[79023] in North American Network Operators' Group
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and
daemon@ATHENA.MIT.EDU (John Dupuy)
Mon Mar 28 16:59:20 2005
Date: Mon, 28 Mar 2005 15:58:51 -0600
To: Nanog Mailing list <nanog@merit.edu>
From: John Dupuy <jdupuy-list@socket.net>
In-Reply-To: <Pine.LNX.4.44.0503281612480.30675-100000@server2.tcw.telec
omplete.net>
Errors-To: owner-nanog@merit.edu
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<font size=3>I'll be brief, but I do want to perhaps word Alex's
definition in a different way that might be more useful.<br><br>
Even "tier 1" providers regularly trade transit. They must
since no single network is connected to all the other ones. Not even
close. Even UUNet (ASN 701), arguably the most-connected network on the
planet, only connects to a fraction of the possible peerings.<br><br>
The true definition is more vague: if a peering or transit circuit
between A or B is taken down, who will be hurt the most: A or B? If it
predominantly B, and much less A, then A is "more Tier 1" and B
is of a "lesser Tier". If they are equally hurt, they the are
of equal status. Essentially, "Tier 1" is whatever the other
"Tier 1" providers believe at the moment is "Tier 1".
It is self-referential and not distinct at all.<br><br>
This is, frustratingly, a very non-technical definition. But it seems to
map with what I've actually seen the industry do.<br><br>
John<br><br>
At 09:17 AM 3/28/2005, Stephen J. Wilcox wrote:<br><br>
<blockquote type=cite class=cite cite>On Mon, 28 Mar 2005, Randy Bush
wrote:<br><br>
> > Firstly, peering isn't binary. Is peering vs transit a
distinction based on<br>
> > routes taken / accepted & readvertised, or on cost? Does
"paid for peering"<br>
> > count as peering or transit? If you pay by volume? If you pay
for "more than<br>
> > your fair share" of the interconnect pipes? (if the
latter, I am guessing<br>
> > there are actually no Tier 1s as everyone reckons they pay for
more than<br>
> > their fair share...).<br>
> <br>
> pay? did i say pay? i discussed announcement and receipt
of prefixes. this<br>
> was not an accident. it is measurable.<br><br>
i also avoided money.. i dont think its that relevant, everyone is paying
for <br>
peering or transit in one form or another, i dont think any peering is
free <br>
(free != settlement free)<br><br>
> > Secondly, it doesn't cover scenarios that have have happened in
the past.<br>
> > For instance, the route swap. EG Imagine networks X1, X2, X3,
X4 are "Tier<br>
> > 1" as Randy describes them. Network Y peers with all the
above except X1.<br>
> > Network Z peers with all the above except X2. Y & Z peer.
To avoid Y or Z<br>
> > needing to take transit, Y sends Z X2's routes (and sends Z's
routes to X2<br>
> > routes marked "no export" to X2's peers), and Z sends
Y X1's routes (and<br>
> > sends Y's routes to X1 marked "no export" to X1's
peers). Perhaps they do<br>
> > this for free. Perhaps they charge eachother for it and settle
up at the end<br>
> > of each month. Perhaps it's one company that's just bought
another.<br><br>
"transit (n). The act of passing over, across, or through;
passage."<br><br>
whether it is a settlement arrangement or a mutual swap, they do NOT
have<br>
peering, they ARE transitting and by our definition are not transit-free
(and <br>
hence not tier1)<br><br>
however alex, you do highlight an excellent point - things are not as
simple as<br>
'tier1, tier2', there are complicated routing and financial arrangements
in<br>
operation, which brings me back to my earlier point: does it matter what
a<br>
network is paying for some connectivity providing they deliver to you the
<br>
connectivity you need at the quality you desire?<br><br>
Steve</font></blockquote></body>
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