[Day 10] 13. Frame-Relay

Frame Relay: This is a type of packet-switched technology used for connecting networks. It allows data to be sent in packets (or frames) over a shared network, making it efficient and cost-effective for transferring data.

NBMA (Non-Broadcast Multi-Access): This term refers to a type of network where multiple devices can connect, but they do not send data to all devices simultaneously (like a broadcast). Instead, each device communicates directly with others. Frame Relay networks are typically NBMA because they don’t support broadcasting.

Key Concepts

1. PVC (Permanent Virtual Circuit): This is a dedicated, permanent connection between two endpoints on a Frame Relay network. It is always available, making it suitable for consistent traffic between two locations.

2. SVC (Switched Virtual Circuit): This is a temporary connection that can be established and torn down as needed. While SVCs were used earlier, they are becoming less common with the rise of PVCs, which offer more stability for continuous connections.

3. DLCI (Data Link Connection Identifier): This is a unique number (ranging from 16 to 1007) assigned to each virtual circuit in a Frame Relay network. It helps identify which connection the data is sent over. Each DLCI corresponds to a specific PVC or SVC.

Example Configuration

When configuring a router to use Frame Relay, you might enter the following commands:

1. Access the Serial Interface:

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   A(config)# interface s0

2. Set the Encapsulation to Frame Relay:

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   A(config-if)# encapsulation frame-relay

3. Assign a DLCI to the Interface:

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   A(config-if)# frame-relay interface-dlci 16

   This command assigns the DLCI number 16 to this interface, indicating the specific virtual circuit it will use.

4. Map IP Address to DLCI:

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   A(config-if)# frame-relay map ip 172.16.20.2 17

   This command creates a mapping between the Layer 3 (network layer) IP address (172.16.20.2) and the next hop’s DLCI (17). This tells the router how to route packets from one Layer 3 address to the appropriate Layer 2 DLCI.

Summary

In summary, Frame Relay is a flexible and efficient way to connect networks using packet-switched technology. It uses unique identifiers (DLCIs) to manage connections between devices. Understanding PVCs and SVCs, as well as how to configure Frame Relay on routers, is essential for effective network management.