Remove/add [A] records based upon server availability

[Chris Buxton]

On Dec 27, 2009, at 7:16 AM, Rick Dicaire wrote:
> On Sun, Dec 27, 2009 at 3:16 AM, Ryan S <ryan332211 at hotmail.com> wrote:
>> Some web browers and applications will fail in a round-robin A record
>> configuration such that if the first A record returned is unavailable, then
>> the browser will not bring up the page.
> 
> So fix the application instead of bending the protocol to suit a
> broken applications need?
> Specifically, what web browsers and applications are you referring to?
> On what OS's?

All web browsers, pretty much. Round robin does not provide failover except for protocols and applications that specifically make it work, such as the DNS and SMTP protocols (only between servers, in each case).

Using DDNS to remove unresponsive or overloaded web servers from the rrset works OK in situations where solutions at the HTTP and routing layers are not appropriate, such as web servers in different physical locations; there are appliance vendors out there offering such solutions. This is also similar to one part of the Akamai solution for global traffic management.

However, this strategy should be avoided when possible, and buffered with highly available solutions at each point to minimize the use.

Chris Buxton
Professional Services
Men & Mice