72 lines
5.0 KiB
HTML
72 lines
5.0 KiB
HTML
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<meta name="DC.Title" content="Setting priorities: How to handle the classes" />
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<meta name="abstract" content="After traffic is classified, differentiated service also requires a per-hop behavior to define how to handle the traffic." />
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<title>Setting priorities: How to handle the classes</title>
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<body id="rzak8handle"><a name="rzak8handle"><!-- --></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">Setting priorities: How to handle the classes</h1>
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<div><p>After traffic is classified, differentiated service also requires
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a per-hop behavior to define how to handle the traffic.</p>
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<p>The server uses bits in the IP header to identify an IP packet's level
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of service. Routers and switches allocate their resources based on the per-hop
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behavior information in the IP header's type of service octet field. The
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type of service octet field was redefined in the Request for Comments (RFC)
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1349 and OS/400<sup>®</sup> V5R1
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operating system. A per-hop behavior is the forwarding behavior that a packet
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receives at a network node. It is represented by a value known as a <em>codepoint</em>.
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Packets can be marked either at the server or at other parts of the network,
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such as a router. For a packet to retain the service requested, every network
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node must be differentiated service (DiffServ)-aware. That is, the equipment
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must be able to enforce per-hop behaviors. To enforce per-hop behavior treatment,
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the network node must be able to use queue scheduling and outbound priority
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management. See the <a href="rzak8conditioners.htm">Traffic conditioners</a> topic for
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more information about what it means to be DiffServ-aware.</p>
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<p>If your packet passes through a router or switch that is not DiffServ-aware,
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it will lose its level of service at that router. The packet is still handled,
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but it might experience unexpected delay. On your iSeries™ server, you can use the pre-defined
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per-hop behavior codepoints or you can define your own codepoint. It is not
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recommended that you create your own codepoints for use outside your private
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network. If you do not know which codepoints to assign, review <a href="rzak8phb.htm">Use codepoints to assign per-hop behaviors</a> topic.</p>
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<p>Unlike integrated service, differentiated service traffic does not require
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a reservation or per-flow treatment. All traffic placed in the same class
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is treated equally.</p>
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<p>Differentiated service can also be used to throttle traffic leaving a server.
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This means that your iSeries server really uses differentiated service
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to limit performance. Limiting a less-critical application allows a mission-critical
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application to exit your private network first. When you create a class of
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service for this policy, you are asked to set various limits on your server.
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The performance limits include token bucket size, peak rate limit, and average
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rate limit. The help topics within the quality of service (QoS)
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function of iSeries Navigator
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gives you more specific information about these limits. </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="rzak8diffserv.htm" title="This is the first type of outbound bandwidth policy you can create on your server. Differentiated service divides your traffic into classes. To carry out a differentiated service policy, you need to determine how you want to classify your network traffic and how to handle the different classes.">Differentiated service</a></div>
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</div>
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