Hierarchical networks are capable of handing heavy traffic where required, and at the same time use minimal number of trunk groups. Three methods are used for deciding on the route for a particular connection:
1. Right – through routing
2. Own-exchange routing.
3. Computer-controlled routing.
In right-through routing the originating exchange determines the complete route from source to destination. No routing decisions are taken at the intermediate routes. In the absence of a computer, only a predetermined route can be chosen by the originating exchange. However, there may be more than one predetermined route and the originating node may select one out of these, based on certain like time of the day, even distribution of traffic etc.
Own-exchange routing or distributed routing allows alternative routes to be chosen at the intermediate nodes. Thus the strategy is capable of responding to changes in traffic loads and network configurations. Another advantage of distributed routing is that when new exchanges are added, modifications required in the switch are minimal.
Computers are used in network with common channel signaling (CCS) features. In CCS, there is a separate computer-controlled signaling network. With computers in position, a number of sophisticated route selection methods can be implemented. Computer based routing is a standard feature in data networks.