When Asterisk was first being written one of the things needed was the ability to do conference bridges. When you think of conference bridges you might think of the one you configure in the dialplan to join, but conference bridges are actually used in other places. An example of this is three way calling for an analog phone. That’s actually a conference bridge. To that end all of the conference bridging in Asterisk was built on the same thing: DAHDI. Leveraging the same functionality used for three way calling allowed conference bridges with non-DAHDI channels to also occur. Unfortunately this meant that the DAHDI kernel module still needed to be loaded even if no hardware was in use, so that conference bridging could occur. This wasn’t ideal in the long term so we needed to come up with a new solution.
The Bridging Framework
As the development of Asterisk progressed we wanted a more defined and pluggable mechanism to connect channels together. This brought the bridging framework into existence. The bridging framework is a pluggable mechanism that allows different technologies to be registered and used to connect channels together in various scenarios and situations. In one case you may have 2 RTP capable channels connected together and they should more efficiently exchange packages. In another you may have 5 different channels connected together that should be in a conference bridge. The bridging framework is what allows this to happen with plenty of hooks to be able to add features on top.
The ConfBridge dialplan application is a consumer of the bridging framework for the purposes of the conference bridges. Underneath it uses the bridging framework to allow media to be mixed, but it also sprinkles on top of it the features you would expect from a conference bridge. The ability to kick people out, administer the conference bridge, have join and leave sounds, recorded names, etc. Those are provided by ConfBridge itself. It provides a rich experience and is extremely configurable.
The Deprecation Of MeetMe
You may be asking yourself why I’ve written a blog post talking about MeetMe and ConfBridge a bit. The reason is that as of Asterisk 19 MeetMe is now a deprecated dialplan application. If you are actively using it you need to move onward over to ConfBridge. As of Asterisk 21 the MeetMe dialplan application will be completely removed.