[CentOS] How to load balance interrupts of a NIC on the PCI-MSI-edge driver in CentOS? :(

Tilman Schmidt t.schmidt at phoenixsoftware.de
Thu May 30 14:04:16 UTC 2013


Am 21.05.2013 20:05, schrieb Alex Flex:
> Why is clearly so significantly expensive for the recieving side rather 
> than the sending side to process a syn flood if they have identical 
> hardware?

Sending is fundamentally less work than receiving.

The sender just puts whatever it wants to send on the line.
The receiver has to recognize it, analyze it, find out whether
it is the intended recipient, match it with what it received
before, keep state, etc.

In the case of a SYN flood, the sender exacerbates this on
purpose, by reducing its own workload (exploiting the fact
that it doesn't really want to communicate) and maliciously
increasing the receiver's workload (forcing it to maintain
enormous numbers of half-open connections).

So it's really quite unsurprising that a SYN flood puts less
load on the sender than on the receiver.

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