Assess Wan Link Resources; Link Utilization - Nortel 1000 Description, Installation And Operation Manual

Assess WAN link resources

Link utilization

For most installations, IP Trunk 3.01 (and later) traffic will probably be
routed over WAN links within the intranet. WAN links are the highest
repeating expenses in the network and they often cause capacity problems in
the network. Unlike LAN bandwidth, which is virtually free and easily
implemented, WAN links, especially inter-LATA and international links,
take time to finance, provision, and upgrade. For these reasons, it is important
to determine the state of WAN links in the intranet before installing the IP
Trunk 3.01 (and later) network.
Each voice conversation, (G.729AB codec, 30 ms payload) consumes 11.2
kbit/s of bandwidth or 18.6 kbit/s with Silence Suppression disabled for each
link that it traverses in the intranet. A DS0 64 kbit/s WAN link would support
5 simultaneous telephone conversations with Silence Suppression enabled, or
2 simultaneous telephone conversations with Silence Suppression disabled.
To start this assessment, obtain a current topology map and link utilization
report of the intranet. A visual inspection of the topology map should reveal
which WAN links are likely to be used to deliver IP Trunk 3.01 (and later)
traffic. Alternately, use the Traceroute tool. See "Measure intranet QoS" on
page 187.
Next, determine the current utilization of those links. Note the reporting
window that appears in the link utilization report. For example, the link
utilization can be averaged over a week, a day, or one hour. To be consistent
with the dimensioning considerations, obtain the busy period (peak hour)
utilization of the trunk. See "IP Trunk 3.01 (and later) traffic engineering" on
page 128. Because WAN links are full-duplex and data services exhibit
asymmetric traffic behavior, obtain the utilization of the link representing
traffic flowing in the heavier direction.
ITG engineering guidelines
IP Trunk Description, Installation, and Operation
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