[ITNOG] Problemi di PMTUD IPv6 con www.nic.it

[Daniele Orlandi]

Sto sperimentando dei problemi di PMTUD blackholing con www.nic.it, ho aperto 
diversi ticket, dopo diverso tempo mi ha risposto una persona che mi pare 
molto poco interessata a risolvere il problema.

Mi chiedo se sono solo io a sperimentarlo o anche voi avete problemi:

vihai@stfu:~$ wget www.nic.it
--2010-10-05 10:45:24--  http://www.nic.it/
Resolving www.nic.it... 2a00:d40:1:1::239, 192.12.192.239
Connecting to www.nic.it|2a00:d40:1:1::239|:80... connected.
HTTP request sent, awaiting response... Read error (Connection timed out) in 
headers.


vihai@stfu:~$ tracepath6 www.nic.it
 1?: [LOCALHOST]                      pmtu 1500
 1:  f-0-45.gw-noc.uli.it                       0.759ms 
 1:  f-0-45.gw-noc.uli.it                       0.639ms 
 2:  f2-0.gw-mix.uli.it                         0.899ms 
 3:  seeweb2-v6.mix-it.net                      0.854ms 
 4:  gi4-16.scotty.mil.seeweb.it                1.046ms 
 5:  registroit-v6.mix-it.net                  30.368ms asymm 12 
 6:  2a00:d40:1:2::6                           38.963ms asymm 13 
 7:  2a00:d40:1:1::239                         38.421ms reached


Pacchetto piccolo passa:

vihai@stfu:~$ ping6 -M dont www.nic.it -s 1000 -c 1
PING www.nic.it(2a00:d40:1:1::239) 1000 data bytes
1008 bytes from 2a00:d40:1:1::239: icmp_seq=1 ttl=52 time=38.1 ms

--- www.nic.it ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 38.197/38.197/38.197/0.000 ms

Pacchetto grosso (ovviamente) non passa:

vihai@stfu:~$ ping6 -M dont www.nic.it -s 2000 -c 1
PING www.nic.it(2a00:d40:1:1::239) 2000 data bytes

--- www.nic.it ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

Pacchetto di 1480 bytes passa:

vihai@stfu:~$ ping6 -M dont www.nic.it -s 1432 -c 1
PING www.nic.it(2a00:d40:1:1::239) 1432 data bytes
1440 bytes from 2a00:d40:1:1::239: icmp_seq=1 ttl=52 time=38.5 ms

--- www.nic.it ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 38.549/38.549/38.549/0.000 ms

Pacchetto di 1481 bytes non passa:

vihai@stfu:~$ ping6 -M dont www.nic.it -s 1433 -c 1
PING www.nic.it(2a00:d40:1:1::239) 1433 data bytes

--- www.nic.it ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

Sembra che ci sia una strozzatura a 1480 bytes che non viene riportata via 
ICMP.



Un altro percorso affetto dal problema:

1  2001:1418:10:5::1 (2001:1418:10:5::1)  1.311 ms  1.247 ms  0.385 ms
2  if-5-2.Muttley-Monster.core.TRN.ipv6.itgate.net (2001:1418:1:101::fa)  
1.773 ms  0.439 ms  1.394 ms
3  garr-ipv6-pub.topix.it (2001:7f8:23:ffff::4)  1.79 ms  1.809 ms  1.978 ms
4  rt-to1-rt-pi1.pi1.garr.net (2001:760:ffff:ffff::ee)  6.452 ms  6.064 ms  
4.989 ms
5  rt-pi1-ru-nic-it.pi1.garr.net (2001:760:ffff:120::41)  35.025 ms  35.239 ms  
35.54 ms
6  2a00:d40:1:1::239 (2a00:d40:1:1::239)  36.332 ms  35.695 ms  35.951 ms


-- 
  Daniele "Vihai" Orlandi
  Bieco Illuminista #184213