Intel SIU520 SS7 User's Manual
Contents
1. Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note A Load sharing between link set 0 and link set 1 under normal Link Set id 0 M my am ole 0 kid 0 SIU520 Point Code 0x100 Link i dT sy D a gt rg 2 wl toe via v Link Set id 1 th Point Code 0x200 B Traffic sent over link set 1 under failure of STP Link Set id 0 SIU520 Link ig is Point Code ory Sie 0 0x100 i a ie gt Na Link Set id 1 Point Code 0x400 Point Code 0x300 Point Code 0x400 Point Code 0x300 Figure 4 SIU520 Connected to Mated STP Pair Providing Route Resiliency Failure of Routes Problem With a single route to a destination point code DPC service can be disrupted if all the links of the link set used to reach that signaling node fail Route failover is a standard MTP3 operation which does not require any specific action from the user application Solution To eliminate this single point of failure an alternative link set can be provided in the SIU520 system configuration to reach the same DPC Route failover is a standard MTP3 operation which does not require any specific action from the user application Note When an alternative route to a given DPC is defined in an SIU520 configuration file a choice must be made between two different traffic modes load sharing2. MTP Levels 1 3 Bi ne Application Distributed Layer 4 MAP or INAP Management or IS41 i 1 lt i Distributed MTP3 Management Link Set Ethernet Figure 5 Dual SIU Architecture Failure of Power Supply Problem Ensuring that the unit survives the loss of one power supply and making it possible to replace a failed power supply without affecting the availability of the system Solution The Intel NetStructure SIU520 SS7 signaling gateway can be optionally configured with a redundant and hot swappable power supply Details Please refer to Intel NetStructure S U520 Intel NetStructure SG430 Hardware User Manual Issue 3 to obtain part numbers for redundant power supplies for the SIU520 Failure of Signaling Interface Unit Problem Since the SIU520 provides an SS7 interface to a distributed application it is usually deployed for high density service platforms Should the SIU of a single SlU based system fail many resources telephony cir cuits to TCAP dialogues would become unavailable and would cause major service disruption Solution A major feature of the SIU architecture is that two units can be configured to operate as a single entity sharing the same local SS7 point code In normal operation signaling can be shared between two units In the event of a failure signaling is maintained by the remaining unit Details In a dual configuration one unit is assigned as SIUA
3. Note The TUP protocol does not currently support forcing of circuit states to INCOMING ACTIVE or OUTGOING ACTIVE this step should therefore be omitted No additional signaling should be exchanged for TUP calls that were in the answered state following the transfer In this case OUTGOING ACTIVE calls should be released at the appropriate time with a circuit reset Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note Recovery of the Failed Unit The host application is informed of recovery of the communication to the SIU with the same method used for notification of the failure The RSILMSG_LINK_ STATUS message in this case contains a status value of 1 link to SIU recovered The host nominated to receive management indications normally host 0 will also receive an API_MSG_SIU_STATUS message with status value 31 decimal indicating a host link has recovered to the specified host ID Transferring Control Back Immediately following re establishment of communication with the primary SIU the application should send deactivate circuit group messages to this SIU to ensure that groups are only active on the secondary unit this may be the case if the inter SIU link had also failed If the primary unit has recovered from a complete failure no circuit groups will be active This deactivate command will fail if the groups were not active and the application should ignore any
4. this command would be used to define a V 11 clock slave MTP LINK O 0O 0 O 1 1 1 1 0 0x4006 while MTP LINK 0 00041111 0 0x6006 would define a V 11 port clock master Routing Configuration A route should be defined on both SIVA and SIUB for the inter SIU link set using the MTP_ ROUTE command referencing the appropriate lt linkset_id gt with a lt dpc gt value set to the point code of the SIU pair This route may only be specified to operate over a single link set Each DPC that may be accessed from the application must have an accompanying MTP ROUTE declaration For dual operation each route includes a preferred link set the lt linkset_id gt parameter and a secondary link set specified by lt second_Is gt linkset_id should refer ence the link set connecting the SIU to the appropriate adjacent signaling point second_Is must be set to the linkset_id assigned to the inter SIU link set Circuit Group Configuration For dual operation each SIU should contain identical Circuit group declarations using the appropriate ISUP_CFG CCTGRP Or TUP_ CFG CTGRP commands These circuit group configurations do not become active on either unit until an Activate Circuit Group API command has been issued to a particular SIU Example Configuration To define routing to the DPC 200 below which is also the adjacent point code using the first E 1 port on the first signaling card in a SIU520 the configuration Figure 19 would be For
5. 0 MTP ROUTE 500 1 0x0020 0x0001 0 MTP ROUTE 600 1 0x0020 0x0001 0 For SIUB MTP CONFIG 0 0 0x0000 MTP LINKSET 0 300 1 0x8000 300 0x8 MTP LINKSET 1 500 1 0x0000 300 0x8 MTP LINK 0 0 0 0 1 1 1 1 0 0x6006 MTP LINK 1 1 0 0 1 2 1 2 16 0x0006 MTP ROUTE 300 0 0x0020 MTP ROUTE 400 0 0x0020 0x0001 0 MTP ROUTE 500 1 0x0020 0x0001 0 MTP ROUTE 600 1 0x0020 0x0001 0 20 Run time Operations of a Dual resilient SIU System Connecting a Host to Two SIUs In a dual SIU system each host should connect to both SIVA and SIUB at start up This is achieved using the rsicmd utility twice first with an siu_id of O for SIUA and second with an siu_id of 1 for SIUB For example if SIVA has an IP address of 123 234 345 110 and SIUB an IP address of 123 234 345 220 the entry in the host s system configuration file system txt would be FORK PROCESS rsicmd 0 Oxef 0 123 234 345 110 9000 FORK PROCESS rsicmd 1 Oxef 0 123 234 345 220 9000 The concerned module id Oxef in this case will receive status indications from the rsi process for both connections The id field of the MSG header is set to the siu_id to identify the link that each status indication relates to The ability to communicate between a host and an SIU is indicated by RSILMSG_STATUS messages received by the conc_id application process Oxef in this case Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway A
6. acknowledgement of this command with a status value indicating processing failure A busy response should cause the application to reattempt the deactivate When communication with the primary SIU has been re established the application should allow sufficient time to ensure that the communication is stable thus avoiding repeatedly transferring circuits between units After this time has expired the application should transfer control of the affected circuit groups back to the original SIU This is achieved by deactivating the groups on the secondary SIU and re activating the ones on the primary SIU However before the groups are deactivated the circuits in that group should be maintenance blocked Using the Circuit Group Supervision Control API message This does not affect any calls in progress but will prevent these circuits from being selected for any new incoming calls The application should also ensure that none of the affected circuits are selected for new outgoing calls When all existing calls are completed all the circuits are therefore idle the application should deactivate the circuit group by sending an APILMSG_COMMAND message with cmd_type of 9 to the secondary unit When the acknowledgement that this command has been success fully processed has been received the groups should be activated on the primary unit by sending an API_MSG_COMMAND message with cmd_type of 8 Once the acknowledgement of the activati
7. includes SS7 protocol layers as well as a configuration and management module The SIU520 supports multiple SS7 signaling links within the same pulse code modula tion PCM trunk interface or over multiple PCM trunks The SIU examines the timeslots carrying the SS7 informa tion and processes them accordingly outputting this data to the LAN using TCP IP Similarly it takes commands from the TCP IP LAN and converts those to SS7 signals for transmission to the SS7 network In the receive direc tion information is conveyed to the user application in structured messages placed in a sequential queue For both circuit and transaction related operations the SIU520 provides the ability to automatically distribute signaling information between a number of physically independent application platforms thus providing a degree of fault tolerance within the application space The SS7 signaling may be presented from the network multiplexed in a timeslot on an E 1 2 048 MB s or T 1 1 544 MB s also known as DS1 bearer or by a V 35 56 64 kb s synchronous serial interface For telephony operation using a telephony layer 4 protocol such as ISUP or TUP if the SS7 signaling is multiplexed onto a PCM bearer the voice circuits may be passed transparently through the SIU to the application platform that terminates the physical circuits See Figure 2 Circuit switched API Operation The message based application programming interface API opera
8. indicate SIUB When the link to the SIU that normally controls a circuit group the primary SIU becomes active the application should issue an activate group command to that SIU specifying that circuit group using its group ID The SIU processes API commands sequentially and the application must wait for an acknowledgement of this command before proceeding An acknowledgement that indicates busy should cause the application to re attempt the activate command The application should wait for a period of time sufficient to establish communication to the preferred SIU before deciding that the preferred unit is not available and activating circuit groups on the non preferred or secondary SIU Once the acknowledgement of the activation of a circuit group is received the circuits should be reset to force the circuits into a known idle state This is achieved using the Circuit Group Status Control CGSC Request API message detailed in the appropriate Programmer s Manual The circuit reset is acknowledged by the terminating exchange this acknowledgement is passed to the user application as a circuit group status confirmation API message On receipt of this the application may commence using the associated circuits for calls Failure Detection The event that triggers the application to transfer circuit groups from one SIU to another is loss of communication between the application and the SIU When the failure occurs the RSI tas
9. or failover In load sharing mode traffic sent towards the remote signaling point is shared between the two link sets In failover mode all traffic sent towards the remote signaling point will normally be sent using the primary link set unless this link set fails in which case the traffic will use the alternative link set See the ntel NetStructure SIU520 Developer s Manual for more information on the selection of traffic mode in the MTP_ROUTE command Details This example See Figure 4 shows two link sets each containing one link being used in load sharing mode to reach destination point code 0x400 MTP LINKSET lt linkset_id gt lt adjacent_spc gt lt num_links gt lt flags gt lt local_spc gt lt ssf gt MTP_LINKSET O 02200 2 0x0000 02100 0x08 MTP_LINKSET 1 0x300 2 00000 0100 0x08 MOE LINK lt link ic lt linkset ach lt link ret lt sle gt lt bp0s gt lt lollimk gt lt lojposz gt lt stream gt lt timeslot gt lt flags gt MiP LINK O 0 16 0x0006 MTE CNE 2 fd ft 2 1 16 0x0006 MTP LNE 2 T 0 0 2 2 16 0x0006 Mine iN 3 i id dt 3 amp 16 0x0006 MIME ROUTE lt C gt lt limksec ich lt User part mesk lt illags gt lt secome le gt lt je_mask gt MTP ROUTE 0x400 0 0x0020 0x0003 1 0x00000000 Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Ethernet SIUA API Layer Ethernet Driver
10. partner unit in response to an activate command from the host application and checks the status of each circuit group on the partner unit An API management event indication is given if dual control is detected Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note A Dual resilient SIUs running SS7 protocol stack to TCAP B Dual resilient SIUs running SS7 protocol stack up to SCCP Host 0 Host N Host 0 Host N Ethernet Ethernet Figure 13 Two Different Architectures for a TCAP Processing SIU System Dual SIU Architecture for Transaction based In the first case TCAP and potential layers sitting on top Applications of TCAP run on the application host s and an additional There are two ways of architecting a dual resilient piece of software is required on each SIU to distribute SIU520 based system for processing TCAP transactions TCAP transactions to multiple application hosts This software option is called distributed transaction server Running the SS7 stack up to SCCP on the SIUs DTS Figure 13 depicts this architectural difference Running the SS7 stack up to TCAP on the SIUs 13 Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Ethernet Signaling B Transmit message for transaction handled by TCAP B Message received for transaction handled by TCAP B Figure 14 Message
11. the other as SIUB Under normal operation the application uses both the resources of SIUA and SIUB see Figure 5 The distributed layer 4 management is achieved using a LAN connection and allows SS7 messages for any trans action or call to be received by either unit regardless of the unit that is actually processing the call or transaction The distributed MTP3 functionality is achieved using a specially configured inter SIU link set containing one or more signaling links Transmit messages from each SIU are load shared between links that connect to the local SIU if these are available If all local network facing SS7 links have failed transmit messages are relayed to the Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note A Normal routing case Single Point Code Inter SIU Link Set Link Set id 0 z777 B Routing under network link failure Single Point Code Inter SIU Link Set lt t Link Setid 0 27 p 1 1 1 1 1 I 1 I t ro My Yo vi JV Link Set id 1 eo 1 1 1 i 1 l I 1 I I I I I Link Set id 1 Li Figure 6 Transmit Routing to a Single Destination partner SIU across the inter SIU link set and sent out to the adjacent signaling point by the partner unit The inter SIU link set also provides the capability of message retrieval and retra
12. Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Intel in Communications Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note Table of Contents Abstract 1 Introduction 1 Overview of SIU Operation 2 Circuit switched API Operation 2 Transaction based API Operation 3 Management Interface 3 Potential Points of Failure 3 Failure of SS7 Links 4 Failure of Routes 5 Failure of Power Supply 6 Failure of Signaling Interface Unit 6 Routing Architectures of a Dual resilient SIU System 7 Dual SIU architecture for Circuit switched Applications 10 Dual SIU architecture for Transaction based Applications 13 Failure of IP Subnetwork 15 Failure of Application 15 Configuring a Dual SIU Pair 17 Hardware Requirements 17 System Configuration 18 Changes to the config txt Parameter File 18 Configuring the Inter SIU Link 18 Routing Configuration 19 Circuit Group Configuration 19 Example Configuration 19 Run time Operations of a Dual resilient SIU System 20 Connecting a Host to Two SIUs 20 Communicating with Both SIUA and SIUB 21 Transferring Control of a Circuit Group between SIUs 21 Activating and Deactivating Circuit Groups 21 System Initialization 21 Failure Detection 21 Transferring the Circuit Group 22 Re synchronization of the Circuit Sate Information 22 Recovery of the Failed Unit 23 Transferring Cont
13. Flow on a Dual resilient System Running the SS7 Stack up to TCAP In the second case each unit controls half of the total available transactions The Intel NetStructure SIU520 SS7 signaling gateway supports up to 16 384 transac tions A dual resilient system can consequently handle up to 32 768 simultaneous transactions Each transaction is processed for its entire duration by the SIU that processed the first TCAP message The user application must therefore direct all messages for a transaction to the same SIU and load balance outgoing dialogues between the two units An incoming TCAP dialogue mes sage other than BEGIN or QUERY is handled by the SIU that processed the first TCAP message for that dialogue received from the SS7 network When an SIU receives a TCAP message that belongs to a transaction that was initiated on the other unit it will pass this message to its peer SIU over the RSI connection This is shown in 14 Figure 14 Failure of an SIU reduces the number of avail able transactions to one half In a dual resilient transaction based SIU system running the SS7 stack up to SCCP on the SIU and TCAP and above on the application host each host controls a fixed number of transactions Each transaction is processed for its entire duration by the application host that processed the first TCAP message Upon failure of one SIU unit the TCAP capacity and ongoing transaction are totally unaffected The architectural decision
14. SIVA MTP CONFIG 0 0 0x0000 MTP LINKSET 0 100 1 0x8000 100 0x8 MTP LINKSET 1 200 1 0x0000 100 0x8 MTP LINK 000 O 1 1 1 1 0 0x4006 MTP LINK 110012 1 2 16 0x0006 MTP ROUTE 100 0 0x0020 MTP ROUTE 200 1 0x0020 0x0001 0 For SIUB MTP CONFIG 0 0 0x0000 z P LINKSET 0 100 1 0x8000 100 0x8 P LINKSET 1 200 1 0x0000 100 0x8 O 1 1 1 1 0 0x6006 1 1 2 1 2 16 0x0006 100 0 0x0020 200 1 0x0020 0x0001 0 z zZ z a AHAHAHAHAHH gel E Ei a P ROUT P ROUT K P LINK T T m F py m F P M up_enable was set for ISUP user part SI 5 for the example above 19 Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Single Point Code Inter SIU Link Set Link Set id O 277 Point Code 300 Link Set id 1 Link Set id 1 Point Code 400 li li link_id 1 slc 0 Point Code 600 Point Code 500 Figure 20 Example Configuration to an Adjacent STP Pair For an SIU pair connected to a mated STP pair carrying the inter SIU link over the second E 1 port of the first signaling card the configuration Figure 20 would be For SIVA MTP CONFIG 0 0 0x0000 MTP LINKSET 0 300 1 0x8000 300 0x8 MTP LINKSET 1 400 1 0x0000 300 0x8 MTP LINK 0000414111 0 0x4006 MTP LINK 1 1 0 0 1 2 1 2 16 0x0006 MTP ROUTE 300 0 0x0020 MTP ROUTE 400 1 0x0020 0x0001
15. ation channel via TCP IP Ethernet to the host processors and reports status information to an application process running on a user defined host The host elected to receive management messages can be selected by sending an API MSG COMMAND management request See the Intel NetStructure SIU520 Developer s Manual for more information Host O is used by default Potential Points of Failure In this section the most critical points of failure of an Intel NetStructure SIU520 SS7 signaling gateway based sys tem are reviewed The list of potential points of failure include SS7 links SS7 routes Power supply E Signaling interface unit P subnetwork Application host For each of these points of failure a solution is provided and implementation details are given Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway A Load sharing between link 0 and link 1 under normal conditions j j s MM a ce SIU520 Pd Link id 0 slc 0 I p Link id 1 slc 1 gg II IO SIC Te oo o Point Code u 0x200 Link Set id 0 e my toj E g I Point Code 1 i 0x100 vie B Traffic sent over link 1 under failure of link O my my my l oi ANE 1 SIU520 i Point Code 0x100 j Dp l Point Code V 0x200 Figure 3 SIU Connected to Adjacent Node with Two Links in Link Set Failure of SS7 Links Link failure management
16. ble at http resource intel com telecom support ss7 cd Genericlnfo GeneralDocumentation U24SSS02 DTS UG pdf Appendix C Abbreviations API Application programming interface CIC Circuit identification code DPC Destination point code DTC Distributed transaction client DTS Distributed transaction server LAN Local area network MMI Man machine interface PCM Pulse code modulation SIU Signaling interface unit SS7 Signaling system 7 To learn more visit our site on the World Wide Web at http www intel com 1515 Route Ten Parsippany NJ 07054 Phone 1 973 993 3000 INFORMATION IN THIS DOCUMENT IS PROVIDED IN CONNECTION WITH INTEL PRODUCTS NO LICENSE EXPRESS OR IMPLIED BY ESTOPPEL OR OTHERWISE TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT EXCEPT AS PROVIDED IN INTEL S TERMS AND CONDITIONS OF SALES FOR SUCH PRODUCTS INTEL ASSUMES NO LIABILITY WHAT SOEVER AND INTEL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO SALE AND OR USE OF INTEL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE MERCHANTABILITY OR INFRIGE MENT OF ANY PATENT COPYRIGHT OR ANY OTHER INTELLECTUAL PROPERTY RIGHT Performance tests and ratings are measured using specific computer systems and or components and reflect the approximate perfor mance of Intel products as measured by those tests Any difference in system hardware or software design or configuration may affect actual performance Buye
17. cally routed to the adjacent signaling point through the inter SIU link set as shown in Figure 11 The application should continue to use the SIU as before directing all outgoing circuit requests to SIUA Outgoing calls in a set up state during the transfer should be re attempted Incoming calls being set up by the interconnected SS7 If the controlling SIU fails the application is informed of Seppe S A A led the failure and should transfer control of the circuit group to the remaining unit remotely 11 Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Adjacent Signaling Point TCP IP Ethernet Application Circuit Group 0 Active Circuit Group 1 Active Figure 12 Routing Following Failure of SIUA The circuit group control will then appear as shown in Figure 12 The user application software should reset all idle circuits following a transfer and reset all remaining circuits as they become idle When the failed unit recovers control of the circuits may be transferred back by the application Circuit group control is transferred by the application in 12 two stages The group should be deactivated from one unit if Communication with that unit is possible before being activated on the partner SIU To protect against control being active on both units at the same time the SIU automatically issues a deactivate command to the
18. djacent SSP SCP 19 Figure 20 Example Configuration to an Adjacent STP Pair 20 Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note Abstract In order to achieve five nines 99 999 reliability and a high degree of fault tolerance in an SS7 environment using Intel NetStructure SIU520 signaling gateways an SS7 end point spread over two signaling interface units SIUs and multiple application servers can be configured and deployed Splitting the protocol processing functionality of a signaling point by implementing an SS7 node over two SlUs isolates the hardware processors on the chassis from each other This separation lets one processor continue if the other fails allowing the system to remain in service Distributing application processing of a signaling point on multiple application servers not only increases the total capacity of a system but also offers a higher level of fault tolerance in the user application space Intel NetStructure SS7 products are designed for this dual processor approach and provide the architecture for splitting a point code over two active SS7 protocol engines Using this technique the links in an SS7 link set can be spread between two separate chassis when Intel NetStructure SS7 boards are installed in each This document describes the features of the SIU520 SS7 signaling gateway that are available to build SS7 solutions and reach the
19. five nines requirements of telco grade service platforms Introduction This application note describes the architecture of the Intel NetStructure SIU520 signaling gateway reviews the most common potential points of failure of an SS7 system based on this product and explains methods that can mitigate each of these potential failure points This document also explains in detail the configuration and run time operation considerations of a dual resilient SIU520 based system Because of the high expectation of service reliability by the users of public telephone networks equipment manufacturers and system integrators demand high levels of fault tolerance and availability often citing the five nines for availability requiring a system to be operational for 99 999 of the time These systems need to continue to offer service even when partial hardware or software failure has occurred There are several well known methods of achieving this type of reaction to partial failure in the signaling component of communications networks including Multiple signaling paths SS7 links and link sets to each end point Distribution of these paths through independent inter faces and cabling m Distribution of the processing of SS7 terminations at a single signaling point between multiple processing cards in a single SIU Physical isolation and duplication of the SS7 interface for a single signaling point on independent protocol engines
20. hese links will be used for outgoing traffic only they can be used at a higher capacity than network facing links Moreover since only half of the traffic can potentially be routed through that link set a common rule is to allocate a fourth of the total number of network facing links in the inter SIU link set In a fully populated pair of SIU520 12 links per unit 24 links total 16 links will be typically allocated in the network facing link set and four links will be allocated in the inter SIU link set Routes to destinations are configured such that there is a primary link set the link set from the SIU to the DPC and a secondary link set the inter SIU link set which is used only when the primary link set has failed Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Single Point Code Inter SIU Link Set Link Set id O Zz gt Link Set id 1 A Links Link Set id 2 I I Figure 7 Dual resilient SIUs Connected to a Mated STP Pair in a Straight Link Configuration Single Point Code Inter SIU Link Set Link Setid O Z777 Figure 8 Dual resilient SIUs Connected to a Mated STP Pair in a Crossed Link Configuration In case A since the F links all exist in the same link set messages may be sent from the adjacent SSP SCP to either SIVA or SIUB If an SIU receives a message from the SS7 network for a circuit o
21. immediately following restoration of the communication with the SIU 23 Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Appendix A Frequently Asked Questions Q How can tell if an SIU fails A The status of the communication between the host and the SIU is indicated by RSILMSG_STATUS messages Q What happens if an SS7 message for a circuit or transaction is received by an SIU that does not control that circuit or transaction A The message is automatically passed to the partner SIU using the TCP IP LAN Q If a single SS7 link to the network fails on one of my SIUs does my application need to take any action A No If there are other links remaining on that unit the traffic will changeover to one of these otherwise the traffic will be automatically passed to the other unit via the inter SIU SS7 link set Q If all of the SS7 links to one of the SIUs fails do need to take any action A No The SIU will automatically re route transmit traffic via the inter SIU SS7 link set If an SIU fails do need to take any action A Yes For switched circuit applications the circuit groups controlled by the failed unit should be activated on the remaining unit Further information may be found in the nte NetStructure S U520 Developer s Manual Q What happens if an inter SIU SS7 link fails A The SIU will changeover to use other SS7 links i
22. inks as shown in Figure 9 Again a common practice is to allocate a fourth of the total number of network facing links in the inter SIU link set Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note A Normal routing case both network link sets available Single Point Code Link Set id 1 Deep Inter SIU Link Set Link Set id 0 EE Link Set id 2 B Routing under failure of network link set between SIUA and adjacent STP Single Point Code Link Set id 1 ry my Inter SIU Link Set q e Link Set id 0 2777 B Transmit Traffic from SIUA Transmit Traffic from SIUB Figure 9 Transmit Routing Through Mated STPs Table 1 compares the advantages and disadvantages of these methods Table 1 Comparison of a Straight Link Configuration vs a Crossed Link Configuration Comparison Subject Straight Configuration Crossed Configuration Load sharing STPA can only load share traffic Each STP can load share between the two SIUs for SIUA and vice versa optimizing the resource utilization Network facing links failure SIUA can rely on SIUB to send When an SIU loses its network facing links the outgoing traffic upon failure of its application must activate circuit groups on the entire network facing links surviving SIU for ISUP based application Inter SIU link set dimensioning Need to allocate 1 4
23. is a standard MTP3 operation Problem With a single link to the adjacent signaling and is not an SIU520 specific feature In other words point service is disrupted if the link goes down for some failure between links in a same link set will happen in a reason i e layer 1 alarm congestion completely transparent way for the user application Details In an SIU520 system configuration two commands are used in config txt to configure link sets and links MTP_LINKSET and MTP_LINK In this example two SS7 links are defined between local point code 0x100 and adjacent point code 0x200 on time slot 16 of PCM ports 1 and 2 Also see Figure 3 Solution Link resiliency is achieved by using multiple links between a local point code and an adjacent point code By definition such links are said to belong to the same link set which can contain up to 16 links Ideally the links of a link set should not be carried over a unique physical medium such as an E 1 or T 1 trunk but instead should be split over independent physical trunks MINE INS lt lalmikesere ae lt eichjeceime spe lt intim linke lt itllegs gt lt local spe gt lt 567 gt MTP LINKSET 0x200 2 00000 0Ox100 0x08 MINE LINK lt link sich lt ilimksee ich lt link tret gt lt sle lt bpos gt lt slink gt lt lppos2 gt lt stream gt lt timeslot gt lt flags gt MIP LINK 0 0 16 0x0006 Me INg L i 1 id Of 16 00006
24. k on the affected host detects the loss of communication and issues an RSI_LMSG_LINK_STATUS API message with a status value set to 2 link to SIU lost to a destination task 21 Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway conc_id on the host conc_id is set when the RSI link was started optionally by rsicmd This message will only be received by the application if the RSI link is con figured with the conc_id set to the application s module ID At the same time the affected SIU if it can will issue an API_MSG_SIU_STATUS message with status value 30 decimal indicating a host link failure on the specified host ID This message is sent to the host configured to receive management messages host O by default There are two failure modes that can cause loss of communication Complete failure of one SIU in a dual resilient pair Partial TCP IP failure causing loss of communication between the host and one SIU of the pair via the TCP IP LAN From the application s point of view there is no difference in these cases since the RSI link fails in either case From a system point of view the main difference is that in the second case the inter SIU communication may still be functioning If the affected SIU loses communication with all of its hosts it automatically deactivates all SS7 signaling links preventing any messages from being processed by any
25. mber does not depend on the number of hosts 15 Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Host 0 Host 1 Host 2 Host 3 Application Application Application Application Ethernet SIU520 i b E i i I I L I Per iy I I nnanponun 1 Figure 16 TCAP Dialogue Groups Example TCAP Resiliency Based on DTS DTC Option each application host Consequently the total capacity of Alternatively it is possible to distribute SCCP traffic to such a system depends on the number of application multiple application hosts using the distributed transac hosts each host bringing an increment of 65 536 tion server distributed transaction client DTS DTC soft simultaneous dialogues Please refer to the Intel ware option as shown on Part B of Figure 13 In this NetStructure SS7 Protocols DTS User Guide Issue 2 architecture TCAP and potential application parts run on for more information on the DTS DTC software option 16 Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note Signaling Card Signaling Card PCM Trunk 0 PCM Trunk 1 PCM Trunk 2 PCM Trunk 3 Figure 17 Inter SIU Link over Crossed E 1 T 1 Cable Configuring a Dual SIU Pair To create a dual resilient configuration for the Intel NetStructure SIU520 SS7 signaling gateway modifications are required t
26. n the inter SIU link set Q What happens if the Ethernet interfaces fail on an SIU A This will cause failure of all of the connections between the hosts and the SIU The SIU will react by deactivating all connected SS7 links preventing any more signaling information from being received from the SS7 network The host applications will receive an indication indicating failure of the SIU and should transfer any circuit groups controlled by this SIU to the remaining unit the effective result being as though the complete unit had failed 24 Q Do need to activate circuit groups on a single SIU configuration A No Q How many links should I configure in the inter SIU link set A The inter SIU link set should have sufficient capacity to enable it to carry the maximum traffic exchanged between a single SIU and the adjacent signaling point To eliminate single points of failure more than one link may be configured in the link set each link connecting to a different signaling card Appendix B For More Information Inte NetStructure S IU520 Developer s Manual Issue 2 available at http resource intel com telecom support ss7 siu520 u06siu02 pdf Inte NetStructure S U520 Intel NetStructure SG430 Hardware User Manual Issue 3 available at http resource intel com telecom support ss7 CD ProductSpecific SG430 HardwareUserManual U05SIU03 pdf Inte NetStructure SS7 Protocols DTS User Guide Issue 2 availa
27. ns stable The circuit groups may then be transferred after this timeout if the communication to the secondary unit remains active Re synchronization of Circuit State Information Once the circuit group activation s are acknowledged from the secondary SIU the application needs to resynchronize the circuit state information based on the application s knowledge of the current circuit state This is achieved by sending three CGSC requests to the secondary SIU Circuits that were in a call set up state or idle i e any circuit that was not in the steady state speech or answered state should be RESET Circuits that were in the speech stage of an incoming call should be forced to INCOMING ACTIVE circuits that were in the speech state of an outgoing call should be forced to OUTGOING ACTIVE The forcing of the circuit state to either INCOMING ACTIVE or OUTOING ACTIVE is achieved using the CGSC Request API message with ptype set to 14 decimal for INCOMING ACTIVE and 15 decimal for OUTGOING ACTIVE Calls that were in outgoing set up prior to the transfer should be re attempted following successful completion of the transfer The application should be able to re attempt a failed outgoing call attempt as this may occur under normal operating conditions The originating switch will automatically reattempt calls that were in incoming set up When these commands are acknowledged the application may resume normal call activity
28. nsmission when a changeover operation occurs between the two units For circuit switched applications the circuit groups are configured on both units letting the application select which SIU controls each group In normal operation the control of circuit groups is distributed between both the SIUA and SIUB In the event of failure of a unit or for maintenance the application can move control of each circuit group from one SIU to the other For transaction based applications the transactions are shared equally between the two units Routing Architectures of a Dual resilient SIU System The routing options i e straight connection to the DPC vs indirect connection via a pair of STPs described in this section will vary based on the actual network architec ture that is being supported for a particular application Connection to a Single Adjacent Signaling Point Figure 6 shows two possible routing alternatives for SIUA routing to an adjacent SSP or SCP Messages issued from SIVA are sent to the destination SSP or SCP using local SS7 links if available If these fail transmit messages are relayed through SIUB over the inter SIU links In this case the DPC is also the adjacent signaling point Although Figure 6 shows an SIU pair connected to a sin gle adjacent signaling point the pair may be connected to multiple destinations The number of links allocated in the inter SIU link set has to be carefully calculated Since t
29. o both the system configuration done using the man machine interface MMI and the protocol configuration in the config txt parameter file This may be done remotely and trans ferred to the SIU using FTP More details may be found in the Intel NetStructure SIU520 Developer s Manual een SS7 Network E 1 Trunk Containing SS7 Signaling Only jeenenneneenenen F gt Inter SIU SS7 Link Set E 1 Trunk sennen SS7 Network E 1 Trunk Containing SS7 Signaling Only 1 1 nnnnnndann nunnnnannnnnnnnnnnnnnnnn al Hardware Requirements Configuring an SIU as one half of a resilient pair requires additional hardware ports to carry the inter SIU link set between SIUA and SIUB This may be achieved using E 1 T 1 interfaces as shown in Figure 17 or V 11 V 35 interfaces as shown in Figure 18 A cable part number 842484 can be purchased from your Intel distributor to interconnect two V 11 ports between signaling cards within the SIU For more information refer to the nte NetStructure SIU520 Developer s Manual 17 Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Signaling Card Voice Processing Platform Signaling Card SS7 Network nunnnnnnnnnnnnnnnn BE 1 or T 1 Trunk Containing SS7 Signaling and Voice Circuits TT Inter SIU SS7 Link Set 4 a SS7 Network E LLTI nuannnnnnnnjannnnn aj E
30. of all Need to allocate a single link maximizing the network facing links e g 16 number of network facing links e g 22 network facing network facing links and four links and one inter SIU link Allocating a single link means inter SIU links there are two single points of failure in the system For best resilience the inter SIU link set should contain two links spread across two cards in each SIU Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Circuit Group 0 Active Circuit Group 1 Inactive Adjacent Signaling Po a Inter SIU SS7 Link Set Application TCP IP Ethernet Circuit Group 0 Inactive Circuit Group 1 Active Transmit traffic for circuits active on SIUA Received traffic for circuits active on SIUA Figure 10 Normal Routing for Circuit Group 0 When Controlled by SIUA Dual SIU Architecture for Circuit Switched Applications Within the SIU environment circuits are configured in groups each group equating to all the circuits multiplexed onto a single E 1 or T 1 PCM trunk The SIU provides the SS7 circuit control and the application platform or host terminates the physical channels typically with a voice processor For normal operation half the circuit groups are controlled by SIUA and half by SIUB As each application platform starts up and connects to both SIVA and SIUB
31. on has been received by the application all affected circuits should be reset This will force the circuits to a known idle state and remove the blocking status When the reset is acknowledged from the terminating switch by receipt of a circuit group supervision control confirmation message the application may begin exchanging call traffic with the SIU Circuit Group Conflict Both SlUs in a dual resilient configuration periodically poll each other to determine which circuit groups are active on each unit If a group is active on both units at the same time an APIMSG_USER_EVENT message is issued by the unit that detects the conflict indicating the group ID of the affected circuit group The controlling application host should issue a deactivate command to the SIU that should not be controlling the circuit group and re synchronize the circuits in the group on the correct SIU by issuing a reset The SlUs prevent this situation from arising by automatically sending a deactivate circuit group command to the other unit on receipt of the activate command If the nature of the failure is such that inter SIU communication is lost it may be impossible for the SIU to issue the automatic deactivate command Under this circumstance when the failed SIU recovers Circuit groups may be active from the time before the initial failure This situation is handled by the application sending a deactivate command for all of the previously active groups
32. or T 1 Trunk Containing SS7 Signaling and Voice Circuits Figure 18 Inter SIU Link Set over V 11 The inter SIU signaling link set can be configured to use any signaling processor on any signaling card and may be carried on any of the available interfaces on the signaling card If V 11 interfaces are used to carry the SS7 signaling between the SIU and the network this is typically the case in North America it is possible that there will be free E 1 T 1 PCM ports on signaling cards These may be used for the inter SIU signaling System Configuration The system assignment of SIVA or SIUB is made by typ ing one of these commands CNSYS MODE SIUA or CNSYS MODE SIUB The current assignment may be displayed by typing CNSYP 18 Changes to the config txt Parameter File Each SIU is configured individually The config txt parameter file held on each unit reflects the configuration view of the local unit only hence assignments of link set and link identities are only unique within a single unit For the dual configuration it is necessary to modify the protocol configuration file config txt to assign one unit as SIUA and the other as SIUB using the SIU_INSTANCE command The IP address of the other SIU must also be declared using the SIU_REM ADDR command Configuring the Inter SIU Link The inter SIU link set should be defined on both units using the MTP_LINKSET command with bit 15 of the lt flags gt parameter
33. pplication Note Communicating with Both SIUA and SIUB The user application exchanges information with the SIU via API messages MSG In a dual SIU environment each time the user application sends a message to the SIU this should be directed to either SIUA or SIUB using a library function GCT_set_instance In the receive direction the application can determine the SIU that sent a MSG using the library function GCT_get_instance Function definitions may be found in the header file sysgct h GCT_set_instance int GCT_set_instance unsigned int instance HDR h This function sets the destination instance number SIU identity or siu_id prior to sending a message and returns O on success non zero otherwise currently no failure conditions are defined SIUA is instance O and SIUB is instance 1 assigned by the siu_id parameter provided to the rsicmd utility This function should be called immediately before GCT_send GCT_get_instance unsigned int GCT_ get instance HDR h This function returns the instance number SIU identity or siu_id after receiving a message The parameter h is a pointer to the HDR structure at the start of the received MSG The returned value will be either O or 1 SIUA is instance O and SIUB is instance 1 as assigned by the siu_id parameter provided to the rsicmd utility Transferring Control of a Circuit Group between SIUs Activating and Deactivating Circuit Groups Configuration commands for all ci
34. r transaction that it does not control this receive message is passed automatically to the other SIU for processing via the TCP IP LAN Connection to an Adjacent Mated STP Pair There are two ways of connecting a pair of SIUs to a mated STP pair In the first method the straight link configuration each SIU is configured with two link sets one link set containing STP facing links plus the inter SIU link set The straight link configuration consists in connecting SIUA to STPA and SIUB to STPB as shown in Figure 7 The second method the crossed link configuration consists of adding crossed link connections between SIVA and STPB and between SIUB and STPA to the previous mode In a crossed link configuration each SIU is configured with three linksets two link sets containing the links towards each STP plus the inter SIU link set see Figure 8 The configuration of the DPC will contain the link set IDs of the two link sets connected to the STPs Load sharing can be enabled to take advantage of all the system resources In such a configuration the inter SIU link set is not used for traffic failover but only for synchronization of network management messages Consequently a single link within this link set is fairly enough giving an increased bandwidth for network facing links The inter SIU link must be carefully dimensioned as it will have to support the outgoing traffic of the SIU that would have lost its entire network facing l
35. rcuit groups must be present on both SlUs At run time the application running on each host should select which SIU is currently in con trol of each group by activating and deactivating groups on a particular SIU Circuit groups are activated and deactivated using the API_MSG_COMMAND message type 0x7 0f with a cmd_type of 8 to activate a group and a cmd_type of 9 to deactivate a group The format of this message is detailed in the Intel NetStructure SIU520 Developer s Manual This message should be issued with a request for a response an acknowledgement this will be returned to the requesting application with a status value of zero indicating success or non zero values indicat ing busy or failure System Initialization When the system starts up the host establishes communication with both SIUA and SIUB either by using the rsicmd utility or by issuing RSI configuration API messages directly from within the application When the communication between the host and the SIU is established the RSI task on the host issues an RSI_LMSG_LINK_STATUS API message with a status value set to 1 link to SIU recovered to a destination task conc_id on the host conc_id is set when the RSI link was started This message will only be received by the application if the RSI link is configured with the conc_id set to the application s module ID The ID field of this message is set to O to indicate SIUA and 1 to
36. remaining active circuit groups Transferring the Circuit Group If any of the circuit groups terminating on the host are currently active on the affected SIU the host application must transfer control of each affected circuit group from the failed SIU the primary SIU to the remaining SIU the secondary SIU Transferring a circuit group normally involves deactivating the group on the controlling SIU then reactivating it on the other However since the host is unable to communicate with the failed SIU the application is only required to send an API_LMSG_COMMAND message to the secondary SIU with cmd_type of 8 activate circuit group for each affected group The activate circuit group command should be issued with a request for a response and the application should not send any call processing or circuit management commands until the response acknowledgement has been received from the secondary SIU The SIU processes single commands in sequence 22 therefore if an activate command is received while a previous command is executing the response will be received with a non zero status in this case a value of 4 indicating equipment busy The application should reattempt the activate command on receipt of a response indicating busy Since the failure may affect SIUA and SIUB the host may choose to wait for a period of time following notification of the failure to determine if communication with the other unit remai
37. rol Back 23 Circuit Group Conflict 23 Appendix A Frequently Asked Questions 24 Appendix B For More Information 24 Appendix C Abbreviations 24 Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Table of Figures Figure 1 Structure of the Intel NetStructure SIU520 SS7 Signaling Gateway Figure 2 Integrating the SIU520 Figure 3 SIU Connected to Adjacent Node with Two Links in Link Set Figure 4 SIU520 Connected to Mated STP Pair Providing Route Resiliency Figure 5 Dual SIU Architecture Figure 6 Transmit Routing to a Single Destination oo N o OQO DN Figure 7 Dual resilient SIUs Connected to a Mated STP Pair in a Straight Line Configuration Figure 8 Dual resilient SIUs Connected to a Mated STP Pair in a Crossed Link 8 Configuration Figure 9 Transmit Routing Through Mated STPs 9 Figure 10 Normal Routing for Circuit Group 0 When Controlled by SIUA 10 Figure 11 Routing When All Local Links Have Failed Group 0 Controlled by SIUA 11 Figure 12 Routing Following Failure of SIUA 12 Figure 13 Two Different Architectures for a TCAP Processing SIU System 13 Figure 14 Message Flow on a Dual resilient System Running 14 the SS7 Stack up to TCAP Figure 15 Dual LAN Operation on the SIU520 15 Figure 16 TCAP Dialogue Groups Example 16 Figure 17 Inter SIU Link over Crossed E 1 T 1 Cable 17 Figure 18 Inter SIU Link Set over V 11 18 Figure 19 Example Configuration to an A
38. rs should consult other sources of information to evaluate the performance of systems or components they are considering purchasing For more information on performance tests and on the performance of Intel products reference www intel com go telecom or call U S 1 800 628 8686 or 1 916 356 3104 The Intel products referred to in this document are intended for standard commercial use only Customer is solely responsible for assessing the suitability of the product for use in particular applications Intel may make changes to specifications product descriptions and plans at any time without notice Other names and brands may be claimed as the property of others Intel Intel NetStructure and the Intel logo are trademarks or registered trademarks of Intel Corporation or its subsidiaries in the United States and other countries Copyright 2004 Intel Corporation Printed in the USA Copyright 2004 Intel Corporation All rights reserved Printed on recycled paper 08 04 00 9206 001
39. set to 1 This link set must have the same value defined for the lt local_spe gt and lt adjacent_spc gt values this will be the local point code of the SIU pair Links are added to the inter SIU link set Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note Single Point Code Inter SIU Link Set Link Set id 0 277 Link_id 0 sic 0 Point Code 100 Link id 1 slc 0 Link id 1 slc 1 Point Code 200 Link Set id 1 Figure 19 Example Configuration to an Adjacent SSP SCP using the MTP_ LINK command assigning incrementing lt link_ref gt and lt slc gt values as normal The lt bpos gt and lt blink gt parameters define which SS7 processor there are three on each signaling card manages each link If a V 11 port is being used lt blink gt must be either Tor 2 For a link using a PCM port the physical location of the link is specified by setting stream and timeslot stream 16 is the PCM port closest to the green LED on the signaling card stream 17 the lower PCM port To use a serial link the MTP_LINK lt flags gt bit 14 should be set to 1 lt stream gt and lt timeslot gt both to 0 One of the units should act as the V 11 port clock master the other as slave hence one SIU must also have lt flags gt bit 13 set to 1 For example to configure an inter SIU link on linkset_id O to use V 11 port A on the first board in a SIU520
40. sharing a single point code Splitting the functionality of the application layer between multiple application servers The first method can be achieved by implementing multi ple links 64 Kb s or 56 Kb s channels between two adjacent inter communicating points By definition these links will all be in the same link set The last two can be accomplished by using two independent but co operat ing SIU520s relaying the SS7 signaling to a distributed application layer split over multiple application hosts Note Readers should be familiar with Signaling System 7 SS7 concepts They should also be aware that the information contained in this application note is provided as a complement to the Intel NetStructure SIU520 Developer s Manual hence an understanding of the terms defined in the developer s manual is assumed Application Note Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Application Application 0 1 N API Layer Ethernet Driver MAP or INAP or IS41 Configuration and Management MTP ae Le 1 3 SIU 520 Figure 1 Structure of the Intel NetStructure SIU520 SS7 Signaling Gateway Overview of SIU Operation The Intel NetStructure SIU520 SS7 signaling gateway is an SS7 network access product that provides a resilient interface to SS7 networks via a TCP IP local area net work LAN As shown in Figure 1 SIU520 software
41. taken on where the TCAP module is running also has consequences on the level of application resiliency and total system capacity These consequences are explained in more details in Failure of Application pg 15 Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note Application Application Host SIU520 Figure 15 Dual LAN Operation on the SIU520 Failure of IP Subnetwork Problem Should one subnetwork go down due to a network component failure the hosts connected to the SIU over the other subnetworks will remain active and attempt to preserve half of the total system capacity Solution There are two Ethernet ports on the SIU520 This allows splitting the IP connections between the SIU and the application hosts onto two physically separated subnetworks as shown in Figure 15 This eliminates the risk of losing all IP connectivity in the event of a switch router hub failure in the LAN Details Failure of Application below shows how to take advantage of the dynamic configuration features offered by the SIU520 to failover the affected application hosts to the surviving subnetwork Failure of Application Problem The failure of an application host leads to the loss of a portion of system resources Solution The most basic feature ensuring this is that the application can be deployed on multiple hosts In a software release bigger
42. tes transparently over TCP IP Ethernet using software modules provided by Intel For circuit switched telephony applications each application platform termi nates and hence controls a fixed range of physical cir cuits or circuit identification codes CICs ClCs are con figured in groups of up to 32 each group normally equating to all the circuits in a single E 1 or T 1 trunk Each group is terminated on a fixed application platform or host processor enabling the SIU to automatically direct API messages to the correct platform Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note CT Application Platform E 1 or T 1 Trunks Voice Circuits Only SIU520 E 1 or T 1 Trunks with SS7 Channel SS7 and Voice Circuits Information Ethernet Figure 2 Integrating the SIU520 Transaction based API Operation TCAP based applications can be distributed on multiple application hosts using two different methods which are explained in details further in this document see Failure of Applications pg 15 These methods imply running TC user application parts such as GSM MAP INAP or IS 41 on each application host When running any application part above TCAP on the SIU520 itself the product allows operation of a single host application Management Interface The SIU520 constantly monitors the state of its physical connections PCM trunk inputs the communic
43. than v1 06 the SIU520 supports up to 64 hosts For circuit switched applications failure of a host generally means loss of the physical trunk interface hence there is no need of transferring the logic to other Surviving hosts More sophisticated features are available to allow TCAP based applications to failover to other hosts Details For TCAP based applications the SIU allows operation of multiple application hosts interfacing directly to TCAP hence giving a certain level of resiliency in the user application space Two methods are available for this purpose and are explained here TCAP Resiliency Based on Dialogue Groups Fixed ranges of TCAP dialogues can be created in the SIU520 configuration file and assigned to different application hosts TCAP dialogue groups are defined using the TCAP_ CFG DGRP command in config txt More information about this command can be found in the Intel NetStructure SIU520 Developer s Manual The application program running on each host must therefore ensure that only dialogue identifiers from the assigned range are used Optionally a TCAP user layer such as MAP INAP or IS41 can run on each application host to provide some application part functionalities Figure 16 describes such a distributed architecture where TCAP transactions are handled by four different hosts each of them running MAP and a MAP application The total number of TCAP dialogues for the whole system is 16 384 and this nu
44. the application must nominate which SIU is to control the 10 signaling for each of the circuit groups it terminates A Circuit group activation command must be sent to the selected SIU for each circuit group Any outgoing messages for circuits in this group must be sent to this SIU as shown in Figure 10 The adjacent signaling point views the links connected to SIVA and SIUB as the same link set and as such is free to send messages for the circuits controlled by SIVA to either unit In the case where SIUB receives a message for a circuit controlled by SIUA the message is automatically routed to the correct controlling circuit group using the LAN Ethernet connection shown by the shaded arrows in Figure 10 Building Fault tolerant SS7 Systems Using the Intel NetStructure SIU520 SS7 Signaling Gateway Application Note Circuit Group 0 Active Circuit Group 1 Inactive Adjacent Signaling ee i s salad Inter SIU SS7 Link Set Application TCP IP Ethernet Circuit Group 0 Inactive Circuit Group 1 Active B Transmit traffic for circuits active on SIUA Received traffic for circuits active on SIUA Figure 11 Routing When All Local Links Have Failed Group O Controlled by SIUA If all the links between the controlling SIU and the Calls in a steady state speech will continue uninter adjacent signaling point fail all transmit traffic is rupted automati
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