Poor YouTube performance; Possible upstream bottleneck?

I am consistently having performance issues with my 50/10 Comcast Business Class connection. I am a network engineer, and I use this connection for both business and personal use. I have investigated the issue to the best of my ability.

Through troubleshooting I have eliminated anything within my network, including the Comcast modem, as being the problem. The performance issues consistently affect just portions of the internet; all Comcast-hosted services work fine, and most websites load fine. My most consistent issues are with the inability to stream Youtube videos. Anything higher than 240p tends to need long pauses for buffering. HD videos simply never start. It works better during off peak hours, but even when it does work, my Sprint 4G LTE phone (~10Mbps) far outperforms the Comcast connection for Youtube buffering and playback, even for HD content. Switching the phone to wireless so that it uses the Comcast connection proves the point -- the playback immediately becomes slow and has to buffer, but is seamless again as soon as I switch it back to the 4G connection.

This leads me to believe that there is a bottleneck either in Comcast's network, or at one of its peering points along the path from my modem to YouTube. The problem seems worst during peak hours, 5-9PM during the week and all afternoon on weekends. It is important to note that many other video services such as Vimeo and Hulu tend to work fine, (buffering at over 40Mbps!) during these periods, so it is definitely not a problem with my local connection but rather a an upstream issue.

Technical details:

I have a static IP block with Comcast @ 000.000.000.000/29. My biggest problem destination seems to be Youtube's Video CDN @ 208.117.224.0/19.  I have included a traceroute below showing the current path between these two networks. Hop 3 is my SMC-D3G, 50.76.151.222 is directly assigned to it.

jbrammer@dev01:~$ traceroute 208.117.255.8
traceroute to 208.117.255.8 (208.117.255.8), 30 hops max, 60 byte packets
1 192.168.17.2 (192.168.17.2) 0.909 ms 1.186 ms 1.486 ms
2 192.168.31.137 (192.168.31.137) 2.107 ms 2.312 ms 2.379 ms
3 000-000-000-000-static.hfc.comcastbusiness.net (000.000.000.000) 1.961 ms 2.666 ms 2.704 ms
4 73.58.232.1 (73.58.232.1) 15.202 ms 15.240 ms 36.961 ms
5 te-9-3-ur02.independence.mo.indepen.comcast.net (68.87.234.245) 13.713 ms 14.878 ms 14.975 ms
6 te-2-2-ar02.independence.mo.indepen.comcast.net (68.87.234.50) 14.583 ms 15.960 ms 10.050 ms
7 te-3-3-ar01.independence.mo.indepen.comcast.net (68.87.234.29) 16.158 ms 18.736 ms 18.789 ms
8 te-5-2-0-12-cr01.350ecermak.il.ibone.comcast.net (68.86.92.1) 34.424 ms 34.632 ms 34.817 ms
9 ix-9-1-0-0.tcore1.CT8-Chicago.as6453.net (64.86.137.29) 33.638 ms 33.385 ms 33.660 ms
10 64.86.137.18 (64.86.137.18) 26.091 ms 27.491 ms 27.666 ms
11 208.117.255.8 (208.117.255.8) 28.060 ms 22.743 ms 27.066 ms
jbrammer@dev01:~$

Thank you,

Jason Brammer
CCNP