I don't understand them, either. However, if you define incoming traffic as "bad", it encourages depeering by the receiving side if the incoming/outgoing ratio exceeds a certain value, especially among close-to-tier-1 carriers: the traffic does not automatically disappear just because you depeer. Now suppose that the sending side doesn't want to play games and buys transit from one of your other peers. Given the tier-1 status, there is some chance that this has a measurable impact on the traffic ratio with that other peer. Essentially, this is a self-fulfilling prophecy, and it works equally well if you define outgoing traffic as "bad".
I was trying to stay out of this. But I think I'm going to chime in here. I think (originally)... means... whenever the NAP structure was created and the NSFnet was decommissioned, long haul moving of the bits was very expensive. Perhaps more so than the local-distance piece because you had comparatively few of these links and had to cart bits a very long way to dump them off. Now I believe that with the influx of large, reasonable colos and 20+ high speed interconnects in a region (or slightly larger area). This coupled with dramatically reduced long haul costs has shifted the value/expense ratios in peering. For example if you are a content network. If you needed to peer in 5 places in the old (long-haul=expensive) model would colo your content in 5 places near your interconnected and the only interconnections between your colos would be whatever you needed to keep heartbeat and data sync between them. But you incurred a large cost for this colo and manpower and other things. Now... let's just say you don't need to do that... because you can run a few circuits around the country (or MPLS them) and its pretty "cheap". However, the last-mile piece for access networks HASN'T moved as much in the same time period. Lots of networks (Q, LVLT, GBLX, etc) built long haul networks. Lots of them colo'd in ILEC switch (and tandem buildings). But this doesn't do ISP type businesses very much good. You still have to pay interconnect fees to the ILEC or exorbitant colo fees to them to backhaul the circuit to your DC with all of your equipment. Means... that even though you control the customer and the CPE, you are paying fees to many folks that _really_ own the copper (or coax) or underlying infrastructure and they have little to NO competitive pressure to be more than slightly price concerned. This drives you to the idea that actually moving higher PPS is "bad" while increasing peak speeds is "good". Customers are buying/being marketed to by peak speed. So you give them large pipes because once you've paid the underlying tariffs to get to their house/business (say a dry pair) whatever speed you signal on it is your equipment cost, nothing else. But actually encouraging them to USE that bandwidth is expensive because your cost of growing the T3, OC3, OC12 or whatever you are backhauling from the various COs to your network is BAD and expensive. This is the model as I understand it today. Formerly the longhaul and cost of transit was so expensive these costs were more negligible. Now we have a playing field. Now if you depeer a guy [Cogent] for example, and you force him to buy transit from someone who doesn't have a very vibrant transit business [NTT/Verio, I'm being kind] you increase his costs and force [NTT/Verio] to upgrade their network which may take time. The depeered guy suffers. Maybe he doesn't suffer much at all [Like when Cogent could force all of its AOL traffic through its Level3 connection]. But his customers... They want speedy access to your eyeballs. Maybe some of them will want to reduce the number of networks traversed to get to your eyeballs. By limiting the number of SFI connections you have... I would theorize you can force those who can afford it to interconnect with you directly. Not everyone. But a few. If you perceive your network as "better" than your SFI peers, then naturally you would assume that the business of their customers would eventually flow to you. The problem with this kind of increased instability is that the perception and tenacity of all the players is very difficult to assess and is often not as vastly different as the players would hope. But to the extent you can force others to have to redo their network interconnections with little impact [at least what you believe when you are taking the action] the better it is for you. Especially if you are running out of value-added sales pitches. Further proving the counterpoint: Large eyeball networks (like Verizon broadband) that use Level3 (formerly genuity) a lot, didn't get affected by this depeering. Why? Because they've already added diversity to their network. Even if the Level3 routes are normally chosen more often than the other providers [guessing, not saying its true], Level3 forced their 95th percentile to peak with their other providers for a month while simultaneously showing them a lack of "of my god my performance sucks" calls from their customers with the new routes. I think this has been proven out to be universally bad for Level3. Cogent probably mostly bad. But I think I wanted to raise the point [above] that while content guys have enjoyed cost improvements over the last years the access guys have not seen as much improvement and the areas of their businesses (loops, co colo vs server pricing, server colo) have become a much larger, more unwieldy part of their businesses. [guessing] Comments? Deepak