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Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
- From: Stephen J. Wilcox
- Date: Tue Mar 29 15:36:00 2005
On Tue, 29 Mar 2005, John Dupuy wrote:
> I was looking at it from a route announcement point of view. Transit is where
> AS A advertises full routes to AS B. Thus, AS B is getting transit from A.
> Peering is where A & B only advertise their network and, possibly, the
> networks that stub or purchase transit from them.
no, they MUST send their customer nets else their customers will not have
> It is my understanding that the top ISPs "trade transit". They provide full
> routes to each other without payment, regardless of how or where the route
> was learned from. They are willing to pass some traffic without
> compensation because it makes for better connectivity. From an announcement
> POV they are not peering.
ahhh. no, they send peering only between each other (approx 50000 routes for
each of the biggest providers - level3, sprint, uunet, at&t)
> I am still curious: do any of the larger ISPs on this list want to
> confirm/deny the previous paragraph?
> I think we are getting into "defining terms" territory. So, I will bow out
> of the discussion.
> At 01:56 PM 3/29/2005, David Barak wrote:
> >--- John Dupuy <firstname.lastname@example.org> wrote:
> > > But by the technical description of a "transit free
> > > zone", then 701 is not
> > > tier one, since I have encountered scenarios where
> > > many AS are transversed
> > > between 701 and other networks, not just a peer of a
> > > peer. Unless, by
> > > "transit free zone" you mean "transit trading" where
> > > large providers permit
> > > each other to transit for free. (Which gets back to
> > > my 'who hurts more'
> > > discussion.)
> > >
> >Transit = being someone's customer
> >Peering = permitting your customers to go to your
> >peer's customers or the peer's network, but not the
> >peer's peers, without exchange of money.
> >Any other relationship != peering for my purposes
> >(although lots of subtly different relationships
> >exist, the largest networks tend to take a view which
> >is not too dissimilar to the one shown above)
> >Are you implying that 701 is paying someone to carry
> >their prefixes? While I'm not the peering coordinator
> >for 701, I would find that improbable. I would expect
> >that money would flow the other direction (and thus
> >701 would become a more valuable peer for other
> > > I'm willing to be wrong. If any of the large
> > > providers on the list will say
> > > that their network does not transit beyond the
> > > customer of a peer; and they
> > > still maintain full connectivity, I will gladly be
> > > corrected.
> >oodles and oodles of people can say this (and already
> >have). A paying customer of mine can readvertise
> >(with a non-munged AS_PATH) any of my prefixes which
> >they want, and thus provide transit for other people
> >to reach me. That does not change the fact that I'm
> >not paying for transit.
> >So in short, I would say that T1 vs T2 etc is a
> >"follow the money":
> >T1 => doesn't pay anyone else to carry their prefixes,
> >and runs a default-free network.
> >T2 => pays one or more T1 providers to carry their
> >prefixes, may or may not run a default-free network.
> >T3 => leaf node, pays one or more T1/T2 providers to
> >carry their traffic, probably uses default route.
> >YMMV, blah blah blah
> >David Barak
> >Need Geek Rock? Try The Franchise:
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> >Yahoo! Sports - Sign up for Fantasy Baseball.