the Internet Backbone

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1

Last time this term came up, I opined that there was no "backbone" any more
and that 1996's Internet had a "hairball topology." Vadim, among others,
disagreed with me but we didn't pursue the topic. Perhaps we should have.

Well, "backbone" is too vague. I rather prefer to think of Internet
topology as of "tiers". The nodes in upper-levels cast "cones of
influence" in lower tiers. Nodes from lower tiers belonging to
different cones of influence do not generally speak to each other,
and so have to purchase transit from higher tiers.

Note that this loose definition provides different idea of "backbone"
aka the first tier, quite unlike the "defaultless core". To illustrate
it let's assume there are two regional dual-homed ISPs, A and B,
connected to, say ANS and MCI:

ANS- --MCI

  X |

A--- ---B

Both A and B generally have to be defaultless. But they are not
in the first tier, but rather in second tier, as they have to purchase
transit from first-tier providers to talk to each other.

May be we should classify ISPs by miles*bandwidth of their internode
circuits?

And in that sense, there is no backbone in 1996.

Tier one is the "backbone". Those are providers not purchasing
transit from anybody else.

Terminologically speaking, there's no discrete set of wires or routers or
companies you can point to and say, "there, that right there, that is the
Internet Backbone."

Well, you can do that in practice, and be pretty certain.

We tend to reserve the term "NSP" for folks who peer at enough NAPs that they
have no default route and aren't buying transit from anybody.

Ok, so here we agree :slight_smile:

We tend to use
the term "ISP" when we mean someone in the packet or even the session business
who _does_ have to buy transit from somebody. Once in a while I hear the term
"backbone provider" used synonomously with "NSP" (as defined above).

That's pretty common usage. Sounds much better than an-as-pee.
The term for second-tier is "regional provider" and third tier is
usually local providers.

I am not even going to get started (here and now, at least) on the subject of
peering politics/economics. I just thought I'd chime in on the definitions of
the words we're all using.

--vadim

2

Well, "backbone" is too vague. I rather prefer to think of Internet
topology as of "tiers". The nodes in upper-levels cast "cones of
influence" in lower tiers. Nodes from lower tiers belonging to
different cones of influence do not generally speak to each other,
and so have to purchase transit from higher tiers.

Tier one is the "backbone". Those are providers not purchasing
transit from anybody else.

If we think like an onion (shades of TinyBASIC!) then the core of the
Internet are these providers who supply transit over their own national
and international backbones and who do not need to buy transit from other
providers. The providers who form the Internet core are sometimes called
NSP's (Network Service Providers) and sometimes called Tier 1 providers

That's pretty common usage. Sounds much better than an-as-pee.
The term for second-tier is "regional provider" and third tier is
usually local providers.

The next layer of the onion is the Tier 2 providers sometimes referred to
as regional providers although they may actually serve overlapping
geographical regions. These providers do not provide transit but they do
supply other providers in a lower tier.

This brings us to the Tier 3 providers commonly known as ISP's (Internet
Service Providers. These organizations may connect to Tier 2 providers
or Tier 1 providers but their distinguishing characteristic is that they
do no normally supply organizations who resell Internet access.

Tier 4 networks belong to those organizations who provide Internet access
for their own members or employees. These could be corporations, schools,
or universities who operate both internal networks and provide dialup
services that are not available to the general public. Sometimes a Tier 4
network provides access to other organizations such as a company which
supplies its subcontractors with their Internet connectivity.

Tier 5 is the end user. They may have a single PC that dials up to the
Internet or they may be sitting in front of a workstation on a corporate LAN.

Unlike an onion skin, these layers are not precise and there is some overlap
especially in Tier 2. Until recently most ISP's connected directly to
Tier 1 providers and although there are some providers who are starting
to specialize in Tier 2 services it will remain common for both Tier 1
and 3 organizations to be in that market.

This seems to explain the relationships in a way that I think the average
person or journalist could understand and still form concepts fairly
close to the reality of today's global Internet.

Michael Dillon Voice: +1-604-546-8022
Memra Software Inc. Fax: +1-604-546-3049
http://www.memra.com E-mail: michael@memra.com