Canonical URL: ; File formats: Plain Text PDF Discuss this RFC: Send questions or comments to [email protected] Differentiated services or DiffServ is a computer networking architecture that specifies a simple In December , the IETF published RFC – Definition of the Differentiated services field (DS field) in the IPv4 and IPv6 headers, which. The type of service (ToS) field is the second byte of the IPv4 header. It has had various In RFC the definition of this entire field was changed. It is now.

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Traffic that exceeds the subscription rate faces a higher probability of being dropped if congestion occurs. Rather than differentiating network traffic based on the requirements of 24774 individual flow, DiffServ operates on the principle of traffic classificationplacing each data packet into one of a limited number of traffic classes.

In practice, however, most networks use the following commonly defined per-hop behaviors:.

DiffServ-aware routers implement per-hop behaviors PHBswhich define the packet-forwarding properties associated with a class of traffic. EF traffic is often given strict priority queuing above all other traffic classes.

Type of service

DiffServ simply provides a framework to allow classification and differentiated treatment. The type of uetf ToS field is the second byte of the IPv4 header. Assured forwarding allows the operator to provide assurance of delivery as long as the traffic does not exceed some subscribed rate. It defined a mechanism for assigning a precedence to each IP packet, as well as a mechanism to request specific treatment such as high throughput, high reliability or low latency, etc.

If a packet is received from a non-DiffServ rffc router that used IP precedence markings, the DiffServ router can still understand the encoding as a Class Selector code point. While DiffServ does recommend a standardized set of traffic classes, [3] the DiffServ architecture does not incorporate predetermined judgments of what types of traffic should rcf given priority treatment.

Rather than using strict priority queuing, more balanced queue servicing algorithms such as fair queuing or weighted fair queuing WFQ are likely to be used. A group of routers that implement common, administratively defined DiffServ policies are referred to as a DiffServ domain. Although precedence field was part of IP version 4, it was never rff.


Under DiffServ, all the policing and classifying is done at the boundaries between DiffServ domains. The premise of Diffserv is that complicated functions such as packet classification and policing can be carried out at the edge of the network by edge routers.

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Modern data networks carry many different types of services, including voice, video, streaming music, web pages and email. Webarchive template wayback links Use American English from April All Wikipedia articles written in American English All articles with unsourced statements Articles with unsourced statements from June In RFC the definition of this entire field was changed.

PHB treatment is achieved by core routers using a combination of scheduling policy and queue management policy. The problem addressed by DiffServ does not exist in a system that has enough capacity to carry all traffic.

RFC – Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers

Each router on the network is then configured to differentiate traffic based on its rc. Retrieved 10 October By using this site, you agree to the Terms of Use and Privacy Policy. Retrieved from ” https: In theory, a network could have up to 64 different traffic classes using the 64 available DSCP values.

A traffic classifier may inspect many different parameters in incoming packets, such as source address, destination address or traffic type and assign individual packets to a specific traffic class.

This is complicated further if a packet crosses two or more Jetf domains before reaching its destination. From a commercial viewpoint this means that it is impossible to sell different classes of end-to-end connectivity to end users, as one provider’s Gold packet may be another’s Bronze.

The Class Selector code points are of the binary form ‘xxx’. For tight control over volumes and type rff traffic in a given class, a network operator may choose not to honor markings at the ingress to the DiffServ domain. In contrast, IntServ is a fine-grainedflow-based mechanism.


The details of how individual routers deal with the DS field is configuration specific, therefore it is difficult to predict end-to-end behaviour. However, a great deal of experimental, research, and deployment work has focused on how to make use of these eight bits, resulting in the current DS field rfcc. The AF behavior group defines 24774 separate AF classes where all have the same priority. That is, in contrast to IntServDiffServ requires no advance setup, no reservation, and no time-consuming end-to-end negotiation for each flow.

Differentiated services or DiffServ is a computer efc architecture that specifies a simple and scalable mechanism for classifying and managing network traffic and providing quality of service QoS on modern IP networks. Typically, DF has best-effort forwarding characteristics. Since no classification and policing is required in the core router, functionality there can then be kept simple. Each IP precedence value can be mapped into a DiffServ class.

Because an overload of EF traffic 22474 cause queuing delays and affect the jitter and delay tolerances within the class, EF traffic is often strictly controlled through admission control, policing and other mechanisms. Should congestion occur between classes, the traffic in the higher class is given priority.

Differentiated services

From Wikipedia, the free encyclopedia. Many of the proposed QoS mechanisms that allowed these services to co-exist were both complex and failed to scale to meet the demands of the public Internet.

Traffic classifiers may honor any DiffServ markings in received packets or may elect to ignore or override those markings. Different PHBs may be defined to offer, for example, low-loss or low-latency service.