H323 Simulation

Discussion related to the ITU-T Recommendation H.323
durani01
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Re: H323 Simulation

Post by durani01 » Sat Sep 15, 2012 12:45 pm

Dear Sir

Besides our discussion on the said topic. I have discuss you with my family, specially my mother and my elder and younger brother. They are very impress from you.
My mother specially praying from Allah for your health, wealth, success and prosperity. And hope that you will guide me in this research till end.

Q 1. What are the jitter buffer requirements?
Q 2. What are the requirements of AMR-WB?

Am I going to start from the right way to my analysis?

I am studying RFC-4867
3GPP TS 26.114 Ch.No. 8 for jitter buffer requirements.
3GPP TS 26.171 for AMR-WB requirements.

Waiting for your positive reply.
Regards

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paulej
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Re: H323 Simulation

Post by paulej » Tue Sep 18, 2012 5:00 am

I apologize for my late reply. I have been very busy lately, as we have an upcoming meeting of ITU-T SG16 (focused on H.323, H.248, H.325, telepresence, etc.)

For your questions, I do not have an answer for what the requirements are. Broadly, you just want to try to play audio packets as quickly as possible, but not so fast that you see a buffer underrun problem with high frequency. If you often run out of packets because of delay in receiving the packets, you need to lengthen the jitter buffer.

I'm sure that people have done test to determine a reasonable jitter buffer. In general, I would hope that no more than 60ms would be buffered. However, the optimal size depends on delay and jitter in the network. This will vary from wired and wireless networks, as well as how far packets have to travel and whether there are any satellite hops in the end-to-end path.

durani01
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Re: H323 Simulation

Post by durani01 » Tue Sep 18, 2012 5:30 am

Dear Paul

Thank you very much for your reply.
I thought if you mind anything and thats why you are not replying, please forgive me.
Sir I understand.

Sir the literature which I am studying is correct or not.

I am studying RFC-4867
3GPP TS 26.114 Ch.No. 8 for jitter buffer requirements.
3GPP TS 26.171 for AMR-WB requirements.

I have started my analysis. and will discuss with you definitely.

Regards

durani_01
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Re: H323 Simulation

Post by durani_01 » Fri Dec 28, 2012 10:31 am

what do you mean by "Media Transmission Mechanism" in VoIP, explain?

We want to send and receive data on different data rates using a single computer.
Is it possible?
If yes, then how?

How we will create, send, receive and listen a voice packet of 20ms?
How we will create, send, receive and listen a voice packet using a single PC?

waiting for your positive reply.

Regards
Jawad Durrani

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paulej
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Re: H323 Simulation

Post by paulej » Fri Dec 28, 2012 11:18 pm

I really don't understand your questions entirely, but I think the best solution is to perhaps look at some open source VoIP products to see how they do it.

durani_01
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Re: H323 Simulation

Post by durani_01 » Sun Dec 30, 2012 7:47 am

Thank you very much sir.

In the above discussion
"Simulate an adaptive jitter buffer and study the behavior of AMR-WB in VoIP envoirnment"
From that description, I don't think you'll need to implement any call signaling at all. The only thing you'll need to do is implement a media transmission mechanism.You could use RTP (which would be reasonable, since that is what all VoIP systems use). That is documented in RFC 3550 and RFC 3551. There are other RFCs that document different payload formats. The payload format for AMR-WB is documented in RFC 4867.
what do you mean by "Media Transmission Mechanism" in VoIP, explain?

Second
We want to send and receive data on different data rates using a single computer.
Is it possible?
For example
We create two logical clients C1, C2 on a single computer and C1 sends data to C2 on different data rates.

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paulej
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Re: H323 Simulation

Post by paulej » Sun Dec 30, 2012 9:15 am

By "media transmission mechanism", I meant some way of sending packets (e.g. RTP over UDP).

You can certain send packets from one port on a machine to another port on the same machine. However, you will not be able to observe any network delay issues. Likely, you will see minimal delay variance by sending packets like that, too. Some of the behavior one sees sending over the Internet is important to study and understand, and it's very different than just sending packets locally on a machine.

durani_01
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Re: H323 Simulation

Post by durani_01 » Tue Jan 01, 2013 4:34 am

Thank you very much for your kind reply.

I understand what you really mean.
You can certain send packets from one port on a machine to another port on the same machine. However, you will not be able to observe any network delay issues. Likely, you will see minimal delay variance by sending packets like that, too.
Is it possible that we create logical, means through programming we create artificial traffic. which represents network traffic. If yes then please elaborate.

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paulej
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Re: H323 Simulation

Post by paulej » Tue Jan 01, 2013 7:56 pm

Sure, but you have to understand what you want to simulate.

Packet networks are not isochronous like TDM networks were. There will be a certain amount of delay that goes end-to-end. You would have that with TDM, too, but packet networks also experience jitter, packet loss, and out-of-order delivery of packets. So, you would want to simulate those things:
  • some delay that might may vary with the call or increase or decrease over the span of a few minutes; this is not the same thing as jitter, but a measure of the end-to-end delay that exists at some moment in time. That can change due to changes in routing in the Internet that might happen at any time.
  • some jitter that might vary by packet or increase or decrease over the span of a few packets or few dozen packets (G.711 with 20ms framing produces 50 packets per second and jitter can be observed with just a few packets). Jitter is the result of changes in the number of packets entering router queues, variations the routers ability to process queues at any given instant, etc.
  • packets get out of order when they travel down different paths over the Internet. From any two points in the Internet, there may exist multiple paths over which packets might flow and the order of delivery can change if one packet takes a different route than another.
These are all things that can be simulated, but I cannot tell you how to write your code to simulate them. You'll have to experiment to get an idea of what real-world traffic flows look like and how to best simulate it. But, these are the things you need to consider.

durani_01
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Re: H323 Simulation

Post by durani_01 » Thu Jan 03, 2013 7:11 am

Dear Paul

Thank you very much for your such a continuous support.
I understand.

Sir
How we will send and receive data with different data rates, using a single machine?

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