<<On Sat, 17 Mar 2001 22:03:53 +0100, Harald Alvestrand
<Harald(_at_)Alvestrand(_dot_)no> said:
That's my reason to use the TTL decrement; if someone shows me a device
where a packet comes in on one interface with a certain TTL, and it comes
out on another interface with a lower TTL but no other significant changes,
I call it a router.
Except that I can now show you a ``stealth router'' -- a device which
acts in all respects like a router, except that it does not decrement
the TTL field or generate ICMP Time Exceeded messages. (Typically
this is done to interpose a packet-filtering router without making it
visible to remote attackers.)
-GAWollman