Date: Wed, 21 Apr 2004 17:18:26 -0400 From: Gary Corcoran <garycor@comcast.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: <4086E522.7090303@comcast.net> 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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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.] Huh? 255-- == 254, not 0. A TTL of 255 just allows the maximum possible number of hops, before being declared hopelessly lost. > A packet with a TTL of 64 could have been many hops away. As DES said in a later reply, 64 was probably just a reasonable, but arbitrary value. Whereas 255 would probably allow for several trips around the world, and would be overkill. Gary
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