Downstream speed = Speed test?

[WorriedNoodle]

We have a couple of ISP, True and TOT - both 10mbps basic starter packages in Bangkok.

For True, we have a True Nlink modem that displays a "Downstream speed" using modem access dislplay of 10547 kbps, whereas when I run Speedtest.net (Android or PC) I always get 9mbps result - and not 10mbps as I might have expected. With Trues own speed test (on their web site) the result is about 9.5mpbs inside Thailand, still less than 10.

* Question - when I run the same Speedtest on a TOT line with another modem I get a steady 10mpbs every day. Why do the speed test results (Speedtest or True) not reflect the full downstream speed on a True account, but do on a TOT account? Is it an issue with the True modem? Curious.

[RichCor]

The speeds are usually quoted as 'up to' and then only to their Network Operations Center.

Speedtest results can also be affected by other factors:

• Time of Day / User Contention for Resources
• Distance and number of hops to speed test server
• Capability and resources of device running the speed test
• Medium over which your connections are occuring

To give an example, my laptop directly connected via Ethernet cable will register near or better to the contracted speed on my FTTx circuit on the ISP's speed test, one of my Android phones will register 1mbps under, and yet another Android phone will register only half. My WiFi Access Point also has an undocumented 'feature' that allows full speed on the first SSID and then 50% speed on any additional SSID that throws off speed tests run over WiFi.

Though, if you can access the modem's status page, the reported downstream speed should be close to the ISP NOC speedtest when connected directly using an Ethernet connection.

[Pib]

A lot depends on how your particular modem and Internet Service Provider (ISP) report ADSL "overhead/control" bits/bytes, which is approx 15% of a plan's speed. Ex: a 10Mb plan which is really 10.24Mb (1.024Mb times 10) of pure "user data" flow will have "approx" another 15% (approx 1.5Mb for a 10Mb plan) in overhead/control bytes which means the plan's "raw" data rate is really up around around 11.75Mb---now whether this raw data speed is reported in your modem or just the "users data" speed will depend on the modem/ISP.

But if a person is say signed up for a 10Mb plan they should be able to pull a hair more than 10Mb on a speedtest to a local server...and the modem BIOS menu should be reporting at least 10Mb...anything less and there is a connection problem somewhere...most like a wiring problem somewhere...a funky/corroded connection at a junction box somewhere. Or if you live in a condo building, the building internal wiring could be funky which is usually out of control of your ISP. Be sure to run this test with an ethernet connection between your computer and modem to eliminate any possible Wifi router to computer speed bottleneck.

Around 4 years ago when I was on a TOT ADSL plan (I'm now on True DOCSIS/cable) the modem BIOS menus only reported the "user data" speed. I was on a 6Mb plan at the time and had two different modems while with TOT....on each modem the modem BIOS menu reported 6.144Mb download speed and I could get that speed in speedtests to local servers. However, from reading many posts over the years it seems "most" current ADSL modems/ISPs now report "raw data" speed in its BIOS menu which includes the ADSL overhead/control bits/bytes....but this overhead/control bytes/bits are "not" reported/measured when using speedtesters like Speedtest.net.

[WorriedNoodle]

OK thanks guys. I thought True was giving me only 9mbps on a 10mbps account as the result is always the same day or night, whereas on TOT it is always 10mbps day or night as per account. But with the information above and the various permutations involved as you guys helpfully explained, I'll let True have the benefit of the doubt this time.

[Pib]

If you are paying for a 10Mb plan you should get 10Mb using the ISP's speedtester or similar speedtesters to local servers. When you don't get such speed, checking the modem BIOS menu for what data speed it's reporting is a first step to determine if the problem is the line "coming to" the modem or a speed problem "after" the modem. For a 10Mb plan I wouldn't want to guess what speed the modem's BIOS should report (i.e.., 10.5, 11.0, 11.5Mb, etc) to account for the ADSL overheat bytes but using a figure in the 10 to 15% ballpark will get you close...of course this assumes the modem/ISP network is setup to report "raw" speed in the BIOS menu versus just "user data speed" you have signed up for (i.e., paying for 10Mb speed).