Michel Renfer schrieb:

Let the fight begin... :-)

Yes. Reading nanog now since 20 minutes, I found a really good explanation by Richard A Steenbergen, what acutally is going on between Cogent and L3 (quote below).

BTW Cogent offers now free transit for 1 year to every L3 customer who cannot reach Cogent anymore ... http://status.cogentco.com/

Also I wrote a little comment about this sandbox battle 3 weeks ago (German): http://www.blogg.ch/index.php?/archives/72-Politik-und-Peering.html

F.

Richard A Steenbergen schrieb:

Internet connectivity is only as good as the people who are willing to buy it. If you wanted to connect to the Internet, you would pay someone money to deliver the packets to/from you to the complete Internet, yes? They do this by either connecting with every other network out there, or by in turn paying someone else to deliver the data that you paid them to deliver. This is called transit.

Now, sometimes when two networks of roughly equal size and value to each other have customer bases that need to talk to each other, they will set up circuits between the two and not charge each other for the traffic passed over it, for the SOLE purposes of exchanging traffic with each others' customer base. This is called peering.

If you carry this trend all the way out to the maximum extent possible, you end up with a network that is so big that it doesn't have to pay anyone else to "deliver the bits for it", it interconnects with EVERYONE else that it would send bits to via peering, and everything else is a customer. This is called a "tier 1", of which there are only a handful (not counting marketing-land, where everyone claims to be a tier 1).

So, what you have here is a battle of wills between two very large networks. One is a legitimate "tier 1" (and one of the biggest IP networks in the world), the other is "really really close", only a couple of networks away from being a tier 1. The network who is "really really close" is still buying transit to reach a few destinations, but they want to be a tier 1. This means that the transit they are buying is not "full transit" in the way that you would normally think of it, instead they are buying "selected routes" to the few remaining networks they don't peer with. This is a kind of "tier 1 by technicality", not having "earned" it through true "settlement free peering" the way that a true tier 1 has, but by intentionally paying your transit provider to "emulate" peering with the remaining networks who they don't peer with directly.

Now, when said "big" peer comes along and says "we don't want to swap traffic for free with you any more", the smaller network doesn't want to let them go. Besides the obvious fact that they don't want to have to start paying money for traffic that was previously free, they don't want to look "weak" by caving in and buying transit, incase other networks who previously peered with them decide that they can depeer and force said network to pay THEM money for transit too. So, the smaller network intentionally chooses to remain unreachable and not buy transit, under the hopes that the customers of the larger network will complain enough that they are forced to "repeer".

So, the bottom line is that the two networks "could" be reachable to each other if they wanted to, but they are intentionally choosing not to do so. Level 3 "could" repeer Cogent (which Cogent wants but Level 3 doesn't), and Cogent "could" buy transit (which Level 3 wants but Cogent doesn't), but it is currently a matter of waiting to see which side will blink first under the pain of pissed off customers who can't reach the full Internet. Whichever one blinks first loses. Cogent has successfully used this tactic in the past (Teleglobe), and unsuccessfully tried it as well (OpenTransit).

But that said, the Internet is working the way that it is intended. I believe folks have reported that Level 3 saw a loss of around 1200 prefixes from Cogent, and Cogent saw a loss of around 4300 prefixes from Level 3. Out of a customer base of 11k and 57k respectively, this is relatively small (11% of Cogent's customer base and 7.5% of Level 3's customer base), since only single homed customers are affected. Unfortunately you can't make two networks who don't want to directly connect with each other or pay someone else to connect to the other network talk to each other if they don't want to. Usually these things iron themselves out within a few days, but these are certainly two of the largest and most pigheaded networks to go up against each other, so it could be interesting. Whining about it as a customer is one way to try and convince one side or the other to cave sooner, but you can pretty much be guaranteed that someone will end it before some judicial, regulatory, or law making body steps and makes them. :)