[SR-Users] A real mystery - 1.5.x vintage edition!

[Federico Cabiddu]

Hi Alex,

RFC 3261, section "6. Choosing the best response" states:


"A proxy which receives a 503 (Service Unavailable) response
SHOULD NOT forward it upstream unless it can determine that any
subsequent requests it might proxy will also generate a 503.
In other words, forwarding a 503 means that the proxy knows it
cannot service any requests, not just the one for the Request-
URI in the request which generated the 503.  If the only
response that was received is a 503, the proxy SHOULD generate
a 500 response and forward that upstream."

So Kamailio (the TM module) is doing right there. In recent versions of
kamailio the TM module has a remap_503_500 parameter to control this
behavior (
http://www.kamailio.org/docs/modules/devel/modules/tm.html#remap_503_500),
but not in the 1.5.x branch (http://kamailio.org/docs/modules/1.5.x/tm.html
).

Hope this helps...to convince your customer to upgrade ;-)

Cheers,

Federico

On Thu, Apr 14, 2016 at 4:14 AM, Alex Balashov <abalashov at evaristesys.com>
wrote:

> Hi,
>
> I've got an installation that is still running Kamailio 1.5.x. Yes, I
> know: "They're running WHAT?" As far as I'm concerned, it was EOL'd in
> early 2010. Nevertheless, that doesn't stop the customer from running it.
> They're probably the most change-resistant customer in the history of IP
> telecom, and, knowing this industry, that's a high bar. There's not much I
> can do about it.
>
> Anyway, I have a bit of a mystery:
>
> GW                   Proxy                     PBX
> ==================================================
>
> ------- INVITE ------>
>
> <---- 100 Trying ----
>
>                       -------- INVITE -------->
>
>                       <------ 100 Trying ------
>
>                       <- 503 Service Unavailable
>
>                       ---------- ACK --------->
>
> <- 500 Service Una...
>
> -------- ACK -------->
>
>
> There is no basis in the configuration for the translation of the "503
> Service Unavailable" reply to "500 Service Unavailable", so I'm thinking it
> has to be rooted in some default module behaviour.
>
> Any insight would be appreciated!
>
> -- Alex
>
> --
> Alex Balashov | Principal | Evariste Systems LLC
> 1447 Peachtree Street NE, Suite 700
> Atlanta, GA 30309
> United States
>
> Tel: +1-800-250-5920 (toll-free) / +1-678-954-0671 (direct)
> Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
>
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