[Cake] [Make-wifi-fast] [Bloat] dslreports is no longer free
moeller0 at gmx.de
Sat May 2 16:19:57 EDT 2020
in principle I agree, a NATed IPv4 ICMP probe will be at best reflected at the NAT router (CPE) (some commercial home gateways do not respond to ICMP echo requests in the name of security theatre). So it is pretty hard to measure the full end to end path in that configuration. I believe that IPv6 should make that easier/simpler in that NAT hopefully will be out of the path (but let's see what ingenuity ISPs will come up with).
Then again, traditionally the relevant bottlenecks often are a) the internet access link itself and there the CPE is in a reasonable position as a reflector on the other side of the bottleneck as seen from an internet server, b) the home network between CPE and end-host, often with variable rate wifi, here I agree reflecting echos at the CPE hides part of the issue.
> On May 2, 2020, at 19:38, David P. Reed <dpreed at deepplum.com> wrote:
> I am still a bit worried about properly defining "latency under load" for a NAT routed situation. If the test is based on ICMP Ping packets *from the server*, it will NOT be measuring the full path latency, and if the potential congestion is in the uplink path from the access provider's residential box to the access provider's router/switch, it will NOT measure congestion caused by bufferbloat reliably on either side, since the bufferbloat will be outside the ICMP Ping path.
Puzzled, as i believe it is going to be the residential box that will respond here, or will it be the AFTRs for CG-NAT that reflect the ICMP echo requests?
> I realize that a browser based speed test has to be basically run from the "server" end, because browsers are not that good at time measurement on a packet basis. However, there are ways to solve this and avoid the ICMP Ping issue, with a cooperative server.
> I once built a test that fixed this issue reasonably well. It carefully created a TCP based RTT measurement channel (over HTTP) that made the echo have to traverse the whole end-to-end path, which is the best and only way to accurately define lag under load from the user's perspective. The client end of an unloaded TCP connection can depend on TCP (properly prepared by getting it past slowstart) to generate a single packet response.
> This "TCP ping" is thus compatible with getting the end-to-end measurement on the server end of a true RTT.
> It's like tcp-traceroute tool, in that it tricks anyone in the middle boxes into thinking this is a real, serious packet, not an optional low priority packet.
> The same issue comes up with non-browser-based techniques for measuring true lag-under-load.
> Now as we move HTTP to QUIC, this actually gets easier to do.
> And the time measurements can resolve well below 100 microseconds, if the JS is based on modern JIT compilation (Chrome, Firefox, Edge all compile to machine code speed if the code is restricted and in a loop). Then again, there is Web Assembly if you want to write C code that runs in the brower fast. WebAssembly is a low level language that compiles to machine code in the browser execution, and still has access to all the browser networking facilities.
Mmmh, according to https://github.com/w3c/hr-time/issues/56 due to spectre side-channel vulnerabilities many browsers seemed to have lowered the timer resolution, but even the ~1ms resolution should be fine for typical RTTs.
P.S.: I assume that I simply do not see/understand the full scope of the issue at hand yet.
> On Saturday, May 2, 2020 12:52pm, "Dave Taht" <dave.taht at gmail.com> said:
> > On Sat, May 2, 2020 at 9:37 AM Benjamin Cronce <bcronce at gmail.com> wrote:
> > >
> > > > Fast.com reports my unloaded latency as 4ms, my loaded latency as ~7ms
> > I guess one of my questions is that with a switch to BBR netflix is
> > going to do pretty well. If fast.com is using bbr, well... that
> > excludes much of the current side of the internet.
> > > For download, I show 6ms unloaded and 6-7 loaded. But for upload the loaded
> > shows as 7-8 and I see it blip upwards of 12ms. But I am no longer using any
> > traffic shaping. Any anti-bufferbloat is from my ISP. A graph of the bloat would
> > be nice.
> > The tests do need to last a fairly long time.
> > > On Sat, May 2, 2020 at 9:51 AM Jannie Hanekom <jannie at hanekom.net>
> > wrote:
> > >>
> > >> Michael Richardson <mcr at sandelman.ca>:
> > >> > Does it find/use my nearest Netflix cache?
> > >>
> > >> Thankfully, it appears so. The DSLReports bloat test was interesting,
> > but
> > >> the jitter on the ~240ms base latency from South Africa (and other parts
> > of
> > >> the world) was significant enough that the figures returned were often
> > >> unreliable and largely unusable - at least in my experience.
> > >>
> > >> Fast.com reports my unloaded latency as 4ms, my loaded latency as ~7ms
> > and
> > >> mentions servers located in local cities. I finally have a test I can
> > share
> > >> with local non-technical people!
> > >>
> > >> (Agreed, upload test would be nice, but this is a huge step forward from
> > >> what I had access to before.)
> > >>
> > >> Jannie Hanekom
> > >>
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