[ih] The history of "This" 0.0.0.0/8 network?

[Grant Taylor]

On 2/11/19 1:21 PM, Dave Taht wrote:
> As part of an upcoming internet draft, I'd wanted to be able to coherently 
> discuss the origin and original use cases of the "this" network "0" 
> in Arpanet to early ipv4 transition days, and thus far I haven't found 
> much information on it.

I have a few comments.  Feel free to ignore them.  Please correct me if 
you can.  I'd love to learn from someone else's work.

  - To me, "0.0.0.0" represents and as such implies IPv4.  So "early 
IPv4 transition days" sounds like the transition /to/ IPv4.  Yet 0.0.0.0 
is an IPv4 address to me.  So what are we transitioning from and to?

Admittedly I'm not familiar with the addressing that was used on ARPAnet 
prior to IPv4.  But I suspect that it's addressing did not take the form 
of 0.0.0.0.

Aside:  Perhaps it's time to go back and re-read Where Wizards Stay Up 
Late again, but this time from the eyes of an amateur network engineer 
instead of a history student.

  - I guess there is some difference in the single IP address of 0.0.0.0 
and any of the 16,777,215 other IPv4 address in the 0/8 network.

  - It's my understanding that zero is frequently used when the proper 
value is unknown.

  - As such, the zero network (0/8) is used when the proper network 
address is unknown.

  - Similarly, the zero host address is used when the proper host 
address is unknown.

  - Thus combining the zero network and zero host, you get 0.0.0.0 as 
the IPv4 address.

  - I think it's important to distinguish sending /from/ and sending 
/to/ the 0.0.0.0 address or network.  (That being said, I don't recall 
anything that sends /to/ the 0.0.0.0 address.)

  - It's important to distinguish things, like ARP, that use the 0.0.0.0 
address as part of their payload, which has nothing to do with the L2 
broadcast addressing.  (I.e. ARP using broadcast Ethernet frames.)

  - To me (and others that I talk to) the zeroth address has a high 
collision (at least in reused concepts) with subnetting.

  - How does the first and last address within a subnet become special?

  - How does the first and last subnetwork within a network become special?

  - I would be very interested in learning more about how 0.0.0.0, or 
the zeroth IP was apparently also used as a broadcast address.

But after recent discussions with friends and colleagues, I realized 
that I can't satisfactorily explain (at least to myself) what the 
network (or zeroth) address is.  I think I had always taken it for 
granted that the network and broadcast were to be not used by client 
devices as they had special meaning to the network.

I can satisfactorily (at least to myself) explain what the broadcast 
(last) address is and what it's used for.  But the network (or zeroth) 
address is more difficult.

I know that (older?) BSD network stacks could overload the network and 
broadcast IPs.  Why was using separate network and broadcast address 
preferred over the older BSD method of using a single address for both.

Sorry if this has turned into a ramble.  There have been a lot of 
scattered thoughts that have sort of collided together over the last few 
months and aggregate around the zeroth / first IP in a subnet, and they 
all seem related in some way that I can't satisfactorily explain.

> I'm curious if there is a reference on it somewhere?

I too would like to find and read the origination (or references there 
to).  Please share what you find, or let us know where we will be able 
to find your work when you're finished.



-- 
Grant. . . .
unix || die