Why is torrent speed slow through comcast?

I recently changed my internet provider from Frontier Fios to Comcast xfinity. Through Comcast, I get somewhat low torrent speeds.

Frontier Fios: 15 down / 5 up. Torrent speed 1.5 MBps.

Comcast xfinity: 15 down / 5 up. Torrent speed 0.5 MBps only.

Got up/down speeds using speedtest.
Testing through wifi only.
Frontier had provided their own router.
Using an old dlink router (tm-g5240) with Comcast.
Transport Encryption is on w/ torrent client to avoid throttling.

I'd like to know ...

Is Comcast throttling OR is it just congestion on Comcast side?
Will a new router help? I do remember getting 0.5+ MB/s w/ Time Warner few years back with same router.

What should I do get at least 1 MB /s torrent speeds?

hIpPy

Posted 2014-08-07T08:30:08.453

Reputation: 133

1Try changing the port used by the torrent software to one between 49153 and 65535. This may require opening the port in the router's and the computer's firewalls. – harrymc – 2014-08-12T06:43:41.413

Something to note is that I use Comcast in Portland, OR. My connection speed usually tests ~55mbps. I am typically downloading at 10-15mbps through uTorrent, though I have managed ~30mbps on a few high-seed torrents. – Thebluefish – 2014-08-12T21:21:24.040

@harrymc, did that already. – hIpPy – 2014-08-12T22:44:41.350

@Thebluefish, do you know why? – hIpPy – 2014-08-12T22:45:07.963

TBH I always thought it was my $3 router that I got on half-off day from Goodwill, but I've never been bothered to test it. A friend down in Phoenix has Cox's 150/50 package, I could try a direct torrent to him sometime in the next few days to test theoretical limits. – Thebluefish – 2014-08-12T23:31:04.763

Why don't you rent a WiFi router from Comcast and see if your results are any different. This way, you can see if its your DLINK or something else. Its my experience Comcast does not throttle your connection, but does set a monthly soft upload cap that they monitor for repeat overage.

You can also test congestion by testing at different days of the week and day. You can use this as a guide: https://www.google.com/get/videoqualityreport/ - You can see when congestion is lower and test speeds from a consistent peer. Can't speak for Comcast, but Time Warner and AT&T U-Verse oversubscribe.

– Sun – 2014-08-18T22:08:57.860

Answers

I find it unlikely that Comcast would throttle BitTorrent traffic so significantly since they got in hot water for doing that in the past. They still do shaping like any large ISP, but probably not enough to knock your speeds down in half versus Frontier. With BitTorrent there are so many factors that affect speed, it's challenging to figure out where problems arise.

An easy way to test if your BT speeds are truly capped at 500kBps is to try different torrents and configurations. I hardly ever see my speeds go above 1MBps on Verizon FiOS, so I might assume a cap too. But if I torrent a popular Fedora release, speeds easily go up to 7MBps. Doing tests like this at different times of the day can also help determine if this performance is congestion related. The pipes can get flooded after school/work, but should be pretty bare early in the morning. Testing over Ethernet versus wireless may show a difference, but probably not. FYI your ISP can look at patterns in your traffic and deduce that you're using BitTorrent regardless of your using transport encryption.

If the router worked with high BT throughput on Frontier, I don't believe it should have to be replaced to work with a similar connection system. Comcast may have specific settings for routers connected to its network, and that's a good question to ask about to support. If you're convinced it's the router, Comcast will be able to tell you which new routers/router-modem combos are compatible with its system. If you tell them your specific problem, they're likely to be more helpful.

You can also see this similar question about BitTorrent throttling.

Some VPN services promise no throttling for different transmission protocols.

dingdingo

Posted 2014-08-07T08:30:08.453

Reputation: 66

Frontier fios was a dedicated 15 / 5 Mbps connection so I would get constant 1.75MB/s if I would torrent few. I had to return frontier router. For comcast, I always get a 15 / 5 on speedtest but torrents are typically 0.5 MB/s and 1 MB/s rarely. So I think something is amiss. – hIpPy – 2014-08-13T18:52:27.740

I tried torrenting a fedora 19 release 3 times and got an average speed of 0.5MB/s. I'm going to try a new router shortly. I would also call Comcast if speeds are still low. Will report back shortly. – hIpPy – 2014-08-13T19:02:51.430

You're rather overestimating Comcast - what Comcast got in hot water was for interfering with the transmissions by dropping and faking BT packets to try to make users think BT was broken. Throttling is still allowed as part of their network management. – James Snell – 2014-08-14T10:57:44.363

1@JamesSnell is referring to "SandVine". With regards to throttling, Comcast was caught throttling NetFlix traffic... It wouldn't surprise me if Comcast throttled traffic from unknown ports, or encrypted traffic. – Sun – 2014-08-18T22:17:13.323

For Netflix vs Comcast, that was a plague on both their houses... Comcast said Netflix weren't delivering enough bandwidth to them and Netflix said Comcast were throttling them to get them to buy more (expensive) direct connections. It seems like Comcast was the bad guy but we'll never know the answer for sure. What is certain is that without more co-operative peering setups like http://linx.net the USA will be in for more of these shenanigans.

– James Snell – 2014-08-23T23:16:49.960

You're probably getting throttled. Not much else to say than what's already been said, but if you're using old networking equipment, Wireless B/G only, that can cause slow connection speeds... And, if the signal is moderate to low you're going to have packet loss. Wifi is already prone to duplicate packets and packet loss, distance can really affect the problem... Try using an Ethernet cable, see if it improves.

The Encryption/Decryption process is also a factor in download speeds, since every packet out must be Encrypted/Decrypted and every packet in must be Encrypted/Decrypted. Even on good machines this can be a problem.

Headless Bunny

Posted 2014-08-07T08:30:08.453

Reputation: 29

My ISP restrict the connection speed once you've downloaded over a certain amount of gb. EG, 2MB/s upto 20GB, then down to 500Kb/s after for the rest of the day.

Joey

Posted 2014-08-07T08:30:08.453

Reputation: 376

Good point, but I have not heard Comcast doing this yet. – hIpPy – 2014-08-19T15:55:36.290