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RFC 3868

 
 
 

Signalling Connection Control Part User Adaptation Layer (SUA)

Part 3 of 5, p. 56 to 92
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prevText      Top      Up      ToC       Page 56 
3.7.  SUA Management Messages

   These messages are used for managing SUA and the representations of
   the SCCP subsystems in the SUA layer.

3.7.1.  Error (ERR)

   The ERR message is sent between two SUA peers to indicate an error
   situation.  The Diagnostic Information parameter is optional,
   possibly used for error logging and/or debugging.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x000C         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Error Code                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0006          |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       Routing Context                         /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0012          |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Mask     |                 Affected PC 1                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                              ...                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Mask     |                 Affected PC n                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x010D          |         Length = 8            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Network Appearance                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0007         |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                        Diagnostic Info                        /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Parameters
     Error Code                    Mandatory
     Routing Context               Mandatory *1
     Network Appearance            Mandatory *1
     Affected Point Code           Mandatory *1
     Diagnostic Information        Optional

   Note 1:    Only mandatory for specific error codes.

3.7.2.  Notify (NTFY)

   The Notify message used to provide an autonomous indication of SUA
   events to an SUA peer.

    0                     1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x000D         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Status                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Tag = 0x0011       |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        ASP Identifier                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   |          Tag = 0x0006         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       Routing Context                         /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0004         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                          Info String                          /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The NTFY message contains the following parameters:

   Parameters
     Status                        Mandatory
     ASP Identifier                Optional *1
     Routing Context               Optional
     Info String                   Optional

   Note 1:    ASP Identifier MUST be used where the IPSP/SGP cannot
              identify the ASP by provisioned address/port number
              information (e.g., where an ASP is resident on a Host
              using dynamic address/port number assignment).

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3.8.  Routing Key Management (RKM) Messages

3.8.1.  Registration Request (REG REQ)

   The REG REQ message is sent by an ASP to indicate to a remote SUA
   peer that it wishes to register one or more given Routing Keys with
   the remote peer.  Typically, an ASP would send this message to an
   SGP, and expects to receive a REG RSP message in return with an
   associated Routing Context value.

   The format for the REG REQ message is as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x010E         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                         Routing Key 1                         /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                              ...                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x010E         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                         Routing Key n                         /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Tag = 0x0109       |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        ASP Capabilities                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The REG REQ message contains the following parameters:

   Parameters
     Routing Key                   Mandatory *1
     ASP Capabilities              Optional

   Note 1:   One or more Routing Key parameters MAY be included in a
             single REG REQ message.

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3.8.2.  Registration Response (REG RSP)

   The REG RSP message is sent by an SG to an ASP indicate the result of
   a previous REG REQ from an ASP.  It contains indications of
   success/failure for registration requests and returns a unique
   Routing Context value for successful registration requests, to be
   used in subsequent SUA Traffic Management protocol messages.

   The format for the REG RSP message is as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0014         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Registration Result 1                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                              ...                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0014         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Registration Result n                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The REG RSP message contains the following parameters:

   Parameters
     Registration Result           Mandatory *1

   Note 1:   One or more Registration Result parameters MAY be included
             in a single REG RSP message.  The number of results in a
             single REG RSP message can be anywhere from one to the
             total number of Routing Key parameters found in the
             corresponding REG REQ message.

3.8.3.  Deregistration Request (DEREG REQ)

   The DEREG REQ message is sent by an ASP to indicate to a remote SUA
   peer that it wishes to deregister a given Routing Key.  Typically, an
   ASP would send this message to an SGP, and expects to receive a DEREG
   RSP message in return with the associated Routing Context value.

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   The format for the DEREG REQ message is as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0006            |           Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       Routing Context                         /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The DEREG REQ message contains the following parameters:

   Parameters
     Routing Context               Mandatory

3.8.4.  Deregistration Response (DEREG RSP)

   The DEREG RSP message is used as a response to the DEREG REQ message
   from a remote SUA peer.

   The format for the DEREG RSP message is as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0015         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Deregistration Result 1                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                              ...                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0015         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Deregistration Result n                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The DEREG RSP message contains the following parameters:

   Parameters
     Deregistration Result         Mandatory *1

   Note 1:    One or more Deregistration Result parameters MAY be
              included in one DEREG RSP message.  The number of results
              in a single DEREG RSP message can be anywhere from one to
              the total number of Routing Context parameters found in
              the corresponding DEREG REQ message.

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3.9.  Common Parameters

   These TLV parameters are common across the different adaptation
   layers.

   Parameter Name                     Parameter ID
   ==============                     ============
   Reserved                             0x0000
   Not used in SUA                      0x0001
   Not used in SUA                      0x0002
   Not used in SUA                      0x0003
   Info String                          0x0004
   Not used in SUA                      0x0005
   Routing Context                      0x0006
   Diagnostic Info                      0x0007
   Not used in SUA                      0x0008
   Heartbeat Data                       0x0009
   Not Used in SUA                      0x000A
   Traffic Mode Type                    0x000B
   Error Code                           0x000C
   Status                               0x000D
   Not used in SUA                      0x000E
   Not used in SUA                      0x000F
   Not used in SUA                      0x0010
   ASP Identifier                       0x0011
   Affected Point Code                  0x0012
   Correlation ID                       0x0013
   Registration Result                  0x0014
   Deregistration Result                0x0015
   Registration Status                  0x0016
   Deregistration Status                0x0017
   Local Routing Key Identifier         0x0018

3.9.1.  Not Used

   Use of Parameter ID 0x0001 in SUA messages is not supported.

3.9.2.  Not Used

   Use of Parameter ID 0x0002 in SUA messages is not supported.

3.9.3.  Not Used

   Use of Parameter ID 0x0003 in SUA messages is not supported.

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3.9.4.  Info String

   The optional INFO String parameter can carry any meaningful UTF-8
   [3629] character string along with the message.  Length of the INFO
   String parameter is from 0 to 255 octets.  No procedures are
   presently identified for its use but service providers may use the
   INFO String for debugging purposes.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0004         |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                          Info String                          /

   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.9.5.  Not Used in SUA

   Use of Parameter ID 0x0005 in SUA messages is not supported.

3.9.6.  Routing Context

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0006         |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       Routing Context                         /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Routing Context parameter contains (a list of) 4-byte unsigned
   integers indexing the Application Server traffic that the sending ASP
   is configured/registered to receive.  There is a one-to-one
   relationship between an index entry and a Routing Key or AS Name.

   An Application Server Process may be configured to process traffic
   for more than one logical Application Server.  From the perspective
   of an ASP, a Routing Context defines a range of signalling traffic
   that the ASP is currently configured to receive from the SG.

   Additionally, the Routing Context parameter identifies the SS7
   network context for the message, for the purposes of logically
   separating the signalling traffic between the SGP and the Application
   Server Process over a common SCTP Association, when needed.  An
   example is where an SGP is logically partitioned to appear as an

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   element in several different national SS7 networks.  It implicitly
   defines the SS7 Point Code format used, the SS7 Network Indicator
   value and SCCP protocol type/variant/version used within a separate
   SS7 network.  It also defines the network context for the PC and SSN
   values.  Where an SGP operates in the context of a single SS7
   network, or individual SCTP associations are dedicated to each SS7
   network context, this functionality is not needed.

   If the Routing Context parameter is present, it SHOULD be the first
   parameter in the message as it defines the format and/or
   interpretation of the parameters containing a PC or SSN value.

3.9.7.  Diagnostic Information

   The Diagnostic Information can be used to convey any information
   relevant to an error condition, to assist in the identification of
   the error condition.  In the case of an Adaptation Layer Identifier
   or Traffic Handling Mode, the Diagnostic Information includes the
   received parameter.  In the other cases, the Diagnostic information
   may be the first 40 bytes of the offending message.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0007          |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                     Diagnostic Information                    /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.9.8.  Not Used

   Parameter ID 0x0008 is not used in SUA.

3.9.9.  Heartbeat Data

   The sending node defines the Heartbeat Data field contents.  It may
   include a Heartbeat Sequence Number and/or Timestamp, or other
   implementation specific details.

   The receiver of a Heartbeat message does not process this field as it
   is only of significance to the sender.  The receiver echoes the
   content of the Heartbeat Data in a BEAT-Ack message.

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0009          |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       Heartbeat Data                          /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The data field can be used to store information in the heartbeat
   message useful to the sending node (e.g., the data field can contain
   a time stamp, a sequence number, etc.).

3.9.10.  Not Used

   Parameter ID 0x000A is not used in SUA.

3.9.11.  Traffic Mode Type

   The Traffic Mode Type parameter identifies the traffic mode of
   operation of the ASP within an AS.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x000B         |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Traffic Mode Type                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The valid values for Type are shown in the following table.

      1         Override
      2         Loadshare
      3         Broadcast

   Within a Routing Context, Override, Loadshare Types and Broadcast
   cannot be mixed.  The Override value indicates that the ASP is
   operating in Override mode, and the ASP wishes to take over all
   traffic for an Application Server (i.e., primary/backup operation),
   overriding any currently active ASP in the AS.  In Loadshare mode,
   the ASP wishes to share in the traffic distribution with any other
   currently active ASPs.  In Broadcast mode, the ASP wishes to receive
   the same traffic as any other currently active ASPs.  When there are
   insufficient ASPs, the sender may immediately move the ASP to Active.

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3.9.12.  Error Code

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Tag =0x000C            |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Error Code                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Error Code parameter indicates the reason for the Error Message.
   The Error parameter value can be one of the following values:

      0x01      Invalid Version
      0x02      Not Used in SUA
      0x03      Unsupported Message Class
      0x04      Unsupported Message Type
      0x05      Unsupported Traffic Handling Mode
      0x06      Unexpected Message
      0x07      Protocol Error
      0x08      Not used in SUA
      0x09      Invalid Stream Identifier
      0x0a      Not used in SUA
      0x0b      Not used in SUA
      0x0c      Not used in SUA
      0x0d      Refused - Management Blocking
      0x0e      ASP Identifier Required
      0x0f      Invalid ASP Identifier
      0x10      Not Used in SUA
      0x11      Invalid Parameter Value
      0x12      Parameter Field Error
      0x13      Unexpected Parameter
      0x14      Destination Status Unknown
      0x15      Invalid Network Appearance
      0x16      Missing Parameter
      0x17      Not Used in SUA
      0x18      Not Used in SUA
      0x19      Invalid Routing Context
      0x1a      No Configured AS for ASP
      0x1b      Subsystem Status Unknown
      0x1c      Invalid loadsharing label

   The "Invalid Version" error is sent if a message was received with an
   invalid or unsupported version.  The Error message contains the
   supported version in the Common header.  The Error message could
   optionally provide the unsupported version in the Diagnostic
   information area.

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   The "Unsupported Message Class" error is sent if a message with an
   unexpected or unsupported Message Class is received.

   The "Unsupported Message Type" error is sent if a message with an
   unexpected or unsupported Message Type is received.

   The "Unsupported Traffic Handling Mode" error is sent by a SGP if an
   ASP sends an ASP Active message with an unsupported Traffic Mode Type
   or a Traffic Mode Type that is inconsistent with the presently
   configured mode for the Application Server.  An example would be a
   case in which the SGP did not support loadsharing.

   The "Unexpected Message" error MAY be sent if a defined and
   recognized message is received that is not expected in the current
   state (in some cases the ASP may optionally silently discard the
   message and not send an Error message).  For example, silent discard
   is used by an ASP if it received a DATA message from an SGP while it
   was in the ASP-INACTIVE state.  If the Unexpected message contained
   Routing Context(s), the Routing Context(s) SHOULD be included in the
   Error message.

   The "Protocol Error" error is sent for any protocol anomaly (i.e.,
   reception of a parameter that is syntactically correct but unexpected
   in the current situation.

   The "Invalid Stream Identifier" error is sent if a message is
   received on an unexpected SCTP stream.

   The "Refused - Management Blocking" error is sent when an ASP Up or
   ASP Active message is received and the request is refused for
   management reasons (e.g., management lockout").  If this error is in
   response to an ASP Active message, the Routing Context(s) in the ASP
   Active message SHOULD be included in the Error message.

   The "ASP Identifier Required" is sent by a SGP in response to an ASP
   Up message that does not contain an ASP Identifier parameter when the
   SGP requires one.  The ASP SHOULD resend the ASP Up message with an
   ASP Identifier.

   The "Invalid ASP Identifier" is send by a SGP in response to an ASP
   Up message with an invalid ASP Identifier.

   The "Invalid Parameter Value" error is sent if a message is received
   with an invalid parameter value (e.g., a DUPU message was received
   with a Mask value other than "0".

   The "Parameter Field Error" would be sent if a message is received
   with a parameter having a wrong length field.

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   The "Unexpected Parameter" error would be sent if a message contains
   an invalid parameter.

   The "Invalid Network Appearance" error is sent by a SGP if an ASP
   sends a message with an invalid (not configured) Network Appearance
   value.  For this error, the invalid (not configured) Network
   Appearance MUST be included in the Network Appearance parameter.

   The "Missing Parameter" error would be sent if a mandatory parameter
   were not included in a message.

   The "Invalid Routing Context" error would be sent by a SG if an ASP
   sends a message with an invalid (not configured) Routing Context
   value.  For this error, the invalid (not configured) Routing
   Context(s) MUST be included in the Routing Context parameter.

   The "No Configured AS for ASP" error is sent if a message is received
   from a peer without a Routing Context parameter and it is not known
   by configuration data, which Application Servers are referenced.

   The "Destination Status Unknown" Error MAY be sent if a DAUD is
   received at an SG inquiring of the availability or congestion status
   of a destination, and the SG does not wish to provide the status
   (e.g., the sender is not authorized to know the status).  For this
   error, the invalid or unauthorized Point Code(s) MUST be included
   along with the Network Appearance and Routing Context associated with
   the Point Code(s).

   The "Subsystem Status Unknown" Error MAY be sent if a DAUD is
   received at an SG inquiring of the availability or congestion status
   of a subsystem, and the SG does not wish to provide the status (e.g.,
   the sender is not authorized to know the status).  For this error,
   the invalid or unauthorized Point Code and Subsystem Number MUST be
   included along with the Network Appearance and Routing Context
   associated with the Point Code and Subsystem Number.

3.9.13.  Status

   The Status parameter identifies the type of the status that is being
   notified and the Status ID.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x000D         |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Status Type           |            Status ID          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   The valid values for Status Type (16 bit unsigned integer) are:

      1     Application Server state change (AS_State_Change)
      2     Other

   The Status ID parameter contains more detailed information for the
   notification, based on the value of the Status Type.

   If the Status Type is AS_STATE_CHANGE, then the Status ID (16 bit
   unsigned integer) values are:

      1    reserved
      2    Application Server Inactive (AS-Inactive)
      3    Application Server Active (AS-Active)
      4    Application Server Pending (AS-Pending)

   These notifications are sent from an SGP to an ASP upon a change in
   status of a particular Application Server.  The value reflects the
   new state of the Application Server.

   If the Status Type is "Other", then the following Status Information
   values are defined:

      1    Insufficient ASP resources active in AS
      2    Alternate ASP Active
      3    ASP failure

   These notifications are not based on the SGP reporting the state
   change of an ASP or AS.  In the Insufficient ASP Resources case, the
   SGP is indicating to an "Inactive" ASP(s) in the AS that another ASP
   is required to handle the load of the AS (Loadsharing mode or
   Broadcast mode).  For the Alternate ASP Active case, an ASP is
   informed when an alternate ASP transitions to the ASP-Active state in
   Override mode.

3.9.14.  Not Used in SUA

   Parameter ID 0x000E is not used in SUA.

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3.9.15.  Not Used in SUA

   Parameter ID 0x000F is not used in SUA.

3.9.16.  Not Used in SUA

   Parameter ID 0x0010 is not used in SUA.

3.9.17.  ASP Identifier

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0011          |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        ASP Identifier                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   ASP Identifier field: 32-bits (unsigned integer)

   The ASP Identifier field contains a unique value that is locally
   significant among the ASPs that support an AS.  The SGP should save
   the ASP Identifier to be used, if necessary, with the Notify message
   (see Section 3.7.2).

3.9.18.  Affected Point Code

   The Affected Point Code Destinations parameter contains a list of
   Affected Point Code fields, each a three-octet parameter to allow for
   14-, 16- and 24-bit binary formatted SS7 Point Codes.  Affected Point
   Codes that are less than 24-bits are padded on the left to the 24-bit
   boundary.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0012         |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Mask       |                 Affected PC 1                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                             . . .                             /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The encoding is shown below for ANSI and ITU Point Code examples.

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   ANSI 24-bit Point Code:

    0                   1                   2                   3-->
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Mask      |    Network    |    Cluster    |     Member    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |MSB-----------------------------------------LSB|

   ITU 14-bit Point Code:

    0                   1                   2                   3-->
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Mask      |0 0 0 0 0 0 0 0 0 0|Zone |     Region    | SP  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                        |MSB--------------------LSB|

   It is OPTIONAL for an implementation to generate an Affected Point
   Code parameter with more than on Affected PC but the implementation
   MUST accept and process an Affected Point Code parameter with more
   than one Affected PC.

   Mask: 8-bits

   The Mask parameter can be used to identify a contiguous range of
   Affected Destination Point Codes, independent of the point code
   format.  Identifying a contiguous range of Affected PCs may be useful
   when reception of an MTP3 management message or a linkset event
   simultaneously affects the availability status of a series of
   destinations at an SG.

   The Mask parameter is an integer representing a bit mask that can be
   applied to the related Affected PC field.  The bit mask identifies
   how many bits of the Affected PC field are significant and which are
   effectively "wild-carded".  For example, a mask of "8" indicates that
   the last eight bits of the PC is "wild-carded".  For an ANSI 24-bit
   Affected PC, this is equivalent to signalling that all PCs in an ANSI
   Cluster are unavailable.  A mask of "3" indicates that the last three
   bits of the PC is "wild-carded".  For a 14-bit ITU Affected PC, this
   is equivalent to signalling that an ITU Region is unavailable.

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3.9.19.  Correlation ID

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0013         |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Correlation ID                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Correlation ID is a 32-bit identifier that is attached to CLDT
   messages to indicate to a newly entering ASP in a Broadcast AS where
   in the traffic flow of CLDT messages the ASP is joining.  It is
   attached to the first CLDT message sent to an ASP by an SG after
   sending an ASP Active Ack or otherwise starting traffic to an ASP.
   The Correlation ID is only significant within a Routing Context.

   Implementation note: Correlation ID parameter can be used for
   features like Synchronisation of ASPs/SGPs in a Broadcast Mode AS/SG;
   avoid message duplication and mis-sequencing in case of failover of
   association from one ASP/SGP to other ASP/SGP etc.

3.9.20.  Registration Result

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0018         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Routing Key Identifier                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0016         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Registration Status                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0006         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Routing Context                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Routing Key Identifier contains the same TLV formatted parameter
   value as found in the matching Routing Key parameter in the REG REQ
   message.

   Routing Context contains the same TLV formatted Routing Context
   parameter for the associated Routing Key if the registration was
   successful.  It is set to "0" if the registration was not successful.

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3.9.21.  Deregistration Result

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0006         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Routing Context                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0017         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Deregistration Status                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Routing Context: 32-bit integer

      Routing Context contains the Routing Context value of the matching
      Routing key to deregister, as found in the DEREG REQ message.

   Deregistration Status: 32-bit integer

      Deregistration Status parameter indicates the success or the
      reason for failure of the deregistration.

3.9.22.  Registration Status

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Tag = 0x0016      |          Length = 8             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Registration Status                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Registration Status: 32-bits (unsigned integer)

      The Registration Status field indicates the success or the reason
      for failure of a registration request.

   Its values may be:
             0           Successfully Registered
             1           Error - Unknown
             2           Error - Invalid Destination Address
             3           Error - Invalid Network Appearance
             4           Error - Invalid Routing Key
             5           Error - Permission Denied
             6           Error - Cannot Support Unique Routing
             7           Error - Routing Key not Currently Provisioned

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             8           Error - Insufficient Resources
             9           Error - Unsupported RK parameter Field
            10           Error - Unsupported/Invalid Traffic Mode Type
            11           Error - Routing Key Change Refused

3.9.23.  Deregistration Status

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Tag = 0x0017      |          Length = 8             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Deregistration Status                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Deregistration Status: 32-bit integer

   The Deregistration Result Status field indicates the success or the
   reason for failure of the deregistration.

   Its values may be:

   0           Successfully Deregistered
   1           Error - Unknown
   2           Error - Invalid Routing Context
   3           Error - Permission Denied
   4           Error - Not Registered
   5           Error - ASP Currently Active for Routing Context

3.9.24.  Local Routing Key Identifier

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Tag = 0x0018        |        Length = 8             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Local Routing Key Identifier                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Local Routing Key Identifier field is a 32-bits unsigned integer.
   The Identifier value is assigned by the ASP and is used to correlate
   the response in a REG RSP message with the original registration
   request.  The Identifier value must remain unique until the REG RSP
   message is received.

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3.10.  SUA-Specific parameters

   These TLV parameters are specific to the SUA protocol.

   Parameter Name                     Parameter ID
   ==============                     ============
   SS7 Hop Counter                      0x0101
   Source Address                       0x0102
   Destination Address                  0x0103
   Source Reference Number              0x0104
   Destination Reference Number         0x0105
   SCCP Cause                           0x0106
   Sequence Number                      0x0107
   Receive Sequence Number              0x0108
   ASP Capabilities                     0x0109
   Credit                               0x010A
   Data                                 0x010B
   User/Cause                           0x010C
   Network Appearance                   0x010D
   Routing Key                          0x010E
   DRN Label                            0x010F
   TID Label                            0x0110
   Address Range                        0x0111
   SMI                                  0x0112
   Importance                           0x0113
   Message Priority                     0x0114
   Protocol Class                       0x0115
   Sequence Control                     0x0116
   Segmentation                         0x0117
   Congestion Level                     0x0118

   Destination/Source Address Sub-Parameters
   ===========================================
   Global Title                         0x8001
   Point Code                           0x8002
   Subsystem Number                     0x8003
   IPv4 Address                         0x8004
   Hostname                             0x8005
   IPv6 Addresses                       0x8006

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3.10.1.  SS7 Hop counter

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0101          |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Reserved                         | SS7 Hop Count |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   SS7 Hop Counter (3.18/Q.713)

   The value of the SS7 Hop Counter is decremented with each global
   title translation and is in the range 15 to 1.

3.10.2.  Source Address

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0102         |      Parameter Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Routing Indicator        |       Address Indicator       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       Address parameter(s)                    /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The following combinations of address parameters are valid:

   -  Global Title (e.g., E.164 number) + optional PC and/or SSN, SSN
      may be zero, when routing is done on Global Title

   -  SSN (non-zero) + optional PC and/or Global Title, when routing is
      done on PC + SSN.  The PC is mandatory in the source address when
      sending from SGP to ASP, and in the destination address when
      sending from ASP to SGP to reach the SS7 SEP.

   -  Hostname + optional SSN, when routing is done by Hostname

   -  SSN (non-zero) and optional IP address (IPv4 or IPv6) when routing
      is done on IP address + SSN

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3.10.2.1.  Routing Indicator

   The following values are valid for the routing indicator:

      Reserved                      0
      Route on Global Title         1
      Route on SSN + PC             2
      Route on Hostname             3
      Route on SSN + IP Address     4

   The routing indicator determines which address parameters need to be
   present in the address parameters field.

3.10.2.2.  Address Indicator

   This parameter is needed for interworking with SS7 networks.  The
   address indicator specifies what address parameters are actually
   received in the SCCP address from the SS7 network, or are to be
   populated in the SCCP address when the message is sent into the SS7
   network.  The value of the routing indicator needs to be taken into
   account.  It is used in the ASP to SG direction.  For example, the PC
   parameter is present in the destination address of the CLDT sent from
   ASP->SG, but bit 2 is set to "0" meaning "do not populate this in the
   SCCP called party address".  The effect is that the SG only uses the
   PC to populate the MTP routing label DPC field, but does not include
   it in the SCCP called party address.

   In the SG->ASP direction, the source address PC parameter is present
   (PC of SS7 SEP).  However, this may have been populated from the OPC
   in the received MTP routing label, not from the PC field in the SCCP
   calling party address.  In this case, bit 2 = "0" denotes that.  The
   AI gives further instructions to the SG how and when to populate the
   SCCP addresses; in the SG->ASP direction, the AI gives information to
   the ASP as to what was actually present in the received SCCP
   addresses.

   The address indicator is coded as follows:

   Bit 1 is used to indicate inclusion of the SSN

   0         Do not include SSN when optional
    1         Include SSN

   Bit 2 is used to indicate inclusion of the PC

   0         Do not include PC, regardless of the routing indicator
             value
    1        Include PC

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   Bit 3 is used to indicate inclusion of the Global Title

   0         Do not include GT when optional (routing indicator /= 1)
    1        Include GT

   The remaining bits are spare and SHOULD be coded zero, and MUST be
   ignored by the receiver.

3.10.2.3.  Global Title

   0                 1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x8001          |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Reserved                       |      GTI      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   No. Digits  | Trans. type   |    Num. Plan  | Nature of Add |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                         Global Title Digits                   /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Number of Digits:

   This is the number of digits contained in the Global Title.

   GTI (Global Title Indicator, defined in chapter 3.4.2.3 of Q.713).

   0000     Invalid
   0001     Nature of Address is taken over. It is implicitly assumed
             that the Translation Type = Unknown and Numbering Plan =
             E.164 (value 1).
   0010     This is most commonly used in North American networks.
             The Translation Type implicitly determines Nature of
             Address and Numbering Plan.  This data can be configured
             in the SG.  The number of digits is always even and
             determined by the SCCP address length.
   0011     Numbering Plan and Translation Type are taken over.  It is
             implicitly assumed that the Nature of Address = Unknown.
   0100     This format is used in international networks and most
             commonly in networks outside North America.  All
             information to populate the source address is present in
             the SCCP Address.

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   Translation type:

   0              Unknown
   1 - 63         International services
   64 - 127       Spare
   128 - 254      National network specific
   255            Reserved

   Numbering Plan:

   0         unknown
   1         ISDN/telephony numbering plan (Recommendations E.163 and
             E.164)
   2         generic numbering plan
   3         data numbering plan (Recommendation X.121)
   4         telex numbering plan (Recommendation F.69)
   5         maritime mobile numbering plan (Recommendations E.210,
             E.211)
   6         land mobile numbering plan (Recommendation E.212)
   7         ISDN/mobile numbering plan (Recommendation E.214)
   8 - 13    spare
   14        private network or network-specific numbering plan
   15 - 126  spare
   127       reserved.

   Nature of Address:

   0         unknown
   1         subscriber number
   2         reserved for national use
   3         national significant number
   4         international number
   5 - 255   Spare

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   Global Title:

   Octets contain a number of address signals and possibly filler as
   shown:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |2 addr.|1 addr.|4 addr.|3 addr.|6 addr.|5 addr.|8 addr.|7 addr.|
   |  sig. | sig.  |  sig. | sig.  |  sig. | sig.  |  sig. | sig.  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        .............          |filler |N addr.|   filler      |
   |                               |if req | sig.  |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   All filler bits SHOULD be set to 0.

   Address signals to be coded as defined in ITU-T Q.713 Section
   3.4.2.3.1.

3.10.2.4.  Point Code

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x8002          |            Length = 8         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            Point Code                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See chapter 3.9.18 Affected Point Code for the layout of the Point
   Code field.

3.10.2.5.  Subsystem Number

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x8003          |            Length = 8         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Reserved                      |   SSN value   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The internationally standardized SSN values are described in chapter
   3.4.2.2 of Q.713.

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3.10.2.6.  IP Addresses

   The IP address formats can use different tags.  It should be noted
   that if the source address is in a certain IP version, the
   destination address should also be in the same IP version.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Tag = 0x8004/0x8006      |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                        IPv4 or IPv6 Address                   /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note:    The tag value 0x8004 is for an IPv4 address and 0x8006 is
            for IPv6.

3.10.2.7.  Hostname

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x8005          |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                           Host Name                           /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Host Name: variable length

   This field contains a host name in "host name syntax" per RFC 1123
   Section 2.1 [1123].  The method for resolving the host name is out of
   scope for this document.

   Note:    At least one null terminator is included in the Host Name
            string and must be included in the length.

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3.10.3.  Destination Address

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0103         |      Parameter Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Routing Indicator        |       Address Indicator       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       Address Parameter(s)                    /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The format of this parameter is identical to the Source Address
   parameter.

3.10.4.  Source Reference Number

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0104         |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   Source Reference Number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The source reference number is a 4 octet long integer.  This is
   allocated by the source SUA instance.

3.10.5.  Destination Reference Number

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0105         |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Destination Reference Number                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The destination reference number is a 4 octet long integer.  This is
   allocated by the destination SUA instance.

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3.10.6.  SCCP Cause

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0106          |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Reserved              |   Cause Type  |  Cause Value  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This parameter bundles the SCCP parameters Release cause, Return
   cause, Reset cause, Error cause and Refusal cause.

   Cause Type can have the following values:

      Return Cause          0x1
      Refusal Cause         0x2
      Release Cause         0x3
      Reset Cause           0x4
      Error Cause           0x5

   Cause Value contains the specific cause value.  Below gives examples
   for ITU SCCP values.  ANSI references can be found in ANSI T1.112.3

   Cause value in        Correspondence with Reference
   SUA message           SCCP parameter
   ------------------    -----------------   ---------
   CLDR                  Return Cause        ITU-T Q.713 Chap 3.12
   COREF                 Refusal Cause       ITU-T Q.713 Chap 3.15
   RELRE                 Release Cause       ITU-T Q.713 Chap 3.11
   RESRE                 Reset Cause         ITU-T Q.713 Chap 3.13
   ERR                   Error Cause         ITU-T Q.713 Chap 3.14

3.10.7.  Sequence Number

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0107         |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Reserved              |  Rec Seq Num|M| Sent Seq Num  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This parameter is used to indicate whether "more" data will follow in
   subsequent CODT messages, and/or to number each CODT message
   sequentially for the purpose of flow control.  It contains the
   received as well as the sent sequence number, P(R) and P(S) in Q.713,
   chapters 3.7 and 3.9.

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   As such it can also be used to acknowledge the receipt of data
   transfers from the peer in case of protocol class 3.

   Sent Sequence Number is one octet and is coded as follows:

      Bits 2-8 are used to indicate the Send Sequence Number P(S).
      Bit 1 (LSB) of octet 1 is spare.

   Received Sequence Number is one octet, and is coded as follows:

      Bits 2-8 are used to indicate the Received Sequence Number
      P(R).
      Bit 1 (LSB) is used for the more data indication, as follows:

      0         no more data
      1         more data

3.10.8.  Receive Sequence Number

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0108         |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Reserved                   |  Rec Seq Num  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This parameter is used exclusively for protocol class 3 in the data
   acknowledgement message to indicate the lower edge of the receiving
   window.  See Q.713, chapter 3.9.

   It is a 1 octet long integer coded as follows:

      Bits 8-2 are used to indicate the Received Sequence Number P(R).

      Bit 1 is spare.

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3.10.9.  ASP Capabilities

   This parameter is used so that the ASP can report its capabilities
   regarding SUA for supporting different protocol classes and
   interworking scenarios.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0109         |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Reserved              |0 0 0 0|a|b|c|d| Interworking  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Flags

     a - Protocol Class 3
     b - Protocol Class 2
     c - Protocol Class 1
     d - Protocol Class 0

   It is mandatory to support at least Protocol Class 0.

   Interworking

   Values

     0x0 indicates no interworking with SS7 Networks.
     0x1 indicates IP Signalling Endpoint (ASP), interworking with SS7
        networks.
     0x2 indicates Signalling Gateway.
     0x3 indicates relay node support.

3.10.10.  Credit

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x010A         |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Reserved                     |     Credit     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The length of the credit field is one octet.  See ITU-T Q.713 Chapter
   3.10.  The parameter is used for protocol class 3 exclusively.

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3.10.11.  Data

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x010b         |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                             Data                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Data parameter field contains the SS7 SCCP-User application
   message, for example an INAP/TCAP message.

3.10.12.  User/Cause

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x010c          |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Cause             |            User               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   "User" is coded to that SCCP's SI value.  There may be several SCCP's
   at a given point code, each with different SI values, although
   normally there is only one with SI = 3.

   Cause may take the following values

   0    remote SCCP unavailable, reason unknown;
   1    remote SCCP unequipped;
   2    remote SCCP inaccessible;

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3.10.13.  Network Appearance

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x010D          |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Network Appearance                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Network Appearance field: 32-bits (unsigned integer)

      The Network Appearance field identifies the SS7 network context
      for the Routing Key.  The Network Appearance value is of local
      significance only, coordinated between the SG and ASP.  Therefore,
      in the case where the ASP is connected to more than one SG, the
      same SS7 Network context may be identified by different Network
      Appearance values depending upon to which SG the ASP is
      registering.

      In the Routing Key, the Network Appearance identifies the SS7
      Point Code and Global Title Translation Type format used, and the
      SCCP and possibly the SCCP-User protocol (type, variant and
      version) used within the specific SS7 network.

3.10.14.  Routing Key

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010E          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0018          |        Length = 8             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Local Routing Key Identifier                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      \                         Key parameter(s)                      \
      /                                                               /
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Local Routing Key Identifier field: 32-bits (unsigned integer)

      Key field: variable

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   The Key field contains the following parameters:

      Parameter
         Traffic Mode Type          Optional
         Network Appearance         Optional *1
         Source Address             Optional
         Destination Address        Optional
         Address Range              Optional

   Note 1:    The Network Appearance parameter must be included in the
              Routing Key when the ASP is able to register in multiple
              SS7 Network contexts.

3.10.15.  DRN Label

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x010F         |            Length = 8         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     start     |      end      |         label value           |
   +---------------+---------------+-------------------------------+

   The Start parameter is the start position of label, between 0 (LSB)
   and 23 (MSB).

   The End parameter is the end position of label, between 0 (LSB) and
   23 (MSB).

   Label value is a 16-bit integer, which is unique across an AS.

3.10.16.  TID Label

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Tag = 0x0110         |            Length = 8         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     start     |      end      |         label value           |
   +---------------+---------------+-------------------------------+

   The Start parameter is the start position of label, between 0 (LSB)
   and 31 (MSB).

   The End parameter is the end position of label, between 0 (LSB) and
   31 (MSB).

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   Label value is a 16-bit integer, which is unique across an AS.

3.10.17.  Address Range

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0111          |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   \                       Address parameter(s)                    \
   /                                                               /
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Address field:

   The Address field the following parameters:

   Parameter
     Source Address              Optional *1
     Destination Address         Optional *1

   Note 1:    The Address field must contain pairs of Source Addresses
              or pairs of Destination Addresses but MUST NOT mix Source
              Addresses with Destination Addresses in the same Address
              field.

3.10.18.  SMI

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0112          |            Length = 8         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Reserved                   |      SMI      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Subsystem Multiplicity Indicator (SMI) can have the following
   values:

   0x00       Reserved/Unknown
   0x01       Solitary
   0x02       Duplicated
   0x03       Triplicated
   0x04       Quadruplicated
   0xff       Unspecified

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3.10.19.  Importance

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0113          |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Reserved                       |   Importance  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Importance (3.19/Q.713)

   Possible values of the Importance Parameter are between 0 and 7,
   where the value of 0 indicates the least important and 7 indicates
   the most important.

3.10.20.  Message Priority (or Priority)

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0114          |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Reserved                         |  Msg Priority |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Priority

   Priority value ranges from 0 to 3.  If the Priority value has not
   been specified by the SCCP user, it should be set to 0xFF.  The SG
   MAY take the priority into account for determining the MTP message
   priority.  In the all-IP case, this parameter MAY be used.

   The Message Priority parameter is optional in the CLDT, CLDR, CORE,
   COAK and CODT messages.  However, for networks, which support Message
   Priority (e.g., ANSI), this parameter MUST be included but it is not
   required for those which don't (e.g., International).

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3.10.21.  Protocol Class

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0115          |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Reserved                         |  Protocol Cl. |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Protocol class (3.6/Q.713)

   Bits 1-2 indicate the protocol class.

      Value     Description
        0       Class 0 (connectionless service)
        1       Class 1 (connectionless service)
        2       Class 2 (connection-oriented service)
        3       Class 3 (connection-oriented service)

   Bit 8 indicates the use of the return on error procedure.

       Value     Description
        0x0      No special options
        0x1      Return message on error

   Bits 3-7 are spare and SHOULD be coded zero, and MUST be
   ignored by the receiver.

3.10.22.  Sequence Control

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0116          |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence  Control         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Sequence Control (6.2.2.2.2/Q.711)

   The field is coded with the value of the sequence control parameter
   associated with a group of messages and are chosen so as to ensure
   proper loadsharing of message groups over SLS values while ensuring
   that sequence control values within message groups have the sequence
   control value coded with the same value as the initial message of the
   message group.

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3.10.23.  Segmentation

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0117          |            Length = 32        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | first/remain  |             Segmentation Reference            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The first/remaining segments field is formatted as follows: bit 8
   (MSB): indicates whether this is the first segment (1) or not (0)

   bits 1-7: indicate the number of remaining segments, value between 0
   and 15

   The field would thus be coded 1000 0000 (first, no remaining
   segments) for a unsegmented CLDT.

   The segmentation reference field is a 3 byte integer, assigned by the
   ASP.

3.10.24.  Congestion Level

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag = 0x0118          |             Length = 8        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Congestion Level                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Congestion Level field: 8-bits (unsigned integer)

   The Congestion Level field contains the level at which congestion has
   occurred.

   When the Congestion Level parameter is included in a SCON message
   that corresponds to an N-PCSTATE primitive, the Congestion Level
   field indicates the MTP congestion level experienced by the local or
   affected signalling point as indicated by the Affected Point Code(s)
   also in the SCON message.  In this case, valid values for the
   Congestion Level field are as follows:

      0  No Congestion or Undefined
      1  Congestion Level 1
      2  Congestion Level 2
      3  Congestion Level 3

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   When the Congestion Level parameter is included in a SCON message
   that corresponds to an N-STATE primitive, the Congestion Level field
   indicates the SCCP restricted importance level experienced by the
   local or affected subsystem as indicated by the Affected Point Code
   and Subsystem Number also in the SCON message. In this case, valid
   values for the Congestion Level field range from 0 to 7, where 0
   indicates the least congested and 7 indicates the most congested
   subsystem.



(page 92 continued on part 4)

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