Hi again,
On 29 Sep 2015, at 21:23, Jiankang Yao wrote:
What reason do you have to think that response latency from root
servers
has any measurable impact on end-user experience?
I think that there are some papers which explain it.
Then some citations would be useful.
To be clear, I'm not having trouble understanding the concept. I just
don't believe it.
One observation:
due to the complexity of the network environment, the current quality
of access to root service is uneven globally. For example, CNNIC
finds through comprehensive monitoring and analysis that in China the
time delay of access to the 13 root servers varies greatly from
province to province, showing a difference of up to 200ms for most
root servers, and in a number of provinces nearly 60% queries fail to
hit the root mirrors deployed in China.
I believe that, for sure. And I understand the desire to bring the root
server infrastructure closer to end-users in China, motivated by
concerns about availability and the problems that would result from
prolonged non-availability.
However, I think it's controversial to imply that end-user performance
is substantially improved by the wider (and closer) deployment of root
zone data. That assertion needs some justification.
For example, a recursive resolver whose clients mainly ask for names
that end in (say) COM only need to talk to root servers every 172,800
seconds (that's the TTL on the NS set in the root zone and at the COM
apex). Even if it takes a really long time to get a response from a root
server when I need one (e.g. ten seconds, which seems like a high
estimate), 10/172800 is less than 0.1%, and even in that case it's
likely that records for popular COM names are independently cached and
in fact there would be zero impact on end-users that depend on those
common names even during such an event.
BTW,
this draft is trying to solve the same problem speicified in
draft-ietf-dnsop-root-loopback.
I think that the authors of draft-ietf-dnsop-root-loopback will have
a better explaination than me.
I had much the same feedback to the authors of that draft. In that case,
however, it was observed that slaving the root zone was common (if
perhaps not widespread) practice, and it was worth documenting the
trade-offs and recommending a consistent approach for those who insisted
on doing it. That's not the case here.
I think I would need to see a convincing problem statement and
understand how this proposal provided effective solutions before I could
support it.
Joe
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