Dear Editor,

Here again is an updated version of the document
draft-ietf-x400ops-mgtdomains-ops-03.txt .

Please update the file in the internet-drafts directory.

Thank you.

Best regards
Alf H

=========================







   Operational Requirements for X.400 Management Domains

                  in the GO-MHS Community

                       March 16, 1993

                      Robert A. Hagens
 C=US; ADMD= ; PRMD=INTERNET; DDA.RFC-822=hagens(a)ans.net;
                       hagens@ans.net

                         Alf Hansen
C=no; ADMD= ; PRMD=uninett; O=sintef; OU=delab; S=Hansen; G=Alf
                 Alf.Hansen@delab.sintef.no

                     $ Revision: 1.16 $




                    Status of this Memo


This  document  specifies  a  set  of  minimal   operational
requirements  that  shall  be  implemented by all Management
Domains (MDs) in the Global  Open  MHS  Community  (GO-MHS).
This  document defines the core operational requirements; in
some cases, technical detail  is  handled  by  reference  to
other documents.

The GO-MHS Community is defined as all  organizations  which
meet the requirements described in this document.

This document is an  Internet  Draft.  Internet  Drafts  are
working  documents  of  the  Internet Engineering Task Force
(IETF), its Areas, and its Working Groups. Note  that  other
groups  may  also  distribute  working documents as Internet
Drafts.

Internet Drafts are draft documents valid for a  maximum  of
six  months.  Internet  Drafts  may be updated, replaced, or
obsoleted by  other  documents  at  any  time.   It  is  not
appropriate  to use Internet Drafts as reference material or
to cite them other than as a "working  draft"  or  "work  in
progress."

Please check the I-D  abstract  listing  contained  in  each
Internet Draft directory to learn the current status of this
or any other Internet Draft.

When agreement is reached, it will be submitted to  the  RFC
editor  as  an  informational document. Distribution of this
memo is unlimited. Please send comments to the authors or to
the discussion group:


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                ietf-osi-x400ops@cs.wisc.edu
C=us; ADMD= ; PRMD=xnren; O=UW-Madison; OU=cs; S=ietf-osi-x400ops





















































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1.  Introduction

There  are  several  large,   operational   X.400   services
currently  deployed. Many of the organizations in these ser-
vices are connected to  the  Internet.  A  number  of  other
Internet-connected  organizations  are  beginning to operate
internal X.400 services (for example, U.S. government organ-
izations  following  U.S.  GOSIP).  The  motivation for this
document is to foster  a  GO-MHS  Community  that  has  full
interoperability  with  the existing E-mail service based on
RFC-822.

The goal of this document is to  unite  regionally  operated
X.400  services  on  the  various continents into one GO-MHS
Community (as seen from an end-user's point of view).  Exam-
ples of such regional services are the COSINE MHS Service in
Europe and the XNREN service in the U.S.

A successful GO-MHS Community is dependent on  decisions  at
both  the  national  and international level. National X.400
service providers are responsible for the implementation  of
the  minimum requirements defined in this document. In addi-
tion to these minimum  requirements,  national  requirements
may be defined by each national service provider.

This document refers to other  documents  based  on  ongoing
work, which will be published as Prototype and Informational
RFCs. These documents are [1],  [4],  [8]  and  [9]  in  the
reference list.

This document handles issues concerning X.400 1984 and X.400
1988  to 1984 downgrading. Issues concerning pure X.400 1988
are left for further study.

We are grateful to Allan Cargille and Lawrence Landweber for
their input and guidance on this paper. This paper is also a
product of discussions in the IETF X.400 Operations  WG  and
the RARE WG-MSG (former RARE WG1 (on MHS)).


1.1.  Terminology

This document defines requirements, recommendations and con-
ventions.   Throughout  the  document, the following defini-
tions apply: a requirement is specified with the word shall.
A  recommendation is specified with the word should.  A con-
vention is specified with the word might.   Conventions  are
intended  to make life easier for RFC-822 systems that don't
follow the host requirements.

[1] is introducing a change in  the  terminology.  The  term
"WEP" is proposed to be changed to "RELAY", with the follow-
ing explanation (quote):


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"RELAY

An X.400 MTA serving one or several MHS domains.  Note  that
the  term  WEP  -Well Known Entry Point- has been used since
the early X.400ies (1987/88) until  now,  giving  the  wrong
impression  of  a single entry point (and therefore a single
point of failure).  This document proposes to use  the  term
RELAY,  reflecting  more  clearly  the  functionality of the
MTA."

Until a complete understanding  is  reached  regarding  this
possible change in terminology, the term "WEP" is still used
throughout this document.  Note that  the  definition  of  a
"WEP" and a "RELAY" is exactly the same.


1.2.  Profiles

Different communities have different  profile  requirements.
The following is a list of such profiles.

    o U.S. GOSIP - unspecified version
    o ENV - 41201
    o UK GOSIP for X.400(88)

In the case when mail traffic is going from the RFC-822 mail
service  to  the  GO-MHS  Community, the automatic return of
contents when mail is non-delivered should be  requested  by
RFC  1327  gateways  and should be supported at the MTA that
generates the non-delivery report.  However,  it  should  be
noted  that this practice maximizes the cost associated with
delivery reports.


2.  Architecture of the GO-MHS Community

In order to facilitate a coherent deployment of X.400 in the
GO-MHS  Community  it  is  necessary  to  define, in general
terms, the overall structure and organization of  the  X.400
service.   This  section  is broken into several parts which
discuss management domains, lower layer connectivity issues,
and overall routing issues.

The GO-MHS Community will operate as a single MHS community,
as defined in [1].


2.1.  Management Domains

The X.400 model supports  connectivity  between  communities
with different service requirements; the architectural vehi-
cle for this is a Management Domain. Management domains  are
needed   when   different   administrations  have  different


INTERNET-DRAFT (OPS-1)    [Page 4]       Exp. Date: 05/10/93

specific requirements.  Two types of management domains  are
defined  by  the  X.400  model: an Administration Management
Domain (ADMD) and a Private Management Domain (PRMD).

Throughout the world in various  countries  there  are  dif-
ferent  organizational policies for MDs.  All of these poli-
cies are legal according to the X.400  standard.  Currently,
X.400  service providers in a country (inside or outside the
GO-MHS Community), are organized as:

    a) One or several ADMDs.
    b) One or several PRMDs and with no ADMDs present in the country.
    c) One or several PRMDs connected to one or several ADMDs.


Or in combinations of a), b) and c).  At this  stage  it  is
not  possible  to  say  which  model  is the most effective.
Thus, the GO-MHS Community shall allow every model.


2.2.  The Well Known Entrypoint (WEP)

The X.400 message routing decision process  takes  as  input
the  destination O/R address and produces as output the name
(and perhaps connection information) of  the  MTA  who  will
take  responsibility  of delivering the message to the reci-
pient. The X.400 store and forward model permits  a  message
to  pass  through  multiple  MTAs.  However, it is generally
accepted that the most efficient path for a message to  take
is one where a direct connection is made from the originator
to the recipient's MTA.

Large scale deployment of X.400 in the GO-MHS Community will
require  a well deployed directory infrastructure to support
routing. In the GO-MHS Community X.500 is considered  to  be
the  best  protocol  for  such  an  infrastructure.  In this
environment, a routing decision can be made by searching the
directory  with a destination O/R address in order to obtain
the name of the next hop MTA. This  MTA  may  be  a  central
entry  point  into  an  MD, or it may be the destination MTA
within an MD.

Deployment  of  X.400  without  a  well  deployed  Directory
infrastructure,  will  require  the  use of static tables to
store  routing  information.  These  tables  (keyed  on  O/R
addresses), will be used to map a destination O/R address to
a next hop MTA.  In order to facilitate  efficient  routing,
one  could  build  a  table  that contains information about
every MTA in every MD.  However, this table would  be  enor-
mous  and very dynamic, so this is not feasible in practice.
Therefore, it is necessary to use  the  concept  of  a  well
known entrypoint (WEP).



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The purpose of a WEP is to act as a default entry point into
an MD. The MTA that acts as a WEP for an MD shall be capable
of  accepting  responsibility  for  all  messages  that   it
receives  that  are  destined for well-defined recipients in
that MD.

The use of a WEP for routing is defined by [1]. WEPs in  the
GO-MHS Community shall route according to [1].


2.3.  Lower Layer Stack Incompatibilities

A requirement for successful operation of the GO-MHS Commun-
ity is that all users can exchange messages. The GO-MHS Com-
munity is not dependent  on  the  traditional  TCP/IP  lower
layer  protocol  suite.  A variety of lower layer suites are
used as carriers of X.400 messages.

For example, consider Figure 1.

  -----------------------------------------------------
  !                                                   !
  !            PRMD A                                 !
  !        --------------------                       !
  !        !   o       x      !                       !
  !        !                  !                       !
  !        !     o        w   !                       !
  !        !          z       !                       !
  !        --------------------                       !
  !                                PRMD B             !
  !                            ------------------     !
  !                            !      o     o   !     !
  !    PRMD C                  !  o             !     !
  !  ------------------        !      o     z   !     !
  !  !       o        !        !                !     !
  !  !  o        x    !        ------------------     !
  !  !     o        w !                               !
  !  !        o       !                               !
  !  ------------------                               !
  !                                                   !
  !               Key: Each character in              !
  !                    the boxes illustrates an MTA.  !
  !                                                   !
  !                    x: TP0/RFC1006/TCP WEP         !
  !                    w: TP4/CLNP WEP                !
  !                    z: TP0/CONS/X.25 WEP           !
  !                    o: MTA                         !
  -----------------------------------------------------

              Figure 1: A Deployment Scenario





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PRMD A has three WEPs which collectively provide support for
the TP0/CONS/X.25, TP0/RFC1006, and TP4/CLNS stacks[1] Thus,
PRMD  A is reachable via these stacks. However, since PRMD B
only supports the TP0/CONS/X.25 stack, it is  not  reachable
from the TP0/RFC 1006 or the TP4/CLNS stack. PRMD C supports
TP0/RFC1006 and TP4/CLNS. Since PRMD B and  PRMD  C  do  not
share  a common stack, how is a message from PRMD C to reach
a recipient in PRMD B?

One solution to this problem  is  to  require  that  PRMD  B
implement  a  stack  in common with PRMD C. However this may
not be a politically acceptable answer to PRMD B.

Another solution is to implement a transport service  bridge
(TSB)  between TP0/RFC 1006 in PRMD C to TP0/CONS in PRMD B.
This will solve the problem for PRMD C and B.  However,  the
lack  of coordinated deployment of TSB technology makes this
answer alone unacceptable on an international scale.

The solution to this problem  is  to  define  a  coordinated
mechanism  that allows PRMD B to advertise to the world that
it has made a bilateral agreement with  PRMD  A  to  support
reachability to PRMD B from the TP0/RFC 1006 stack.

This solution does not require that every MTA or MD directly
support  all  stacks. However, it is a requirement that if a
particular stack is not directly supported by an MD, the  MD
will  need  to make bilateral agreements with other MD(s) in
order to assure that connectivity from that stack is  avail-
able.

Thus, in the case of Figure 1, PRMD B can make  a  bilateral
agreement  with  PRMD  A  which provides for PRMD A to relay
messages which arrive on either the TP4/CLNP  stack  or  the
TP0/RFC 1006 stack to PRMD B using the TP0/CONS stack.

The policies described in [1] define  this  general  purpose
solution.  It is a requirement that all MDs follow the rules
and policies defined by [1].



3.  Description of GO-MHS Community Policies

A GO-MD is a Management Domain in the GO-MHS Community.




   [1] Note: it is acceptable for a single  WEP  to  support
more  than  one  stack.  Three WEPs are shown in this figure
for clarity.




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The policies described in this section constitute a  minimum
set  of  common  policies  for GO-MDs. They are specified to
ensure interoperability between

    - all GO-MDs.
    - all GO-MDs and the RFC-822 mail service (SMTP).
    - all GO-MDs and other X.400 service providers.




3.1.  X.400 Address Registration

An O/R address is a descriptive name for a UA that has  cer-
tain  characteristics  that  help  the  Service Providers to
locate the UA. Every O/R address is an  O/R  name,  but  not
every  O/R name is an O/R address. This is explained in [5],
chapter 3.1.

Uniqueness of X.400 addresses shall be used to  ensure  end-
user connectivity.

Mailboxes shall be addressed according to the description of
O/R  names,  Form 1, Variant 1 (see [5], chapter 3.3.2). The
attributes shall be regarded as a hierarchy of

    Country name (C)
    Administration domain name (ADMD)
    [Private domain name] (PRMD)
    [Organization name] (O)
    [Organizational Unit Names] (OUs)
    [Personal name] (PN)
    [Domain-defined attributes] (DDAs)

Attributes enclosed in  square  brackets  are  optional.  At
least one of PRMD, O, OU and PN names shall be present in an
O/R address.

In general a subordinate address  element  shall  be  unique
within  the  scope  of  its immediately superior element. An
exception is PRMD, see  section  3.1.3.  There  shall  exist
registration authorities for each level, or mechanisms shall
be available to ensure such uniqueness.


3.1.1.  Country (C)

The values of the  top  level  element,  Country,  shall  be
defined  by  the set of two letter country codes, or numeric
country codes in ISO 3166.





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3.1.2.  Administration Management Domain (ADMD)

The values of the ADMD  field  are  decided  on  a  national
basis.  Every  national decision made within the GO-MHS com-
munity shall be supported by a GO-MD.


3.1.3.  Private Management Domain (PRMD)

The PRMD values should be unique within a country.


3.1.4.  Organization (O)

Organization values shall be unique within  the  context  of
the subscribed PRMD or ADMD if there is no PRMD. For clarif-
ication: The following situation is legal:

    1) C=FI; ADMD=FUMAIL; O=FUNET.
    2) C=FI; ADMD=FUMAIL; PRMD=NOKIA; O=FUNET.

In this case 1) and 2) are different addreses. (Note that 2)
at  this point is a hypotethical address). O=FUNET is a sub-
scriber both at ADMD=FUMAIL, 1), and at PRMD=NOKIA, 2).


3.1.5.  Organizational Units (OUs)

If used, a unique hierarchy of OUs shall be implemented. The
top  level  OU is unique within the scope of the immediately
superior address element (i.e., Organization, PRMD or ADMD).
Use of multiple OUs may be confusing.


3.1.6.  Given Name, Initials, Surname (G I S)

Each Organization can define its own Given-names,  Initials,
and  Surnames  to  be  used  within the Organization. In the
cases when Surnames are not unique within an O  or  OU,  the
Given-name  and/or  Initial  shall  be  used to identify the
Originator/Recipient. In the rare cases when more  than  one
user  would  have  the same combination of G, I, S under the
same O and/or OUs, each organization is free to find a prac-
tical  solution,  and  provide  the  users  with  unique O/R
addresses.

Either one of Given-name or Initials  should  be  used,  not
both.  Periods shall not be used in Initials.

To avoid problems with the mapping of the X.400 addresses to
RFC-822  addresses, the following rules might be used. ADMD,
PRMD, O, and OU values should consist  of  characters  drawn
from  the alphabet (A-Z), digits (0-9), and minus.  Blank or


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Space characters should be avoided.  No distinction is  made
between  upper  and lower case. The last character shall not
be a minus sign or period.  The first  character  should  be
either a letter or a digit (see [6], [7]).


3.1.7.  Domain Defined Attributes (DDAs)

The GO-MHS Community shall allow the use of  domain  defined
attributes. Note: Support for DDAs is mandatory in the func-
tional profiles, and all software must  upgrade  to  support
DDAs.  The following DDAs shall be supported by a GO-MD:

    "RFC-822" - defined in [3].


The following DDAs should be supported by a GO-MD:

    "COMMON" - defined in [2].



3.2.  X.400 88 -> 84 Downgrading

The requirements in [2] should be implemented in GO-MDs


3.3.  X.400 / RFC-822 address mapping

All GO-MHS Community end-users shall be reachable  from  all
end-users  in  the  RFC-822  mail  service  in  the Internet
(SMTP), and vice versa.

The address mapping issue is split into two parts:

    1) Specification of RFC-822 addresses seen from the X.400 world.
    2) Specification of X.400 addresses seen from the RFC-822 world.

The mapping of X.400 and RFC-822  addresses  shall  be  per-
formed according to [3].


3.3.1.  Specification of RFC-822  Addresses  seen  from  the
X.400 World

Two scenarios are described:

    A. The RFC-822 end-user belongs to an organization with no defined X.400
       standard attribute address space.
    B. The RFC-822 end-user belongs to an organization with a defined X.400
       standard attribute address space.




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Organizations belong to scenario B if their X.400  addresses
are registered according to the requirements in section 3.1.


3.3.1.1.  An  Organization  with  a  defined  X.400  Address
Space

An RFC-822 address for an  RFC-822  mail  user  in  such  an
organization  shall be in the same address space as a normal
X.400 address for X.400  users  in  the  same  organization.
RFC-822  addresses  and X.400 addresses are thus sharing the
same address space. Example:

University of Wisconsin-Madison is  registered  under  C=US;
ADMD=Internet;  PRMD=XNREN;  with  O=UW-Madison and they are
using OU=cs to address end-users in the  CS-department.  The
RFC-822  address  for RFC-822 mail users in the same depart-
ment is: user@cs.wisc.edu.

An X.400 user in the GO-MHS Community will address the  RFC-
822 mail user at the CS-department with the X.400 address:

    C=US; ADMD=Internet; PRMD=xnren; O=UW-Madison; OU=cs; S=user;


This is the same address space as is  used  for  X.400  end-
users in the same department.


3.3.1.2.  An Organization  with  no  defined  X.400  Address
Space

RFC-822 addresses shall  be  expressed  using  X.400  domain
defined  attributes.   The mechanism used to define the RFC-
822 recipient will vary on a per-country basis.

For example, in the U.S., a special PRMD named "Internet" is
defined   to   facilitate   the   specification  of  RFC-822
addresses.  An X.400 user can address an  RFC-822  recipient
in the U.S. by constructing an X.400 address such as:

    C=us; ADMD=Internet; PRMD=Internet; DD.RFC-822=user(a)some.place.edu;


The first part of this address:

    C=us; ADMD=Internet; PRMD=Internet;


denotes the U.S. portion of the Internet community and not a
specific "gateway". The 2nd part:

    DD.RFC-822=user(a)some.place.edu


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is the RFC-822 address of the RFC-822 mail user  after  sub-
stitution  of non-printable characters according to [3]. The
RFC-822 address is placed in an X.400 Domain Defined  Attri-
bute of type RFC-822 (DD.RFC-822).

Each country is free to choose its own  method  of  defining
the  RFC-822 community.  For example in Italy, an X.400 user
would refer to an RFC-822 user as:

    C=IT; ADMD=MASTER400; DD.RFC-822=user(a)some.place.it


In the UK, an X.400 user would refer to an RFC-822 user as:

    C=GB; ADMD= ; PRMD=UK.AC; O=MHS-relay; DD.RFC-822=user(a)some.place.uk



3.3.2.  Specification of X.400 Addresses seen from the  RFC-
822 World

If an X.400  organization  has  a  defined  RFC-822  address
space,  RFC-822  users  will  be able to address X.400 reci-
pients  in  RFC-822/Internet  terms.  This  means  that  the
address  of  the X.400 user, seen from an RFC-822 user, will
generally be of the form:

    Firstname.Lastname@some.place.edu


where the some.place.edu is a registered Internet domain.

This implies the necessity of maintaining  and  distributing
address  mapping  tables to all participating RFC-1327 gate-
ways. The  mapping  tables  shall  be  globally  consistent.
Effective  mapping table coordination procedures are needed.
The procedures defined in [4] shall be followed.

If an organization does not have a defined  RFC-822  address
space,  an escape mapping (defined in [3]) shall be used. In
this case, the address of the X.400 user, seen from an  RFC-
822 user, will be of the form:

    "/G=Firstname/S=Lastname/O=org name/PRMD=foo/ADMD=bar/C=us/"@
                                    some.gateway.edu


Note that [7] specifies that quoted left-hand side addresses
must  be  supported  and that these addresses may be greater
than 80 characters long.

This escape mapping shall also be used for  X.400  addresses
which do not map cleanly to RFC-822 addresses.


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It is recommended that an organization with no defined  RFC-
822  address  space,  should register RFC-822 domains at the
appropriate registration entity for such registrations. This
will  minimize  the  number  of addresses which must use the
escape mapping.

If the escape mapping is not used, RFC-822  users  will  not
see  the  difference between an Internet RFC-822 address and
an address in the GO-MHS Community.  For example:

The X.400 address:

    C=us; ADMD=ATTMail; PRMD=CDC; O=CPG; S=Lastname; G=Firstname;


will from an RFC-822 user look like:

    Firstname.Lastname@cpg.cdc.com



3.4.  Routing Policy

To facilitate routing in  the  GO-MHS  Community  before  an
X.500  infrastructure is deployed, the following two tables,
an MTA table and a Domain table, are defined.  These  tables
are  formally  defined  in  [1].  The use of these tables is
necessary to solve the routing crisis that is present today.
However,  this  is a temporary solution that will eventually
be replaced by the use of X.500.

The MTA table will define  the  names  of  well  known  MTAs
(WEPs) and their associated connection data including selec-
tor values, NSAP addresses, supported protocol  stacks,  and
supported X.400 protocol version(s).

Each entry in  the  Domain  table  consists  of  a  sub-tree
hierarchy  of  an  X.400 address, followed by a list of MTAs
which are willing to accept mail for the address or  provide
a  relay  service  for  it. Each MTA name will be associated
with a priority value. Collectively, the list of  MTA  names
in  the  Domain  table make the given address reachable from
all protocol stacks. In addition, the list of MTAs may  pro-
vide  redundant  paths  to the address, so in this case, the
priority value indicates the preferred  path,  or  the  pre-
ferred order in which alternative routes should be tried.

The MTA and Domain  tables  are  coordinated  by  the  group
specified  in  the  Community  document.  The procedures for
table  information  gathering  and  distribution,  are   for
further study.




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3.5.  Minimum Statistics/Accounting

The following are not required for all MTAs. The information
is  provided as guidelines for MTA managers, and is based on
work in [8].  This is helpful for observing service use  and
evaluating service performance.

This section defines the data which should be kept  by  each
MTA.  There are no constraints on the encoding used to store
the data (i.e., format).

For each  message/report  passing  the  MTA,  the  following
information should be collected.

The following fields should be collected.

    Date
    Time
    Priority
    Local MTA Name
    Size


The following fields are conditionally collected.

    From MTA Name (fm)
    To MTA Name (tm)
    Delta Time (dt)
    Message-id (id)

At least one of 'fm' and 'tm' should be present.  If one  of
'fm'  and  'tm'  is  not present, 'id' should be present. If
both 'fm' and 'tm' are  present,  then  'dt'  indicates  the
number  of  minutes that the message was delayed in the MTA.
If 'id' cannot be mapped locally because of  log  file  for-
mats,  'id'  is  not  present  and every message creates two
lines: one with 'fm' empty and one with 'tm' empty. In  this
case, 'date' and 'time' in the first line represent the date
and time the message entered the MTA.  In the  second  line,
they represent the date and time the message left the MTA.

The following fields are optionally collected.

    From Domain (fd)
    To Domain (td)

For route tracing, 'fd' and 'td' are useful. They  represent
X.400  OU's,  O,  PRMD, ADMD and C and may be supplied up to
any level of detail.






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4.  Community Document

For the GO-MHS community there will exist one single COMMUN-
ITY document containing basic information as defined in [1].
First the contact information for the  central  coordination
point  can be found together with the addresses for the file
server where all the documents are  stored.  It  also  lists
network  names  and  stacks to be used in the WEP and DOMAIN
documents. The GO-MHS community must agree on its own set of
mandatory and optional networks and stacks.













































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                         References

[1]  U. Eppenberger, Routing coordination for an X.400  MHS-
     service  within  a  multi  protocol / multi network en-
     vironment, IETF  Internet  Draft,  "draft-ietf-x400ops-
     mhs-service-04.txt".



[2]  S.E. Hardcastle-Kille: X.400 1988 to 1984  downgrading,
     RFC 1328, May 1992.



[3]  S.E. Hardcastle-Kille: Mapping  between  X.400(1988)  /
     ISO 10021 and RFC 822, RFC 1327, May 1992.



[4]  Urs Eppenberger, Jeroen Houttuin, Paul Klarenberg,  Jim
     Romaguera:  Co-ordination Procedures for RFC 1327 Gate-
     ways, (IETF Internet Draft).



[5]  <ref. CCITT Red Book, X.400>



[6]  K. Harrenstien, et al. DOD Internet Host Table Specifi-
     cation.  Request for Comments 952, October 1985.



[7]  R. Braden. Requirements for Internet Hosts --  Applica-
     tion  and  Support.  Request for Comments 1123, October
     1989.



[8]  The COSINE MHS Project Team, "Requirements for A  Final
     Format Of Traffic Statistics"



[9]  C. Allan  Cargille,  Postmaster  Convention  for  X.400
     Operations,  IETF  Internet Draft, "draft-ietf-x400ops-
     postmaster-00.txt"







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