Network Working Group C. Allocchio
Request for Comments: 1405 I.N.F.N. - Italy
January 1993

Mapping between X.400(1984/1988) and Mail-11 (DECnet mail)

Status of this Memo

This memo defines an EXPerimental Protocol for the Internet
community. Discussion and suggestions for improvement are requested.
Please refer to the current edition of the "IAB Official Protocol
Standards" for the standardization state and status of this protocol.
Distribution of this memo is unlimited.

Abstract

This document describes a set of mappings which will enable inter
working between systems operating the CCITT X.400 ( 1984 / 1988 )
Recommendations on Message Handling Systems, and systems running the
Mail-11 (also known as DECnet mail) protocol. The specifications are
valid within DECnet Phase IV addressing and routing scheme.

The complete scenario of X.400 / RFC822 / Mail-11 is also considered,
in order to cover the possible complex cases arising in multiple
gateway translations.

This document covers mainly the O/R address to DECnet from/to address
mapping (and vice versa); other mappings are based on RFC1327 and
its eventual future updates.

This is a combined effort of COSINE S2.2, the RARE MSG Working Group,
and the IETF X.400 Ops Working Group.

Chapter 1 - IntrodUCtion

1.1. X.400

The standard referred shortly into this document as "X.400" relates
to the CCITT 1984 and 1988 X.400 Series Recommendations covering the
Message Oriented Text Interchange Service (MOTIS). This document
covers the Inter Personal Messaging System (IPMS) only.

1.2. Mail-11

Mail-11, also known as DECnet mail and often improperly referred as
VMSmail, is the proprietary protocol implemented by Digital Equipment
Corporation (DEC) to establish a real-time text messaging system

among systems implementing the DECnet Phase IV networking protocols.

1.3. RFC822

RFC822 was defined as a standard for personal messaging systems
within the DARPA Internet and is now diffused on top of many
different message transfer protocols, like SMTP, UUCP, BITNET, JNT
Grey Book, CSnet. Its mapping with X.400 is fully described in
RFC1327. In this document we will try to consider its relations with
Mail-11, too.

1.4. The user community

The community using X.400 messaging system is currently growing in
the whole world, but there is still a number of very large
communities using Mail-11 based messaging systems willing to
communicate easily with X.400 based Message Handling Systems. Among
these large DECnet based networks we can include the High Energy
Physics network (HEPnet) and the Space Physics Analysis Network
(SPAN).

These DECnet communities will in the future possibly migrate to
DECnet Phase V (DECnet-OSI) protocols, converting thus their
messaging systems to OSI specifications, i.e., merging into the X.400
MHS; however the transition period could be long, and there could
always be some DECnet Phase IV communities around.

For these reasons a set of mapping rules covering conversion between
Mail-11 and X.400 is described in this document.

This document also covers the case of Mail-11 systems implementing
the "foreign mail protocol" allowing Mail-11 to interface other mail
systems, including RFC822 based system.

Chapter 2 - Message Elements

2.1. Service Elements

Mail-11 protocol offers a very restricted set of elements composing a
Inter Personal Message (IPM), whereas X.400 specifications support a
complex and large amount of service elements. Considering the case
where a message is relayed between two X.400 MHS via a DECnet network
this could result in a nearly complete loss of information. To
minimise this inconvenience most of X.400 service elements will be
mapped into Mail-11 text body parts. To consider also the case when a
message originates from a network implementing RFC822 protocols and
is relayed via Mail-11 to and X.400 MHS, the applied mapping from
X.400 service elements into Mail-11 text body part the rules

specified in RFC1327 and their updates will be used, producing an
RFC822-like header.

2.2. Mail-11 service elements

All envelope (P1) and header (P2) Mail-11 service elements are
supported in the conversion to X.400. Note that Mail-11 P1 is solely
composed by P1.From and P1.To, and any other Mail-11 element belongs
to Mail-11 P2:

- P1.From
maps to P1.Originator

- P1.To
maps to P1.Primary Recipient

- P2.From
maps to P2.Originator

- P2.To
maps to P2.Primary Recipient

- Cc
maps to P2.Copy Recipient

- Date
maps to Submission Time Stamp

- Subj
maps to Subject

Any eventual RFC822-like text header in Mail-11 body part will be
interpreted as specified into RFC1327 and its updates.

2.3. X.400 service elements

The following X.400 service elements are supported directly into
Mail-11 conversion:

- P1.Originator
maps to P1.'From'

- P1.Primary Recipients
maps to P1.'To'

- P2.Originator
maps to P2.'From'

- P2.Primary Recipients
maps to P2.'To'

- Copy Recipients
maps to 'Cc'

- Submission Time Stamp
maps to 'date'

- Subject
maps to 'Subj'

The following X.400 service element is partially supported into
Mail-11 conversion:

- Blind Copy Recipient
to ensure the required privacy, when a message contains
a BCC address, the following actions occurs:
- a new message is created, containing the body parts;
- a new envelope is added to the new message, containing
the originator and the BCC recipient addresses only;
- a note is added to the message informing the BCC
recipient about the fact that the message was a BCC;
- the new message is delivered separately;
- a note is added to the message delivered to TO and CC
recipients informing them about the fact that there
were some BCC recipients, too.

Any other X.400 service element support is done accordingly to
RFC1327 including the mapped element into the RFC822-like header into
Mail-11 body part.

Chapter 3 - Basic Mappings

The basic mappings indicated in RFC1327 and its updates should be
fully used.

Chapter 4 - Addressing

4.1. Mail-11 addressing

Mail-11 addressing can vary from a very simple case up to complex
ones, if there are other Mail-11 to "something-else" gateways
involved. In any case a Mail-11 address is an ASCII string composed
of different elements.

4.2. X.400 addressing

On the other hand, An X.400 O/R address is a collection of
attributes, which can anyway be presented as an IA5 textual
representation as defined in chapter 4 of RFC1327.

4.3. Mail-11 address components

Let us start defining the different parts composing a Mail-11
address. We can consider any Mail-11 address as composed by 3 parts:

[[route]::] [[node]::] local-part

where 'route' and 'node' are optional and only 'local-part' is
compulsory.

Here comes a strict definition of these elements

node = *(ALPHA/DIGIT) / *DIGIT / *DIGIT "." *DIGIT

route = *(node "::")

local-part = username / nickname / for-protocol

username = *(ALPHA/DIGIT)

nickname = <printablestring - <" " and HTAB>>

for-protocol = (f-pref f-sep <">f-address<">)

f-pref = *(ALPHA/DIGIT)

f-sep = "%" / "::"

f-address = printablestring / RFC822-address / X400-text-address

X400-text-address = <textual representation of an X.400 O/R addr>

Please note that in x-text-address both the ";" notation and the "/"
notation are equivalent and allowed (see examples in different sect.)

Some examples:

route node local-part
-----------------------------------------------------------
USER47
MYNODE::BETTY
BOSTON::CLUS02::GOOFY1::MARY34
IN%"M.P.Tracy@Dicdum.cc.edu"
UCLA13::MVAX93::MRGATE::"MBOX1::MBX34::MYC3::BOB"
MIAMI2::George.Rosenthal
CCUBVX::VS3100::Jnet%"IAB3425@IBAX23L"
MRGATE::"C=xx::A=bbb::P=ppp::S=Joe"
MAINVX::IN%"path1!path2!user%dom"
GWX400::gw%"C=xx;ADMD=aaa;PRMD=ppp;S=Lee;"
GX409A::x400%"/C=xx/A=aaa/P=ppp/S=Lee"
smtp%"postmast@nodeb.bitnet"
MICKEY::PRFGAT::profs%"NANCY@IBMB"
edu%"HU427BD%CSUNIB@abc.acme.edu"

Chapter 5 - Mapping

5.1. Mapping scheme

DECnet address field is somehow a 'flat land' with some obliged
routes to reach some hidden areas. Thus a truly hierarchical mapping
scheme using mapping tables as suitable for RFC822 is not the
appropriate solution. A fixed set of rules using DDAs support is
defined in order to define the mapping.

Another important ASPect of the problem is the coexistence of many
disjoint DECnet networks, using the same DECnet address space, i.e.,
common X.400 and/or RFC822 mailing system acting as glue to connect
different isolated Mail-11 islands. Thus, to identify uniquely each
DECnet network we must also introduce the concept of 'DECnet network
name', which we will refer shortly as 'net' from now onwards. We
define as 'net' a unique ASCII string identifying the DECnet network
we are connected to. To be more specific, the 'net' element will
identify the DECnet community being served, i.e., it could also
differ from the actual official network name. Aliases are allowed for
the

net = 'HEPnet' the High Energy Physics DECnet network
net = 'SPAN' the Space Physics Analysis Network
net = 'Enet' the Digital Equipment Corporate Network

The need of labelling each DECnet network with its name comes also
from the requirement to implement the 'intelligent' gateway, i.e.,
the gateway which is able to understand its ability to connect

directly to the specified DECnet network, even if the O/R address
specify a path to a different gateway. A more detailed discussion of
the problem is in 5.3 and 5.5.

A registry of 'net' attributes and their correspondent gateways must
also be implemented to insure uniqueness of names. A simple table
coupling 'net' and the gateway address is used, in a syntax similar
to the 'gate' table used in RFC1327. An example:

HEPnet#OU$Cosine-gw.O$@.PRMD$infn.ADMD$garr.C$IT#
SPAN#OU$Cosine-gw.O$@.PRMD$infn.ADMD$garr.C$IT#
SPAN#O$ESRIN1.PRMD$esa.ADMD$Master400.C$it#

Ambiguous left entries are allowed. Gateway implementations could
simply choose among one of them, or try them all in cyclic order to
oBTain better performances.

In order to keep the mapping rules very simple, avoiding the need to
analyse Mail-11 addresses to distinguish the 'route', 'node' and
needed to cover the mapping problem.

5.2. Mail-11 --> X.400

We define the following Domain Defined Attributes to map a Mail-11
address:

DD.Dnet
DD.Mail-11

We thus define the mapping rule

route::node::localpart

maps into

C=xx; ADMD=yyy; PRMD=zzz; O=ooo; OU=uuu; DD.Dnet=net;
DD.Mail-11=route::node::localpart;

with

xx = country code of the gateway performing the conversion
yyy = Admd of the gateway performing the conversion
zzz = Prmd of the gateway performing the conversion
ooo = Organisation of the gateway performing the conversion
uuu = Org. Unit(s) of the gateway performing the conversion
net = name of the DECnet network (e.g., HEPnet, SPAN,...)

('zzz','ooo','uuu' being used or dropped appropriately in order to

identify uniquely within the X.400 MHS the gateway performing the
conversion).

The following defaults also apply:

if 'node' is missing and we are mapping the Mail-11 originator (From)
then 'node' defaults to the DECnet node name of the gateway (gwnode);

if 'node' is missing and we are mapping the Mail-11 recipient (To,
Cc) then 'node' defaults to the DECnet node name of the 'From'
address.

if 'DD.Dnet=net' is missing, then it defaults to a value defined
locally by the gateway: if the gateway is connected to one DECnet
network only, then 'net' will be the name of this unique network; if
the gateway is connected to more than one DECnet network, then the
gateway will establish a 'first choice' DECnet network, and 'net'
will default to this value.

In case 'local-part' contains 'x400-text-address' see also section
6.4.3;

In case 'local-part' contains 'RFC822-address' see also section
6.4.4.

5.2.1. Examples

Let us suppose that:

the DECnet network name (net) is 'HEP';
the DECnet node name of the gateway (gwnode) is 'X4TDEC';
the Country Code of the gateway is 'IT' and its ADMD is 'garr'
(and these two fields are enough to identify uniquely the gateway
within the X.400 MHS).

USER47
C=it; ADMD=garr; DD.Dnet=HEP; DD.Mail-11=X4TDEC::USER47;

MYNODE::BETTY
C=it; ADMD=garr; DD.Dnet=HEP; DD.Mail-11=MYNODE::BETTY;

BOSTON::CLUS02::GOOFY1::MARY34
C=it; ADMD=garr; DD.Dnet=HEP; DD.Mail-11=BOSTON::GOOFY1::MARY34;

UCLA13::MVAX93::MRGATE::"MBOX1::MBX34:MYC3::BOB"
C=it; ADMD=garr; DD.Dnet=HEP;
DD.Mail-11=UCLA13::MVAX93::MRGATE::(q)MBOX1::MBX34::MYC3::BOB(q)

MIAMI2::George.Rosenthal
C=it; ADMD=garr; DD.Dnet=HEP; DD.Mail-11=MIAMI2::George.Rosenthal;

MRGATE::"C=xx::A=bbb::P=ppp::S=Joe"
C=it; ADMD=garr; DD.Dnet=HEP;
DD.Mail-11=X4TDEC::MRGATE::(q)C=xx::A=bbb::P=ppp::S=Joe(q)

MAINVX::In%"path1!path2!user%dom"
C=it; ADMD=garr; DD.Dnet=HEP;
DD.Mail-11=MAINVX::In(p)(q)path1(b)path2(b)user(p)dom(q)

5.3. X.400 encoding of Mail-11 --> Mail-11

In order to assure path reversibility in case of multiple Mail-
11/X.400 gateway crossing we must distinguish two cases:

- DD.Dnet=net is known to the gateway as one of the DECnet networks
it is connected to. In this case the mapping is trivial:

C=xx; ADMD=yyy; PRMD=zzz; O=ooo; OU=uuu; DD.Dnet=net;
DD.Mail-11=route::node::localpart;

(see sect. 5.2 for explication of 'xx','yyy','zzz','ooo','uuu','net')

maps into

route::node::localpart

- DD.Dnet=net is NOT known to the gateway as one of the DECnet
networks it is connected to. In this case the mapping rule
described into section 5.4 apply:

C=xx; ADMD=yyy; PRMD=www; DD.Dnet=net;
DD.Mail-11=route::node::localpart;

maps into

gwnode::gw%"C=xx;ADMD=yyy;PRMD=www;DD.Dnet=net;
DD.Mail-11=route::node::localpart;"

5.3.1. Examples

Let us suppose that:

the DECnet network name (net) is 'HEP';
the DECnet node name of the gateway (gwnode) is 'X4TDEC';
the Country Code of the gateway is 'IT' and its ADMD is 'garr';
(and these two fields are enough to identify uniquely the gateway

within the X.400 MHS).

C=it; ADMD=garr; DD.Dnet=HEP;
DD.Mail-11=X4TDEC::MRGATE::(q)C=ab::A=dsa::P=qwty::OU=mie::S=Cly(q)
MRGATE::"C=ab::A=dsa::P=qwty::OU=mie::S=Cly"

C=it; ADMD=garr; DD.Dnet=EASYNET; DD.Mail-11=ROM01::CARLO;
X4TDEC::gw%"C=it;ADMD=garr;DD.Dnet=EASYNET;
DD.Mail-11=ROM01::CARLO;"

(in the above example 'EASYNET' is supposed to be not connected to
our gateway located on X4TDEC DECnet node).

5.4. X.400 --> Mail-11

The mapping of an X.400 O/R address into Mail-11 is done encoding the
various attributes into the X400-text-address as defined in chapter 4
of RFC1327, and including this as 'f-address'. A 'f-pref' and a the
DECnet node name of the gateway.

Thus

x400-text-address

will be encoded like

gwnode::gw%"x400-text-address"

having spaces dividing attributes as optional.

5.4.1. Example

Let us suppose that:

the DECnet node name of the gateway (gwnode) is 'X4TDEC';

Thus

C=gb; ADMD=Gold 400; PRMD=AC.UK; O=ucl; OU=cs; G=Jim; S=Clay;

will be encoded like

X4TDEC::gw%"/C=gb/A=Gold 400/P=AC.UK/O=ucl/OU=cs/G=Jim/S=Clay"

or its equivalent with the ";" notation

X4TDEC::gw%"C=gb;ADMD=Gold 400;PRMD=AC.UK;O=ucl;OU=cs;G=Jim;S=Clay;"

5.5. Mail-11 encoding of X.400 --> X.400

It can happened that Mail-11 is used to relay messages between X.400
systems; this will mean multiple X.400/Mail-11 gateway crossing and
we will encounter Mail-11 addresses containing embedded X.400
informations. In order to assure path reversibility we must then
distinguish two cases:

- the embedded X.400 address belongs to a domain whose naming and
routing rules are known to the global X.400 MHS. In this case the
mapping is trivial:

route::gwnode::gw%"x400-text-address"

maps into

x400-text-address

'route' and 'gwnode' are mapped into X.400 Trace service elements.

- the encoded X.400 domain does not belong to the global X.400 name
space. In this case the mapping rule described into section 5.2
apply:

route::gwnode::gw%"x400-text-address"

maps into

C=xx; ADMD=yyy; DD.Dnet=net;
DD.Mail-11=route::gwnode::gw(p)(q)x400-text-address(q);

The latter case is deprecated and must be regarded as a possible
temporary solution only, while waiting to include into the global
X.400 MHS also this domain.

5.5.1. Examples

Let us suppose that:

the DECnet network name (net) is 'HEP';
the DECnet node name of the gateway (gwnode) is 'X4TDEC';
the Country Code of the gateway is 'IT' and its ADMD is 'garr';
(and these two fields are enough to identify uniquely the gateway
within the X.400 MHS).

X4TDEC::gw%"C=fr;ADMD=atlas;PRMD=ifip;O=poly;S=Moreau;"
C=fr; ADMD=atlas; PRMD=ifip; O=poly; S=Moreau;

X4TDEC::gw%"C=zz;ADMD= ;PRMD=Botwa;O=Miner;S=Chiuaw;"
C=it; ADMD=garr; DD.Dnet=HEP;
DD.Mail-11=X4TDEC::gw(p)(q)C=zz;ADMD= ;
PRMD=Botwa;O=Miner;S=Chiuaw;(q)

(in the above example C=zz is unknown to the global X.400 MHS)

Chapter 6 - Complex mapping

6.1. The protocol triangle

The bilateral mappings described in chapter 5 must be extended in
order to cover also the case in which also RFC822 addressing is
involved, and the following triangular situation occurs:

x.400
/
/
/
Mail-11----RFC822

The X.400 - RFC822 side is fully covered by RFC1327, and the previous
chapters in this document cover the Mail-11 - X.400 side.

Currently a number of implementations also perform the mapping along
the Mail-11 - RFC822 side. The most important among these de facto
standards are discussed in Appendix A, jointly with a Mail-11 -
RFC822 mapping scheme which covers this side of the triangle.

6.2. RFC822 mapped in Mail-11

The 'RFC822-address' is usually included in 'local-part' as

route::gwnode::gw%"rfc822-address"

an example

NVXA23::SMTPGW::in%"M.T.Rose@CS.UCLA.edu"

6.3. Mail-11 mapped in RFC822

There are different styles in mapping a Mail-11 address in RFC822
let's have a short summary.

- Mail-11 address encoded in "Left Hand Side" (LHS) of RFC822
address, using "%" syntax or "::" syntax;

route::node::localpart

maps to

localpart%node%route@gw-domains

or

"route::node::localpart"@gw-domains

where 'gw-domains' identify uniquely the Mail-11 / RFC822 gateway.

- Mail-11 address maps partly to LHS and partly to 'domain' part of
RFC822 address:

node::localpart

maps to

localpart@node.gw-domains

- Mail-11 address is completely hidden by a mapping table / Directory
and the resultant RFC822 address contains no trace at all of the
original address.

As you could notice, in any of the quoted cases the resultant RFC822
address is not distinguishable from a genuine RFC822 address.

6.4. Multiple conversions

Let us now examine briefly the possible situations which involve
multiple conversions, having one protocol as a relay between the
other two. This summary suggest some possible enhanced solutions to
avoid heavy and unduly mappings, but the 'step by step' approach,
considering blindly one conversion as disjointed to the other, as
described in the previous sections, can always be used.

6.4.1. X.400 --> RFC822 --> Mail-11

We apply the RFC1327 rules to the first step, obtaining an RFC822
address which can be mapped in Mail-11 using the 'f-address' field,
as described in section 6.2.

an example:

C=gb; ADMD=Gold 400; PRMD=AC.UK; O=UCL; OU=cs; G=Jim; S=Clay;

maps accordingly to RFC1327 to

Jim.Clay@cs.UCL.AC.UK

and finally becomes

SMTPGW::In%"Jim.Clay@cs.UCL.AC.UK"

where 'SMTPGW' is the DECnet node name of the machine running the
RFC822 to Mail-11 gateway.

6.4.2. Mail-11 --> RFC822 --> X.400

Some of the possible mapping described in section 6.3 apply to the
Mail-11 address, hiding completely its origin. The RFC1327 apply on
the last step.

an example:

RELAY::MYNODE::BETTY

could map into RFC822 as

BETTY%MYNODE@RELAY.dnet.gw1.it

and accordingly to RFC1327

C=it; A=garr; P=dom1; O=gw1; OU=RELAY; S=BETTY(p)MYNODE;

where 'dnet.gw1.it' is the domain of the machine running the Mail-11
to RFC822 gateway.

6.4.3. X.400 --> Mail-11 --> RFC822

The X.400 address is stored into Mail-11 'f-address' element as
described in sections 5.3 and 5.4; then if the Mail-11 to RFC822
gateway is able to understand the presence of a 'x400-text-address'
into the Mail-11 address, then it applies RFC1327 to it, and encodes
header. Otherwise it applies the rules described in 6.3

an example:

C=gb; ADMD=Gold 400; PRMD=AC.UK; O=UCL; OU=cs; G=Jim; S=Clay;

will be encoded like

X4TDEC::gw%"/C=gb/A=Gold 400/P=AC.UK/O=UCL/OU=cs/G=Jim/S=Clay"

If the Mail-11 to RFC822 gateway recognise the x400-text-address,
then the address becomes, accordingly to RFC1327

Jim.Clay@cs.UCL.AC.UK

and the following RFC822 header line is added

Received: from X4TDEC with DECnet (Mail-11) on xx-xxx-xxxx.

Otherwise one of the dumb rules could produce

gw%"/C=gb/A=Gold 400/P=AC.UK/O=UCL/OU=cs/G=Jim/S=Clay"@X4TDEC.doms

6.4.4. RFC822 --> Mail-11 --> X.400

The RFC822 address is encoded in Mail-11 f-address element as
described in sect. 6.2; then if the Mail-11 to X.400 gateway is able
to understand the presence of an 'RFC822-address' into the Mail-11
address, then it applies RFC1327 to it, and encodes 'route' and
applies the rules described in 5.2 and 5.5.

an example:

Jim.Clay@cs.UCL.AC.UK

will be encoded like

SMTPGW::In%"Jim.Clay@cs.UCL.AC.UK"

If the Mail-11 to X.400 gateway recognise the RFC822-address, then
the address becomes, accordingly to RFC1327

C=gb; ADMD=Gold 400; PRMD=AC.UK; O=UCL; OU=cs; G=Jim; S=Clay;

and a 'trace' record is added into the X.400 P1 data, stating that a
node named SMTPGW was crossed.

Otherwise dumb rule produces

C=it; ADMD=garr; DD.Dnet=HEP;
DD.Mail-11=SMTPGW::In(p)(q)Jim.Clay(a)cs.UCL.AC.UK(q)

6.4.5. RFC822 --> X.400 --> Mail-11

We apply RFC1327 to the first conversion, obtaining an X.400 address.
Then the rules described in sections 5.3 and 5.4 are used to store
the X.400 address as 'x400-text-address' into the Mail-11

an example:

Jim.Clay@cs.UCL.AC.UK

maps accordingly to RFC1327 to

C=gb; ADMD=Gold 400; PRMD=AC.UK; O=UCL; OU=cs; G=Jim; S=Clay;

and finally becomes

SMTPGW::gw%"/C=gb/A=Gold 400/P=AC.UK/O=UCL/OU=cs/G=Jim/S=Clay"

where 'SMTPGW' is the DECnet node name of the machine running the
X.400 to Mail-11 gateway.

6.4.6. Mail-11 --> X.400 --> RFC822

The Mail-11 address is encoded as specified in sections 5.2 and 5.5;
then RFC1327 is used to convert the address in RFC822.

an example:

RELAY::MYNODE::BETTY

maps into X.400 as

C=it; ADMD=garr; DD.Dnet=HEP; DD.Mail-11=RELAY::MYNODE::BETTY;

and accordingly to RFC1327

"/C=it/A=garr/DD.Dnet=HEP/DD.Mail-11=RELAY::MYNODE::BETTY"@gw2.it

where 'gw2.it' is the domain of the machine running the RFC1327
gateway.

Appendix A Mail-11 - RFC822 mapping

A.1 Introduction

The implementation of a Mail-11 - RFC822 gateway was faced by many
software developers independently, and was included in many mail
products which were running on both VAX/VMS and UNIX systems. As
there was not a unique standard mapping way, the implementations
resulted into a number of possible variant methods to map a Mail-11
address into an RFC822 one. Some of these products became then
largely widespread, starting to create a number of de facto mapping
methods.

In this small appendix some sort of standardisation of the mapping
problem is considered, trying to be compatible with the existing
installed software. We must also remind that, in some cases, only
simple Mail-11 addresses could be mapped into RFC822, having complex
ones producing all sort of quite strange results.

On the other hand, the mapping of an RFC822 address in Mail-11 was
quite straightforward, resulting in a common definition which uses
"Mail-11 foreign mail protocol" to design an RFC822 address:

[[node::][node::]...]prot%"rfc-822-address"

or

[node::][node::]...]::"rfc-822-address"

A.2 De facto implementations

A considerable number of de-facto implementations of Mail-11/RFC822
gateways is existing. As said in the introduction, the mapping of
RFC822 addresses in Mail-11 is accomplished using the foreign mail
protocol syntax and is thus unique.

On the other hand, Mail-11 addresses are encoded in RFC822 syntax in
various ways. Here are the most common ones:

a) "node::user"@gateway-address
b) user%node@gateway-address
c) user@node.decnet.domains
d) user%node.dnet@gateway-address

Let's have a quick look to these different choices.

a - This form simply encloses as quoted Left Hand Side string the
original Mail-11 address into the RFC822 address of the
Mail-11/RFC822 gateway. This method is fully conformant with
RFC822 syntax, and the Mail-11 address is left untouched; thus
no encoding rules need to applied to it.

b - As one will immediately notice, this form has nothing in it
indicating the address is a Mail-11 one; this makes the encoding
indistinguishable from a similar encoding of RSCS (BITnet)
addresses used by some IBM VM Mailer systems. It should thus be
deprecated.

c - In this case a sort of 'reserved Word' (decnet) embedded into
the address itself identifies the presence of a Mail-11 original
address preceding it. The decoding is possible, dropping
'domains' and extracting 'user' and 'node' parts. However complex
Mail-11 addresses cannot be mapped properly in this syntax, and
there is no specific rule for adding the 'domains' part of the
address.

d - In this case again there is a 'reserved word' (dnet) which make
possible the identification of the original Mail-11 address;
'gateway-address' points to the Mail-11/RFC822 gateway and 'node'
and 'user' information can be easily drawn from the address.
However complex Mail-11 addresses cannot be embedded easily into
this syntax.

A.3 Recommended mappings

From the examples seen in the previous paragraphs we can derive a
canonical form for representing the mapping between Mail-11 and
RFC822.

A3.1 RFC822 mapped in Mail-11

The mapping of an RFC822 address in Mail-11 is straightforward, using
the "Mail-11 foreign mail protocol" syntax. The two possible variants
are:

[[node::][node::]...]prot%"rfc-822-address"

or

[node::][node::]...]::"rfc-822-address"

A3.2 Mail-11 mapped in RFC822

RFC822 foresee a canonical form for representing non-RFC822
addresses: put the foreign address in local part (Left Hand Side,
LHS) is a form as similar as possible to its original syntax. Thus
the suggested mapping is:

"Mail-11-address"@gateway-address

This format assures also the return path via the appropriate gateway.

A.4 Conclusions

A standard way of mapping Mail-11 addresses into RFC822 and vice
versa is feasible. A suggestion is thus made to unify all existing
and future implementations. It should be noted, however, that there
is no way to specify in these mappings the name of the decnet
community owning the encoded address, as it was done for X.400, thus
the implementation of the 'intelligent' gateway in this case is
impossible.

Acknowledgements

I wish to thank all those people who read the first draft and
contributed a lot with their useful suggestions to the revision of
this document, in particular RARE WG1 and IETF X.400 ops group
members and S. Hardcastle-Kille.

References

[1] CCITT, "CCITT Recommendations X.400-X.430", Message Handling
Systems: Red Book, October 1984.

[2] CCITT, "CCITT Recommendations X.400-X.420", Message Handling
Systems: Blue Book, November 1988.

[3] Crocker, D., "Standard of the Format of ARPA Internet Text
Messages", STD 11, RFC822, UDel, August 1982.

[4] Kille, S., "Mapping Between X.400 and RFC822", UK Academic
Community Report (MG.19) / RFC987, June 1986.

[5] Kille, S., "Mapping Between X.400(1988) / ISO 10021 and RFC
822", RFC1327, March 1992.

[6] Digital Equipment Corp.;, "VAX/VMS Mail Utility".

[7] Joiner Associates Inc., "Jnet User's Manual".

[8] PMDF User's Guide.

Security Considerations

Security issues are not discussed in this memo.

Author's Address

Claudio Allocchio
Cosine S2.2
Sincrotrone Trieste
Area di Ricerca
Padriciano 99
I 34012 Trieste
Italy

Phone: +39 40 3758523
Fax: +39 40 226338
EMail: Claudio.Allocchio@elettra.Trieste.it
C=it; A=garr; P=Trieste; O=Elettra; S=Allocchio; G=Claudio;