[nocarrier]

This stuff seems basic at first glance, but it's not easy to get right, and you're discounting a ton of effort that went into getting feedback loops and demand prediction to work properly in Cartographer for example. Maybe it's easy to slap together L4/L7 LB and throw a DNS server in front of it at smaller scales, but it's a notable accomplishment to do this at Facebook's scale. Nothing out there approaches Facebook's request rates.

There have been detailed talks about Proxygen's architecture at various open houses in Seattle and Menlo Park, and they should have HTTP2 support working well soon. I'd expect there's going to be more detailed blog posts on Proxygen at some point. Or you can check out the source code too.

Fragmentation isn't really an issue for either Shiv or Proxygen. I don't think they will share the rate but it is very low.

[scurvy]

You'll get fragmentation on every segment over 1460 bytes, which would be the majority of datagrams for a large file upload like pictures or movies. Only way to work around this is to run jumbo frames from L4 to L7. You can't magically encapsulate IP in IP at 1460 segments without fragmenting.