ipv6 sloooow tonight

[#1]

Noticed youtube videos crawling along (youtube is ipv6 enabled).
Did some speedtests and here is results (note I repeated the ipv6 test multiple times to confirm and its 4.30am).
ipv6

ipv4

The huge gap between x6 and normal is bizarre but the single threaded result is bang on to youtube throughput.

[#2]

So I will continue to update even tho noone has shown interest (testers and staff alike).
TBB single threaded tests continue to max out at around 3mbit./sec.
youtube is not consistent its usually 3mbit/sec throughput but sometimes is line speed.  So I am thinking now either plusnet are testing traffic management with some routes rate limited, or there is an issue on some ipv6 routes.
Need others to test and staff to respond really.

[#3]

As requested. Both results were carried out using the ipv6test account. I disabled IPv6 in the network properties of the adapter to get the IPv4 result.
IPv6

IPv4

[#4]

Could you do us a Wireshark of the v6 traffic? I need to check something with the network guys but I have a feeling I know what it is, the Wireshark will prove it.

[#5]

ok thanks for both replies, will do a wireshark as soon as possible.

[#6]

not very good with wireshark, I tried to apply a ipv6 only filter but still lots of lan stuff in there.
then I cant figure out how to get the result onto here.
any quick howto anywhere?

[#7]

If you close any background running programs - that will help.
It's fairly easy to filter out traffic on there (put ipv6 and !(tcp.stream eq 0) in the filter bar and you'll see).

[#8]

ok and then how to paste here? I see no way to select.
seems have to do a screenshot instead?

[#9]

trying to attach screenshot but forum hangs forever. bear with me.

[#10]

trying to attach screenshot but forum hangs forever. bear with me.

[#11]

another, I seem to have small tcp window size.

[#12]

It's a bit strange how your IPv6 speed test doesn't show up on your IPv6 TBB Ping Monitor like it does on your IPv4 TBB Ping Monitor.
Which router are you using by the way?

[#13]

I am using an asus ac66u
ok so I ran the analyser test here.
http://netalyzr.icsi.berkeley.edu/
something of interest from the results.

Quote

IPv6 Tests +    –   DNS support for IPv6 (?): OK +     IPv4, IPv6, and your web browser (?): IPv6 connectivity problem +     IPv6 connectivity (?): OK – Your host was able to contact our IPv6 test server successfully. The requests originated from 2a02:16c8:2000:1400:c911:xxxx:xxxx:xxxx. It takes 832 ms for your computer to fetch a response from our test server using IPv6, while it takes 196 ms for the same host to fetch a response using IPv4 from the same server.   IPv6 TCP connectivity (?): OK +     IPv6 Path MTU (?): Warning – Your system can send fragmented traffic, but can not receive fragmented traffic over IPv6. The path between your network and our system supports an MTU of at least 1496 bytes. The path between our system and your network has an MTU of 1500 bytes. The path between our system and your network does not appear to handle fragmented IPv6 traffic properly. IPv6 Traceroute (?): OK

The tests do show and affect ipv6 but the affect is more normal, the affect on my ipv4 traffic I dont consider normal, maxing out the line via a speedtest shouldnt cause packetloss and spike latency so high (which it does on my ipv4), I mentioned this on the tbb forums recently, but I dont think anyone else sees anything wrong with it.

[#14]

due to the fragmentation errors and that I know I am using a mtu of 1500 bytes, I adjusted my ipv6 mtu down to 1400 just to be sure that isnt the cause and can confirm a mtu of 1400bytes on my ipv6 does not change the behaviour.

[#15]

Wireshark didn't prove what I thought but has given me another idea, chrcoluk I think you may be on to something with the packet fragmentation.
Is anyone seeing a problem on ADSL? If it's just fibre then it could be something to do with the 1492 packet size on PPPoE whereas most people on ADSL with be on 1500 MTU. Need to do some more digging and testing.