What is Routing? Explain the working principle of distance vector routing protocol with a proper example.

Subject Computer Network
NU Year Set: 6.(d) Marks: 1+6=7 Year: 2017

Routing refers to establishing the routes that data packets take on their way to a particular destination. This term can be applied to data traveling on the Internet, over 3G or 4G networks, or over similar networks used for telecom and other digital communications setups. Routing can also take place within proprietary networks.


Distance Vector routing protocols use frequent broadcasts (255.255.255.255 or FF:FF:FF:FF) of their entire routing table every 30 sec. on all their interfaces in order to communicate with their neighbours. The bigger the routing tables, the more broadcasts. This methodology limits significantly the size of network on which Distance Vector can be used.

Routing Information Protocol (RIP) and Interior Gateway Routing Protocol (IGRP) are two very popular Distance Vector routing protocols. You can find links to more information on these protocols at the bottom of the page. (That's if you haven't had enough by the time you get there !)

Distance Vector protocols view networks in terms of adjacent routers and hop counts, which also happens to be the metric used. The "hop" count (max of 15 for RIP, 16 is deemed unreachable and 255 for IGMP), will increase by one every time the packet transits through a router.

So the router makes decisions about the way a packet will travel, based on the amount of hops it takes to reach the destination and if it had 2 different ways to get there, it will simply send it via the shortest path, regardless of the connection speed. This is known as pinhole congestion.

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