Frame Relay Components, part 2

We continue a comprehensive view of all the components you need to know about when using Frame Relay. This time, we include an examination of the differences between Fully Meshed, Partially Meshed, and Hub-and-Spoke networks. Excerpted from Cisco Press' Network Consultants Handbook.

By Cisco Press | Posted Jan 16, 2002
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Network Consultants Handbook - Frame Relay
by Matthew Castelli

Network Consultants Handbook -- Click here to go to publisher's site

Frame Relay Components (Cont'd)

As one would expect, determining the number of Virtual Circuits required for a network configuration is based on the number of end nodes, and the communication requirements, such as fully meshed (all-to-all), partial meshed (some-to-all), or hub-and-spoke (all-to-one), as illustrated by Figure 15-8.

Figure 15-8: Fully Meshed, Partially Meshed, and Hub-and-Spoke Networks
Click image for larger view in a new window
(Click image for larger view in a new window)

In a fully meshed network environment, the number of VCs required can be represented by the following formula:

where N is the number of end nodes in the network. This formula is sometimes referred to as the "N2 Formula" because it is derived from ((N2-N) / 2).

In a partial meshed network environment, the number of VCs required is not easily represented by a mathematical formula. You must consider many variables, the least of which is based on the determination of which end nodes require communication with which other end nodes. It is a fair assumption to estimate that the number of VCs required would fall between those of a fully meshed and those of a hub-and-spoke environment:

where N is the number of end nodes in the network and X is the number of VCs required to support a partially meshed configuration. The following formula can be used as an approximation to determine the number of VCs necessary to support a partial mesh configuration: , where N is the number of network nodes. This formula is useful from a network planning and cost-determination standpoint; however, because partial mesh connectivity is determined by application and user requirements at the end node, an exact number of partial-mesh VCs is almost impossible to determine.

In a hub-and-spoke network environment, the number of VCs required can be represented by the formula [N-1], where N is the number of end nodes in the network.

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