North American Network Operators Group

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Re: TCP session disconnection caused by Code Red?

  • From: Jim Warner
  • Date: Mon Aug 06 20:06:56 2001

George Herbert ([email protected]) said:

    I've been told (but not given permission to forward details of
    who/how/what) that some major sites with a single router
    and relatively flat network topology are dying due to the ARP
    request flood that is being generated by Code Red scans on the
    inside of their border router choking the router.  Check the
    rate of ARP requests coming off your border router and see if
    it seems excessive; if so, that may be it.

My campus is now seeing around 500 packets per second of CodeRed 
connection requests into blocks that total 130,000 addresses.  
The work of ARPing for all that stuff is distributed across 6 
routers (mostly Cisco RSM) and they're doing OK.

The experience at Cal State campuses is variable.  They do tend to
have flat topologies behind a single entrance router.  Our neighbors
at CSU Monterey Bay melted under the load _before_ CR-II emerged. 
They had their upstream install an access list permitting an 
explicit list of campus web servers and blocking port 80 to 
everything else.  Their router is mfg by Alcatel, a PowerRail 
7652 OmniCore 5052.  I don't have a lot of details about their 
setup but I do know how big their assigned address pool is -- 
about 6000 addresses.

That leaves me wondering about the importance of quality of the
ARP implementation in the router code.  I have heard that CSU Long
Beach (Cabletron router) had similar problems.

I'm looking for anyone that knows some details of Alcatel and
SSR routers that might help us understand this.  I don't think
this is a case where the ingenuity of ASIC designers is the
important parameter.  Have any of the router benchmarks dealt 
with the capabilities and robustness of what I'm imagining must
be process-level parts of the a router implementation?

-jim warner, University of California Santa Cruz