available. Why bother just compressing the TCP header? Well, compression algorithms can be
optimized if the data to be compressed has a known format and a tendency toward using
particular values. The 40-byte TCP header can be reduced to an average of 10 bytes. One of the
biggest reasons that TCP header compression can be beneficial is that it takes little processing
because of the efficient compression algorithm. Also, if a large amount of traffic is made up of
small IP packets with TCP, then the compression ratio can be more than 2-to-1. For instance, in
the "old" days when Telnet was used on a frequent basis by end users, many IP packets were
sent with the IP header, the TCP header, and just a few bytes of data typed by the user. So,
efficient compression with the possibility of more than 2-to-1 compression ratio is a very
reasonable option. If most of the IP packets using TCP in a network are large, then the
compression ratio will not be very high, making TCP header compression a less-attractive
option.
are taken. Cisco expects CCNAs to know several of the optional parameters that are shown in
this section as well.
this section lists commands, provides examples, and points out tricky features. Table 8-22 and
Table 8-23 summarize the more popular commands used for Frame Relay configuration and
verification. Two configuration samples follow. The Cisco IOS documentation is an excellent
reference for additional IP commands, and the Cisco Press book Interconnecting Cisco Network
Devices is an excellent reference, particularly if you are not able to attend the instructor-led
version of the class.
[ietf | cisco]
encapsulation that is used rather
than HDLC, PPP, and so on.
q933a | cisco}
messages sent to the switch.
of the interface. Bandwidth is
used by some routing protocols
to influence the metric.