Avaya Configuring Data Compression Services Bedienungsanleitung PDF herunterladen (Seite 67)

Data Compression Parameters

117352-B Rev. 00

A-7

Parameter: History Size

Path: Configuration Manager > Protocols > WCP > Interfaces

Default: Inherit from Line

Options: 32 K

8 K

Inherit from Line

Function: Indicates the amount of memory allocated to compression history for the line.

Remember that history size has separate compression and decompression

histories and lookup tables on each side of a link. If the link uses a compression

history of 8 KB, each end of the link allocates a total of 32 KB as follows:

• 8 KB for compression

• 16 KB for a lookup table

• 8 KB for decompression

If the link uses a compression history of 32 KB, each end of the link allocates a

total of 128 KB as follows:

• 32 KB for compression

• 64 KB for a lookup table

• 32 KB for decompression

Hardware compression has similar requirements.

Selecting 32 K for PPP WCP should not be a problem for the BN, because PPP

allows only one circuit per single or multiple lines. Select 8 K or 32 K for frame

relay and X.25 lines, depending on the resources of your network. Selecting 32

K for PPP WCP on the ASN can cause problems, particularly if you are using a

32-context compression net module.

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 may have low available

bandwidth, and with PPP on a 32-context net module. 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 each side 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.

Instructions: 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.

MIB Object ID: 1.3.6.1.4.1.18.3.4.22.2.1.5

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Avaya Configuring Data Compression Services Bedienungsanleitung Seite 67