: ==>Could traffic shaping, or similar QoS configurations, be used to solve
: ==>such issues in a more general way?
:
[...]
: It has information on using Cisco's Committed Access Rate (CAR) feature
: to rate-limit traffic such as ICMP echo/echo-reply and TCP SYNs.
Thanks, everyone, for your responses. It seems that lots of us agree
that CAR sounds like a wonderful mechanism for taming smurf-like
attacks. (Thanks, Cisco and others who have provided it.)
So isn't this the solution(**) to smurfing that we should be lobbying for?
Consider: Using CAR to limit ICMP to a statistically normal range on
all links has these features:
* It can be implemented from the core out
* It must be implemented by clueful network operators (because they
run the core)
* It must be implemented on a relatively small handful of
rigorously-maintained routers
Compare this to the drive for limitations on directed broadcasts:
* It must be implemented at the edges
* It must be implemented by widely-varying clue levels
* It must be implemented on hundreds of thousands of routers that no
one ever touches
In short, the core grows slower, and is run by people with more experience.
If the problem can be addressed there, then it seems like we *must* address
it there.
Comments, please.
(**) You could well argue that limiting ICMP traffic on core/distribution
links doesn't actually solve the problem -- lots of trash traffic
can be generated on networks whose routers allow directed broadcasts.
But that's if we define the problem to be trash ICMP because
hosts reply to pings (or fraggle, or whatever); in such a case,
traffic limitations are simply a kludge.
However, if you define the problem to be packet floods, then I think
CAR provides a viable and real solution. After all, directed broadcast
is a useful tool; in such a definition, disabling it on a network
is a kludge. My limited studies seem to show that there are enough
smurf amplifiers on the Internet to easily saturate OC-48s. Perhaps
the real problem *is* flooding -- not directed broadcast.