[sr-dev] More about locally generated 408

[Iñaki Baz Castillo]

2010/4/9 Juha Heinanen <jh at tutpro.com>:
> Iñaki Baz Castillo writes:
>
>  > Unfortunatelly such 408 is painful as the examples above show. This is
>  > the reason I propose TM to generate a local 503 if no response at all
>  > is received for a UDP requests (when fr_timer expires).
>
> inaki,
>
> from rfc3261:
>
> 21.4.9  408 Request Timeout
> The server could not produce a response within a suitable amount of
> time, for example, if it could not determine the location of the user in
> time.
>
>  1.5.4   503 Service Unavailable
> The server is temporarily unable to process the request due to a
> temporary overloading or maintenance of the server.
>
> if there is no response from server, there is no way for the proxy to
> know that the server is "temporarily overloaded or under maintenance".
> it seems that 503 needs to come from the server itself.  so in this case
> 408 looks a more appropriate response to me.

I understand your point, but it would make more sense if 408 is just
caused when a transaction fails due to fr_timer (no provisional
response from destination). But this is not the case as TM generates
408 when fr_inv_timer expires (maybe 60-120 seconds after receiving a
provisional response). So the 408 is a confussing response:

- In the first case (fr_timer expires) there has been a real error (alarm).
- In the second case (fr_inv_timer) there has been no problem, just
the call progress took so long that the proxy has decided to cancel
it.

Perhaps in the second case the proxy should generate a 480 and leave
the 408 just for fr_timer expiration?

-- 
Iñaki Baz Castillo
<ibc at aliax.net>