Cisco Systems 3825 Header Compression passive Keyword, Header Compression iphc-format Keyword

Appendix A Cisco 3825 Mobile Wireless Edge Router RAN-O Command Reference

ip tcp header-compression

Header Compression passive Keyword

By default, the ip tcp header-compressioncommand compresses outgoing TCP traffic. This command includes an optional passive keyword. If you specify the passive keyword, outgoing TCP traffic is compressed only if incoming TCP traffic on the same interface is compressed. If you do not specify the passive keyword, all TCP traffic is compressed.

For PPP interfaces, the passive keyword is ignored. PPP interfaces negotiate the use of header-compression, regardless of whether the passive keyword is specified. Therefore, on PPP interfaces, the passive keyword is replaced by IPHC format, the default format for PPP interfaces.

Header Compression iphc-format Keyword

This command includes the iphc-formatkeyword. The iphc-format keyword indicates the type of header compression that will be used. For PPP and HDLC interfaces, when the iphc-formatkeyword is specified, Rapid Transport Protocol (RTP) header-compression is also enabled. For this reason, the ip rtp header-compressioncommand appears in the output of the show running-configcommand. Because both TCP and RTP header compression are enabled, both TCP and UDP packets are compressed.

Note For Frame Relay interfaces, the iphc-formatkeyword is not available.

Header Compression ietf-format Keyword

This command includes the ietf-formatkeyword. The ietf-formatkeyword indicates the type of header compression that will be used. For HDLC interfaces, the ietf-formatcompresses only TCP packets. For

PPPinterfaces, when the ietf-formatkeyword is specified, RTP header-compression is also enabled. For this reason, the ip rtp header-compressioncommand appears in the output of the show running-configcommand. Because both TCP and RTP header compression are enabled, both TCP and UDP packets are compressed.

		Note	For Frame Relay interfaces, the ietf-formatkeyword is not available.
Examples		The following example sets the first serial interface for header compression with a maximum of ten
		cache entries:
		Router(config)# interface serial 0
		Router(config-if)# ip tcp header-compression
		Router(config-if)# ip tcp compression-connections 10
		The following example enables RTP header compression on the Serial1/0/0.0 subinterface and limits the
		number of RTP header compression connections to 10. In this example, the optional iphc-format
		keyword of the ip tcp header-compressioncommand is specified:
		Router(config)# interface serial1/0/0.0
		Router(config-if)# encapsulation ppp
		Router(config-if)# ip tcp header-compression iphc-format
		Router(config-if)# ip tcp compression-connections 10
		The following example enables RTP header compression on the Serial1/0/0.0 subinterface and limits the
		number of RTP header compression connections to 20. In this example, the optional ietf-format
		keyword of the ip tcp header-compressioncommand is specified:
		Router(config)# interface serial1/0/0.0
		Router(config-if)# ip tcp header-compression ietf-format
		Router(config-if)# ip tcp compression-connections 20
			Cisco 3825 Mobile Wireless Edge Router Software Configuration Guide
	OL-15667-03			A-45