Date: Wed, 21 Apr 2004 16:43:48 -0400 From: Mike Tancsa <mike@sentex.net> To: Charles Swiger <cswiger@mac.com> Cc: freebsd-security@freebsd.org Subject: Re: Other possible protection against RST/SYN attacks (was Re: TCP RST attack Message-ID: <6.0.3.0.0.20040421163904.0738d960@209.112.4.2> In-Reply-To: <75226E9B-93D3-11D8-90F9-003065ABFD92@mac.com> References: <6.0.3.0.0.20040420125557.06b10d48@209.112.4.2> <xzp65buh5fa.fsf@dwp.des.no> <6.0.3.0.0.20040420144001.0723ab80@209.112.4.2> <200404201332.40827.dr@kyx.net> <20040421111003.GB19640@lum.celabo.org> <6.0.3.0.0.20040421121715.04547510@209.112.4.2> <20040421165454.GB20049@lum.celabo.org> <6.0.3.0.0.20040421132605.0901bb40@209.112.4.2> <48FCF8AA-93CF-11D8-9C50-000393C94468@sarenet.es> <6.0.3.0.0.20040421161217.05453308@209.112.4.2> <75226E9B-93D3-11D8-90F9-003065ABFD92@mac.com>
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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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