On 8 Jun 2015, at 22:18, Ramy Hashish wrote:
Even if the transit provider won't be involved in the mitigation
process
and the GRE tunnel is used only for injecting the traffic back to the
end
customer, the customer's dirty traffic will pass through some
congestion
points (most likely near the IGWs) throughout the transit provider
network.
The Internet is a best-effort network (of networks). People with
operational experience understand this and don't find it remarkable, nor
do they make unfounded general assertions.
And concerning point b) as per Arbor representatives in my region,
Arbor's
system takes up to five minutes to mitigate the attack (starting from
the
hit of the first dirty packet), so there will be a period of time
where the
dirty traffic (or at least some of it) will be coming down all the way
to
the end customer until you completely mitigate the attack.
All the commercial IDMS systems from various vendors of which I'm aware
have operator-configured latency values for both
detection/classification/traceback and for mitigation activation; these
functions are intended to allow the operator to find the right balance
between rapidity in responding to operationally-significant events and
not being deluged with alerts/mitigations regarding events with little
or no operational significance. Different operators with different
customer bases in different situations tend to tune them differently,
depending upon their situationally-specific priorities, operational
practices, etc.
It isn't appropriate for a vendor employee like me to get into a
vendor-specific discussion on the NANOG list; if you'd like to
understand how a) the above assertion about '5 minutes' is incorrect and
b) how DDoS mitigation in general focused on minimizing both
underblocking and overblocking, rather than on the failed 'IPS' model,
contact those Arbor representatives of whom you speak and have them
engage me in joint discussions.
-----------------------------------
Roland Dobbins <rdobb...@arbor.net>