On Mon, 4 Dec 2006, John Kelly wrote:
The DNS lookup has little cost when you manage the clients' DNS, and you make sure they all have good DNS. But for users connecting from the world, there will be delays.
The number of cases in which reverse DNS is unavailable (or untimely) has decreased significantly in the past decade. The spam problem has actually helped, by making IP addresses without reverse DNS be second class citizens.
That isn't to say that the world is all good. Some Linux distributions have glibc with a broken implementation of getaddrinfo() (the IPv6 capable version of gethostbyname()) which do a reverse DNS lookup to return the canonical name rather than stopping at the end of a FQDN/CNAME chase. This is a terrible bug, it affects any software built with IPv6 support, it breaks virtual hosts, and it violates the specification of getaddrinfo().
I think that the current Linux distributions are fixed, but lots of sites (including our main timesharing site at UW) have older distributions with the bug.
I need speed, rather than hostnames in the logs. And Kerberos is not a concern (for me).
The problem is, what is "not a concern" today may become a concern in the future. Also, the "not a concern" side effects of a decision are not always noted (or passed on to one's successor).
I've experienced numerous support request of this nature, when the successor tried to do something, it doesn't work, insists that he never did such-and-such. The result is considerable frustration; sometimes the individual gets *quite* irate, and only after some time is it discovered that a third party (whether his predecessor, or a distribution) *did* make a change because the side effect was "not a concern".
So, at the very least, please document that you made that change in your installation, along with a note about the known side effects.
Your successor will thank you. So will I. -- Mark -- http://staff.washington.edu/mrc Science does not emerge from voting, party politics, or public debate. Si vis pacem, para bellum. _______________________________________________ Imap-uw mailing list Imap-uw@u.washington.edu https://mailman1.u.washington.edu/mailman/listinfo/imap-uw
