Re: not using debian as firewall!
On Tue, Apr 13, 1999 at 04:06:13PM -0500, Ossama Othman wrote:
> Hi,
>
> On 13 Apr, David Welton wrote
> [snip]
> > Eh? Ping's are ICMP packets, which operate beneath the tcp layer.
> [snip]
> > >From RFC 791:
> > +-----+ +-----+ +-----+
> > | TCP | | UDP | ... | ... |
> > +-----+ +-----+ +-----+
> > | | |
> > +--------------------------+----+
> > | Internet Protocol & ICMP |
> > +--------------------------+----+
>
> Please excuse me. This is me nitpicking... :-)
>
> I believe it is more accurate to say that ICMP is a required part of IP
> rather than say "IP & ICMP" as is shown in your diagram. It is also
It's not my diagram - it's in the RFC!
> more accurate to say that ICMP operates within IP instead of beneath
> TCP. TCP operates over IP but ICMP need not necessarily run beneath
> TCP, as your diagram shows. ICMP is the "error and control messages"
> part of IP. See "Internetworking With TCP/IP - Volume I" chapter 9 by
> Douglas E. Comer. It states that "ICMP messages travel across the
> internet in the data portion of IP datagrams." Therefore, ICMP is
> independent of TCP. :)
When I said 'under', I meant at a lower level. And of course it's
independent of TCP - that's why inetd has absolutely nothing to do
with it, which is why I brought this up at all:-)
I'll see your "Internetworking With TCP/IP - Volume I" and raise you
one TCP illustrated, Volume I;-))
Ciao,
--
David N. Welton | Fortune rota volvitur - descendo minoratus
davidw@prosa.it | alter in altum tollitur - nimis exaltatus
http://www.efn.org/~davidw | rex sedet in vertice - caveat ruinam!
www.debian.org - www.prosa.it | nam sub axe legimus - Hecubam reginam
Reply to: