| This class contains the enumerations that define the underlying state of an
existing transaction. SIP defines four types of
transactions, these are Invite Client transactions, Invite Server transactions,
Non-Invite Client transactions and Non-Invite Server transactions.
There are six explicit states for the various transactions, namely:
- Calling:
- Invite Client transaction: The initial state, "calling", MUST be entered
when the application initiates a new client transaction with an INVITE request.
- Trying:
- Non-Invite Client transaction: The initial state "Trying" is entered
when the application initiates a new client transaction with a request.
- Non-Invite Server transaction: The initial state "Trying" is entered
when the application is passed a request other than INVITE or ACK.
- Proceeding:
- Invite Client transaction: If the client transaction receives a
provisional response while in the "Calling" state, it transitions to the
"Proceeding" state.
- Non-Invite Client transaction: If a provisional response is received
while in the "Trying" state, the client transaction SHOULD move to the
"Proceeding" state.
- Invite Server transaction: When a server transaction is constructed for
a request, it enters the initial state "Proceeding".
- Non-Invite Server transaction: While in the "Trying" state, if the
application passes a provisional response to the server transaction, the
server transaction MUST enter the "Proceeding" state.
- Completed: The "Completed" state exists to buffer any additional
response retransmissions that may be received, which is why the client
transaction remains there only for unreliable transports.
- Invite Client transaction: When in either the "Calling" or "Proceeding"
states, reception of a response with status code from 300-699 MUST cause the
client transaction to transition to "Completed".
- Non-Invite Client transaction: If a final response (status codes
200-699) is received while in the "Trying" or "Proceeding" state, the client
transaction MUST transition to the "Completed" state.
- Invite Server transaction: While in the "Proceeding" state, if the
application passes a response with status code from 300 to 699 to the server
transaction, the state machine MUST enter the "Completed" state.
- Non-Invite Server transaction: If the application passes a final response
(status codes 200-699) to the server while in the "Proceeding" state, the
transaction MUST enter the "Completed" state.
- Confirmed: The purpose of the "Confirmed" state is to absorb any
additional ACK messages that arrive, triggered from retransmissions of the
final response. Once this time expires the server MUST transition to the
"Terminated" state.
- Invite Server transaction: If an ACK is received while the server
transaction is in the "Completed" state, the server transaction MUST
transition to the "Confirmed" state.
- Terminated: The transaction MUST be available for garbage collection
the instant it enters the "Terminated" state.
- Invite Client transaction: When in either the "Calling" or "Proceeding"
states, reception of a 2xx response MUST cause the client transaction to
enter the "Terminated" state. If amount of time that the server transaction
can remain in the "Completed" state when unreliable transports are used
expires while the client transaction is in the "Completed" state, the client
transaction MUST move to the "Terminated" state.
- Non-Invite Client transaction: If the transaction times out while the
client transaction is still in the "Trying" or "Proceeding" state, the client
transaction SHOULD inform the application about the timeout, and then it
SHOULD enter the "Terminated" state. If the response retransmissions buffer
expires while in the "Completed" state, the client transaction MUST transition
to the "Terminated" state.
- Invite Server transaction: If in the "Proceeding" state, and the application
passes a 2xx response to the server transaction, the server transaction MUST
transition to the "Terminated" state. When the server transaction abandons
retransmitting the response while in the "Completed" state, it implies that
the ACK was never received. In this case, the server transaction MUST
transition to the "Terminated" state, and MUST indicate to the TU that a
transaction failure has occurred.
- Non-Invite Server transaction: If the request retransmissions buffer
expires while in the "Completed" state, the server transaction MUST transition
to the "Terminated" state.
For each specific transaction state machine, refer to
RFC3261.
author:
BEA Systems, NIST
version:
1.2 |
