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IPv6 Connectivity Saga (part n+1)

  • From: Thomas KÃhne
  • Date: Sat Feb 02 05:55:27 2008 
I took a DMOZ[1] dump, extracted all unique domain-name port combinations
and checked their IPv6 connectivity.

3 388 012 : 100.000% : total
3 260 296 :  96.230% : IPv4 only
  122 560 :   3.620% : bad NS
    3 372 :   0.100% : IPv6 working
    1 694 :   0.050% : broken or "fake" IPv6 

broken: TCP connect failed
fake: IPv6 mapped IPv4 addresses (e.g. ::ffff:1.2.3.4)

33.4% of all services that advertised IPv6 failed to deliver or in
other words the IPv6 failure rate is ten times the NS failure rate.

Seems high, thus a cross check via TLDs' NS:

270 : 100.0% : TLD total (excluding the IDN tests)
268 :  99.3% : IPv4 working
  2 :   0.7% : IPv4 broken (HM and KP)
177 :  65.6% : IPv6 working
  8 :   3.0% : IPv6 broken

1910 : 100.0% : NS total
1500 :  78.5% : IPv4 only
  31 :   1.6% : IPv4 broken
 356 :  19.1% : IPv6 working
  23 :   1.2% : IPv6 broken

IPv6 failure rates of 4.3% (TLD) and 6.1% (NS) is lower than the above
33.4% but are still significantly higher than the IPv4 failure rates of
0.7% (TLD) and 1.6% (NS). TLD root-NSs usually are managed by dedicated
infrastructure organisations thus better trouble shooting than the DMOZ
listed ones get is expected and suggests the above 33.4% failure rate
isn't some kind of sampling artifact.

About 4 days later I did a more detailed check of the hosts with
broken IPv6:

1624 : hosts total
 827 : connection timed out
 382 : no route to host
 249 : connection refused
  95 : network unreachable
  54 : SixXS never received a route announcement for that block
  43 : broadcast address
  30 : * IPv4 in IPv6
  22 : IPv6 assignments reclaimed (3ffe::/16)
  16 : * no IPv6 (::)
  12 : * IPv4 only
  10 : * IPv6 working
   4 : IPv6 never assigned
   4 : local (fe80::/10)
   2 : local (::1)
   2 : broken NS

Issues(cases not marked with a star) do tend to arise
but why are fundamental issues like "connection timed out",
"no route to host" and "connection refused" so frequent?

(testing was done from 2a01:4d0:102::31)

Thomas

[1] http://www.dmoz.org/help/getdata.html