Avaya Configuring Data Compression Services Instrukcja Użytkownika Pobierz pdf (Strona 51)

Data Compression Parameters

114061 Rev. A 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 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 for the BN, 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.

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 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 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.

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 Instrukcja Użytkownika Strona 51