67 lines
4.2 KiB
HTML
67 lines
4.2 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Packet processing" />
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<meta name="abstract" content="Having a better understanding of packet processing helps you decide how to implement routing functions." />
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<meta name="description" content="Having a better understanding of packet processing helps you decide how to implement routing functions." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Packet processing</title>
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</head>
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<body id="rzajwpp"><a name="rzajwpp"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Packet processing</h1>
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<div><p>Having a better understanding of packet processing helps you decide
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how to implement routing functions.</p>
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<p>The following simplified flow chart shows the logical process that takes
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place when an IP packet (datagram) reaches your iSeries™ server. The actual flow might
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be different, but the outcome should be the same. The following logic only
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describes the default packet processing scenarios. If advanced routing techniques
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are used, packet processing might be slightly different.</p>
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<br /><img src="rzajw523.gif" alt="Packet processing" /><br /><p>First, the destination address in the IP header is compared to all the
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defined addresses on the system. If it is determined that the packet is destined
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for your system, the packet is passed up the IP stack to a higher level software,
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such as TCP, and then to the application that is listening on the destination
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port.</p>
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<p>If the packet is not accepted locally, the next check that is performed
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is the IP forwarding attribute. If IP forwarding is set to *YES, then this
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system is configured to forward packets like a router. If the attribute is
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set to *NO in the TCP/IP attributes or in the PPP profile, the packet is destroyed.</p>
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<p>The destination address of the packet is compared to all the *DIRECT routes
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known to your system. This is done by including the destination address of
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the packet with the subnet mask specified in the *DIRECT routing entries of
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the defined interfaces to determine if the packet is destined for a network
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that is directly attached to this system. Checking is done from the most specific
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routes to the least specific.</p>
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<p>Then, if the iSeries server
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is not directly connected to the remote host, the routing table is searched.
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Once again this is done from the most specific host (subnet mask 255.255.255.255)
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to the least specific different route (subnet mask 0.0.0.0). If a route is
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found, the packet is forwarded to the next hop gateway.</p>
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<p>The last point in the flow chart shows that if no matching routing entry
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is found, the packet is destroyed.</p>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzajwkickoff.htm" title="Are you looking for better ways to route and balance the TCP/IP traffic of your iSeries server?">TCP/IP routing and workload balancing</a></div>
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</div>
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</div>
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</body>
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</html>
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