BIND9.2.0a2 Source Code

[Kevin Darcy]

Vaishali Paithankar wrote:

> Firstly, I am sorry for the repetative mails sent by me. This happened
> because my earlier mail to the list was bounced back. And I was trying
> to send it again.
>
> On Wed, 18 Jul 2001, Kevin Darcy wrote:
>
> >
> > This isn't just a BIND source code issue. You'd have to extend the protocol
> > so that the server would send this additional information in a form that the
> > clients would understand. And then you'd have to convince all of the server
> > and client implementors to adopt the protocol extension.
> >
> > Overall, you might be better off using a totally different protocol instead
> > of piggybacking on DNS. A Server Performance Metric Protocol or something
> > like that...
> >
> > About the best you can do _without_ protocol changes is to convince client
> > implementors to use SRV records, which send "preference" and
> > "weight" information to the clients so that they can make more intelligent
> > decisions about what server to use, and how to do failover. But SRV isn't
> > truly dynamic.
>
> To make it dynamic...
>
> How often a DNS loads its zones ?
>
> i.e. if we updated our SRV records frequently, DNS will also have to load
> its zones with the same frequency ?
>
> Or can't we load only SRV records or the information that has changed
> e.g. only the metrics in the SRV record ?

With Dynamic Update, these questions become basically meaningless. The master
server gets the changes immediately. Now, how quickly the changes get out to all
of the slaves and to all of the caching servers in the world, is another question.
Most DNS-based load-balancer solutions "solve" this problem by using very small
TTL (time-to-live) values on their records. But that's an awful approach. It
wastes tons of nameserver resources and causes lookup latency. As Brad pointed
out, L4 load-balancing is a more technologically elegant approach, because from
the DNS perspective, the data stays constant. This fits DNS'es caching model
better.


- Kevin

> If you want something dynamic, then you have to go to some
> > sort of load-balancing solution. If you look in the archives of this list for
> > the last few days, you'll see that we've been arguing about whether these
> > load-balancing solutions violate the DNS protocol and/or whether they are a
> > good idea or not.
> >
> >
> > - Kevin
> >
> > Vaishali Paithankar wrote:
> >
> > > Hello,
> > >
> > > I have read about the concepts of DNS but am a new BIND user and
> > > just installed BIND9.2.0a2 on one of my Red Hat Linux 7 machines.
> > >
> > > I wish to try to incorporate some changes in BIND so that it returns
> > > metrics of Server (metrics like Server Load, RTT) with the I.P. Address of
> > > the Server.
> > >
> > > This is for the purpose of selection of "best" server by the Client.
> > >
> > > Which source code files should I go through / change to implement this ?
> > >
> > > Where can I find some help, documentation of structure of the source
> > > code of BIND ?
> > >
> > > Vaishali
> > > --
> >
> >
> >
> >
>
> --