Chapter 8: Configuring Voip Qos; Configuring Rtp And Rtcp; Configuring Header Compression - Avaya G250 Administration

Chapter 8: Configuring VoIP QoS

The Avaya G250/G350 Media Gateway provides voice services over IP data networks using
VoIP. VoIP is a group of protocols for transmitting and receiving various types of voice data over
an IP network. VoIP includes protocols for transmitting and receiving the following types of
information:
Digitally encoded voice data
●
Call signalling information
●
Call routing information
●
QoS information
●
VoIP uses the RTP and RTCP protocols to transmit and receive digitally encoded voice data.
For more information about configuring RTP and RTCP on the Avaya G250/G350 Media
Gateway, see
You can use many types of telephones and trunks that do not directly support VoIP. The Avaya
G250/G350 Media Gateway translates voice and signalling data between VoIP and the system
used by the telephones and trunks.

Configuring RTP and RTCP

VoIP uses the RTP and RTCP protocols to transmit and receive digitally encoded voice data.
RTP and RTCP are the basis of common VoIP traffic. RTP and RTCP run over UDP and incur a
12-byte header on top of other (IP, UDP) headers. Running on PPP or frame relay, these
protocols can be compressed.

Configuring header compression

Header compression reduces the size of packet headers, thus reducing the amount of
bandwidth needed for data. The header compression method is based on the fact that most of
the header fields remain constant or change in predictable ways throughout the session. Thus,
instead of constantly retransmitting the header, each side keeps a context table of the sessions
(the normal headers), and while sending and receiving packets it replaces the full-length
headers with 1 or 2 bytes CID (context-id) plus unpredictable deltas from the last packet.
Configuring RTP and RTCP on page 201.
Issue 3 February 2007 201