On Wed, Feb 29, 2012 at 4:02 PM, Joe Greco <jgreco@ns.sol.net> wrote:
In the specific case of TTL, the problem is made much worse due to the way most client code has hidden this data from developers, so that many developers don't even have any idea that such a thing exists.
I'm not sure how to see that a design failure of the TTL mechanism.
Hi Joe, You shouldn't see that as a design failure of the TTL mechanism. It isn't. It's a failure of the system of which DNS TTL is a component. The TTL component itself was reasonably designed. The failure is likened to installing a well designed sprinkler system (the DNS with a TTL) and then shutting off the water valve (gethostbyname/getaddrinfo).
I don't see developers ignoring DNS and hardcoding IP addresses into code as a failure of the DNS system.
It isn't. It's a failure of the sockets API design which calls on every application developer to (a) translate the name to a set of addresses with a mechanism that discards the TTL knowledge and (b) implement his own glue between name to address mapping and connect by address. It would be like telling an app developer: here's the ARP function and the SEND function. When you Send to an IP address, make sure you attach the right destination MAC. Of course the app developer gets it wrong most of the time. Regards, Bill Herrin -- William D. Herrin ................ herrin@dirtside.com bill@herrin.us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004