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Avaya BCM 2.0 IP Telephony Configuration manual

1. Declines in QoS can be correlated with increasing IP telephony traffic and intranet health reports to locate the sources of delay and error in the network Steps can be taken to strengthen the intranet User feedback Qualitative feedback from users helps confirm if the QoS settings match what end users sense The feedback can come from a Helpdesk facility and can include information such as time of day origination and destination points and a description so the service degradation Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering checklist How do you determine if you have enough available bandwidth on your private network intranet Before installing Enterprise Edge VoIP Gateway test your intranet e Use a terminal on the intranet to test network capability e Use the guidelines to determine if you have enough bandwidth e Choose the codec settings e Determine the dialing plan for VoIP Gateway e Determine if the VoIP Gateway uses a ITU H 323 gatekeeper For further information refer to the Engineering guidelines chapter and the Interoperability chapter PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 56 Engineering checklist Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Installation Before configuration of the Enterprise Edge IP Telephony install the following hardware and software components See the Enterpr
2. About this document This guide provides information about the Enterprise Edge VoIP Gateway This guide is for both guide telecom and datacom engineers who design and install the network The assumption is that the telecom engineer understands how to engineer the Enterprise Edge product portfolio and get system voice and fax traffic statistics The assumption is that the datacom engineer understands the intranet architecture LAN implementation tools for collecting and analyzing data network statistics and data network management systems The terms installer and administrator used in this document refer to either the telecom or datacom engineer This guide contains the following chapters e Engineering guidelines on page 15 e Engineering checklist on page 55 e Installation on page 57 e Configuration on page 61 e Maintenance on page 69 e Interoperability on page 71 System Functions Enterprise Edge VoIP Gateway uses IP telephony to provide least cost routing of voice traffic through a corporate intranet VoIP Gateway provides the following e Basic calls with answer and disconnect supervision e Direct Inward Dial DID and Direct Outward Dial DOD e Calling name and number e VoIP Gateway to M1 ITG capability e ITU H 323v2 compatible gateway e ITU H 323v2 Gatekeeper interoperability e Economical bandwidth use through voice compression e Economical bandwidth use through silence compression e Quality of Service QoS mon
3. Correct design procedures and rules are a must if a corporate network is expected to deliver voice traffic The intranet introduces limits delay delay variation and error at levels that are higher than those delivered by voice networks Delay between a user talking and a listener reduces the performance of conversations while delay variation and packet errors introduce glitches in conversation The connection of the IP gateways to the corporate intranet without preliminary evaluation can result in not acceptable degradation in the voice service A good design of the network begins with an understanding of traffic and the network that carries the traffic There are three preliminary steps where the installer must begin e Determine bandwidth requirements The installer must determine the amount of traffic that the Enterprise Edge product will route through the IP gateway This in turn places a traffic load on the corporate intranet To determine bandwidth requirements refer to the Enterprise Edge VoIP Gateway bandwidth engineering section on page 17 e Determine WAN link resources If there are not enough resources in the corporate intranet to support voice services the problem is normally because of not enough WAN resources To determine WAN resources refer to the Determining WAN link resources section on page 23 e Measure the existing intranet s QoS The installer must determine the quality of voice service the corporate intr
4. Poor QoS levels Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 31 If QoS levels of some or all routes fall short of being Good the installer or administrator needs to evaluate options and costs for upgrading the intranet Further network analysis on page 31 provides guidelines for reducing one way delay The evaluation often requires a link upgrade a topology change or implementation of QoS in the network The installer or administrator can opt for keeping costs down and accept a Fair QoS level for the time for a selected route A calculated trade off in quality requires the installer or administrator monitor the QoS level reset needs with the end users and respond to user feedback Further network analysis This section describes actions possible actions to examine the sources of delay and error in the intranet This section and Implementing QoS in IP networks on page 34 discuss several methods for reducing one way delay and packet loss The key methods are e Reduce link delay e Reducing hop count e Adjust the jitter buffer size e Setting IP telephony QoS objectives Components of delay End to end delay is the result of many delay components The major components of delay are as follows Propagation delay Propagation delay is the result of the mileage and the medium of links moved across Within a country the one way propagation delay over terrestrial lin
5. NetMeeting Enterprise Edge IP Telephony interoperates with any H 323v1 or H 323v2 compliant gateway that conforms to the specifications in the following table Fax calls are only supported between Enterprise Edge Gateways Table 15 Engineering specifications Capacity 1 to 8 ports Voice Compression G 723 1 MP MLQ 6 3 kbit s or ACELP 5 3 kbit s G 729 CS ACELP 8 kbit s supports plain Annex A and Annex B G 711 PCM 64 kbit s u A law Silence compression G 723 1 Annex A G 729 Annex B Echo cancellation 48 ms tail delay In band signalling DTMF TIA 464B Call progress Speech path setup methods H 323v1slowStart media negotiation H 323v2 fastStart End to end DTMF signaling digits 0 9 and fixed duration tones only Table 16 Supported voice payload sizes Codec Receive transmit to M1 ITG Receive transmit to others G 711 Up to 30 ms in 10 ms increments 10 20 or 20 ms 30 ms per ITG s indication G 723 1 30 ms 30 ms G 729 Up to 30 ms in 10 ms increments 10 20 or 20 30 ms per ITG s indication PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 72 Interoperability Asymmetrical media channel negotiation By default the Enterprise Edge IP Telephony gateway supports G 729 G 723 1 G 711 u law and G 711 A law audio media encoding Because NetMeeting does not support the H 323 fastStart call setup method NetMeeting can choose a different me
6. Remote Gateway Table Remote Gateway Table Remote Gateway Remote Gateway IP addresses IP addresses IP3 IP5 IP2 IP5 IPA EE IP7 IP6 IP5 BNE Enterprise Edge 3 A Local Gateway Table Local Gateway IP IP5 Remote Gateway Table Remote Gateway IP addresses IP3 IP3 Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 19 When a user at DN A calls DN C the IP addresses in the Local Gateway and Remote Gateway tables of the each Enterprise Edge systems determine the call routing The Remote Gateway table of the calling party EE 1 contains the IP address where the outgoing voice packets are sent EE 3 The Local Gateway table of EE 1 contains the IP address where EE 3 sends the return voice packets The Local Gateway table of EE 3 contains the IP address which receives the voice packets from EE 1 The Remote Gateway table of EE 3 contains the IP address where it sends the return voice packets There are two methods to set up an IP address Method 1 On a routable internal LAN assign the LAN IP address as the IP address in the Local Gateway table See the Configuration chapter on page 61 for additional information on entering the Local Gateway IP address Method 2 In cases where the LAN is not routable specify a WAN IP address If you assign a WAN link as the local gateway IP address and the primary link
7. 3 IP Monitor G 729 G 711 kbit s kbit s Tx Rx Tx Rx Tx Rx Tx Rx 47 192 5 2 Enabled 4 50 4 50 4 00 4 30 4 75 4 70 4 80 4 90 47 192 5 6 Disabled N A N A N A N A N A N A N A N A Using the QoS Monitor pull down View menu The View menu contains the following option e Refresh The Refresh option updates the display with the most current values Operational Statistics IP Telephony uses the Unified Manager to record information about its operation The administrator accesses the Unified Manager from the Start menu See the software documentation for more information about the events and the viewer Backup and Restore Procedures IP Telephony uses the backup and restore procedures in the Enterprise Edge Programming Operations Guide PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 70 Maintenance Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Interoperability Enterprise Edge IP Telephony is compatible with the ITU T H 323v2 standards IP Voice supports H 323v2 Direct routed gateway capabilities Enterprise Edge IP Telephony 2 0 is compatible with H 323 gatekeepers such as Radvision and the Inca M10 First IP Telephony only interworks with itself and the M1 ITG The M1 ITG is an H 323v2 gateway We expect future releases to support H 323 products from other vendors Interoperability considerations Enterprise Edge IP Telephony interoperates with M1 ITG and Microsoft
8. Enable or disable non linear processing Enable or disable silence compression Enable or disable fallback Enter the voice jitter buffer value PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 58 Installation Figure 9 Configuring the local gateway installation flowchart Enter the fax jitter buffer value Enter the local gateway IP Launch Enterprise Edge Unified Manager Enter VolP Gateway keycode Perform warm reset Choose Enterprise Edge VolP Gateway radio utton Enter codecs Enable or disable echo cancellation Enable or disable silence compression Enable or disable non linear processing NLP Enter voice jitter buffer value Enter fax jitter buffer value Enter local gateway IP Configuring a remote gateway Figure 10 Configuring the remote gateway installation flowchart contains the steps for configuring a remote gateway The installer adds information about each remote gateway Launch Enterprise Edge Unified Manager Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Installation 59 e Select the VoIP Gateway radio button Configure IP address for remote gateway and dialed digits needed to call that gateway Enable or disable QoS Set QoS thresholds e Select Telephony under Resou
9. Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 33 router to router4 instead of having the call routed from router to router2 to router3 to router4 reducing the hop count by two e Router reduction Join co located gateways on one larger and more powerful router Adjust the jitter buffer size The parameters for the voice jitter buffer directly affect the end to end delay and audio quality IP telephony dynamically adjusts the size of the jitter buffer to adjust for jitter in the network The installer or administrator sets the starting point for the jitter buffer Lower the jitter buffer to decrease one way delay and provide less waiting time for late packets Late packets that are lost are replaced with silence Quality decreases with lost packets Increase the size of the jitter buffer to improve quality when jitter is high IP telephony fax calls use a fixed jitter buffer that does not change the hold time over the duration of the call Fax calls are more prone to packet loss In conditions of high jitter increase delay through the use of a deeper jitter buffer To allow for this increase IP telephony provides a separate jitter buffer setting for fax calls Reduce packet errors Packet errors in intranets correlate to congestion in the network Packet errors are high because the packets are dropped if they arrive faster than the link can transmit Identify which links are the most u
10. Guide PO911590 Issue 02 Engineering guidelines 27 The settings in Table 4 indicate the quality of voice service IP telephony periodically calculates the prevailing QoS level per site pair based on the measurement of the following e one way delay e packet loss e codec When the QoS level of any remote gateway is below the fallback threshold all new calls are routed over the standard circuit switched network The computation is taken from the ITU T G 107 Transmission Rating Model Fax is more open to packet loss than the a person s ear quality starts to degrade when packet loss exceeds 10 Fax services must be supported with the gateway operating in either the Excellent or Good QoS level Avoid fax services between site pairs that can guarantee no better than a Fair or Poor QoS level Measuring Intranet QoS Measure the end to end delay and error characteristics of the current state of the intranet These measurements help to set accurate QoS needs when using the corporate intranet to carry voice services Measuring end to end network delay The basic tool used in IP networks to get delay measurements is the Ping program The Ping takes a delay sample by sending an ICMP packet from the host of the Ping program to a destination server and waits for the following Pinging 10 10 10 15 with 32 bytes of data Reply from 10 10 10 15 bytes 32 time 13ms TTL 252 Reply from 10 10 10 15 bytes 32 time 10ms TTL 252 Reply from
11. PnPisbned Codere G72F ka O EST E Cere IroPfwimeo Coleen AFS F t ras z r PreierecdCadecs aaa re mPa Goiara AFi Poe b inui ih FPreieerd Cadere fe r bai P ar On Eimi C rcsldion ts ad fiona Croceseing Emshled aie r Sisti Ceragransion babbi F E Frinackig Croate Eaohked bi P Woke er Duta TT gt i b p T an Ser Duta ET T T a hime s Larai Gara F foras 5 Perform the operation The menus for all of the possible selection from the IP Telephony web browser are the same The menu headers are e Configuration e View e Help Configuration contains options that allow the administrator to modify the table and the highlighted entries The options available in this pull down menu depend on the table selected for modification Local Gateway Configuration These settings apply to all calls no matter the IP destination Settings include the Preferred order of codecs echo cancellation state silence compression state and jitter buffer settings Codecs reduce bandwidth use by reducing the amount of information sent between gateways The G 7XX series of codecs are standards defined by the International Telecommunications Union ITU Different codecs have different QoS and compression properties The compression properties can affect heard audio quality while saving bandwidth The installer or administrator configures the supported codecs Refer to the Codec types section on page 37 for more information about sele
12. Table 5 you can calculate the load of voice traffic per link Table 5 Site pairs and routes Site pair Intranet route Santa Clara Richardson R1 R4 R5 R6 Santa Clara Ottawa R1 R2 Santa Clara Tokyo R1 R4 R5 R7 Richardson Ottawa R2 R3 R5 R6 Enterprise Edge 2 0 IP Telephony Configuration Guide P0911590 Issue 02 Engineering guidelines 29 Table 6 Computed load of voice traffic per link Links Traffic from R1 R4 Santa Clara Richardson R4 R5 Santa Clara Richardson Santa Clara Tokyo R5 R6 Santa Clara Richardson Richardson Ottawa R1 R2 Santa Clara Ottawa R1 R4 Santa Clara Tokyo R5 R7 Santa Clara Tokyo R2 R3 Richardson Ottawa R3 R5 Richardson Ottawa Adjusting ping measurements The Ping Statistics are based on round trip measurements while the QoS metrics in the Transmission Rating model are one way To make the comparison compatible the delay and packet error Ping statistics are halved Adjustment for processing The Ping measurements are taken from Ping host to Ping host The Transmission Rating QoS metrics are from end user to end user and include components outside the intranet The Ping statistics for delay needs additional adjustments by adding 140 ms to explain the processing and jitter buffer delay of the gateways No adjustment are required for error rates If the intranet measurement barely meets the round trip QoS objectives the one way QoS is not met in one of the directions of flow Th
13. WAN IP bandwidth usage per Enterprise Edge Gateway loaded to 36 CCS per port per hour without silence compression on page 21 for no silence compression each port generates 80 kbit s when engaged in a call If all four ports are in use then the additional load is 320 kbit s Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 23 Determining WAN link resources For most installations IP telephony traffic is routed over WAN links within the intranet WAN links are the most expensive recurring expenses in the network and they often are the source of capacity problems in the network Different from LAN bandwidth which is almost free and easily installed WAN links especially inter LATA and international links require time to receive financial approval provision and upgrade For these reasons it is important to determine the state of WAN links in the intranet before installing the IP telephony Each voice conversation G 729 Annex B codec 20 ms payload uses 12 kbit s of bandwidth for each link that moves across in the intranet a DSO can support below 5 simultaneous telephone conversations Link utilization The starting point of this evaluation is to get a current topology map and link utilization report of the intranet A visual inspection of the topology map indicates which WAN links are expected to deliver IP telephony traffic Also use the Traceroute tool see Measuring Intranet QoS
14. a busy signal from the gateway Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Glossary Backbone Bandwidth Bridge CBQ CD ROM CDP CO Codec Communications Protocol CPU Data Communications DID DN DOD DSP E amp M Enbloc Full duplex transmission G 711 G 729 G 723 1 GUI H 323 Hub IP ITG PO91 1590 Issue 02 A network s major transmission path handling high volume high density traffic A measure of information carrying capacity available for a transmission medium shown in bits per second The greater the bandwidth the more information sent in a given amount of time LAN equipment providing interconnection between two networks using the same addressing structure A bridge filters out packets that remain on one LAN and forwards packets for other LANs Class Based Queuing Compact Disk Read Only Memory Coordinated Dialing Plan Central Office Equipment or circuits that digitally code and decode voice signals A set of agreed upon communications formats and procedures between devices on a data communication network Central Processing Unit Processes and equipment used to transport signals from a data processing device at one location to a data processing device at another location Direct Inward Dialing Directory Number Direct Outward Dialing Digital Signal Processor E amp M is a type of analog trunk that detects line disconnect All dialed digi
15. address resolution In this mode the gatekeeper handles all call control signaling The remote gateway table is not used Dialing plan support Dialing plan configuration allows the customer to set up the routing tables to route calls to appropriate destinations based on the dialed digits Routing codes and the destination code table allow the core telephony services on the Enterprise Edge to direct the use and time of use of trunking facilities for calls Routing codes are associated with line pools You can assign more than one routing code to each destination code depending on factors such as Least Cost Routing Enterprise Edge has two main areas of configuration the destination codes in the core telephony services and the destination digits in the remote gateway configuration table The destination digits allow VoIP Gateway to route calls to the appropriate intranet destination based on the leading dialed digits The destination code tables route calls to the appropriate trunks based on the leading dialed digits See the Configuration chapter on page 61 for details on configuring destination digits and destination codes The dialing plans for all VoIP Gateways connected to the corporate intranet require planning to allow calls between gateways as required For more information about Dialing plan support see Dialing plan section on page 43 PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 10 Overview Netwo
16. amount of bandwidth The G 729 and G 723 1 codecs use less bandwidth but reduce audio quality The installer or administrator determines the best option for the user and the available bandwidth on the intranet For example if the WAN link cannot support multiple 64 kbit s calls G 711 must not be configured as a supported codec Enterprise Edge IP Telephony supports and recommends the following order for codec selection e G 729 e G 723 1 6 3 kbit s or 5 3 kbit s e G 711 The G 729 codec provides the best balance of quality audio plus bandwidth savings G 729 The G 729 codec is the default and Preferred codec for IP telephony The G 729 codec provides near toll quality with a low delay This codec uses compression to 8 kbit s Enterprise Edge VoIP Gateway supports G 729 with silence compression per Annex B G 723 1 The G 723 1 codec uses the smallest amount of bandwidth This codec uses the greatest compression 5 3 kbit s or 6 3 kbit s PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 38 Engineering guidelines The G 723 1 codec uses a different compression method than the G 729 codec The G 723 1 method uses more DSP resources Each MSPEC supports one G 723 1 call A G 711 call can run in the same MSPEC as a G 723 1 call See the Enterprise Edge Programming Operations Guide for additional information If the G 723 1 codec is the only possible codec for a call a trunk can not be available for the cal
17. cause not needed delay Some routes are better than other routes The Traceroute program allows the user to detect routing anomalies and to correct these problems Possible high delay differences causes are e routing instability e wrong load splitting e frequent changes to the intranet e asymmetrical routing Implementing QoS in IP networks Corporate intranets developed to support data services Accordingly normal intranets are designed to support a set of QoS objectives dictated by these data services When an intranet takes on a real time service users of that service set additional QoS objectives in the intranet some of the targets can be less controlled compared with the targets set by current services while other targets are more controlled For intranets not exposed to real time services in the past but now need to deliver IP telephony traffic QoS objectives for delay can set an additional design restriction on the intranet One method is to subject all intranet traffic to additional QoS restrictions and design the network to the strictest QoS objectives A exact plan to the design improves the quality of data services although most applications cannot identify a reduction of say 50 ms in delay Improvement of the network results in one correctly planned for voice but over planned for data services Another plan is to consider using QoS mechanisms in the intranet the purpose of which is to provide a more cost effective
18. compression full duplex bandwidth use is reduced by the same amount releasing bandwidth for other voice fax or data communications Figure 5 Silence compression shows how silence compression allows two conversations to fit in the bandwidth otherwise used by one This 50 bandwidth reduction develops over a 20 30 second period as the conversation switches from one direction to another Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 39 Figure 5 Silence compression Two Conversations Without Silence Suppression i Hello Fred this is Susan gt Hi Peter this is Carol PEN S i hi l i Between the talk listen silence around 50 With silence suppression two conversations can share the bandwidth normally used by one conversation hus doubling transmission efficiency Data and LAN traffic can also share bandwidth and ride along on the silence of a speech conversation To provide a more natural sound comfort noise is added at the destination gateway during the silent periods to calls where silence compression is active Silence compression can cause a sensed degradation in audio quality Silence compression can be disabled With silence compression disabled the bandwidth use of the LAN WAN approximately multiplies by two If an IP gateway acts as a tandem switch in a network where circuit switched trunk facilities have a large amount of lo
19. indicate the minimum QoS required for traffic to route over the IP Telephony to or from the defined destination Valid thresholds are between 0 and 5 00 Modifying the Remote Gateway Configuration table The pull down menu Table contains the following options e Add Entry e Delete Entry e Modify Entry The Add Entry option allows the administrator to add a new entry to the Remote Gateway Configuration table If the administrator highlights an entry on the existing table and selects the Add Entry option a dialog box appears Insert the new entry at the end of the table Enable or disable the QoS monitor for each entry with the radio button The Delete Entry option allows the administrator to delete an entry from the Remote Gateway Configuration table If the administrator highlights an entry on the existing table and selects the Delete Entry option a dialog box appears The dialog box asks the administrator to confirm either or not to delete an entry The Delete Entry option is not available when there is no entry on the existing table highlighted Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Configuration 67 The Modify Entry option allows the administrator to change the information in an entry The administrator highlights an entry on the existing table and selects the Modify Entry option A dialog box allows changes to entry information A default button restores the information to the settings shown in the
20. public numbers when the numbers are dialed by Meridian M1 users or by Enterprise Edge Solution users Enterprise Edge and a Gatekeeper Enterprise Edge 2 0 IP Telephony Configuration Guide Enterprise Edge supports the use of an ITU H 323 gatekeeper A gatekeeper is a third party software installed on a server to centralize IP address configuration information Each port on the network receives an aliasname Instead of having remote gateway tables on each Enterprise Edge system the gatekeeper contains the remote gateway table The aliasname is linked to an IP address by the gatekeeper If an IP address changes only the gatekeeper need updating as the aliasname remains the same PO91 1590 Issue 02 Engineering guidelines 47 See the gatekeeper s software documentation for information about changing IP addresses Figure 7 Enterprise Edge systems with a gatekeeper Enterprise Edge Enterprise Edge Enterprise Edge Santa Clara DN 4xx Ottawa DN 5xx Raleigh DN 6xx IP 10 10 10 11 IP 10 10 10 12 IP 10 10 10 13 Gatekeeper Gatekeeper IP 10 10 10 10 d Meridian M1 Tokyo DN 3xx IP 10 10 10 18 um A user in Tokyo at DN300 dials DN400 The least cost routing is over the internet The Tokyo Meridian M1 connects to the destination IP address in its remote gateway table for DN4xx That address is the gatekeeper The gatekeeper identifies DNA4xx as a Santa Clara DN The gatekeeper performs address resolution from the Santa
21. solution to engineering the intranet for non homogenous traffic types Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 35 Traffic mix This section describes what QoS mechanisms work with the IP telephony and with what new intranet wide results if done Before putting into operation QoS mechanisms in the network determine the traffic mix of the network QoS mechanisms depend on the process and ability to determine traffic by class so as to provide different services With an intranet designed only to deliver IP telephony traffic where all traffic flows are equal priority there is no need to consider QoS mechanisms This network can have one class of traffic In most corporate environments the intranet is supporting data and other services When planning to provide voice services over the intranet the installer determine the following e Are there existing QoS mechanisms What kind IP telephony traffic must take advantage of established mechanisms if possible e What is the traffic mix If the IP telephony traffic is small compared to data traffic on the intranet then IP QoS mechanisms can do If IP telephony traffic is a large amount data services can be hit if those mechanisms are biased toward IP telephony traffic TCP traffic behavior Most of corporate intranet traffic is TCP based Different from UDP that has no flow control TCP uses a sliding window flow control mechan
22. 10 10 10 15 bytes 32 time 6ms TTL 252 Reply from 10 10 10 15 bytes 32 time 5ms TTL 252 The round trip time rtt is indicated by the time field So that the delay sample results match what the gateway experiences the Ping host must be on a correctly working LAN segment on the intranet The option of destination host is as important following the same guidelines for the source host Set the size of the Ping probe packets to 60 bytes to approximate the size of probe packets sent by IP telephony and determine if new calls need to fall back on the circuit switched voice facilities Notice from the Ping output the difference of rtt The repeated sampling of rtt allows you to receive a delay characteristic of the intranet To get a delay distribution include the Ping tool in a script which controls the frequency of the Ping probes which timestamps and stores the samples in a raw data file PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 28 Engineering guidelines The file can be analyzed by the administrator using spreadsheet and other statistics packages The installer can check if the intranet s network management software has any delay measurement modules which can cause a delay distribution measurement for specific site pairs Delay characteristics vary depending on the site pair and the time of day The evaluation of the intranet includes taking delay measurements for each site pair If there are important chan
23. Clara aliasname to the IP address 10 10 10 11 The call connects to the Santa Clara Enterprise Edge routed to DN400 Toll bypass with VoIP telephony This example shows a private network with one Enterprise Edge system in Toronto and one system in Ottawa connected over IP trunks through a corporate IP network Each system has a PRI trunk to the Central Office and IP trunks to the other system Calls arrive from Toronto to the Ottawa and the Ottawa public network over IP trunks with fallback to the PRI trunks when IP trunks are overflowed This configuration allows for reduced costs using the corporate IP network when possible bypassing toll charges and other charges when using the public network Note When a call gets rerouted over the PSTN as a result of congestion the user can see a prompt Expensive route The warning indicates that toll charges can apply to this call PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 48 Engineering guidelines Users at both locations access the public network by dialing 9 followed by the public number For example a user in Toronto can dial 9 555 1212 for a local call or 9 1 613 555 1212 for a long distance call to Ottawa Local calls can go to the Central Office over PRI trunks Long distance calls to Ottawa can go over IP trunks the Ottawa system can tandem these calls to the local Central Office over PRI trunks Private network cal
24. DiffServ or legacy network the router manages the WAN link to make sure Premium VoIP packets have high priority in both directions when crossing a Slow WAN link Implementing the network LAN engineering To minimize the number of router hops between the systems connect the gateways to the intranet ensuring there is enough bandwidth on the WAN links shorter routes To prevent division of the constant bit rate IP telephony traffic from bursty LAN traffic and make easier the end to end Quality of Service engineering for packet delay jitter and packet loss place the gateway and the LAN router near the WAN backbone With supported codecs through the IP telephony network set to G 729 G 723 1 6 3 kbit s G 723 1 5 3 kbit s and G 711 ensure that up to 8 ports share the same 10BaseT LAN collision domain For the deployment of a mixed codec IP telephony refer to Table 1 LAN and WAN IP bandwidth usage per Enterprise Edge Gateway loaded to 36 CCS per port per hour with silence compression on page 20 to estimate the amount of LAN bandwidth used Setting the Quality of Service threshold for fallback routing Configure the Quality of Service thresholds for fallback routing in the IP telephony Manager application Configure a threshold for both the receive fall back threshold Rx and the transmit fall back threshold Tx The available thresholds are Excellent Good Fair and Poor Table 8 Sample Mean Opinion Score to qualitative sca
25. NORTEL NETWORKS Enterprise Edge 2 0 IP Telephony Configuration Guide 1 800 4 NORTEL www nortelnetworks com 2000 Nortel Networks P0911590 Issue 02 Contents 3 Contents Chapter 1 Chapter 2 Overview 7 About this document 8 System Functions 8 Dialing plan support 9 Network Quality of Service 10 Network Monitoring 10 Quality of service parameters 10 Fallback to circuit switched voice facilities 11 Network Performance Utilities 12 Codecs 12 Silence compression 13 Echo cancellation 13 Jitter buffer 14 Fax calls 14 Alarm Notification 14 Engineering guidelines 15 Introduction 15 Enterprise Edge IP telephony 15 Overview 15 Enterprise Edge VoIP Gateway bandwidth engineering 17 Multiple network interfaces 18 Method 1 19 Method 2 19 LAN engineering 20 Silence compression 20 WAN engineering 22 Determining WAN link resources 23 Link utilization 23 Determining network loading caused by IP telephony traffic 24 Other intranet resource considerations 25 Setting QoS 26 Measuring Intranet QoS 27 Measuring end to end network delay 27 Measuring end to end packet loss 28 Recording routes 28 Adjusting ping measurements 29 Measurement procedure 29 Other measurement considerations 30 Further network analysis 31 PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 4 Contents Chapter 3 Chapter 4 Chapter 5 Chapter 6 Components of delay 31 Reduce link delay 32 Reducing hop coun
26. Rx and the transmit fallback threshold Tx set on a per site pair basis The Setting QoS section on page 26 and Measuring Intranet QoS section on page 27 describe the process to determine the appropriate QoS level for operating the voice network Site pairs can have very different QoS measurements either because some traffic flows are local while other traffic flows are inter continental The installer or administrator can consider setting a higher QoS level for the local sites compared to the international sites keeping cost of international WAN links down Normally set the fallback threshold in both directions to the same QoS level In site pairs where the applications are so that one direction of flow is more important the installer or administrator can set up asymmetric QoS levels Enterprise Edge uses routes to determine which outgoing facilities to use A given destination code can have an alternate route configured The alternate route is used if the main route is not available to process calls For example calls use the alternate route if all lines in the line pool are busy See the Enterprise Edge Programming Operations Guide for more information IP trunks can use this capability Unique to IP trunks is the ability to take advantage of the QoS monitoring capability that is part of IP telephony If fallback functionality enabled any QoS damage in the intranet which causes any monitored remote gateway to exceed its threshold resu
27. The installer or administrator enters a numeric value between 20 and 200 The recommended maximum is 100 The Fax Jitter Buffer field displays the maximum size of the fax Jitter buffer The installer or administrator enters a numeric value between 20 and 500 The recommended value is 250 The Local Gateway IP displays the IP address used by the local gateway and the remote gateways of other VoIP systems See the Multiple network interfaces section page 18 for more information The Gatekeeper IP displays the IP address of the gatekeeper Set the field to none or enter the IP address of the gatekeeper When the installer or administrator enters an IP address the gateway registers with the gatekeeper at this address on port 1719 Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Configuration 65 e The Call Signaling field displays the selected IP address conversion process and the installer or administrator enters one of the following options Direct gateway resolves IP addresses locally using the remote gateway table GatekeeperRouted gateway sends call signaling messages to the gatekeeper to use the gatekeeper s remote gateway table to resolve the IP address GatekeeperResolved not supported e The Aliasname field contains a text string that identifies the Enterprise Edge gateway to the gatekeeper The gatekeeper matches dialed DNs with aliasnames as part of the dialing plan for the network M
28. and hop count Each site pair takes different routes over the intranet The route taken determines the number and type of delay components that add to end to end delay Sound routing in the network depends on correct network design Reduce link delay In this and the next few sections the guidelines examines different ways of reducing one way delay and packet loss in the network The time taken for a voice packet to queue on the transmission buffer of a link until received at the next hop router is the link delay Methods to reduce link delays are e Upgrade link capacity to reduce the serialization delay of the packet but more so reduces the utilization of the link reducing the queueing delay Before upgrading a link the installer or administrator must check both routers connected to the link for the upgrade and ensure correct router configuration guidelines e Change the link from satellite to terrestrial to reduce the link delay by on the order of 100 to 300 ms e Put into operation a priority queueing rule e Identify the links with the highest use and the slowest traffic Estimate the link delay of these links using Traceroute Contact your service provider for help with improving your QoS Reducing hop count To reduce end to end delay can reduce hop count especially on hops that move across WAN links Some of the ways to reduce hop count include e Improve meshing Add links to help improve meshing adding a link from
29. anet can deliver The Measuring Intranet QoS section on page 27 describes how to measure the delay and error characteristics of an intranet After the examination phase the installer designs and installs the IP telephony network This design not only includes the IP telephony but can also include making design changes to the intranet e The Further network analysis section on page 31 provide guidelines for modifying the intranet e The Implementing the network section on page 36 provides guidelines for integrating the IP gateway into the corporate LAN Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 17 Figure 1 IP Telephony network engineering process shows when the design and planning decisions that must occur Figure 1 IP Telephony network engineering process Determine bandwidth requirements Assess WAN resources i Capaci available Le Measure intranet QoS No Within Qos expectations Vv Implement IP Further network telephony analysis or design AA v Network Implement monitoring and network changes data collection Yes Enterprise Edge VolP Gateway bandwidth engineering Traffic controls the network design and the design process starts with the process of getting an IP telephony bandwidth forecast The bandwidth forecast drives
30. ange of the affected values This gives time for implementation processes to follow through The planning thresholds can be set 5 to 15 below the QoS objectives depending on the implementation lag time Intranet QoS monitoring To monitor the one way delay and packet loss statistics install delay and route monitoring tools such as Ping and Traceroute on the LAN of each gateway site See Measuring Intranet QoS on page 27 for guidelines describing the implementation of Ping hosts the use of scripting and information about other delay monitoring tools Delay monitoring tool runs continuously adding probe packets to each gateway about every minute The load generated by the probe packets is not considered a large amount At the end of the month the hours with the highest one way delay are indicated within those hours the packet loss and standard deviation statistics can be calculated PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 54 Engineering guidelines At the end of the month the administrator can analyze each gateway s QoS based on information described in Table 12 Gateway QoS objectives Table 12 Gateway QoS objectives One way delay Packet loss Peak hour Carried Mean o ms Mean o ms traffic traffic QoS Site pair Last Current Last Current End Start End Start Piective period period period period Santa Clara Richardson Santa Clara Ottawa etc
31. bits per second Millions of bits per second Device that converts serial data from a transmitting terminal to an analog device for transmission over a telephone channel Another modem converts the signal to serial digital data for the receiving terminal Mean Opinion Score Media Services Card Random electrical signals generated by circuit components or by natural interruptions that damage communications Operations Administration and Maintenance Group of bits transmitted as a complete package on a packet switched network A telecommunications network based on packet switching technology A link is busy for the duration of the packets Processing Expansion Card Public Switched Telephone Network Quality of Service Real Time Protocol Transmission Control Protocol Internet Protocol Protocol for routing and reliable message delivery Device capable of sending or receiving data over a data communications channel Indicator of data handling ability Measures data processed as output by a computer communications device link or system Logical or physical arrangement of nodes or stations Method of reducing bandwidth by reducing the number of bits required to transmit voice Voice over Internet Protocol Wide Area Network Weighted Random Early Detection PO91 1590 Issue 02 Index A alarms 69 Aliasname field 65 C Call Signaling 65 changes to the intranet 34 Codecs 12 Core telephony services configurati
32. can fail For an example of fallback programming refer to the section Toll bypass with VoIP telephony on page 47 Note Enterprise Edge IP telephony requires a keycode After entering the keycode for Enterprise Edge IP Telephony perform a warm reset by following the procedure in the Maintenance chapter of the Enterprise Edge Programming Operations Guide In Table 9 Private and public network routing West End to East End office private network routing information appears in gray Public network routing information appears in white The Call Managers examine the dialed digits and route the call to the matching IP address Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 45 Table 9 Private and public network routing West End to East End office Heading Parameter Setting West End office Trunk Line Data Line 241 Target line Received 2221 Line Access Set 2221 L241 Ring only Line pool access Line pool A To Head office M1 Service Routing Service Route 001 Use Pool A External leave blank DN type Private Destination Code 4 Normal route 001 Absorb None To East End Service Routing Service Destination Code 6 Normal route 001 Absorb None To Public Network Service Routing Service Route 002 Use Pool A External leave blank DN type Public Destination Code 9 No
33. compression Fax calls require 64 kbit s bandwidth Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 21 For more information about silence compression and fax calls see the Silence compression on page 38 and the Fax calls section on page 41 Table 2 LAN and WAN IP bandwidth usage per Enterprise Edge Gateway loaded to 36 CCS per port per hour without silence compression Codec Type Packet Voice fax IP packet Ethernet Bandwidth Bandwidth duration payload in bytes frame usage usage on in ms in bytes bytes on LAN WAN payload in kbit s in kbit s G 711 10 80 240 292 233 6 967 64 kbit s 36 160 400 452 180 8 80 30 240 560 612 163 2 74 67 G 729 10 10 100 152 121 6 40 07 8 kbit s 20 20 120 172 68 8 24 0 30 30 140 192 512 18 67 G 723 1 5 3 30 20 120 172 45 8 16 0 kbit s G723 1 30 24 128 180 48 0 17 0 6 3 kbit s Note 1 LAN data rate is the effective Ethernet bandwidth use Note 2 LAN kbit s Ethernet frame bytes 8 1000 Frame duration in ms Note 3 50 voice traffic reduction due to silence compression no compression for fax Note 4 Overhead of RTP UDP IP packet over voice packet is 40 bytes overhead of Ethernet frame over IP packet is 26 bytes Note 5 Keep Ethernet bandwidth to support to support an Interframe gap of at least 12 bytes per frame This gap is not included in the above bandwidth calculati
34. cting a codec PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 64 Configuration Table 13 Sample Local Gateway Configuration Parameters Settings Supported Codecs G 729 G 723 1 6 3 kbit s or 5 3 kbit s G 711 Echo Cancellation Enabled Non linear processing Enabled Silence Compression Enabled Fallback to Circuit switched Enabled Voice Jitter Buffer 100 Fax Jitter Buffer 250 Local Gateway IP Gatekeeper IP address 00 00 00 00 Call signaling Direct GatekeeperRouted GatekeeperResolved Aliasname Alias assigned to the local gateway The Local Gateway Configuration menu contains the following are fields The Supported Codecs field indicates the supported codecs A pull down menu allows the installer or administrator to modify the list The Echo Cancellation field indicates Echo cancellation A pull down menu allows the installer or administrator to select enabled or disabled The Non linear processing field indicates Non linear processing A pull down menu allows the installer or administrator to select enabled or disabled The Silence Compression field indicates Silence compression A pull down menu allows the installer or administrator to select enabled or disabled The Fallback to Circuit switched field has a pull down menu that allows the installer or administrator to select enabled or disabled The Voice Jitter Buffer field displays the maximum size of the voice Jitter buffer
35. d continues with the call If both ends cannot agree on a codec type the call fails Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Overview 13 All gateways in the intranet must use the same codec types Each gateway is configured with available codecs with the selected order of use The codecs configuration must reflect available bandwidth on the network Codec options are between quality compared to bandwidth The supported codec types are configured in the Modifying the Local Gateway Configuration table section on page 65 The G 711 codec provides the best audio quality but uses the greatest amount of bandwidth The G 729 and G 723 1 codecs use less bandwidth but reduce audio quality The installer or administrator determines the best option for the user and the available bandwidth on the intranet For example if the WAN link cannot support multiple 64 kbit s calls G 711 must not be configured as a supported codec Enterprise Edge supports and recommends the following order for codec selection e G 729 e G 723 1 6 3 kbit s or 5 3 kbit s e G 711 The G 729 codec provides the best balance of quality audio plus bandwidth savings For more information about codecs see the Codec types section on page 37 Silence compression G 723 1 and G 729 Annex B support Silence compression A key to VoIP Gateway s success in business applications is reducing WAN bandwidth use Beyond speech compression the be
36. d time over the duration of the call The installer or administrator configures the maximum hold time VoIP Gateway fax calls use a fixed jitter buffer that does not change the hold time over the duration of the call Fax calls are more prone to packet loss In conditions of high jitter increased delay through the use of a deeper jitter buffer is preferred To adapt VoIP Gateway provides a separate jitter buffer setting for fax calls The voice jitter buffer parameters directly affect the end to end delay and audio quality IP telephony dynamically adjusts the size of the jitter buffer to adjust for jitter in the network The installer or administrator sets the starting point for the jitter buffer Fax calls The Enterprise Edge gateways support T 30 Group 3 fax calls Fax calls automatically use the G 711 codec and require the associated bandwidth As the gateway does not know in advance that a call carries a fax transmission it first establishes a voice channel The voice channel can use G 729 or G 723 1 audio compression When detecting the answering fax machine s CED tone the terminating gateway performs the following operations e Starts the procedure to revert the speech path to a G 711 64 Kbit s clear channel e Disables the adaptive jitter buffer feature e Sets the hold time for the jitter buffer to the value indicated in the Local Gateway settings to improve late IP packet tolerance The answering fax machine must pro
37. determine network strength by conducting link and node failure analysis By simulating failures re loading network and re computed routes the modules indicate where the network can be out of capacity during failures Not enough link capacity If there is not enough link capacity consider one or more of the following options e Use the G 723 1 codec Compared to the default G 729 codec with 20 ms payload the G 723 1 codecs use 29 to 33 less bandwidth e Upgrade the link s bandwidth Other intranet resource considerations Bottlenecks caused by non WAN resources do not occur often For a more complete evaluation consider the impact of incremental IP telephony traffic on routers and LAN resources in the intranet The IP telephony traffic moves across LAN segments that are saturated or routers whose CPU utilization is high PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 26 Engineering guidelines Setting QoS The users of corporate voice and data services expect these services to meet a level of quality of service QoS which in turn affect network design The purpose is to design and allocate enough resources in the network to meet user needs QoS metrics or parameters help in meeting the needs required by the user of the service There are two interfaces that the installer needs to consider e IP telephony interfaces with the end users voice services made available need to meet user QoS objectives
38. determining voice quality delay is like the average jitter is like the standard deviation For more information about jitter buffer see the Jitter buffer section on page 40 Fax calls The Enterprise Edge gateways support T 30 Group 3 fax calls Fax calls automatically use the G 711 codec and require the associated bandwidth For more information about fax calls see the Fax calls section on page 41 Alarm Notification Enterprise Edge uses the Unified Manager to record information about its working status See the Maintenance chapter on page 69 for additional information Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines The engineering guidelines address the design of an IP trunk network for Enterprise Edge VoIP Gateway The network contains the following e Enterprise Edge VoIP gateways e Gateways attached to LANs e Corporate intranet connecting the LANs The guidelines assume that an installed corporate intranet connects the sites of the IP gateways Introduction IP telephony compresses PCM voice and routes the packetized data over an intranet to provide virtual analog TIE trunks between gateways As voice traffic flows through at low marginal cost over existing private IP network facilities with available bandwidth on the private Wide Area Network WAN backbone communication costs are lower This chapter provides guidelines for correctly designing a network of IP gatewa
39. dia type for its receive and transmit channels Enterprise Edge IP Telephony gateway does not support calls with different media types for the receive and transmit channels and immediately hangs up a call taken with asymmetric audio channels The party on the Enterprise Edge switch hears a treatment from the switch normally a reorder tone The party on the NetMeeting client losses connection To solve this problem in NetMeeting under the Tools Options Audio Advanced check Manually configure compression settings and ensure that the media types are in the same order as shown in the Enterprise Edge local gateway configuration table Table 17 lists the names used by the Enterprise Edge local gateway table and the matching names in NetMeeting Table 17 Name comparison Enterprise Edge local gateway table MS NetMeeting G 723 1 6 3 Kbit s MS G 723 6400 bit s G 723 1 5 3 Kbit s MS G 723 5333 bit s G 711 p law CCITT p law G 711 A law CCITT A law No feedback busy station The Enterprise Edge VoIP gateway considers the voice over IP connection as the equivalent of an MF trunk The Enterprise Edge VoIP gateway provides call progress tones in band to the user On calling a busy station through the gateway the gateway plays a busy tone to the user As NetMeeting does not support fastStart no speech path is opened to the user before the call connects In this distinct design the user on the NetMeeting station does not hear
40. duce its CED tone within 15 s of connection The terminating gateway turns off CED tone detection after 15 s to prevent false tone detection during a voice call This method sets the following restrictions PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 42 Engineering guidelines e Interoperability with other IP gateways A terminating gateway must support CED fax tone detection and start the procedure as described in previous paragraphs An originating gateway must support the H 323 Request Mode procedure but does not need to detect fax tones The originating gateway must additionally be capable of supporting the large G 711 packets used for fax transmission e In order for the gateways to revert to a G 711 clear channel the terminating fax machine must issue a CED tone when answering the call Manually started fax transmissions where the user at the terminating end first talks with the originating user before setting the terminating fax to receive the document are not supported e Fax machines allow a maximum round trip delay of 1200 ms Media processing in the two gateways introduces a round trip delay of approximately 300 ms and the delay caused by the jitter buffer If a 250 ms jitter buffer is used IP latency must never exceed 1200 300 2 x 250 400 ms round trip delay or approximately 200 ms one way Fallback threshold Fallback threshold has two parameters the receive fallback threshold
41. e Edge VolP Gateway display ju HSE ES GF Enbwitcedg 408205 sl er The interface allows the administrator to modify the following areas e Local gateway e Remote gateways PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 62 Configuration User Interface Overview Use the following steps to modify an entry 1 Select the item click on the radio button to open the Enterprise Edge IP Gateway menu Figure 13 Unified Manager selection list ME RTEL HETWORKS Bivsp Compeheneve a Enion ia ECE CE Stem D e Arimea D Saracen Local Grien B Rmo Gak iji Seva ES Management 2 Select an item from the Unified Manager menu The right hand side of the manager displays a pull down menu bar and the current information for the selected item Figure 14 Unified Manager with pull down menu and sample information Nene TERPRIS SE HETWORKS ENTERPRIS Eten Congres es liste CRC Legre ran Add Enp OF Enem Ein Dabber E rary Cetin Oe Mis Team Tihai soe Thai Gate Lau Deni i nie E ur E der o io T P Femois Galea ge i T e 3 Highlight an entry to modify it 4 Use the pull down menu bar to select the operation A dialog box opens Enterprise Edge 2 0 IP Telephony Configuration Guide P0911590 Issue 02 Configuration 63 Figure 15 Sample dialog box sample display new screen cap to be provided Comprene Lii Gare tried Cee
42. e Enterprise Edge Programming Operations Guide Core telephony services configuration IP telephony ports represent private IP trunking facilities by the core telephony services The core telephony services require configuration to enable calls to use IP telephony ports as IP trunks The user indicates the required destination by dialing digits The dialing plan determines the digits required to reach each destination The user dials a destination code configured to select a fixed route which in turn selects a line pool A line pool is a group of trunk facilities This configuration process allows the administrator to determine the use of facilities IP trunks are one of many possible facilities that used to optimize communication functionality With this information Direct Inward Dial DID and Direct Outward Dial DOD services are provided IP trunks are a point to multipoint facility different from analog TIE trunks which are a point to point facility When IP trunk is selected through the dialed digits its endpoint is not determined The remote gateway configuration on IP telephony provides the final address resolution To ensure functionality the installer and administrator need to ensure that the core telephony services configuration such as planning the destination codes with the IP telephony remote gateway configuration If the leading dialed digits which are passed to the IP gateway during call setup do not match the IP telepho
43. e The gateways interface with the intranet the service provided by the intranet is best effort delivery of IP packets not guaranteed QoS for real time voice transport IP telephony translates the QoS objectives set by the end users into IP adjusted QoS objectives The guidelines call these objectives the intranet QoS objectives Figure 4 Relationship between users and services Delay variation Enterprise Edge IP telephony parameters Fallback threshold Silence compression Codec Echo cancellation Non linear programming Enterprise Edge VolP Corporate intranet lo Deliver voice Deliver IP fax service service I User oriented QoS Network QoS metrics Roundtrip conversation delay One way delay Clipping and dropout Packet loss echo The IP gateway can monitor the intranet s QoS In this mode two parameters the receive fallback threshold and the transmit fallback threshold control the minimum QoS level of the intranet Fallback thresholds are set on pair per site basis The QoS level is aligned for user QoS metrics that allow to set an acceptable Mean Opinion Score MOS level The administrator can adjust the fallback thresholds to provide acceptable service to the users Table 4 Quality of voice service MOS Range Qualitative Scale 4 86 to 5 00 Excellent 3 00 to 4 85 Good 2 00 to 2 99 Fair 1 00 to 1 99 Poor Enterprise Edge 2 0 IP Telephony Configuration
44. e capability unique to IP trunks takes advantage of the QoS monitoring that is part of IP telephony If fallback to conventional circuit switched facilities is enabled in the Local Gateway Configuration calls route to the circuit switched facilities if the QoS is below the acceptable threshold The installer configures fallback as follows 1 Launch Unified Manager and select the IP Telephony radio button 2 Enable fallback in the Local Gateway Configuration 3 Enable QoS monitoring for the required destination in the Remote Gateway Configuration 4 Set the Tx and Rx thresholds MOS numbers for the required QoS 5 Configure all alternate routes for the IP trunks Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Maintenance Quality of Service Monitor The Quality of Service Monitor is a software that monitors the quality of the IP channels every 15 seconds The QoS Monitor determines the quality of the intranet based on threshold tables for each codec If the QoS Monitor determines that a threshold has been exceeded the QoS Monitor if enabled will trigger fallback to conventional circuit switched systems Quality of Service Status The QoS Status displays the current network quality described as a Mean Opinion Score MOS for each IP destination A pull down menu allows the administrator to view the MOS mapping A sample QoS Monitor follows QoS G 723 1 6 3 G 723 1 5
45. ed by the public number For example a user in the west end branch can dial 9 555 1212 for a local call or 9 1 613 555 1212 for a long distance call These public calls routes to the Meridian 1 by the Enterprise Edge s routing table Routing tables at the Meridian 1 select an appropriate public facility for the call PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 44 Engineering guidelines Private network calls are done by dialing a 4 digit private network DN For example if a user in the west end branch calls a user in the east end branch within the private network they dial 6221 Figure 6 Enterprise Edge and M1 networking overview Network 2221 Network 6221 Received 2221 Received 6221 Internal 2221 Internal 6221 IP IP IP ise Ed Enterprise Edge Enterprise Edge West end Branch East end Branch LT Dl COUT TDR El ss CT ON IP 192 1 1 2 IP 192 1 1 3 Meridian M1 DN 4221 IP 192 1 1 4 PRI public protocol Remote Gateway Configuration Central Office East end If the quality of the IP trunk connection during initial call setup rates as poor Enterprise Edge finds an alternate route to complete the call fallback based on the programming definitions in the routing table In this example if the quality of the IP connection is poor during the call setup phase the call
46. es is under 18 ms Within the U S the propagation delay from coast to coast is under 40 ms To estimate the propagation delay of long haul and trans oceanic circuits use the rule of thumb of 1 ms per 100 terrestrial miles If a circuit goes through a satellite system estimate each hop between earth stations to adds 260 ms to the propagation delay Serialization delay The serialization delay is the time it takes to transmit the voice packet one bit at a time over a WAN link The serialization delay depends on the voice packet size and the link bandwidth and is the result of the following formula IP packet size in bytes serialization delay in ms 8 X link bandwidth in kbit s PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 32 Engineering guidelines Queuing delay The queuing delay is the time it takes for a packet to wait in the transmission queue of the link before it is serialized On a link where packets are processed in a first come first served order the average queuing time in ms and is the result of the following formula eee X px average packet size in bytes 1 p ink speed in kbit s Note where p is the link utilization level The average size of intranet packets carried over WAN links generally is between 250 and 500 bytes Queueing delays can be important for links with bandwidth under 512 kbit s while with higher speed links they can allow higher utilization levels Routing
47. fails the VoIP function is lost See the Configuration chapter on page 61 for additional information on entering the Local Gateway IP address For more information see also the Enterprise Edge Programming Operations Guide PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 20 Engineering guidelines LAN engineering Engineering the network for worst case numbers indicates the spare bandwidth a LAN must have to handle peak traffic It is important the LAN be planned to handle the IP telephony traffic using the defined codec without Ethernet delay or packet loss The installer or administrator must select one configuration and then set up the LAN so there is more bandwidth than the IP telephony output Refer to standard Ethernet engineering tables for passive 10BaseT repeater hubs Refer to the manufacturer s specification for intelligent 10BaseT layer switches Table 1 LAN and WAN IP bandwidth usage per Enterprise Edge Gateway loaded to 36 CCS per port per hour with silence compression Codec Type Packet Voice fax IP packet Ethernet Bandwidth Bandwidth duration payloadin in bytes4 frame usage usage on in ms bytes bytes on LAN WAN in payload in kbit s kbit s G 7296 10 10 50 76 60 8 20 07 8 kbit s 36 20 60 86 34 4 12 0 30 30 70 96 25 6 9 3 G 723 1 30 20 60 86 22 9 8 0 5 3 kbit s G723 1 6 3 30 24 64 90 24 0 8 5 kbit s Note 1 LAN data rate i
48. ges of traffic in the intranet include some Ping samples during the intranet s peak hour For a more complete evaluation of the intranet s delay characteristics get Ping measurements over a period of at least a week Measuring end to end packet loss The Ping program also reports if the packet made its round trip correctly or not Use the same Ping host setup to measure end to end errors Use the same packet size Sampling error rate require taking multiple Ping samples at least 30 An accurate error distribution requires data collection over a greater period of time The error rate statistic from multiple Ping samples is the packet loss rate Recording routes As part of the network evaluation record routing information for all source destination pairs Use the Traceroute tool to record routing information A sample of the output of the Traceroute tool follows C WINDOWS gt tracert 10 10 10 15 Tracing route to 10 10 10 15 over a maximum of 30 hops ms lt 10 ms tftzrafl ca nortel com 10 10 10 1 ms ms 1 ms 10 10 10 57 1 1 ms 2 ms 3 ms tcarrbf0 ca nortel com 10 10 10 2 ms 7 ms 5 ms bcarha56 ca nortel com 10 10 10 15 ms 3 1 4 8 Trace complete The Traceroute program checks if routing in the intranet is symmetric or not for each source destination pairs Also the Traceroute program identifies the intranet links used to carry voice traffic For example if Traceroute of four site pairs gets the results shown
49. ho cancellation can cause broken speech in conversations in a low audio conversation Although echo cancellation can be disabled it is not recommended Non linear processing Non linear processing NLP is part of echo cancellation It improves echo cancellation by reducing remaining echo NLP mutes background noise during periods of far end silence and prevents additional comfort noise from occurring Some listeners find muted background noise a problem NLP can be disabled to prevent this but with the trade off of increased heard echo Jitter buffer A major cause to reduced voice quality is IP network packet delay and network jitter Network delay represents the average length of time for a packet to move across a network Network jitter represents the differences in arrival time of a packet Both important in determining voice quality delay is like the average jitter is like the standard deviation To allow for differences in arrival time of a packet and continue to produce a steady out going stream of speech the far end gateway does not play out the speech when the first packet arrives Instead it holds it for a some time in part of its memory called the jitter buffer and then plays it out The amount of this hold time is the measure of the jitter buffer for example a 50 ms hold time indicates a 50 ms jitter buffer As the network delay total time including codec processing time exceeds about 200 ms the two speakers increasingl
50. ide PO911590 Issue 02
51. ing plan section IP trunks also use this capability One capability unique to IP trunks takes advantage of the QoS monitoring that is part of IP Telephony With fallback to normal circuit switched facilities enabled in the local gateway configuration calls route to the circuit switched facilities if the QoS is below the permitted threshold The installer configures fallback as follows e Launch the Unified Manager e Select the IP Telephony radio button Enable fallback in the local gateway configuration Enable QoS monitoring for the required destinations in the remote gateway configuration Set the Tx and Rx thresholds MOS numbers for the required QoS e Launch Enterprise Edge Unified Manager Configure all alternate routes for the IP trunks Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Configuration Enterprise Edge VoIP Gateway uses a menu driven interface for operations administration and maintenance OA amp M The interface includes a display pull down menus dialog windows status bars page contents and data A radio button provides access to the interface from the Enterprise Edge Unified Manager shell Figure 11 Enterprise Edge Unified Manager ie Bape Caprice The IP telephony main menu is part of the Services menu When you click on IP Telephony to access the sub menus in the interface the IP telephony version appears as Figure 12 Figure 12 Enterpris
52. is state can be true when the flow is on a symmetric route caused by the asymmetric behavior of the data processing services Late packets Packets that arrive outside of the window allowed by the jitter buffer are discarded To determine which Ping samples to ignore calculate the average one way delay based on all the samples Add 300 ms to that amount This amount is the maximum delay All samples that exceed this one way delay maximum are considered late and are removed from the sample Calculate the percentage of late packets and add that percentage to the packet loss statistic Measurement procedure The following procedure is an example of how to get delay and error statistics for a specific site pair during peak hours PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 30 Engineering guidelines Program a script to run the Ping program during intranet s peak hours repeatedly sending a series of 50 Ping requests Each Ping request generates a summary of packet loss with a granularity of 2 and for each successful probe that made its roundtrip that many rtt samples For a strong network there must be at least 3000 delay samples and 60 packet loss samples Have the raw output of the Ping results stored in a file Determine the average and standard deviation of one way delay and packet loss Repeat this for each site pair At the end of the measurements the results are as shown in Table 7 Table 7 Dela
53. ise Edge Programming Operations Guide for information about installing these components Enterprise Edge product software Keycode software key that allows IP telephony refer to the Systems operations chapter Software keys section in the Enterprise Edge Programming Operations Guide Media Services Card MSC contains the Central Processing Unit CPU and the MSPEC slots refer to the Hardware Description chapter in the Enterprise Edge Programming Operations Guide Media Services Processing Expansion Cards MSPEC plug into the MSC to provide additional resources refer to the Hardware Description chapter in the Enterprise Edge Programming Operations Guide Installation flowchart Figure 9 Configuring the local gateway installation flowchart and Figure 10 Configuring the remote gateway installation flowchart show how to install a local gateway and how to add a remote gateway Configuring a local gateway The installer sets the characteristics of the local gateway These characteristics determine the bandwidth and QoS requirements for all calls over IP telephony Launch Enterprise Edge Unified Manager Enter the Enterprise Edge VoIP Gateway keycode Perform a warm reset by following the procedure in the Maintenance chapter of the Enterprise Edge Programming Operations Guide Select the Enterprise Edge VoIP Gateway radio button Enter the codecs Enable or disable echo cancellation
54. ism Under this design TCP increases its window size increasing throughput until congestion occurs Congestion results in packet losses and when that occurs the throughput decreases and the whole cycle repeats When multiple TCP sessions flow over few congestion links in the intranet the flow control algorithm can cause TCP sessions in the network to decrease at the same time causing a periodic and synchronized surge and ebb in traffic flows WAN links can appear to be overloaded at one time and then followed by a period of under utilization There are two results e bad performance of WAN links e IP telephony traffic streams are unfairly affected Enterprise Edge Router QoS Support In Enterprise Edge the VoIP gateway and the router are in the same box The Enterprise Edge router performs QoS and priority queuing to support VoIP traffic The router supports VoIP in the following two ways e Ina DiffServ network Enterprise Edge acts as a DiffServ edge device and performs packet classification prioritization and marking The router performs admission control for H 323 flows based on the WAN link bandwidth and PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 36 Engineering guidelines utilization When received the WAN link marks the H 323 flows as Premium traffic and places the flows in the high priority queue Note Differentiated Service DiffServ is a QoS framework standardized by IETF e Inanon
55. itoring of gateways e Circuit switched voice facilities fallback capability The core telephony service made available through Enterprise Edge considers the Enterprise Edge VoIP Gateway as a trunk The IP trunk uses the trunking and routing functionality of the Enterprise Edge product portfolio The IP trunks are an important part of the Enterprise Edge product portfolio Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Overview 9 VoIP Gateway trunks are supervised trunks with answer and disconnect supervision The VoIP Gateway supports voice and fax calls See the Engineering guidelines chapter on page 15 for more information about fax calls VoIP Gateway does not support modem calls The IP telephony gateway allows communication with other supported gateways and H 323v2 gateways through trunk calls The IP telephony gateway supports Direct Routed communication The local gateway performs the address resolution and maintains the remote gateway table The ITU H 323v2 Gatekeeper allows for centralized configuration of IP address information Two call signaling protocols are available in Enterprise Edge 2 0 e Direct routed where Enterprise Edge uses a locally maintained table for IP resolution The locally maintained table is the remote gateway table See the Configuration chapter on page 61 for information about the remote gateway table e Gatekeeper routed where Enterprise Edge uses a centralized gatekeeper for
56. l if there are not enough DSP resources available All VoIP Gateway facilities can appear to be in use although there are DSP resources available for calls using other codec types Because most gateways support the G 711 codec configure G 711 as a supported codec The G 711 codec does not compress audio or fax The G 711 codec supports two IP trunks on each MSPEC See the Enterprise Edge Programming Operations Guide for additional information G 711 This codec delivers toll quality audio at 64 kbit s This codec is best for speech because it has the smallest delay and is very strong to channel errors However the G 711 codec uses the largest bandwidth North America uses G 711 u LAW and international markets use G 711 A LAW Silence compression G 723 1 and G 729 Annex B support Silence compression A key to VoIP Gateway s in business applications is reducing WAN bandwidth use Beyond speech compression the best bandwidth reducing technology is silence compression also known as silence suppression Silence compression technology identifies the periods of silence in a conversation and stops sending IP speech packets during those periods Telco studies show that in a typical telephone conversation only about 36 40 of a full duplex conversation is active When one person talks the other listens known as half duplex And there are important periods of silence during speaker pauses between words and phrases By applying silence
57. le MOS Range Qualitative Scale 4 86 to 5 00 Excellent 3 00 to 4 85 Good 2 00 to 2 99 Fair 1 00 to 1 99 Poor Set the MOS values using the lowest number matching to the required threshold You can adjust the MOS values to fine tune the fallback scale Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 37 IP telephony settings Codec types The term codec refers to the voice coding and compression algorithm used by the DSP on the telephony services and the MSPECs See the Enterprise Edge Programming Operations Guide for additional information on DSP and MSPEC resources Determine the codec type for a VoIP Gateway call basis at call setup The originating gateway indicates to the remote gateway which codec types it supports starting with the selected order of use The remote gateway depending on its capabilities selects one of the codec types and continues with the call If both ends cannot agree on a codec type the call fails All gateways in the intranet must use the same codec types Configure each gateway with available codecs with the selected order of use The codecs configuration must reflect available bandwidth on the network Codec options are between quality compared to bandwidth The supported codec types are configured in the Modifying the Local Gateway Configuration table section on page 65 The G 711 codec provides the best audio quality but uses the greatest
58. ls are done by dialing a 4 digit private network DN For example if a user in the west end branch calls a user in the east end branch within the private network they dial 6221 Note Enterprise Edge IP telephony requires a keycode After entering the keycode for Enterprise Edge IP Telephony perform a warm reset by following the procedure in the Maintenance chapter of the Enterprise Edge Programming Operations Guide Figure 8 Toll bypass Network 2221 Network 6221 Received 2221 Received 6221 Internal 2221 Internal 6221 Corporate IP Network IP IP a Enterprise Edge Toronto Branch Enterprise Edge IP 192 1 1 2 Ottawa Branch IP 192 1 1 3 PRI public protocol PRI public protocol Public Public Network Network The Call Manager at the Toronto office examines the dialed digits and determines the call can be routed to the IP address matching to the Ottawa office The Ottawa office receives the call sees that the leading digit s match its Private Network Access Code and uses a destination code to route the call over its public trunks to the PSTN This is acommon example with only calls to the 613 Area Code routed by the Ottawa node In a real world configuration it can be a consideration to handle Area Codes that are close for example Montreal 514 In Table 10 Private and public network routing T
59. lts in the configuration of an alternate route if configured Until the QoS improves IP trunks are all considered busy Enable QoS monitoring for the required destination in the Modifying the Remote Gateway Configuration table on page 66 To prevent a few bad sites from starting fallback disable the QoS monitoring for remote gateways which have QoS problems until solved Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 43 Set the Tx and Rx thresholds MOS numbers for the remote gateway with the required QoS level as indicated in the Modifying the Remote Gateway Configuration table on page 66 The fallback threshold algorithm considers a fixed IP telephony delay of 140 ms This delay is based on the default settings and its delay monitoring probe packets The fallback mechanism does not adjust when the parameters are modified from their default values Users can sense a lower quality of service than the QoS levels at fallback thresholds when e Delay variation in the intranet is important If the standard deviation of one way delay is like the jitter buffer maximum delay it means that there is a group of packets that arrive late to be used by the gateway in the playout process e The jitter buffer is increased The real one way delay is greater than that estimated by the delay probe e The codec is G 711 The voice packets formed by this codec are larger 120 to 280 bytes than the dela
60. n Code 916A Normal route 004 Absorb 1 Destination Code O1A Normal route 004 Absorb 1 Destination Code 9A Normal route 004 Absorb 1 Ottawa office Trunk Line Data Line 241 Target line Received 6221 Line Access Set 6221 L241 Ring only Line pool access Line pool A Line pool PRI A To Toronto office Services Routing Service Route 001 Use Pool A External leave blank DN type Private Route 002 Use Pool PRI A External leave blank DN type Private Destination Code 2 Normal route 002 Absorb None Schedule 4 001 Absorb None To Toronto Public Network Services Routing Service Route 003 Use Pool A External leave blank DN type Public Enterprise Edge 2 0 IP Telephony Configuration Guide PO91 1590 Issue 02 Engineering guidelines 51 Heading Parameter Setting Services Routing Service Route 004 Use Pool PRI A External leave blank DN type Public Destination Code 91416 Normal route 004 Absorb 1 Schedule 4 003 Absorb None To Public Network Services Routing Service Destination Code 9141A Normal route 004 Absorb 1 Destination Code 914A Normal route 004 Absorb 1 Destination Code 91A Normal route 004 Absorb 1 Destination Code 9A Normal route 004 Absorb 1 The impact on the configuration on each node are e each node must have the Private Network Access Code set
61. nal destination codes These destination codes point to line pools which contain PSTN trunks For information about line pools see the Enterprise Edge Programming Operations Guide Configuration of fallback to conventional circuit switched facilities If the measured Mean Opinion Score MOS for all codecs is below the configured threshold for any monitored gateway the Fallback to Conventional Circuit switched services activates This feature reroutes calls to different trunks such as the Public Switched Telephone Network PSTN until the network QoS improves When the QoS meets or exceeds the threshold calls route over the IP network PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 68 Configuration With the fallback feature disabled calls move across the IP telephony trunks no matter the QoS The fallback feature is only active at call setup A call in progress does not fall back if the QoS degrades Calls fallback if there is no response from the destination an improperly configured remote gateway table or if there are not enough DSP resources available to handle the new call IP trunks on the core telephony services use routes to determine which outgoing facilities to use A given destination code can have an alternate route configured The alternate route is used if the main route is not available to process calls For example if all the lines in a line pool are busy IP trunks also use this capability On
62. ny remote gateway configuration the call fails The installer and administrator need to understand the core telephony services See the Enterprise Edge Programming Operations Guide for more information See the Configuration chapter on page 61 for more information about core telephony services set up and configuring the remote gateway Post installation network measurements The design process is continuous even after implementation of the IP telephony and commissioning of voice services over the network Network changes in real IP telephony traffic general intranet traffic patterns network controls network topology user needs and networking technology can make a design no longer valid or non compliant with QoS objectives Review designs against prevailing and trended network conditions and traffic patterns every two to three weeks at the start and after four times a year Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 53 When operating IP telephony services a customer s organization must have or include processes to monitor analyze and perform design changes to the IP telephony and the corporate intranet These processes ensure that both networks continue to conform to internal quality of service standards and that QoS objectives are always met Setting IP telephony QoS objectives The installer or administrator needs to state the design objective of IP telephony the p
63. odifying the Local Gateway Configuration table The pull down menu Configuration contains the Modify Entry option The Modify Entry option allows the administrator to change the settings for the supported codecs non linear processing silence compression and the jitter buffers Echo cancellation cannot be disabled If the administrator selects an entry and selects the Modify Entry option a dialog box appears The dialog box allows the administrator to select a new value The Modify Entry option allows the administrator to change the order of the Preferred codecs through a set of five dialog boxes Each dialog box contains a list of the supported codecs and a none option The administrator selects from the list for each of the five boxes and the result of the information appears in the Supported Codecs field Stop and restart the gateway to change the configuration to the new settings Select VoIP Gateway from the Unified Manager menu then select the Status pull down menu Click on Disabled then click on Enabled The new configuration is active when the status returns to Up Changes to the Local Gateway Configuration table only begin on the next call Calls in progress are not affected Remote Gateway Configuration The Remote Gateway Configuration menu manages the Remote Gateway Configuration table The gateway configuration table contains the IP address destination digits and QoS threshold for each remote gateway The gateway configura
64. on Note 6 IP telephony uses a frame duration of 20 ms for G 729 and G 711 Note 7 If interworking with an M1 ITG other frame durations are supported config ured on the M1 ITG Example 1 LAN engineering voice calls Consider a site with four Enterprise Edge IP telephony ports The Preferred codec is G 729 using a voice payload of 20 ms Silence compression is enabled Given the above what is the peak traffic in kbit s that IP telephony will put on the LAN With Table 1 LAN and WAN IP bandwidth usage per Enterprise Edge Gateway loaded to 36 CCS per port per hour with silence compression on page 20 for calls with silence compression each port generates 34 4 kbit s when engaged in a call to another gateway If all four ports are in use then the additional load is 137 6 kbit s Example 2 LAN engineering fax calls Consider a site with four IP telephony ports The required codec is G 711 with a voice payload of 20 ms Silence compression is not used PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 22 Engineering guidelines With Table 2 LAN and WAN IP bandwidth usage per Enterprise Edge Gateway loaded to 36 CCS per port per hour without silence compression on page 21 for calls without silence compression each fax call generates 180 8 kbit s If all four ports are in use for fax calls then the additional load is 723 2 kbit s For more information about fax calls see the Fax calls sec
65. on 52 D Destination Digits 66 Dialing plan 17 67 Direct Inward Dial 67 E Echo Cancellation 64 Echo cancellation 13 40 end to end network delay 27 end to end packet loss 28 Engineering Specifications 71 F Fallback 11 42 fallback 67 fallback routing 36 Fallback to Circuit switched 64 Fax Jitter Buffer 64 feedback 54 G G 711 38 G 723 1 37 G 729 37 Gatekeeper 8 Gatekeeper IP 64 Gatekeeper routed 9 GatekeeperResolved 65 GatekeeperRouted 65 Gateway Configuration Tables 65 H hop count 32 l inappropriate load splitting 34 interoperability 71 Introduction 7 Enterprise Edge 2 0 IP Telephony Configuration Guide Index 75 J jitter 11 jitter buffer 40 jitter buffer size 33 L link delay 32 Local gateway 63 Local Gateway IP 64 M Measuring Intranet QoS 27 Modifying the Gateway Configuration Table 66 Modifying the Vocoder Table 65 N network loading 24 network measurements 52 Non linear Programming 64 O OA amp M 61 P Packet delay 11 packet errors 33 Packet loss 11 Ping 12 ping 27 29 Q QoS 34 QoS Monitor 66 69 QoS Rx 66 QoS Tx 66 Quality of Service Monitor 69 R Remote gateway 65 Routing and hop count 32 routing instability 34 S Silence Compression 64 Silence suppression 13 Supported Codecs 64 System Functionality 8 U User Interface 62 P0O9 11590 Issue 02 76 Index V Voice Jitter Buffer 64 Enterprise Edge 2 0 IP Telephony Configuration Gu
66. on 72 Glossary 73 Index 75 PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 6 Contents Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Overview The Enterprise Edge VoIP Gateway reduces communication costs by routing voice traffic over private Internet Protocol IP networks as part of the Enterprise Edge product portfolio Enterprise Edge uses IP telephony to link multiple sites together using an existing corporate data network The IP trunks are an important part of the telephony services IP telephony is transparent to users IP telephony involves the conversion of voice from its normal telephony format continuous analog or digital signal into a digital packet format transported over an intranet IP telephony operates on an installed corporate IP network IP telephony requires a correctly managed intranet instead of the internet The private IP network facilities must have sufficient bandwidth on the private Wide Area Network WAN backbone The Engineering guidelines chapter on page 15 contains information about determining if your corporate IP network can support IP telephony A keycode controls the number of supported IP ports IP telephony uses a Web based browser for configuration See the Configuration chapter on page 61 for information about how to configure IP telephony The VoIP Gateway supports ITU H 323v2 gatekeeper operation The VoIP Gateway allows Enterprise Edge
67. on page 27 The next step is to find out the current utilization of those links Note the reporting window that appears in the link utilization report For example the link utilization can be an average of a week a day or one hour To be consistent with the dimensioning considerations see Enterprise Edge VoIP Gateway bandwidth engineering on page 17 get the peak utilization of the trunk Also because WAN links are full duplex that data services show asymmetric traffic behavior get the utilization of the link representing traffic flowing in the heavier direction The third step is to determine the available spare capacity Enterprise Edge intranets are subject to capacity planning controls that ensure that capacity use remains below some determined utilization level For example a planning control can state that the utilization of a 56 kbit s link during the peak hour must not exceed 50 for a T1 link the threshold is higher for example at 85 The carrying capacity of the 56 kbit s link can be 28 kbit s and for the T1 1 3056 Mbit s In some organizations the thresholds can be lower than that used in this example in the event of link failures there needs to be spare capacity for traffic to be re routed Some WAN links can be provisioned on top of layer 2 services such as Frame Relay and ATM the router to router link is a virtual circuit which is subject not only to a physical capacity but also a logical capacity limit The ins
68. oronto to Ottawa office on page 49 private network routing information appears in gray Public network routing information appears in white Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 49 Table 10 Private and public network routing Toronto to Ottawa office Calls to Ottawa office Heading Parameter Setting Toronto office Lines Trunk Line Data Line 241 Target line Received 2221 Terminals amp Sets Line Access Set 221 L241 Ring only Line pool access Line pool A Line pool PRI A Services Routing Service Route 001 Use Pool A External leave blank DN type Private Services Routing Service Route 002 Use Pool PRI A External leave blank DN type Private Services Routing Service Destination Code 6 Schedule 4 001 Absorb None Normal route 002 Absorb None Calls to Ottawa Public Network Services Routing Service Route 003 Use Pool A External leave blank DN type Public Route 004 Use Pool PRI A External leave blank DN type Public Destination Code 91613 Normal route 004 Absorb 1 Schedule 4 003 Absorb None PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 50 Engineering guidelines Heading Parameter Setting To Public Network Services Routing Service Destination Code 9161A Normal route 004 Absorb 1 Destinatio
69. over the IP network Disable the fallback feature in the Local Gateway Configuration With the fallback feature disabled calls move across the IP telephony trunks no matter the QoS The fallback feature is only active at call setup A call in progress does not fall back if the QoS degrades Calls fallback if there is no response from the destination an incorrectly configured remote gateway table or if there are not enough DSP resources available to handle the new call PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 12 Overview Network Performance Utilities There are two common network utilities Ping and Traceroute These utilities provide a method to measure quality of service parameters Other utilities used also find more information about VoIP Gateway network performance Note 1 Because data network conditions can vary at different times collect performance data over at least a 24 hour time period Note 2 Use performance utilities to measure performance from each gateway to every other gateway Ping Ping Packet InterNet Groper sends an ICMP Internet Control Message Protocol echo request message to a host expecting an ICMP echo reply which allows for the measurement of a round trip time to a selected host By sending repeated ICMP echo request messages percent packet loss for a route can be measured Traceroute Traceroute uses the IP TTL time to live field to determine router hops to a s
70. pecific IP address A router must not forward an IP packet with a TTL field of 0 or 1 Instead a router discards the packet and returns to the originating IP address an ICMP time exceeded message Traceroute uses this mechanism by sending an IP datagram with a TTL of 1 to the selected destination host The first router to handle the datagram sends back a time exceeded message This message identifies the first router on the route The Traceroute transmits a datagram with a TTL of 2 Following the second router on the route returns a time exceeded message until all hops are identified The Traceroute IP datagram has a UDP Port number not likely to be in use at the destination normally gt 30 000 The destination returns a port unreachable ICMP packet The destination host is identified Traceroute is used to measure round trip times to all hops along a route identifying bottlenecks in the network Codecs The term codec refers to the voice coding and compression algorithm used by the DSP on the telephony services and the MSPECs See the Enterprise Edge Programming Operations Guide for additional information on DSP and MSPEC resources The codec type for a VoIP Gateway call basis is determined at call setup The originating gateway indicates to the remote gateway which codec types it supports starting with the selected order of use The remote gateway depending on its capabilities selects one of the codec types an
71. rces Assign IP trunks to pools Route assignment Destination code assignment Target line assignment Figure 10 Configuring the remote gateway installation flowchart Launch Enterprise Edge Unified Manager Choose the VolP Gateway Configure IP address for radio button remote gateway Enable or disable QoS Set QoS thresholds Choose Telephony Assign IP trunks to under Resources __ pool Route assignment Destination code assignment Target line assignment PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 60 Installation Fallback to normal circuit switched services configuration If the measured Mean Opinion Score MOS exceeds the configured threshold for any monitored gateway the fallback to normal circuit switched services is triggered This feature reroutes calls to other trunks such as PSTN until the network QoS improves to exceed the configured threshold IP trunks on the core telephony services use routes to determine which outgoing facilities to use A given destination code can have an alternate route configured This alternate route is used if the main route is not available to process calls For example the alternate route is used if all the lines in a line pool are busy See the Systems Operation chapter of the Enterprise Edge Programming Operations Guide See Dial
72. rk Quality of Service Enterprise Edge VoIP Gateway uses a method like the ITU T Recommendation G 107 the E Model to determine the voice quality This model evaluates the end to end network transmission performance and outputs a scalar rating R for the network transmission quality The packet loss and latency of the end to end network determine R The model correlates the network objective measure R with the subjective QoS metric for voice quality MOS or the Mean Opinion Score This model provides an effective traffic building mechanism by activating the Fallback to Circuit Switched Voice Facilities feature at call set up to avoid quality of service degradation New calls fall back when the configured MOS values for all codecs are below the threshold The model is the reason for compression characteristics of the codecs Each codec delivers a different MOS for the same network quality Network Monitoring The VoIP Gateway network monitoring function measures the quality of service between the local and all remote gateways on a continuous basis The network monitoring function exchanges UDP probe packets between all monitored gateways to collect the network statistics for each remote location All the packets make a round trip from the Sender to Receiver and back to the Sender From this information you can calculate the latency and loss in the network for a distinct location Note 1 Quality of Service monitoring is not s
73. rmal route 002 Absorb None East End office Trunk Line Data Line 241 Target line Received 6221 Line Access Set 6221 L241 Ring only Line pool access Line pool A To Head Office M1 PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 46 Engineering guidelines Heading Parameter Setting Service Routing Service Route 001 Use Pool A External leave blank DN type Private Destination Code 4 Normal route 001 Absorb None To West End Service Routing Service Destination Code 2 Normal route 001 Absorb None To Public Network Service Routing Service Route 002 Use Pool A External leave blank DN type Public Destination Code 9 Normal route 002 Absorb None In this example outgoing public network calls dialed from a Enterprise Edge route to the Meridian M1 and the Meridian M1 is responsible for seizing a public trunk For this reason the 9 prefix remains in the number passed to the Meridian 1 Note For IP trunks ensure the programming selection is Line Pool A Set the Private Network Access Code to 9 on each Enterprise Edge system to ensure the algorithm for outgoing IP calls include this additional digit The Meridian M1 must identify incoming 2xxx and 6xxx DID calls and route the call over IP trunks to either the East or West end offices The Meridian M1 must identify numbers starting with 9 as
74. s exercise the traffic flow from every site pair needs to be summed to calculate the load on each route and loaded to the link Figure 3 Calculating network load with IP telephony traffic D Santa Clara Santa Clara Richardson traffic Otawa Tokyo traffic Santa Clara Tokyo traffic Enterprise Edge IP telephony if Router Richardson Enough link capacity Table 3 Link capacity on page 25 sorts the computations so that for each link the available link capacity is compared against the additional IP telephony load For example on link R4 R5 there is capacity 568 kbit s to allow for the additional 96 kbit s of IP telephony traffic Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 25 Table 3 Link capacity Link Utilization Incremental IP telephony Available load Enough End Capacity Threshold Used TOPA Site pair Traffic capacity Points kbit s bit s kbit s RI R2 1536 85 75 154 Santa Clara 15 5 Yes Ottawa Santa Clara Tokyo RI R3 1536 R2 R3 1536 R2 R4 1536 R4 R5 1536 85 48 568 Santa Clara 24 Yes Richardson Ottawa Tokyo Santa Clara Tokyo Some network management systems have network planning modules that determine network flows These modules provide more detailed and accurate analysis as they can include correct node link and routing information They also help the installer or administrator
75. s the effective Ethernet bandwidth use Note 2 LAN kbit s Ethernet frame bytes 8 1000 Frame duration in ms Note 3 50 voice traffic reduction due to silence compression no compression for fax Note 4 Overhead of RTP UDP IP packet over voice packet is 40 bytes overhead of Ethernet frame over IP packet is 26 bytes Note 5 Keep Ethernet bandwidth to support an Interframe gap of at least 12 bytes per frame This gap is not included in the above bandwidth calculation Note 6 IP telephony uses a frame duration of 20 ms for G 729 Note 7 If interworking with an M1 ITG other frame durations are supported config ured on the M1 ITG Silence compression If an IP gateway acts as a tandem switch in a network where circuit switched trunk facilities have a large amount of low audio level enabling silence compression also known as Voice Activity Detection degrades the quality of service causing broken speech Under tandem switching conditions with a large amount of low audio level disable the silence compression using the IP telephony interface With silence compression disabled the bandwidth use of the LAN WAN approximately multiplies by two Table 2 LAN and WAN IP bandwidth usage per Enterprise Edge Gateway loaded to 36 CCS per port per hour without silence compression on page 21 shows the full duplex bandwidth requirements with silence compression disabled Fax calls use a G 711 codec which does not support silence
76. se packet loss In a voice conversation gaps in the conversation represent packet losses Some packet loss less than 5 can be acceptable without audible degradation in voice quality Sporadic loss of small packets can be more acceptable than less frequent loss of large packets Packet delay Packet delay is the time between when a packet leaves and when a packet arrives at it s destination The total packet delay time includes fixed and variable delay Variable delay is the more manageable delay while fixed delay depends on the network technology The distinct network routing of packets are the cause of variable delays The gateway must be as close as possible to the network backbone WAN with a minimum number of hops to minimize packet delay and increase voice quality Delay variation jitter The amount of variation in packet delay is otherwise known as delay variations or jitter Jitter affects the ability of the receiving gateway to assemble voice packets received at irregular intervals into a continuous voice stream Fallback to circuit switched voice facilities If the measured Mean Opinion Score MOS for all codecs is below the configured threshold for any monitored gateway the Fallback to Conventional Circuit switched services activates This feature reroutes calls to different trunks such as the Public Switched Telephone Network PSTN until the network QoS improves When the QoS meets or exceeds the threshold calls route
77. sed to upgrade removes a source of packet errors on a distinct flow A reduction in hop count provides for less occurrences for routers and links to drop packets Other causes of packet errors not related to delay are as follows e Bad link quality e Overloaded CPU e Saturation e LAN saturation e Limited size of Jitter buffer If the underlying circuit has transmission problems high line error rates outages or other problems the link quality is bad Other services such as X 25 frame relay or ATM can affect the link Check with your service provider for information Find out what the router s threshold CPU utilization level is and check if the router conforms to the threshold If a router is overloaded the router is continuously processing intensive tasks Process intensive tasks prevent the router from forwarding packets Reconfigure or upgrade the router Routers can be overloaded when there are too many high capacity and high traffic links configured on it Ensure that routers are configured to vendor guidelines PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 34 Engineering guidelines Saturation refers to too many packets on the intranet Packets can be dropped on improperly planned or damaged LAN segments Packets that arrive at the destination late are not placed in the Jitter buffer and are lost packets See Adjust the jitter buffer size section on page 33 Routing issues Routing problems
78. st bandwidth reducing technology is silence compression also known as silence suppression Silence compression technology identifies the periods of silence in a conversation and stops sending IP speech packets during those periods Telco studies show that in a typical telephone conversation only about 36 40 of a full duplex conversation is active When one person talks the other listens known as half duplex And there are important periods of silence during speaker pauses between words and phrases For more information about silence compression see the Silence compression section on page 38 Echo cancellation When a two wire telephone cable connects to a four wire PBX interface or a central office CO interface the system uses hybrid circuits to convert between two wires and four wires Although hybrid circuits are very efficient in their conversion ability a small percentage of telephony energy is not converted but instead is reflected back to the caller This is called echo For more information about echo cancellation see the Echo cancellation section on page 40 PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 14 Overview Jitter buffer A major cause to reduced voice quality is IP network packet delay and network jitter Network delay represents the average length of time for a packet to move across a network Network jitter represents the differences in arrival time of a packet Both important in
79. systems to use a central facility for IP address resolution The VoIP Gateway uses standard Digital Signal Processor DSP voice coding The VoIP Gateway supports compression algorithms codecs such as G 711 G 723 and G 729 See Codec types on page 37 in the Engineering guidelines chapter for information about codecs The VoIP Gateway monitors the data network and reroutes calls to the conventional circuit switched voice facilities if Quality of Service QoS over the data network decreases This Fallback to Conventional Circuit Switched Voice Facilities feature allows the system and installer to determine the acceptable QoS over the data network The customer can configure QoS parameters according to their requirements See the Quality of service parameters section on page 10 and Configuration of fallback to conventional circuit switched facilities section on page 67 in the Configuration chapter for information about configuring the QoS parameters If the quality is below the expected level of QoS the conventional circuit switched voice facilities route is selected until the QoS returns to an acceptable level The VoIP Gateway also activates fallback for other cases when a call cannot be completed Examples include no response from the destination the remote gateway table is improperly configured or if there are not enough DSP resources to support the call PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 8 Overview
80. t 32 Routing issues 34 Implementing QoS in IP networks 34 Traffic mix 35 TCP traffic behavior 35 Enterprise Edge Router QoS Support 35 Implementing the network 36 LAN engineering 36 Setting the Quality of Service threshold for fallback routing 36 IP telephony settings 37 Codec types 37 Silence compression 38 Echo cancellation 40 Jitter buffer 40 Fax calls 41 Fallback threshold 42 Dialing plan 43 IP telephony and M1 networking 43 Enterprise Edge and a Gatekeeper 46 Toll bypass with VoIP telephony 47 Core telephony services configuration 52 Post installation network measurements 52 Setting IP telephony QoS objectives 53 Intranet QoS monitoring 53 User feedback 54 Engineering checklist 55 Installation 57 Installation flowchart 57 Configuring a local gateway 57 Configuring a remote gateway 58 Configuration 61 User Interface Overview 62 Local Gateway Configuration 63 Remote Gateway Configuration 65 Core telephony services configuration 67 Configuration of fallback to conventional circuit switched facilities 67 Maintenance 69 Quality of Service Monitor 69 Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Contents 5 Quality of Service Status 69 Using the QoS Monitor pull down View menu 69 Operational Statistics 69 Backup and Restore Procedures 69 Chapter 7 Interoperability 71 Interoperability considerations 71 Asymmetrical media channel negotiation 72 No feedback busy stati
81. table Core telephony services configuration Launch the Enterprise Edge Unified Manager and configure the following 1 Put the IP trunks into a line pool IP Telephony ports are IP trunks Start with Line 01 to a maximum of Line 08 depending on the keycode entered 2 Configure a route which uses the line pool linked with the IP trunks For IP trunks do not add or absorb because the IP telephony gateway receives the dialed digits as dialed 3 Enter a destination code which uses the route configured above Ensure the destination code is the identical to the destination digits in the Remote Gateway Configuration See the Remote Gateway Configuration section on page 65 The above procedure ensures Direct Outward Dial DOD calls go to a remote gateway To receive Direct Inward Dial DID calls configure DID lines also called target lines on the core telephony services The full dialed number passes from the originating to the destination gateway during call setup The destination gateway processes the dialed number to determine which DID line can terminate the call For private networking the call terminates at a terminal at the destination gateway Configure target lines which match to the dialed digits to complete private networking For a description of target lines and DID see the Enterprise Edge Programming Operations Guide For toll bypass the DID calls can terminate on an outgoing PSTN trunk To do this configure additio
82. taller or administrator needs to get the physical link capacity and the QoS parameters The important QoS parameters are CIR committed information rate for Frame Relay and MCR maximum cell rate for ATM The difference between the current capacity and its acceptable limit is the available capacity For example a T1 link used at 48 during the peak hour with a planning limit of 85 has an available capacity of about 568 kbit s PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 24 Engineering guidelines Determining network loading caused by IP telephony traffic At this point the installer or administrator has enough information to load the IP telephony traffic on the intranet Consider the intranet has the topology as shown Figure 3 Calculating network load with IP telephony traffic on page 24 and the installer or administrator wants to know in advance the amount of traffic on a specific link R4 RS Consider there are four IP telephony ports per site With the Enterprise Edge VoIP Gateway bandwidth engineering section on page 17 and Traceroute measurements the R4 R5 link is expected to support the Santa Clara Richardson Santa Clara Tokyo and the Ottawa Tokyo traffic flows The other IP telephony traffic flows do not route over R4 R5 A peak of eight calls can be made over R4 R5 for the four IP telephony ports per site R4 R5 needs to support the incremental bandwidth of 8 x 12 96 kbit s To complete thi
83. the following e LAN requirements LAN must be great enough for the number of calls plus the overhead e WAN requirements WAN must be great enough for the number of calls plus the overhead PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 18 Engineering guidelines Table 1 LAN and WAN IP bandwidth usage per Enterprise Edge Gateway loaded to 36 CCS per port per hour with silence compression on page 20 and Table 2 LAN and WAN IP bandwidth usage per Enterprise Edge Gateway loaded to 36 CCS per port per hour without silence compression on page 21 show the bandwidth use for the different codecs This data assumes that each port is complete to 36 CCS Centi call second CCS is a channel or circuit occupied for 100 s The worst case scenario is 100 utilization or 36 CCS Engineering the network for worst case numbers ensures that the network can handle peak traffic Multiple network interfaces The Enterprise Edge can have more than one IP address Figure 2 Multiple network interfaces has three Enterprise Edge systems each with more than one IP address available Define the IP address for the VoIP gateway in the Local Gateway table The other remote gateways use this address to communicate with the Enterprise Edge VoIP Gateway Figure 2 Multiple network interfaces Enterprise Edge 1 Enterprise Edge 2 Local Gateway Table Local Gateway Table Local Gateway IP Local Gateway IP IP2 IP3
84. tion on page 41 WAN engineering To get traffic to Wide Area Network WAN use the formula 0 5 x IP packet in bytes x 8 x 1000 payload in ms The reason for the reduction data rate is because of the type of a duplex channel ona WAN For example with G 711 codec a two way conversation channel has a rate of 128 kbit s However the same conversation on WAN for example a T1 requires a 64 kbit s channel only because a WAN channel is a full duplex channel Both talk and listen traffic use a part of the 10 Mbit s Ethernet channel while a conversation uses a 64 kbit s DSO duplex channel in a T1 or other WAN media Example 1 WAN engineering voice calls Consider a site with four IP telephony ports The Preferred codec is G 723 1 6 3 kbit s using a voice payload of 30 ms Silence compression is enabled Given the above what is the peak traffic in kbit s that IP telephony will put on the WAN With Table 1 LAN and WAN IP bandwidth usage per Enterprise Edge Gateway loaded to 36 CCS per port per hour with silence compression on page 20 for silence compression each port generates 8 5 kbit s when engaged in a call If all four ports are in use then the additional load is 34 kbit s Example 2 WAN engineering fax calls Consider a site with four IP telephony ports The G 711 codec automatically selected with a voice payload of 20 ms Silence compression is not used in the G 711 codec With Table 2 LAN and
85. tion table allows QoS monitoring to be enabled or disabled for each IP destination A pull down menu allows the administrator to modify the table PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 66 Configuration Table 14 Sample Remote Gateway Configuration Name IP Destination QoS QoS Tx QoS Rx Digits Monitor Threshold Threshold Toronto 10 10 10 1 6l Disabled 5 00 5 00 Santa Clara 10 192 5 2 6265 61408 Enabled 4 35 4 00 Montreal 10 192 5 5 6852 61514 Enabled 3 23 4 80 Calgary 10 192 5 6 6775 61406 Disabled 5 00 5 00 The Remote Gateway Configuration menu contains the following are fields e The Name field contains the name connected with the IP address Ensure this name is correct before pressing the Save button When saved the name cannot be changed e The IP field contains the IP address or the machine name of the destination gateway If the machine name is used disable QoS Only enter an IP address or machine name one time in the Remote Gateway Configuration table e The Destination Digits field contains the leading dialed digits that indicate which calls route to this remote gateway Separate groups of dialed digits with a space See the Dialing plan section on page 43 IP Telephony uses the best match algorithm to determine call destinations e The QoS Monitor field indicates the status of QoS monitor for the destination e The QoS Tx Threshold and QoS Rx Threshold
86. to the value 9 e each node must have destination codes that match the Private Network Access Code plus digits matching to calls terminating in the local PSTN For example if the Private Network Access Code is 9 the node in Ottawa can require a destination code of 91613 In the same way Toronto can require the following destination code 91416 Note For IP trunks ensure the programming selection is Line Pool A To allow for fallback to PRI trunks when the IP trunks are overflowed you must program the following Routing service settings e Set the start and end times for Sched 4 to 1 00 to allow IP calls can 24 hours a day e Program the Sched 4 Service setting to Auto and enable overflow routing by changing the Overflow setting to Y Yes e Define a control set for all sets on the system that make calls over IP trunks See the Enterprise Edge Programming Operations Guide for more information PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 52 Engineering guidelines Program Remote Packages so that the IP trunks in Pool A can access the lines in Pool PRI A in a toll bypass plan A Remote Package is a set of capabilities associated with an incoming trunk The default package is fully restricted so to change the restrictions configure a new Remote Package for each trunk For example you give package 01 access to pool PRI A and you assign package 01 to all IP trunks For more information see th
87. ts sent in a single expression Simultaneous two way separate transmission in both directions A codec that delivers toll quality audio at 64 kbit s This codec is best for speech because it has small delay and is very resillient to channel errors A codec that provides near toll quality at a low delay Uses compression to 8 kbit s 8 1 compression rate The G 729 codec allows the Enterprise Edge IP Telephony to support only four VoIP ports A codec that provides the greatest compression 5 3 kbit s or 6 3 kbit s Normally indicated for multimedia applications such as H 323 videoconferencing Allows connectivity to Microsoft based equipment Graphical User Interface The ITU standard for multimedia communications over an IP network Enterprise Edge IP Telephony supports H 323 Center of a star topology network or cabling system Internet Protocol IP Telephony Gateway Enterprise Edge 2 0 IP Telephony Configuration Guide 74 Glossary ITU kbit s LAN Latency MI ITG Mbit s Modem MOS MSC Noise OA amp M Packet Packet switched network PEC PSTN QoS RTP TCP IP Terminal Throughput Topology Voice Compression VoIP WAN WRED Enterprise Edge 2 0 IP Telephony Configuration Guide International Telecommunications Union kilobits per second Thousands of bits per second Local Area Network The amount of time it takes for a discrete event to occur Meridian Internet Telephony Gateway Mega
88. upported for non Enterprise Edge product locations and must be disabled Note 2 The Quality of Service threshold is configurable per remote gateway Note 3 Fallback starts for all new originating calls if the QoS of any monitored gateway is below its threshold Note 4 The fallback decision is made only at the originating gateway using the QoS thresholds monitored at the originating gateway for the destination gateway VoIP Gateway allows for manual configuration of QoS thresholds depending on the customer preference between cost and voice quality The Engineering guidelines chapter on page 15 provides the guidelines to determine the quality of service that supported for any given network Quality of service parameters Quality of Service is depends on end to end network performance and available bandwidth A number of parameters determine the VoIP Gateway QoS over the data network Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Overview 11 The VoIP Gateway monitoring function can take about 3 mins to respond to marginal changes in the network condition Fallback can be caused by any of the following reasons e Bad network conditions e The remote gateway is out of service e No network connection e Not enough DSP resources available Packet loss Packet loss is the percentage of packets that do not arrive at their destination Transmission equipment problems and high delay and congestion can cau
89. urpose of which sets the standard for evaluating compliance to meeting users needs When IP telephony is first installed set the design objectives based on the work done in Measuring Intranet QoS on page 27 The QoS objective is to ensure that for each destination pair the mean o of one way delay and packet loss is below a threshold value so that calls between those site pairs have a accurate QoS level The graphs in Setting QoS on page 26 with the QoS measurements can help the installer or administrator determine what threshold levels are appropriate The Table 11 IP telephony QoS objectives describes examples of IP telephony QoS objectives Table 11 IP telephony QoS objectives Site pair Enterprise Edge IP telephony QoS objective Fallback threshold setting Santa Clara Mean one way delay G one way delay lt 120 ms Excellent Richardson Mean packet loss o packet loss lt 0 3 Santa Clara Ottawa Mean one way delay o one way delay lt 150 ms Excellent Mean packet loss o packet loss lt 1 1 In following design cycles the QoS objective is reviewed and improved based on data collected from monitoring of intranet QoS Having decided on a set of QoS objectives the installer or administrator determines the planning threshold The planning thresholds are based on the QoS objectives These thresholds used to trigger the network implementation decisions when the prevailing QoS is within r
90. w audio level enabling silence compression degrades the quality of service causing broken speech Under tandem switching conditions with a large amount of low audio level disable the silence compression using the IP telephony interface Fax calls use a G 711 codec which does not support silence compression Fax calls require 64 kbit s bandwidth For more information about fax calls see the Fax calls section on page 41 PO911590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 40 Engineering guidelines Echo cancellation When a two wire telephone cable connects to a four wire PBX interface or a central office CO interface the system uses hybrid circuits to convert between two wires and four wires Although hybrid circuits are very efficient in their conversion ability a small percentage of telephony energy is not converted but instead is reflected back to the user This is called echo If the user is near the PBX or CO switch the echo comes back so quickly it cannot be detected However if the delay is more than about 10 ms the user can hear an echo To prevent this occurrence gateway vendors include special code in the DSPs that listens for the echo signal and subtracts it from the listener s audio signal Echo cancellation is important for gateway vendors because the IP network delay can be 40 50 ms so the echo from the far end hybrid can be important at the near end Far end echo cancellation removes this Ec
91. y and error statistics Destination Measured one way Measured packet loss Expected QoS level pair delay ms Mean Mean o Mean Mean o Mean Mean o Santa Clara 171 179 2 2 3 Good Good Richardson Santa Clara Ottawa Santa Clara Tokyo Richardson Ottawa Richardson Tokyo Ottawa Tokyo Other measurement considerations The Ping Statistics described above measure the intranet before IP telephony installation The measurement does not take into consideration the expected load provide by the IP telephony users If the intranet capacity is tight and the IP telephony traffic important the installer or administrator must consider making intranet measurements under load Apply load using traffic generator tools the amount of load must match the IP telephony offered traffic estimated in the Enterprise Edge VoIP Gateway bandwidth engineering section on page 17 Decision does the intranet meet IP telephony QoS needs The end of the measurement and analysis is a good indicator if the corporate intranet can deliver acceptable voice and fax services The Expected QoS level column in Table 7 indicates to the installer or administrator the QoS level for each site pair with the data To provide voice and fax services over the intranet keep the network within a Good or Excellent QoS level at the Mean o operating area Fax services must not travel on routes that have Fair or
92. y probe packets 60 bytes This means there is a greater delay felt per hop If there are low bandwidth links in the path then the one way delay is higher both in terms of average and variation Dialing plan The dialing plan determines the digits used to make and receive calls over the IP telephony Because all the gateways attached to the intranet must work together the installer and administrator ensures the control of the configuration of all gateways including the dialing plan and codec selections A local gateway at one location is a remote gateway from another location and reversed IP telephony supports wildcards through the best match algorithm All calls which do not have a specific match in the Modifying the Remote Gateway Configuration table on page 66 route through the generic IP address IP telephony and M1 networking This example shows a private network made of one central Meridian 1 and two smaller sites with Enterprise Edge systems connected over IP trunks through a corporate IP network This example can represent a large head office with the Meridian 1 connected to several smaller branch offices In this network only the head office has trunks connected to the public network The branch offices access the public network using IP trunks to the head office This configuration allows to save costs and to join together public access trunks Users at all three locations access the public network by dialing 9 follow
93. y use a half duplex communications mode where one speaks the other listens and pauses to make sure the speaker is done If the pauses are ill timed they end up stepping on each other s speech This is the problem that occurs when two persons speak over a satellite telephony connection The result is a reduction in voice quality Enterprise Edge 2 0 IP Telephony Configuration Guide PO911590 Issue 02 Engineering guidelines 41 When a voice packet is delayed and does not arrive at the far end in time to fit into the voice stream going out of the far end gateway it is discarded and the previous packet is replayed If the scenario occurs often or twice in a row the listener hears reduced voice quality The jitter buffer hold time adds to the delay so if the network has high jitter the effect is a long delay in the voice stream For example a network can have an average delay of 50 ms and a variability of 5 ms The network is said to have 5 ms of jitter a low figure The jitter buffer hold time is only 5 ms so the network total delay is 55 ms If a network has a low average delay of 15 ms but 10 of the time the delay goes out to a 100 ms while 90 of the time the delay is a brief 4 ms the jitter buffer is 100 ms and the total network delay is 115 ms a long delay Network jitter can be more important than average delay in many VoIP Gateway applications VoIP Gateway voice calls use an adaptive jitter buffer that changes the hol
94. ys over the corporate intranet The chapter describes how to qualify the corporate intranet to support an IP network This chapter indicates which changes ensure the maintenance of the quality of voice services when transferring those services from the PSTN This chapter also addresses requirements for the successful integration with a customer s existing local area network LAN By following these guidelines the installer can configure the IP to ensure the best cost and quality and within a calculated tolerance Enterprise Edge IP telephony Enterprise Edge IP telephony functions on a correctly provisioned and stable LAN Delay delay variation or jitter and packet loss must be minimized end to end across the LAN and WAN The installer must determine the design and configuration of the LAN and WAN that link the IP telephony system If the intranet exceeds it s capacity new calls to the IP telephony fall back to conventional circuit switched voice facilities to ensure the quality of service for new calls Overview Traditional networks depend on voice services such as LEC and IXC private lines With Enterprise Edge IP telephony technology IP telephony selects a new kind of delivery mechanism that uses packet switching over a data network a corporate intranet The IP gateway converts a steady stream digital voice into fixed length IP packets PO91 1590 Issue 02 Enterprise Edge 2 0 IP Telephony Configuration Guide 16 Engineering guidelines

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