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220 Avaya Application Solutions IP Telephony Deployment Guide
Table 41: Payload size per packet on page 220 is populated using this formula, and provides
the payload 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 Table 42:
Bandwidth
requirements for media streams.
Note that the entries in Table 42
correspond with a single (unidirectional) media stream. As we
will see in the following example, the entries in Table 42
are not multiplied by the average
number of simultaneous streams, but rather by a much larger number that represents the 99.9th
percentile for the simultaneous number of streams.
Table 41: Payload size per packet
Packet
“size”
(ms)
G.711
(bits)
G.729
(bits)
10 640 80
20 1280 160
30 1920 240
60 3840 480
Table 42: Bandwidth requirements for media streams
Packet “size” (ms) G.711 (kbps) G.729 (kbps)
10 110.4 54.4
20 87.2 31.2
30 79.5 23.5
60 71.7 15.7