Global Availibity

[Joseph K Gainey]

[this was posted through the comp.protocols.dns.bind newsgroup as well]


Okay, I've read all the bantering about how DNS was never intended
to load balance etc. so please don't scream at me when I ask this
question.

I've got sites that are geographically diverse, they are located in
different parts of the country.  Assuming that my different ISP's at each 
location have network connections that are 100% available at both location 
then I would only need to have a standard bind domain setup with master/slaves.

Now the problem in in the real world the network connection provied by the
various ISP's are not 100% available and when they are not available and
we use the master/slave setups then some percentage of the time clients
attempting accessing out site won't be able to.  For example:


      Client------------[Client DNS]
                        |               
      +-----------------+                       [Office]
      |                                         DNS(MASTER) 
      |                                           |
      |
      +---------------------+---------------------+
  (t1)|                 (t1)|                 (t1)|
      SITEA(Seattle)    SITEB(New York) SITEC(Houston)
      DNS1(SLAVE)       DNS2(SLAVE)     DNS3(SLAVE)
      WWW(1)            WWW(2)          WWW(3)




Now if the the client requests the address of WWW it will get back the
list of IP addresses in some non-guaranteed order correct?  Each time the
client requests that WWW be resolved it will get a different ip address.

Now the scenario: my ISP in Houston has a total internet connectivity 
failure leaving zero access to ANY machine at that location for 24hrs.  What 
happens correct me if i'm wrong, is that 1/3 (33%) of the connections to WWW 
will fail.

We have entered into our contracts with clients that we will have 99.99% uptime
,
if 1/3 (33%) of connection made in a 24hr period fail then this is not 99.99%
uptime.  The problem i've run into is that the only way for client's (and thier
DNS servers) to not see the down site is to remove the down site from dns.  Not
a problem right, except I'ld rather not be called at 2am to remove something
from dns i'ld rather have dns do it itself.

Any constructive ideas?

Joe