US Cable Support > Comcast HSI > [Speed] Comcast throttling streaming?

[Speed] Comcast throttling streaming?

Comcast doesn't throttle.

Since when? In 2008, they implemented a broad QoS policy to throttle heavy-bandwith-using users (»downloads.comcast.net/docs/Attac···ices.pdf). Also, they were once throttling Bittorrent traffic, but that's irrelevant.

My usage neither exceeds nor approaches the 250GB monthly cap, although I have no way of determining how it relates to my neighbors' utilization.

The only reason I suspected throttling or caching issues is b/c I saw the URL for a youtube video change from youtube.com to comcast.net when trying to stream something.

reply to ExoticFish

reply to dorkino
I don't think that's throttling.
First thing, are you using ComCast DNS?
If so caching, (with YouTube's cooperation) could actually be intended to move the stream closer to you (network wise) and save transport costs too.
That is if you're watching a stream from a west coast location, rather than transporting a stream for each east coast viewer across the country, CC could cache it to several east coast locations, refreshing the cache every few seconds or minutes and save a huge amount of traffic, while at the same time providing a shorter/faster/more direct path to your home.

Nope, I'm using Google's DNS. Maybe they do something similar?

google DNS may direct you anywhere (NOT optimized for the ComCast network in the case of (most) multihomed CDNs)
and redirection from that point to /through a ComCast link/proxy would be entirely a YouTube effort and also maynot be optimal for your actual location.
The only official CC link/proxy for YT content would be through the CC "VIDEO" links on Comcast.net.

If you could post an example URL, it might help.

reply to dorkino
Comcast has "congestion management" but they do not throttle.
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reply to dorkino
Try the DHCP provided DNS from CC and see what happens.

reply to Robotics

reply to dorkino
Just a couple of links for reference about Comcast congestion management vs. throttling:

»Comcast throttling USENET
»Is the Comcast Congestion Management System Throttling?
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I've tried removing the static IP entries in my router that point to Google's DNS servers. The problem still exists.

Here's an example link: »www.clarkhoward.com/videos/clark···e/vFgdc/

That took almost a full minute for the video to appear (the rest of the page loads almost instantly). The data is coming from brightcove.com. It doesn't have to be from there only though. The delays happen on pretty much any video stream, be it from Brightcove, Youtube, CNN, etc.

Edit: I should note that the problem affects anything that streams, including music. I just tried opening the 90s channel on 977music.com, and it took about 30 seconds for the player on the page to appear and the music to start.

I'm on a hard-wired connection using Comcast cable Blast! service. My speedtest (from speedtest.net): »www.speedtest.net/result/1719687251.png , Pingtest (pingtest.net): »www.pingtest.net/result/54979390.png Both speedtest and pingtest too about 20-30 seconds to initialize the page so I could start the test. The 1st pingtest caused my streaming music to stop and failed, saying it couldn't connect to the test server. After the error appeared, the music started again, and I ran the test again (which worked).

I've tried both Firefox and IE, both have the same issue.

Edit2: Ew. This doesn't look good: »/pingtest/966c···/2869342

Do you think it's a problem with my local service, or is it a problem somewhere upstream?

Ran a linetest again: »/pingtest/a428···/2869367

Seems even worse. If I'm reading that correctly, is it saying that my router only responded to a couple of pings out of 100? If that's the case, why can I run a ping test from whatsmyip.org and have 0% packet loss?

Edit: I ran a linetest to the next hop beyond my router/modem, and it has 0% loss (»/pingtest/9636···/2869378). Maybe it's time I start troubleshooting my installation here at home, yes? The interesting thing is, I'm running Tomato on an Asus RT-N16 router, and it has tools I can use to ping/trace directly from the router. When I try pinging or tracerouting to google.com, I see zero dropped packets.

Edit2: I just ran a ping test to that same gateway from my computer, and ping times averaged 10ms, with 0% packet loss after about 10 minutes of pinging.

So, I can run a line quality test to the gateway and it looks good, but a line test to my router shows horrible loss. Running a ping test from my computer to the router looks good, with 0% loss. Also running a ping test from my computer to the gateway has 0% loss.

I'm lost and confused.

Wait. Edit 3: Right now, videos are streaming instantly. I'll have to repeat these tests when the problem presents itself again.

reply to dorkino
try direct to the modem, with no router.
and be sure that the computer is using CC's DNS as assigned by dhcp. a full power cycle/cache clearing before testing should show the trusest baseline result

reply to dorkino

reply to dorkino
So this is still occurring. If I run a line quality test to my default gateway, it runs perfectly fine. But if I run it to my modem/router IP, which is one hop beyond the gateway, it has horrible loss. I've noticed the response time of the gateway varies between around 10-50ms.

What's weird is, during troubleshooting, I removed the router from the picture and hooked a computer directly to the cablemodem. The modem pulled a completely new class A IP (a 174.x.x.x vs the router's 24.x.x.x). So I put the router back in service and had it clone the PC's MAC so I'd get the new IP... thinking maybe I was given the wrong gateway to begin with. I started a line test and came downstairs to test on my main PC. The line test showed horrible drops still to the new 174.x.x.x IP, and when I ping the gateway, times ranged from 10-50ms again.

I removed the MAC clone from the router and then it pulled the old 24.x.x.x IP again. Same relatively slow response times from the local gateway.

My question is, why did a new MAC on my cablemodem pull such a drastically different (174.x.x.x vs 24.x.x.x) IP address?

reply to dorkino
Also, here is a ShaperProbe test. Earlier when I ran this, it failed the upload test due to too many lost packets.

DiffProbe release. January 2012. Build 1008.
Shaper Detection Module.

Connected to server 4.71.254.162.

Estimating capacity:
Upstream: 4348 Kbps.
Downstream: 31374 Kbps.

The measurement will take upto 2.5 minutes. Please wait.

Checking for traffic shapers:

Upstream: Burst size: 9696-9777 KB;
Shaping rate: 2128 Kbps.

Downstream: Burst size: 19038-19526 KB;
Shaping rate: 21280 Kbps.

For more information, visit: »www.cc.gatech.edu/~partha/diffprobe