SIP UACs have user interface capabilities ranging from pop-up
windows and audio on PC softclients to audio-only on "black"
phones or endpoints connected via gateways. Rather than forcing a
server generating an error to choose between sending an error
status code with a detailed reason phrase and playing an audio
recording, the Error-Info header field allows both to be sent.
The UAC then has the choice of which error indicator to render to
the caller.
是的,如果您查看位于https://www.ietf.org/rfc/rfc3261.txt的 RFC, 它准确地解释了如何执行此操作。
因此,客户端会在 SIP 回复中收到 404,并且会被告知连接到 sip:[email protected] 以获取录制的消息。