Nortel Networks NN43001-563 - Manual (Page 123)

Assess WAN link resources 123
The third step is to assess how much spare capacity is available. Enterprise
intranets are subject to capacity planning policies that ensure capacity use
remains below some determined utilization level. For example, a planning
policy might state that the utilization of a 56 kbit/s link during the peak hour
must not exceed 50%; for a T1 link, the threshold is higher, for instance,
80%. The carrying capacity of the 56 kbit/s link would be 28 kbit/s and for
the T1, 1.2288 Mbit/s. In some organizations the thresholds can be lower
than those used in this example; in the event of link failures, there must
be spare capacity to re-route traffic.
Some WAN links can be provisioned on top of Layer 2 services such as
Frame Relay and ATM; the router-to-router link is actually a virtual circuit,
which is subject not only to a physical capacity, but also to a "logical
capacity" limit. Obtain, in addition to the physical link capacity, the QoS
parameters, especially the Committed Information Rate (CIR) for Frame
Relay and Maximum Cell Rate (MCR) for ATM.
The difference between the current capacity and its allowable limit is
the available capacity. For example, a T1 link utilized at 48% during the
peak hour, with a planning limit of 80%, had an available capacity of
approximately 492 kbit/s.
Estimate network loading caused by IP Trunk 3.01 (and later) traffic
At this point, enough information has been obtained to "load" the IP Trunk
3.01 (and later) traffic on the intranet.
Figure 25 "Calculate network load
with IP Trunk 3.01 (and later) traffic" (page 124) illustrates how this is done
on an individual link.
Nortel Communication Server 1000
IP Trunk Fundamentals
NN43001-563 01.01 Standard
Release 5.0 30 May 2007
Copyright © 2007, Nortel Networks
.