[atlas] Problems with DNS measurements and NSID

On 2014/05/20 18:36 , john wrote:
> On 20/05/14 18:23, Daniel Quinn wrote:
>> Maybe there's some confusion here, but this multiple response business 
>> is all related to the introduction of `resultset` in firmware 4610:
>>
>>   https://atlas.ripe.net/docs/data_struct/#v4610_dns
>> 
> OK, I guess it might be to support retrying the query on a failure but I
> would be keen to get confirmation from Philip.

The 'normal' mode for DNS queries is that they get sent to one server.
So you would get one reply each time the measurement is performed.

The exception is when the measurement is to query the probe's local DNS
resolvers. In that case, up to three resolvers are queried and you can
get as many replies.

In the past, each replies would be an independent Atlas result. However,
our storage back-end cannot really handle that. So the code was changed
that all three replies are grouped into a single Atlas result.

Hence, in general, an Atlas DNS result can contain multiple DNS replies.
But only if you select the 'use the probe's local resolvers' option.

Philip