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Bittorrent suffers, everything else fine?

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Bittorrent suffers, everything else fine?


I am a residential subscriber of a cable ISP. The connection is solid -- I am getting what I pay for according to all my speed tests (download and upload speeds).

But when I run Bittorrent, the connection starts to really suffer. My ISP recently put in a new CMTS on September 1st, and also started using a brand new block of IP addresses that are vastly different than the ones we had before. Before Sept 1st, Bittorrent ran fine. I could even be downloading a few files and also play an online game at the same time (as long as my upload cap was set low). Now? It really makes my entire connection suffer, and I am almost 100% certain it has something to do with their new CMTS. The connection just dies... we're talking 1000+ ms to the first HOP when Bittorrent is barely 30% using any of my internet connection down, and 1-2% up. I can run a speedtest that maxes out my download or upload and still load a webpage fairly fast... but Bittorrent is a huge problem.

I really stress that I have checked everything on my end (other programs aren't using bandwidth, no hardware/software firewall or antivirus conflicts, no OS limitations for simultaneous connections, and so on). I have called and talked with my ISP, and they have stated "we do not do any throttling or packet-shaping".

The reason I come here is to see if you guys had any ideas/thoughts on the CMTS side as to what my ISP might have done on this Sept 1st CMTS upgrade. Are there options to limit the number of concurrent connections for cable modems? Maybe they only allow X amount of connections, which is why Bittorrent suffers (since it is p2p software that connects to multiple computers to get a single file(s))... and also why regular speed tests, using a single server, do not suffer.

That's all I can think of: packet shaping/throttling of bittorent traffic (which they said they don't do)... or a limit on the simultaneous number of connections.

What do you guys think? Thanks so much in advance for your help. I know I'm not an ISP but this problem has been bugging me for days now. It was perfect before Sept 1st, then they had to go change their CMTS and mess up Bittorrent :P

oh yes, I did some packet scans directly connected to the modem and noticed broadcast traffic coming from mac address vendor 00:01:5c which is "Cadent". That might be the CMTS vendor they are using, but I'm not too sure.

Web Hog

Not sure if you remember those old Phone company commercials where neighbors would get upset with each other because there wasn't enough bandwidth. anyway, Cadent is a cmts company and yes, chances are they are throttling your connection. Question for you... from the modem's web page, can you tell what your upstream channel width is or the modulation downstream and upstream?
could be a case where they had to go to 64Qam downstream instead of 256Qam. that would give lower downstream throughput, but I would bet that there's a config set for throttling, where is a give modem is using more downstream or upstream throughput than others and it's hitting a given threshold, it will cut back on that one modem.
other than bit torrent, if you did an ftp download or upload, would the speed reflect the speed test you ran before? also, do they offer docsis 3.0? that could be a way around the problem. most that have gone to docsis 3.0 offer a min. of 50 Mbps down and 20 Mbps up, on average. depends on the company. Over in Japan they offer 100 Mbps and Canada 160 Mbps.

Here is some info I was able

Here is some info I was able to gather via DocsDiag and/or the cable modem's web page. Hope it can help in some way. If not I can look further with docsdiag if needed.

[Cable modem's web page]

Frequency: 111000000 Hz
Signal To Noise Ratio: 40.1 dB
Power Level: 4.5 dBmV
Channel ID: 22
Frequency: 24800000 Hz
Power: 39.4 dBmV

[DocsDiag -traffic]:

I also talked with a higher up tech further yesterday. They are now agreeing that it might not be a problem with me, but with the new cmts. He said they dont do any throttling in my town, and he also said the modem wasn't registering to their monitoring system or to the correct cmts which could cause a problem. Long story short, they are going to investigate everything on their end and get back to me. I've dealt with this guy for previous "unique" issues that I've had and he's been very helpful... so hopefully he will do good this time around too.

Update - I apologize I

Update - I apologize I didn't really answer all of your question: all speed tests and file transfers have been perfect.. I get my full speed up and down. This includes all speed test websites relatively close to me, and even my usenet account maxes out just fine. But Bittorent crushes the connection even when it's not using all that much bandwidth.

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