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Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]

  • From: Stephen J. Wilcox
  • Date: Mon Mar 28 10:19:51 2005

On Mon, 28 Mar 2005, Randy Bush wrote:

> > Firstly, peering isn't binary. Is peering vs transit a distinction based on
> > routes taken / accepted & readvertised, or on cost? Does "paid for peering"
> > count as peering or transit? If you pay by volume? If you pay for "more than
> > your fair share" of the interconnect pipes? (if the latter, I am guessing
> > there are actually no Tier 1s as everyone reckons they pay for more than
> > their fair share...).
> pay?  did i say pay?  i discussed announcement and receipt of prefixes.  this
> was not an accident.  it is measurable.

i also avoided money.. i dont think its that relevant, everyone is paying for 
peering or transit in one form or another, i dont think any peering is free 
(free != settlement free)

> > Secondly, it doesn't cover scenarios that have have happened in the past.
> > For instance, the route swap. EG Imagine networks X1, X2, X3, X4 are "Tier
> > 1" as Randy describes them. Network Y peers with all the above except X1.
> > Network Z peers with all the above except X2. Y & Z peer. To avoid Y or Z
> > needing to take transit, Y sends Z X2's routes (and sends Z's routes to X2
> > routes marked "no export" to X2's peers), and Z sends Y X1's routes (and
> > sends Y's routes to X1 marked "no export" to X1's peers). Perhaps they do
> > this for free. Perhaps they charge eachother for it and settle up at the end
> > of each month. Perhaps it's one company that's just bought another.

"transit (n). The act of passing over, across, or through; passage."

whether it is a settlement arrangement or a mutual swap, they do NOT have
peering, they ARE transitting and by our definition are not transit-free (and 
hence not tier1)

however alex, you do highlight an excellent point - things are not as simple as
'tier1, tier2', there are complicated routing and financial arrangements in
operation, which brings me back to my earlier point: does it matter what a
network is paying for some connectivity providing they deliver to you the 
connectivity you need at the quality you desire?


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