Initial address message (IAM)

INVITE

Address complete message (ACM)

180 RINGING / 183 PROGRESS

Answer message (ANM)

 200 OK

Connect message (CON)

 200 OK

Call progress message(CPG)

183 CALL PROGRESS

Release message (REL)

BYE/CANCEL

Release complete message (RLC)

NA

Reset circuit (RSC)

BYE/CANCEL (only for a call) *

Circuit group reset message(GRS)

BYE/CANCEL (only for a call) *

Circuit group blocking message(CGB)

BYE/CANCEL (only for a call) *

Suspend message (SUS)

Re-Invite or INFO **

Resume message (RES)

Re-Invite or INFO **