priority with A record?

[Kevin Darcy]

On 4/5/2011 8:23 AM, iharrathi.ext at orange-ftgroup.com wrote:
> Hi,
> can i make priority on a A or NS record? Since with round robin if i 
> put  the same record record 2 or 3 time, Bind ignore the duplicates 
> Records, means
>  this:
>
> wikipediaNSns2.wikimedia.org.
>
> wikipediaNSns0.wikimedia.org.
>
> is the same like this:
>
> wikipediaNSns2.wikimedia.org.
>
> wikipediaNSns0.wikimedia.org.
>
> wikipediaNSns0.wikimedia.org.
>
> In this 2 case it will send 50% of traffic to ns2 and 50% to ns0;
>
> Is there anyway to enable priority on A or NS record?
>
> Thanks.
>
>
For NS records, there is no way to do this in BIND, and it's completely 
unnecessary anyway, since every major DNS full-resolver implementation 
will keep track of how fast nameservers respond -- based on round-trip 
times, known as "RTT"s -- and prefer faster-responding nameservers over 
slower-responding ones. So the load spreads itself automatically, and 
failures -- which are assessed as really "bad" performance -- are routed 
around.

For A/AAAA records, there are mechanisms to control the order in which 
the records are presented. See "sortlist" and "rrset-order" (not sure 
that "rrset-order" even exists in later versions of BIND, since I've 
never used it in production). However, these are only practical on 
tightly-controlled intranets, where all of the BIND-instance 
configurations can be kept in sync with each other, otherwise one BIND 
instance may undo the careful address-record ordering that another 
performs. rrset-order and sortlist are pretty much useless for Internet 
names, since the vast majority Internet users get their DNS through 
intermediate resolvers, which will usually randomize or round-robin the 
responses whenever they are answering from their caches.

As another poster pointed out, SRV records provide the capability for 
the domain owner to implement per-name failover and "weighting" of 
targets, in the DNS data itself. But, thusfar the DNS community hasn't 
had much success getting client-software developers (e.g. browser 
developers) to adopt SRV record support. Meanwhile, certain 
network-hardware companies (including among others a certain huge router 
vendor) rake in big money with their sledgehammer "load-balancer device" 
approach to the problem. There are software approaches to network 
load-balancing as well, but I have no direct experience with those.

                                                                         
                                                                         
                                                                         
                 - Kevin

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.isc.org/pipermail/bind-users/attachments/20110405/abe4dd37/attachment.html>