The technique of header compression created by Van Jacobson also called VJHC algorithm and described in RFC 1144 is well established and used to improve the bandwidth usage in a wireless local area network WLAN. It is a data compression protocol specifically designed to improve Transmission Control Protocol/Internet Protocol TCP/IP performance over slow serial links. The header compression technique reduces the normal 40 byte TCP/IP packet headers down to 3-4 bytes for the average case. It does this by saving the state of TCP connections at both ends of a link and only sending the differences in the header fields that change. In a WLAN, header compression can be implemented in access points AP or routers. Both of these implementations encounter different problems:    1. APs and routers in an existing network may come from different manufacturers, they are based on different operating system platforms OS, and usually have very limited CPU performance, so it may be difficulty to implement header compression in them;    2. Lack of scalability. Because of limited CPU power, the number of header-compression-enabled mobile stations supported in a WLAN will be quite limited, and several header compression protocols can not be deployed simultaneously in the same network;    3. If the header compression is implemented in APs, that will need context transfer when mobile station roaming among a group of APs. This may cause longer handover latency.