Essay Title: 

Routing Algorithms

April 3, 2016 | Author: | Posted in english, literature and language

An Essay on Routing Algorithms

When routers transport data packets among the nodes of a network , they either rely on a hard-coded body of information on optimal routes , or on an algorithm /protocol that selects optimal routes (best routes for data packets to take ) based on metrics of interest like reliability , the number of hops taken , cost of transmission , delays , and other such measures of routing efficiency (Tanenbaum , 2003 . The approach of using algorithms or protocols is very much if network topology might have a possibility of changing (and it usually does [banner_entry_middle]

change as time passes and more requirements come up . Generally , the algorithms used for moving packets by routers fall into two classes based on how information on network structure is collected and the analysis taken to map out the best route : the distance vector algorithms (also referred to as decentralized routing algorithms ) and the link-state algorithms (or global routing algorithms

Distance vector algorithms are based on the premise that a router should only be concerned about neighboring routers . Routers using this class of algorithms utilize a table that contains the optimal route for each of the possible destinations . All the neighbors of a router are weighed according to metrics such as delay time or number of hops taken , upon which the router caches this information into a table , and proceeds to send this table only to adjacent routers . Table updating is done based on tables received by the router from its neighbors (Kozierok , 2005

Link-state algorithms , by contrast , have the routers in the network use complete information on other routers . They start out by having a router identify all physically connected routers with the use of a packet Having done so , it gathers information on neighboring routers , including their respective IP addresses . After this , important parameters , an example being the delay time , for adjacent routers are taken with the help of so-called echo packets , called such because adjacent routers , upon receiving , bounce the packet back to the sender . The time taken for the packet ‘s round trip is halved to give the delay time After doing so , there is an exchange of information gathered among all the routers in the network . This sharing of information results in all the routers of a network acquiring knowledge about network topology and state . The best route to take is then decided upon with any of a number of shortest path ‘ algorithms , appropriately modified to weigh nodes according to preset metrics . Nodes with lower weight are given priority in this scheme (Kozierok , 2005

In general , both of these types have distinct advantages and disadvantages . The chief caveat of the distance vector class of algorithms is that problems such neighbor table overflow (wherein the router might have to deal with more table data than it usually handles looping (where information passed ends up bouncing back and forth between two nodes when it should not be ) and the so-called count to infinity ‘ problem (a condition where a nonfunctional router is not recognized at… [banner_entry_footer]


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