When my system is doing an invite, in the request line I have "sip:nnnnn@domain;user=phone" but when it does a re-invite it drops the user=phone and looks like "sip:nnnnn@domain".
My question is this normal behaviour? I have a supplier complaining but from what I gather from RFC 3261 as its in the same dialog this is fine. Is this correct?
Thanks
The meaning of 'user=phone' is to specify that the user-part of the URI should be interpreted as a telephone number (tel-URI). This information can be useful when establishing a connection. For re-invites it has no added value since the connection between the endpoints is already in place.
Furthermore is it normal that the Request-URI for an invite differs from the Request-URI for a re-invite. The Request-URI used for an invite usually is an address-of-record, e.g. from a phone book. The invite will establish a connection with a specific SIP instance (endpoint). This SIP endpoint returns its contact address in the (final) response, and sometimes a route-set. The contact address is the remote target for the dialog. The remote target and route-set must be used to build the Request-URI for subsequent re-invites (see RFC3261).
I think (without message examples) your system is handling this the right way. If your supplier insists on re-invites having a Request-URI containing 'user=phone' it should include this parameter in the contact addresses for its phones.