
94 Networking
P0937663 02.0
Table 11 Bandwidth Requirements per BCM Gateway port for half-duplex links.
Bandwidth Requirements on Full Duplex Links
Table 12 on page 95 provides bandwidth requirements for normal two-way voice calls on a
full-duplex link for a variety of link protocols, codec types and payload sizes. Bandwidths for
full-duplex links are stated in terms of the individual transmit and receive channels. For instance a
64 kbits full duplex link (e.g. a DS0 on T1 link) has 64 kbits in the transmit direction and 64 kbits
in the receive direction.
With no silence suppression, both the transmit path and the receive path continuously transmit
voice packets. Enabling silence suppression on full-duplex links reduces the average bandwidth.
However, since transmit and receive paths use separate channels, the peak bandwidth per call per
channel does not change. Therefore, peak bandwidth requirements per channel (Rx or Tx) per call
on a full-duplex link is::
(Full Duplex links, With or Without Silence Suppression)
Codec
Type
Payload
Size Ethernet B/W
2
PPP B/W FR B/W
No SP
Silence
Suppression No SP
Silence
Suppression No SP
Silence
Suppression
peak peak Avg peak peak Avg peak peak Avg
ms kbit/s kbit/s kbit/s kbit/s kbit/s kbit/s kbit/s kbit/s kbit/s
G.711
(
64 kb/s)
10 233.6 233.6
3
233.6
3
195.2 195.2
3
195.2
3
206.4 206.4
3
206.4
3
20 180.8 180.8
3
180.8
3
161.6 161.6
3
161.6
3
167.2 167.2
3
167.2
3
30 163.2 163.2
3
163.2
3
150.4 150.4
3
150.4
3
154.2 154.2
3
154.2
3
G.729
(8 kb/s)
10 121.6 60.8 60.8 83.2 41.6 41.6 94.4 47.2 47.2
20 68.8 34.4 34.4 49.6 24.8 24.8 55.2 27.6 27.6
30 51.2 25.6 25.6 38.4 19.2 19.2 42.2 21.1 21.1
G.723.1
(6.3 kb/s)
30 48.0 24.0 24.0 35.2 17.6 17.6 39.0 19.5 19.5
G.723.1
(5.3 kb/s)
30 45.8 22.9 22.9 33.0 16.5 16.5 36.8 18.4 18.4
Notes:
1) Gray background indicates payload sizes used by Business Communications Manager 2.5 for transmission. Other values
listed indicate payload sizes that BCM can receive.
2) Ethernet bandwidth includes the 14 byte Ethernet frame overhead plus a 12 byte inter-frame gap.
3) G.711 does not support silence suppression.
Peak Bandwidth per channel per call 2 Continuous Transmission Rate()=
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