Polycom 1725-11530-310 manual Header Support, Following SIP request headers are supported

Administrator’s Guide SoundPoint IP / SoundStation IP

Method	Supported	Notes
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

Header Support

The following SIP request headers are supported:

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

B - 4