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Old 07-27-2010, 02:27 PM   #1
pawelch
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What happened to syn cache?


Hello everyone,
I have a general question and decided to post it here. Hopefully, I have picked a correct category. The thing I have been trying to figure out is the syn-cache mechanism. I know that it used to be utilized as a method to mitigate the impact of (D)DoS attacks. I would like to know what happened with it? Is it still added to the Linux systems? Perhaps I am missing something, and cannot find the correct man page about it. Is it the thing, that it is only for NetBSD project?

Thank you in advance for your time and help.

Best wishes
 
Old 07-27-2010, 02:49 PM   #2
zirias
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You're referring to this?
http://cr.yp.to/syncookies.html

AFAIK, it is still part of linux. There's even a RFC:
http://tools.ietf.org/html/rfc4987
 
Old 07-27-2010, 05:55 PM   #3
pawelch
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hey zirias, thank you for your answer.
as far as syn cookies goes, I think it has been developed independently of syn cache. Even in the RFC you refer to, there is a solid distinguishment between those two. In the early years of the development of SYN Cookie, I think they have been used simultaneously in order to improve the efficiency of the SYN flood mitigations techniques. In simpler words, as soon as the hash-table of the SYN Cache was about to fill up, the SYN Cookie was triggered. Nowadays, I think there is only SYN Cookie in use,or, I have not come across a relevant reference yet.

If any of you knows where I can find any information about this issue, please let me know. I will be more than grateful for your help.

Thank you one more time for all your resources used up accordingly

Cheers!!!
 
Old 07-28-2010, 03:42 AM   #4
resetreset
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Yes, I would like this information too!
 
Old 07-28-2010, 03:47 AM   #5
zirias
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Ah then I'm sorry, I always thought syn cookies were just the "next step" and replaced syn cache... I didn't know about the technique to use them both together.
 
Old 07-28-2010, 04:45 AM   #6
pawelch
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Hey,
That's what I thought at the beginning (that SYN Cookies were the improvement). But apparently, SYN Cache was being implemented in the NetBSD project, and in parallel, Linux was being backed up with SYN Cookie. After some time, they worked together. However, the question is - does SYN Cookies mechanism utilize a standard backlog queue? If it does so, then, what happened to SYN Cashe again ?

Cheers!
 
  


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