Re: port 80 is open
From: Daniel Crichton (news_at_worldofspack.co.uk)
Date: 06/18/04
- Next message: Daniel Crichton: "Re: port 80 is open"
- Previous message: Wim Roffal: "Re: Zonealarm and localhost"
- In reply to: JC: "Re: port 80 is open"
- Next in thread: Tim Smith: "Re: port 80 is open"
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] [ attachment ]
Date: Fri, 18 Jun 2004 10:08:18 +0100
"JC" <jhoppyc@westnet.com.invalid> wrote in message
news:1ro4d0h6b375625usp3ilj0oi843m367fd@4ax.com...
> On Thu, 17 Jun 2004 09:26:49 +0100, "Daniel Crichton"
<news@worldofspack.co.uk> wrote:
> Does a hardware firewall change this process? I can imagine that what
you said above would be true if a software firewall is used since that is
> running on the PC itself. However, a hardware firewall is independent of
the PC so the ISP's router would see the hardware firewall but not the PC
> itself if the firewall drops packets initiated from the WAN. However, my
ISP would know that I am active since it would see packets coming from me
> at various times during the day and would be adding up the bytes
sent/received to get to a monthly figure which it then uses to determine
whether to
> throttle the link back if the monthly figure exceeds a preset target.
Since that is the case why would it send ICMP host unreachable packets?
It would only send the packets if your hardware firewall was turned or
disconnected. If you have a connection to your ISP at all (you have a piece
of hardware connected at your end of the line that is turned on and has been
allocated an IP address) then it won't send the unreachable packets - it
doesn't matter if your PC is turned off.
> > On the other hand, if the upstream router always sent an ICMP
unreachable
> > response, you'd never make a connection to anything on the internet,
> > rendering it useless - eg. if you tried to open a web site, the server
would
> > return a TCP packet with the first bit of data, get the ICMP unreachable
> > packet, and then close the connection as your IP is seen as not
connected.
>
> I guess the upstream router sees my traffic going out to the ip address
and uses those bits of info to stop sending ICMP host unreachable packets.
It has nothing to do with traffic being generated by your PC. When you are
physically connected to the ISP you have been allocated an IP address, when
you disconnect (either your Network card/stack tells the ISP router to close
the connection, or the ISP router can no longer get responses at the
physical/network layer) that IP is no longer allocated and then the router
will respond to data sent to that IP with the ICMP host unreachable data. It
might be worth you reading up on the concepts of networking, specifically at
how routers interact at the various layers with equipment connected to them.
I don't pretend to understand it all, but I know the basics enough to
understand the principles.
Dan
- Next message: Daniel Crichton: "Re: port 80 is open"
- Previous message: Wim Roffal: "Re: Zonealarm and localhost"
- In reply to: JC: "Re: port 80 is open"
- Next in thread: Tim Smith: "Re: port 80 is open"
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] [ attachment ]
Relevant Pages
|
