[THIN] Re: Web Interface Query - NetBT Errors

I guess that depends on your situation.

If you are running internal clients on internal DNS (under your control) then 
the refresh time is less significant since you can manually refresh downstream 
DNS servers.  If you are running with external DNS servers on the public 
internet then you need to be more planful and careful. A botched DNS setting 
pushed to the outside world can be very difficult to correct after you release 
it.

The key pieces of the DNS Zone SOA record are:

        refresh = how ofen downstream DNS servers come back to the primary to 
update the zone
        retry   = how often downstream DNS server will retry a failed zone 
transfer
        expire  = how long a downstream DNS server can hold a zone without 
contact to the primary DNS server
        default TTL = the TTL for the records within the zone (unless otherwise 
specified on the host records)

We typically lower the refresh to 5 minutes on our internal servers when we 
have a planned outage, then put it back to 24 hours when we are done.  On the 
internal servers though, we can cycle the DNS services to push an urgent change 
if we have an unplanned outage.  On the outside DNS you have to find a 
equilibrium (fast enough refresh that you can react to an outage vs. long 
enough TTL that clients do overrun their DNS servers or have unnecessary DNS 
overhead)

Eric

Eric M. Foote
Detroit Medical Center
Intel Server Group Leader
Security Group Leader
OP 5-1625
3663 Woodward Ave.
Detroit, MI 48201-2403
(313) 578-2310
<mailto:EFoote@xxxxxxx>
Fax (313) 578-2265




-----Original Message-----
From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx]On
Behalf Of Toby
Sent: Friday, July 29, 2005 9:26 AM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: Web Interface Query - NetBT Errors


Thanks for the information Eric. Do you know of an alternative method
I can use to resolve the issue should it arise?

Toby

On 7/29/05, Foote, Eric <EFoote@xxxxxxx> wrote:
> Just a side note here:
> 
> Be sure that you understand the implications of making this change on a 
> permanent basis.
> The TTL's purpose in life is to reduce the overhead of DNS queries from the 
> client's transaction perspective, reduce the load on the DNS servers and 
> provide the ability for the client to sustain functionality during a DNS 
> outage.
> 
> The refresh time for the domain is also significant if you have a 
> multi-tiered DNS structure (internal or external).  If you change the TTL on 
> an "A" record at the domain primary but the downstream DNS servers are only 
> updating once/day because domain refresh is set to 86400, the downstream 
> clients will not see the change until the downstream DNS server refreshes 
> from the primary.
> 
> DNS is one of those services that you really need to spend some time on 
> understanding, the implications of a misconfigured domain can be disasterous. 
>  Microsoft has done a great job of making DNS "invisible" and "simple" and 
> many admins don't take the time to really understand how it works.
> 
> Eric
> 
> Eric M. Foote
> Detroit Medical Center
> Intel Server Group Leader
> Security Group Leader
> OP 5-1625
> 3663 Woodward Ave.
> Detroit, MI 48201-2403
> (313) 578-2310
> <mailto:EFoote@xxxxxxx>
> Fax (313) 578-2265
> 
> 
> -----Original Message-----
> From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx]On
> Behalf Of Toby
> Sent: Friday, July 29, 2005 5:09 AM
> To: thin@xxxxxxxxxxxxx
> Subject: [THIN] Re: Web Interface Query - NetBT Errors
> 
> 
> So when they say you learn something new everyday, they were right.
> 
> Thankyou very much.
> 
> Toby
> 
> On 7/28/05, Jeff Pitsch <jepitsch@xxxxxxxxx> wrote:
> > Open DNS admin console, click on view, then Advanced.  Then go to the
> > actual entry of the record and open it.  You'll now see the Time to
> > Live parameters.  You may want to set this one lower than the default.
> >  This is the setting of how long the record will reside in teh client
> > side cache.  For instance, if your web server goes down and a user had
> > already accessed the web server, it could potentially take up to an
> > hour before the record leaves the cache and the user could pull the
> > correct IP.
> >
> > Jeff Pitsch
> >
> > On 7/28/05, Toby <toby.percival@xxxxxxxxx> wrote:
> > > Forgive me, DNS is not my thing. How do I change the TTL (is that time
> > > to live?) in DNS.
> > >
> > > On 7/28/05, Jeff Pitsch <jepitsch@xxxxxxxxx> wrote:
> > > > No requirement, but it may be desired.
> > > >
> > > > Yes, you could easily change the DNS.  I would change the TTL of the
> > > > entry though just in case.
> > > >
> > > > Jeff Pitsch
> > > >
> > > > On 7/28/05, Toby <toby.percival@xxxxxxxxx> wrote:
> > > > > Thanks for the reply Jeff.
> > > > >
> > > > > So no requirement for load balancing then. Ok, that is great.
> > > > >
> > > > > I have created an alias in DNS, 'citrix', which points to the WI 
> > > > > server.
> > > > > In a disaster recovery exercise, all I have to do is point this alias
> > > > > to my backup WI server.
> > > > >
> > > > > Is that configuration along the right lines?
> > > > >
> > > > > Thanks
> > > > >
> > > > >
> > > > >
> > > > > On 7/28/05, Jeff Pitsch <jepitsch@xxxxxxxxx> wrote:
> > > > > > Keep in mind that WI only does app enumeration and handoff.  After a
> > > > > > session is started, WI has nothing to do wiht it.  So the actual 
> > > > > > load
> > > > > > of 400 users is very small.  Also,if your that concerned about it, I
> > > > > > would recommend moving the WI serves off the Metaframe servers.  One
> > > > > > WI server can easily handle 400 users.
> > > > > >
> > > > > > Jeff Pitsch
> > > > > >
> > > > > > On 7/28/05, Toby <toby.percival@xxxxxxxxx> wrote:
> > > > > > > Hi List,
> > > > > > >
> > > > > > > I have a Web Interface query.
> > > > > > >
> > > > > > > I have 15 Citrix servers (PS4.0 on W2K3), and three of these are 
> > > > > > > WI
> > > > > > > servers. Instead of having one server service 400 connections, 
> > > > > > > how do
> > > > > > > you go about load balancing the 3 WI servers.
> > > > > > >
> > > > > > > What around DNS round robin?
> > > > > > > Or maybe a third party app out there?
> > > > > > >
> > > > > > > Any ideas would be very gratefully received.
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