H3C Technologies H3C MSR 50 - Manual (Page 623)

238
NOTE:
•
The packet assembly interval is the duration to encapsulate information into a voice packet.
• Bytes coded in a time unit = packet assembly interval × media stream bandwidth.
• Packet length (IP) = IP header + RTP header + UDP header + voice information length = 20+12+8+data.
• Packet length (IP+PPP) = PPP header + IP header + RTP header + UDP header + voice information length
= 6+20+12+8+data.
• 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 227 Compression efficiency of IPHC+PPP header
Codec
Bytes
coded in
a time
unit
Before compression After IPHC+PPP compression
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 17.5 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
Other parameters
Other parameters are some optional parameters, such as number selection priority, dial prefix, called
number sending mode, and DTMF transmission mode. For the description of these parameters,
see Configuring other parameters of a local number and Configuring other parameters for a call route .
Configuring advanced settings of a local number
Configuring coding parameters of a local number
Select Voice Management > Local Number from the navigation tree, and then click the icon of the
local number to be configured to access the advanced settings configuration page.