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Home / Learn More / What is the definition of H.323 protocol.

What is the definition of H.323 protocol.


H.323 It’s a pretty complicated protocol.

So we’re going to hit the basics. So without further ado H.R. 3 2 3 H.R. 3 2 3 is not actually a protocol that you’ll see on the network. It’s what we call an umbrella protocol and it is from the International Telecommunication Union telecom sector. So it actually includes a bunch of sub-protocols and that’s actually what we see on the network.

Now H3 2 3 is what we call a signaling protocol. So anytime you’re thinking about signaling protocols along with H.R. 3 2 3 you’ll be talking about SIP and skinny. Those are other major signaling protocols. It predates both of these guys at least as far as the deployment goes. It’s been at least an hour of the seat for a while. But the 2 3 3 2 3 standard was around very early and comes from a very telecom ish background as you might imagine.

And it was the de facto standard for video conferencing. Remember if you think back to the way that things actually got started long before we had voice over IP we had stuff like video conferencing. Now once you drop out of H.R. 3 2 3 call control and setup and things like that you drop into RTP just like some of the other technologies that we’ve talked about in these videos. And then the chapters.

Typologies and operations

So in that sense it’s exactly like many of the other typologies and operations that we’ve talked about but H.R. 3 2 3 because it uses these sub-protocols you’ll see transitions from subprotocol to sub protocol and we’ll talk more about that here in just a bit before we get too far into H.R. 3 2 3 I wanted to remind you guys especially if you haven’t watched the previous videos or read the other chapters that we’re actually talking about a basic voice over IP topology. So that means that we’re going to start off just like any other topology with DCP maybe some TFT be happening and of course the phones will probably be supported by Power Over Ethernet age 3 2 3 is a signaling protocol. So that means that we’re going to see things like registration dialing and calling lookups that might be 800 numbers or name resolution things like that.

And then just prior to getting into the RTP transport you have to negotiate the media session info and then RTP constitutes our transport protocol our DCP is our quality of service metrics for the transport protocol and then we’ll see HD up to four or five in Asia to each a two to five drop back into our call after the RTP to terminate the session and here is a look at our topology and we see the same components DCP server and the TFT server to provide for the startup services for the phones.

And then of course the the chassis itself that that is actually the call manager. Now the chapter talks about a couple of different vendors. So I spent some time there on a vi and Polycom both of them were doing the age at 3 2 3 suite.


This one happens to be the the Avaya so let’s talk a little bit of terminology here with a star 3 2 3 phones or endpoints. Those are called terminals in Asia. 3 2 3 Speak the gateway is much like you would think of a gateway when you hear that term it is really the the translation point between different kinds of networks or even different kinds of similar networks. The gatekeeper is really there for what we call call control services. So that might be whether or not a terminal is actually allowed on the network if we’re gonna keep track of what that terminal is doing so gatekeeper is not always part of the topology but the gateway is is one of the critical components.

The multipoint controller

And then there’s the multipoint controller and you can see here it’s four conferencing and things like that. So these are our main components. But on any topology you’re typically going to see a terminal and a gateway device All right so let’s talk for a second about some of the other components or objects that we see on every single laid out three to three topology and that is our sub protocols the one that you’re absolutely going to see all the time is H.R. 2 2 5

And in a truly standardized UN fooled around with to quote the commercials topology you’ll see Asia to four or five as well there are others a 2 3 5 4 security there are other annexes for these protocols. So let’s start with 2 2 5 2 2 5 is what we might call the beginning part of a three to three conversation it handles all of the things that we normally associate with signaling protocols. I register using H.R. 2 to 5 I call other phones with a set 2 to 5 we’ll dial numbers. All these things are two to five specific so here are some examples of Asia two to five conversations here.

If we take a look at the bottom pain to begin with we can see DCP and TFT. Now these are not all of the messages for those two protocols I just sort of snipped some but then we can see right off that we start into two to five and I’m going to point out something here. There are some of these two to five messages immediately following the TFT P that also say. RAZ All right. S after them under the info. Now that becomes important to us here in a second because that’s actually a typology that’s implemented the gatekeeper the two to five down below that is straight up call signaling for two to five without the gatekeeper functions and up above there we can see an example of an aged out 2 to 5 non.

RAZ message and one thing that I like to point out here is that 2 2 5 is the bottom and above that the actual part that’s expanded here is QDot 931 one QDot nine thirty one is actually part of or originates from ISDN call signaling. So H.R. three 2 Three makes use of packet ties. Q Dot nine thirty one signaling messages within Asia 2 to 5. So this is just a little more informal way of saying what I just talked about. So remember that you start to do five utilizes two signaling messages. So the same functions that are present on an ISDN network are present in packages from on an Asia three 2 3 IP based telephony or video call the razz portion or registration administration and sat as a gatekeeper function it’s not always there and that’s if you want to implement things like mission control for your network and then dial the bottom of this I just listed some of the common HDR 2 to 5 messages now Asia 2 4 5 and age 2 to 5 both have a collection of messages that are defined for them.


Some of them are mandatory. Some of them are optional and so you don’t always see every message utilized in Asia 3 2 3 conversation. So let’s talk about H.R. 2 4 5 for a second in this image we see a number of the messages involved here. Now remember that each that 2 to 5 is there sort of get your phone registered dial your numbers provide some mechanism for contacting the other phone things like that. The point of HR2 245 5. Is to set up the session for the actual multimedia communication. In other words you’re about to send data between two sides here. How do you want to do it. And so one of the obvious things that we need to do is figure out what codec we’re gonna use. But this is sort of a negotiation because you might be talking to or sending the transmission between our two terminals that are exactly the same or one terminal might have significant significantly larger set of capabilities.

And so part of Asia to four or five is to establish what the capabilities of your type and points are going to be and then what are the parameters for the call itself. And one of those is also hey what ports do you want to use with RTP. So that’s really what we’re getting into with 2 4 5. So we have this natural progression from H2 2 to 5 to HD up to 4 or 5. All right. I want to say thanks very much for stopping by. Remember that this has been the Packard guy to voice over IP chapter 6 and we’ve been talking about H.R. 3 2 3. And remember that each that 3 2 3 is the umbrella protocol for this signaling standard or the signaling protocol from the I.T. team. We also saw that we have the use of sub protocols in a shot three to three a lot more complex than the other two protocols much harder to read but there’s an awful lot of installed H.R. three to three out there. So in all likelihood if you’re doing voice over IP you’re going to run into three to three out there.


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