[OpenSIPS-Devel] [OpenSIPS-Users] Why the best response is 408 instead of 486 when parallel forking?

[Dan Pascu]

On Monday 27 October 2008, Iñaki Baz Castillo wrote:
> 2008/10/27 Dan Pascu <dan at ag-projects.com>:
> > I don't know about all internally generated replies, but I know that
> > if a reply came from an end user device, it doesn't make much sense
> > to pick an internally generated 408 Timeout on a dead branch.
> >
> > Maybe doing a custom selection, instead of the "lower reply code
> > wins", would avoid the need to consider internal and external replies
> > in a different way.
>
> That is why I suggested:
>
> - 2XX (inmediate)
> - 6XX (except if disable_6xx_block == 1)

I do not think that 6xx should be considered before 4xx or 3xx. 6xx means 
global response and if you get a 4xx and a 6xx at the same time, it is 
obvious that a device took a global decision that another device doesn't 
agree upon. 6xx should only be sent when a device knows _for sure_ that 
no other device can answer a call and it can give a final answer in the 
name of all devices (which is practically almost never when you have 
parallel forking).

IMO the current selection seems fine, since we haven't hit any other 
problems than this 408 timeout issue, so making the minimal change 
(consider 408 after all other 4xx replies) should provide a solution with 
the minimal impact (as opposed to a solution that would scramble the 
order for almost all reply codes with unknown side effects).

> - 3XX
> - 486
> - 480
> - 4XX
> - 408
> - 5XX
>
>
> --
> Iñaki Baz Castillo
> <ibc at aliax.net>
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-- 
Dan