Avaya Configuring Data Compression Services Manuel d'utilisateur télécharger pdf (Page 33)

Data Compression Overview

117352-D Rev. 00

2-3

Data Compression Architecture

WCP and Hi/fn LZS use different compression algorithms and protocols. The

compression protocol that you choose depends on whether you are

communicating with routers from Bay Networks or other vendors.

Table 2-1

lists the algorithms and protocols that Bay Networks uses to provide

data compression services for WCP and Hi/fn LZS.

You must ensure that routers at both ends of the connection are using the same

compression protocol.

• If both ends of the connection are Bay Networks routers, configure both

routers to use WCP as the compression protocol.

• If the connection is a PPP link and only one end of the connection is a Bay

Networks router, configure both routers to use Hi/fn LZS.

If you want the router to negotiate which protocol is used, set the Compression

Protocol parameter to Any (see page A-15

for the parameter description).

LZ-77 Algorithm

Bay Networks WCP data compression software is based 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 recently. 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.

Table 2-1. Data Compression Algorithms and Protocols

WCP Hi/fn LZS

LZ-77 algorithm Hi/fn LZS algorithm

Compression Control Protocol (RFC 1962) Compression Control Protocol (RFC 1962)

Bay Networks proprietary WAN

Compression Protocol (WCP)

References the PPP Hi/fn LZS

Compression Protocol (RFC 1974) as a

guideline

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Avaya Configuring Data Compression Services Manuel d'utilisateur Page 33