Avaya Configuring Data Compression Services Uživatelský manuál stáhnout pdf (Strana 32)

Configuring Data Compression Services

2-4

117352-B Rev. 00

Stac LZS Algorithm

Hi/fn™ is a wholly owned subsidiary of Stac, Inc. Bay Networks Stac LZS

compression software incorporates LZS

from Hi/fn™. In this documentation the

Hi/fn™ LZS

algorithm is referred to as Stac LZS.

Bay Networks Stac LZS compression software is based on the Stac LZS algorithm

to transport compressed packets across a PPP link. Stac LZS implements an error

detection mechanism, which means it can detect if packets are lost during

transmission. Stac LZS does not retransmit packets if they are lost.

The Stac LZS compression algorithm searches incoming data for redundant data

strings and replaces these strings in the outgoing data with encoded tokens of

shorter length. Stac LZS creates the encoded tokens from information in a table

that the Stac LZS algorithm builds. This table consists of string matches, which

point to previous incoming data. As the table builds and tokens are created,

subsequent data is compressed based on previous data.

Compression Control Protocol (CCP)

Bay Networks uses RFC 1962, the Compression Control Protocol (CCP) to enable

or disable compression across a PPP link and determine what kind of compression

is used. CCP also includes a history reset request and acknowledgment capability,

which Stac LZS uses but WCP does not. WCP uses its own negotiation

mechanism.

Bay Networks WAN Compression Protocol (WCP)

Bay Networks proprietary WAN Compression Protocol (WCP) is an IETF draft

standard. WCP enables compression for frame relay and for X.25, and transports

compressed packets for PPP, frame relay, and X.25. WCP negotiates compression

mode, history size, and buffer size. For PPP and frame relay, WCP also

retransmits packets in the event of packet loss, and protects against inadvertent

data expansion (LAPB retransmits packets for X.25).

WCP 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. WCP supports connections up to

512 KB/s on the FRE-040. For networks operating at faster speeds, you should

use hardware compression.

1 2 ... 27 28 29 30 31 32 33 34 35 36 37 ... 71 72

Žádné komentáře

Avaya Configuring Data Compression Services Uživatelský manuál Strana 32