To understand Frame Relay concepts, it's important to familiarize yourself with key terms and components used in Frame Relay networks. Here are explanations of three fundamental Frame Relay concepts:
1. Data Link Connection Identifier (DLCI):
- DLCI is a unique identifier used in Frame Relay networks to distinguish between different virtual circuits (VCs). Each DLCI represents a specific logical connection between two endpoints in the network.
- DLCIs are locally significant to each Frame Relay switch or router. This means that a DLCI value can represent different connections at different points in the network.
- DLCIs are used to route incoming frames to the appropriate destination based on the DLCI value contained in the Frame Relay header.
2. Permanent Virtual Circuit (PVC):
- A Permanent Virtual Circuit (PVC) is a predefined, statically configured virtual connection between two endpoints in a Frame Relay network.
- PVCs are established in advance by configuring the appropriate DLCI values and network parameters on each Frame Relay interface.
- Once configured, PVCs remain active continuously and provide a dedicated communication path between the configured endpoints.
- PVCs are typically used for permanent connections between sites that require constant communication, such as between branch offices and a central data center.
3. Switched Virtual Circuit (SVC):
- A Switched Virtual Circuit (SVC) is a dynamically established virtual connection in a Frame Relay network, created on demand as needed.
- SVCs are initiated by sending a setup request from one endpoint to another, specifying the desired destination and the required parameters for the connection.
- Upon receiving the setup request, the Frame Relay network allocates resources and establishes the virtual circuit between the requested endpoints.
- SVCs are temporary and remain active only for the duration of the communication session. Once the session ends, the SVC is terminated, and the allocated resources are released.
- SVCs are typically used for occasional or temporary connections that do not require constant communication, such as for data transfers or remote access sessions.
In summary, DLCI is a unique identifier used to differentiate between virtual circuits in Frame Relay networks. PVCs are permanent, statically configured connections established in advance, while SVCs are dynamically established connections created on demand. Understanding these concepts is essential for configuring and managing Frame Relay networks effectively, as they define the structure and behavior of virtual connections within the network.