There are algorithms that do compression technique on the TCP/IP headers to increase transmision efficiency such as Van Jacobson TCP/IP Header Compression. In case a router receives a compressed header, how does the router extract the IP header? What if there are multiple routers on the path to the destination?

Thank you.

2 Answers 2


RFC 1144 explains how both compression and decompression work. This was designed for low-speed serial links. Most links today are fast enough that this just isn't needed.

This RFC is has been around for a very long time, and just about every router vendor supports it.


The compressor assigns "connection numbers" to TCP/IP connections. The compressor and decompressor use these as indexes into a state table to construct the compressed headers and reconstruct the full headers.

The compression operates at the level of individual point to point links, it sits below the IP layer but above the link level framing. When a packet comes in over a link using header compression it will reconstruct the full header before making any routing descisions. If the outgoing interface also uses header compression it will then attempt to recompress the header.

Due to separate state tables a packet may be compressible on the incoming interface but not the outgoing interface or vice-versa.

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