Header compression reduces the size of packet headers, thus reducing the amount of bandwidth needed for data. The header compression method is because 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 packet.

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.

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