What’s DiffServ?

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DiffServ is an abbreviation for differentiated services, which is a network management system. Differentiated service allows users to set up a class system and tag network information based on content. Routers using DiffServ protocols then organize those packets based on their tags. Some packets, such as voice transmissions, have a higher priority and will always be transmitted immediately. Other packets are held for later transmission or dropped altogether.

Information sent over a standard network is divided into packets. Each of these packets contains a small portion of the total information. A computer takes information and divides it into packets containing the information, its network address and the address where it is going. This information is sent in rapid pulses across the network or the Internet. When it gets to where it’s going, the receiving computer reassembles the packets into the original data.

A DiffServ system adds an additional marker to packets when they are first created. This marker designates the package based on predefined characteristics. These characteristics are devised by the user and can be anything from the content of the information to its associated addresses. These indicators are used to assure users that certain information will always have priority over others.

Any system that can handle DiffServ packets can make judgments about the importance of packets as they travel the network. When a group of packets enters the differential services router, it examines individual markers and prioritizes them based on user-defined lists. The packets then move in order of priority. If multiple high priority packets enter the system, lower priority packets continue to be rejected.

In general, a DiffServ system ensures correct and timely delivery of one or two types of data, or two markers, and best effort on the rest. This means that one or two types of marked packages will arrive on time and in order without fail, but other packages may not. In networking, best effort means that the system will do its best to move information around, but it won’t guarantee anything. Packets can arrive slowly or never transmit.

This is one of the major disadvantages of DiffServ. When packets are held back, it can cause a lot of problems on both ends of the system. If packets arrive damaged or out of order, the receiving computer will need to request the information again. This request causes the sending computer to resend all the necessary information, effectively doubling the amount of low-priority information sent. This increases the bandwidth used on both ends with no guarantee that the second transmission will work.

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