Unable to register phone on Zultys MX250 r8.0.3: SIP 400 Error

[IsaacSchneider]

There are two things that stand out in the registration message. First the Max Forwards parameter on all of the phones I have seen appear just after the Via parameter. Second is the Contact line not giving all of the parameters most other phones are presenting.

I looked up the RFCs and they do not specifically state in which order most of the parameters must appear. However the RFC examples clearly show the Max Forwards parameter always after the Via parameter. This follows the behavior of other vendors sip ua.

As for the Contact line the RFC states it is optional for the extended parameters but is suggested/recommended to provide additional parameters. And again on other phones they all have additional parameters like Registration Timeout and additional unique login session ids, rport,.. etc.

What I did not check but is something the RFC requires is the unique session ids have to be unsigned 32bit numbers.

-Isaac