Technical Summary
This document defines the 608 (Rejected) SIP response code, which informs a
calling party that an intermediary has rejected their call attempt. This
document also extends the Call-Info header field so that the caller may
contact the blocking party if the rejection was in error. The 608 response
code addresses the use case of call rejection by a call analytics engine or
other automated process. This contrasts with the 607 (Unwanted) SIP response
code, which is sent by a SIP user agent when a human indicates that the call
was not wanted [RFC8197].
Working Group Summary
The document is of interest to the STIR (Secure Telephone Identity
Revisited) WG, but discussions were (mostly) kept to the SIPCORE mailing
list since the document covers a SIP extension. Sometimes cross-posting was
not successful and some discussions occurred only on the STIR mailing list.
All feedback that was discussed on the STIR mailing list was incorporated
into the document, however.
Document Quality
One of the authors (Bhavik Nagda) implemented this solution in Kamailio,
which is an open source SIP server. The implementation can be found at
https://github.com/nagdab/608_implementation. There are also governmental
agencies that are interested in the 608 response code feature.
Reviewers and their contributions have been called out in the
Acknowledgements section. Tolga Asveren provided substantial feedback on
interoperability and security considerations.
Personnel
Jean Mahoney is the Document Shepherd.
Adam Roach is the Responsible Area Director.