Difference between dialog and session in SIP?

对话与会话的区别

最新推荐文章于 2025-09-27 10:47:51 发布

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本文探讨了SIP中对话(Dialog)与会话(Session)的概念差异。对话代表了信令层面的呼叫状态，包括序列号、路由集等信息；而会话则侧重于媒体流的建立与管理。此外，还解释了请求如何在对话内外发挥作用。

Patrick Lam wrote:

Dear all:

I am a little confused about the concept of a dialog. What exactly is
the difference between a dialog and a session?

A dialog is a sip relationship. A session is a media relationship.

Does dialog mean a "call
has already been setup" in the signaling sense, while a session mean the
"media has already been setup" in the media sense?

Thats pretty much right.

Also, what does "part of a dialog" mean?  Are "INVITE", "ACK" and the
responses considered "part of a dialog"?

Dialog represents state, which includes sequence numbers, route sets, and URIs. A request sent as part of a dialog means that it includes route headers from the route set of the dialog, and uses the next highest sequence number in the dialog.'

What does "outside the dialog" mean then?  Is a request is outside the
dialog, does it still affect or change anything "inside the dialog"
then?

Outside the dialog means that it is not within the context of a dialog. It doesnt use the callid, cseq, or route sets of any existing dialogs, and when such a reuqest is set, it has no impact on the state of an existing dialog.

-Jonathan R.