4 ms·

> Basically, this is a really hard problem, since you can measure bandwidth only indirectly What do you mean? My ISP knows which package I bought and how conge

• syntheticcdo 6y ago
  The hop between your computer and your ISP is likely about 10-20% of the puzzle. Congestion control is necessary to find the optimal transmission rate across all the networks between your PC and the final destination (and back!).
  • im3w1l 6y ago
    Do you have any source for this? My preconception would be that either me-to-isp or server-to-their-isp would be bottleneck large portion of time.
    • syntheticcdo 6y ago
      Well let's take a look at the traceroute from my residential PC to Hacker News as an example: Tracing route to news.ycombinator.com [209.216.230.240] over a maximum of 30 hops: 1 1 ms 1 ms <1 ms 192.168.86.1 2 12 ms 11 ms 6 ms x.x.x.x 3 29 ms 32 ms 24 ms y.y.y.y 4 19 ms 21 ms 22 ms be23.clmkohpe02r.midwest.rr.com [24.33.160.66] 5 28 ms 22 ms 22 ms be27.clmkohpe01r.midwest.rr.com [65.29.1.34] 6 19 ms 23 ms 19 ms bu-ether31-vinnva0510w-bcr00.tbone.rr.com [66.109.6.54] 7 33 ms 31 ms 20 ms ae-13.edge2.Chicago10.Level3.net [4.68.37.137] 8 68 ms 69 ms 69 ms ae-0-11.bar1.SanDiego1.Level3.net [4.69.146.65] 9 71 ms 75 ms 69 ms M5-HOSTING.bar1.SanDiego1.Level3.net [4.16.110.170] 10 69 ms 77 ms 66 ms news.ycombinator.com [209.216.230.240] Hop 1 is to my router Hop 2 is my router to my ISP Hop 3, 4, 5, 6 are all routers within my ISPs network. Hop 7 is from my ISP into "the internet". Level3 is a major provider of interconnectivity. Hops 8 and 9 are within Level3's network. Hop 10 is finally to Hacker News, which indicates HN's "ISP" is Level3 directly. Only hop 2 is where my "400 Mbps" package limitation is in place. Only hop 10 is "server-to-their-ISP". I chose 10-20% as my intuition because, as you see, 10 routers were involved to get my packet from my PC to HN, and only 1 of them is constrained by my internet package.
      • im3w1l 6y ago
        Ok, but aren't those Level 3 pipes really really fat? And within ISP too? And besides, if they are overloaded, then packages will get rerouted iiuc?
        • Sesse__ 6y ago
          Packets don't get routed based on congestion, no. And while fat, L3's pipes are not infinitely fat (imagine how much overcapacity they would need to pay for to never be congested at any time of the week/day!).
      • usr1106 6y ago
        You measured delay to get an ICMP packet back. Is that strongly correlated to packets being dropped (causing resend)? As you see even your example, sometimes the time even goes down when you move "further". Not working the field, but I believe it's an incredibly hard statistical model, not that far away from random chaos for a remote observer in the general case.
      • usr1106 6y ago
        Interesting that you can traceroute up to the destination. Over the years I have got accustomed that it's not possible any more in most cases. Some router is not sending or dropping the ICMP packets I guess. Not sure for what reason. To save the load? To stop people (competitors) spying on them? news.ycombinator.com is no exception that it doesn't work: 5 a9k2-49-infra-dc2.dc3.poneytelecom.eu (195.154.1.118) 0.745 ms 195.154.1.188 (195.154.1.188) 0.865 ms a9k2-49-infra-dc2.dc3.poneytelecom.eu (195.154.1.118) 0.720 ms 6 lag-110.ear3.Paris1.Level3.net (212.3.235.197) 0.940 ms ae53.edge7.Paris1.Level3.net (212.3.235.201) 9.700 ms lag-110.ear3.Paris1.Level3.net (212.3.235.197) 0.955 ms 7 ae-0-11.bar1.SanDiego1.Level3.net (4.69.146.65) 139.415 ms 139.085 ms 139.031 ms 8 GIGLINX-INC.bar1.SanDiego1.Level3.net (4.16.105.98) 150.362 ms M5-HOSTING.bar1.SanDiego1.Level3.net (4.16.110.170) 140.286 ms 139.842ms 9 * * * 10 * * * 11 * * * 12 * * * 13 * * * (sorry, somewhat poor formatting caused by typing on the phone?)
        • usr1106 6y ago
    • deleted 6y ago
      [deleted]
• Sesse__ 6y ago
  Even if the ISP were the only place congestion could arise, how would it tell the sender?