ADSL extreme slowdown & then huge speedup: what causes this?

[KatanaDV20]

Hey guys

I have a ADSL connection and last week it abruptly slowed down to BELOW dial-up level speed. My favorite game is flight simulator (FSX) and I download a lot of addon freeware planes for it. Average size of a download is usually tiny - about 15MB or so.

During the slowdown a 15MB download was timed to take *4 days* according to Operas intergrated download manager. Various speedtest sites showed my connection between 0 to 2 bp (yes *bits* per second) It was insanely annoying.

Called my ISP they did a line test and said all was good...the line could support upto 7MPS they said and there was no noise or interference. My router checked out fine.

For one week I endured this....and suddenly this last Friday I got back from work and went online to see if things had changed...and wow was it back. I now have a 5-meg connection.....2.5 times more than prior to the slowdown.That 15MB Airbus A320 download takes like 8 secs or something...I mean my connection is on fiya

Im just curious now...what would cause such a crippling slowdown and then a speedup like this?

 

[ncjok]

It's only guesswork at this stage as to what the root cause of your 'internet slowdown' was. To simplify things I might try to break it down into the following categories,

• End user: Router, PC, hardware/drivers/software or WiFi problems.
• Line: Low/wrong sync. Packet loss. Dropping.
• Back-haul: BRAS/IP Profile. Exchange-wide PL or latency.
• Remote server: Peering/routing. 'Congestion' w.r.t connectivity or hardware.

What I would suggest, to anyone for that matter, is to gain a somewhat basic understanding of the characteristics of your connection. This might involve familiarising yourself with, for example,

• Modem statistics: Modulation. Attenuation. Sync rate w.r.t (target) noise margins. Error rates and their impact, if any, on your apparent throughput or gaming experience.
• Basic analysis: Ping/traceroute to a reliable host such as bbc.co.uk. IP Profile check, if applicable.
• Throughput: Direct download from a reliable high bandwidth server, e.g. Debian or Ubuntu Linux UK mirrors. Don't need to get the whole thing, just an idea of the speed.

There's probably more that could be added such as any other tools which may assist in helping narrow down on the cause of a problem if one can be more specific about what is being experienced. Bear in mind that, depending on the ISP, there may be other helpful avenues to gain support such as their user forum (official or unofficial) or IRC channel which could save you from life-shortening script-reading call centre staff.

 

[DJMK4]

Use an ethernet cable? does it do the same?

Is it at a particular time of the day everyday?

Does it happen on all machines on your network? If not then it could be malware causing an issue on that particular workstation

How is it on the weekends?

What are ping times like during the slowdown, and during the fast times?

Sounds like a congestion issue somewhere along the lines, im sure there is a tool online somewhere which graphs out the exchange congestion. You have to enter details obviously, if you sign up on the BE forums, even if you are not with them, you should find this tool on their forums.

EDIT, here is the link to the tool

http://www.fruk.net/

Visit that page and follow the link for "f8lure", you have to enter some connection details including the exchange you are connected to if I remember correctly

 

[KatanaDV20]

Thanks for the detailed replies ncjok & DJMK4 Im checkin all this out now.

Line: Low/wrong sync. Packet loss. Dropping.

Yea that sounds familiar...the tech support dude ran some test that checked that. The other stuff you mentioned sounds real interesting - specially the congestion bit.

I keep hearin about "MTU" but dont really understand it and need to read more. Apparently you can tweak this but it done wrong can be a pain in the ass!

Sounds like a congestion issue somewhere along the lines, im sure there is a tool online somewhere which graphs out the exchange congestion. You have to enter details obviously, if you sign up on the BE forums, even if you are not with them, you should find this tool on their forums.

EDIT, here is the link to the tool

Thanks for that m8 That would be cool to see a display of congestion levels.

Not surprisingly Mon-Fri 1700-2200 are slowest hours, fastest are after 2300 on weekends.

 

[DJMK4]

No probs let us know how you get on with that tool, i was going to install it the other day but didnt get round to it.

Plenty of people on the BE forums are using it though, and iv seen screenshots of peoples results.