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RE: key change for TCP-MD5

  • From: Owen DeLong
  • Date: Fri Jun 23 18:45:10 2006

Why couldn't the network device do an AH check in hardware before passing
the
packet to the receive path?  If you can get to a point where all connections
or traffic TO the router should be AH, then, that will help with DOS.

If you can limit what devices _SHOULD_ talk to the router and at least
define
some subset of that from which you demand AH on every packet, that helps but
isn't a complete solution.

Owen


--On June 23, 2006 11:49:33 AM -0700 "Barry Greene (bgreene)"
<bgreene@cisco.com> wrote:

> 
>  
> 
>> If DOS is such a large concern, IPSEC to an extent can be 
>> used to mitigate against it. And IKEv1/v2 with IPSEC is not 
>> the horribly inefficient mechanism it is made out to be. In 
>> practice, it is quite easy to use.
> 
> IPSEC does nothing to protect a network device from a DOS attack. You
> know that.
> 
> DOS prevention on a network device needs to happen before the TCP/Packet
> termination - not the Key/MD5/IPSEC stage. The signing or encrypting of
> the BGP message protects against Man in the Middle and replay attacks -
> not DOS attacks. Once a bad packet gets terminated, your DOS stress on
> the router kicks in (especially on ASIC/NP routers). The few extra CPU
> cycles it takes for walking through keys or IPSEC decrypt are irrelevant
> to the router's POV. You SOL if a miscreant can get a packet through
> your classification & queuing protections on the router and have it
> terminated. 
> 
> The key to DOS mitigation on a network device is to have many fields in
> the packet to classify as possible before the TCP/Packet termination.
> The more you have to classify on, the more granular you can construct
> your policy. This is one of the reasons for GTSM - which adds one more
> field (the IP packet's TTL) to the classification options. 
> 
> Yes Jared - our software does the TTL after the MD5, but the hardware
> implementations does the check in hardware before the packet gets punted
> to the receive path. That is exactly where you need to do the
> classification to minimize DOS on a router - as close to the point where
> the optical-electrical-airwaves convert to a IP packet as possible.



-- 
If it wasn't crypto-signed, it probably didn't come from me.

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