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The mix of standards for sending voice over IP has gotten a bit muddled of late. We sort through the alphabet soup of protocols.
Just as you raise the last spoonful of VoIP (voice over IP) alphabet soup to your mouth, the cafeteria lady appears with a huge pot, a ladle and an evil grin. "Here, dear, you look hungry; have some more," she says, as she slowly refills your bowl.
Now your spoon twirls up enough letters to spell SIP, SIP+, MGCP, H.GCP and Megaco, as well as the H.323 you've been trying to hold down for months.
H.323 was the future for organizations that had been using proprietary technology to set up and route calls until a standard emerged. Created around an existing set of protocols-including H.225.0 for setup, ISDN Q.931 for signaling, H.245 for negotiation and H.450 for additional servicesH.323 provides a framework for products that interoperate over a network. But it has drawbacks.
Because H.323 is based on ISDN standards, it's limited to point-to-point only. This means simple telephony services, such as conferencing, call forwarding and call transfer, are impossible to implement without external help in the form of an MCU (multipoint control unit), which must sit in on the call and manage the sessions. For conference calls, a point-to-point session is created from the call originator to the MCU. The MCU then creates one point-to-point session from itself to each of the endpoints in the conference. The MCU must operate in a stateful mode, keeping up with all call sessions.
The need to maintain the connections makes large conference calls difficult and requires lots of horsepower. Newer H.323 implementations change this by letting cascading MCUs distribute...