questions about interfaces

[Bill Hacker]

David Cuthbert wrote:

Erik Wikström wrote:

 It's
easier to just pretend that it's a normal NIC just like any other 
(though the driver does not require any special hardware).


Heh... imagine if the loopback interface actually required hardware.
Imagine?  'Remember when' you mean...

It exists because there was a time when hardware *was* required, and one did not 
always have arms long enough...

Likewise the 'echo' service and 'ping'.

"Yeah, I have sl0 going out to the net; sl1 has the Tx and Rx lines tied 
together and is bound to 127.0.0.1."
One also had to tie the RTS-CTS (serial) or other busy/done (parallel) lines 
together, sometimes even add pull-up resistors or latches.

Other standards and protocols were even more fussy, (E1, DS1, X.75, FR, ATM, 
SDH, SONET, etc.) but remote-loopback was soon built-in to the terminating gear 
as standard.

Can't test the underlying network without it.

I think I just trashed the last of those pre-wired DB-25 and Centronics plug-ins 
the same week I sent the S-100 gear off to someone who would try to preserve it...

Bill