Whitehelm - Bandwidth Management

Network Traffic Control

Overview

Traffic management, in general, is a simple concept. The idea is to be able to differentiate or classify user traffic according to a wide array of criteria and then assign various priorities to each classified packet or session. For example, bandwidth management allows an administrator to give HTTP traffic a higher priority over SMTP traffic, which in turn may have a higher priority over FTP traffic. At the same time, a bandwidth management solution can track the actual bandwidth used by each application and set limits as to how much each classified traffic pattern can utilise.

There are a variety of methods used in order to enforce the bandwidth management policies configured by an administrator. The simplest method would be to discard packets when certain thresholds are reached or when certain pre-allocated session buffers are overflowing. More complex mechanisms include TCP rate shaping and priority based queuing.

TCP rate shaping uses the inherent flow control mechanisms of the TCP protocol. By adjusting parameters in the packets` TCP headers, a bandwidth management solution can signal the end nodes to throttle the rate at which to transmit packets. Needless to say, the mechanism only works with TCP sessions. TCP rate shaping also has some uncertainties associated with it, as the amount of bandwidth associated with sessions can rarely be exactly enforced. Rate shaping also does not work well with protocols that use short lived sessions (such as HTTP), since such sessions usually end before the bendwidth manager has decided how to shape the rate of the session.

Priority based queuing is a means by which all classified packets are placed in packet queues, each with its own preset priority. A number of queues are available and when it comes to traffic forwarding, packets are forwarded from the higher priority queues first. This is an oversimplified version of what really happens, but it presents the general concept. Various algorithms and safety measures should be deployed to ensure methodical packet forwarding as well as protection against "starvation", where lower priority packets wait in queues for intolerably long amounts of time.

This type of solution can be useful when trying to managed and monitor traffic across internal or external WAN links. It can also be useful when trying to prioritise ERP Traffic over email traffic. E.g SAP ERP packets over Lotus Notes email traffic. These types of product can also be useful if you want to know what your utilisation is on certain WAN links, i.e they will show you when your links are under heavy load and by what type of traffic in detailed reports. This type of information can be useful for planning the amount of bandwidth you will need in the future in relation to how many users that you have. There are many instances where bandwidth management products can be implemented.

Please call 0870 421 4023 to find out how your company can benefit from developing a traffic management solution, or e-mail sales@whitehelm.com requesting more information.