While I think 9k for exchange points is an excellent target, I'll reiterate that there's a *lot* of SONET interfaces out there that won't be going away any time soon, so practically speaking, you won't really get more than 4400 end-to-end, even if you set your hosts to 9k as well.
Agreed. But in the meantime, removing the 1500 bottlenecks at the ethernet peering ports would at least provide the potential for the connection to scale up to the 4400 available by the SONET links. Right now, nothing is possible above 1500 for most flows that traverse an ethernet peering point. My point is that 1500 is a relic. Put another way, how come PoS at 4400 in the path doesn't break anything currently between endpoints while any suggestion that ethernet be made larger than 1500 in the path causes all this reaction? We already HAVE MTUs larger than 1500 in the "middle" part of the path. This really doesn't change much of anything from that perspective. For example, simply taking Ethernet to 3000 would still be smaller than SONET and even that would provide measurable benefit. There is a certain "but that is the way it has always been done" inertia that I believe needs to be overcome. Increasing the path MTU has the potential to greatly improve performance at practically no cost to anyone involved. We are throttling performance of the Internet for no sound technical reason, in my opinion. Now I could see where someone selling "jumbo" paths at a premium might be reluctant to see the Internet generally go that path as it would decrease their "value add", but that is a different story.