Use codepoints to assign per-hop behaviors

In the Class of service wizard, you will need to assign a per-hop behavior to your policy. You must determine which codepoints to use, based on your individual network needs. Only you can decide what codepoint schemes make sense for your environment. You need to consider what applications are most important to you and what policies might be assigned higher priority. The most important thing is to be consistent with your markings, so that you get the results you expect. For example, policies that hold similar importance might use similar codepoints so that you get consistent results for those policies. If you are unsure which codepoint to assign, use trial and error. You can create test policies, monitor these policies, and make adjustments accordingly.

The tables in the following sections display the suggested codepoints, which are based on industry standards. Most Internet service providers (ISPs) support the industry-standard codepoints, and you can verify whether your ISP supports these codepoints. Across domains, every ISP must agree to support QoS requests. Your service agreements must be able to give your policies what they request. Verify that you are receiving the amount of service you need. If not, you might waste your resources. QoS policies allow you to negotiate service-levels with your ISP, which might decrease network service costs. You can also create your own codepoints; however, it is not suggested for external use. Your own codepoints might be best used in a testing environment.

Expedited forwarding

Expedited forwarding is one type of per-hop behavior. It is mainly used to provide guaranteed service across a network. Expedited forwarding gives traffic a low-loss, low-jitter, end-to-end service by guaranteeing bandwidth across networks. The reservation is made before the packet is sent. The main goal is to avoid delay and deliver the packet on a timely basis.

Class selector

Class selector codepoints are another type of behavior. There are seven classes. Class 0 gives packets the lowest priority and Class 7 gives packets the highest priority within the class selector codepoint values. This is the most common group of per-hop behaviors, because most routers already use similar codepoints.

Assured forwarding

Assured forwarding is divided into four per-hop behavior classes, each of which has drop precedence levels of low, medium, or high. A drop precedence level determines how likely it is for the packets to be dropped. The classes each have their own bandwidth specifications. Class 1, High gives the policy the lowest priority and Class 4, low gives the policy the highest priority. A low drop level means that the packets in this policy have the lowest chance of being dropped in this particular class level.