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			Home &gt; Graph Theory: Networking
					&gt; Telephone Networks
					&gt; Routing Strategies</div>
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    <div id="content"><h1>Routing Strategies</h1>
				<p>
				Routing problems arise when telephone traffic becomes aggregated.
				</p>
				<p>
				Possible protocols for handling networks with local overloading:
				</p>
				<ol><li>
					Collect information about the current traffic at all links,
					calculate the path with lightest traffic, and route the call
					along that path.
					</li><li>
					Base the routing strategy on previously-gathered statistics
					on traffic patterns at all links and time periods. (These
					statistics should be updated periodically).
					</li></ol>
				<p>
				<b>Strategy #2</b> is the universally-accepted strategy
				in real telephone networks.  It turns out that aggregated telephone
				traffic is highly predictable, and telephone links and switches are
				very reliable.  Hence, the approximate load can be pre-computed for
				each pair of switches for every interval of every day, allowing routes
				to be determined <b>in advance</b>.
				</p>
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