User manual

Compression
Page 29-5
Compression
Data compression allows you to get more data through the Frame Relay pipeline, further
enhancing cost benefits. A typical data compression ratio on the WSX board at the hardware
level is 4:1. In addition, the compression processor (STAC 9705) has its own DRAM that can
store up to 100 virtual circuits (on a 4-port WSX) without performance degradation. An 8-port
WSX can store up to 200 virtual circuits without performance degradation. Support for more
than 100 compressed VCs (or 200 VCs on an 8-port WSX) is possible through swapping within
memory, but compression performance may decrease at these levels.
The
WSX will only compress data if you enable Compression Negotiation through software
and the Bridge/Router on the other end of the Frame Relay virtual circuit supports standard
FRF.9 compression. (An Omni Switch/Router-to-Omni Switch/Router connection would
support compression.) Negotiation is necessary because if compressed data is sent to a
Bridge/Router that does not support compression, then this Bridge/Router will not recognize
the data and will automatically drop the unrecognizable frames.
If you enable Compression Negotiation, the
WSX will query the Frame Relay device on the
other end of the circuit (according to FRF.9 specifications) to see if it supports compression. If
it does, then the WSX compresses all data except DLCMI (management) data. If it doesn’t, then
data on that virtual circuit is sent uncompressed. See Setting Configuration Parameters on
page 29-22 for information on enabling compression.
Note
Compression is not supported on the 2 universal serial
port Omni Switch/Router
WSX and Omni Switch/Router
WSX modules.