3.4 PPP Compression
3.4.2 Configuring compression
Configuring for compression is simple: from the interface, issue the compress predictor, compress stac, compress mppc, or ip tcp header-compression command on both sides of the link.

Compression Algorithm

Predictor is more memory intensive and less CPU intensive, whereas Stacker and MPPC are more CPU intensive and less memory intensive. Memory intensive means that an extra memory allowance is required.

You need to consider this memory usage when implementing compression on any specific router. If you use a Cisco 2500 series router or better, it should be acceptable to use either of these methods if you have sufficient memory in the router.  Use caution with smaller systems that have less memory and slower CPUs, and ensure that you are not overloading the router. The interface command to enable compression follows:

Router(config-if)#compress [predictor|stac|mppc]

TCP Header Compression

The TCP header compression technique is fully described in RFC 1144. It is supported on serial lines by using HDLC, PPP, or SLIP encapsulation. You must enable the compression on both ends of the connections for TCP header compression to work. Only TCP headers are compressed-UDP headers are not affected. The following is the interface command used to activate TCP header compression:

Router(config-if)#ip tcp header-compression

The ip tcp header-compression passive command specifies that TCP header compression is not required, if the router receives compressed headers from a destination, then use header compression for that destination.

Lab Activity    
  The Atlanta Bread Company is again reviewing the costs incurred by the Macon office for dialin access to the core router. The CTO has recommended that Stacker compression be added to the asynchronous link between Atlanta and Macon to maintain compatibility with the Cisco 700 series. You will configure compression between the Atlanta core router and the Macon remote office.