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HTML
157 lines
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<meta name="DC.Title" content="Use codepoints to assign per-hop behaviors" />
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<meta name="abstract" content="Quality of service (QoS) uses the recommended codepoints to assign per-hop behaviors to traffic." />
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<meta name="description" content="Quality of service (QoS) uses the recommended codepoints to assign per-hop behaviors to traffic." />
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<title>Use codepoints to assign per-hop behaviors</title>
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</head>
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<body id="rzak8phb"><a name="rzak8phb"><!-- --></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">Use codepoints to assign per-hop behaviors</h1>
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<div><p>Quality of service (QoS) uses the recommended codepoints to assign
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per-hop behaviors to traffic.</p>
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<div class="section"><p>In the Class of service wizard, you will need to assign a per-hop
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behavior to your policy. You must determine which codepoints to use, based
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on your individual network needs. Only you can decide what codepoint schemes
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make sense for your environment. You need to consider what applications are
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most important to you and what policies might be assigned higher priority.
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The most important thing is to be consistent with your markings, so that you
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get the results you expect. For example, policies that hold similar importance
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might use similar codepoints so that you get consistent results for those
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policies. If you are unsure which codepoint to assign, use trial and error.
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You can create test policies, monitor these policies, and make adjustments
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accordingly.</p>
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<p>The tables in the following sections display the suggested
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codepoints, which are based on industry standards. Most Internet service providers
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(ISPs) support the industry-standard codepoints, and you can verify whether
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your ISP supports these codepoints. Across domains, every ISP must agree to
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support QoS requests. Your service agreements must be able to give your policies
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what they request. Verify that you are receiving the amount of service you
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need. If not, you might waste your resources. QoS policies allow you to negotiate
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service-levels with your ISP, which might decrease network service costs.
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You can also create your own codepoints; however, it is not suggested for
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external use. Your own codepoints might be best used in a testing environment.</p>
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</div>
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<div class="section" id="rzak8phb__rzak8ef"><a name="rzak8phb__rzak8ef"><!-- --></a><h4 class="sectiontitle">Expedited forwarding</h4><p>Expedited forwarding
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is one type of per-hop behavior. It is mainly used to provide guaranteed service
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across a network. Expedited forwarding gives traffic a low-loss, low-jitter,
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end-to-end service by guaranteeing bandwidth across networks. The reservation
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is made before the packet is sent. The main goal is to avoid delay and deliver
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the packet on a timely basis.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><caption>Table 1. Recommended codepoints: Expedited
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forwarding</caption><thead align="left"><tr><th valign="top" id="d0e35">Expedited forwarding</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e35 ">101110</td>
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</tr>
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</tbody>
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</table>
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</div>
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<div class="note"><span class="notetitle">Note:</span> There is typically a high cost to receive expedited forwarding
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treatment, so it is not recommended to use this per-hop behavior on a regular
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basis.</div>
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</div>
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<div class="section" id="rzak8phb__rzak8cs"><a name="rzak8phb__rzak8cs"><!-- --></a><h4 class="sectiontitle">Class selector</h4><p>Class selector codepoints
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are another type of behavior. There are seven classes. Class 0 gives packets
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the lowest priority and Class 7 gives packets the highest priority within
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the class selector codepoint values. This is the most common group of per-hop
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behaviors, because most routers already use similar codepoints.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><caption>Table 2. Recommended codepoints: Class selector</caption><thead align="left"><tr><th valign="top" id="d0e55">Class selector</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e55 ">Class 0 - 000000</td>
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</tr>
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<tr><td valign="top" headers="d0e55 ">Class 1 - 001000</td>
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</tr>
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<tr><td valign="top" headers="d0e55 ">Class 2 - 010000</td>
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</tr>
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<tr><td valign="top" headers="d0e55 ">Class 3 - 011000</td>
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</tr>
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<tr><td valign="top" headers="d0e55 ">Class 4 - 100000</td>
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</tr>
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<tr><td valign="top" headers="d0e55 ">Class 5 - 101000</td>
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</tr>
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<tr><td valign="top" headers="d0e55 ">Class 6 - 110000</td>
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</tr>
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<tr><td valign="top" headers="d0e55 ">Class 7 - 111000</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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<div class="section" id="rzak8phb__rzak8af"><a name="rzak8phb__rzak8af"><!-- --></a><h4 class="sectiontitle">Assured forwarding</h4><p>Assured forwarding
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is divided into four per-hop behavior classes, each of which has drop precedence
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levels of low, medium, or high. A drop precedence level determines how likely
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it is for the packets to be dropped. The classes each have their own bandwidth
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specifications. Class 1, High gives the policy the lowest priority and Class
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4, low gives the policy the highest priority. A low drop level means that
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the packets in this policy have the lowest chance of being dropped in this
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particular class level.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><caption>Table 3. Recommended codepoints: Assured forwarding</caption><thead align="left"><tr><th valign="top" id="d0e94">Assured forwarding</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 1, Low - 001010</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 1, Medium - 001100</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 1, High- 001110</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 2, Low - 010010</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 2, Medium - 010100</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 2, High - 010110</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 3, Low - 011010</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 3, Medium - 011100</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 3, High - 011110</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 4, Low - 100010</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 4, Medium - 100100</td>
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</tr>
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<tr><td valign="top" headers="d0e94 ">Assured forwarding, Class 4, High - 100110</td>
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</tr>
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</tbody>
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</table>
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</div>
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</div>
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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="rzak8cos.htm" title="When you create a differentiated service policy or an inbound admission policy, you also create and use a class of service.">Class of service</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><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><a href="rzak8cos.htm" title="When you create a differentiated service policy or an inbound admission policy, you also create and use a class of service.">Class of service</a></div>
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</div>
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</div>
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