SIP Intro --- HOLD event

HOLD event

以下是節錄自RFC3264的一段文字，在說明HOLD的implementation。
稍後會說明...




RFC 2543 [10] specified that placing a user on hold was accomplished by setting the connection address to 0.0.0.0. Its usage for putting a call on hold is no longer recommended, since it doesn’t allow for RTCP to be used with held streams, doesn’t work with IPv6, and breaks with connection oriented media. However, it can be useful in an initial offer when the offerer knows it wants to use a particular set of media streams and formats, but doesn’t know the addresses and ports at the time of the offer. Of course, when used, the port number MUST NOT be zero, which would specify that the stream has been disabled. An agent MUST be capable of receiving SDP with a connection address of 0.0.0.0, in which case it means that neither RTP nor RTCP should be sent to the peer.



目前業界的HOLD的implementation並沒有一定的標準，有些是使用0.0.0.0來作識別。有些另外於sdp中另外夾帶msg，有些還會看port，還有些是servert會處理掉，各家有各家的做法。