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

Tillman Hodgson wrote:

> On Wed, Apr 21, 2004 at 05:18:26PM -0400, Gary Corcoran wrote:
> 
>>Charles Swiger wrote:
>>
>>>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.]
>>
>>Huh?  255-- == 254, not 0.  A TTL of 255 just allows the maximum possible
>>number of hops, before being declared hopelessly lost.
> 
> 
> Exactly -- if you see an incoming packet with a TTL of 255, it must've
> originated on a directly connected system /or it would've already been
> decremented to 254 or lower/.

Ah, yes, of course.  I thought the original poster was implying
that the packet could only exist on a direct connection, and
wouldn't be passed along to another hop if it had a TTL of 255.
But I guess I just got the wrong impression - sorry for the confusion.
In any event, it still seems like 255 is overkill for this application...

Gary


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