[e2e] Data flow models for real-time applications

[Fred Baker]

I think you also need to define "real time". The term derives from the  
historical milleiu around 1990. It is specifically defined in http://www.ietf.org/rfc/rfc1633.txt 
  to refer to communications that have a stated end to end delay  
requirement, which turns out to be more practically addressed as a  
bandwidth requirement - a voice or video codec will generally require  
a rate within a range or within one of several ranges. Fundamentally,  
the difference is by comparison to elastic applications such as those  
that run over TCP; they will adjust themselves infinitely up to a  
point derived from the retransmission or drop-dead configuration of  
the communicants, while real-time applications break in some way.

But there are a number of other applications that have real-time  
characteristics that are not play-back applications. Sensor traffic  
comes to mind; certain classes of sensors generate traffic at a  
certain rate, either regardless of circumstances or under certain  
circumstances, and if it doesn't get through there is no  
retransmission on the theory that it wasn't all that important. An  
example that has been proposed is with the CalTech Earthquake lab; if  
they had cheap seismometers built into set-top boxes in people's homes  
(say), whenever there is a jiggle above some threshold they could get  
an arbitrary number of UDP reports with a GPS location and a seismic  
reading. Now, that would have the characteristics of a DDOS attack  
(when there is a jiggle near CalTech, a *lot* of homes might be  
affected), so they had jolly well better have enough bandwidth in place.

So when you say "real time", what do you mean - voice/video playback  
applications? Sensor traffic, and if so of what types? Is there  
something else (I'll bet there is but haven't spent a lot of time  
thinking about it)?


On Feb 17, 2009, at 5:06 AM, Craig Partridge wrote:

>
> There have certainly been attempts to develop data structures  
> intended to
> model a real-time flow -- e.g. the ST-2 flow specs and token buckets  
> come
> to mind.
>
> But to better answer your question, I think you need to clarify what  
> you
> mean by "instantaneous model of a flow for real-time applications".
> What makes the model instantaneous?  (Do you mean you adjust it in
> real-time? Or that you can specify a sufficiently good model of the  
> flow
> before it starts?).  What are you trying to model about the flow?  
> (The delay
> constrained traffic within the flow? the total traffic load?  a  
> layered
> traffic/delay model?).  What is your definition of real-time?   
> (Sufficient
> for playback?  Sufficient for two-way conversation?).
>
> Thanks!
>
> Craig
>
> In message <55c1a2ac0902162347l69180e93uf79acf89207ca0e4 at mail.gmail.com 
> >, Guy -
> Alain Lusilao-Zodi writes:
>
>> --001636c5a72e60d25e04631882b7
>> Content-Type: text/plain; charset=ISO-8859-1
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>>
>> Hi All,
>>
>> I am working on a project which consist of developing an end-to-end  
>> quality
>> of service for real-time applications. The novelty of the project  
>> is to
>> develop an instantaneous model of flow for real-time applications  
>> or for
>> streaming video.
>> I would like to known if no one have never try to develop a model  
>> of flow
>> for real-time applications that can server as a basis for my project.
>> Also as PhD degree, this is suppose to be my contribution,  
>> therefore if the
>> work have already been done I will appreciate if you can provide me  
>> the
>> necessary informations otherwise I will be wasting my time.
>>
>> Regards
>>
>> -- 
>> ----------------------------------------------------------
>> G.-A. Lusilao-Zodi           voice : 0216554019
>> PhD in Video streaming  cell    :082687993
>>
>> Communication group    guylzodi at gmail.com
>> university of cape-Town
>> -----------------------------------------------------------
>>
>> --001636c5a72e60d25e04631882b7
>> Content-Type: text/html; charset=ISO-8859-1
>> Content-Transfer-Encoding: quoted-printable
>>
>> Hi All,<br><br>I am working on a project which consist of  
>> developing an end=
>> -to-end quality of service for real-time applications. The novelty  
>> of the p=
>> roject is to develop an instantaneous model of flow for real-time  
>> applicati=
>> ons or for streaming video. <br>
>> I would like to known if no one have never try to develop a model  
>> of flow f=
>> or real-time applications that can server as a basis for my  
>> project. <br>Al=
>> so as PhD degree, this is suppose to be my contribution, therefore  
>> if the w=
>> ork have already been done I will appreciate if you can provide me  
>> the nece=
>> ssary informations otherwise I will be wasting my time.<br>
>> <br>Regards<br clear=3D"all"><br>--  
>> <br>-----------------------------------=
>> -----------------------<br>G.-A. Lusilao-Zodi &nbsp; &nbsp; &nbsp;  
>> &nbsp; &=
>> nbsp; voice : 0216554019<br>PhD in Video streaming &nbsp;cell  
>> &nbsp; &nbsp;=
>> :082687993 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;  
>> &nbsp; &=
>> nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <br>
>> Communication group &nbsp; &nbsp;<a  
>> href=3D"mailto:guylzodi at gmail.com">guyl=
>> zodi at gmail.com</a> &nbsp; &nbsp; <br>university of cape- 
>> Town<br>-----------=
>> ------------------------------------------------<br>
>>
>> --001636c5a72e60d25e04631882b7--