RTP
Issue 3.4.1 June 2005
327
Table 76: Test call (20ms-packets) results
shows the results with and without RTP header
compression. Note that these are rough measurements.
For each codec, there was an attempt to verify that the audio packets were received intact. This
was done by spot checking the audio packets before and after compression, using two Sniffer
protocol analyzers. For every codec except G.711, the RTP header and payload were identical
before and after compression. With G.711, however, the received packets had the PADDING
flag set in the RTP header, although the flag was not set when the packets were transmitted.
The PADDING flag indicates the presence of padding octets at the end of the RTP payload,
which cannot be true for G.711.
Configuration
To configure RTP header compression on a Cisco router:
1. Specify the number of RTP connections that can be compressed (cache allocation). In
interface configuration mode, the command is
ip rtp compression-connections
<number>
, where
●
The default for
<number>
is 32, and each call requires two connections.
●
The configurable range is 3 to 256 for PPP and HDLC using IOS v11.3 and later.
●
The configurable range is 3 to 1000 for PPP and HDLC using IOS v12.0(7)T and later.
●
For Frame Relay, the value is fixed at 256.
Table 76: Test call (20ms-packets) results
Codec
Payload
bytes
per packet
Packets
per
second
Avg WAN BW
consumption (kbps)
%
reduction
without
compressi
on
with
compressi
on
G.711
(64 kbps)
160
50
84
68.5
~18%
G.729A
(8 kbps)
20
50
27.5
13
~53%
G.723.1
(5.3 kbps)
20
33
18
9
~50%
G.723.1
(6.3 kbps)
24
33
19
10
~47%
Summary of Contents for Application Solutions
Page 1: ...Avaya Application Solutions IP Telephony Deployment Guide 555 245 600 Issue 3 4 1 June 2005 ...
Page 20: ...About This Book 20 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 21: ...Issue 3 4 1 June 2005 21 Section 1 Avaya Application Solutions product guide ...
Page 22: ...22 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 106: ...Call processing 106 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 124: ...Avaya LAN switching products 124 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 139: ...Issue 3 4 1 June 2005 139 Section 2 Deploying IP Telephony ...
Page 140: ...140 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 186: ...Traffic engineering 186 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 204: ...Security 204 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 228: ...Avaya Integrated Management 228 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 274: ...Reliability and Recovery 274 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 275: ...Issue 3 4 1 June 2005 275 Section 3 Getting the IP network ready for telephony ...
Page 276: ...276 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 356: ...Network recovery 356 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 366: ...Network assessment offer 366 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 367: ...Issue 3 4 1 June 2005 367 Appendixes ...
Page 368: ...Appendixes 368 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 394: ...Access list 394 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 414: ...DHCP TFTP 414 Avaya Application Solutions IP Telephony Deployment Guide ...