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ITG Engineering Guidelines
Table 6
Silence suppression disabled T-LAN Ethernet and WAN IP bandwidth usage per ITG port
Codec
Multi -
frame
Codec type
duration
in ms
(payload)
(one way)
G.711
10
(64 kbit/s)
20
30
G.729AB/
10
G.729A
20
(8kbit/s)
30
30
G.723.1
(5.3
kbit/s)
G723.1
30
(6.3
kbit/s)
T.30/T.38
G3 Fax
16.6
Modem
25
14.4
Kbit/s
Note 1: Based on voice multiframe encapsulation for Realtime Transport Protocol per H.323 V2.
Note 2: The bolded rows contain the default payload/packet size for each codec in the MAT.
Note 3: T-LAN data rate is the effective Ethernet bandwidth consumption.
Note 4: T-LAN kbit/s for voice traffic = 2*Ethernet frame bits*8/frame duration in ms
Note 5: WAN kbit/s for voice traffic = IP packet bytes*8/frame duration in ms
Note 6: 24 ports per card for all codecs
Note 7: Overhead (RTP/UDP header + IP header) of packets over the voice payload multiframe is 40 bytes;
overhead of Ethernet frame over IP packet is 26 bytes.
Note 8: An Interframe gap is not included in the above bandwidth calculation, because of the low probability
of occurring in this type of application.
553-3001-202
Standard 1.00
Voice/fax
payload
IP voice
Multi -
packet in
frame
bytes
in bytes
(one way)
(one way)
80
240
160
400
240
560
10
100
20
120
30
140
20
120
24
128
30
70
30
70
April 2000
Ethernet
Bandwidth
voice
use on
packet in
T-LAN in
bytes
kbit/s
(one way)
(two way)
292
233.6
452
180.8
612
163.2
152
121.6
172
68.8
192
51.2
172
45.8
180
48.0
96
46.3
96
30.7
WAN with
Bandwidth
Frame
use on
Relay
WAN in
overhead
kbit/s
in kbit/s
(one way)
(one-way)
96.0
102.4
80.0
83.2
74.6
76.6
40.0
46.4
24.0
27.2
18.6
20.8
16.0
18.1
17.0
19.2
33.7
37.5
22.4
25.0
WAN with
ATM
overhead
in kbit/s
(one-way)
127.2
106.0
98.9
84.8
42.4
28.3
28.3
28.3
50.9
33.9
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