July 2002
Intermediate to advanced
528 pages
15h 13m
English
Content preview from Practical VoIP Using VOCALBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Sample Message Flows
As mentioned earlier, SIP phones can be connected together in pairs with an Ethernet cable, or they can be nodes on a LAN or a WAN that supports SIP. The SIP-based network can also work with translators to talk to VoIP phones and networks that work with other protocols such as the Media Gateway Control Protocol (MGCP) and H.323 (the International Telecommunications Union (ITU) VoIP standard). Finally, since most people and organizations are connected to the PSTN, VoIP networks normally contain gateways to translate the protocol messages into Integrated Services Digital Network (ISDN) or Signaling System 7 (SS7) signals for transmission to the phone company’s central office.
Many request and response messages are identified in the RFC. This section introduces you to some of the more common messages and shows how they are used by the network components.
SIP Request Messages
The following are the most common request messages described in the standard and the only ones that are used in our example call flows:
- INVITE
Indicates that the user or service is being invited to participate in a session.
- ACK
Confirms that the client has received a final response to an INVITE request.
- BYE
Indicates that the user wishes to terminate the session.
- CANCEL
Cancels a previous request. This can be confused with BYE; see "BYE and CANCEL: Similar but Not Interchangeable" later in this chapter.
- REGISTER
Registers the address listed in the To header field with a SIP server. ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.