Re: not using debian as firewall!

[Ossama Othman <othman@cs.wustl.edu>]

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
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. :)

-Ossama
______________________________________________________________________
Ossama Othman <othman@cs.wustl.edu>
58 60 1A E8 7A 66 F4 44  74 9F 3C D4 EF BF 35 88  1024/8A04D15D 1998/08/26