Some very nice broken IPv6 networks at Google and Akamai

Jeroen Massar jeroen at
Tue Nov 11 20:13:40 CET 2014

On 2014-11-11 19:09, Andras Toth wrote:
> On Tue, Nov 11, 2014 at 3:36 PM, Jeroen Massar <jeroen at
> <mailto:jeroen at>> wrote:
>     If you expect that they have outages that they cannot quickly see or
>     not, then you should also expect a blacklist like to be broken or not
>     properly update. Hence, better to see the problems and to alert the
>     folks so that they can fix these issues properly (though Google is now
>     just hacking around with MSS clamping...).
> [de-cloak]
> Google has been doing MSS clamping for a long time, I've seen this
> myself in packet captures and Lorenzo also confirmed in his email:
> "...some Google servers temporarily stopped doing MSS clamping."
> They do it for a good reason: to prevent PMTUD as it introduces delay
> and their customers (eyeballs) wouldn't like it. Lorenzo and others
> explained this too several times.

That "explanation" was seen, at least for me, the first time in this thread.

As stated, the MSS clamping is just hiding the real problems. It does
not properly resolve anything.

> The world is not spinning around sixxs and your design ideas. Please
> turn off write-only.

Wow, here come the ad-hominem attacks, stay in lurk mode if you can't
handle people raising issues. If I had not commented about this problem,
it would never have come to light... maybe in several years when nothing
could have been done anymore. But today, we still can fix things.

Please realize that the world does have a lot more users than SixXS.

Noting problems and properly fixing them are important.


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