[atlas] A Case Study of AAAA Filtering

On Thu, Oct 11, 2012 at 8:56 PM, Lorenzo Colitti <lorenzo at google.com> wrote:

> When you did the AAAA measurements, did you distinguish between the probe
> not getting a response (e.g., if the dig command timed out) and the probe
> getting a NODATA response?
>

Ok, after having done my own analysis, it looks like the answer to that was
no. Strictly speaking, AAAA filtering is when the recursive resolver
returns NOERROR with zero records even if there was an AAAA record.
However, this but this rare in the raw data here.

Many of the cases that the post reports as filtering seem to be problematic
home routers returning "not implemented", timing out, or returning SERVFAIL
when asked for AAAA records. While this is still a problem for IPv6
(especially in the case of timeouts) it's not really AAAA filtering. The
"not implemented" seems to be mostly to blame for the failures in the
French AS at the top of the list:

Results (produced by the attached Python script):

A queries (udmlog_1004102_2012_39.txt):
Results: {'successful': 167183, 'norecurse': 382, 'ERR_timeout': 5722,
'refused': 1163, 'ERR_senderror': 416, 'server-failure': 362}

AAAA queries (udmlog_1004103_2012_39.txt):
Results: {'filtering': 420, 'successful': 165667, 'norecurse': 383,
'ERR_timeout': 6057, 'refused': 1156, 'not-implemented': 774,
'ERR_senderror': 415, 'server-failure': 317}
Filtering DNS servers:
  124.102.51.104: 96/98 (98.0%)
  79.131.194.22: 95/95 (100.0%)
  124.212.215.50: 97/97 (100.0%)
  88.188.129.85: 2/95 (2.1%)
  133.38.4.79: 96/96 (100.0%)
  2.85.23.226: 32/55 (58.2%)
   81.56.47.149: 2/96 (2.1%)
Filtered probes:
  2299: 96/98 (98.0%)
  2848: 2/96 (2.1%)
  3028: 95/95 (100.0%)
  2896: 96/96 (100.0%)
  2891: 97/97 (100.0%)
  2197: 2/95 (2.1%)
  268: 32/55 (58.2%)
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