On Tue, 2012-04-10 at 21:42 -0300, Henrique de Moraes Holschuh wrote: > On Tue, 10 Apr 2012, John A. Sullivan III wrote: > > On Tue, 2012-04-10 at 21:10 -0300, Henrique de Moraes Holschuh wrote: > > > On Tue, 10 Apr 2012, Martin T wrote: > > > > It's a well known fact that even most(with exceptions like ASR1K) of > > > > the high-end Cisco or Juniper routers handle ICMP traffic in routing > > > > engines not in ASIC's which means that they share the CPU time with > > > > other processes. How prioritized is ICMP handling in modern Linux 2.6 > > > > and newer kernels? Is it possible to prioritize ICMP handling in > > > > kernel? > > > > > > AFAIK, it has the same priority of every other packet that makes it to the > > > IP stack. > > > > > > Easy depriorizing is possible by outright dropping incoming ICMP packets > > > in the iptables layer, before it is processed by the IP stack. > > > > > > I suppose advanced NICs might be able to use receiver-side flow-steering > > > to > > > priorize or depriorize ICMP packets before delivering them to the driver, > > > or > > > you could steer them all to a particular core. > > > > > > I fear you will probably need to ask this question in the netdev ML if > > > you want a better answer. > > > > > Setting up a qdisc via the tc utility would be a more controlled way > > than simply drop or not drop. Alas, it is not one of the simpler things > > to do in Linux - John > > I suppose so, but that would require the use of ifb devices. That is likely > more expensive than handling the ICMP in the first place (with kernel ICMP > reply rate-limiters configured, obviously), so it might not work as well as > one would like it to. <snip> I did not read the original post but I'm not sure why it would require IFB interfaces. I have found I only use them if I need to shape rather than police ingress traffic or if I need to do identical traffic shaping on multiple interfaces. Then again, I have not experience configuring kernel ICMP reply rate limiters - John
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