[nsd-users] NSD SRV rr return limit

W.C.A. Wijngaards wouter at nlnetlabs.nl
Wed May 16 07:31:14 UTC 2012


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Hi Will,

On 05/16/2012 01:08 AM, Will Pressly wrote:
> Nah. I am querying directly against the authority.

There is no limit imposed (apart from packet size and the 16-bit
counter for the number of RRs and so on).  So, practically, 30 or so
to keep easily within UDP message sizes (you would need to test to see
the compression benefits and resulting message size), and with TCP
failover up to 64Kib of data (thousands of SRVs).

Best regards,
   Wouter

> On Tue, May 15, 2012 at 3:44 PM, Bryan Duff <bduff at ecessa.com 
> <mailto:bduff at ecessa.com>> wrote:
> 
> __ On 05/15/12 17:18, Will Pressly wrote:
>> Hi All,
>> 
>> Is there a limit to the number of SRV records that NSD will 
>> return, outside of the upper bound on packet size? I have a name 
>> that has ~18 SRV records, and I only see the same four, always. 
>> The packet size out on the wire is 260B, so I would expect we 
>> could cram some more in there, and I am not sure why we are only 
>> ever seeing the same five.
>> 
>> I wanted to ask before burning time on a source-code code-dive.
>> I am using nsd 3.2.5.
>> 
>> Thanks, Will Pressly
>> 
>> 
>> _______________________________________________ nsd-users mailing
>> list nsd-users at NLnetLabs.nl <mailto:nsd-users at NLnetLabs.nl> 
>> http://open.nlnetlabs.nl/mailman/listinfo/nsd-users
> Remember NSD doesn't rotate records in the same set (or in any 
> case).  Also, you aren't going through a caching server are you?
> 
> $ dig @192.168.2.231 <http://192.168.2.231> 
> _autodiscover._tcp.example.org <http://tcp.example.org> srv ... ;;
> QUESTION SECTION: ;_autodiscover._tcp.example.org
> <http://tcp.example.org>. IN      SRV
> 
> ;; ANSWER SECTION: _autodiscover._tcp.example.org
> <http://tcp.example.org>. 30 IN SRV     1 100 25 mail.example.org
> <http://mail.example.org>. _autodiscover._tcp.example.org
> <http://tcp.example.org>. 30 IN SRV     2 100 25 mail.example.org
> <http://mail.example.org>. _autodiscover._tcp.example.org
> <http://tcp.example.org>. 30 IN SRV     3 100 25 mail.example.org
> <http://mail.example.org>. _autodiscover._tcp.example.org
> <http://tcp.example.org>. 30 IN SRV     4 100 25 mail.example.org
> <http://mail.example.org>. _autodiscover._tcp.example.org
> <http://tcp.example.org>. 30 IN SRV     5 100 25 mail.example.org
> <http://mail.example.org>.
> 
> ;; AUTHORITY SECTION: example.org <http://example.org>.
> 360     IN      NS ns1.example.org <http://ns1.example.org>. //end
> snip
> 
> That was just me quickly creating some entries on a test zone. 
> Often caching servers limit the number of RR's to whatever they
> feel like (4 seems common).  That's just my experience.
> 
> -Bryan
> 
> 
> 
> 
> _______________________________________________ nsd-users mailing
> list nsd-users at NLnetLabs.nl 
> http://open.nlnetlabs.nl/mailman/listinfo/nsd-users

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