On 10/9/2015 3:16 PM, David Lang wrote: ... >> Wouldn't it have been cleaner with more appropriate network provisioning? > > "more appropriate network provisioning" is not always going to result in > more bandwidth the way you want it to. > > If there is established infrastructure that can handle X in one > direction and 100X in the other direction, but "appropriate network > provisioning" requires that the ratio never be more than 3x, it's not > going to magically increase bandwidth in one direction, all it can do is > cap bandwidth in the other direction (throwing away capacity)
Sure, but we're dealing with a problem that arises when the ratio can't support 40:1. That's quite an asymmetry except in extreme cases where we already know extreme measures are required (e.g., satcom with telco backchannels). >> Why are you blaming TCP? > > first off, didn't you see the smiley? > > But treating your question as serious, it's because as RFC3449 shows, > highly assymetric networks or networks with other traffic on them don't > work with TCP the way you want it to work. So the option is to modify > TCP or tinker with the packets to leverage less commonly used features > of TCP (or features that are implicit in the design rather than explicit) The former is always on the table - that's what TCPM is for. The latter has always been problematic, exactly because it's subject to tragedy-of-the-commons. TCP is a contract between the endpoints, and whenever a middlebox starts modifying those packets, IMO it becomes a party to that contract that needs to be taken very seriously (smiley faces aside ;-) >> A DOCSIS router ought to route. If it left the packets alone, IMO we'd >> all be better off. > > So you would rather have people getting slower downloads than have > network equipment modify packets? I would rather people get slower downloads than break TCP in ways we won't see for 5 years or inhibit the extension of TCP in new ways that might be even more beneficial. > Those are the real-world choices. There were other cable modem companies that tried similar "tricks" in the past and got in a lot of hot water for making a box that went a LOT faster for *their* customers. TCP works when everyone plays by the same conservative rules. There has always been a choice to break those rules for individual gain, and there has always been a reason we try very hard to avoid that. Joe _______________________________________________ aqm mailing list aqm@ietf.org https://www.ietf.org/mailman/listinfo/aqm
