IPP> MOD - Client-side ONLY 'ipp:' scheme

IPP> MOD - Client-side ONLY 'ipp:' scheme

IPP> MOD - Client-side ONLY 'ipp:' scheme

Ira Mcdonald x10962 imcdonal at eso.mc.xerox.com
Tue Nov 3 15:05:16 EST 1998

Hi Paul Moore and IPP folks,                   Tuesday (3 November 1998)

Paul Moore, please poke holes in the following.  Long ago, you stated
that 'ipp:' scheme URL should NEVER be carried in the over-the-wire
IPP/HTTP protocol.  You were right!

Shivaun Albight and other printer implementors, this proposal has NO
impact on existing IPP printers OR existing IPP clients.

While editing the SLPv2 'printer:' template for IPP alignment, I found
a serious problem:  to advertise IPP printers in SLPv1 (Service Location
Protocol Version 1, RFC 2165, June 1997) a registered scheme of 'ipp:'
is necessary (because abstract services like 'printer:' were only added
in the newer SLPv2, now in IETF Last Call).

Here's a proposal for a minor change to future IPP clients and servers.
This proposal REMOVES ALL redundant security or other parameter(s) in
the 'ipp:' scheme.  The simple premise is that a client who wants to use
secure printers MUST be installed in a network with directory services.

1)  All IPP Clients (in the future):
    a) SHALL accept 'ipp:' scheme printer URL from end-users;
    b) SHALL display 'ipp:' scheme printer URL to end-users;
    c) SHALL translate 'ipp:' URL to 'http:' for use in HTTP headers;
    d) SHALL translate 'ipp:' URL to 'http:' for all IPP attributes in
    'application/ipp' MIME bodies (ie, IPP requests or responses).

2)  Secure IPP Clients (in the future):
    a) SHALL lookup IPP printer URL via the 'ipp:' scheme in SLP, LDAP,
    or other directory service, before accessing the IPP printer;
    b) SHALL read 'printer-uri-supported' and 'uri-security-supported'
    IPP Printer object attributes from the directory service to discover
    security info (eg, using the SLPv2 'printer:' template).

3)  All IPP Printers (in the future):
    a) SHALL put 'printer-uri-supported' and 'uri-security-supported' in
    ALL of their directory service registrations (current requirement).
    b) SHALL advertise ONLY 'ipp:' scheme URL in directory services
    (new requirement).

Let's discuss this at our weekly IPP Telecon tomorrow.

- Ira McDonald (outside consultant at Xerox)
  High North Inc

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