Re: schein.debian.org
Jeffrey B. Green a écrit :
> Pascal Hambourg writes:
>>
>> The MTU 1480 suggests that there is some 6in4 tunnel encapsulation on
>> the path and one node does not do its job properly. It could be either :
>>
>> - the remote tunnel endpoint has IPv6 MTU set to 1480 but does not send
>> ICMPv6 "packet too big" when dropping too big a packet ;
>> - the server or a node before it drops ICMPv6 "packet too big" ;
>> - the remote tunnel endpoint has IPv6 MTU set to 1500 but does not
>> fragment properly 6in4 datagrams ;
>> - some node on the path drops 6in4 fragments ;
>> - the local tunnel endpoint does not reassemble properly 6in4 fragments
>>
>> or many more causes.
>
> It may be a local problem
If downloads work from other IPv6 servers, then the problem is likely at
this specific server, schein.debian.org.
I did a little test : on my router I added a specific route to an IPv6
host in my LAN (so this route it is preferred over the general prefix
route) specifying an MTU of 1300, so the router replies to bigger
packets with an ICMPv6 "packet too big" advertising the proper MTU.
Then from the host, when I send a ping with a size of 1350 to some other
server (say www.debian.org), the server sends the first reply in one big
packet, my router drops it and sends an ICMPv6 "packet too big" and the
server sends each subsequent reply as two fragments. Just as expected.
But when I send a ping of the same same size to schein.debian.org, it
keeps sending replies as one single packet so it seems to ignore the
ICMPv6 "packet too big".
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