ACE system stability with multi-context

Question

Question... if the ACE module is configured with multiple contexts, and one of the contexts hits its max resource limitations for a given resource thereby resulting in dropping excess resources, will this cost the entire ACE system, or is it limited only to the one context?
For example, if a context configured for a max of 3000 connections/second receives 300000000 connections/second due to a virus outbreak/DoS attack, will this attack affect other contexts, or will the dropping of the excess connections be seamless to other contexts? Also, does the ACE drop the excess traffic in hardware, or must it be examined by a cpu?
Thanks!!
-Lee

Answer 1

Generally, the individual contexts operate independently from one another. So if one context reaches it's upper defined limit, that affects only that context.
The ACE has hardware-based support for many of it's operations, and to the best of my knowledge, connection processing is handled by one of its 16 ME's (MicroEngine). I've never seen a benchmark test that shows how e.g a DoS-attacks affects the entire module, nor have I tried it myself, but maybe someone else here at the forum can provide you with some information on that.
BTW, try and check out theese to links. The first one describes the ACE hardware architecture, including the ME's and how they're used for processing traffic. The other one is a test conducted by Miercom on the ACE module, maybe this can provide you with some information on how the ACE handles a sudden increase in traffic during an attack.
http://www.cisco.com/en/US/customer/prod/collateral/modules/ps2706/ps6906/White_Paper_Connection_Handling_within_the_Cisco_Application_Control_Engine_Module_Hardware.html
http://www.cisco.com/en/US/prod/collateral/modules/ps2706/ps6906/prod_brochure0900aecd806d1c90.pdf
hth
/Ulrich