Methods,Reference
ACK,[RFC3261]
BYE,[RFC3261]
CANCEL,[RFC3261]
INFO,[RFC6086]
INVITE,[RFC3261][RFC6026]
MESSAGE,[RFC3428]
NOTIFY,[RFC6665]
OPTIONS,[RFC3261]
PRACK,[RFC3262]
PUBLISH,[RFC3903]
REFER,[RFC3515]
REGISTER,[RFC3261]
SUBSCRIBE,[RFC6665]
UPDATE,[RFC3311]