A Mechanically Proved and an Incremental Development of the Session Initiation Protocol INVITE Transaction

Box 5

VARIABLES

  s_st

  c_st

INVARIANTS

inv1: s_st STATES

inv2: c_st STATES

inv3: c_st = Calling ⇒ INVITE ∈ cl_sent

inv4: s_st = Proceeding ⇒ INVITE sr_got r1xx sr_sent

inv5: c_st = Proceeding ⇒ r1xx cl_got

inv6: s_st = Accepted ⇒ r2xx sr_sent

inv7: c_st = Accepted ⇒ r2xx cl_got

inv8: s_st = Completed ⇒ r3xx_r699 sr_sent

inv9: c_st = Completed ⇒ r3xx_r699 cl_got ACK cl_sent

inv10: s_st = Confirmed ⇒ ACK sr_got