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			Home &gt; Graph Theory: Networking
					&gt; The Internet
					&gt; Link-State Routing</div>
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        <a class="toc_link" href="page30.xml">Distance-Vector Routing</a>
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        <a class="toc_link" href="page33.xml">Link-State Routing</a>
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    <div id="content"><h1>Link-State Routing</h1>
				<h2>Which Method Is Better?: Distance-Vector vs. Link-State</h2>
				<p>
				When should distance-vector be used, and when should link-state
				routing be used?  There are arguments for and against each approach.
				</p>
				<p>
				The choice of strategy should be based on the properties of the given
				network, the main parameter being how frequently nodes are expected to
				go down or come up.
				</p>
				
				<h2>Stability:</h2>
				<ol><li>
					It is generally thought that link-state algorithms are more stable,
					because each router &quot;knows&quot; the entire network.
					</li><li>
					On the other hand, if the network is highly dynamic, it is possible
					for link-state algorithms to create routing loops while new topology
					information is being disseminated.
					</li></ol>
				<h2>Running Time:</h2>
				<ol><li>
					Link-state algorithms converge more quickly than distance-vector
					algorithms.
					</li><li>
					In practice, the time for convergence depends on the network graph,
					the load on the routing protocol, and the exact sequence of link
					failure and recovery.
					</li></ol>
				<h2>Overhead:</h2>
				<ol><li>
					Much of the overhead in link-state routing comes from the subroutine
					that prevents corruption of the LSP database in case of node and/or
					link failure. The distance-vector algorithm does not have this
					overhead.
					</li></ol>
				<h2>Memory:</h2>
				<ol><li>
					Typically, link-state implementations require more memory than
					distance-vector implementations.
					</li></ol>
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					<b><i>Conclusion</i></b>
					
					<p>
					There is no clear winner between these two strategies, especially
					because for every positive feature of one protocol, a modification can
					be made to the other to make it competitive again.
					</p>
					
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