Well, when I queried the name livetileedge.dsx.mp.microsoft.com, I got a CNAME
chain where all of the links in the chain had TTLs of 300 seconds or less:
livetileedge.dsx.mp.microsoft.com. 43 IN CNAME
livetileedge.dsx.mp.microsoft.com.akadns.net.
livetileedge.dsx.mp.microsoft.com.akadns.net. 300 IN CNAME
livetileedge.dsx.mp.microsoft.com.edgekey.net.
livetileedge.dsx.mp.microsoft.com.edgekey.net. 46 IN CNAME
e1898.b.akamaiedge.net.
e1898.b.akamaiedge.net. 20 IN A 23.201.56.85
Now, the Authority Section had NS records for b.akamaiedge.net, but that
doesn't help mitigate future queries for {whatever}.microsoft.com,
{whatever}.akadns.net or {whatever}.edgekey.net, so repeated queries of the
same name will need to go back up to the roots again, whenever the TTLs expire
(assuming nothing else queried names *directly* in those domains, or
intermediate domains, through the same recursive resolver and thus populated
relevant NS records).
Yet another reason why chained CNAMEs are bad. But, it's hard to argue with a
successful company whose whole business model is based on chaining CNAMEs. Who
ever knew that violating Internet standards and/or best practices could be so
profitable?
- Kevin
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of HONTVÁRI Levente
Sent: Tuesday, January 26, 2016 9:07 AM
To: [email protected]
Subject: frequent queries to root servers
Hi All,
I assumed that the root servers are only queried a few times a week
(corresponding to the number of top level domains). The logs show a different
picture, Queries to the root servers are quite frequent. What am I missing?
I have attached a dnstop screen (local network traffic was filtered out), after
running for about 2 hours. I also attached a log extract about a single query
from 10.0.3.44 resolved by 10.0.3.48, which involves a query to the root
servers. I notice that there is a DS record query before the root server query,
but otherwise I do not see anything strange.
I have an almost stock Bind 9.9.5 resolver configuration on an Ubuntu server.
L.
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