Forwarding an IP Packet over a Frame Relay PVC

Forwarding an IP Packet over a Frame Relay PVC

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R1 needs to send the packet to R2, physically using its serial0 interface, and logically using the PVC with DLCI 102. First, R1 has to perform Frame Relay encapsulation like the other data link protocols covered in this book by putting the IP packet between a Frame Relay header and trailer. As usual, the trailer has a frame check sequence (FCS) field that allows the receiver of the frameR2 in this caseto know if the frame experienced errors. And, as was mentioned before, the Frame Relay header holds the 10-bit-long DLCI field that identifies the PVC. By putting the right DLCI into the Frame Relay header (102 in this case), the Frame Relay switches inside the telco can forward the frame correctly to R2.