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378
ITG Engineering Guidelines
553-3001-202 Standard 1.00 April 2000
ITG traffic engineering
To design a network is to size the network so that it can accept some
calculated amount of traffic. The purpose of the ITG network is to deliver
voice traffic meeting the QoS objectives. Since traffic determines network
design, the design process needs to start with the process of obtaining offered
ITG traffic forecast. The traffic forecast will drive:
• WAN requirements
• ITG hardware requirements
• T-LAN requirements
Use
of Ethernet and WAN bandwidth
Table 5 on page 77 lists the Ethernet and WAN bandwidth use of ITG ports
with different codecs with silence suppression enabled, and Table 6 on
page 80 lists the use with silence suppression disabled. One port is a channel
fully loaded to 36 CCS, where one CCS (Centi-Call-Second) is a
channel/circuit being occupied 100 seconds. 36 CCS is a circuit occupied for
a full hour. To calculate the bandwidth requirement of a route, the total route
traffic should be divided by 36 CCS and multiplied by the bandwidth use to
get the data rate requirement of that route. All traffic data must be based on
the busy hour of the busy day.
Note that to calculate resource requirements (ITG ports and T-LAN/WAN
bandwidth), traffic parcels are summarized in different ways:
1 Add all sources of traffic for the ITG network, e.g., voice, fax sent, fax
received, together to calculate ITG port and T-LAN requirements.
2 For data rate requirement at each route, the calculation is based on each
destination pair.
3 For fax traffic on a WAN, only the larger of either the fax-sent or
fax-received traffic is to be accounted for.
The engineering procedures for T-LAN and WAN are different. The
following calculation procedure is for T-LAN (the modification required for
WAN engineering is included in these procedures).