This section discusses the terminology used for the various features within a Frame Relay network. You will learn how two internetwork devices communicate end-to-end through a Frame Relay cloud by using a DLCI number, DTE, DCE, demarcation (demarc), local loop, and PSE.

It is important to understand the difference between these devices and to know the terms used for them, both when you are working in a production environment and when you are studying for your CCNA exam. In a real network, it is helpful if you can visualize how the frame traverses the internetwork, as well; you’ll have a better chance of troubleshooting problems.

Critical Information

To understand the terminology used in Frame Relay networks, first you need to know how the technology works. Figure below is labeled with the various terms used to describe different parts of a Frame Relay network.

key Frame Relay Terms

Figure : Frame relay technology and terms The basic idea behind Frame Relay is to allow users to communicate between two data terminal equipment (DTE) devices through data communication equipment (DCE). The users should not see a difference between connecting to and gathering resources from a local server and a server at a remote site connected with Frame Relay. Chances are that this connection will be slower than a 100Mbps Ethernet LAN, but the difference in the connection should be transparent to the user.

Figure illustrates everything that must happen in order for two DTE devices to communicate. Here is how the process works:

The user’s network device sends out a frame on the local network. The hardware address of the router (default gateway) will be in the frame header.

Router Discards the frame after extracting the packets from frame.

The router then forwards the data to the interface that it thinks can find the remote network. (If the router can’t find the network in its routing table, it discards the packet.) . It will add the Data Link Connection Identifier (DLCI; discussed later in this chapter) number associated with the serial interface. DLCIs identify the type of virtual circuit permanent virtual circuit (PVC) or switched virtual circuit (SVC) to the routers and switches participating in the Frame Relay network.

The local loop can connect using various physical media, but twisted-pair or fiber is very common

The CO get the frame and than transfer it through the Frame Relay cloud to its destination. This cloud can be dozens of switching offices or more! The CO looks for the DLCI number, which is mapped locally to an IP address in IP networks. Typically it can find the DLCI number of the remote device or router by looking up an IP-to-DLCI mapping.

Related posts:

1. key Frame Relay Terms and Features Exam Points
2. Frame Relay LMIs, Maps, and Subinterfaces
3. Commands to Configure Frame Relay LMIs, Maps, and Subinterfaces
4. Monitor Frame Relay Operation in the Router
5. Commands to Monitor Frame Relay Operation in the Router
6. Control Router Passwords
7. LAN segmentation using bridges and switches
8. Virtual LANs Exams Points
9. Virtual LANs
10. Command History and Editing Features