Subject: Re: data content identification

From: Scott Bradner <[email-masked]>
Date: Fri, 19 Mar 1999 10:25:19 -0500 (EST)

> I am looking for a method to identify voice packets on a data stream

why do you want to do this?

note that if its so someone can bill differently for the packets
I would expect that many of the users will adopt simple ways
to hide this from you

Scott

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This message came from the IETF IPTEL Working Group Mailing List.

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From: Edward Vielmetti <[email-masked]>
Date: Fri, 19 Mar 1999 08:48:35 -0800 (PST)

> > I am looking for a method to identify voice packets on a data stream

It would seem to be straightforward to look for long-lived flows at
roughly voice-sized constant data rates.  No matter what protocol is
being used to carry these flows, they should stick out pretty clearly.
(As long as no one is doing crazy "spread spectrum" stuff across the IP
port space).  Constant bit rate encoders will be easier to find than
variable bit rate encoders, and if someone is doing streaming media like
realaudio or video you might be confused by those.

It'll be harder to pick out voice the less it is real time - a "push to
talk" scheme running over any of the internet "chat" protocols will be so
much more bursty than the canonical H.323 application than it might as
well be a totally different beast for content identification purposes. And
you know that the people hacking voice over chat don't go to international
standards committee meetings very often....

-- 
Edward M. Vielmetti                                 ||        ||        
Consulting Engineer, Office of the CTO,             ||        ||        
Cisco Systems                                      ||||      ||||       
Ann Arbor, MI                                  ..:||||||:...:||||||:..   
mailto:[email-masked]                      C i s c o S y s t e m s 

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