Toshiba Strata CIX40 General Description Manual page 196

Appendix — Specifications
Strata Net IP and IPT Bandwidth Requirements
When sharing voice and data on the same network segment, the data will cause some jitter in voice
communications, especially on slower segments.
jitter assuming a worst case data packet size of 1500 bytes (Maximum Transmission Unit (MTU) =
1500) based on a segment's bandwidth. This also requires that the routers connecting the segment
through the WAN support Diffserv.
Note A router that doesn't support Diffserv may stack multiple data packets together increasing
Class definition categories are shown in
Table 49
independent of the amount of voice traffic.
So the amount of bandwidth that is required on a segment to support a specific number of calls is
the sum of the number of channels multiplied by the bandwidth for the selected CODEC and
interval, plus the bandwidth required for the selected number of busy hour call attempts. And the
jitter is determined by the bandwidth of the WAN segment.
Example: If you want to support 4 calls using the G.711 CODEC with a 20 msec. interval, this
requires 4 x 88 kbps = 352 kbps of bandwidth. In addition, to support 1000 busy hour call
attempts, 6 kbps must be added for a total of 358 kbps. If only voice is going to be carried on the
segment, then a 384 kbps segment (6 B-channels) is sufficient.
If voice and data are going to be mixed on the segment, then at least 25% (89.5 kbps) should be
added, or more, based on the amount of data traffic desired. In this case, a total of 447 kbps will be
required which would best be supported by a 512 kbps segment (8 B-channels). This would result
in an expected jitter of 20 ms in the voice traffic.
When using the MEGACO+ protocol with IPT telephones, keep alive packets are exchanged
between the IPU and the phones. This traffic amounts to 3 kbps per phone.
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the jitter perhaps indefinitely. And the voice quality will be indeterminate.
Table 47 Strata Net IP Jitter on Mixed Voice and Data WAN
No. of
Bandwidth
B-Channels
(kbps)
of WAN
2 128
4 256
6 384
8 512
24 1536
Table 48
Class
Excellent
Good
Fair
Poor
shows the amount of bandwidth required for setting up and tearing down calls
Table 49
Traffic Rate
1. BHC = Busy Hour Call Attempts
Table 47
Time to
transmit max.
MTU (ms)
93.75
46.88
23.44
15.63
1.00
Table 48.
Strata Net IP Class Definitions
Delay (ms)
< 20
< 50
< 100
< 200
Strata Net IP Bandwidth
Required for Call Setup
Required
1
Bandwidth
(BHCA )
1000
2000
4000
6000
shows calculations of the amount of
Expected
Class
Jitter (ms)
100 Poor
50 Fair
30 Fair
20 Good
1 Excellent
Jitter (ms)
< 10
< 20
< 50
< 100
6
12
23
36
Strata CIX General Description 12/07