Discuss different Routing plan adopted in a Telephone network.

Hierarchical networks are able of handing heavy traffic where needed, and at similar time use minimal number of trunk groups. Three ways are used for deciding on the route for an exact connection:

1. Right - through routing

2. Own-exchange routing.

3. Computer-controlled routing.

In right-through routing the originating exchange find out the complete route from source to destination. At the intermediate routes, no routing decisions are taken. In the absence of a computer, simply a predetermined route can be selected by the originating exchange. Though, there may be more than one predetermined route and the originating node may decide on one out of these, based on certain as time of the day, even distribution of traffic and so on.

Own-exchange routing or distributed routing permits alternative routes to be selected at the intermediate nodes. Therefore the strategy is able of responding to changes in traffic loads and network configurations. The other advantage of distributed routing is that while new exchanges are added, modifications needed in the switch are minimal.

Computers are utilized in network with common channel signaling (CCS) features. There is a separate computer-controlled signaling network, in CCS. With computers in position, a number of difficult route selection methods can be implemented. In data networks, computer based routing is a standard feature.