Other possible protection against RST/SYN attacks (was Re: TCP RST attack

Mike Tancsa mike at sentex.net
Wed Apr 21 13:41:56 PDT 2004


At 04:35 PM 21/04/2004, Charles Swiger wrote:
>On Apr 21, 2004, at 4:14 PM, Mike Tancsa wrote:
>>What side effects if any are there?  Why is the default 64 and not some 
>>other number like 255...
>
>The default TTL gets decremented with every hop, which means that a packet 
>coming in with a TTL of 255 had to be sent by a directly connected 
>system.  [ip_ttl is an octet, so it can't hold a larger TTL value.]  A 
>packet with a TTL of 64 could have been many hops away.

Thanks, I realize that.  My question is, what unintended consequences might 
happen if the default is changed to 255 from 64.  As one poster said, if a 
packet generated by that host had a ttl of 255, it would bounce around a 
lot more if it was trying to reach a host with a bad route somewhere.

I am no IP expert, but I have been around long enough to know that these 
default values get set only after long arduous debates and often there are 
tradeoffs by raising or lowering a value.  I guess I am trying to find that 
original debate to see what I might be in for by implementing this with my 
peers who request it.

         ---Mike 



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