The Mathematical Reality of IP Addressin in IPv4...

Forrest W. Christian forrestc at
Thu Aug 26 16:05:28 UTC 1999

> Through if someone translate this joke to the normal labguage, I'll 
> appreciate too -:). Good paper - for the evening hours...

I DID look at it pretty deeply.

As far as I can tell the concept is basically this:

Today, we determine the network part of the address via ANDing the netmask
with the address.   Thus, if we have (for simplicity sake) a classful B
address we have something like: Address  OR

 10010000 00000001 00001000 00000011 in binary netmask OR

 11111111 11111111 00000000 00000000 in binary

You derive the network number by anding the two above, such as:

 10010000 00000001 00000000 00000000

Or, in other words everyhting starting with 144.1 as the first two octets
is on the same network.

What this proposal appears to be proposing is to permit NON-CONTIGUOUS
netmasks such as:

Or, in binary:

 1111111111 10000000 01111111 00000000

Thus, the network number would actually consist of all 8 bits of octet
one, the first bit of octet two, the last 7 bits of octet 3 and none of
octed four.

Initially this seems like a good idea in that by allocating in this
fashion you can reuse bits over and over - that is, my host bits can be
your network bits and vice versa.

Assuming that netmask info was available end to end for both source and
destination addresses this would be a really cool idea.

However, the problem is that since the netmask is not available for
"destination" addresses at the source end, There is no way to determine
which bits mean what for proper routing.  In addition, even if you did
provide that information at the source end, it would have to be passed on
with each packet through all the routers so they could uniquely identify
which of the multiple potential endpoints for a given destination address
that the packet is going to.

In all reality, I think that the IP address problem is solving itself.
The majority of the customers I deal with have a SINGLE ip address for all
of their internal machines.  I have actually allocated LESS space than I
have reclaimed over the past year and a half from customers who have moved
to Private Address space.   To facilitate this I sell them a $250 "iGate
Junior" which is basically a 486 with some software I've put together in
house (shameless plug).   The iGate Jr. basically takes all of the inside
requests and NAT's them into a single outside address.  It also takes
inbound connections for Mail and other services and routes them to the
appropriate inside box.   As a result, a typical small-to-medium sized
company only needs ONE real ip address in most circumstances. 

- Forrest W. Christian (forrestc at KD7EHZ
iMach, Ltd., P.O. Box 5749, Helena, MT 59604
Solutions for your high-tech problems.                  (406)-442-6648

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