Avaya Configuring Data Compression Services User's Manual
Contents
1. xvii Configuring Data Compression Services Ordering Bay Networks Publications Acronyms To purchase additional copies of this document or other Bay Networks publications order by part number from Bay Networks Press at the following numbers You may also request a free catalog of Bay Networks Press product publications Phone 1 800 845 9523 FAX U S Canada 1 800 582 8000 FAX International 1 916 939 1010 CCP Compression Control Protocol CPC Continuous Packet Compression CRC Cyclic Redundancy Check DDN Defense Data Network ILI intelligent link interface LCP Link Control Protocol MIB Management Information Base NCP Network Control Protocol PDN Public Data Network PPC Packet by Packet Compression PPP Point to Point Protocol PTOP Point to Point Protocol proprietary to Bay Networks PVC permanent virtual circuit RFC Request for Comment VC virtual circuit WAN wide area network WCP compression protocol proprietary to Bay Networks xviii Chapter 1 Data Compression Overview Bay Networks data compression services enable you to reduce line costs and improve response times over wide area networks Our data compression eliminates redundancies in data streams When you use compression on your network bandwidth efficiency improves and you can transmit more data over a given amount of network bandwidth Our compression services include e Software based compression for Frame Relay Point to Point2. Continuous Packet compression There is no limit to the number of VCs that can use this one PPC context The compression hardware uses memory in units called pages where a page equals 32 KB of memory Each context that uses a 32 KB history uses one page of memory Restrictions for CPC contexts using either 8 or 32 KB histories are that the memory used for any one history must be continuous and it may not cross pages For 8 KB contexts these restrictions create few constraints but for 32 KB contexts they are significant 1 8 Data Compression Overview Thirty one CPC contexts each using an 8 KB history are possible on the 32 context board and 127 contexts each using an 8 KB history are possible on the 128 context board Table 1 1 indicates the maximum number of 8 KB contexts each board can support Table 1 1 Hardware Compression 8 KB Contexts Max 8 KB CPC Available 32 KB Reserved 8 KB Contexts CPC Contexts PPC Context 32 Context Board 31 0 1 128 Context Board 127 0 1 On a 32 context board the maximum number of 32 KB contexts is 7 and on a 128 context board the maximum number of 32 KB contexts is 31 because of the 8 KB of memory the one PPC context requires Table 1 2 summarizes this information Table 1 2 Hardware Compression 32 KB Contexts Max 32 KB CPC Available 8 KB Reserved 8 KB PPC Contexts CPC Contexts Context 32 Context Board 7 3 1 128 Context Board 31 3 1 You can use a mix of
3. 2 Compression Mode Continuous Packet Continuous Packet Packet by Packet Indicates the compression mode on the line Continuous Packet Compression CPC retains compression history across packets and allows a higher compression ratio than does Packet by Packet Compression PPC PPC resets compression history at the start of each packet resulting in a lower compression ratio Since PPC does not depend on previous packets you should select this option for a link that drops a large number of packets Select either Continuous Packet or Packet by Packet 1 3 6 1 4 1 18 3 4 22 1 1 5 4 5 Configuring Data Compression Services Parameter Default Options Function Instructions MIB Object ID History Size 32 K for software compression 8 K for hardware compression 32 KI8K Indicates the amount of memory allocated to compression history for the line Remember that history size entails separate compression and decompression histories and lookup tables on each side of a link For example if the link uses software compression with a history of 8 KB each end of the link allocates 8 KB of memory for compression 16 KB for a compression lookup table and 8 KB for decompression or 32 KB total If the link uses a compression history of 32 KB each end of the link allocates 32 KB of memory for compression 64 KB for a compression lookup table and 32 KB for decompression for a total of 128 KB Hardware compression entai
4. 6 Compression Mode parameter circuit interface 4 10 line 4 5 compression modes 1 7 compression ratio defined 1 3 D data compression architecture 1 2 deleting from a router 4 12 enabling 3 1 features 2 1 implementation 2 1 to 2 4 modes continuous 1 7 packet by packet 1 7 overview 1 1 to 1 6 performance 1 3 Index data compression parameters overview 1 7 to 1 11 daughterboards for hardware compression 1 3 default parameter settings circuit interface A 1 line interface A 1 deleting compression 4 12 dial backup 2 4 dial on demand 2 3 E editing parameters 4 1 to 4 12 Enable parameter circuit interface 4 10 line 4 5 enabling data compression 3 1 engine type 1 10 Engine Type parameter circuit interface 4 12 line 4 7 F fallback compression mode 1 11 Fallback Compression Mode parameter line 4 8 Frame Relay configuring data compression for 4 2 data compression features 2 2 enabling data compression for use with 3 1 modes 2 2 4 2 Index 1 H hardware compression 1 3 2 1 header compression 2 1 history buffer 1 2 history size 1 7 History Size parameter circuit interface 4 11 line 4 6 implementation notes 2 1 to 2 4 L Lempel Ziv algorithm 1 2 line parameters 4 5 to 4 8 LZ 77 algorithm 1 2 multiline 2 3 multilink 2 3 N Network Control Protocol NCP negotiations 1 5 1 6 P parameters circuit interface 4 9 to 4 12
5. Data Compression Works The following sections describe how Bay Networks data compression works As you read these sections refer to Figure 1 1 which illustrates CCP and WCP initialization on a PPP link 1 4 XI Data Compression Overview m Router B Router A 1 PPP interface on network LCP negotiations complete begin CCP negotiations Send Initialization Request gt lt Send Initialization Request Send Initialization ACK gt Send Initialization ACK 2 CCP negotiations complete begin WCP negotiations including compression mode history size and buffer size Send Initialization Request gt lt Send Initialization Request Send Initialization ACK gt lt Send Initialization ACK 3 WCP negotiations complete begin NCP negotiations Send Configure Request gt Send Configure Request Send Configure ACK I Send Configure ACK 4 NCP open begin transmitting data lt Send Data SE Figure 1 1 CCP WCP and NCP Initialization on a PPP Link 1 5 Configuring Data Compression Services CCP Negotiations CCP allows the two ends of a PPP connection to negotiate whether to use data compression and if so which algorithm to use Our implementation of compression uses only the LZ 77 algorithm Note If one side of a link requests an algorithm that
6. Hardware PPC Hardware PPC is a good choice for higher speed links greater than 64 Kb s It provides better throughput than does Software CPC Chapter 2 Implementation Notes This chapter describes special features of Bay Networks data compression Bay Networks Data Compression Features Our data compression works over wide area network links running Frame Relay PPP or X 25 It includes the following features Compression for a FRE module at 4 x 128 KB s compressed throughput full duplex or 512 KB s aggregate compressed throughput Compression on an AN platform at 2 x 64 KB s compressed throughput full duplex or 128 KB s aggregate compressed throughput Compression on all intelligent link interface modules ILIs that support serial and ISDN BRI ports Software compression support for all Bay Networks platforms AN ASN and BN plus VME Hardware compression support in an optional daughterboard for Frame Relay and PPP networks that use the octal synchronous link module for the BN using FRE2 processors only Compression configurable on a per circuit or line basis Compression on MCT 1 and MCE 1 lines Compression on multiline and multilink We do not support VJ header compression 2 1 Configuring Data Compression Services Compression Features for Specific Protocols Bay Networks data compression services vary in some details according to the WAN protocols you configure Read the following sections to lea
7. Slot 4 Module 1 COM3 mrs Line 205105 Slot 5 Module 1 COMS Line 205106 Slot 5 Module 1 COM6 Line 205107 Slot 5 Module 1 COM7 Line 205108 Slot 5 Module 1 COM8 Enable ENABLE Compression Mode CONTINUOUS PACKET History Size 32K Buffer Size NORMAL Engine Type OFTWARE Fallback Compression Mode SOFTWARE CPC Figure 4 2 WCP Line Interfaces List Window 2 Select a line from the list in the top left corner of the window The values in the parameter fields apply to the WCP line interface you highlight 3 Edit those parameters you want to change using the descriptions following this list as a guide 4 4 Editing Data Compression Parameters 4 Click on Apply to implement your changes 5 Repeat Steps 2 through 4 for each parameter you want to edit 6 Click on Done to exit the window WCP Line Parameter Descriptions Use the following descriptions as guidelines when you configure the WCP line parameters Parameter Enable Default Enable Options Enable Disable Function Enables or disables data compression on the line Instructions WCP automatically sets this parameter to Enable when you select WCP in MIB Object ID Parameter Default Options Function Instructions MIB Object ID the Select Protocols window If you want to temporarily disable WCP rather than delete it from the platform set this parameter to Disable Reset it to Enable to re enable WCP 1 3 6 1 4 1 18 3 4 22 1 1
8. in group mode for that interface Conversely if you enable data compression in group mode but not on a PVC you have configured for hybrid mode the hybrid circuit does not use compression 2 2 Implementation Notes PPP Services You can use software or hardware data compression on all PPP circuits including multiline and multilink bandwidth on demand dial on demand and dial backup lines When you use compression on a bandwidth on demand dial on demand or dial backup circuit WCP automatically configures or deletes compression as lines are added to or removed from the circuit Multiline Multiline is a feature that enables you to configure a single circuit that consists of one or more WAN data paths A data path is a logical point to point channel it can be a permanent or dial up physical line or it can be a virtual circuit connection Multiline provides both increased fault tolerance and greater bandwidth between two sites For more information about Bay Networks multiline see Configuring Line Services or Configuring Customer Access BNX Software Multilink The multilink feature of PPP provides capabilities beyond those of multiline circuits Multilink consists of a bundle of lines between two peers consisting of up to four links Multilink has the ability to e Distribute traffic across the lines in the bundle in amounts roughly proportional to the effective bandwidth of each link e Use lines that have different spe
9. options the parameter function instructions for setting the parameter and the Management Information Base MIB object ID With the exception of the Engine Type and Fallback Compression Mode parameters these parameters apply to both software and hardware based compression The Engine Type and Fallback Compression Mode parameters apply to hardware based compression only The Technician Interface allows you to modify parameters by issuing set and commit commands with the MIB object ID This process is equivalent to modifying parameters using Site Manager For more information about using the Technician Interface to access the MIB refer to Using Technician Interface Software Caution The Technician Interface does not verify that the value you enter for a parameter is valid Entering an invalid value can corrupt your configuration After you enable compression you can edit all data compression parameters from the Configuration Manager window Figure 4 1 Refer to Configuring Routers or Configuring Customer Access BNX Software for instructions on using Site Manager to access this window Then read the section that follows for the protocol you are configuring 4 1 Configuring Data Compression Services BT A E E Configuration Mode Local LOCAL FILE rmp mimer i bechpubs shir ley ocre Beckhbone Link Hode BLA 9 00 Color Key Used Description Dormer bors Had Quad Zuse Oi EE ere EX Quad Syne fi com co
10. other such as satellite connections Select None for links that drop a very small number of packets Increase the buffer size for a link with a large number of resets Note Because X 25 has features that check for errors and prevent data loss Bay Networks data compression software ignores the Buffer Size parameter for X 25 If you are configuring compression for X 25 you do not have to set this parameter MIB Object ID Parameter Default Options Function Instructions MIB Object ID 1 3 6 1 4 1 18 3 4 22 1 1 7 Engine Type Software unless you have configured an Octal Sync Link module that has a hardware compression daughterboard in which case the default is Hardware Software Hardware Determines whether compression for this node will be software or hardware based You can use hardware compression with Frame Relay and PPP only You can use software compression with Frame Relay PPP or X 25 Select Software to use software based compression or select Hardware to use hardware based compression 1 3 6 1 4 1 18 3 4 22 1 1 8 4 7 Configuring Data Compression Services Parameter Default Options Function Instructions MIB Object ID Fallback Compression Mode Software CPC Software CPC Hardware PPC This parameter is for hardware compression only Use it to indicate the compression mode you want to use when no hardware compression contexts are available Software CPC is a goo
11. service contracted customers from two U S and three international support centers If you have purchased your Bay Networks product from a distributor or authorized reseller contact the technical support staff of that distributor or reseller for assistance with installation configuration troubleshooting or integration issues Customers also have the option of purchasing direct support from Bay Networks through a variety of service programs The programs include priority access telephone support on site engineering assistance software subscription hardware replacement and other programs designed to protect your investment xiv About This Guide To purchase any of these support programs including PhonePlus for 24 hour telephone technical support call 1 800 2LANWAN Outside the U S and Canada call 408 764 1000 You can also receive information on support programs from your local Bay Networks field sales office or purchase Bay Networks support directly from your reseller Bay Networks provides several methods of receiving support and information on a nonpriority basis through the following automated systems CompuServe Bay Networks maintains an active forum on CompuServe All you need to join us online is a computer a modem and a CompuServe account We also recommend using the CompuServe Information Manager software available from CompuServe The Bay Networks forum contains libraries of technical and product documents
12. 8 KB and 32 KB contexts on either board Be aware that if you are bringing VCs up and down memory fragmentation can occur Even though you have 32 or more KB of compression memory available if it is on different pages you will not be able to configure a 32 KB context To solve this problem you must save your configuration and reset the slot When you reset the slot available compression memory is rearranged to be contiguous If you have memory available you will always be able to add an 8 KB context because 8 KB is the smallest divisible amount of compression memory Configuring Data Compression Services Buffer Size Buffer size is the amount of memory allocated to keep the transmission history You must configure this parameter to protect against data loss if you run Frame Relay or PPP You can select a buffer size of None Normal Large or Very Large The default value is Normal Configure buffer space based on the following conditions e Length of time it takes for data to travel over the link A Normal buffer size usually suffices for a coast to coast connection within the United States You may need a Large or Very Large buffer if your link is over a Satellite connection e Number of dropped packets Increase the buffer size on a link with a large number of dropped packets Decrease the buffer size even to None to conserve memory on a link with a very small number of dropped packets es Number of resets Increase the buf
13. Compression Mode 4 10 Enable 4 10 Engine Type 4 12 History Size 4 11 default settings A 1 editing 4 1 to 4 12 line 4 5 to 4 8 Buffer Size 4 3 4 7 Compression Mode 4 5 Enable 4 5 Engine Type 4 7 History Size 4 6 line Fallback Compression Mode 4 8 overview 1 7 to 1 11 performance 1 3 PPP bandwidth on demand 2 3 configuring data compression for 4 3 data compression features 2 3 dial backup 2 4 dial on demand 2 3 enabling data compression for use with 3 1 multiline 2 3 multilink 2 3 S Select Protocols window enabling data compression from 3 1 software compression 1 3 T throughput defined 1 3 W WCP defined 1 2 deleting from a router 4 12 features 2 1 implementation 2 1 to 2 4 initialization 1 5 negotiations 1 6 overview 1 1 to 1 6 X X 25 configuring data compression for 4 3 data compression features 2 4 DDN service 2 4 4 3 enabling data compression for use with 3 1 PDN service 2 4 4 3 Index 2
14. Configuring Data Compression Services Router Software Version 10 0 Site Manager Software Version 4 0 Software Version BNX 6 0 Site Manager Software Version BNX 6 0 Part No 112910 Rev A January 1996 a Bay Networks ES Bay Networks 4401 Great America Parkway 8 Federal Street Santa Clara CA 95054 Billerica MA 01821 Copyright 1988 1996 Bay Networks Inc All rights reserved Printed in the USA January 1996 The information in this document is subject to change without notice The statements configurations technical data and recommendations in this document are believed to be accurate and reliable but are presented without express or implied warranty Users must take full responsibility for their applications of any products specified in this document The information in this document is proprietary to Bay Networks Inc The software described in this document is furnished under a license agreement and may only be used in accordance with the terms of that license A summary of the Software License is included in this document Restricted Rights Legend Use duplication or disclosure by the United States Government is subject to restrictions as set forth in subparagraph c 1 Gi of the Rights in Technical Data and Computer Software clause at DFARS 252 227 7013 Notice for All Other Executive Agencies Notwithstanding any other license agreement that may pertain to or accompany the delivery of this computer softw
15. Data Compression Services WCP Interface Parameter Descriptions Use the following descriptions as guidelines when you configure the WCP interface parameters Parameter Enable Default Enable Options Enable Disable Function Enables or disables data compression on the circuit Instructions WCP automatically sets this parameter to Enable when you select WCP in the Select Protocols window If you want to temporarily disable WCP rather than delete it from the platform set this parameter to Disable Reset it to Enable to re enable WCP MIB Object ID 1 3 6 1 4 1 18 3 4 22 2 1 2 Parameter Compression Mode Default Inherit from Line Options Continuous Packet Packet by Packet Inherit from Line Function Indicates the compression mode on the circuit Continuous Packet Compression CPC retains compression history across packets and allows a higher compression ratio than does Packet by Packet Compression PPC PPC resets compression history at the start of each packet resulting in a lower compression ratio Since PPC does not depend on previous packets you should select this option for a link that drops a large number of packets Inherit from Line allows you to set WCP parameters at the line level and apply them to circuits For PPP with only one circuit per line this means that you can configure WCP at either the circuit level or the line level Instructions Select Inherit from Line if you want to accept the
16. HDLC PPP OSPF EGP BGP and basic DLSw The LAN Suite includes DECnet Phase 4 AppleTalk Phase 2 OSI VINES IPX and ATM DXI in addition to the System Suite The WAN Suite includes ATM DXI Frame Relay LAPB and X 25 in addition to the System Suite The Corporate Suite includes the System LAN and WAN suites in their entirety xiii Configuring Data Compression Services e The ARE ATM Suite provides RFC 1483 and 1577 compliance ATM UNI 3 0 signaling in addition to the LAN Suite e The ARE VNR Corporate Suite provides ATM Forum LAN Emulation in addition to the ARE ATM Suite and Corporate Suite e The BNX Suite includes IP Routing SNMP Agent Bay Networks HDLC PPP OSPF EGP BGP File Based Performance Statistics Frame Relay switching and Frame Relay billing and selected components from the Corporate ARE ATM and ARE VNR Corporate suites Availability of features and functionality described in this guide depends on the suites you are using Before You Begin Before using this guide you must complete the following procedures e Create and save a configuration file that has at least one Frame Relay PPP or X 25 interface e Retrieve the configuration file in local remote or dynamic mode Refer to Configuring Routers or Configuring Customer Access BNX Software for instructions Bay Networks Customer Support Bay Networks provides live telephone technical support to our distributors resellers and
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18. Protocol PPP and X 25 networks for all router platforms and all serial interfaces This includes PPP compression on multiline multilink on the ISDN BRI module and on interfaces that use raise DTR or V 25 bis signaling with dial services e Hardware based compression for Frame Relay and PPP networks that use the octal synchronous link module for the Backbone Node BN using FRE2 processors Bay Networks provides hardware compression as an optional daughterboard that attaches to the octal synchronous link module Hardware compression supports all of the PPP services that software compression supports Bay Networks software and hardware based compression interoperate fully because they use the same algorithm To use data compression effectively you must make decisions about how much memory to allocate to this task The goal is to compress data as much as possible and to transmit the data as quickly as possible without unduly taxing the resources of the router Configuring Data Compression Services Data Compression Architecture Bay Networks uses the following algorithm and protocols to provide data compression services e LZ 77 algorithm e Compression Control Protocol draft RFC Bay Networks proprietary compression protocol WCP LZ 77 Algorithm We base our data compression on a Lempel Ziv LZ 77 algorithm The algorithm uses a Sliding history buffer that stores the data that the network link has processed most recent
19. To delete WCP from all circuits on which it is currently configured complete the following steps 1 From the Configuration Manager window refer to Figure 4 1 select Protocols gt WCP gt Delete WCP A window pops up and prompts Do you REALLY want to delete WCP 2 Click on OK Site Manager returns you to the Configuration Manager window WCP is no longer operating on the platform 4 12 Appendix A Parameter Default Settings Tables A 1 and A 2 list WCP line and circuit interface parameters and their default values See Chapter 4 for instructions on editing these parameters Table A 1 WCP Line Interface Parameters Parameter Default Enable Enable Compression Mode Continuous Packet History Size 32 KB Buffer Size Normal Engine Type Software unless you have configured an Octal Sync Link Module that has a hardware compression daughterboard in which case the default is Hardware Fallback Compression Mode Software CPC for hardware compression only Table A 2 WCP Circuit Interface Parameters Parameter Default Enable Enable Compression Mode Inherit from Line History Size Inherit from Line Engine Type Inherit from Line bandwidth on demand 2 3 buffer size 1 10 Buffer Size parameter 4 3 line 4 7 C CCP 1 2 circuit interface parameters 4 9 to 4 12 Compression Control Protocol CCP definition 1 2 initialization 1 5 negotiations 1
20. aces List Window c cccccccscesceeesessesseaseseeeeeeeeseeese 4 4 WOP Circuit Interfaces List Window 4 9 Tables Table 1 1 Hardware Compression 8 KB Contexts ccccceeseeeeeeeneeeseteeeeeeeetees 1 9 Table 1 2 Hardware Compression 32 KB Contexts c sccceeesesseeeeeeesteeeseeeees 1 9 Table A 1 WOP Line Interface Parameters ccccccccesssccceceeseeeeeeeesseeeeeesesseaaeens A 1 Table A 2 WOP Circuit Interface Parameters rrrrrrnrrrnnvvvnnrrnnnrvrnrrrnsrrrnnrrrnrrrnnnennn A 1 xi About This Guide If you are responsible for configuring and managing Bay Networks routers and or BNX switching platforms running over Frame Relay Point to Point or X 25 networks read this guide to learn how to customize Bay Networks platforms for software and hardware based data compression Refer to this guide for An overview of data compression services Chapter 1 Implementation notes that may affect how you configure compression services Chapter 2 Instructions for using Site Manager to enable data compression Chapter 3 Descriptions and instructions for editing compression line and interface parameters Chapter 4 Default parameters settings Appendix A Software Suites Routing and Switching software is available in the following suites The System Suite includes IP routing 802 1 Transparent Bridge Source Route Bridge Translation Bridge SNMP Agent Bay Networks
21. are the rights of the United States Government regarding its use reproduction and disclosure are as set forth in the Commercial Computer Software Restricted Rights clause at FAR 52 227 19 Trademarks of Bay Networks Inc ACE AFN BCN BLN BN CN FRE LN Optivity SynOptics SynOptics Communications Wellfleet and the Wellfleet logo are registered trademarks and AN ANH ASN BaySIS BayStack BCNX BLNX BNX EZ Internetwork EZ LAN FN PathMan PhonePlus PPX Quick2Config RouterMan SPEX Bay Networks Bay Networks Press the Bay Networks logo and the SynOptics logo are trademarks of Bay Networks Inc Third Party Trademarks All other trademarks and registered trademarks are the property of their respective owners Statement of Conditions In the interest of improving internal design operational function and or reliability Bay Networks Inc reserves the right to make changes to the products described in this document without notice Bay Networks Inc does not assume any liability that may occur due to the use or application of the product s or circuit layout s described herein Portions of the code in this software product are Copyright 1988 Regents of the University of California All rights reserved Redistribution and use in source and binary forms of such portions are permitted provided that the above copyright notice and this paragraph are duplicated in all such forms and that any documentation advertising material
22. chapter Configuring Data Compression for X 25 You can use software based data compression with X 25 X 25 allows many circuits per line You may wish to use data compression on some circuits but not on others To configure compression for individual circuits follow the instructions in the Editing WCP Circuit Interface Parameters section later in this chapter When you use compression with X 25 PDN or DDN services you must enable compression on both sides of the X 25 link for the circuit line and X 25 service record parameters or your data will be garbled Configuring Data Compression for PPP You can use software or hardware based data compression with PPP Since PPP allows only one circuit per line you can configure most PPP WCP parameters by selecting either Protocols gt WCP gt Lines or Protocols gt WCP Interfaces The only parameter that does not appear in both places is Buffer Size which is a line parameter only 4 3 Configuring Data Compression Services Editing WCP Line Parameters To edit WCP line parameters begin at the Configuration Manager window refer to Figure 4 1 and proceed as follows 1 Select Protocols gt WCP7 Lines The WCP Line Interfaces List window appears Figure 4 2 WCP Line Interfaces List Line 203105 Slot 3 Module 1 COMS Done Line 203106 Slot 3 Module 1 COM6 Apply COM COMS Values Line 203107 Slot 3 Module 1 Line 203108 Slot 3 Module 1 Line 204103
23. d choice for lower speed links 64 Kb s or less It generally affords a better compression ratio than does Hardware PPC Hardware PPC is a good choice for higher speed links greater than 64 Kb s It provides better throughput than does Software CPC Refer to Chapter 1 for explanations of continuous packet and packet by packet compression modes Select Software CPC or Hardware PPC 1 3 6 1 4 1 18 3 4 22 1 1 10 4 8 Editing Data Compression Parameters Editing WCP Circuit Interface Parameters To edit WCP circuit interface parameters begin at the Configuration Manager window refer to Figure 4 1 and proceed as follows 1 Select Protocols gt WCP Interfaces The WCP Circuit Interfaces List window appears Figure 4 3 WCP Circuit Interfaces List Done Delete Apply l Values Help Enable ENABLE Compression Mode INHERIT FROM LINE History Size INHERIT FROM LINE Engine Type INHERIT FROM LINE Figure 4 3 WCP Circuit Interfaces List Window 2 Select the WCP circuit that you want to edit from the list in the top left corner of the window The values in the parameter fields apply to the WCP circuit interface you highlight 3 Edit those parameters you want to change using the descriptions following this procedure as a guide 4 Click on Apply to implement your changes 5 Repeat Steps 2 through 4 for each parameter you want to edit 6 Click on Done to exit the window 4 9 Configuring
24. designed to help you manage and troubleshoot your Bay Networks products Software agents and patches are available and the message boards are monitored by technical staff and can be a source for problem solving and shared experiences Customers and resellers holding Bay Networks service contracts can visit the special libraries to acquire advanced levels of support documentation and software XV Configuring Data Compression Services InfoFACTS To open an account and receive a local dial up number call CompuServe at 1 800 524 3388 and ask for Representative No 591 Inthe United Kingdom call Freephone 0800 289378 e In Germany call 0130 37 32 In Europe except for the United Kingdom and Germany call 44 272 760681 e Outside the U S Canada and Europe call 614 529 1349 and ask for Representative No 591 or consult your listings for an office near you Once you are online you can reach our forum by typing the command GO BAYNETWORKS at any prompt InfoFACTS is the Bay Networks free 24 hour fax on demand service This automated system contains libraries of technical and product documents designed to help you manage and troubleshoot your Bay Networks products The system can return a fax copy to the caller or to a third party within minutes of being accessed World Wide Web The World Wide Web WWW is a global information system for file distribution and online document viewing via the Internet You need a di
25. eds proportionally distributing traffic over those lines e Balance traffic load and restore packet sequence e Use switched lines such as ISDN B channels as well as leased lines e Monitor traffic volume Bandwidth on Demand Bandwidth on demand allows a secondary dial up line to augment a primary leased line when the primary line experiences congestion Congestion occurs when traffic volume exceeds line capacity When congestion abates the secondary line becomes inactive Dial on Demand Dial on demand enables you to establish a circuit only when you want to transmit and receive data as opposed to having a leased line which is always available By using a circuit on a demand basis you can significantly reduce your line costs 2 3 Configuring Data Compression Services Dial Backup PPP also allows you to configure a dial backup feature If a primary PPP line fails and you have enabled dial backup the router automatically establishes a backup line You cannot enable any protocols including compression on a backup circuit because a backup circuit inherits its protocols from the primary circuit If the primary circuit uses compression then the backup circuit does also For further information on Bay Networks dial services see Configuring Dial Services X 25 Services An X 25 network permits as many as 128 VCs to exist on the same physical link at the same time You can configure each of those interfaces individually t
26. effectiveness of the compression algorithm but also according to the characteristics of the data you are transmitting data that includes a lot of redundant strings compresses at a high ratio Throughput or network response time varies with the number of elements in that network that the data must traverse including the compression decompression process Software Compression Bay Networks software based data compression is most effective for sites that have WAN connections at relatively low speeds such as 56 64 KB where you want to achieve data compression at low cost and with minimal memory requirements It supports up to 512 Kb s on the FRE 040 For networks operating at faster speeds you must use hardware compression Hardware Compression Bay Networks hardware based compression works with Frame Relay and Point to Point Protocol PPP networks It best serves sites that support T 1 E 1 lines which often concentrate many lower speed remote connections Our hardware compression facility operates at high speeds and also supports high density WAN connections Use hardware compression when you want to achieve high compression ratios and throughput and also want to preserve router memory to perform other functions We offer two compression daughterboards e AG2104037 Octal Sync with a 32 context hardware compression daughterboard e AG2104038 Octal Sync with a 128 context hardware compression daughterboard Configurin
27. fer size for a link with a large number of resets and a low number of dropped packets Be aware however that a high number of resets may occur for reasons unrelated to buffer size Note X 25 is a reliable protocol which means that it has features that check for errors and prevent data loss Bay Networks data compression software therefore ignores the Buffer Size parameter for X 25 so if you are configuring compression for X 25 you do not need to set this parameter Engine Type The Engine Type parameter determines whether you use hardware or software compression The default is software compression unless you have selected an octal sync link module that has a hardware compression daughterboard either AG2104037 or AG2104038 in which case the default is hardware This parameter enables you to use software compression even though you are using one of these two octal sync link modules You would select software compression for VCs in excess of the number of contexts your hardware compression daughterboard can support Data Compression Overview Fallback Compression Mode This parameter is for hardware compression and is configurable on a line basis only Use it to indicate the compression mode you want to use when no hardware compression contexts are available The options are software CPC and Hardware PPC Software CPC is a good choice for lower speed links 64 Kb s or less It generally affords a better compression ratio than does
28. g Data Compression Services Hardware Compression Contexts A context refers to compression and decompression for a single VC Compression hardware maps a context to specific regions of compression and decompression memory If you have a 32 context compression daughterboard you can simultaneously run compression over 31 continuous packet compression CPC contexts each using an 8 KB history size with one shared 8 KB packet by packet PPC context If you have a 128 context compression daughterboard you can simultaneously run compression over 127 CPC contexts each using an 8 KB history size with one shared 8 KB PPC context For more information on CPC and PPC see the section Compression Mode later in this chapter The only difference between the two Bay Networks compression daughterboards is that the 128 context daughterboard has more memory 2 MB compression 1 MB decompression as opposed to 512 KB compression 256 KB decompression for the 32 context daughterboard Note f you configure more VCs for hardware compression than your daughterboard can support you have no way of controlling which VCs will in fact use hardware compression You should plan your network to use hardware compression on the VCs most important to you within the limits of your equipment By default all VCs that exceed the hardware context limit use software compression For more information see the section History Size later in this chapter How
29. ls similar requirements Selecting 32 K for PPP WCP should not pose a problem because PPP allows only one circuit per line Select 8 K or 32 K for Frame Relay and X 25 lines depending on the resources of your network Remember that if you are running Frame Relay in group mode each interface in the group maintains its own history size In general 8 KB histories are appropriate for WAN links that run at 64 Kb s or less because less throughput is required Use an 8 KB history size with Frame Relay and X 25 which have large numbers of VCs and low available bandwidth You may want to allocate a 32 KB history size for links with speeds higher than 64 Kb s to improve throughput The compression engine can find a data pattern match up to three times faster using a 32 KB history than an 8 KB history If you select different history sizes for the two sides of a link the smaller of the two becomes the effective history size Select either 32 K or 8 K 1 3 6 1 4 1 18 3 4 22 1 1 6 4 6 Parameter Default Options Function Instructions Editing Data Compression Parameters Buffer Size Normal Very Large Large Normal None Indicates the amount of buffer memory for the transmission history on a line Set this parameter according to the end to end round trip length of a WCP connection Select Normal for most land line coast to coast connections Select Large or Very Large for connections at a great distance from each
30. ly The compressor compares new data strings with data it has already processed and stored in the buffer When the compressor detects data strings that match data it has already processed it replaces those strings with offset and length tokens that are shorter than the original strings thus compressing the data Compression Control Protocol CCP Bay Networks uses the draft RFC Compression Control Protocol CCP only to enable or disable compression for PPP CCP also includes a history reset request and acknowledgment capability but our implementation of data compression does not use these features Bay Networks Compression WCP Bay Networks data compression uses a proprietary transfer protocol WCP to enable compression for Frame Relay and for X 25 and to transport compressed packets for Frame Relay X 25 and PPP WCP negotiates compression mode history size and buffer size For Frame Relay and PPP WCP also retransmits packets in the event of packet loss and provides protection from inadvertent data expansion LAPB retransmits packets for X 25 1 2 Data Compression Overview Data Compression Performance The goals in using data compression are to achieve a high compression ratio while maximizing throughput Compression ratio is the size of uncompressed data compared to the size of the same data after it has been compressed Throughput refers to the speed of transmitting data The compression ratio varies according to the
31. m RER HETE com i S200 Quad Syms come fi om Cintes Resource Hodule Figure 4 1 Configuration Manager Window Configuring Data Compression for Frame Relay You can use either hardware or software based data compression with Frame Relay Read the following sections to learn how to configure data compression for Frame Relay Group Access and Hybrid Access When you configure Frame Relay in group access or hybrid access mode you can run data compression on all members of the group or on none Therefore the easiest way to configure compression is to set values for the line parameters and to accept the parameter default value Inherit from Line for the interfaces Follow the instructions in the Editing WCP Line Parameters and Editing WCP Circuit Interface Parameters sections later in this chapter 4 2 Editing Data Compression Parameters Hybrid Access If you configure Frame Relay in Group access mode and then add a PVC in Hybrid mode the configuration file you create for the hybrid access PVC takes precedence over the Group configuration Data compression will work only if you specifically configure it for the Hybrid PVC Direct Access When you configure Frame Relay in direct access mode you can configure circuits individually to run compression or not To configure parameters for individual PVCs follow the instructions in the Editing WCP Circuit Interface Parameters section later in this
32. nnnennne 3 1 Enabling Data Compression for 3 28 3 1 Chapter 4 Editing Data Compression Parameters Configuring Data Compression for Frame Relay rannvvnnnrrrnnnnvnnnenvrnnnnrnnnnnrrenrnrrnnsnnneeenn 4 2 Group Access and Hybrid ACCESS ccscccceeceeeeeeeeceeeeeeseaeeeeeeeeesaeeeeeneeeseaeeeseaeeeeaas 4 2 Hybrid AcCeSS c 0 ndied clin isd Ed 4 3 Biller e 4 3 Configuring Data Compression for X 25 ccccccesceceeeeeeeeeeeeceeeeeeeaeeeeneeeeeaaeeeseeeeessaeeneeaeees 4 3 vi Configuring Data Compression for PPP A 4 3 Editing WCP Line Parameters rrrnnnnrnnnnnvrvnnnrrnnnnnrvnnnrrnnannnnnnnrransnnnnnrerransnnnnnserrreennnnnsennn 4 4 WOP Line Parameter Descriptions 4 5 Editing WCP Circuit Interface Parameters rrnnannvnnnnrrrnnnnvnnnnrrrnnnnvnnnrrrrnnnnrnererrressnrnnsennn 4 9 WCP Interface Parameter Descriptions 0 cceesceeeceeeeeeeeeceeeeeeaeeseeeeeetaaeeeeaees 4 10 Deleting Data Compression from a Platform rrrrnnnnrnnnnrrnnnnnrvnnnrrrnnnnnnnnerrrvnnnnrnnennnen 4 12 Appendix A Parameter Default Settings Index vii Figure 1 1 Figure 3 1 Figure 4 1 Figure 4 2 Figure 4 3 Figures CCP WCP and NCP Initialization on a PPP Link eevrvvrnenrnrnrvrnrnrnnvnnnnnnnnn 1 5 Select Protocols Window rrnrrrnnnnnrnnrrrvennnensanannnnnnnrnavveneensannannnnnnnnnnnnnsene 3 2 Configuration Manager Window rrrrnnannvnnrnrrrnnnnvnnnerrrennnrnnnenrrvensrrnnsnnrenenr 4 2 WOP Line Interf
33. o use data compression or not X 25 PDN and DDN Services When you use data compression on circuits that you configure for X 25 PDN or DDN services you must be careful to enable compression on both sides of the link If you configure compression on only one side of a PDN or DDN link the data that travels over that link will be garbled You must also remember to enable the X 25 service record compression parameter for each X 25 interface you configure See Configuring X 25 Services for more information about this parameter X 25 Max Window Size Parameter Window size can affect packet throughput across the X 25 network Setting the X 25 Max Window Size parameter too low can cause the router to drop packets and render data compression ineffective You should configure this parameter at a higher value than the default setting 2 4 Chapter 3 Enabling Data Compression Services This chapter describes how to enable data compression services It assumes you have read Configuring Routers and that you have 1 Opened a configuration file 2 Specified hardware if this is a local mode configuration file 3 Selected the link or net module connector on which you are enabling data compression 4 Selected Frame Relay PPP or X 25 from the WAN Protocols window Note f you want to use hardware based compression you must select an Octal Sync Link Module that has a hardware compression daughterboard either AG2104037 or AG2104038 When y
34. okup table and 32 KB for decompression for a total of 128 KB Hardware compression entails similar requirements If you select different values for history size for the two sides of the link the smaller of the two sizes becomes the history size for the link Configuring Data Compression Services 8 KB History Size In general 8 KB histories are appropriate for Frame Relay and X 25 when you have large numbers of VCs 32 KB History Size For PPP with only one circuit per line you may want to use a 32 KB history You may want to allocate a 32 KB history size for links with speeds higher than 64 Kb s to improve throughput The compressor can find a data pattern match up to three times faster using a 32 KB history than an 8 KB history History Size with Hardware Compression Hardware compression daughterboards are available in 32 and 128 contexts The numbers 32 and 128 assume a history size of 8 KB per context although you can configure history size at either 8 KB or 32 KB For example if you configure history size at 32 KB you have used four 8 KB contexts and you have that many fewer contexts available to run hardware compression on your network Note Although software compression does not put strict limits on the number of contexts you can configure be aware that memory requirements for history size are the same for software and hardware compression Both boards reserve one 8 KB context for Packet by Packet as opposed to
35. ou enable data compression you do not have to configure any data compression parameters The Configuration Manager supplies default values for all data compression parameters If you want to edit these default values refer to Chapter 4 Enabling Data Compression for PPP and Frame Relay You enable data compression from the Select Protocols window Figure 3 1 that appears after you select Frame Relay or PPP from the WAN Protocols window Enabling Data Compression for X 25 To enable data compression for X 25 select Protocols gt Add Delete from the X 25 Service Configuration Window after you have Added a Service record see Configuring X 25 Services The Select Protocols window appears 3 1 Configuring Data Compression Services Select Protocols IGMP DVMRP Decnet IV P RIP SAP XNS NLSP RIP XNS E WCP kel OS Figure 3 1 Select Protocols Window 1 Scroll through the list to select WCP Bay Networks proprietary compression protocol You may also select other protocols you want to configure 2 Click on OK to implement data compression and any other protocols you want to configure and to exit the window 3 2 Chapter 4 Editing Data Compression Parameters This chapter provides information about customizing data compression parameters for the Frame Relay X 25 or PPP interfaces you configure For each WCP parameter this chapter gives the default setting valid parameter
36. rect connection to the Internet and a Web Browser such as Mosaic or Netscape Bay Networks maintains a WWW Home Page that you can access at http www baynetworks com One of the menu items on the Home Page is the Customer Support Web Server which offers technical documents software agents and an E mail capability for communicating with our technical support engineers xvi How to Get Help About This Guide For additional information or advice contact the Bay Networks Technical Response Center in your area United States Valbonne France Sydney Australia Tokyo Japan Conventions arrow character gt italic text quotation marks screen text vertical line 1 1 800 2LAN WAN 33 92 966 968 61 2 903 5800 81 3 328 005 Separates menu and option names in instructions Example Protocols AppleTalk identifies the AppleTalk option in the Protocols menu Indicates variable values in command syntax descriptions new terms file and directory names and book titles Indicate the title of a chapter or section within a book Indicates data that appears on the screen Example set Bay Networks Trap Monitor Filters Indicates that you enter only one of the parts of the command The vertical line separates choices Do not type the vertical line when entering the command Example If the command syntax is show at routes nets you enter either show at routes or show at nets but not both
37. ression Parameters manrnnrnrrnnannvnnnenrenannrnnnnnnensnnrnnnannnnnnnrrnnsnnnnenenrrsennnnesennn 1 7 Compression Mode A 1 7 elei 1 7 e KB Ee EE 1 8 32 KB Hist ry EE 1 8 History Size with Hardware Compression cccccceeeeeeeeeeeeeeeceeeeeeeeeseaeeteeeeess 1 8 Bune SZE Eege ee att net adn EE te a ret laa ee 1 10 Gs 1 10 Fallback Compression Mode ccccccesceceeeeeeeeneeeeeaeeeeeaaeeseeeeeesaaeeseeneeesaeeeseaeeeeaas 1 11 Chapter 2 Implementation Notes Bay Networks Data Compression Features ccccceeeseeeeceeeeeeeeeseceeeseaeeseeneeeeeaaeeeeneeens 2 1 Compression Features for Specific Protocols rrrrrrannrnnnorrrnnnnrnnnrnvrrnnnrnnnennrensnrnnnennrenenn 2 2 Frame Relay Services c cccssscecceeeceeeneeeceeeeeeeaaeesseneeecaaeesseaeeeseaeeeseaaeesseneeseaaeesnes 2 2 Group ACCESS 4 28 ieee i en et aAa EY 2 2 Direct ACCESS EE 2 2 Hybrid Lee 2 2 al le le 2 3 MOURE 2 00 eet pride Mader 2 3 Multilink asus hentia oe Ah el ae ae el ei 2 3 B ndwidth on Demand BE 2 3 Biaon Ru In Le WEE 2 3 Dial BACKUP srair aata iad Isdalen deed Eeleren deed 2 4 X25 SEMVICES EE 2 4 X 25 PDN and DDN Services cccccceeeeeeeeneeeeeeeeeeeeeeseneeeesaeeeeeneeessaeeeseeeeeaas 2 4 X 25 Max Window Size Parameter c cccscceceeeeeeeeeeeeeeeeeeeaeeeeeeeeeseaeeeseeeeeaas 2 4 Chapter 3 Enabling Data Compression Services Enabling Data Compression for PPP and Frame Relay murnnvnnnonvvnnnnrnnnnnvvnrnrrrnnnnn
38. rictions of this license Licensee shall not make the resulting software available for use by any third party Neither title nor ownership to Software passes to licensee Licensee shall not provide or otherwise make available any Software in whole or in part in any form to any third party Third parties do not include consultants subcontractors or agents of licensee who have licensee s permission to use the Software at licensee s facility and who have agreed in writing to use the Software only in accordance with the restrictions of this license Third party owners from whom Bay Networks has acquired license rights to software that is incorporated into Bay Networks products shall have the right to enforce the provisions of this license against licensee Licensee shall not remove or obscure any copyright patent trademark trade secret or similar intellectual property or restricted rights notice within or affixed to any Software and shall reproduce and affix such notice on any backup copy of Software or copies of software resulting from modification or combination performed by licensee as permitted by this license Bay Networks Inc 4401 Great America Parkway Santa Clara CA 95054 8 Federal Street Billerica MA 01821 Bay Networks Software License continued 10 11 12 Licensee shall not reverse assemble reverse compile or in any way reverse engineer the Software Note For licensees in the European Community
39. rn about how our implementation of data compression applies to Frame Relay PPP and X 25 services Frame Relay Services Group Access Direct Access You can use software or hardware based data compression with Frame Relay interfaces that you configure to operate in group access direct access or hybrid access mode When you enable data compression for Frame Relay in group access mode every virtual circuit in the group uses compression Each member of the group has its own compression history however so you may want to select a history size of 8 KB when you configure data compression in group mode When you use Frame Relay in direct access mode you configure each permanent virtual circuit PVC individually and each VC has its own compression history so you may want to select a history size of 8 KB You can use data compression with some PVCs and not with others Hybrid Access Hybrid access mode combines group and direct access modes for use in nonmeshed networks that use both bridging and routing over a single Frame Relay interface Hybrid access enables you to use PVCs in group mode for routing while simultaneously using the same PVCs for bridging When you enable data compression for Frame Relay on a hybrid circuit both the bridged and the routed traffic over that circuit are compressed Note that compression applies only to that PVC and not to the other PVCs from the main circuit unless you have also enabled compression
40. roughput is required Use an 8KB history size with Frame Relay and X 25 which have large numbers of VCs and low available bandwidth You may want to allocate a 32 KB history size for links with speeds higher than 64 Kb s to improve throughput The compression engine can find a data pattern match up to three times faster using a 32 KB history than an 8 KB history If you select different history sizes for the two sides of a link the smaller of the two becomes the effective history size Inherit from Line allows you to set WCP parameters at the line level and apply them to circuits Select Inherit from Line if you want to accept the value in effect for the WCP History Size line parameter Otherwise select either 32 K or 8 K 1 3 6 1 4 1 18 3 4 22 2 1 5 Configuring Data Compression Services Parameter Engine Type Default Inherit from Line Options Software Hardware Inherit from Line Function Determines whether compression for this node will be software or hardware based You can use hardware compression with Frame Relay and PPP only You can use software compression with Frame Relay PPP or X 25 Instructions Select Inherit from Line if you want to accept the value in effect for the WCP Engine Type line parameter Otherwise select Software to use software based compression or select Hardware to use Hardware based compression MIB Object ID 1 3 6 1 4 1 18 3 4 22 1 1 8 Deleting Data Compression from a Platform
41. rr renn nnnnnennreennnnenennrennnnrneennneenenn xiv E eu XV dite IR ET xvi World Wide Webs EE xvi How to Get Help mannnvenon vona nnvnnnnnrnnnnnnnnnnnvennnnrnnnnnnennn ananas anennnnrnnennnennenrnsennnnenesnresnnnneseenn xvii GONVentions EE xvii Ordering Bay Networks Publications c ccceceeeeeeeeeeeeeceeeeeeeeeeeeeeeeeeeaaeeeeeeeeetaeeneneees xviii Ae Ke IEN xviii Chapter 1 Data Compression Overview Data Compression Architecture arsrrrrrrrrnannrnnrorrrnnnnrnnnennenennrrnnennnnensrrnesnnnererrresnnnnnsennn 1 2 EZ 77 Algorithm E eeii deed dee i 1 2 Compression Control Protocol CCP ccecccccesseeceeeeeeseeeeeeeeeesaeeeeeaeeeseaeeeseeeeeaas 1 2 Bay Networks Compression WCP c cccceceeeeeeeceneeeeeeeeeeeeeeeesaaeeeeeneeesaeeeseneeeeaas 1 2 Data Compression Performance ccccccceeeseeeeeeeeeeeaeeeeeeeeeceaaeedeneeeceaaeeeeaaeeseeaeeeeiaaeeee 1 3 Software Compression cccceeceeeceneeeeeeeeeceeeeeeeaeeeceaeeeseaaeeseaeeeeeaaeeseeeeeesaeeeeeeeeessaeeeteaeees 1 3 Hardware OL 0 10 ER 0 aS 1 3 Hardware Compression Contexts mmmmmrmmmnrverrrrrrrnrrenrerrerarnrnnnrrrenennrnnsrnnenernrnennnnene 1 4 How Data Compression Works rrarnrrnnnnrrvnnnrrnnnnnrennnrrnnnnnvnnrrrrnnnnnnnererrneennnnnnernresnnnnneennn 1 4 CGP Negotiations gege a idl i a ee ete 1 6 WOP Negotiations ecceccececceeeeeeeeeeeceaeeeeeeeeeceaeeeseaeeecaeeeseaaeeseaeeeesaaeeseeeeeessaeeeseneees 1 6 RCM EE 1 6 Data Comp
42. s and other materials related to such distribution and use acknowledge that such portions of the software were developed by the University of California Berkeley The name of the University may not be used to endorse or promote products derived from such portions of the software without specific prior written permission SUCH PORTIONS OF THE SOFTWARE ARE PROVIDED AS IS AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING WITHOUT LIMITATION THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE In addition the program and information contained herein are licensed only pursuant to a license agreement that contains restrictions on use and disclosure that may incorporate by reference certain limitations and notices imposed by third parties Bay Networks Software License Note This is Bay Networks basic license document In the absence of a software license agreement specifying varying terms this license or the license included with the particular product shall govern licensee s use of Bay Networks software This Software License shall govern the licensing of all software provided to licensee by Bay Networks Software Bay Networks will provide licensee with Software in machine readable form and related documentation Documentation The Software provided under this license is proprietary to Bay Networks and to third parties from whom Bay Networks has acquired license rights Bay
43. the Software Directive dated 14 May 1991 as may be amended from time to time shall apply for interoperability purposes Licensee must notify Bay Networks in writing of any such intended examination of the Software and Bay Networks may provide review and assistance Notwithstanding any foregoing terms to the contrary if licensee licenses the Bay Networks product Site Manager licensee may duplicate and install the Site Manager product as specified in the Documentation This right is granted solely as necessary for use of Site Manager on hardware installed with licensee s network This license will automatically terminate upon improper handling of Software such as by disclosure or Bay Networks may terminate this license by written notice to licensee if licensee fails to comply with any of the material provisions of this license and fails to cure such failure within thirty 30 days after the receipt of written notice from Bay Networks Upon termination of this license licensee shall discontinue all use of the Software and return the Software and Documentation including all copies to Bay Networks Licensee s obligations under this license shall survive expiration or termination of this license Bay Networks Inc 4401 Great America Parkway Santa Clara CA 95054 8 Federal Street Billerica MA 01821 Contents About This Guide Ee xiii Before YOU BegIN EE xiv Bay Networks Customer Support mmrnrrnnnnrnnnnnnrnnnrrrnnnnnnnrr
44. the other side does not support traffic over the link continues but in uncompressed form In the example shown in Figure 1 1 negotiations begin when PPP establishes a link CCP uses the same configuration and network control protocol negotiations that the Link Control Protocol LCP uses For a detailed explanation of LCP negotiations see Establishing the PPP Link in Configuring PPP Services WCP Negotiations Frame Relay and X 25 use WCP to negotiate whether to use data compression and which algorithm to use As with PPP if one side of a link requests an algorithm the other side does not support traffic continues but in uncompressed form Each side of a link running data compression has a compressor a decompressor a compression history and a buffer When you configure compression you can edit WCP parameters for compression mode history size and buffer size to optimize compression performance on your network Data Transmission Frame Relay and X 25 data transmission using compression begins when WCP negotiations are complete For PPP Network Control Protocol NCP negotiations and WCP negotiations occur simultaneously When PPP NCP and WCP negotiations are complete data transmission using compression begins 1 6 Data Compression Overview Data Compression Parameters The following sections describe data compression parameters and give information about decisions you must make to use compression effectively on
45. value in effect for the WCP Compression Mode line parameter Otherwise select either Continuous Packet or Packet by Packet MIB Object ID 1 3 6 1 4 1 18 3 4 22 2 1 4 4 10 Parameter Default Options Function Instructions MIB Object ID Editing Data Compression Parameters History Size Inherit from Line 32 K 18 K Inherit from Line Indicates the amount of memory allocated to compression history for the circuit Remember that history size entails separate compression and decompression histories and lookup tables on each side of a link For example if the link uses software compression with a history of 8 KB each end of the link allocates 8 KB of memory for compression 16 KB for a compression lookup table and 8 KB for decompression or 32 KB total If the link uses a compression history of 32 KB each end of the link allocates 32 KB of memory for compression 64 KB for a compression lookup table and 32 KB for decompression for a total of 128 KB Hardware compression entails similar requirements Selecting 32 K for PPP WCP should not pose a problem because PPP allows only one circuit per line Select 8 K or 32 K for Frame Relay and X 25 lines depending on the resources of your network Remember that if you are running Frame Relay in group mode each interface in the entire group maintains a history size In general 8 KB histories are appropriate for WAN links that run at 64 Kb s or less because less th
46. your network Compression Mode You can compress data in one of two modes e Continuous Packet Compression CPC maintains compression history across packets CPC yields a higher compression ratio than does Packet by Packet e Packet by Packet Compression PPC creates a new history for each packet PPC yields a lower compression ratio than does CPC In most circumstances you should select CPC to maximize compression Select PPC only for links that drop a very large number of packets Be aware that under these circumstances implementing data compression may offer marginal or no advantages If either side of the link specifies PPC both sides of the link use PPC History Size Each side of the link maintains both a compression and decompression history and a lookup table The compression and decompression histories maintain a record of data that has already traveled across the network The lookup tables maintain pointers to redundant strings and the offset and length tokens that replace each of those strings You can specify either 8 KB or 32 KB of local memory to maintain a compression history If the link uses software compression with a history of 8 KB each end of the link allocates 8 KB of memory for compression 16 KB for the compression lookup table and 8 KB for decompression or 32 KB If the link uses a compression history of 32 KB each end of the link allocates 32 KB of memory for compression 64 KB for the compression lo
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