Perfomance very up and down in Cambridge

[MTD]

I am based in Cambridge, and for the past couple of weeks or so my 4 mbps broadband connection with NTL is very up and down. Basically performance keeps stalling. When it flies, eg on a good moment, with www.speedtest.net I seem to be getting around the 4 mbps rate, but on some measurements with speedtest.net you can see it stalling and the averaged speed comes out considerably lower.

Running Robin Walker's quick test shows this effect:

Fri, 03 Nov 2006 05:28:44 GMT
1st 128K took 265 ms = 494611 Bytes/sec = approx 4115 kbits/sec
2nd 128K took 271 ms = 483661 Bytes/sec = approx 4024 kbits/sec
3rd 128K took 265 ms = 494611 Bytes/sec = approx 4115 kbits/sec
4th 128K took 3723 ms = 35206 Bytes/sec = approx 293 kbits/sec

The 4th test is incredibly slow, as you can see. This sort of inconsistency is reproducible.

http://www.adslguide.org.uk/tools/speedtest.asp clocks my connection speed as

Downstream 1,159.2 Kbps ( = 1.1 Mbps )
Upstream 230.2 Kbps ( = 0.2 Mbps )

This goes up and down with different runs, but in the past has been consistently high.

From a user's perspective, it means that loading web pages can end up being incredibly sluggish and unusable for some pages. Moreover, downloading system updates stalls and doesn't work.

I don't think I am asking for help specifically, but to know whether this is something that is becoming common around NTL, whether it is specific to me, and if I phone NTL what exactly to ask or expect from them (I note that many people claim that calling NTL doesn't help).

Other details about me in case they are needed: I use a Mac OS X 10.4.8 (have tried various things to check that it isn't the computer at fault), I can't run all the tests people recomment because they are windows-only, I am not sufficient an expert to do a lot here beyond run the tests above. I have a Terayon cable modem connecting via my ethernet port (not usb). I run these tests at 5 am in the morning when I expect low levels of competition from others in the street, but the problems persist throughout the day.

[Heedyheed]

.....I run these tests at 5 am in the morning when I expect low levels of competition from others in the street, but the problems persist throughout the day.
As you're running your tests in the early hours of the morning, have you checked the service pages to ensure that NTL aren't changing things in your area at that time?

Mike

[Will73]

MTD,

I'm in Cambridge and my 4Meg connection has also been a bit erratic of late. Although not quite to the extent as yours sounds.

I used to get a steady 3.8Meg constantly, but over the last few weeks the speed test above has given results of 3.3, 2.8, 3.6, 3.8 etc

I'm putting it down to NTL upgrading or just playing about with the network in this area. I don't know though...

[MTD]

As you're running your tests in the early hours of the morning, have you checked the service pages to ensure that NTL aren't changing things in your area at that time?

Mike

Yes, I checked. Nothing appears to be happening that NTL are telling us about. I chose 5 am in order to avoid contention - it is up and down in performance most of the time, but during the day you can't exclude the possibility that someone in the street is doing a lot of downloading.

[MTD]

I have a Terayon cable modem connecting via my ethernet port (not usb).

Just to add one point of detail ...

One text case is a 50 MB download (the X11 update from Apple), which I cannot complete due to time out errors. I follow the lights on the front of the model (Terayon TJ210). The data light alternates between rapid busts of on/off flickering when my computer thinks it is receiving data and long pauses with no green light. I am slightly more worried by the fact that the cable light blinks off at random points during the data transmission stage. Is this significant?

Thanks to anyone who has any words of wisdom.

[MTD]

The problems I had have reached a satisfactory conclusion.

For anyone interested, the problem came down to a failing modem. It was apparently rebooting quite often, causing a lot of packet losses and hence an apparent slow speed.

I called NTL support, and having anticipated long waits and not much help, I was pleasantly surprised at getting through to someone almost immediately, and they were able to work with me to run a set of tests to identify the problem. They called out an engineer to replace the modem, and the engineer arrived well on time and completed the task. He also allowed me to run my own tests while he waited.

Overall, good performance by NTL to help fix the problem. Happy ending!