[sr-dev] [tracker] Task opened: Extending TM timeout/408 handling

[sip-router]

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User who did this - Iñaki Baz Castillo (ibc) 

Attached to Project - sip-router
Summary - Extending TM timeout/408 handling
Task Type - Bug Report
Category - tm
Status - Assigned
Assigned To - Andrei Pelinescu-Onciul
Operating System - All
Severity - Low
Priority - Low
Reported Version - Development
Due in Version - Undecided
Due Date - Undecided
Details - Hi, let's suppose the following case:
SR receives an INVITE and performs serial or parallel forking to gw1 and gw2.

Three cases:


case a)
- gw1 replies 480.
- gw2 replies 408.

case b)
- gw1 replies 480.
- gw2 replies 180 and fr_inv_timer expires so a local 408 is generated.

case c)
- gw1 replies 480.
- gw2 replies nothing and fr_timer expires so a local 408 is generated.


In any case, after the transaction fails I handle the winning response in failure_route in which I get a 408. But there is no way to determine which of the above 3 cases took place.

For cases "a" and "b" the 408 could be a good choice (also the 480) but in case "c" I'd strongly prefer using the 480. But there is no way, in failure_route, to determine if our case is "a", "b" or "c".

A non reliable pseudo-workaround is setting a transaction flag(RINGIN_RECEIVED) so when inspecting the 408 in failure_route we can "determine" if fr_timer expired (case "c") or not (cases "a" or "b"). This is not reliable as the flag could be set by other branch in which 1XX was received.


Possible solutions:

1) When TM chooses the winning response it must give lowest priority to locally generated 408 if such 408 was raised by fr_timer expiration, so for the above cases the winning response would be:
    a) 408
    b) 408
    c) 480

or:

2) When fr_timer expires a new status code is locally generated, i.e. 478 "No response received at all". Such code would have lowest priority.


Opinions?

More information can be found at the following URL:
http://sip-router.org/tracker/index.php?do=details&task_id=55

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