[dns-wg] DNS Lameness Statistics and Notifications

Anand,

On Tue, 2009-02-24 at 14:02 +0100, Anand Buddhdev wrote:
> We have been monitoring name servers for some time now and statistics
> from the data gathered are published online each month at:
> http://www.ripe.net/info/stats/dns-lameness/

I'm curious about the numbers here, and the meaning of the counts of
servers.

That is, if I have:

  2.0.192.in-addr.arpa NS ns1.example.com
                       NS ns2.example.net
  3.0.192.in-addr.arpa NS ns1.example.com
                       NS ns2.example.net

  ns1.example.com      A  192.0.2.1
  ns2.example.com      A  192.0.3.1

Does this count as 2 servers or 4 servers?

Further, if I have:

  2.0.192.in-addr.arpa NS ns1.example.com
                       NS ns2.example.net
  3.0.192.in-addr.arpa NS ns1.example.com
                       NS ns2.example.net

  ns1.example.com      A  192.0.2.1
                       A  192.0.3.1
  ns2.example.com      A  192.0.2.2
                       A  192.0.3.2

How many servers does this get counted as?


It might also be informative to show the amount of address space that is
affected by bad servers. It could be that the overall 6% of servers that
are lame only affects 1% of the space... or it could affect 50%.


Another useful metric may be to look at the amount of traffic that
arrives to the RIPE NCC parents and gets directed to lame servers. I
think this is should give a reasonable guesstimate of how lameness
affects actual users.

The NCC can look at the answers they send, and since they know both the
NS-sets they are answering with as well as the lameness for each of the
servers in those answers, this information can be used to determine the
likely effect of lameness on users.

So, for example, if a user gets an NS-set where 1 of 4 servers is lame,
we can estimate that they will have a 25% chance of sending a query to a
lame server and have to retry. If a user gets an NS-set where 2 of 4
servers are lame, then they have a 50% chance of sending a query to a
lame server, and a 33% chance of their retry going to a lame server as
well.

Combining a bit of analysis with actual traffic measurement could help
us to understand what the actual impact of lameness on Internet users
is(*).

I suppose the NCC would need to be careful about how it publishes
results, as LIRs or DNS operators might be sensitive about someone
publishing how much DNS traffic they get. I doubt it actually matters,
but people may still get upset.

--
Shane

(*) And perhaps help me in my quest to rid the world of the evil of
    reverse DNS completely. ;)