On Sun, Apr 12, 1998 at 08:54:20AM -0400, Tom Diehl wrote:
> On Sun, 12 Apr 1998, Erik Corry wrote:
>
> > The short answer is "it just works". The long answer:
>
> Maybe but it also works without it. That is what I do not understand.
> I have been using diald with a dynamic IP for at least 3 years and this is
> the first time I have gotten involved in this. But since you brought it
> up I am courious. Your explaination makes sence but one would think
> that you would need this all of the time. Are there only some
> programs that need this? What do I not understand here?
A lot of this you probably know. Sorry, but I don't know which bits,
so I'll explain it all ;)
You need to do a dns lookup for each connection attempt, ie when you
do:
mybox$ telnet bbs.isca.uiowa.edu
the first thing that happens is that telnet has to translate
bbs.isca.uiowa.edu to 127.12.16.3 (except it's not 127.12.16.3,
I made that bit up).
If you don't have a cacheing only nameserver on your own box,
then what will happen is:
a) the resolver sends a UDP packet to a server in /etc/resolv.conf
b) diald brings the link up
c) the packet goes out (with an incorrect source address)
d) the DNS server tells a different machine the answer
e) your resolver times out the request, and thinks to itself that
the server it asked first of all is dead, and asks someone else,
but this time with the correct source address
f) telnet goes ``aha! I know who to connect to now!''
g) everything works.
If you have already have a cacheing named on your box, then the
above is obviously bogus.
--
"Oh, I've seen copies [of Linux Journal] around the terminal room at
The Labs."
-- Dennis Ritchie
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