+1 on this response. We watch our metrics closely so we can measure when something begins to move in the wrong direction. We ultimately had to stop paying attention to 503's because of their casual interpretation of the RFC's intention of 5xx responses. It seems like we need a new "Not Now I Have a Headache" response code. In the meantime, we route advance. On Dec 14, 2016, at 00:17, Alex Balashov <abalashov at evaristesys.com> wrote: On Tue, Dec 13, 2016 at 06:04:43PM -0800, Glenn Geller (VDOPh) wrote:
We frequently encounter carriers that use the 503 for anything they cannot classify otherwise.
So, generally, unless it is OUR system, we treat 503 as a "Progress to another route".
My $.02 is that there is no industry "best practice", as widespread use of 503 is a "worst" (or "pessimal") practice. As far as I can tell, 503 (and to a lesser extent, alarmingly, 603) has got to be a catch-all epithet for any sort of call completion failure. The short duration-orientated service providers are the worst offenders, mostly because--as someone pointed out--they aim to obscure any and all possible upstream vendors' failure cause codes with a blanket 503 in the interest of secrecy. However, even relatively respectable members of the food chain will send 503 rather generically in a variety of cases. I would definitely treat it as a "advance to next route" cause. It is very seldom that a 503 is caused by anything from which it can reasonably follow that the destination cannot be reached through any other carrier, and in any case, that's not what 503 is for. As a Class 4/LCR software platform vendor, we've tried to behave correctly and send nuanced SIP cause codes that speak as closely as possible to the genuine nature of the failure, sticking to ISUP mappings where possible and returning 503 only in cases where the call is not processed for business reasons (e.g. unprofitable routes) or some other miscellaneous reason. What we have found is that many customers balk at this, though the short duration & call centre traffic constituencies' protests have been especially howling. Apparently they deal with a lot of customer call centre equipment that expects a 503 in almost all cases and can't properly route-advance on most other codes. So, at least to some extent, as this bad behaviour has crystallised into established practice, the expectation on the endpoint side has also evolved to expect opaque 503s in case of almost all kinds of failure. Dumb, dumb, dumb. Alas, regressions to the stupidest possible common denominator are common in the technology world. -- Alex -- Alex Balashov | Principal | Evariste Systems LLC Tel: +1-706-510-6800 (direct) / +1-800-250-5920 (toll-free) Web: http://www.evaristesys.com/, http://www.csrpswitch.com/ _______________________________________________ VoiceOps mailing list VoiceOps at voiceops.org https://puck.nether.net/mailman/listinfo/voiceops