T1

500 milliseconds

17.1.1.1

RTT Estimate

T2

4 seconds

17.1.2.2

Maximum retransmit interval for non-INVITE requests and INVITE responses

T4

5 seconds

17.1.2.2

Maximum duration that a message remains in the network

Timer A

T1

17.1.1.2

INVITE request retransmit interval, for UDP only

Timber B

64*T1

17.1.1.2

INVITE transaction timeout timer

Timer C

> 3 minutes

16.6 (bullet 11)

Proxy INVITE transaction timeout

Timer D

> 32 seconds for UDP, 0 for TCP/SCTP

17.1.1.2

Wait time for response retransmits

Timer E

T1

17.1.2.2

Non-INVITE request retransmit interval, for UDP only

Timer F

64 * T1

17.1.2.2

Non-INVITE transaction timeout timer

Timer G

T4 for UDP, 0 for TCP/SCTP

17.2.1

INVITE response retransmit interval

Timer H

64 * T1

17.2.1

Wait time for ACK receipt

Timer I

T4 for UDP, 0 for TCP/SCTP

17.2.1

Wait time for ACK retransmits

Timer J

64 * T1 for UDP, 0 for TCP/SCTP

17.2.2

Wait time for non-INVITE request retransmits

Timer K

T4 for UDP, 0 for TCP/SCTP

17.1.2.2

Wait time for response retransmits