Resolving numerical adresses

[Jon Knight]

On Thu, 28 Nov 1996 web4lib at library.berkeley.edu wrote:
> But can anyone tell me where the log pics up the machinename/IP-number?

The IP address can be retrieved from the OS once a socket connection is
made (the IP packets have to carry both a source and destination IP
address otherwise the server wouldn't know where to send any responses).

> Is it from the browser?

Yes, its the browser, or the last proxy that the request went through
before it reached your server.
 
> The statistics program (Analog) lists IP-numbers
> under the heading ]Unresolved numerical adresses], does this mean that
> they have failed a resolving process?

To get from the IP address to the Fully Qualified Domain Name (FQDN) one
calls a name resolution function (the name of which varies depending on
the OS that you're using). This function can try a number of techniques
to look up the host name including looking in a local file, doing a
NIS (Yellow Pages) lookup and querying the DNS.  The last of those will be
the most common.  Your "Unresolved numerical adresses" are simply IP
addresses that either don't have an associated FQDN in the DNS or whose
DNS servers are unreachable for some reason.  Not having an FQDN for an IP
address is not uncommon and is perfectly valid; FQDNs are just to improve
user friendliness and you can run perfectly OK without one as long as
you've got a valid IP address.

Tatty bye,

Jim'll

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Jon "Jim'll" Knight, Researcher, Sysop and General Dogsbody, Dept. Computer
Studies, Loughborough University of Technology, Leics., ENGLAND.  LE11 3TU.
* I've found I now dream in Perl.  More worryingly, I enjoy those dreams. *