Chapter 11 : Frame Relay


Frame Relay

     It is a standard wide area network technology that specifies the physical and logical link layers of Integrated Services Digital Network (ISDN) infrastructure, it may be used today in context of many other network interfaces.

     

     Frame Relay is a protocol standard for LAN internetworking which provides a fast and efficient method of transmitting information from a user device to LAN bridges and routers.The Frame Relay protocol uses a frame structured similar to that of LAPD, except that the frame header is replaced by a 2-byte Frame Relay header field. The Frame Relay header contains the user-specified DLCI field, which is the destination address of the frame. It also contains congestion and status signals which the network sends to the user.

Packet Switching

      Is a digital networking communications method that groups all transmitted data regardless of content, type, or structure into suitably sized blocks called packets. Packet Switching features delivery of variable-bit-rate data streams over a shared network. When traversing network adapters, switches, routers and other network nodes, packets are buffered and queued, resulting in variable delay and throughput depending on the traffic load in the network.

What is Frame Relay useful for?

     Frame Relay can be used for various types of connections. It should be seen as a flexible protocol that lies on the Data Level of the Connections between routers. It can currently be used effectively for carrying all sorts of data, up to speeds of about 4 megabits per second.

   Due to the implementation and cost of frame relay, it is most suitable for permanent or semi-permanent connections. It is not desirable as of yet to access frame relay on a dial up basis for economical purposes. it is possible to connect the clients router to frame relay and access internet services over this circuit. at the same time, if the costumer has no other frame relay ports available in different locations, the same port may be used to connect to Wide Area offices the client has. This integrated approach can be attractive for both parties, from one Frame port, can connect multiple costumers. At the same time, the client can connect to multiple remote locations using the one port.

Frame Relay Advantages

   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 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.

Speeds of Frame Relay

     

    

      Some people believe that Frame Relay is being replaced by the modern technologies rather rapidly and it is completely disappearing however it is still the most widely used WAN protocol.