First I'd just like to state the fact that lag doesn't mean low FPS. Please stop saying lag when you actually have low fps. Lag is when your internet connection to the game is bad.
Anyway, I've been having an odd issue with lag all day today. I seem to be the only one having this issue in my group of friends, and it only happens on Rust. When I play other games I have no lag issues. It's been working fine the past few days, but suddenly when I got on today it's been very laggy. I die from zombies from 30 feet away, I can't open boxes most of the time, people stand still or move like a slideshow, etc. It's unplayable.
I posted a bug report earlier yesterday but there's been no response.
Here is my ticket with a list of everything I've tried: https://github.com/Facepunch/rust-issues/issues/961