Getting practical for a minute. What is the optimal way now to see if a given host truly exists?
You first have to define what you mean by 'exists'. I have a machine here that I call 'stinky'. It's not on the Interent though. Does the 'host' 'stinky' exist?
Assume that I can't control the DNS server--I need to have this code run in any (*ix) environment. Assume also that I don't want to run around specialcasing specific IP addresses or TLDs--this needs to work reliably no matter what the domain. User gives me a string, and I need to see if the given host is a real machine.
How would you do this before? Does an A record for a hostname mean that a host with that name exists? If so, then all *.com 'hosts' now 'exist'. If not, what did you mean by exist before?
An answer from Verisign would be most appropriate here, since they have done "extensive research" on the impact of their new service, so presumably they figured out the answer to this problem and have code samples available for distribution. However I get the feeling from their press releases that they've forgotten there is more to the internet than just the web.
Forgive me for defending Verisign, but if you want to know if a given DNS name corresponds with an A record, you can still determine that. If you want to determine something else, you can still do that, depending upon what that something else is. As for 'fsck.de', a good argument can be made that this is not really a legal domain. It's a host. Checking for an SOA is a good way to tell if a domain is valid, depending upon what you mean by 'domain' and 'valid'. I'm reminded of the classic programmers question, "how do you tell if a machine is online?". The answer is "define what you mean by a machine being online and test for that". So you aren't asking a comprehensible question yet. DS