DDOS, IDS, RTBH, and Rate limiting

Roland Dobbins rdobbins at arbor.net
Thu Nov 20 21:59:18 UTC 2014

On 21 Nov 2014, at 4:36, Pavel Odintsov wrote:

> I tried to use netflow many years ago but it's not accurate enough and
> not so fast enough and produce big overhead on middle class network
> routers.

These statements are not supported by the facts.  NetFlow (and other 
varieties of flow telemetry) has been used for many years for traffic 
engineering-related analysis, capacity planning, and security purposes.  
I've never seen the CPU utilization on even a modest mid-range router 
rise above single-digits, except once due to a bug (which was fixed 

Flow telemetry scales and provides invaluable edge-to-edge traceback 
information.  NetFlow telemetry is accurate enough to be used for all 
the purposes noted above by network operators across the world, from the 
smallest to the largest networks in the world.

There are several excellent open-source NetFlow analysis tools which 
allow folks to benefit from NetFlow analysis without spending a lot of 
money. Some of these projects have been maintained and enhanced for many 
years; their authors would not do that if NetFlow analytics weren't 
sufficient to needs.

Packet-based analysis is certainly useful, but does not scale and does 
not provide traceback information.

> FastNetMon can handle 2-3 million of packets per second and ~20Gbps on 
> standard i7 2600 Linux box with Intel 82599 NIC.

See the comments above with regards to scale.  This is inadequate for a 
network of any size, it does not provide traceback information, and it 
does not lend itself to broad deployment across a network of any size.

I'm sure FastNetMon is a fine tool, and it's very good of you to spend 
the time and effort to develop it and to make it available.  However, 
making demonstrably-inaccurate statements about other technologies which 
are in wide use by network operators and which have a proven track 
record in the field is probably not the best way to encourage folks to 
try FastNetMon.

Roland Dobbins <rdobbins at arbor.net>

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