Policy Statement on Address Space Allocations
Tim Bass (@NANOG-LIST)
nanog at dune.silkroad.com
Mon Jan 29 01:00:46 UTC 1996
Dick says (with a smile):
> I'm just a country network jockey and don't understand all this stuff,
Here is a very simple explanation for you to "take to the bank";
and I'll avoid discussing any particular provider and look at the
generic question only.
First, pull up your favorite browser and look at this simple diagram
from an excellent 1977 paper by Kleinrock and Kamoun :
Now, consider this model a very simplified model of the Internet.
Notice that for purposes of discussion, K&K used a 3-level
clustered 24-node network; but the theory scales upward.
In fact, image that YOU are a provider at the 3rd level of the
network and that the network is expanding rapidly and your routing tables
are about to overflow. What must you do to remain at your place in
One obvious way is to create more clusters of route aggregation and form
another level in the hierarchy and the 3-level clustered model becomes
a 4-level cluster. Without getting into the details, even us Tulane
'bare-foot country networkers :-) " can see that the optimal goal of a provider
at each layer is to accept routing information from networks that
are only 1 level less than their position in the hierarchy. Of course,
there are numerous other variations to the them, but the end results
are basically the same.
To illustrate this, please take a final browse at another figure from Kleinrock
and Kamoun :
This diagram is just K&K figure 1 illustrated in a tree.
As a side note, please understand that hierarchical routing is not a new
concept. In fact the original concept of classful A, B, and C IP address
space was basically the same model, where individual clusters in the
network were originally either a /8 or a /16 or a /24; and the network
was somewhat simpler and more closely resembled a symmetric model.
Back to Fig. 2; please note that with the implementation of classless
address space, the model becomes much more complex and a drawing of
the Internet is much more complex; but what remains the same is the
fact that as the network grows, you can easily understand (and think
for yourself) why certain providers have particular business policies
for connecting to their network or why "things are the way they are",
in a simple matter of speaking.
Furthermore, providers that the highest levels of the hierarchy have
a very difficult task considering that they did not have the privilege
to manage the address space in the during the early days of the Internet.
In fact, as many people know, many remain incredulous to the fact that
the original funding agency may have mismanaged the commercialization of the
original IP network (but I'll omit the details).
Understandably, it was difficult to take the fragmented IP address space
model and create an environment that would allow an easy transition
from a non-commercial use policy to uncontrollable commercial growth.
But, on the other hand, taking a "hands off, anything goes,
turn the keys over to commercial providers" approach...... I think
historians will find that the study of this transition and the subsequent
business climate and problems very interesting (as the concept of hierarchical
routing becomes second nature to the layman).
I would like to acknowledge the members of the CIRD-WG within the IETF for
pointing me into the direction of the archives of Computer Networks
and in particular the papers of K&K, with special thanks to Noel Chiappa
for the pointer and UCLA for a copy of the original Kleinrock paper.
In addition, in respect to one of the authors, Professor Kleinrock, I
would like to say thank you for such outstanding work in the field.
I look forward to your 1996 publications of _Queuing Systems_ by
John Wiley and Sons.
Also, thank you for your patience with my use of the southern vernacular.
 Kleinrock, L. and Kamoun, F., "Hierarchical Routing for Large
Networks", Computer Networks, Vol 1, No. 3, 1977, p. 155-174.
| Tim Bass | |
| Principal Network Systems Engineer | "... images are the literature |
| The Silk Road Group, Ltd. | of the layman." |
| | |
| http://www.silkroad.com/ | Umberto Eco |
| | |
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