Randall,
At Prolexic we have tested, used, and worked with most current IPS
platforms. They all make claims of "multi-gig" functionality, when in
reality, each one can only handle those traffic levels in very specific
lab conditions designed just to prove the point that they can actually
pass a "gigabit" of traffic. When on a real network with
who-knows-what flowing over the wire, gigabit speeds on an IPS doing
useful stuff is rather hard to achieve.
The definition of "gigabit" seems to very from vendor to vendor; some
call their hardware multi-gigabit just because they have more than one
GigE interface on the device: 4 GigE interfaces in that configuration
means the device can do 4 gigabit - not 2 ingress/egress for a total of
2 gigabit, but a total of 4 gigabit.
See: http://www.toplayer.com/content/cm/pr131.jsp for an example of
the above.
I'm sure every IPS vendor would be at 10 gigabit today if the 10
Gigabit ports were at a low cost, but then their processing engines
would not support that packet rate and we would be where we are today
with current 1 gigabit IPS devices.
Further, to do a gigabit of traffic on a single link may not be that
bright as well. One would hope that a gig of traffic would have been
split across several gigabit interfaces all running at a lower average
bandwidth so you can burst and allot for failures.
What we are finding, to terminate and process more than one gigabit of
traffic is difficult; some modern gigabit switches do not do "trunking"
or OSPF load balanced multiple gige interfaces very well (destination
mac addresses can be the same causing load balancing algorithms to do
goofy stuff), so just having the capacity to do more than a gig can get
rather tricky. When you put an IPS in-line with an already difficult
environment ( or a pair of IPS devices) you run into state table
synchronization issues, symmetrical routing problems, and a whole lot
of other messy stuff.
I could keep going on and on about IPS failures we have experienced but
that would not do anyone any good. When it comes down to it, each
device on the market seems to excel at one or two items and the rest of
the "features" beyond what they are good at appear to mostly be bolt-on
for marketing.
Here are a few high-throughput IPS shopping tips:
1) Identify what the IPS is to do, if that's "everything" then you
should adjust your expectations.
a) If it's to do DDoS mitigation, what aspects of mitigation? No
box can stop all of the attacks correctly, so don't expect to stop all
of your problems with an IPS, in most cases they can cause more
problems then you could imagine.
b) If it's doing string matching, what exact signatures do you need
- the less you run the more throughput you will see.
2) Understand your traffic and how the IPS will work with that traffic
a) If your traffic is just HTTP stuff, your IPS could do well doing
limited checks to add value.
b) If your traffic is mixed (ISP) then good luck unless you are
trying to stop a specific worm or rate limit stuff.
c) If you are dealing with encryption, then an IPS can't do much for
you, unless you are decrypting and re-encrypting your traffic.
3) Understand the underlying mechanism that the hardware uses to do its
job.
a) String matching may be good, but what about fragments?
b) What type of algorithmic things does it do to your traffic?
b) Does it do some sort of in-line tricks with the packets?
4) Never listen to sales people
5) Don't trust "industry" tests, they are just bought logos. Real
world testing of a device takes many months and must meet criteria that
nobody would ever expect (people build interesting networks out there.)
I would suggest you do a demo and a bake off with your vendors as well.
After you get a demo IPS units, go buy an Ixia and verify that the
device will do what it says it will and _do not_ put it in-line with
your production traffic as a test. In 100% of the cases we have worked
with, the box performed much lower than it was advertised and in some
cases a feature is just a ruleset that denies traffic rather than
cleaning traffic. There are also "side effects" that are very
unexpected with all the different IPS devices. A good expectation is
that a gigabit IPS can do about 50% of line rate on most things and
full line rate on some things.
Good luck and happy shopping,
-Barrett
Barrett G. Lyon
Founder & CTO
Prolexic Technologies - The leaders in DDoS Security!
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