Routing protocols

  A routing protocol provides a mechanism for routers to share routing information. These protocols allow routers to pass information between themselves, and update their routing tables. Example of routing protocols are Routing Information Protocol (RIP), Interior Gateway Routing Protocol (IGRP), Enhanced Interior Gateway Routing Protocol (EIGRP) and Open Shortest Path First (OSPF).

 

Routed Protocols

    These protocols are any network layer protocol that allows for the addressing of a host and a destination on a network, such as IP and IPX. Routers are responsible for passing a data packet onto the next router in, if possible an optimal way, based on the destination network address. The definition of and optimal way depends on many things, especially its reliability. With IP, routers on the path between a source and a destination, examine the network part of the IP address to achieve their routing. Only the last router, which is connected to the destination node network, examines the host part of the IP address.

A route can either use static or dynamic routing. These are:

Dynamic Routing

    In dynamic routing, the routers monitor the network, and can change their routing tables based on the current network conditions. The network thus adapts to changing conditions. Unfortunately, this method tends to reveal everything known about an internetwork to the rest of the network. This may be inappropriate for security reasons.

Static Routing

    In static routing, a system administrator sets up a manual route when there is only one route to get to a network. This type of configuring reduces the overhead of dynamic routing. Static routing also allows the internetwork administration to specify the information that is advertised parts of a network.

Default Routing

    These are manually defined by the system administrator and define the path that is taken if there is not a known route for the destination.

   In order to achieve dynamic routing, each router uses a metric for a route to a destination. the route with the lowest metric wins and the router send the data packet onto the next router in the best path. There are many ways to define the best route, these includes:

  Bandwidth

    The data capacity of a link, which is typically defined in bps.

 
  Load

    A measure of the amount of activity on a route.

 
  Delay

    The amount of time that is required to send a packet from the source to a destination.

 
  Reliability

    Relates to the error rate of the link.

 
  Hop Count

    Defined by the number of routers that it takes between the current router and the destination.

 
  Ticks

    Defines the delay of a link by a number of ticks of a clock.

 
  Cost

    An arbitrary value which defines the cost of a link, such as financial expense, bandwidth and so on.