North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Congestion control train-wreck workshop at Stanford: Call for Demos
> On Wed, 5 Sep 2007, Stephen Stuart wrote: > > > > [...] > > If there is no congestion, then this conversation serves no purpose. > I'd like one infinite improbability drive too. Sure. When mine arrives, I'll drop it into my matter replicator so you can have one. :-) > > Let's say our example student is capable of generating 95% of flows by > > virtue of having access to 95% of the IP endpoints in the example > > network. How do you envision the OS notion of "user" helping you > > implement a per-user notion of fairness on the backbone? > > That's why I don't think operators care about "users" or "endpoints" but > they do care about who is paying the bills. Operators care about the > relative "fairness" between bill payers, not flows, sessions or users. > > Suppose MIT has a /8, Harvard as a /16; if MIT figured out they could get > more backbone bandwidth than Harvard by multiplexing its "flows" across > more addresses, and starving Havard students of backbone capacity. > Suppose Harvard was paying for 50% of the backbone cost, while poor > MIT could only afford to pay for 10% of the backbone cost. > > If the congestion point was always at the backbone edge, you might be > able to accomplish this by making Harvard's connection bigger than MIT's > connection. But lets imagine instead, during periods of little congestion > you want both Harvard and MIT to use as much of the backbone as they can, > and only when there is congestion do you want to "share" the backbone > congestion "fairly" between them. Yes, that's the notion that I was trying to convey. I agree that operators don't care about users, my reason for steering the conversation back toward them is that what kicked this sub-thread off was the assertion that knowledge of user by the OS at a TCP endpoint could somehow provide relevant information for resource allocation in a network such that congestion is divided among users. Techniques for trying to impose how congestion is "fairly" shared among flows exist and aren't what we're talking about. Could a technique be developed that used a notion of "user" in a network? (From Fred's reply, I think that's what we're talking about.) I'd argue that if it could it would be complex and therefore unsuitably fragile in a service provider environment, and would lose all relevance the moment a congestion point at an administrative boundary was crossed. Stephen
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