ACK_TIMER Handling

[ericthegeek]

There seem to be two different, and largely incompatible, interpretations of ACD_TIMER in the wild.

According to the text of E1.20, after sending an ACK_TIMER, the responder "shall" send the properly formatted response as a queued message after the timeout has elapsed.

But some implementations seem to assume that you can simply resend the same request after the timeout period and expect to get a valid response. Unfortunately, I don't see this behavior called out on the standard anywhere so there's no way to know how a given responder will handle it.

In the second case, what assumptions does the responder make? Is it treated like ACK_OVERFLOW? (With ACK_OVERFLOW you can't send any other PIDs between the first and second requests and if the responder receives any other PID it must reset its parser state).