Header Compression Configuration - Avaya G430 Manual

Administering branch gateway

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Header compression configuration

Header compression reduces the size of packet headers, thus reducing the amount of

bandwidth needed for data. The header compression method is based on the fact that most

of the header fields remain constant or change in predictable ways throughout the session.

Thus, instead of constantly retransmitting the header, each side keeps a context table of the

sessions (the normal headers), and while sending and receiving packets it replaces the full-

length headers with one or two bytes CID (context-id) plus unpredictable deltas from the last

The Branch Gateway offers both RTP header compression, for reducing the amount of

bandwidth needed for voice traffic, and TCP and UDP header compression, for reducing the

amount of bandwidth needed for non-voice traffic.

For header compression purposes, any UDP packet with an even destination port within a

user-configurable range of ports, is considered an RTP packet.

The Branch Gateway enables decompression whenever compression is enabled. However,

when enabling header compression on a Frame Relay interface, you must first verify that the

remote host is also employing header compression. Header compression on a Frame Relay

interface does not check what the remote host is employing. Thus, it may compress headers

even when the remote host is not configured to decompress headers.

You can configure how often a full header is transmitted, either as a function of time or of

transmitted compressed packets.

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