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Engineering Guidelines
142
IP TRUNKING MODELS
Examples of fully-meshed and hierarchical network configuration networks are shown Figure
17 and Figure 18.
Figure 17: Fully-meshed Network
In a fully-meshed network, every node is connected to every other node. The benefit of a
fully-meshed network arrangement is that one, or even more than one, link can go down, and
nodes can still reach each other—there are many alternative routes.
For deployments of 20 nodes or less, the fully meshed model is easy to deploy, but as each
new node is added, there is additional management overhead on every existing unit to add the
new IP trunk. Every node requires N-1 IP trunk connections, so for 20 nodes, there are 380
IP trunks (20 x (20-1))—760 end-points to be programmed.
For larger systems, especially for those with many smaller remote nodes, it may be more
practical to deploy a hierarchical network.
In a hierarchical network, as shown in Figure 18, a central group of core routing controllers are
fully meshed, but only one or two links are required to connect to the remote nodes, or to other
applications. Adding a new node requires only an update at the central group and at the new
remote site.
In the example 20-node system, you might need only 38 IP trunks, with 76 end-points to be
programmed in a hierarchical system. Adding the 21st node would require programming of four
additional IP trunks, compared to 40 for the meshed system.