gateway
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... technologies, as conversion will be needed to ensure a smooth service
transition. It is expected that there will be more than one gateway,
and this specification will enable them to behave in a consistent
manner. Note that the term gateway ...
... gateway,
and this specification will enable them to behave in a consistent
manner. Note that the term gateway is used to describe a component
performing the mapping between RFC 822std11(-> 2822prop) and X.400 ...
...
Consistency between gateways is desirable to provide:
...
...
3. It is always a bad idea to lose information as a result of
any transformation. Hence, it is a bad idea for a gateway
to discard information in the objects it processes. This
includes requested services ...
... services which cannot be fully mapped.
4. Mail gateways operate at a level above the layer on which
they perform mappings. This implies that the gateway ...
... gateways operate at a level above the layer on which
they perform mappings. This implies that the gateway shall
not only be cognisant of the semantics of objects at the
...
... not only be cognisant of the semantics of objects at the
gateway level, but also be cognisant of higher level
semantics. If meaningful transformation of the objects that
...
... semantics. If meaningful transformation of the objects that
the gateway operates on is to occur, then the gateway needs
to understand more than the objects themselves.
...
... semantics. If meaningful transformation of the objects that
the gateway operates on is to occur, then the gateway needs
to understand more than the objects themselves.
...
... The Gateway ...
... Given this functional description of the two services, the functional
nature of a gateway can now be considered. It would be elegant to
consider the SMTP (822-MTS ...
... Probes (MTA Service) shall be processed by the gateway, as discussed
in Chapter 5. MTS Messages containing Content Types ...
... Content Types other than those
defined by the IPMS are not mapped by the gateway, and shall be
rejected at the gateway if no other gatewaying procedure is defined.
...
... IPMS are not mapped by the gateway, and shall be
rejected at the gateway if no other gatewaying procedure is defined.
...
... MIME and X.400),
interconnected by multiple gateways. Objects may be transferred
over multiple gateways, and so it is important that gateways ...
... interconnected by multiple gateways. Objects may be transferred
over multiple gateways, and so it is important that gateways
behave in a coherent fashion. MIXER ...
... gateways. Objects may be transferred
over multiple gateways, and so it is important that gateways
behave in a coherent fashion. MIXER is critical ...
...
A gateway is used to connect a closed community to a global mail
network (this could be enforced by connectivity or gateway ...
... gateway is used to connect a closed community to a global mail
network (this could be enforced by connectivity or gateway
authorisation policy). This is a common commercial scenario.
MIXER ...
...
There is also a transition effect. Gateways which are initially
deployed in a strict local scenario situation start to find
...
... start to find
themselves in a global scenario. A common case is ADMD provided
gateways, which are targeted strictly at the local scenario. In
practice they soon start to operate in the global scenario, because
...
... are not customers of the ADMD. At this point, users are hurt by the
restrictions of a local scenario gateway.
...
... Note that conformance to MIXER applies to an instantiation of a
gateway, not just an implementation (although clearly it is critical
that the implementation is capable of being operated in a conformant
...
... Elements - This describes the (end user) services
mapped by a gateway.
3. Basic mappings - This describes some basic notation used in
...
...
This chapter considers the services offered across a gateway built
according to this specification. It gives a view of the
functionality provided by such a gateway ...
... gateway built
according to this specification. It gives a view of the
functionality provided by such a gateway for communication with users
in the opposite domain. This chapter considers service ...
... across an X.400 <-> RFC 822std11(-> 2822prop) gateway. The cases considered are single
transfers across such a gateway, although the problems of multiple
...
... 822std11(-> 2822prop) gateway. The cases considered are single
transfers across such a gateway, although the problems of multiple
crossings are noted where appropriate.
...
... This chapter describes, for each offered service, to what extent it
is supported for a recipient accessed through a gateway. There are
three levels of support:
...
... service is mapped onto a non-standard service on the other side of
the gateway, and this would have lead to support if it had been a
standard service. In many cases, this is equivalent to support. For
...
... User Agent of a message
originated in an X.400 system and transferred across a gateway. The
following standard services (headers ...
... headers. Other elements are provided, in part, by the
gateway as they cannot be provided by RFC 822std11(-> 2822prop).
...
... Physical Delivery Access Unit (PDAU), and so
do not need to be mapped by the gateway.
N/A (reception)
...
... system may freely send an undeliverable message to a local
postmaster). A MIXER gateway has two conformant options. The
first is not to gateway a message requesting prohibition of
...
... MIXER gateway has two conformant options. The
first is not to gateway a message requesting prohibition of
alternate recipient, as this control cannot be guaranteed. This
option supports the service ...
... option supports the service, but may cause unacceptable level of
message rejections. The second is to gateway the message on the
basis that there is no alternate recipient service in RFC 822std11(-> 2822prop) ...
... service shall always be provided by the MTS
prior to the gateway. A new RFC 822std11(-> 2822prop) header ...
... Delivery Notification
Supported. This is performed at the gateway, but may be performed
at the end system if the end system supports NOTARY. Thus, a
notification ...
... at the end system if the end system supports NOTARY. Thus, a
notification is sent by the gateway to the originator.
Delivery ...
... SMTP leve control to prohibit distribution list
expansion. A MIXER gateway has two conformant options. The
first is not to gateway a message requesting DL expansion ...
... MIXER gateway has two conformant options. The
first is not to gateway a message requesting DL expansion
prohibition, as this control cannot be guaranteed. This option
...
... supports the service, but may cause unacceptable level of message
rejections. The second is to gateway the message on the basis that
there is no distribution list service in RFC 822std11(-> 2822prop) ...
... N/A (local). The service request is dealt with at submission
time. Any such request is made available through the gateway by
use of a comment associated with the recipient in question.
...
...
Note:
In practice, a gateway will need to parse various illegal variants
on 822.date-time. In cases where 822.date-time cannot be parsed,
it is recommended that the derived UTCTime ...
... elements of RFC 822std11(-> 2822prop) Headers. A gateway may ignore
this encoding and treat the elements ...
...
A preferred approach is for the gateway to interpret the RFC 1522(-> 2049draft | 2048(-> 4289 | 4288) | 2047draft | 2046draft | 2045draft)
encoding ...
... RFC 1522(-> 2049draft | 2048(-> 4289 | 4288) | 2047draft | 2046draft | 2045draft) is only applied to fields which are "for information only".
A gateway which interprets header elements according to RFC 1522(-> 2049draft | 2048(-> 4289 | 4288) | 2047draft | 2046draft | 2045draft) ...
... Addressing is the most complex aspect of X.400 <-> RFC 822std11(-> 2822prop) gateway
and is therefore given a separate chapter. This chapter also
discusses message identifiers ...
... MIXER
Conformant Global Address Mapping (MCGAM). Gateways conforming to
this specification shall support MCGAMs.
...
... addresses to be referred to
transparently in the remote system, with the choice of gateway being
left to the Message Transfer Service. There are two fundamental
...
... equivalence where there is sufficient co-operation. To be useful,
this equivalence shall be recognised and interpreted in the same way
by all gateways. Therefore, an asymmetrical mapping is defined,
which can be symmetrical where there is appropriate administrative
co-operation. Section 4.3 describes the asymetrical aspects. This
...
... The authority defining an MCGAM may simply use this mapping locally.
This will often be the case in a "local scenario" gateway. Because
of third party addressing ...
... third party addressing, a MIXER gateway will work best with the
maximum number of MCGAMs. Therefore, three mechanisms are defined
to enable publication and exchange of MCGAMs:
...
... Lookup shall be repeated until a value is determined, in order to
maintain consistent gateway operation.
...
...
Where the mapping relates to an envelope address, the gateway shall
non-deliver messages according to the associated MTA's normal timeout
...
... routing within the RFC 822std11(-> 2822prop) world, and will
not be interpreted by the gateway (although they may have identified
the gateway from within the RFC 822std11(-> 2822prop) ...
... not be interpreted by the gateway (although they may have identified
the gateway from within the RFC 822std11(-> 2822prop) world).
...
... The 822.domain associated with the 822.local-part identifies the
gateway from within the RFC 822std11(-> 2822prop) world. This final 822.domain may be
...
... role. RFC 822std11(-> 2822prop) routing to gateways
will usually be set up to facilitate the 822.domain being used for
...
... address is encoded in the 822.local-part and the 822.domain
identifies the gateway to which the message is being sent. This
technique may be used by the RFC 822std11(-> 2822prop) user for any X.400 ...
... manner. The standard domain mechanisms are used to select
appropriate gateways for the corresponding OR Address space. It is
...
... Management Domain to identify a gateway. Thus, this scheme can be
used with varying levels of Management Domain ...
... 1026(-> 2156prop | 1327(-> 2156prop)).
- To ensure that gateways generate consistent addresses.
This is both to help end users, and to generate
...
... the intermediate approach of stripping only domain references
which reference the local gateway are conformant to this
specification.
...
... Where EBNF.known-domain is the longest possible match in the set
of MCGAMs being used by the gateway (described in Section 4.2).
EBNF.domain-syntax is the restricted domain ...
... due to length restrictions. If the limit is exceeded by a
mapping at the MTS level, then the gateway shall reject the
message in question. If this occurs at the IPMS level, then the
...
... mappings will ensure correct routing through X.400 to a gateway
back to RFC 822std11(-> 2822prop).
...
... address
effectively identifies a source route to a gateway from the X.400
side. There are three cases, which are handled differently:
...
... Address
This shall be set up so that errors are returned through the
same gateway. Therefore, the OR Address of the local
...
... may end up anywhere within the X.400 world, and so this
optimisation identifies a gateway appropriate for the RFC
822std11(-> 2822prop) address ...
... address would be routed is used to select an appropriate
gateway.
In this case, it may be useful to use a non-local ...
...
In this case, it may be useful to use a non-local gateway,
which will optimise the reply address. This information
...
... which will optimise the reply address. This information
may be looked up in gateway tables in a manner equivalent to
the MCGAM lookup. Because of the similarity of lookup ...
... DNS) are also
available to look up this information. This information is
local, and a gateway may insert any appropriate (gateway)
OR ...
... available to look up this information. This information is
local, and a gateway may insert any appropriate (gateway)
OR Address ...
... Address. The longest possible match on the 822.domain
defines which gateway to use. This mechanism is used for
any part of the X.400 namespace ...
... X.400 namespace for which it is desirable to
identify a preferred X.400 gateway in order to optimise
routing.
...
... domain, a default value
(typically that of the local gateway) is used. It is never
appropriate to ignore the locally used MCGAMs.
...
... remaining within the RFC 822std11(-> 2822prop) world shall be configured
privately into the gateway in question. X.400 routing shall
...
... available MCGAMs. It is to support this case that the
definition of the global domain to gateway mapping is
important, as the use of this mapping will lead to a remote
X.400 ...
... OR Address
of Preferred Gateway table, pointing to c=gb; A=BTglobal; P=relay)
postmaster@UK.alter.net
...
... attribute, assume that the hierarchy is inverted. This is to
facilitate the situation where a user has input the attributes in
reverse hierarchical order. To do this the gateway shall first
map according to the order defined in 4.3.3. If this mapping
generates an address ...
...
RFC 1327(-> 2156prop) specified that this shall only be done when the gateway
identfied is local or otherwise known, and identified the approach
specified here as a pragmatic option. Experience has shown that this
...
... is effective in practice, despite theoretical problems.
If a gateway wishes to make a mapping in a manner similar to RFC
1327(-> 2156prop), but does not wish for this global interpretation (e.g., to
...
... domain defined attribute,
different to "RFC-822". An RFC 1327(-> 2156prop) gateway might be configurable to
operate in this manner.
...
... described below, and go to step 5. The default domain to be
used is the specification of the local gateway. A gateway
may use other domains ...
... domain to be
used is the specification of the local gateway. A gateway
may use other domains according to private mapping tables or
...
... heuristics. For example, it may choose a domain which it
knows to provide a free gateway service to the mapped
address.
...
... domain will correctly route to
a gateway. In general, this is achieved by carefully co-
ordinating RFC 822std11(-> 2822prop) routing ...
... 822std11(-> 2822prop) routing with the definition of the
MCGAMs, as there is no easy way for the gateway to make this
check. One rule that shall be used is that domains with
...
... domains with
only one component will not route to a gateway. If the
generated domain does not route ...
... treated as if no match is found.
The gateway may also make use of a mapping equivalent to the
MCGAM mapping to determine the domain to use. This mapping
...
... Address with an entry for A=ATT; C=us; into the domain
of Preferred Gateway table, pointing to attmail.com)
G=Andy; S=Wharol; O=MMNY; A=ATT; C=us;
...
... There are two types of repeated mapping:
1. A recursive mapping, where the repeat is within one gateway
2 A source route ...
... 2 A source route, where the repetition occurs across multiple
gateways
...
...
The mappings defined are symmetrical and reversible across a single
gateway. The symmetry is particularly useful in cases of (mail
exploder type) distribution list expansion. For example, an X.400
...
... X.400 or RFC 822std11(-> 2822prop)) where there is common agreement on gateway
identification, then this will apply to multiple gateways.
...
...
When a message traverses multiple gateways, the mapping will always
be reversible, in that a reply can be generated which will correctly
reverse the path. In many cases, the mapping will also be
...
...
This is routed to a gateway, which generates:
...
...
This is then routed to another gateway where the mapping is reversed
to give:
...
...
Here, use of the gateway is transparent.
...
...
This will be sent to an arbitrary UK Academic Community gateway by
X.400. Then it will be sent by JNT Mail to another gateway ...
... gateway by
X.400. Then it will be sent by JNT Mail to another gateway
determined by the domain Inria.ATLAS.FR ...
... delivery notification, this shall be
generated by the gateway. Supplementary Information shall be set to
indicate that the report is gateway generated. This information
...
... generated by the gateway. Supplementary Information shall be set to
indicate that the report is gateway generated. This information
shall include the name of the gateway generating the report.
...
... indicate that the report is gateway generated. This information
shall include the name of the gateway generating the report.
...
... 822std11(-> 2822prop) fields. The value of MTS.MTSIdentifier.local-part
will facilitate correlation of gateway errors.
...
... Receipt Notification Requested)". The effort of correlating P1
and P2 information is too great to justify the gateway sending
Receipt Notifications.
...
... 822std11(-> 2822prop) Message ID,
which is preferable to a gateway generated ID. A reversible and
symmetrical mapping is defined. This provides fully reversible
mappings when messages pass multiple times across the X.400 ...
... The mapping works by defining a way in which message IDs generated on
one side of the gateway can be represented on the other side in a
systematic manner. The mapping is defined so that the possibility of
clashes is low enough to be treated as impossible.
...
... IPMS.Heading.this-IPM (IPMS.IPMIdentifier). A default is generated
by the gateway. With the exception of "Received:", the values of
multiple fields are merged (e.g., If there are two "To:" fields, then
the mailboxes ...
... encoded information types in the trace is derived from the message
generated by the gateway, and shall reflect all body parts (including
those in enclosed messages). In addition it shall include the
Encoded Information Type ...
... This type of conversion will prevent the normal loop detection from
working in certain circumstances, and introduces the possiblity of
gateway loops. MIXER gateways shall therefore count the number of
...
... gateway loops. MIXER gateways shall therefore count the number of
MIXER conversions made. If this count exceeds five in one direction,
...
... element of trace information,
reflecting the gateway's local information and the time of
conversion. The MTA.InternalTraceInformationElement.mta-supplied-
...
... MTA.AdditionalAcctions.converted-encoded-information-types Set to
correct set of EITs for the message that is generated by the gateway.
This trace element ...
... Notifications and IP Messages. A gateway conforming to this
specification shall map all of these fields to X.400, except as
...
... DSN information available as a text body part in the outer
message, with the real returned content as an enclosed message. This
mechanism will ensure that information is not lost at the gateway.
...
... the rest of the field, which is encoded as EBNF.mts-msg-id. In other
cases, this field shall be generated by the MIXER Gateway.
...
... reporting-mta-field
dsn-gateway-field
received-from-mta-field
arrival-date-field
...
... follows.
If a status value is found that is not in this table, the gateway may
use the same mapping as for "X.n.0" (1/None or 0/None), or it may map
to another, configurable code. Implementors ...
... 822std11(-> 2822prop). MIXER simply
requires that a gateway requests the return of content service from
X.400 ...
... If this is not generated by the mapping (e.g., for a Delivery
Report), a value pointing at a gateway administrator shall be
assigned.
...
... If this is not generated by the mapping, it is assigned equal to
the SMTP Originator. If this is gateway generated, an appropriate
822.phrase shall be added.
...
...
If a non-standard extension is found, it shall be discarded, unless
the gateway understands the extension and can perform an appropriate
mapping onto an RFC 822std11(-> 2822prop) header field ...
... Notifications will not usually
need to be mapped by a MIXER gateway. A message is generated, with
the following fields:
...
... for transfer or for delivery, the message shall be non delivered by
the gateway because a critical extension cannot be correctly handled.
...
... Identifier:". This has been
changed to avoid confusion with MIME defined fields. Gateways
which reverse map, may support the old field.
...
... MTA.MessageTransferEnvelope.per-recipient-fields being passed through
the gateway, where the responsibility bit is set. In some cases, a
different RFC 822std11(-> 2822prop) ...
... MTA does not provide this service, the function may
optionally be implemented by the gateway: that is, the gateway may
hold the message until the time specified in the protocol element ...
... service, the function may
optionally be implemented by the gateway: that is, the gateway may
hold the message until the time specified in the protocol element.
...
... If MTA.PerMessageTransferFields.extensions.dl-expansion-prohibited is
present and set to dl-expansion-probited, the gateway may reject that
message on the basis that it is unable to control distribution list
expansion beyond the gateway ...
... gateway may reject that
message on the basis that it is unable to control distribution list
expansion beyond the gateway. The service relating to this is
described in Section 2.3.1.2. This approach was not specified in RFC
...
... MTA.PerMessageTransferFields.extensions.recipient-reassignment-
prohibited is present and set to recipeint-reassignment-probited, the
gateway may reject that message on the basis that it is unable to
control distribution list expansion beyond the gateway. The service ...
... gateway may reject that message on the basis that it is unable to
control distribution list expansion beyond the gateway. The service
relating to this is described in Section 2.3.1.2. This approach was
...
... Relayed, Expanded, Redirected ; Tue, 20 Jun 89 19:25:11 +0100
The gateway itself shall add a single line of trace information,
indicating MIXER ...
... From:
An administrator at the gateway system.
To: A mapping of the
...
... 822std11(-> 2822prop) user in a consistent manner.
The format is structured as if it was a message coming from the
gateway, with three body parts. The first body part is ASCII text
structured as follows:
...
... The original message shall be included in the delivery status
notification if it is available. The original message will usually be
available at the gateway, as discussed in Section 5.2. If the
original message is available, but is not a legal message format, a
...
... Reporting-MTA: x400; bells.cs.ucl.ac.uk in /PRMD=uk.ac/ADMD=gold
400/C=gb/ Arrival-Date: Thu, 7 Feb 1991 15:48:34 +0000 DSN-Gateway:
dns; bells.cs.ucl.ac.uk X400-Conversion-Date: Thu, 7 Feb 1991
15:48:40 +0000 Original-Envelope-Id:
...
... Arrival-Date: Thu, 7 Feb 1991 15:48:40 +0000
DSN-Gateway: dns; bells.cs.ucl.ac.uk
X400-Conversion-Date: Thu, 7 Feb 1991 15:49:12 +0000
Original-Envelope-Id:
...
... MTS internal issue. Any probe shall be serviced by the
gateway, as there is no equivalent RFC 822std11(-> 2822prop) functionality. The value
of the reply is dependent on whether the gateway ...
... gateway, as there is no equivalent RFC 822std11(-> 2822prop) functionality. The value
of the reply is dependent on whether the gateway could service an MTS
...
... 29]. Use of these
extensions by a MIXER gateway is optional. If these extensions are
used, they shall be used in the manner described below.
...
... non-delivery-report bit is
set. If the gateway uses the NOTIFY command, it shall perform
this mapping in all cases.
...
... is NEVER. If the report bit is set, SUCCESS is used. Otherwise,
FAILURE is used. If this is done, the gateway shall not generate
a delivery report for this recipient, unless this is needed in the
...
...
This appendix defines a number of options, which a conforming gateway
shall specify. Conformance to this specification shall not be
claimed if any of the mandatory features are not implemented. A
...
... - Formats for all fields shall be followed.
- The gateway shall enable MCGAMs to be used.
- Formats for subject ...