FRAME RELAY

 Frame relay is a protocol standard for LAN internetworking which provides a fast and efficient method of transmitting information  from a user device LAN ti a bridge and routers. Data is sent in HLDC packets which refers to "frames". It also uses a packet-switching technology similar to X.25 which can make your networking quicker,simpler and less costly. Like X.25, Frame Relay is a packet-switched protocol. But the Frame-Relay process is streamlined. There are significant differences that make Frame Relay a faster, more efficient form of networking. A Frame-Relay network doesn't perform error detection, which results in a considerably smaller amount of overhead and faster processing than X.25. Frame Relay is also protocol independent-it accepts data from many different protocols. This data is encapsulated by the Frame-Relay equipment, not the network.

  X.25 circuits can be initiated and ended from the users terminals. Frame relay circuits are set up at the time of installation and are maintained 24 hours per day, 7 days per week. Frame relay circuits are not created and ended by user at their terminals or PC's. However, the user may have an application running over a frame relay circuit where computer to terminal sessions are initiated and ended by the user. These sessions are related to the application, not to the underlying frame relay network.

  Frame relay relies on the customer equipment to perform end to end error correction. Each switch inside a frame relay network just relays the data (frame) to the next switch. X.25, in contrast, performs error correction from switch to switch.

 Frame Relay offers an attractive alternative to both dedicated lines and X.25 networks for connecting LANs to bridges and routers. The success of the Frame Relay protocol is based on the following two underlying factors Because virtual circuits consume bandwidth only when they transport data, many virtual circuits can exist simultaneously across a given transmission line. In addition, each device can use more of the bandwidth as necessary, and thus operate at higher speeds.The improved reliability of communication lines and increased error-handling sophistication at end stations allows the Frame Relay protocol to discard erroneous frames and thus eliminate time-consuming error-handling processing. 

 These two factors make Frame Relay a desirable choice for data transmission; however, they also necessitate testing to determine that the system works properly and that data is not lost.

 Frame routers translate existing data communications protocols for transmission over a Frame-Relay network, then route the data across the network to another frame router or other Frame-Relay compatible device. Frame routers can handle many types of protocols, including LAN protocols. They're used in environments that require T1 or slower network access speeds. Each router supports one of many physical data interfaces and can provide several user ports. While Frame Relay offers many benefits, a host of problems have to be overcome before it can be used effectively as a carrier for voice, fax, or video traffic. Until recently, the advancements were vendor-specific solutions that offered no interoperability. Recently ratified industry standards have addressed such issues as compression, packetization, and prioritization. This move towards standardization has been led by the Frame-Relay Forum (FRF) and the International Telegraphic Union (ITU). 

 Most frame relay WANs are hosted by commercial network operators that charge flat rates based on the speed of service or volume of data required. Supported by relatively inexpensive networking hardware, frame relay is based on establishing a logical or virtual circuit across a network with another computer. In frame relay, the packets, or frames, of data may vary in size, and no attempt is made to correct errors. This latter feature is based on the assumption that frame relay is run over relatively high quality, digital networks and the data is less susceptible to errors. This also improves speed since the network protocol isn't trying to correct the data. The stability of this connection allows frame relay service providers to guarantee a certain minimum level of service. The comparative low cost and high quality of service made frame relay one of the most popular WAN technologies in the 1990s. 

sources:

http://www.referenceforbusiness.com/encyclopedia/Val-Z/Wide-Area-Networks-WANs.html

http://www.protocols.com/pbook/frame.htm

http://www.dcbnet.com/notes/framerly.html

http://www.arcelect.com/frame_relay-56kbps_ft1-t1.htm