Avaya Configuring Data Compression Services Uživatelský manuál stáhnout pdf (Strana 55)

Customizing Data Compression

117352-E Rev 00

3-5

History Size with Hardware Compression

Hardware compression daughterboards and net modules are available in 32, 128,

and 256 contexts. The numbers 32, 128, and 256 assume a history size of 8 KB

per context, although you can set the history size to either 8 KB or 32 KB. For

example, if you set the history size to 32 KB, you use four 8 KB contexts, and you

have that many fewer contexts available to run hardware compression on your

network.

Compression daughterboards reserve one 8 KB context for PPC, as opposed to

CPC. There is no limit to the number of VCs that can use this one PPC context.

The maximum number of VCs for the compression engine is 256.

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 KB or 32 KB histories are

that the memory used for any one history must be continuous, and that it may not

cross pages. For 8 KB contexts, these restrictions create few constraints, but for 32

KB contexts, they are significant.

Table 3-2

shows the maximum number of 8 KB contexts each daughterboard or

net module can support.

Note:

Although software compression does not place strict limits on the

number of contexts you can configure, memory requirements for history size

are the same for both software and hardware compression.

Table 3-2. Hardware Compression: 8 KB Contexts

Daughterboard or Net Module

Maximum 8 KB

CPC Contexts

Available 32 KB

CPC Contexts

Reserved 8 KB

PPC Contexts

32-context 31 0 1

128-context 127 0 1

256-context (advanced

compression coprocessor

daughterboard)

255 0 1

1 2 ... 50 51 52 53 54 55 56 57 58 59 60 ... 107 108

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Avaya Configuring Data Compression Services Uživatelský manuál Strana 55