All things related to multicast

[Dave Hartzell <>]

Bill Nickless wrote:

> Maybe the question we should ask about QoS approaches is "what packets 
> can we throw away?" rather than "what packets should be protected?"  
> Audio/video conferencing applications can answer the "throw away" 
> question rationally.  Also consider non-TCP bulk-data transfer 
> protocols; perhaps they should be allowed to blast UDP traffic without 
> TCP back-off behavior if they're queued at a lower priority than TCP 
> packets?


  I think we've got some headway into that direction now....the QBone 
Scavenger Service is exactly what you described: "What packets can we 
throw away?"  I'm not sure where Scavenger Service is at right now in 
terms of deployment, but the last I heard it was on the Chief Engineer's 
desk for approval.  Our testing has proven that the concept is valid, 
and does work with today's router implementations (CBWFQ).

From reading this thread, I've noticed a common trend, and that being 
that there are other issues involved here other than network congestion, 
like dirty lines, etc.  TCP assumes congestion if a packet loss occurs, 
and backs off appropriately.  This is an issue that the wireless world 
is dealing with today, where a dropped packet may be the result of a 
noisy air path or collision.  I'm not sure how that will be handled...

Dave Hartzell