You made an excellent point at the end of your note below.
A sophisticated application layer gateway (ALG) is necessary
for any INDP targets accessible over the Internet but 'obscure'
because of NAT (network address translation), Windows connection
And the problem of configuring the ALG to handle the *particular*
choice of security measures (one-time-passwords and so on) mandated
in each different customer environment is intractable in my
I like INDP, but I consider it only plausibly an intranet solution.
The IESG and the IAB are certainly alive to the loss of opacity
in the public Internet and won't miss the security implications
for INDP. Has anyone read the I-D on an SNMP ALG for NAT boxes?
This stuff is often more bother than it's worth...
- Ira McDonald, consulting architect at Xerox and Sharp
High North Inc
From: kugler at us.ibm.com [mailto:kugler at us.ibm.com]
Sent: Wednesday, June 21, 2000 3:09 PM
To: ipp at pwg.org
Subject: Re: IPP> TES: Mandatory IPP notification agreement
[Added subject line and this P.S.:]
henrik.holst at i... wrote:
>> Well it was my understanding that we didn't agree on a mandatory method.
> And the INDP method
> won't go through a firewall, so if you are searching for a mandatory
> I would say MAILTO.
I agree, INDP won't go through firewalls.
---------------------- Forwarded by Carl Kugler/Boulder/IBM on 06/21/2000
04:07 PM ---------------------------
From: Carl Kugler on 06/21/2000 03:39 PM
To: ipp at pwg.org
From: Carl Kugler/Boulder/IBM at IBMUS
"Zehler, Peter" <Peter.Zehler at u...> wrote:
> My preference is that INDP be mandated. I feel that programmatic
> notification is critical to the development of robust IPP applications.
> of those applications would be QUALDOCS. In the definition of IPP, and
> associated notification mechanism, I am concerned primarily with client
> /server communications. End user notification, while useful, is not my
> primary objective. It is true that infrastructure will have to be
> configured to allow this traffic to pass. The same is true of outbound
> requests. I imagine that most of our printers will also implement mailto.
> have no objections to allowing both, but I think only one should be
Actually, in many cases the infrastructure does not have to be configured
to allow outbound IPP requests. I've always been able to connect to IPP
Printers on the Internet with an IPP client here inside the IBM firewall.
(In fact, I remember connecting my client to your Printer a few years ago!)
We run a SOCKS Internet gateway here, and I can make a TCP connection to
any host:port on the Internet.
"McDonald, Ira" <imcdonald at s...> wrote:
> Lastly, Peter you jumped from port filtering by firewalls
> to MIME type filtering - but the latter requires that the
> firewall have an Application Layer Gateway (ALG) to figure
> out the protocol and THEN to find the MIME type inside the
> protocol envelope.
>> Personally, I agree with Henrik about selecting email as
> the IPP mandatory notification method.
Most firewalls allow insiders to make outbound connections (perhaps
indirectly), but prevent outsiders from making inbound connections. Very
few corporate firewall administrators would be willing to simply open a
port and allow anybody to make inbound connections to arbitrary addresses
inside the firewall. Here at IBM, making an inbound connection requires
full-blown authentication, encryption, one-time passwords, etc. (by
strictly enforced corporate policy). We use Aventail for this. Also, in
many cases, machines inside a firewall are simply not addressable from
outside, due to network address translation (NAT), IP Masquerading, Windows
connection sharing, etc. You'd need a really sophisticated
application-level gateway to deal with these issues.