SIP header "From" field

[yixiu0317]

Does the "From" field have to contain both user and host part in order to make a successful call?

For a particular intercom, when it call mobile the from field looks like this

sip:sip@domain.

Telco said since there is no number in user part, they do not know where to send traffic back, which may be the root cause for failing calls.

Thank you in advance.

[R0g22]

Your ITSP is partially correct. They would need to send the traffic back using the Via header for the most part but yes, FROM header should tell who the UA is or who the initiator is and not just a random "sip@domain".

https://www.ietf.org/rfc/rfc3261.txt
From RFC 3261 -

Usually, the value that populates the From header field in requests generated by a particular UA is pre-provisioned by the user or by the administrators of the user's local domain. Examples for FROM header from the RFC -

Examples:

From: "A. G. Bell" <sip:agb@bell-telephone.com> ;tag=a48s
From: sip:+12125551212@server.phone2net.com;tag=887s
f: Anonymous <sip:c8oqz84zk7z@privacy.org>;tag=hyh8

f is for compact SIP. Valid.

[yixiu0317]

Hi Nipun,

Thank you for the information.

Can you help to clarify one more question?

Attched is the flow sequence collected by Telco, I removed some of the digits of our CUBE external ip.

As you can see Telco sent OK message for the invitation and both parties exchanged SDP, does it mean Telco accept the call?

From the last OK message until the 487 message, there are 23 seconds without any information exchange, normally we should see ringing message sent from Telco, any idea why it did not happen.

Thank you in advance.

[R0g22]

Thats fine. Your ITSP sent a 183 w/SDP which we provisionally acked. This was to allow backward cut through for early media. This could have been for ringing. Your ITSP sent a 200 OK for PRACK and then a 487 which should have been a 200 OK for the INVITE to setup the dialog.