I really wouldn't have an idea at this very moment, as it looks like the return path for both connections jive closely with the sending path. The latency is showing nothing out of the ordinary so I have no idea where the problem may be. I do notice one thing about the Comcast reverse route, and it seems that the particular link coming back is running over TATA, if I'm not mistaken who Comcast is known to overload their peering points with in the past. They don't look problematic though.
As a test, I'd like you to try something. Even though the server I'm going to link you to is not in Switzerland, it is in Europe so it should at least give us a rough idea on what could be going on. It sounds like something is still up to me with perhaps the server-end if the problem developed after Windows server patches were applied (I'm assuming they're running Windows based on the trace provided).
Run a few tests to this site and tell me what kind of results you get. You only need to do it on the FiOS, but if you wish to run it on the Comcast connection, feel free.
http://npad.iupui.mlab2.ams01.measurement-lab.org:8000/ (Do not post up the URL to your test. It gives your IP). Set this test to an RTT of 130, and the target rate to the rated speed of your FiOS connection, to the nearest megabit.
http://ndt.iupui.ams01.measurement-lab.org:7123/ (Provide the complete test results from the More Details section).
Both of the above servers are in the same path, however, here's a traceroute to the above servers. Notice Level3? Different route, different servers, different host. So this will effectively knock out a good chunk of the path as being the culprit, so to speak. Not set in stone but pretty reliable.
Microsoft Windows [Version 6.0.6002]
Copyright (c) 2006 Microsoft Corporation. All rights reserved.
C:\Users\>tracert ndt.iupui.ams01.measurement-lab.org
Tracing route to ndt.iupui.ams01.measurement-lab.org [213.244.128.164]
over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms 192.168.3.1
2 9 ms 9 ms 9 ms 10.15.3.1
3 9 ms 9 ms 9 ms so-1-1-0-0.BUFF-CORE-RTR1.verizon-gni.net [130.81.13.73]
4 20 ms 20 ms 19 ms as4-0.NY325-BB-RTR1.verizon-gni.net [130.81.20.104]
5 20 ms 20 ms 20 ms 0.so-0-0-0.XT1.NYC4.ALTER.NET [152.63.1.41]
6 20 ms 20 ms 20 ms 0.ae3.BR3.NYC4.ALTER.NET [152.63.16.181]
7 21 ms 20 ms 20 ms 204.255.173.54
8 20 ms 20 ms 20 ms vlan51.ebr1.NewYork2.Level3.net [4.69.138.222]
9 21 ms 20 ms 20 ms ae-4-4.ebr1.NewYork1.Level3.net [4.69.141.17]
10 89 ms 88 ms 88 ms ae-41-41.ebr2.London1.Level3.net [4.69.137.65]
11 96 ms 95 ms 95 ms ae-48-48.ebr2.Amsterdam1.Level3.net [4.69.143.81]
12 97 ms 97 ms 97 ms ae-57-222.csw2.Amsterdam1.Level3.net [4.69.153.206]
13 96 ms 96 ms 98 ms ae-2-52.edge3.Amsterdam1.Level3.net [4.69.139.169]
14 97 ms 96 ms 96 ms 213.244.128.164
Trace complete.
C:\Users\>
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Remember: YouTube is not a comprehensive benchmark. See the Google Product forums for slowdown issues.
Wireless issues? http://tinyurl.com/mfh3sud
