Frame relay

Frame relay is a packet switched Telecommunications network, commonly used at the data link layer (layer 2) of the OSI model. Generally the concept of permanent virtual circuits (PVCs) is used to form logical end-to-end links mapped over a physical network. Switched virtual circuits (SVCs), analogous to circuit switching in the public switched telephone network, are also part of the Frame relay specification but are rarely applied in the real world. Frame relay was originally developed as a stripped-down version of the X.25 protocol.

Datalink Connection Identifiers or DLCIs are a locally significant numeric value to represent each end point. Multiple PVCs can be mapped to the same physical end point. It is often provisioned with a Committed Information Rate (CIR) and a burstable component sometimes known as Extended Information Rate (EIR).

Frame relay was designed to make more efficient use of existing physical resources, thereby allowing the overprovisioning of data services to telco customers, as most clients are unlikely to be utilising a data service 100 percent of the time. Frame relay has acquired a bad reputation in some markets because of excessive bandwidth overbooking by telcos.

Frame relay is/was often sold by Telecommunications companies to businesses looking for a cheaper alternative than dedicated lines, its use in different areas depending on governmental and telecommunication's companies polices.

Frame relay is being displaced by ATM and native IP based products, including IP virtual private networks.

External links

• http://www.frforum.com/basicguide/toc.html