Question Speedtest.net Automatically Selects Overall Slower Server?

[d.john27]

Hi everyone,

I'm pretty techie, but even I can't figure this out... This is my first post on a forum like this, so I thought I'd give it a shot.

On wireless OR wired connections, speedtest.net automatically selects my ISPs server since I have their internet. The reason behind this, would be because it gives me the lowest ping possible out of my surrounding servers, which makes sense according to speedtest.net's methodology for choosing the best server (see their FAQs). What doesn't make sense is why my speed (Wired OR Wireless) is always capped around 250mbps with a ping around 6-10ms. My ISP is a fiber company giving me 980/100 speeds, which I have confirmed before by directly plugging my iMac into the ONT (modem) and again with the router (Orbi RBK50).

Here's the interesting part, when I switch to a server ~6 miles closer than the automatically selected one, my ping increases ~10-15ms, BUT my speeds increased to the >900mbps on my ethernet connection and >650mbps on my wireless devices. I can also get these results on a few other speedtest sites too (fast.com/testmy.net/opensignal/etc.) so it's not just Ookla's speedtest.net site messing it up. (but there are some sites that show the capped ~250mbps speed making me believe they are connecting to the ISP server).

Question: Now, shouldn't the lower ping mean a better download speed or does that just mean my ISP's server is limited to that ~250mbps download speed? I can easily switch speedtest to default to the faster server, but I'm genuinely curious why the default server on speedtest, the one with the lower ping, doesn't give me the fasted possible download speed.

I've never run into this issue before I switched to fiber, and hey, I'm still getting the gigabit speeds so I'm not mad one bit, but this server speed difference has me very perplexed.
Thanks in advance to anyone who can answer this for me!!!
Stay blessed.

 

[Aeacus]

Question: Now, shouldn't the lower ping mean a better download speed

Ping is essentially response time and nothing to do with download/upload speed.

does that just mean my ISP's server is limited to that ~250mbps download speed?

That's quite likely. Might also want to contact ISP and ask about that specific server. Probably the load on server is big at certain points of the day, hence the download speed cap on it. Without the cap, high traffic can choke the server, which either results in a huge ping for everyone or flat out kills the connection to all involved.

 

[bill001g]

The ping time no longer really affects or caps download. This used to be a issue before they started to use window scaling...microsoft calls it something different than everyone else.

The limit used to be 64KBYTES. Since all tcp data is acknowledged this meant that a server could only send 64KB of data and then wait for a response that it was received. If we would take a case where the ping time was say 1 second...something crazy like it has 2 satellite hops in the path... the download speed would be capped at 64KB or about .5mbps. The ping times represent the time the server and client are delayed in communicating that data was received properly.

Modern stuff uses a window size that scales up to a very large number to reduce this issue. Very huge latency/ping times still impact the transfer speed but much less.

It tends to be impossible to predict why a server will only download at certain rates. Could be artificial bandwidth limits or maybe server cpu limits. It can also be if you take errors. It must retransmit data. This is the problem with the tcp window size scaling. The larger the window the more data that can be in transit and make it harder to retransmit. The tcp window size is generally temporarily lowered when errors are detected. This is how server and client figure out the optimum speed to download at.

 

[JohnMGotts]

I like to look at it in a less complicated way.
If ISP “A” provides you with 50Mbs and ISP “B” provides 300 Mbs,
Would you expect the ping rate to be different?
No, it’s a response time, the only bandwidth used is for the ICMP packet.