Am 27.01.2016 um 00:36 schrieb Darcy Kevin (FCA):
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?
violating what? complain at the vendor of your DNS cache or the device doing "DNS ALG" in front of you!
;; ANSWER SECTION:livetileedge.dsx.mp.microsoft.com. 3581 IN CNAME livetileedge.dsx.mp.microsoft.com.akadns.net. livetileedge.dsx.mp.microsoft.com.akadns.net. 281 IN CNAME livetileedge.dsx.mp.microsoft.com.edgekey.net. livetileedge.dsx.mp.microsoft.com.edgekey.net. 281 IN CNAME e1898.b.akamaiedge.net.
e1898.b.akamaiedge.net. 1 IN A 104.87.22.10 ;; ANSWER SECTION:livetileedge.dsx.mp.microsoft.com. 3580 IN CNAME livetileedge.dsx.mp.microsoft.com.akadns.net. livetileedge.dsx.mp.microsoft.com.akadns.net. 280 IN CNAME livetileedge.dsx.mp.microsoft.com.edgekey.net. livetileedge.dsx.mp.microsoft.com.edgekey.net. 280 IN CNAME e1898.b.akamaiedge.net.
e1898.b.akamaiedge.net. 0 IN A 104.87.22.10 ;; ANSWER SECTION:livetileedge.dsx.mp.microsoft.com. 3579 IN CNAME livetileedge.dsx.mp.microsoft.com.akadns.net. livetileedge.dsx.mp.microsoft.com.akadns.net. 279 IN CNAME livetileedge.dsx.mp.microsoft.com.edgekey.net. livetileedge.dsx.mp.microsoft.com.edgekey.net. 279 IN CNAME e1898.b.akamaiedge.net.
e1898.b.akamaiedge.net. 17 IN A 104.87.22.10
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