> It's not about "that's all they need", "that's all they want", etc.
Whenever any vendor spouts "this is what our customers want" you know they are talking pure bullshit. The only customers who know what they "want" are the microscopic percentage who know what's actually possible, and we are dismissed as cranks. Even though they keep hiring us to run their networks. In the spirit of adding real data to the symmetry conversation, let me describe why I would prefer symmetric. Currently I have all-copper DSL running at 3 Mb/s down and about 640 Kb/s up. There are days I wish I had 1.5 Mb each way, as there are times when I need to push large files out (well in excess of 1 GB each). Doing that now is painfully slow, but I can live with the long transfer times because I'm not doing it every day. Where it is painful is how the clogged pipe breaks other things. The big one is my SIP phone service. Because the ACKs on the file upload come back faster than the data can leave, it's almost impossible to avoid queueing delays in my border router, despite it being a real UNIX box vs. a cheap appliance NAT router with buffer bloat. TCP doesn't deal well with the asymmetry, so the only way to address this is to drastically reduce the sendspace window on my uploading box in order to throttle it back to where TCP's flow control works as designed. So do I hack FTP and ssh on my machines to take a command line option to squash the sendspace? Or worse, do I use the existing knobs to turn sendspace down for the entire host? Neither one is pleasant, and I shouldn't have to implement either. Having a DSL link that allocated bandwidth based on real-time need would solve this for me. But since that's not an option, converting the link I have from ADSL to SDSL would solve my problem. I would gladly trade in a portion of my downstream *bandwidth* for a corresponding reduction in my upstream *latency*. And I suspect a lot of those bullshitting ISPs would find this is "what our customers want" if their customers ever learned that it is this asymmetry that underlies many of their perceived performance issues. Mind you, the truly annoying part of this story (for me) is knowing Telus has fibre pedestals not a block away, with enough bandwidth to serve up IPTV to all the condos in the neighbourhood. But I'm in the marina across the street. Since there are only a handful of us here with service of any sort, they aren't about to come out and reroute us to the fibre pedestal. So I get to stay on the very long and corroded copper circuit back to one of the original downtown Vancouver exchanges. As one of the Telus techs said when he came out to help troubleshoot a failing DSL modem: I am amazed it works at all :-) And he's right -- the dB line losses are horrific. --lyndon
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