[SR-Users] Advice on handling SIP trunk to a Perimeta SBC

[Juha Heinanen]

Björn Bylander writes:

> My problem is this: When the Perimeta SBC sends its first INVITE (I
> can't say anything about any succeeding INVITEs yet) it's added a
> Record-Route header with the "lr" parameter included which, as far as
> I can see makes Kamailio think it should use loose routing which is
> all well I think. But when the SBC sends an ACK for the "200 OK" from
> the Kamailio side it doesn't include any Route headers and I think
> that makes it hard for Kamailio (at least with the standard script
> which is basically what I'm using) to know where to relay the ACK, at
> least it makes the t_check_trans() call in WITHINDLG after
> 'is_method("ACK")' return false which makes the script ignore the
> ACK. 
> 
> Any thoughts or suggestions on how to handle this?

If the SBC does not include Route headers it learned from 200 OK R-R
headers into in-dialog requests (e.g. ACK) it break SIP RFC3261 and you
should ask them to fix their code or get your money back.

-- Juha