MTU Problem: Akamai,HE,GTT

[Erik Nygren]

Can you pass me along a traceroute6 to 2a02:26f0:6a:18f::eed and I'll pass
it along to the Akamai NOCC?  (Or you can email details to noc at akamai.com).
>From here I'm able to ping it fine with large packets:

$ ping6 -s 1452 2a02:26f0:6a:18f::eed
PING 2a02:26f0:6a:18f::eed(2a02:26f0:6a:18f::eed) 1452 data bytes
1460 bytes from 2a02:26f0:6a:18f::eed: icmp_seq=1 ttl=52 time=105 ms
1460 bytes from 2a02:26f0:6a:18f::eed: icmp_seq=2 ttl=52 time=105 ms
1460 bytes from 2a02:26f0:6a:18f::eed: icmp_seq=3 ttl=52 time=106 ms
1460 bytes from 2a02:26f0:6a:18f::eed: icmp_seq=4 ttl=52 time=105 ms

Are any of the others Akamai IPs that you're having problems with?  While
we have intentionally not lowered our initial MSS (we don't want a broken
Internet where ICMPv6 PMTUD doesn't work), we very rarely hear of issues
and almost all of them end up being last-mile misconfigurations near the
end-user.

     Erik


On Mon, Sep 22, 2014 at 5:16 AM, Ignatios Souvatzis <ignatios at cs.uni-bonn.de
> wrote:

> Hi,
>
> for at least one weatheronline.co.uk seems to hang most of the time for
> some of my users. The reason is javascript code unconditionally loaded
> from connect.facebook.net.
>
> connect.facebook.net is an alias for connect.facebook.net.edgekey.net.
> connect.facebook.net.edgekey.net is an alias for
> e3821.dspe1.akamaiedge.net.
> e3821.dspe1.akamaiedge.net has IPv6 address 2a02:26f0:6a:191::eed
> e3821.dspe1.akamaiedge.net has IPv6 address 2a02:26f0:6a:18f::eed
>
> The latter two networks (or at least one of them) seem to block
> IPv6 packets of too large a size.
>
> I get replies to ICMPv6 echo requests with PING6(1280=40+8+1232 bytes)
> but not bigger; I suspect an icmpv6 black hole somwehere.
>
> However, some others show the same problem.
>
> Working (addresses shortened):
>
> 2001:638:a000:: (fully inside DFN), but also
>
> 2a00:19e0::
> 2001:608::
> 2001:200::
>
> so I think it's not a problem with two DFN internal tunnels I'm aware of
> (one inside Univ. of Bonn, one the UoB's next hop).
>
> Not working:
>
> 2001:470::              (routed through he.net)
> 2001:1900:2254::        (routed through he.net/yahoo)
> 2a02:26f0:6a::          (routed through gtt.net)
>
> I can workaround on my workgroup edge router, but I guess it would be
> more helpful if the real problem would be fixed.
>
> Regards,
>         Ignatios Souvatzis
>
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