[ale] network problems?

[Jason Day]

On Fri, Feb 14, 2003 at 02:03:23PM -0500, J.M. Taylor wrote:
> If any point between you and the place you're trying to traceroute drops
> ICMP requests, your traceroute fails.  Sounds like your DSL provider is
> blocking ICMP traffic somewhere upstream of you...my cable provider does
> afaik.

That's not entirely correct.  Traceroute works by initially setting the
TTL field on a packet to 1.  The first box that tries to forward the
packet will see that its TTL has expired, and will send an ICMP ttl
exceeded message back to the originating host (I forget the name of the
ICMP message).  So as long as the router is not blocking ICMP, a
traceroute should at least get one response.

Jason
-- 
Jason Day                                       jasonday at
http://jasonday.home.att.net                    worldnet dot att dot net
 
"Of course I'm paranoid, everyone is trying to kill me."
    -- Weyoun-6, Star Trek: Deep Space 9
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