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Van Jacobson: a compressed TCP protocolVan 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 - Van Jacobson TCP compressed protocolThe format of the compressed TCP is as follows:
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|
C |
I |
P |
S |
A |
W |
U |
|
Connection number (C) |
|
TCP checksum |
|
Urgent pointer (U) |
|
D Window (W) |
|
D Ack (A) |
|
D Sequence (S) |
|
D IP ID (I) |
|
data |
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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 Protocols
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 |
