Circuit Switching Switch 非 Input Ports Output Ports Connects(electrons or bits) ports to ports 11
11 Circuit Switching Input Ports Output Ports Switch Connects (electrons or bits) ports to ports
Packet switchedⅴs.VC Pa d avila VCI Payload Dst RI packet A R2 g rardin R1 table R4 Dst R2 B R3 Different paths to RI VC table same destination VCI R2 (useful for traffic engineering! Vc 2 R3 12
12 Packet switched vs. VC A B R2 R1 R3 R4 R1 packet forwarding table: Dst R2 R1 VC table: VC 1 R2 VC 2 R3 Different paths to same destination! (useful for traffic engineering!) Payload VCI Payload Dst Dst 1 2 3 4 3 3 3 1 1 1 2 2 4 4 4 2
Virtual circuit Pa d avila VC Payload A 2R2 R1 R4 B R3 Challenges RI VC table: R2 VC table How to set up path? VC5 R2 How to assign IDs?? VC5R4 13
13 Virtual Circuit A B R2 R1 R3 R4 R1 VC table: VC 5 R2 Payload VCI Payload Dst 1 2 3 4 3 3 3 1 1 1 2 2 4 4 4 2 R2 VC table: VC 5 R4 Challenges: - How to set up path? - How to assign IDs??
Connections and Signaling Permanent Vs switched virtual connections (PVcs, svcs 》 static vs. dy namic. PVCs last“ a long time E. g, connect two bank locations with a Pvc that looks like a circuit SVcs are more like a phone call PVcs administratively configured (butnot manually") 》 SVCs dynamically set up on a“per- call' basis Topology 》 point to point 》 point to multipoint multipointto multipoint Challenges: ) How to configure these things? What vcl to use? Setting up the path 14
14 Connections and Signaling Permanent vs. switched virtual connections (PVCs, SVCs) » static vs. dynamic. PVCs last “a long time” – E.g., connect two bank locations with a PVC that looks like a circuit – SVCs are more like a phone call » PVCs administratively configured (but not “manually”) » SVCs dynamically set up on a “per-call” basis Topology » point to point » point to multipoint » multipoint to multipoint Challenges: » How to configure these things? – What VCI to use? – Setting up the path
Virtual circuit switching Label( tag) Swapping A 2 R2 RI R4 Dst B R3 Global vc id allocation --ICK! Solution: Per-link uniqueness Change VCl each hop Input Port Input vcl Output Port Output VCI R1: 5 3 9 R2:2 R4:1 2 3 15
15 Virtual Circuit Switching: Label (“tag”) Swapping Global VC ID allocation -- ICK! Solution: Per-link uniqueness. Change VCI each hop. Input Port Input VCI Output Port Output VCI R1: 1 5 3 9 R2: 2 9 4 2 R4: 1 2 3 5 A B R2 R1 R3 R4 Dst 1 2 3 4 3 3 3 1 1 1 2 2 4 4 4 2