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Author Topic: Anyone having trouble streamnig video?  (Read 9887 times)

kasperd

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Re: Anyone having trouble streamnig video?
« Reply #15 on: July 13, 2012, 02:03:54 AM »

So, I pulled out wireshark and the big difference I noticed between XP and the Win7 VM was the window size.  Under IPv4 with both OSs it was 64k but under IPv6 with XP it was around 16k and with Win7 it was a little over 64k.
That's interesting. Certainly something to keep in mind when debugging the performance. I am curious what they were thinking when they decided to decrease the window size when going from IPv4 to IPv6.

TCP was designed with a maximum window size of 64KB. That turned out to not be enough. A window scaling option was introduced, which can be used to increase the maximum window size. Avoiding the option for compatibility reasons made sense at the time XP was released. So at the time a window size of 64KB did in fact make sense. But I don't see why you would want to go any lower than that. And why exactly go lower for IPv6? It is not like IPv6 uses faster light than IPv4 and thus can achieve same performance with a smaller window.
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ghira

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Re: Anyone having trouble streamnig video?
« Reply #16 on: July 13, 2012, 03:39:04 AM »

youtube has been slow as to be unusable for me since the day before yesterday at least (possibly earlier
if I hadn't been using it).

wireshark revealed I was getting youtube via ipv6. disabling v6 on my lan has "solved" the problem
but clearly I am curious to know what this could be.

my ipv6 tunnel was via the paris server because London was full but I moved it to London yesterday
since there is now space there. no real improvement.
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ghira

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Re: Anyone having trouble streamnig video?
« Reply #17 on: July 13, 2012, 06:54:39 AM »

Googling "youtube ipv6 slow cisco" suggests that at least in my case there could be cisco-related
issues here involving ip inspect (or zbfw if I switched to that) or ecn. I will re-enable ipv6
this weekend and see what I can find.
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