ts.SIPTimerBMultiplier

Specifies a multiplier used to calculate the timeout for INVITE attempts. The timeout is calculated by multiplying this value and the ts.SIPT1 value. If a Voice Browser service instance does not respond to an INVITE by the time this timeout expires, the Telephony Session service marks the instance as failed. If all Voice Browser service instances fail, the Telephony Session service returns a 480 Temporarily Unavailable message.

For example, if ts.SIPT1 is 200 (200 milliseconds) and ts.SIPTimerBMultiplier is 30, the Telephony Session service issues up to five unsuccessful INVITE attempts before the timeout. These attempts occur at 0 ms, 200, 600 ms(200 + 400), 1400 ms(200 + 400 + 800), and 3000 ms (0 + 200 + 400 + 800 +1600). The next INVITE would occur at 6200 ms (3000 ms + 3200 ms). However, since the timeout occurs first at 6000 ms (200 ms x 30), this sixth INVITE is not issued.

The default value is 30, which (along with the ts.SIPT1 HA default of 200) allows the Telephony Session service to try both Voice Browser service instances before the remote party times out.

For more information on INVITE intervals and timeouts, see the SIP RFC 3261.