One tidbit that is interesting: dwred on the cisco gives non tcp packets the lowest possible ^^^^^^
non-ip .. sorry.
priority. Thus, with an aggressive drop pattern (depending on how you have configured minth, maxth and exponential weight on the router) you will run into a problem.
I am not sure as to who has dwred configured on congested interfaces at exchanges. You can throw packets into one of 8 precedence levels @ your border and then craft red to select harshly against low vs. high priority. However, upon observation of a network without car matching certain types of traffic and setting priorities, i see about 3 orders of magnitude difference in packets moving at the lowest precedence compared to packets moving at higher precedences. RED considerations are not necessarily the cause of your problem, but it is a possibility which is worth investigating.
more cisco implementaion specific information at: http://www.cisco.com/univercd/cc/td/doc/product/software/ios111/cc111/wred.h...
BR