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


 
Configuring IP Multicast Routing
Configuring RTP Header Compression
IPC-433
Cisco IOS IP Configuration Guide
By default, for PPP or HDLC encapsulation, the software allows 32 RTP header compression
connections (16 calls). This default can be increased to a maximum of 1000 RTP header compression
connections on an interface.
To change the number of compression connections supported, use the following command in interface
configuration mode:
See the “RTP Header Compression Examples” section later in this chapter for an example of how to
change the number of header compression connections.
Enabling Express RTP Header Compression
Before Cisco IOS Release 12.0(7)T, if compression of TCP or RTP headers was enabled, compression
was performed in the process-switching path, which meant that packets traversing interfaces that had
TCP or RTP 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 and RTP packets.
With Release 12.1 and later releases, if TCP or RTP header compression is enabled, it occurs by default
in the fast-switched path or the Cisco Express Forwarding-switched (CEF-switched) path, depending on
which switching method is enabled on the interface.
If neither fast switching nor CEF switching is enabled, if enabled, RTP header compression will occur
in the process-switched path as before.
For examples of RTP header compression, see the sections “Express RTP Header Compression with PPP
Encapsulation Example” and “Express RTP Header Compression with Frame Relay Encapsulation
Example.”
The Express RTP and TCP Header Compression feature has the following benefits:
It reduces network overhead.
It speeds up transmission of TCP and RTP packets. The faster speed provides a greater benefit on
slower links than faster links.
One restriction affects Multilink PPP (MLP) interfaces that have link fragment and interleave (LFI). In
this case, if RTP header compression is configured, RTP packets originating on or destined to the router
will be process switched. Transit traffic will be fast switched.
The CEF and fast-switching aspects of this feature are related to these documents:
Cisco IOS Switching Services Configuration Guide
Cisco IOS Switching Services Command Reference
Command Purpose
Router(config-if)# frame-relay ip rtp
compression-connections number
Specifies the maximum number of RTP header compression
connections supported on the Frame Relay interface.
Router(config-if)# ip rtp
compression-connections number
Specifies the total number of RTP header compression connections
supported on the PPP or HDLC interface.