Summary


Routing is a critical function in the global switched telephone network.
It is important to note that the term dynamic routing used in this chapter refers to dynamic call routing in the telephone network; it should not be confused with dynamic routing in IP networks.
Most dynamic call routing schemes for the telephone network require exchange of link state information—such information exchange does not use flooding; instead separate dedicated channels or a signaling network are used.
Hierarchical routing is a routing method based on hierarchical addressing.
Dynamic routing performs the same function as static routing except it is more robust.
Static routing allows routing tables in specific routers to be set up in a static manner so network routes for packets are set.
Dynamic routing allows routing tables in routers to change as the possible routes change.
Dynamic Non hierarchical Routing commonly known as DNHR can overflow to alternate if needed and also drop call if all alternate paths are busy.
Dynamically Controlled Routing is a routing system controlled by a centralized Network Processor (NP) that provides to the switches an alternative path recommendation for traffic in a network.

Summary


Despite numerous classifications, all dynamic routing schemes have two things in common.
All routing schemes allow at most two links for routing a call, and they all provide trunk reservation.