Probabilistic Verification of Go-Back-N Tong Wang tw2436 Yihan Zou yz2575 Hang Yin hy2368 Miaoqiong Wang mw2908

Assumptions RTT >> Tx: multiple messages on channel FC and BC are FIFO queues: packets arrive in order Sender/ Receiver can only process one packet at a time Sender always has packet to send Timeout occure Stopping conditions Initial state: ( 0 0 (0,1,2,3) ( ) )

Timeout Backward channel is empty Both forward and backward channel is empty

Stopping points 3 lost packages on the channel ACK0 is successfully received

Global state (Tx, Rx, FC, BC) Four stacks: stack(i) contains states going through i low probability transitions

Initial (0 0 (0,1,2,3) ()) Get M0, Get M1, Get M2, Get M3 0 step 1 Pop (0 0 (0,1,2,3) ()) (0 1 (1,2,3) (0)) Get M0, Get M1, Get M2, Get M3, Acpt M0 0 (0 0 (1,2,3) ()) Get M0, Get M1, Get M2, Get M3 1 step 2 Pop (0 1 (1,2,3) (0)) ,(1 1 (1,2,3,4) ()) is accepted (0 2 (2,3) (0,1)) Get M0, Get M1, Get M2, Get M3, Acpt M0, Acpt M1 0 (0 1 (1,2,3) ()) Get M0, Get M1, Get M2, Get M3, Acpt M0 1 (0 1 (2,3) (0)) Get M0, Get M1, Get M2, Get M3, Acpt M0 1 (0 0 (1,2,3) ()) Get M0, Get M1, Get M2, Get M3 1 step 3 Pop (0 2 (2,3) (0,1)) ,(1 2 (2,3,4) (1)) is accepted (0 3 (3)(0,1,2)) Get M0, Get M1, Get M2, Get M3, Acpt M0, AcptM1, AcptM2 0 (0 2 (2,3) (1)) Get M0, Get M1, Get M2, Get M3, Acpt M0, Acpt M1 1 (0 2 (3) (0,1)) Get M0, Get M1, Get M2, Get M3, Acpt M0, Acpt M1 1

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