Re: Stopping SYN floods.

Taner Halicioglu (taner@cerf.net)
Thu, 17 Oct 1996 18:22:15 -0700 (PDT)


On Thu, 17 Oct 1996, Chris Thornhill wrote:

> solution to this (in theory). Forgive my lack of proper terminology
> here, but couldn't the tcp/ip stack be written so that if its connection
> table for a particular port fills, the next incoming SYN packet immediatly
> causes the oldest connection that is waiting for an ACK from it's SYNACK
> to time out?

Well, since most SYN floods are coming in at a very rapid pace, this
method would simply kick out the old, waiting, SYNs just as fast as new
ones came in. Hence, valid connections would have a hard time getting
established.

You'd have better luck establishing a valid connection by RANDOMLY
dropping a queued SYN packet.

Anyway, I don't know if this is the right place to be discussing this
already-buried-into-the-ground-on-other-lists subject :-)

-Taner
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