Nortel Networks NN43001-563 - Manual (Page 115)

Factors that effect the real-time capacity 115
To calculate the average bandwidth, perform the following calculation:
Codec bandwidth from Table 17 "Silence Suppression disabled TLAN
Ethernet and WAN IP bandwidth usage per IP Trunk 3.01 (and later) " (page
113)
x (0.6)
When voice services with multi-channel requirements are extensively used
in an IP Trunk 3.01 (and later) network, such as Conference, Music-on-hold,
and Message Broadcasting, additional voice traffic peaks to the IP network
are generated due to the simultaneous voice-traffic bursts on multiple
channels on the same links.
In those cases, even when Silence Suppression is enabled on the IP
trunk card, Nortel recommends using the more conservative bandwidth
calculations of
Table 17 "Silence Suppression disabled TLAN Ethernet and
WAN IP bandwidth usage per IP Trunk 3.01 (and later) " (page 113) with
Silence Suppression disabled to calculate the portion of the bandwidth
requirement caused by simultaneous voice traffic.
Fax engineering considerations
The fax calculation is based on a 30-byte packet size and a data rate of 64
kbit/s (with no compression) The frame duration (payload) is calculated
by using the equation:
30*8/14400=16.6 ms
where 14,400 bit/s is the modem data rate.
Bandwidth output is calculated by the equation:
108*8*1000/16.6=52.0 kbit/s
Bandwidth output to WAN is:
70*8*1000/16.6=33.7 kbit/s.
Payload and bandwidth output for other packet sizes or modem data rates
must be calculated in a similar manner.
Fax traffic is always one-way. Fax pages sent and fax pages received
generate data traffic to the TLAN subnet. For WAN calculation, only the
larger traffic parcel of the two must be considered.
Nortel Communication Server 1000
IP Trunk Fundamentals
NN43001-563 01.01 Standard
Release 5.0 30 May 2007
Copyright © 2007, Nortel Networks
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