[bind10-dev] Nameserver Address Store and RFC 2308 - Comments Requested

[Michal 'vorner' Vaner]

Hello

Sending once more to the list, I forgot to add it to CC.

On Tue, Nov 23, 2010 at 09:43:22AM -0800, Jerry Scharf wrote:
> One question is what is the initial state of an NSAS entry before the 
> first query is made? Since this will not be updated in the case of a 
> dropped query, this state will remain, possibly forever. While you can't 
> remove it from the active list, you can lower the likelihood that it is 
> selected and still be within the spec. So adding 10ms to the rtt for 
> each drop would be acceptable. If all the mane servers implement the 
> same policy, all the times will be increased and the selection will not 
> be changed.

The plan is that when a nameserver entry in the hash table is born, it will be
reachable with some random but low RTT (so it is selected and we see what its
real RRT is.

However, it is not true we do not want to update it in case of dropped query. If
the query there times out, we definitely need to mark that, either by setting it
unreachable (really aggressive approach) or by increasing its RTT (it didn't
answer in the time given by timeout, so it was really slow on this query).

What about keeping both RTT and probability it will respond? If we keep that, we
might know it is fast, but drops queries sometime or on the other hand might be
slow but reliable. Server, that is down, would have low probability (computed
somehow, if it did not answer, it would lower, if did, it would get higher). So
we wouldn't cache dead server, just wouldn't want to use it too often.

The problem is when all the servers of a zone are dead, in that case we couldn't
tell right away it is unreachable, and would have to wait for few timeouts.

What do you think?

Have a nice day

-- 
Never underestimate the bandwidth of a station wagon full of HDDs.

Michal 'vorner' Vaner
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