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Table 36: Payload size per packet
size per packet (expressed in bits) as a function of packet "size" (that is, ms per packet) and
codec.
Note that the number of bits of payload per packet depends on the packet "size," but it is
independent of the "sizes" of the individual frames that are contained in that packet. For
example, a packet "size" of 60 ms could be referring to six 10-ms frames per packet, or three
20-ms frames per packet, or two 30-ms frames per packet, and so on. Presently, the most
commonly used packet "sizes" are 20 ms. Both G.711 and G.729 codecs typically use two
10-ms frames per packet.
As stated earlier, there is an overhead of 464 bits per packet. So, the bandwidth (expressed in
kbps) that is associated with a unidirectional media stream (assuming no Silence Suppression
is used) is augmented from 64 kbps and 8 kbps (for G.711 and G.729, respectively) to account
for this overhead. The results of this exercise are provided in
requirements for media
Table 37: Bandwidth requirements for media streams
Note that the entries in
will see in the following example, the entries in
number of simultaneous streams, but rather by a much larger number that represents the 99.9th
percentile for the simultaneous number of streams.
is populated using this formula, and provides the payload
Table 36: Payload size per packet
Packet
G.711
"size"
(bits)
(ms)
10
640
20
1280
30
1920
60
3840
streams.
Packet "size" (ms)
10
20
30
60
Table 37
correspond with a single (unidirectional) media stream. As we
G.729
(bits)
80
160
240
480
Table 37: Bandwidth
G.711 (kbps)
G.729 (kbps)
110.4
54.4
87.2
31.2
79.5
23.5
71.7
15.7
Table 37
are not multiplied by the average
Resource sizing
Issue 3.4.1 June 2005
181
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