Virtual circuits:signaling protocols used to setup,maintain teardown VC used in ATM,frame-relay,X.25 not used in today's Internet application transport 5.Data flow begins 6.Receive data application network Call connected 3.Accept c transport data link Initiate call network 2.incoming physical data link physical Network Layer 4-15 Network Layer 4-15 Virtual circuits: signaling protocols  used to setup, maintain teardown VC  used in ATM, frame-relay, X.25  not used in today’s Internet application transport network data link physical application transport network data link physical 1. Initiate call 2. incoming call 4. Call connected 3. Accept call 5. Data flow begins 6. Receive data