When designing an internetwork, the customer
cannot assume that an application will go over point-to-point lines.
If link compression is used, the header may not be readable at a
particular hop, however, the customer can use payload compression
instead.
When using payload compression, the header is
left unchanged and packets can be switched through a WAN packet
network. Payload compression is appropriate for virtual network
services such as X.25, Switched Multimegabit Data Service (SMDS),
Frame Relay, and ATM. It uses the STAC compression method discussed
previously.