Polycom SIP 3.1 manual Hold Implementation, Reliability of Provisional Responses, Transfer

Session Initiation Protocol (SIP)

Hold Implementation

	The phone supports both currently accepted means of signaling hold.
	The first method, no longer recommended due in part to the RTCP problems
	associated with it, is to set the “c” destination addresses for the media streams
	in the SDP to zero, for example, c=0.0.0.0.
	The second, and preferred, method is to signal the media directions with the
	“a” SDP media attributes sendonly, recvonly, inactive, or sendrecv. The hold
	signaling method used by the phone is configurable (refer to SIP <SIP/>on
	page A-10), but both methods are supported when signaled by the remote end
	point.
Note
	Even if the phone is set to use c=0.0.0.0, it will not do so if it gets any sendrecv,
	sendonly, or inactive from the server. These flags will cause it to revert to the other
	hold method.

Reliability of Provisional Responses

The phone fully supports RFC 3262 - Reliability of Provisional Responses.

Transfer

The phone supports transfer using the REFER method specified in draft-ietf-sip-cc-transfer-05 and RFC 3515.

Third Party Call Control

The phone supports the delayed media negotiations (INVITE without SDP) associated with third party call control applications.

When used with an appropriate server, the User Agent Computer Supported Telecommunications Applications (uaCSTA) feature on the phone may be utilized for remote control of the phone from computer applications such as Microsoft Office Communicator.

The phone is compliant with “Using CSTA for SIP Phone User Agents (uaCSTA), ECMA TR/087” for the Answer Call, Hold Call, and Retrieve Call functions and “Services for Computer Supported Telecommunications Applications Phase III”, ECMA – 269 for the Conference Call function.

This feature is enabled by configuration parameters described in SIP <SIP/> on page A-10and Registration <reg/> on page A-107and needs to be activated by a feature application key.

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