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Tuesday, August 6, 2013

What is meant by an optimal route?

- For selecting a path or route, a routing metric has to be applied to a number of routes so as to select the best out of them. 
- This best route is called the optimal route with respect to the routing metric used. 
- This routing metric is computed with the help of the routing algorithms in computer networking.
- It consists of information such as network delay, hop count, network delay, load, MTU, path cost, communication cost, reliability and so on.
- Only the best or the optimal routes are stored in the routing tables that reside in the memory of the routers. 
- The other information is stored in either the topological or the link state databases. 
- There are many types of routing protocol and each of them has a routing metric specific to it. 
- Some external heuristic is required to be used by the multi-protocol routers for selecting between the routes determined using various routing protocols. 
For example, the administrative distance is the value that is attributed to all the routes in Cisco routers. 
- Here, smaller distances mean that the protocol is a reliable one. 
- Host specific routes to a certain device can be set up by the local network admin. 
- This will offer more control over the usage of the network along with better overall security and permission for testing. 
- This advantage comes handy especially when it is needed to debug the routing tables and the connections. 

In this article we discuss about the optimal routes. 
- With the growing popularity of the IP networks as the mission critical tools for business, the need for methods and techniques using which the network’s routing posture can be monitored is increasing.
- Many routing issues or even incorrect routing can lead to undesirable effects on the network such as downtime, flapping or performance degradation. 
- Route analytic are the techniques and tools that are used for monitoring the routing in a network. 

The performance of the network is measured using the following 2 factors:
  1. Throughput or the Quantity of service: This includes the amount of data that is transmitted and time it takes to transfer.
  2. Average packet delay or Quality of service: This includes the time taken by a packet to arrive at its destination and the response of the system to the commands entered by the user.
- There is always a constant battle between the fairness and optimality or we can say between quantity of service and quality of service. 
- For optimizing the throughput, the paths existing between the nodes have to be saturated and the response time from source point to destination point must be noticed. 

For finding the optimal routes, we have two types of algorithms namely:
  1. Adaptive Algorithms: These algorithms are meant for the networks in which the routes change in a dynamic manner. Here the information regarding the route to be followed is obtained at the run time itself from adjacent as well as the all other routers. The routes change whenever there is a change in the load, change in the topology and every delta T seconds.
  2. Non – adaptive algorithms: These algorithms the same routes cannot be followed every time. Therefore the measurements that were made for the previous condition cannot be used for the current condition. The routes thus obtained are called static routes and are computed at the boot time.

Finding optimal routes requires following the principle of optimality according to which the optimal path between an intermediate router and the destination router lies on the same route from the source to the destination route. 

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