TABLE OF CONTENTS This chapter addresses core capacity planning and how traffic engineering can be used as a tool to make more efficient use of network capacity.
Capacity planning of the core network is the process of ensuring that sufficient bandwidth is provisioned such that the committed core network SLA targets of delay jitter, loss, and availability can be met. In the core network where link bandwidths are high and traffic is highly aggregated, the SLA requirements for a traffic class can be translated into bandwidth requirements, and the problem of SLA assurance can effectively be reduced to that of bandwidth provisioning. Hence, the ability to assure SLAs is dependent upon ensuring that core network bandwidth is adequately provisioned, which is in turn dependent upon core capacity planning.
The simplest core capacity planning processes use passive measurements of core link utilization statistics (i.e. as described in Chapter 5, Section 5.2) and apply rules of thumb, such as upgrading links when they reach 50% average utilization, or some other such general utilization target. The aim of such simple processes is to attempt to ensure that the core links are always significantly over-provisioned relative to the offered average load, on the assumption that this will ensure that they are also sufficiently over-provisioned relative to the peak load, that congestion will not occur, and hence the SLA requirements will be met. There are, however, two significant consequences of such a simple approach. Firstly, without a network-wide understanding of the traffic demands,...
