AIS AI2524 Because priority queuing changes the order in which, Interface is not recommended

AI2524 Router Card User’s Manual

A typical TCP/IP packet includes a 40-byte datagram header. Once a connection is established, the header information need not be repeated in every packet that is sent. Reconstructing a smaller header that iden- tifies the connection and indicates the fields that changed and the amount of change reduces the number of bytes transmitted. The aver- age compressed header is 10 bytes long.

For this algorithm to function, packets must arrive in order. If packets arrive out of order, the reconstruction will appear to create regular TCP/IP packets but the packets will not match the original.

Note:	Because priority queuing changes the order in which
	packets are transmitted, enabling priority queueing on th
	interface is not recommended.

You can configure TCP/IP header compression in either of two ways:

zConfigure an Individual IP Map for TCP/IP Header Compression

zConfigure an Interface for TCP/IP Header Compression

Note:	If you configure an interface with Cisco encapsulation
	and TCP/IP header compression, Frame Relay IP maps
	inherit the compression characteristics of the interface.
	However, if you configure the interface with IETF
	encapsulation, the interface cannot be configured for
	compression. Frame Relay maps will have to b
	configured individually to support TCP/IP header
	compression.

Configure an Individual IP Map for TCP/IP Header

Compression

TCP/IP header compression requires Cisco encapsulation. If you need to have IETF encapsulation on an interface as a whole, you can still configure a specific IP map to use Cisco encapsulation and TCP header compression.

In addition, even if you configure the interface to perform TCP/IP header compression, you can still configure a specific IP map not to compress TCP/IP headers.

You can specify whether TCP/IP header compression is active or pas- sive. Active compression subjects every outgoing packet to TCP/IP header compression. Passive compression subjects an outgoing TCP/ IP packet to header compression only if the packet had a compressed TCP/IP header when it was received.

Page 13-40	August 1997
	2524UM