[toomim]

TCP congestion control relies on packets being dropped to signal that a link is congested.

L4S actually includes an extra bit of information in IP packets that routers can mutate to explicitly say when they are congested.

This means that you (a) don't need to play exponential backoff games, (b), don't need to re-send redundant packets, and (c) don't need big buffers in routers.

You need big buffers in routers because otherwise exponential backoff goes crazy. But when you add big buffers, you get latency, which is another kind of suck.

In order to avoid latency, you need to avoid buffers, which is hard unless you avoid exponential backoff. To avoid exponential backoff, you need routers to actually communicate their congestion, by sending more information. L4S does that by using an unallocated bit in IP packets.

[tjoff]

I'll need to read up on this, but one potential misuse of this is to just always/often set that bit on traffic you want to suppress.

Which feels much easier and much less heavy-handed than what you can to today. Which technically is a great thing but just wondering about misuse aspect.

[0xdeadbeefbabe]

A router could pretend to drop packets too, but that would result in higher latency. With L4S can a router cheat and get lower latency?