Network Addresses

Protocols that are routable differ from protocols that are non routable.
Routable protocols contain information in each packet relating to the network address of the source and destination nodes.
This kind of information allows a router to forward the packet to a particular network rather than a particular node.
Different protocols address networks using a variety of naming schemes.
However they rely on each network having a unique address.
Choosing Paths
A routing algorithm is used to build a routing table for forwarding packets.

They are of two types:
Non-adaptive

The choice of route has to be manually configured into router.

This is also known as 'static' routing.
Adaptive

Routing information is obtained from other routers.

Routing decisions are based on traffic levels connection speeds and number of hops or administrator-preset costs.

This is known as dynamic routing.