MIT open courseware has a course on Performance Engineering which details some of the types of low level optimizations that can be done. It requires a lot of measuring and problem specific solutions.

I’ve helped with that course in the past. It’s awesome. It’s completely unrelated to WAN networking. I found the IETF groups working on these problems more helpful.

Thanks. Any specific recommendations for someone fairly new to low-level networking? IETF docs can be a little dense :)