From: brunner@practic.com (Thomas Eric Brunner)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Firewall usage (was: Re: ping works, but ftp/telnet get "no route)
Date: 24 Jul 92 16:10:06 GMT
Reply-To: brunner@practic.UUCP (Thomas Eric Brunner)
Organization: Practical Computing Inc., Sunnyvale

In article <1992Jul23.142026.20112@sci34hub.sci.com> gary@sci34hub.sci.com (Gary Heston) writes:
>In article <BrsM1C.36v@cs.columbia.edu> ji@cs.columbia.edu (John Ioannidis) writes:
>>In article <BrruC8.FEo@spock.dis.cccd.edu> markb@spock.dis.cccd.edu (Mark Bixby) writes:
>>>Why would I be able to ping a site OK, but when I try to ftp or telnet to it
>>>I receive a "no route to host" error?  ....

They are probably doing packet filtering based on ports at one or another of
the routers under their adminstrative control, for reasons of their own.

>>The site you are trying to ping is running a firewall gateway, because
>>they're too lazy to beef up their host security and are relying on the
>>firewall to protect themselves against external attacks.

Hmm, an ad hominum explination, always a pleasure to read in a technical list.
Having reluctently made a few dollars working for or against host security,
I respectfully note to those not entirely convinced by the offered rational
above, that for reasons of their own, the site in question, or any site,
may have chosen to obtain hosts which meet specific local needs, and don't
as yet meet a narrow subset of features thought of as offering "security"
to ip- (or smtp-, or decnet-, or uucp-) addressable hosts. In short, they
may be heterogeneous with some hosts meeting higher locally-defined needs
than denial of unathorized use -- like computing for instance.

>I have to take exception to this remark. Use of a firewall doesn't indicate
>laziness on the part of a site; it most probably means that the persons
>responsible for the Internet connection and security of the sites' net are
>either too understaffed to maintain all the hosts on their site, or they
>don't have control over all the hosts, and are therefore not able to make
>them secure. And there are doubtless many sites that suffer from both 
>problems.

They may also have intellectual property, or operational function, which
they value sufficiently to attempt some form of administrative filtering,
in addition to the staffing and competency issues.

>>I wish I had a transcript of Dave Clark's talk at the IETF last week.
>>He said some great things about firewall gateways and mailbridges, and
>>how they've essentially destroyed the whole purpose of having an IP
>>internet, and have forced a lot of us to use mail as a transport-level
>>protocol.

Dave is usually correct, but as he thinks quite a bit more than many, and
says what he thinks, he is frequently not correct. Send him mail and ask
for a copy, or invite him to write. Perhaps he's been misstated in this
summary of his remarks. In any event, this was not one of the more important
topics on the IETF adgenda, had it been, I'm sure there would have been
other points of view expressed, as well as discussion of technical details
of implementation, which are more to the point.

I'm looking forward to John's posting, "Administrative Packet Filtering
Considered Harmfull"... in comp.security.misc, or as an internet-draft...

-- 
#include <std/disclaimer.h>
Eric Brunner, Tule Network Services
uunet!practic!brunner or practic!brunner@uunet.uu.net
trying to understand multiprocessing is like having bees live inside your head.