112 ITG engineering guidelines
Tocalculate the bandwidth requirement of a route, divide the total route
traffic by 36 CCS and multiply bythe bandwidth use. All traffic data must be
based on the busy hour ofthe busy day.
Tocalculate resource requirements (IP Trunk 3.01 (and later) ports and
TLAN subnet/WAN bandwidth), traffic parcels are summarized in different
ways:
1. Add all sources of traffic for the IP Trunk3.01 (and later) network,
such as voice, faxessent, and faxes received, together to calculate IP
Trunk3.01 (and later) por t requirements and TLAN subnet bandwidth
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 the TLAN subnet and WAN are different.
The followingcalculation procedure is for the TLAN subnet. Themodification
required for WANengineer ing is included in these procedures.
ATTENTION
IMPORTANT
Voicepackets must have priority over data packets.
When the WAN route prioritizes voice traffic overdata traffic,the route bandwidth
can be engineered to 90% loading level; otherwise, a WANroute with bandwidth
of 1.536 Mbit/s or more can onlybe loaded up to 80%. A smaller WANpipe (64
kbit/s) is recommended to a loading of 50%.
In Table17 "Silence Suppression disabled TLAN Ethernet and WANIP
bandwidth usage per IP Trunk3.01 (and later) "(page 113), the first WAN
bandwidth is without Frame Relay or ATMoverhead.
The Frame Relay overheadis 8 bytes (over IP packet).
The LLC SNAP (Link Layer Control SubNetwork Attachment Point)and
AAL5 overhead for ATMis 16 bytes (over IP packet).
IP packet size over53 bytesrequires two ATM cells, over 106 bytes requires
three ATMcells, and so on. Within the same number of cells, the bandwidth
requirements are the same for packets with different sizes.
TM 3.1 input for fax is in bytes, ranging from 20 to 48;
30 bytes is the default.This differsfrom voice applications where payload
size is the input.
Nortel Communication Server 1000
IP TrunkFundamentals
NN43001-563 02.01 Standard
Release 5.5 21 December 2007
Copyright© 2007, Nor tel Networks
.