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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Good day,</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>We just yesterday deployed the 3.1.1 recursor in one of our
regions, and have noted a handful of domains with problems when the “auth-can-lower-ttl”
attribute is set on the server. I noted that some users here reported
some problems with 3.1.1 on their servers – this could be the reason</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>The problem is that, with this option, the recursor can end
up with different NS data for the same name with varying TTL values. This
happens if the “lower” servers do not include some NS records that
are present on the “registrar” servers, and with lower TTL values.
When this happens, the lower TTL records will expire, leaving only the records
with the higher TTLs. If that server(s) is/are also not reachable- then the
domain will be unresolvable until that NS record expires. When it does, this
cycle will start again. I believe that different data for the same name
is never supposed to have differing TTL values anyway…</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>At the time of this message, “ocis.net” and “ipcc.ca”
are examples of this situation.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>We took a look at how some other caching software handles
this situation – nearly all of them have an implicit “auth-can-lower-ttl”,
but, they all also just completely replace the NS records with those on the “lower”
servers, thus still leaving a set of NS records on the cache that all have the
same (lower) TTL.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>We’d really prefer to not to disable “auth-can-lower-ttl”
on these new pdns servers as we know this will draw different complaints from
users who are migrating their domains.</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Is there any other recourse here?</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Thanks!</span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'> </span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>============================<br>
Darren Gamble<br>
Planner, Regional Services<br>
Shaw Cablesystems GP<br>
630 - </span></font><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>3rd Avenue SW</span></font><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'><br>
</span></font><font size=2 face=Arial><span style='font-size:10.0pt;font-family:
Arial'>Calgary</span></font><font size=2 face=Arial><span style='font-size:
10.0pt;font-family:Arial'>, </span></font><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'>Alberta</span></font><font size=2
face=Arial><span style='font-size:10.0pt;font-family:Arial'>, </span></font><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>Canada</span></font><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'><br>
T2P 4L4<br>
(403) 781-4948</span></font></p>
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12.0pt'> </span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
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