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Global Call IP Technology Guide — November 2007
Dialogic Corporation
Supplementary Reference Information
12.2 SIP Transaction Timer Values
This section provides information on the various timers that affect Global Call’s behavior when
handling SIP transactions. The duration values for these timers are preconfigured and are not
configurable by applications.
retransmissionT1
T1 determines several timers as defined in RFC3261. For example, when an unreliable
transport protocol is used, a Client Invite transaction retransmits requests at an interval that
starts at T1 seconds and doubles after every retransmission. A Client General transaction
retransmits requests at an interval that starts at T1 and doubles until it reaches T2.
• Standard duration: 1000 ms
retransmissionT2
T2 determines the maximum retransmission interval as defined in RFC 3261. For example,
when an unreliable transport protocol is used, general requests are retransmitted at an interval
which starts at T1 and doubles until it reaches T2. If a provisional response is received,
retransmissions continue, but at an interval of T2.
• Standard duration: 8000 ms
retransmissionT4
T4 represents the amount of time the network takes to clear messages between client and
server transactions as defined in RFC 3261. For example, when working with an unreliable
transport protocol, T4 determines the time that a UAS waits after receiving an ACK message
and before terminating the transaction.
• Standard duration: 10000 ms
generalLingerTimer
After a server sends a final response, the server cannot be sure that the client has received the
response message. The server should be able to retransmit the response upon receiving
retransmissions of the request for generalLingerTimer milliseconds.
• Standard duration: 32000 ms
inviteLingerTimer
After sending an ACK for an INVITE final response, a client cannot be sure that the server has
received the ACK message. The client should be able to retransmit the ACK upon receiving
retransmissions of the final response for inviteLingerTimer milliseconds.
• Standard duration: 32000 ms
provisionalTimer
The provisionalTimer is set when receiving a provisional response on an Invite transaction.
The transaction will stop retransmissions of the Invite request and will wait for a final response
until the provisionalTimer expires. If you set the provisionalTimer to zero (0), no timer is set.
The Invite transaction will wait indefinitely for the final response.
• Standard duration: 32000 ms
cancelGeneralNoResponseTimer
When sending a CANCEL request on a General transaction, the User Agent waits
cancelGeneralNoResponseTimer milliseconds before timeout termination if there is no
response for the cancelled transaction.
• Standard duration: 32000 ms