Van Jacobson is a compressed TCP protocol which improves the TCP/IP performance over low speed (300 to 19,200 bps) serial links. Van Jacobson is to solve problems in link-level framing, address assignment, routing, authentication and performance.

The compression proposed in the Van Jacobson protocol is similar in spirit to the Thinwire-II protocol. However, this protocol compresses more effectively (the average compressed header is 3 bytes compared to 13 in Thinwire-II) and is both efficient and simple to implement. Van Jacobson compression is specific to TCP/IP datagrams.

Protocol Structure

• C, I, P, S, A, W, U - Change mask. Identifies which of the fields expected to change per-packet actually changed.
• Connection number - Used to locate the saved copy of the last packet for this TCP connection.
• TCP checksum - Included so that the end-to-end data integrity check will still be valid.
• Urgent pointer - This is sent if URG is set.
• D values for each field - Represent the amount the associated field changed from the original TCP (for each field specified in the change mask).

Related Terms: TCP

Sponsor Source: Van Jacobson is defined by IETF (http://www.ietf.org) RFC 1144.

Reference: http://www.javvin.com/protocol/rfc1144.pdf: Compressing TCP/IP Headers for Low-Speed Serial Links