R2511-HP MSR Router Series Voice Command Reference(V5)

7
Network bandwidth = Bandwidth of the media stream × packet length/bytes coded in a time unit.
Because IPHC compression is affected significantly by network stability, it cannot achieve high efficiency
unless the line is of high quality, the network is very stable, and packet loss does not occur or seldom
occurs. When the network is unstable, IPHC efficiency drops drastically. With best IPHC performance,
the IP (RTP) header can be compressed to 2 bytes. If the PPP header is compressed at the same time, a
great deal of media stream bandwidth can be saved. The following table shows the best IPHC
compression efficiency of codec algorithms with a packet assembly interval of 30 milliseconds.
Table 10 Compression efficiency of IPHC+PPP header
Codec
Bytes
coded in
a time
unit
Before com
p
ression After IPHC+PPP com
p
ression
Packet length
(IP+PPP) (bytes)
Network
bandwidth
(IP+PPP)
Packet length
(IP+PPP) (bytes)
Network
bandwidth
(IP+PPP)
G.729 30 76 20.3 kbps 34 9.1 kbps
G.723r63 24 70 18.4 kbps 28 7.4 kbps
G.723r53 20 66 17.5 kbps 24 6.4 kbps
G.726r16 60 106 28.3 kbps 64 17.1 kbps
G.726r24 90 136 36.3 kbps 94 25.1 kbps
G.726r32 120 166 44.3 kbps 124 33.1 kbps
G.726r40 150 196 52.3 kbps 154 41.1 kbps
Two communication parties can communicate correctly only if they share some identical
coding/decoding algorithms. If the codec algorithm between two connected devices is inconsistent, or
the two devices share no common coding/decoding algorithms, the calling will fail.
Examples
# Configure to use g723r53 coding/decoding algorithm first, then the g729r8.
<Sysname> system-view
[Sysname] voice-setup
[Sysname-voice] dial-program
[Sysname-voice-dial] entity 10 voip
[Sysname-voice-dial-entity10] compression 1st-level g723r53
[Sysname-voice-dial-entity10] compression 2nd-level g729r8
default entity compression
NOTE:
The default entity compression command takes no effect on IVR voice entities.
Use default entity compression to specify the default global codecs and their priority levels.
Use undo default entity compression to restore the default.
Syntax
default entity compression { 1st-level | 2nd-level | 3rd-level | 4th-level } { g711alaw | g711ulaw |
g723r53 | g723r63 | g726r16 | g726r24 | g726r32 | g726r40 | g729a | g729br8 | g729r8 }
undo default entity compression { 1st-level | 2nd-level | 3rd-level | 4th-level }