The basic initiative behind a SD-WAN solution is to enable connectivity between two DTE (routers, LANs) networks through a DCE (frame Relay switches, ISP) network.
The network’s DCE device (CSU/DSU) provides clocking to the DTE-connected interface.
Frame relay is a Packet switching method used to transport data from one location to another. It’s a type of high performance WAN protocol originally designed for use across Integrated Services Digital Network (ISDN) interfaces.
A Packet-switched network enable end stations to dynamically share the network medium and the available bandwidth.Its is widely used in today’s network because its easily used to construct reliable and low-cost networks.
Unlike Point-to-Point serial link; it can be used to connect one site (network) to many remote sites through a single physical circuit. Frame Relay makes use of virtual circuits to connect any physical circuit in a cloud to any other physical circuit. Virtual circuits can coexist on a single physical interface. In essence, it allows you to configure the routers (DTEs) to function like a set of point-to-point physical connections.
Simply put, If the router (DTE) in network A wants to send a packet to network B, it uses the correct DLCI number for the virtual circuit that was assigned and connects to network B or any other network ( with assigned DLCI number) in the Frame Relay header.
Benefits of Frame relay
1. Cost Effectiveness
i. It reduces network costs by using less equipment, less complexity, and an easier implementation.
. ii. It’ shares bandwidth across a larger base of customers. Typically, a network provider can service 40 or more 56 kb/s customers over one T1 circuit. Using dedicated lines would require more DSU/CSUs (one for each line) and more complicated routing and switching. Network providers save because there is less equipment to purchase and maintain.
2. It provides greater bandwidth, reliability, and resiliency than private or leased lines.
Virtual circuit provides considerable flexibility in network design. In Frame Relay, the end of each connection has a number (value) for identification called a Data Link Connection Identifier (DLCI). Any station can connect with any other simply by stating the address of that station and DLCI number of the line it needs to use.