Frame Relay is a CCITT and ANSI standard, which describes a process for data transmission over a public data network. Data is divided into packets in order to transmit information over a Wide Area Network. Frame Relay operates at the physical and data link layers of the OSI reference model but depends on the upper layer protocols for error correction. In addition, Frame Relays use virtual circuits to make connections by means of a connection-oriented service. Finally, Frame Relay nowadays is considered as an industry-standard switched data link layer protocol, which can handle multiple virtual circuits using High-Level Data Link Control (HDLC) encapsulation between connected devices.
Based on the logical topology and the requirements of the Wide Area Network (WAN) of the Washington School District, Frame Relay is only used or provided at the District Office/Data Center for Internet access and other outside network connections. It would be better if Cisco routers will be used to connect to the Frame Relay network because this type of routers provides Local Management Interface (LMI), which are extensions to the basic Frame Relay protocol that offer additional capabilities for complex internetworking environments.
As stated in the requirements, T1 will be used as a physical interface from the District Office/Data Center to the Frame Relay Network thus the connection to the Internet will have a maximum bandwidth of 1.544 Mbps.
To connect to the Internet using Frame Relay, the Committed Information Rate (CIR) is required. Usually, CIRs are provided by the service provider. Also, Data-Link Connection Identifier (DLCI) for the router is also needed since Frame Relay is used as a connection. DLCIs are also provided by the service provider. Lastly, the IP address and the subnet mask for the router’s interface that is connected to the Frame Relay network will also be provided by the service provider.
In order for the Data Center to be connected to the Internet, the router that connects to the Frame Relay network must first be configured in such a way that it will be compatible with the Frame Relay network. The router configuration will be:
1. Select the interface of router that is connected to the Frame Relay network:
Where n is the interface number.
2. Configure the network layer address, which in this case an IP address since the Internet uses TCP/IP:
The values for the Xs and the Ys will be provided by the Internet Service Provider where the Xs field is the IP address and the Ys field is the subnet mask.
3. The Frame Relay encapsulation type must be selected in order to send data traffic over the frame relay network for internet connectivity:
4. Since a Cisco router is used to connect to the Frame Relay Network, the LMI type must be specified:
5. The bandwidth will also be configured:
Router (config-if) # bandwidth 1544
The physical connection uses T1, which is 1.544 Mbps. The value after the bandwidth must be in kilobits. So the maximum bandwidth for T1 is 1544 Kilobits per second.
6. Enable the configuration changes on this interface:
Router (config-if) # no shutdown
