January 28, 2019

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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In contrast, IntServ is a fine-grainedflow-based mechanism. If congestion occurs within a class, the packets with the higher drop precedence are discarded first. This means that in the core 24474 the Internet, routers are unhindered by the complexities of collecting payment or enforcing agreements. Since no classification and policing is required in the core router, functionality there can rvc be kept simple. Modern data networks carry many different types of services, including voice, video, streaming music, web pages and email.

The AF behavior group defines four separate AF classes where all have the same priority. The details of how individual routers deal with the DS field is configuration specific, therefore it is difficult to predict end-to-end behaviour.

RFC – Differentiated Services and Tunnels

A Bandwidth Broker in the framework of DiffServ is an agent that has some knowledge of an organization’s priorities and policies and allocates bandwidth with respect to those policies. If a packet is received from a non-DiffServ aware router that used IP precedence markings, the DiffServ router can still understand the encoding as a Class Selector code point.


The problem addressed by DiffServ ietc not exist in a system that has enough capacity to 24744 all traffic. The first three bits are the IP precedence bits. Although precedence field was part of IP version 4, it was never used. Each traffic class can be managed differently, ensuring preferential treatment for higher-priority traffic on the network. DiffServ is a coarse-grainedclass-based mechanism for traffic management. Within each class, packets are given a drop precedence high, medium or low, where higher precedence means more dropping.

The four available ToS bits now becomes:. The type of service ToS field is the second byte of the IPv4 header. These characteristics are suitable for voice, video and other realtime services.

Pages using RFC magic links. To prevent issues associated with tail dropmore sophisticated drop selection algorithms such as random early detection RED are often used. Some measure of priority and proportional fairness is defined between traffic in different classes. It defined a mechanism for assigning a precedence to each IP packet, as well as a mechanism to request specific 2744 such as high throughput, high reliability or low latency, etc.

Should congestion occur between classes, the traffic in the higher class is given priority. DiffServ simply provides a ieyf to allow classification and differentiated treatment.

Retrieved from ” https: If a router is congested and needs to discard some packets, it will discard packets having lowest priority first. The per-hop behavior is determined by the DS field in the IP header.

DiffServ can, for example, be used to provide low-latency to critical network traffic such as voice or streaming media while providing simple best-effort service to non-critical services such as web traffic or file transfers.


Traffic classifiers may honor any DiffServ markings in received packets or may elect to ignore or override those markings.

Traffic that exceeds the subscription rate faces a higher probability of being dropped if congestion occurs. The entire ToS field would then beassuming that the unused 5 bits are zero.

Retrieved 10 October Typically, DF has best-effort forwarding characteristics. Internet architecture Internet Standards Quality of service. For the design pattern for business applications, see Differentiated service design pattern. Each router on the network is then configured to differentiate traffic based on its class.

Differentiated services

Rather than using strict priority 4274, more balanced queue servicing algorithms such as fair queuing or weighted fair queuing WFQ are likely to be used. In theory, a network could have up to 64 different traffic classes using the 64 available DSCP values. By using this site, you agree to the Terms of Use and Privacy Policy.

Rather than differentiating network traffic based on the requirements of an individual flow, DiffServ operates on the principle of traffic classificationplacing each data packet into one of a limited number of traffic classes.

DiffServ relies on a mechanism to classify and mark packets as belonging to a specific class.