Polycom SIP 3.1 - Manual (Page 286)

Administrator’s Guide SoundPoint IP / SoundStation IP
B - 4
Header Support
The following SIP request headers are supported:
INFO Yes RFC 2976, the phone does not generate INFO
requests, but will issue a final response upon
receipt. No INFO message bodies are parsed.
MESSAGE Yes Final response is sent upon receipt. Message
bodies of type text/plain are sent and received.
UPDATE Yes
Method Supported Notes
Note In the following table, a “Yes” in the Supported column means the header is sent
and properly parsed.
Header Supported Notes
Accept Yes
Accept-Encoding No
Accept-Language Yes
Alert-Info Yes
Allow Yes
Allow-Events Yes
Authentication-Info No
Authorization Yes
Call-ID Yes
Call-Info Yes
Contact Yes
Content-Disposition No
Content-Encoding No
Content-Language No
Content-Length Yes
Content-Type Yes
CSeq Yes
Date No