The data is transferred in frames and they are relayed on the data link layer. The network provides permanent and fast virtual connection PVC. Frame relay provides the service between ISDN and ATM. Over the leased telephone lines, frame relay is used to connect the LAN with the fiber optic backbones and with the WAN. The data is transmitted to the destination by means of permanent of switched virtual circuits. Many virtual circuits can exist across a transmission between because virtual circuits only consume the bandwidth when they transmit the data.
The frame relay circuits are the logical circuits that are created at the time of installation and are not created by the users at their systems. In device that is a part of the frame relay network can operate at a very high speed due to the availability of the more bandwidth. The high performance and the error handing techniques allow frame relay protocol to discard the time consuming error handling techniques. The standards of the Frame relay protocols have been developed by the ANSI and CCITT. The frame relay structure is based on the LAPD protocol.
The header of the frame has the data link connection identifier DLCI and congestion bits. When a network becomes congested i.e. it is not able to transmit any new data it begins to discard the frames and these discarded frames retransmitted so more congestion is produced. To avoid this problem several methods have been developed.
Two bits Forward Explicit Congestion Notification and Backward Explicit Congestion Notification in the header of the frame are used to signal the devices at the user end that congestion has been developed. When congestions occur the FECN is changed to 1 and in this way all the downstream nodes and the attached devices at the user end learn about the congestion in the line. The BECN is changed to 1 in the frame that traveling back to the source of the data transmission. So the source is notified of the congestion in the line and to slow down the transmission until the congestion in the line is minimized.
Frame relay works on the consumer hardware such as router and switches and each switch relays the data to the next switch in frame relay network. Frame relay also work with the meshed network because each endpoint can be connected to the different locations and so on. FR is a cost effective and standardized way of creating a wide area network. Frame relay provides error free high data transmission rate and the speed comes in a number of options such as 56 KB/s, 64 KB/s, 128 KB/s, 256 KB/s, 512 KB/s, 1.5 MB/s, and 2 MB per second.