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RFC 2524

Neda's Efficient Mail Submission and Delivery (EMSD) Protocol Specification Version 1.3

Pages: 83
Informational
Part 2 of 4 – Pages 11 to 39
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Top   ToC   RFC2524 - Page 11   prevText

3 EFFICIENT MAIL SUBMISSION AND DELIVERY PROTOCOL

EM Submission is the process of transferring a message from EMSD-UA to EMSD-SA. EM Delivery is the process of transferring a message from EMSD-SA to EMSD-UA.
Top   ToC   RFC2524 - Page 12
   The Message-submission service enables an EMSD-UA to submit a message
   to the EMSD-SA for transfer and delivery to one or more recipients.
   The Message-submission Service comprises of the submit operation --
   invoked by the EMSD-UA -- and possibly the submitVerify operation --
   invoked by the EMSD-SA.

   The Message-delivery service enables the EMSD-SA to deliver a message
   to an EMSD-UA. The Message-delivery Service comprises of the deliver
   operation -- invoked by the EMSD-SA -- and possibly the deliverVerify
   operation -- invoked by the EMSD-UA.

   EMSD-UA uses the following services:

        o Message-submission

   +---------------------------------------------+
   | MTS                                         |
   |                                             |
   |  +-------------------------+                |
   |  | MRS                     |                |
   |  |  +---+          +---+   |                |
   |  |  |   |          | M |   |         +---+  |
   |  |  |   |<-------->| T |<----------->|   |  |
   |  |  |   |          | A |   |         |   |  |               +---+
   |  |  |   |          +---+   |         | E |  |               | E |
   |  |  |   |                  |         | M |  |               | M |
   |  |  | M |                  |         | S |  |   EMSD-P&FS   | S |
   |  |  | T |<-------------------------->| D |<---------------->| D |
   |  |  | A |                  |         | - |  |               | - |
   |  |  |   |          +---+   |         | S |  |               | U |
   |  |  |   |          | M |   |         | A |  |               | A |
   |  |  |   |<-------->| T |<----------->|   |  |               +---+
   |  |  |   |          | A |   |         |   |  |
   |  |  +---+          +---+   |         +---+  |
   |  |                         |                |
   |  +-------------------------+                |
   |                                             |
   |                                             |
   +---------------------------------------------+


         Figure 2:  Efficient Mail Submission and Delivery Protocol

      o Delivery-control (the deliveryControl operation).

   EMSD-SA uses the following services:

      o Message-delivery
Top   ToC   RFC2524 - Page 13
      o Submission-control (the submissionControl operation).

   This specification expresses information objects using ASN.1 [X.208].

   This specification expresses Remote Operations based on the model of
   ESROS as specified in Efficient Short Remote Operations (RFC-2188)
   [1].  The ES-OPERATION notation of (RFC-2188) is used throughout this
   specification to define specific operations.

   This specification uses the Duplicate Operation Detection Support
   functions as specified in Section 4.

3.1 Use Of Lower Layers

3.1.1 Use of ESROS

ESRO protocol, as specified in (RFC-2188 [1]), provides reliable connectionless remote operation services on top of UDP [6] with minimum overhead. ESRO protocol supports segmentation and reassembly, concatenation and separation. ESRO Services (2-Way and 3-Way handshake) shall be used by the EMSD- P. ESRO Service Access Point (SAP) selectors used by EMSD-P are enumerated in the protocol.

3.1.2 Use Of UDP

EMSD-P through ESRO MUST use UDP [6] port number 642 (esro-emsdp). Note that specification of Service Access Points (SAP) for EMSD-P include the UDP Port Number specification in addition to ESRO SAP selector specifications. In other words, EMSD-P's use of ESRO SAPs does not preclude use of the same SAP selectors by other protocols which use a UDP port other than port 642. Such usage of ESRO is a design characteristic of ESRO which results into bandwidth efficiency and is not a scalability limitation.

3.1.3 Encoding Rules

Use of Basic Encoding Rules (BER) [5] is mandatory for both EMSD Format Standards and EMSD Protocol. In order to minimize data transfer, the following restrictions shall be maintained in the formatting of EMSD PDUs: o Specifically, when ASN.1 Basic Encoding Rules are being used:
Top   ToC   RFC2524 - Page 14
         A. Only the "Definite" form of Length encoding MUST be used,

         B. The "Short" form of Length encoding MUST be used whenever
            possible (i.e.  when the Length is less than 128), and

         C. OCTET STRING and BIT STRING values, and any other native
            ASN.1 types which may be encoded as either "Primitive" or
            "Constructed", MUST always be encoded as "Primitive" and
            MUST never be "Constructed".

3.1.4 Presentation Context

Parameter Encoding Type of "0" MUST be used in ESRO Protocol to identify Basic Encoding Rules for operation arguments.

3.2 EMSD-UA Invoked Operations

The following operations are invoked by EMSD-UA: a. submit b. deliveryControl c. deliveryVerify The submit operation uses the duplication detection functional unit while deliveryControl and deliveryVerify don't use the duplication detection. The complete definition of these operations follows.

3.2.1 submit

The submit ES-OPERATION enables an EMSD-UA to submit a message to the EMSD-SA for transfer and delivery to one or more recipients. submit ES-OPERATION ARGUMENT SubmitArgument RESULT SubmitResult ERRORS { submissionControlViolated, securityError, resourceError, protocolViolation, messageError } ::= 33;
Top   ToC   RFC2524 - Page 15
   Duplicate operation detection is necessary for this operation.

   The successful completion of the ES-OPERATION signifies that the
   EMSD-SA has accepted responsibility for the message (but not that it
   has delivered it to its intended recipients).

   The disruption of the ES-OPERATION by an error signifies that the
   EMSD-SA cannot assume responsibility for the message.


   Arguments

   This operation's arguments are:

   SubmitArgument ::= SEQUENCE
   {
     -- Security features
     security                [0]    IMPLICIT SecurityElement OPTIONAL,

     -- Segmentation features for efficient transport
     segment-info                            SegmentInfo OPTIONAL,

     -- Content type of the message
     content-type                            ContentType,

     --
     -- THE CONTENT --
     --

     -- The submission content
     content                                 ANY DEFINED BY content-type
   };


   The fields are:


   Security

   See Section 3.4.1, "SecurityElements".


   Segment-info

   See Section 3.4.2, "Message Segmentation and Reassembly".
Top   ToC   RFC2524 - Page 16
   Content-type

   This argument identifies the type of the content of the message.  It
   identifies the abstract syntax and the encoding rules used.


   Content

   This argument contains the information the message is intended to
   convey to the recipient(s).  It shall be generated by the originator
   of the message.


   Results

   This operation's results are:

   SubmitResult ::= SEQUENCE

       {
           -- Permanent identifier for this message.
           -- Also contains the message submission time.
           -- See comment regarding assignment of message identifiers,
           -- at the definition of EMSDLocalMessageId.

           message-id                              EMSDLocalMessageId

       };


   The fields are:


   Message-id

   This result contains an EMSD-SA-identifier that uniquely and
   unambiguously identifies the message-submission.  It shall be
   generated by the EMSD-SA.


   Errors

   See Section 3.4.3.
Top   ToC   RFC2524 - Page 17

3.2.2 deliveryControl

The deliveryControl ES-OPERATION enables the EMSD-UA to temporarily limit the operations that the EMSD-SA may invoke, and the messages that the EMSD-SA may deliver to the EMSD-UA via the Message delivery ES-OPERATION. deliveryControl ES-OPERATION ARGUMENT DeliveryControlArgument RESULT DeliveryControlResult ERRORS { securityError, resourceError, protocolViolation } ::= 2; The duplicate operation detection is not required for this operation. The EMSD-SA shall hold until a later time, rather than abandon, ES- OPERATIONS and messages that are presently suspended. The successful completion of the ES-OPERATION signifies that the specified controls are now in force. The ES-OPERATION returns an indication of any ES-OPERATIONS that the EMSD-SA would invoke, or any message types that the EMSD-SA would deliver, were it not for the prevailing controls. Arguments This operation's arguments are: DeliveryControlArgument ::= SEQUENCE { -- Request an addition of or removal of a set of restrictions restrict [0] IMPLICIT Restrict DEFAULT update, -- Which operations are to be placed in the restriction set permissible-operations [1] IMPLICIT Operations OPTIONAL, -- What maximum content length should be allowed permissible-max-content-length [2] IMPLICIT INTEGER (0..ub-content-length) OPTIONAL,
Top   ToC   RFC2524 - Page 18
     -- What is the lowest priority message which may be delivered
     permissible-lowest-priority

                                     [3]     IMPLICIT ENUMERATED
                                              {
                                                non-urgent     (0),
                                                normal         (1),
                                                urgent         (2)
                                              } OPTIONAL,

     -- Security features
     security                        [4]     IMPLICIT SecurityElement
                                             OPTIONAL,

     -- User Feature selection
     user-features                   [5]     IMPLICIT OCTET STRING
                                             OPTIONAL
   };



   Restrict

   This argument indicates whether the controls on ES-OPERATIONS are to
   be updated or removed.  It may be generated by the EMSD-UA.

   This argument may have one of the following values:

      o update:  The other arguments update the prevailing controls;

      o remove:  All temporary controls are to be removed

   In the absence of this argument, the default update shall be assumed.


   Permissible-operations

   This argument indicates the ES-OPERATIONS that the EMSD-SA may invoke
   on the EMSD-UA. It may be generated by the EMSD-UA.

   This argument may have the value allowed or prohibited for each of
   the following:

      o message-delivery:  The EMSD-SA may/may not invoke the deliver
        ES-OPERATIONS; and

      o Other ES-OPERATIONS are not subject to controls, and may be
        invoked at any time.
Top   ToC   RFC2524 - Page 19
   In the absence of this argument, the ES-OPERATIONS that the EMSD-SA
   may invoke on the EMSD-UA are unchanged.


   Permissible-max-content-length

   This argument contains the content-length, in octets, of the
   longest-content message that the EMSD-SA shall deliver to the EMSD-UA
   via the deliver ES-OPERATIONS. It may be generated by the EMSD-UA.

   In the absence of this argument, the permissible-maximum-content-
   length of a message that the EMSD-SA may deliver to the EMSD-UA is
   unchanged.


   Permissible-lowest-priority

   This argument contains the priority of the lowest priority message
   that the EMSD-SA shall deliver to the EMSD-UA via the deliver ES-
   OPERATIONS. It may be generated by the EMSD-UA.

   This argument may have one of the following values of the priority
   argument of the submit ES-OPERATIONS: normal, non-urgent or urgent.

   In the absence of this argument, the priority of the lowest priority
   message that the EMSD-SA shall deliver to the EMSD-UA is unchanged.


   Security

   See Section 3.4.1, "SecurityElements".


   User-features

   This argument contains information that allows the EMSD-UA to convey
   to MTS the feature set that the user is capable of supporting.  This
   argument will be defined when the setConfiguration and
   getConfiguration operations are defined.


   Results

   DeliveryControlResult ::= SEQUENCE
   {
     -- Operation types queued at the EMSD-SA due to existing
     -- restrictions.
     waiting-operations      [0]     IMPLICIT Operations DEFAULT { },
Top   ToC   RFC2524 - Page 20
     -- Types of messages queued at the EMSD-SA due to
     -- existing restrictions
     waiting-messages        [1]     IMPLICIT WaitingMessages
                                     DEFAULT { },

     -- Content Types of messages queued at the EMSD-SA
     waiting-content-types   SEQUENCE SIZE (0..ub-content-types) OF
                                            ContentType DEFAULT { }

   };

   Restrict ::= ENUMERATED
   {
       update                                      (1),
       remove                                      (2)
   };

   Operations ::= BIT STRING
   {
       submission                                  (0),
       delivery                                    (1)
   };

   WaitingMessages ::= BIT STRING
   {
       long-content                                (0),
       low-priority                                (1)


   };


   Waiting-operations

   This result indicates the ES-OPERATIONS being held by the EMSD-SA,
   and that the EMSD-SA would invoke on the EMSD-UA if it were not for
   the prevailing controls.  It may be generated by the EMSD-SA.

   This result may have the value holding or not-holding for each of the
   following:

      o message-delivery:  The EMSD-SA is/is not holding messages, and
        would invoke the deliver ES-OPERATIONS on the EMSD-UA if it were
        not for the prevailing controls.

   In the absence of this result, it may be assumed that the EMSD-SA is
   not holding any messages for delivery due to the prevailing controls.
Top   ToC   RFC2524 - Page 21
   Waiting-messages

   This result indicates the kind of messages the EMSD-SA is holding for
   delivery to the EMSD-UA, and would deliver via the deliver ES-
   OPERATIONS, if it were not for the prevailing controls.  It may be
   generated by the EMSD-SA.

   This result may have one or more of the following values:

      o long-content:  The EMSD-SA has messages held for delivery to the
        EMSD-UA which exceed the permissible maximum-content-length
        control currently in force;

      o low-priority:  The EMSD-SA has messages held for delivery to the
        EMSD-UA of a lower priority than the permissible-lowest-priority
        control currently in force;

   In the absence of this result, it may be assumed that the EMSD-SA is
   not holding any messages for delivery to the EMSD-UA due to the
   permissible-maximum-content-length, permissible-lowest-priority or
   permissible-security context controls currently in force.

   Errors

   See Section 3.4.3.

3.2.3 deliveryVerify

The deliveryVerify ES-OPERATIONS enables the EMSD-UA to verify delivery of a message when it receives FAILURE.indication for deliver ES-OPERATIONS. deliveryVerify ES-OPERATION ARGUMENT DeliveryVerifyArgument RESULT DeliveryVerifyResult ERRORS { verifyError, resourceError, protocolViolation } ::= 5; The duplicate operation detection is not required for this operation. Arguments
Top   ToC   RFC2524 - Page 22
   This operation's arguments are:

   DeliveryVerifyArgument ::= SEQUENCE

   {
     -- Identifier of this message. This is the same identifier that
     -- was provided to the originator in the Submission Result.
     -- See comment regarding assignment of message identifiers,
     -- at the definition of EMSDMessageId.
     message-id                                      EMSDMessageId
   };


   Message-id

   This argument contains an EMSD-SA-identifier that distinguishes the
   message from all other messages.  It shall be generated by the EMSD-
   SA, and shall have the same value as the message-submission-
   identifier supplied to the originator of the message when the message
   was submitted.


   Results

   DeliveryVerifyResult ::= SEQUENCE
   {
            status  DeliveryStatus
   };

    DeliveryStatus  ::= ENUMERATED
   {
           no-report-is-sent-out                   (1),
           delivery-report-is-sent-out             (2),
           non-delivery-report-is-sent-out         (3)
    };



   No-report-is-sent-out

   This result indicates that EMSD-SA has received the delivery verify
   and no report is sent out (either because it has not been requested
   or EMSD-SA has problems and can not send it out).


   Delivery-report-is-sent-out

   This result indicates that EMSD-SA has received the delivery verify
Top   ToC   RFC2524 - Page 23
   and has sent the delivery report out.


   Non-Delivery-report-is-sent-out

   This result indicates that EMSD-SA has received the delivery verify
   but it has already sent out a non-Delivery report.  This should not
   happen in normal cases but a wrong user profile on EMSD-SA side can
   result in this outcome.

   Errors

   See Section 3.4.3.


3.3 EMSD-SA Invoked Operations

This section defines the operations invoked by the EMSD-SA: a. deliver; b. submissionControl; c. submissionVerify. The deliver operation uses 3-Way handshake service of ESROS. This operation always uses the duplication detection functional unit. The submissionControl and submissionVerify operations use 2-Way handshake service of ESROS without duplication detection.

3.3.1 deliver

The deliver ES-OPERATIONS enables the EMSD-SA to deliver a message to an EMSD-UA. deliver ES-OPERATION ARGUMENT DeliverArgument RESULT NULL ERRORS { deliveryControlViolated, securityError, resourceError, protocolViolation, messageError } ::= 35;
Top   ToC   RFC2524 - Page 24
   The EMSD-UA MUST not refuse performing the deliver ES-OPERATION
   unless the delivery would violate the deliveryControl restrictions
   then in force.


   Arguments

   This operation's arguments are:

   DeliverArgument ::= SEQUENCE
   {
     -- Identifier of this message. This is the same identifier that
     -- was provided to the originator in the Submission Result.
     -- See comment regarding assignment of message identifiers,
     -- at the definition of EMSDMessageId.
     message-id                                      EMSDMessageId,

     -- Time the message was delivered to the recipient by EMSD-SA
     message-delivery-time                           DateTime,

     -- Time EMSD-SA originally took responsibility for processing
     -- of this message. This field shall be omitted if the message-id
     -- contains an EMSDLocalMessageId, because that field contains
     -- the submission time within it.
     message-submission-time [0]  IMPLICIT DateTime OPTIONAL,

     -- Security features
     security                [1]  IMPLICIT SecurityElement OPTIONAL,

     -- SegContentTypementation features for efficient transport
     segment-info                              SegmentInfo OPTIONAL,

     -- The type of the content
     content-type                                ContentType,

     --
     -- THE CONTENT --
     --

     -- The submitted (and now being delivered) content
     content                           ANY DEFINED BY content-type
   };
Top   ToC   RFC2524 - Page 25
   message-id

   This argument contains an EMSD-SA-identifier that distinguishes the
   message from all other messages.  When within the EMSD, it MUST be
   generated by the EMSD-SA, and MUST have the same value as the
   message-submission-identifier supplied to the originator of the
   message when the message was submitted.


   Message-delivery-time

   This argument contains the Time at which delivery occurs and at which
   the EMSD-SA is relinquishing responsibility for the message.  It
   shall be generated by the EMSD-SA.


   Results

   This operation returns an empty result as indication of success.


   Errors

   See Section 3.4.3.


3.3.2 submissionControl

submissionControl ES-OPERATION ARGUMENT SubmissionControlArgument RESULT SubmissionControlResult ERRORS { securityError, resourceError, protocolViolation } ::= 4; The submissionControl ES-OPERATIONS enables the EMSD-SA to temporarily limit the operations that the EMSD-UA may invoke, and the messages that the EMSD-UA may submit to the EMSD-SA via the submit ES-OPERATIONS. The duplicate operation detection is not required for this operation. The EMSD-UA should hold until a later time, rather than abandon, ES- OPERATIONS and messages that are presently suspended.
Top   ToC   RFC2524 - Page 26
   The successful completion of the ES-OPERATIONS signifies that the
   specified controls are now in force.  These controls supersede any
   previously in force, and remain in effect until the association is
   released or the EMSD-SA re-invokes the submissionControl ES-
   OPERATIONS.

   The ES-OPERATIONS returns an indication of any ES-OPERATIONS that the
   EMSD-UA would invoke were it not for the prevailing controls.


   Arguments

   This operation's arguments are:

   SubmissionControlArgument ::= SEQUENCE
   {
     -- Request an addition of or removal of a set of restrictions
     restrict               [0]     IMPLICIT Restrict DEFAULT update,

     -- Which operations are to be placed in the restriction set
     permissible-operations  [1]     IMPLICIT Operations OPTIONAL,

     -- What maximum content length should be allowed
     permissible-max-content-length
                             [2]     IMPLICIT INTEGER
                                     (0..ub-content-length) OPTIONAL,

     -- Security features
     security                [3]     IMPLICIT SecurityElement
                                                     OPTIONAL
   };



   Restrict

   This argument indicates whether the controls on ES-OPERATIONS are to
   be updated or removed.  It may be generated by the EMSD-SA.

   This argument may have one of the following values:

      o update:  The other arguments update the prevailing controls;

      o remove:  All temporary controls are to be removed

   In the absence of this argument, the default update shall be assumed.
Top   ToC   RFC2524 - Page 27
   Permissible-operations

   This argument indicates the ES-OPERATIONS that the EMSD-UA may invoke
   on the EMSD-SA. It may be generated by the EMSD-SA.

   This argument may have the value allowed or prohibited for each of
   the following:

      o submit:  The EMSD-UA may/may not invoke the submit ES-
        OPERATIONS; and

      o Other ES-OPERATIONS are not subject to controls, and may be
        invoked at any time.

   In the absence of this argument, the ES-OPERATIONS that the EMSD-UA
   may invoke on the EMSD-SA are unchanged.


   Permissible-max-content-length

   This argument contains the content-length, in octets, of the
   longest-content message that the EMSD-UA shall submit to the EMSD-SA
   via the submit ES-OPERATIONS. It may be generated by the EMSD-SA.

   In the absence of this argument, the permissible-maximum-content-
   length of a message that the EMSD-UA may submit to the EMSD-SA is
   unchanged.


   Security

   See Section 3.4.1, "SecurityElements".


   Results

   SubmissionControlResult ::= SEQUENCE
   {
     -- Operation types queued at the EMSD-SA due to existing
     -- restrictions.
     waiting-operations    [0]   IMPLICIT Operations DEFAULT { }

   };
Top   ToC   RFC2524 - Page 28
   Waiting-operations

   This result indicates the ES-OPERATIONS being held by the EMSD-UA,
   and that the EMSD-UA would invoke if it were not for the prevailing
   controls.  It may be generated by the EMSD-UA.

   This result may have the value holding or not-holding for each of the
   following:

      o submit:  The EMSD-UA is/is not holding messages, and would
        invoke the submit ES-OPERATIONS if it were not for the
        prevailing controls.

   In the absence of this result, it may be assumed that the EMSD-UA is
   not holding any messages for submission due to the prevailing
   controls.


   Errors

   See Section 3.4.3.


3.3.3 submissionVerify

The submissionVerify ES-OPERATIONS enables the EMSD-SA to verify if the EMSD-UA has received the result of its submission. submissionVerify ES-OPERATION ARGUMENT SubmissionVerifyArgument RESULT SubmissionVerifyResult ERRORS { submissionVerifyError, resourceError, protocolViolation } ::= 6; The duplicate operation detection is not required for this operation. Arguments This operation's arguments are: SubmissionVerifyArgument ::= SEQUENCE
Top   ToC   RFC2524 - Page 29
     -- Identifier of this message. This is the same identifier that
     -- was provided to the originator in the Submission Result.
     -- See comment regarding assignment of message identifiers,
     -- at the definition of EMSDMessageId.
     {
        message-id                                  EMSDMessageId
     };


   Message-id

   This argument contains an EMSD-SA-identifier that distinguishes the
   message from all other messages.  It shall be generated by the EMSD-
   SA, and shall have the same value as the message-submission-
   identifier supplied to the originator of the message when the message
   was submitted.


   Results

   SubmissionVerifyResult ::= SEQUENCE
   {
           status  SubmissionStatus
   };

   SubmissionStatus::= ENUMERATED
   {
           send-message            (1),
           drop-message            (2)
   };


   Send-message

   This result indicates that EMSD-SA is supposed to send the message
   out.


   Drop-message

   This result indicates that EMSD-SA is supposed to drop the message.


   Errors

   See Section 3.4.3.
Top   ToC   RFC2524 - Page 30

3.4 EMSD Common Information Objects

3.4.1 SecurityElements

SecurityElement ::= SEQUENCE { credentials Credentials, contentIntegrityCheck ContentIntegrityCheck OPTIONAL }; Credentials ::= CHOICE { simple [0] IMPLICIT SimpleCredentials -- Strong Credentials are for future study -- strong [1] IMPLICIT StrongCredentials -- externalProcedure [2] EXTERNAL }; SimpleCredentials ::= SEQUENCE { eMSDAddress EMSDAddress OPTIONAL, password [0] IMPLICIT OCTET STRING SIZE (0..ub-password-length)) OPTIONAL }; -- StrongCredentials ::= NULL -- for now. -- ContentIntegrityCheck is a 16-bit checksum of content ContentIntegrityCheck ::= INTEGER (0..65535);

3.4.2 Message Segmentation and Reassembly

Small messages can benefit from the efficiencies of connectionless feature of ESROS (See Efficient Short Remote Operations, RFC-2188 [1]). Very large messages are transferred using protocols (e.g., SMTP) that rely on Connection Oriented Transport Service (e.g., TCP). When a message is too large to fit in a single connectionless PDU but is not large enough to justify the overhead of connection establishment, it may be more efficient for the message to be segmented and reassembled while the connectionless service of ESROS is used. If the underlying Remote Operation Service is capable of efficient segmentation/reassembly over connectionless (CL) services,
Top   ToC   RFC2524 - Page 31
   then use of the segmenting/reassembly mechanism introduced in this
   section is not necessary.  This feature is accommodated in this layer
   by:

   SegmentInfo ::= CHOICE

   {
     first           [APPLICATION 2]         IMPLICIT FirstSegment,
     other           [APPLICATION 3]         IMPLICIT OtherSegment
   };

   FirstSegment ::= SEQUENCE
   {
     sequence-id                             INTEGER,
     number-of-segments                      INTEGER
     -- number-of-segments must not exceed ub-total-number-of-segments
   };

   OtherSegment ::= SEQUENCE
   {
     sequence-id                             INTEGER,
     segment-number                          INTEGER
   };

   Segmentation and reassembly only applies to Message-submission and
   Message-delivery.

   The sender of the message is responsible for segmenting the message
   content into segments that fit in CL PDUs.  The segmented content is
   sent in a sequence of message-segments each carrying a segment of the
   content.  sequence-Id is a unique identifier that is present in all
   message-segments.  In addition to sequence identifier, the first
   message-segment specifies the total number of segments (number-of-
   segments).  Other message-segments have a segment sequence number
   (segment-number).  The receiver is responsible for sequencing (based
   on segment-number) and reassembling the entire message.


   Segmenting over the Connectionless ESRO Service

   The sender of the message maps the original message into an ordered
   sequence of message-segments.  This sequence shall not be interrupted
   by other messages over the same ESROS association.

   All message-segments in the sequence shall be assigned a sequence
   identifier by sender.  The sequence identifier shall be incremented
   by one by the sender after transmission of a complete message
   sequence.
Top   ToC   RFC2524 - Page 32
   The first message-segment specifies the total number of segments.
   All message-segments in the sequence except the first one shall be
   sequentially numbered, starting at 1 (first message-segment has
   implicit segment number of 0).

   Each message-segment is transmitted by issuing a Message-submission
   or Message-delivery ES-OPERATIONS. All segments of a segmented
   message are identified by the same sequence-id.  For a given message,
   the receiver should not impose any restriction on the order of
   arrival of message-segments.

   There is no requirement that any message-segment content be of
   maximum length allowed by ESROS for connectionless transmission;
   however, no more than ub-total-number-of-segments segments can be
   derived from a single message.

   The receiver reassembles a sequence of message-segments into a single
   message.  A message shall not be further processed unless all
   segments of the message are received.  Failure to receive the message
   shall be determined by the following events:

      o Expiration of Reassembly Timer (see Section 3.4.3).

      o Receipt of a message-segment with different sequence identifier.

   In the event of the above mentioned failures, the receiver shall
   discard a partially assembled sequence.

   In Reassembly process, all arguments other than content are ignored
   in all segments except the first one.  The content parts of all
   segments are concatenated to compose the original message content.

   When sender receives FAILURE.indication (as opposed to a
   resourceError) for a message-segment, the whole message shall be
   retransmitted.

   In the case of submission and delivery operations, the verify
   function is used as described below:

   Receiver ignores FAILURE.indications received for message-segments,
   and just collects the message-segments to complete the message.
   However, it keeps a failure status for a segmented message which says
   if any segment of the message has received FAILURE.indication.  When
   receiver succeeds to assemble the whole segmented message, then if
   the status of the message shows there has been a FAILURE.indication
   for any of the message-segments, it verifies the message through
   verify operation.  It's not enough to invoke verify operation just
   based on the last message-segment because the sender might send a
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   segment without waiting for the result of the previous segment.  In
   such cases, there might be any combination of success and failure for
   message-segments on the sender side.

   Receiver uses the error code ResourceError (see Section 3.4.3) to ask
   for retransmission of a single segment and uses the error code
   MessageError (see Section 3.4.3) to ask for retransmission of all
   segments (the whole message).


   Reassembly Timer

   The Reassembly Timer is a local timer maintained by the receiver of
   message-segments that assists in performing the reassembly function.
   This timer determines how long a receiver waits for all segments of a
   message-segment sequence to be received.  The timer protects the
   receiver from the loss of a series of segments and possible sequence
   identifier wrap-around.

   The Reassembly Timer shall be started on receipt of a message-segment
   with different sequence identifier than that previously received.
   The timer shall be stopped on receipt of all segments composing the
   sequence.

   The value of Reassembly Timer is defined based on the network
   characteristics and the number of segments.  This requires that the
   transmission of all segments of a single message must be completed
   within this time limit.

3.4.3 Common Errors

protocolVersionNotRecognized ERROR PARAMETER NULL ::= 1; submissionControlViolated ERROR PARAMETER NULL ::= 2; messageIdentifierInvalid ERROR PARAMETER NULL ::= 3; securityError ERROR PARAMETER security-problem SecurityProblem ::= 4; deliveryControlViolated ERROR PARAMETER NULL ::= 5; resourceError ERROR PARAMETER NULL ::= 6; protocolViolation ERROR PARAMETER NULL ::= 7; messageError ERROR PARAMETER NULL ::= 8; SecurityProblem ::= INTEGER (0..127);
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   protocolVersionNotRecognized

   The major and minor protocol versions presented do not match those
   recognized as being valid.


   submissionControlViolated

   The Submission control violated error reports the violation by the
   MTS-user of a control on submission services imposed by the MTS via
   the Submission control service.  The Submission control violated
   abstract-error has no parameters.


   messageIdentifierInvalid

   The Message Identifier Invalid error reports that the Message
   Identifier presented to the MTS is not considered valid.


   securityError

   The Security error reports that the requested operation could not be
   provided by the MTS or MTS-user because it would violate the security
   policy in force.


   deliveryControlViolated

   The Delivery control violated error reports the violation by the MTS
   of a control on delivery operations imposed by the MTS-user via the
   Delivery-control operation.


   resourceError

   The messaging agent cannot currently support this operation.  In the
   case of segmentation and reassembly, resourceError is by the receiver
   used to request that the sender retransmit of a single segment.


   protocolViolation

   Indicates that one or more mandatory argument(s) were missing.
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   messageError

   For a multi-segment message, this error indicates that the messaging
   agent has not received the message completely and that the message
   must be retransmitted.


   SecurityProblem

   To ensure the security-policy is not violated during delivery, the
   message-security-label is checked against the security-context.  If
   delivery is barred by the security-policy then, subject to the
   security policy, a report instruction for this is generated.

3.4.4 ContentType

ContentType ::= INTEGER { -- Content type 0 is reserved and shall never be transmitted. reserved (0), -- Content types between 1 and 31 (inclusive) are for -- internal-use only probe (1), -- reserved delivery-report (2), -- reserved -- Content types between 32 and 63 (inclusive) are for -- message types defined within this specifications. emsd-interpersonal-messaging-1995 (32), voice-messaging (33) -- reserved -- Content types beyond and including 64 are for -- bilaterally-agreed use between peers. } (0..127);

3.4.5 EMSDMessageId

If this message was originated as an RFC-822 message, then this EMSDMessageId shall be the "Message-Id:" field from that message. If this message was originated within the EMSD domain, then this identifier shall be unique for the EMSD-SA generating this id. EMSDMessageId ::= CHOICE { EMSDLocalMessageId [APPLICATION 4] IMPLICIT EMSDLocalMessageId, rfc822MessageId [APPLICATION 5] IMPLICIT AsciiPrintableString
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                         (SIZE (0..ub-message-id-length))
   };

   EMSDLocalMessageId ::= SEQUENCE
   {
     submissionTime            DateTime,
     messageNumber             INTEGER (0..ub-local-message-nu)
   };

3.4.6 EMSDORAddress

EMSDORAddress ::= CHOICE { -- This is the local-format address emsd-local-address-format EMSDAddress, -- This is a globally-unique RFC-822 Address rfc822DomainAddress AsciiPrintableString }; In the global sense Originators and Recipients are represented by EMSDORAddress. The rfc822Domain may be used to address any recipient.

3.4.7 EMSDAddress

EMSDAddress ::= SEQUENCE { emsd-address OCTET STRING (SIZE (1..ub-emsd-address-length)), -- emsd-address is a decimal integer in BCD (Binary Encoded Decimal) format. -- If it had an odd number of digits, it is -- padded with 0 on the left. emsd-name [0] IMPLICIT OCTET STRING (SIZE (0..ub-emsd-name-length)) OPTIONAL }; Originator and Recipients in the scope of EMSD network are identified by a digit based addressing scheme. EMSDAddress can only be used where the scope of addressing has clearly been limited to the EMSD network.

3.4.8 DateTime

DateTime ::= INTEGER;
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   DateTime is a Julian date, expressed as the number of seconds since
   00:00:00 UTC, January 1, 1970.

3.4.9 AsciiPrintableString

Iso8859String ::= GeneralString; AsciiPrintableString ::= [APPLICATION 0] IMPLICIT Iso8859String (FROM (" "|"!"|"#"|"$"|"%"|"&"|"'"|"("|")"|"*"|"+"|","|"-"|"."|"/"| "0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9"|":"|";"|"<"|"="|">"| "?"|"@"|"A"|"B"|"C"|"D"|"E"|"F"|"G"|"H"|"I"|"J"|"K"|"L"|"M"| "N"|"O"|"P"|"Q"|"R"|"S"|"T"|"U"|"V"|"W"|"X"|"Y"|"Z"|"["|"]"| "^"|"_"|"`"|"a"|"b"|"c"|"d"|"e"|"f"|"g"|"h"|"i"|"j"|"k"|"l"| "m"|"n"|"o"|"p"|"q"|"r"|"s"|"t"|"u"|"v"|"w"|"x"|"y"|"z"|"{"| "|"|"}"|"~"|"\"|""""));

3.4.10 ProtocolVersionNumber

ProtocolVersionNumber ::= [APPLICATION 1] SEQUENCE { version-major INTEGER, +------------------+-------+----+---------+----+---------+-----+-----+ |Operation |Invoker|Sap |Performer|Sap |Duplicate|OpId |ESROS| | | |Sel | |Sel |Detect | |Use | |__________________|_______|____|_________|____|_________|_____|_____| |submit |UA |4 |MTS |5 |Yes |33 |3-Way| |__________________|_______|____|_________|____|_________|_____|_____| |deliver |MTS |2 |UA |3 |Yes |35 |3-Way| |__________________|_______|____|_________|____|_________|_____|_____| |deliveryControl |UA |8 |MTS |9 |No |2 |2-Way| |__________________|_______|____|_________|____|_________|_____|_____| |submissionControl |MTS |6 |UA |7 |No |4 |2-Way| |__________________|_______|____|_________|____|_________|_____|_____| |submissionVerify |MTS |6 |UA |7 |No |6 |2-Way| |__________________|_______|____|_________|____|_________|_____|_____| |deliveryVerify |UA |8 |MTS |9 |No |5 |2-Way| |__________________|_______|____|_________|____|_________|_____|_____| |getConfiguration |UA |8 |MTS |9 |No |7 |2-Way| |__________________|_______|____|_________|____|_________|_____|_____| |setConfiguration |MTS |6 |UA |7 |No |8 |2-Way| +------------------+-------+----+---------+----+---------+-----+-----+ Table 1: EMSD-P Operations Summary
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     version-minor           [0]     IMPLICIT INTEGER DEFAULT 0
   }

3.5 Submission and Delivery Procedures

Table 1 provides a comprehensive summary of EMSD-P operations, the SAP selectors used and the operation IDs used. Submission The semantics of a submission operation is Exactly Once. Exactly Once means that every operation is carried out exactly one time, no more and no less. This semantic can not be fully implemented because, if after invoking the operation, an invoker has a Success (e.g. result) indication and the performer has a FAILURE.indication, and the network goes down, the result of the operation will be Zero (and not Exactly Once). No more than one is controlled and guaranteed by the performer by using the Duplicate Operation Detection Support Functions (see the chapter entitled Duplicate Operation Detection Support). Not zero but one is realized by performer by using the SubmissionVerify operation. When the performer receives FAILURE.indication, it's responsibility is to resolve the case by using SubmissionVerify resulting in Not zero but one. Submission procedure is as follows: o Submit operation with 3-Way handshake and Duplicate Operation Detection Support Function is invoked. o If performer at EMSD-SA receives FAILURE.indication, it invokes SubmissionVerify. o Message is sent out by EMSD-SA only if result operation is confirmed or the operation is verified (in the case of FAILURE.indication). The semantic of SubmissionVerify operation is At Least Once. This type of semantics corresponds to the case that invoker keeps trying over and over until it gets a proper reply. This operation can be performed more than once without any harm.
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   Implications:

      o MTS sends out the message if and only if it's sure that UA knows
        about it.


   Delivery

   The semantics of Deliver operation is Exactly Once.  Exactly Once
   means that every operation is carried out exactly one time, no more
   and no less.  This semantic can not be fully implemented and if after
   invoking the operation, invoker has Success indication and performer
   has FAILURE.indication, and the network goes down, the result of the
   operation will be Zero (and not Exactly Once).

   No more than one is controlled and guaranteed by performer and by
   using the Duplicate Operation Detection Support Functions.

   Not zero but one is realized by performer by using the DeliveryVerify
   operation.  When performer receives FAILURE.indication, it's
   responsible to resolve the case by using DeliveryVerify resulting in
   Not zero but one.

   Delivery procedure is as follows:

      o Deliver operation with 3-Way handshake is invoked.

      o If performer at User Agent (device) receives FAILURE.indication,
        it invokes DeliveryVerify.

   The semantic of DeliveryVerify operation is At Least Once.  This type
   of semantics corresponds to the case that invoker keeps trying over
   and over until it gets a proper reply.  This operation can be
   performed more than once without any harm.

   Implications:

      o A non-delivery report is sent by MTS only if the message is not
        delivered.

      o The UA is responsible for notifying the MTS (through an explicit
        deliveryVerify) to make sure that a delivery report is sent out.


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