On 17/06/11 14:26, Doug Averch wrote: > Hi Wol: > > We have 10/100 mb router and find no problems. Most of our clients have > those or 1gb routers and find no problems. The reason to open more than one > connection is not be linear on the updates and allow the staff to do > something else than watch the update. Most of the time spent on > installation is creating files, updating indexes, compiling dictionaries and > compiling programs. None of these tasks requires any amount of data to > accomplish this.
That actually sounds exactly like the failure scenario ... > > We not moving that much data that we could overwhelm any of today's routers > or internet. Most of the data copied is dictionaries and programs which is > a few megabytes if that. Our biggest installation is about 20 megabytes. > And that makes sense too. When I made things fall over, I was trying to download a couple of DVD-sized chunks in parallel. What seems to be happening is that the hardware makers are increasing the size of router buffers, basically because ram is cheap, and there's this perception "that you mustn't drop packets". Problem is, TCP/IP relies on dropped packets to detect congestion! So all the buffering in all the routers backs up, and if you do succeed in overwhelming a router, TCP/IP stalls and you get a road-block. The backbone usually has plenty of capacity, as does the customer's local net. So the connection that fails is almost invariably the ADSL link between the customer and the net. (That's also why gamers curse - the bigger buffers lead to bigger latencies, and make internet game playing harder - I gather they often pay extra for routers with artificially restricted buffers precisely because it gives far better latency.) >From what I can gather, various ISPs have had failures of this sort, which they've tried to solve by throwing hardware at the problem. And, of course, as volume grew the problem hit again. Finally, some investigator's cottoned on and identified what seems to be happening - and said that throwing hardware at it makes the problem worse... And a lot of end-users have been hit by it since this trend of "accelerators" has come along. To an extent, that's actually what's helped identify the problem. As soon as I read the article, I was thinking "so THAT's why my connection keeps falling over - makes sense", because I had no problem running the downloads in serial, but as soon as they went in parallel, they failed. Cheers, Wol _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users
