Re: [Sip] Question on loop detection

[Theo Zourzouvillys <theo at voip.co.uk>]

On Wed, Feb 4, 2009 at 4:31 PM, Elwell, John <john.elwell at siemens.com> wrote:

> Questions: Has this problem has been seen in practice? If so, what steps
> have been taken to overcome it? If not, have I misinterpreted RFC 3261?

The behaviour as you described it is correct when the SBC device is a
B2BUA with a single UA core for all sessions flowing through it, which
it isn't - or at least probably isn't what you want.

if instead you considered an SBC to have multiple logical UA cores,
one for each target that it's currently being an SBC for, then that
behaviour would be incorrect (as matching would be done by comparing
all other ongoing transactions within the same UAS core), and both
calls would flow through correctly.

this is how we have had our SBC behaving for the last 3 years without
problem [1].

 ~ Theo

1 - standard SBCs don't exist and it's all in our heads disclaimer applies :)

-- 
Theo Zourzouvillys
Chief Technical Officer
VoIP.co.uk - Commerce House, Telford Road, Bicester, OX26 4LD
Tel: +44 1908 764 196