DNS Failover

[Maria Iano]

Pete,

It is still the case that our GSLBs work pretty well. I'm not just saying that from the point of view of using my own browser. When we use the GSLBs to redirect traffic for our sites, we can see that the traffic does indeed get redirected. 

For example, one of our sites gets over a million hits per day from all over the world. It gets over one million monthly unique visitors. When the IP address handed out for that site by the GSLBs is changed, the change takes effect in the traffic to the site extremely quickly and effectively. So that gives a good kind of average over the various different browsers and resolvers throughout the world.

I agree with you that the solution does not work 100% effectively, as there are indeed clients and name servers out there that don't use TTLs correctly. But what I'm saying is, that overall and mostly it does work, and I don't know of a better solution (we are not an ISP and cannot play around with routing at all). We do use local server load balancers within each geographical location, but they can't provide geographical failover.

Maria 

On Thu, Oct 14, at 09:08%P so wrote Pete Tenereillo (pt_bind at hotmail.com):

> Maria,
> 
> A new DNS resolution is required if a single A record is returned. The only 
> version of IE that does a new DNS resolution without being restarted is 
> WinXP SP2. Microsoft was notified that GSLBs do not work correctly for 
> failover with single A records, some of the vendors worked with them, and 
> they changed the behavior in the release that came out a few weeks ago. 
> WinXP SP1 and previous versions of IE, and NetScape (i.e. the vast majority 
> of Internet clients) have the issue. I don't know about Firefox etc. 
> Browsers aside, many proxy servers will defeat what you are trying to do 
> with failover and your GSLBs.
> 
> 
> Pete.
> 
> 
> ----- Original Message ----- 
> From: "Maria Iano" <maria at iano.org>
> To: <comp-protocols-dns-bind at isc.org>
> Sent: Thursday, October 14, 2004 7:53 AM
> Subject: Re: DNS Failover
> 
> 
> > We use GSLBs for load balancing between web sites but mostly for failover 
> > in case a primary site goes down. Usually they work pretty well. It's true 
> > that some name servers don't handle TTLs properly, but from my experience 
> > at watching the traffic I can tell you that it works for the vast 
> > majority.
> >
> > Personally I haven't found it to be the case, as stated in the article you 
> > mention, that I have to restart my browser for the new A record to take 
> > effect. It has been my experience that the browser catches on and goes to 
> > the new IP pretty much immediately. The browsers I use most frequently are 
> > Firefox, Safari and IE. They are recent versions. Maybe the problems you 
> > describe occurred with older versions?...
> >
> > Maria
> >
> >>
> >> -----Original Message-----
> >> From: bind-users-bounce at isc.org [mailto:bind-users-bounce at isc.org] On
> >> Behalf Of Pete Tenereillo
> >> Sent: Thursday, October 14, 2004 9:00 AM
> >> To: Greg Maccarone; Anthony Wilkins
> >> Cc: comp-protocols-dns-bind at isc.org
> >> Subject: Re: DNS Failover
> >>
> >> Anthony mentioned he has a Web app, so that TTL trick won't work
> >> reliably.
> >> The low TTL would be seen by servers "throughout the rest of the world"
> >> but
> >> TTL are ignored by most clients (and many proxy servers), so all
> >> existing
> >> users (and users that share such proxies) will be stuck on the downed
> >> server. Check out:
> >>
> >> http://www.tenereillo.com/GSLBPageOfShame.htm
> >>
> >> for details. IMO for failover you are better off putting both servers at
> >> the
> >> same site, using local load balancing (there are some very cost
> >> effective
> >> solutions available now) and redundant power and Internet connections.
> >>
> >>
> >> Pete.
> >>
> >>
> >> ----- Original Message ----- 
> >> From: "Greg Maccarone" <gmaccarone at gmail.com>
> >> To: "Anthony Wilkins" <anthony_wlkns at yahoo.com>
> >> Cc: <comp-protocols-dns-bind at isc.org>
> >> Sent: Tuesday, October 12, 2004 11:46 AM
> >> Subject: Re: DNS Failover
> >>
> >>
> >> > On Tue, 12 Oct 2004 11:01:45 +0200, Anthony Wilkins
> >> > <anthony_wlkns at yahoo.com> wrote:
> >> >> Hi, is there anybody who can help me in finding a solution to a
> >> problem
> >> >> I have?
> >> >>
> >> >> My web server is sometime temporarily down and I want people to go to
> >> my
> >> >> remote site where I have a backup web server. Can I change DNS on the
> >> >> Internet fast enough for incoming requests to be handled by my
> >> redundant
> >> >> web server? Normally I don't want traffic to go to the remote site.
> >> >>
> >> >> Thanks, Anthony W.
> >> >>
> >> >>
> >> >
> >> > A way this could be achieved with DNS is to have a low TTL on the host
> >> > entry that could be changing because of the outage.  Then in most
> >> > cases it would take no longer than the specified TTL for the changes
> >> > to be seen throughout the rest of the world.
> >> >
> >> > my $.02.
> >> >
> >> > -- 
> >> > Greg Maccarone
> >> > gmaccarone at gmail.com
> >> >
> >> >
> >>
> >
> >