Cisco Systems 78-11741-02 Wireless Office Headset User Manual


 
Configuring IP Services
Configuring TCP Performance Parameters
IPC-111
Cisco IOS IP Configuration Guide
Compressing TCP Packet Headers
You can compress the headers of your TCP/IP packets in order to reduce their size, thereby increasing
performance. Header compression is particularly useful on networks with a large percentage of small
packets (such as those supporting many Telnet connections). To enable TCP header compression, use the
following command in interface configuration mode:
The ip tcp header-compression interface configuration command only compresses the TCP header; it
has no effect on UDP packets or other protocol headers. The TCP header compression technique is
supported on serial lines using High-Level Data Link Control (HDLC) or PPP encapsulation. You must
enable compression on both ends of a serial connection.
By using the passive keyword, you can optionally specify outgoing packets to be compressed only if
TCP incoming packets on the same interface are compressed. If you specify the command without the
passive keyword, the software will compress all traffic. Without the command, the default is no
compression.
Note Fast processors can handle several fast interfaces, such as T1 lines, that are running header
compression. However, you should think carefully about the traffic characteristics of your network
before compressing TCP headers. You might want to use the monitoring commands to compare
network utilization before and after enabling TCP header compression.
Expressing TCP Header Compression
Before Cisco IOS Release 12.0(7)T, if compression of TCP headers was enabled, compression was
performed in the process switching path. Compression performed in the process switching path meant
that packets traversing interfaces that had TCP header compression enabled were queued and passed up
to the process to be switched. This procedure slowed down transmission of the packet, and therefore
some users preferred to fast switch uncompressed TCP packets.
In Cisco IOS Release 12.1, if TCP header compression is enabled, it occurs by default in the
fast-switched path or the CEF-switched path, depending on which switching method is enabled on the
interface.
If neither fast switching nor CEF switching is enabled, then if TCP header compression is enabled, it
will occur in the process-switched path as before.
The Express TCP Header Compression feature reduces network overhead and speeds up transmission of
TCP packets. The faster speed provides a greater benefit on slower links than faster links.
In order for Express TCP Header Compression to work, the following conditions must be in place:
CEF switching or fast switching must be enabled on the interface.
HDLC, PPP, or Frame Relay encapsulation must be configured.
TCP header compression must be enabled.
Command Purpose
Router(config-if)# ip tcp
header-compression
[passive]
Enables TCP header compression.