[ NNSquad ] Re: Routers deal with IP information

[Richard Bennett <richard@bennett.com>]

Unfortunately, I have to agree with David Reed on this point. I was 
formerly under the mistaken impression that IS-IS routers preferred to 
drop largish TCP segments over UDP packets and TCP ACKs until quite 
recently, but have learned that this thinking never advanced past the 
idea stage. Most of your IS-IS routers today simply implement RED and 
only apply different dropping strategies across streams with different 
CoS settings. In the Internet core, it's all pretty much the same.

TCP and UDP may be treated differently by management systems such as the 
Ellacoya traffic shaper (apparently used by Bell Canada,) Sandvine, and 
others, but this is a feature that's under the owner's control. Reports 
from Canada indicate that uTorrent 1.9 does in fact escape traffic 
policing at the moment, much to the chagrin of P2P over TCP users and 
VoIP over UDP users.

I expect this situation to change, but can't say in which direction it 
will go.

RB

David P. Reed wrote:
> One more correction of a complete boner by "expert" George Ou:
> > Because UDP end-points don't respond to dropped packets the way TCP
> > end-points do, most routers leave the UDP traffic alone when there is
> > congestion and they only drop TCP packets which respond by cutting their
> > flow rate in half. 
> This is UTTERLY false.  Perhaps if Mr. Ou worked for a router company 
> instead of making up fantasies in his own mind, he'd understand this.  
> (it may be that "NAT boxes" do such things, and are often called "home 
> routers", but routers do not - the generality of the statement is 
> awesome in its ignorance).
> > Besides, there's no point in forcing a 30 kbps gaming
> > UDP data stream to slow down because it's already very slow and it's 
> > only
> > fair to ask the bursty applications that have no bandwidth limit 
> > operating
> > at 100 to 500 times faster to take a hit on bandwidth.
> >   
> Like most people who are not on solid ground, he has to give details 
> of "why" his fantasy must be true.
> > Now here comes BitTorrent with their well-meaning but problematic 
> > change to
> > take a bulk file transfer protocol and stick it on UDP.  So instead 
> > of tiny
> > 30-80 Kbps VoIP and online gaming UDP streams, we're now looking at 
> > multiple
> > UDP streams operating at 15,000 Kbps per user.  Now we're forcing the
> > network operator to change their routers inside the Internet to start
> > managing UDP flows by dropping UDP packets whenever a link is congested.
> >
> >  
> RTP streams such as streaming video are *designed* to handle dropped 
> packets.  That's the one of the main reasons we invented UDP - in 
> particular, Danny Cohen, who created the field of packetized speech 
> over the Internet pretty much from the whole cloth, taught me why.
>
> Ou is close to impeaching his credibility here.

--
Richard Bennett