The term virtual here means that the two dtes are not connected directly but through a network. For example have look on following figure that illustrates a network with simple point to point leased line connection. Packetswitched networks enable end stations to dynamically share the network medium and the. The logical connection through the frame relay network between two dtes is called a virtual circuit vc. Using an example of a large enterprise network helps illustrate the benefits of using a. It also forms an important step in the direction to full multimedia atm networking. In this tutorial ill explain to you why we used framerelay and how it works. Frame relay uses virtual circuits to connect a single router to multiple remote sites. In addition, frame relay standards have been developed to interwork. Basic concepts of frame relay explained in easy language. In this tutorial ill explain to you why we use d frame relay and how it works. Frame format frame relay uses the synchronous hdlc frame format see synchronous and asynchronous communications up to 4kbytes in length. Frame relay is one of the wan protocols you need to understand if you plan to become ccna certified. Although the above picture shows two vcs from the headquarter but do you remember that the headquarter only has only one serial interface.
Today, it is used over a variety of other network interfaces as well. The ohio state university raj jain 21 physical layer options q both ansi and itut define frame relay on isdn q frame relay forums implementation agreements. It allows multiple logical channels to use the same physical. Frame relay providers use a frame relay switch to route the data on each. The frame relay header contains the userspecified dlci field, which is the destination address of the frame. Presently, it is used for networks for atms and credit card verification.
Frame relay is an example of a packetswitched technology. It also contains congestion and status signals which the network sends to the user. A common private frame relay network implementation is to equip a t1 multiplexer with both frame relay and nonframe relay interfaces. The router can communicate with other routers through the frame relay network carrying multiple protocols for example ip, ipx and decnet phase iv. Frame relay networks 1 abstract frame relay networks reduce the. In fact, we need to run a routing protocol like ospf, eigrp or rip to make different networks see each other dynamic. Since we want connectivity between the sites we have an isp. This chapter focuses on frame relay s specifications and applications in the context of wan services. In this part we will continue to discuss about other important frame relay parameters. So how can it know which branch it should send the frame to. Non frame relay traffic is forwarded to the appropriate application or service, such as a private branch exchange pbx for telephone service or to a videoteleconferencing application. As an example of equipment used to construct a frame relay network, the technology deployed by. Frame relay traffic is forwarded out the frame relay interface and onto the data network.
With virtual interface frame relay can effectively handle this network or even bigger. Nonframe relay traffic is forwarded to the appropriate application or service, such as a private branch exchange pbx for telephone service or to a video. Its also one of the most difficult protocols to understand for most ccna students. Configuring frame relay feature history release modification forinformationaboutfeaturesupportinciscoios software,useciscofeaturenavigator. Suppose you are working in a big company and your company has just expanded to two new locations. Frame relay originally was designed for use across integrated services digital network isdn interfaces. Frame relay is no longer a topic in ccnav3 200125 exam. In most cases, permanent virtual circuits are used, i. As a result, the performance of a frame relay network is virtually identical to that of a leased line, but because most of the network is shared, costs are lower. It was originally designed for use in the 1970s and became very popular in 1980s.