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FTSC                             FIDONET TECHNICAL STANDARDS COMMITTEE
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Publication:  FRL-1017
Revision:     1
Title:        The ICM flag
Author(s):    Michiel van der Vlist
Issue Date:   13 July 2005
Review Date:  N/A
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Contents:
              1. Introduction.
              2. The ICM flag.
              3. Clarification.
              4. References.
              5. Contact Info.
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Status of this document
-----------------------

  This document is a Fidonet Reference Library document (FRL).

  This document preserves FSP-1033.001 -- this flag has been approved
  for use and incorporated into the updated FTS-5001.002 ("Nodelist
  flags and userflags") document.

  This document is released to the public domain, and may be used,
  copied or modified for any purpose whatever.


1. Introduction
---------------

  One of the problems with the present nodelist format is that
  there is no way for dual capable systems (PSTN-IP) to specify
  different on-line times for the PSTN section and the IP
  section. There is the CM flag to signal 24/7 capability but there
  is no way to signal 24/7 capability for IP combined with limited
  opening hours for PSTN.

  The use of IP is gradually increasing but PSTN will still be an
  important factor for quite some time, so sysops may want to find
  a means to eliminate the cost of a dedicated PSTN line without
  completely dropping PSTN support. One solution is to share the
  line with a voice line and to only support limited opening
  hours on the PSTN side. They will be ZMH only or carry a Txy flag
  to signal opening hours. They can not fly the CM flag. Yet if the
  node has a dsl or cable connection, the IP mailer can very well
  be online 24/7. The proposed ICM flag takes care of this.
  

2. The ICM flag
---------------

        ICM    Indicates that the node is available for mail 24 hours
               a day by means of one or more of the IP protocols as
               mentioned in FTS-5001 section 1 paragraph H.

               This flag may only be used in combination with one or
               more of the flags mentioned in FTS-5001 1.H.(f.e IBN)

               This flag must not be used in combination with the CM
               flag.

               If the node flies any Tyz, #?? or !?? flags in
               addition to the ICM flag, those other flags are
               assumed to only apply to PSTN connects.

3. Clarification
----------------

  PSTN only node:    -  Flies CM flag when available 24/7.

  IP only node:      -  When available 24/7 flies either CM flag or
                        ICM flag. (But not both) CM is preferable
                        as all existing software will recognise it.

  PSTN/IP node:      -  Flies CM flag when both PSTN and IP sections
                        are available 24/7.
                     -  Flies ICM flag when PSTN section is only
                        available during limited hours but IP
                        section is available 24/7.
                     -  Never flies both. 

4. References
-------------

  [FTS-5000] The distribution nodelist

  [FTS-5001] Nodelist flags and user flags.

5. Contact Data
---------------

  Michiel van der Vlist
  Fidonet:  2:280/5555
  E-mail:   pa0mmv (at) vrza.org


History
-------

   Rev.1, 20040614: Initial Release.
                    Principal author Michiel van der Vlist.
   ------ 20050713: Reassigned to FRL-1017.001

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