Value of the T303 timer for the Q931 protocol 12.5.5.17.1 T303 T303 is the length of time that the IDT and RDT will wait for a reply to a SETUP message. R12-446 [1315] At the IDT, the value of T303 is not user settable, its value depends on specific vendor implementations, but shall be within the range of 700 ms to 4 seconds. R12-447 [1316] The above range is not intended to define acceptable response-time performance at the RDT, where the low-load (i.e., no other external stimuli requiring call processing activity) mean response time to a SETUP message shall be no greater than 200 ms. R12-448 [1317] At the RDT, the value of T303 shall be provisionable from 700 ms through 4.7 seconds in steps of 500 ms; the default shall be 700 ms. R12-449 [1318] The above range is not intended to define acceptable response-time performance at the IDT, where the low-load (i.e., no other external stimuli requiring call processing activity) mean response time to a SETUP message shall be no greater than 500 ms. Units in milliseconds.