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Sync speed with different routers

Soapy
Grafter
Posts: 38
Registered: 01-10-2007

Sync speed with different routers

When I was first max’d, early last year my sync speed was 3700ish which gave me a 2.5 or 3mb connection speed. Since then my sync speed, has steadily dropped to about 2400, giving me a normal connection speed of 1.5 and occasionally 2mb.

I have always assumed that the drop in speed was due to my SNR target being increased by BT, as my SNR over the last 6 months or so has been showing around 15-16 after a modem reboot. (it used to be below 10 as I remember it when I was first max’d).

I have had periods of frequent disconnects, but all due to me playing with the router, or other problems not related to the line itself. Therefore I have thought that these dropped connections may have caused the SNR target to increase in steps to 15.

Over the last few weeks I maintained a connection for 17 days without a drop, therefore I was hoping that the SNR target would drop down. But after a reboot, I was still only syncing at 2400, with the SNR still at 16ish.

My router was plugged into an extension socket (but I have tried the router in the master socket without seeing any difference in sync speed).

I have 2 routers, a Belkin F5D7630 and an Origo ARS-8400. My normal router was the Origo, but I was getting similar speeds from the Belkin.

Tonight I bought a ZyXEL P-660HW router, and connected it to the master socket. I am now sync’ing at 3800ish, with an Noise Margin of 6 (vs SNR of 16 with the other routers)

(is the noise margin on the ZyXEL the same as the SNR on the Origo?)

Whenever I have tried the other routers in this socket, I have not had a sync speed near that.

Is the better sync speed due to the ZyXEL router being better that the others?

Also, if BT has set the SNR target for my line at 15 (as it looked like with the other routers), how does that impact on the ZyXEL router that seems to be syncing at 6? If BT was to drop the target for my line, would I sync at a high speed again?

Stephen
6 REPLIES
N/A

Sync speed with different routers

I'm no expert, but I'm not sure that the SNR is "a target"?

Surely, the SNR is a "measurement" of the current amount of noise on your line relative to the signal (on a logarithmic scale) - the larger the number the lower the noise relative to the signal (larger number = better).

Note - because of the logarithmic scale, even small variations in the SNR numbers represent fairly significant variations in the quality of the line's signal.

Unfortunately, I don't know whether "noise margin" is the same as "SNR" - although if I had to guess, I'd gamble that it might well be?

In my limited experience of 3 modems (USB & router), they can have a tendancy to "sync'" at slightly different speeds, even on the same line/conditions - and certainly, it's also likely that any one modem may be noisier, or less capable, to some degree, than another.
Soapy
Grafter
Posts: 38
Registered: 01-10-2007

Sync speed with different routers

By SNR target I was meaning the minimum SNR that the modem will try to sync at when it is connecting

My understanding is that when maxdsl is enabled, BT set the line so that the connection will try to sync with a SNR of 6. In this way the maximum stable sync speed can be reached. However if the line is not stable at this target (minimum) SNR of 6, then the minimum SNR sync value can be increased by steps of 3 until the line is stable. Each increase in target SNR means the line syncs at a lower speed each time the modem is rebooted.

It looked like with my old routers, that when the line was syncing, it was trying to sync such that the SNR would not be below 15. I therefore assumed that the value of 15 was a target that BT had set so that the line would sync at a stable rate. When I first had maxdsl, the line would sync at 9ish, not 15.

I was also under the impression, that if a stable connection could be held long enough, BT would drop the ‘target’ SNR by 3, but I have not seen evidence of that happening.

Therefore my basic question is/was, if BT does set a target SNR, and mine is 15 (as seen by the old routers), does my new router obey this target value when it is connecting, or does it ignore it and just try to sync with an SNR as close to 6 as possible. And if there is a target and mine is 15, if it was to reduce would my speed increase again?


Stephen
N/A

Sync speed with different routers

Have you tried a firmware upgrade for the Origo router from

http://safecom.cn/code/product/adsl/samr-4114/fm.htm

It upgrades it to a safcom which gives you loads of extras like a firewall. It makes it a very good router as I have 2.

The snr is confusing as each router doesnt report the same data some call it snr some say snr margin and they are different. The origo reports a margin and the higher the number the better. The snr is also effected by the connection speed the higher the speed the lower the snr goes.

So you can connect at 2 meg and have a snr margin of 20 connect at 6 meg and it mat drop to 10
N/A

Sync speed with different routers

I read about a DMT tool that can be used on some routers to increase the sync speed.


I'd like to know if some routers are better than others on long lines ?
Community Veteran
Posts: 14,469
Registered: 30-07-2007

Sync speed with different routers

Yes.

Different chipsets and software mean some routers will be better than others under certain conditions like long lines or noisy lines. Even different firmware versions within the same router can make a difference. For instance I get a different sync speed on my DG834 for 2.10.10, 3.01.25, 3.01.29 and 3.01.31 firmware versions and with the latest one I get a different speed between the UK and Australian versions. My Vigor 2600 always syncs at a lower speed than my netgear (usually around 200Kbs) and the D-Link I tried recently was different again.
N/A

Sync speed with different routers

And yet some people have said that the Draytek Vigor 2600 is good on long lines.
I suppose it's just a case of trying different routers.