re: gaming ECN
apologies for not replying to the right message, I deleted them earlier before
deciding to respond.
Programmers are going to game ECN to their advantage (or at least to their
perceived advantage)
There are three ways to mark flows as congested
1. at the same level that you drop packets and then drop the packets at this
level (why bother)
2. at the level that you drop packets for non-ECN flows, you mark and allow ECN
flows to continue
3. at a level below the point that you drop packets for all flows, you mark ECN
flows as congested
If you do #2, then flows with ECN effectively get priority over flows without
ECN (as you don't actually force them to back off, you are just asking them to)
Programmers will mark everything with ECN and not back off
If you do #3, then flows with proper ECN yield to flows without ECN, giving
effective priority to flow without ECN
Programmers will not use ENC as it puts their traffic at a disadvantage
If everyone uses ENC and backs off properly, then #3 is better as you don't have
the delays caused by re-sending packet. But in a mixed environment, ECN is going
to be gamed one way or the other.
David Lang
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