[dccp] RE: [MMUSIC] DCCP Media Guide

["Phelan, Tom" <tphelan@sonusnet.com>]

Hi Jonathan,

See inline ...

Tom P.

> -----Original Message-----
> From: Jonathan Rosenberg [mailto:jdrosen@dynamicsoft.com]
> Sent: Thursday, November 20, 2003 12:35 PM
> To: Phelan, Tom
> Cc: 'dccp@ietf.org'; 'avt@ietf.org'; 'mmusic@ietf.org'
> Subject: Re: [MMUSIC] DCCP Media Guide
> 
> 
> 
> 
> Phelan, Tom wrote:
> 
> > Hi Jonathan,
> > 
> > Thanks for the comments.  The actual proposal is to send up 
> to double the
> > nominal transmit rate when there's available bandwidth, and 
> to reduce the
> > rate as necessary if there isn't enough bandwidth.  This 
> doubling is to
> > allow fair sharing of the chokepoint bandwidth (between 
> DCCP media apps and
> > TCP apps), and to avoid what appears to me to be the 
> potential for bullying
> > from TCP applications that want to suck up all the 
> bandwidth they can.  It
> > doesn't preclude using low-rate codecs, or mean that the 
> access link must
> > support the double rate for the connection to function well.
> > 
> > This recommendation was meant for best-effort environments, 
> where the voice
> > traffic receives no special treatment, and must compete 
> with TCP apps for
> > network resources.  I can see how this would require a 
> network that gave
> > special treatment to voice packets to provision double the 
> capacity, though.
> 
> What about networks where there is also a lot of UDP traffic? For 
> example, these same networks providing voip traffic today. If I 
> incrementally add dccp support, it seems like I will need to increase 
> the provisioned capacity so I dont push out the UDP, no?

Yes, DCCP will behave towards UDP (and vice versa) pretty much the same as
TCP behaves toward UDP.  For streaming media apps following the guidelines
in the DCCP Media Guide, it actually can be a little better than TCP versus
UDP, because there is a maximum transmit rate.

> 
> -Jonathan R.
> -- 
> Jonathan D. Rosenberg, Ph.D.                600 Lanidex Plaza
> Chief Technology Officer                    Parsippany, NJ 07054-2711
> dynamicsoft
> jdrosen@dynamicsoft.com                     FAX:   (973) 952-5050
> http://www.jdrosen.net                      PHONE: (973) 952-5000
> http://www.dynamicsoft.com
> 

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