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INTERNET-DRAFT                                   J. Loughney (Editor)
Internet Engineering Task Force                                  Nokia
                                                         G. Sidebottom
                                                   gregside Consulting
Issued:  December 11, 2003                        L. Coene, G. Verwimp
Expires: June 10, 2003                                         Siemens
                                                             J. Keller
                                                               Tekelec
                                                           B. Bidulock
                                                   OpenSS7 Corporation

     Signalling Connection Control Part User Adaptation Layer (SUA)
                    <draft-ietf-sigtran-sua-16.txt>

Status of This Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time.  It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as 'work in progress.'


   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This draft expires on April 5, 2003.

Abstract

   This Internet Draft defines a protocol for the transport of any
   Signalling Connection Control Part-User signalling over IP using the
   Stream Control Transmission
    Protocol. The protocol is designed to be modular and symmetric, to
   allow it to work in diverse architectures, such as a Signalling
   Gateway to IP Signalling Endpoint architecture as well as a peer-to-
   peer IP Signalling Endpoint architecture.

Internet Draft                   SUA                  December 11, 2003


Abstract..............................................................1
1. Introduction.......................................................3
1.1 Scope.............................................................3
1.2 Terminology and Abbreviations.....................................3
1.3 Signalling Transport Architecture.................................6
1.4 Services Provided by the SUA Layer................................8
1.5 Internal Functions Provided in the SUA Layer.....................10
1.6 Definition of SUA Boundaries.....................................13
2 Conventions........................................................18
3 Protocol Elements..................................................18
3.1 Common Message Header............................................18
3.2 SUA Connectionless Messages......................................22
3.3 Connection Oriented Messages.....................................26
3.4 Signalling Network Management (SNM) Messages.....................37
3.5 Application Server Process State Maintenance Messages............43
3.6 ASP Traffic Maintenance Messages.................................46
3.7 SUA Management Messages..........................................49
3.8 Routing Key Management (RKM) Messages............................51
3.9 Common Parameters................................................54
3.10 SUA-Specific parameters.........................................66
4. Procedures........................................................82
4.1 Procedures to Support the SUA-User Layer.........................82
4.2 Receipt of Primitives from the Layer Management..................83
4.3 AS and ASP State Maintenance.....................................85
4.4 Routing Key Management Procedures................................98
4.5 Availability and/or Congestion Status of SS7 Destination Support101
4.6 MTP3 Restart....................................................103
4.7 SCCP - SUA Interworking at the SG...............................104
4.8 NIF Not Available on SGP...............Error! Bookmark not defined.
5 Examples of SUA Procedures........................................106
5.1 SG Architecture.................................................106
5.2 IPSP Examples...................................................107
6 Security Considerations...........................................109
7 IANA Considerations...............................................110
7.1 SCTP Payload Protocol ID........................................110
7.2 Port Number.....................................................110
7.3 Protocol Extensions.............................................110
8 Timer Values......................................................111
9 Acknowledgements..................................................111
10 Authors' Addresses...............................................112
11 References.......................................................113
11.1 Normative......................................................113
11.2 Non-Normative..................................................113
Appendix A Signalling Network Architecture..........................114
A.1 Generalized Peer-to-Peer Network Architecture...................114
A.2 Signalling Gateway Network Architecture.........................115
A.3 Signalling Gateway Message Distribution Recommendations.........116





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1. Introduction

   There is on-going integration of switched circuit networks and IP
   networks.  Network service providers are designing IP-based
   signalling architectures that need support for SS7 and SS7-like
   signalling protocols. IP provides an effective way to transport user
   data and for operators to expand their networks and build new
   services. In these networks, there is need for interworking between
   the SS7 and IP domains [2719].

   This draft defines a protocol for the transport SS7 SCCP user-
   protocols [ANSI SCCP] [ITU SCCP], such as TCAP and RANAP, over IP
   using the Stream Control Transmission Protocol (SCTP) [2960].

1.1 Scope

   This document details the delivery of SCCP-user messages (MAP & CAP
   over TCAP [ANSI TCAP] [ITU TCAP], RANAP [RANAP], etc.) messages over
   IP between two signalling endpoints.  Consideration is given for the
   transport from a signalling gateway to an IP signalling node (such
   as an IP-resident Database) as described in the Framework
   Architecture for Signalling Transport [2719]. This protocol can also
   support transport of SCCP-user messages between two endpoints wholly
   contained within an IP network.

   The delivery mechanism addresses the following criteria:

     *    Support for transfer of SCCP-User Part messages
     *    Support for SCCP connectionless service.
     *    Support for SCCP connection oriented service.
     *    Support for the operation of SCCP-User protocol peers.
     *    Support for the management of SCTP transport associations
          between signalling gateways and IP-based signalling nodes.
     *    Support for distributed IP-based signalling nodes.
     *    Support for the asynchronous reporting of status changes to
          management functions.

1.2 Terminology and Abbreviations

1.2.1 Appreviations

   CAP - CAMEL Application Protocol.

   GTT - Global Title Translation.

   MAP - Mobile Application Protocol.

   PC - Signalling System no. 7 Point Code.

   RANAP - Radio Access Network Application Protocol.

   SCTP - Stream Control Transmission Protocol.

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   SS7 - Signalling System no. 7.

   TCAP - Transaction Capabilities Application Protocol.

1.2.2 Terminology

   Signalling Gateway (SG) - Network element that terminates switched
   circuit networks and transports SCCP-User signalling over IP to an
   IP signalling endpoint.  A Signalling Gateway could be modeled as
   one or more Signalling Gateway Processes, which are located at the
   border of the SS7 and IP networks. Where an SG contains more than
   one SGP, the SG is a logical entity and the contained SGPs are
   assumed to be coordinated into a single management view to the SS7
   network and to the supported Application Servers.

   Application Server (AS) - A logical entity serving a specific
   Routing Key.  An example of an Application Server is a virtual IP
   database element handling all requests for an SCCP-user.  The AS
   contains a set of one or more unique Application Server Processes,
   of which one or more is normally actively processing traffic.

   Application Server Process (ASP) - An Application Server Process
   serves as an active or backup process of an Application Server
   (e.g., part of a distributed signalling node or database element).
   Examples of ASPs are MGCs, IP SCPs, or IP-based HLRs.  An ASP
   contains an SCTP end-point and may be configured to process traffic
   within more than one Application Server.

   IP Server Process (IPSP) - A process instance of an IP-based
   application.  An IPSP is essentially the same as an ASP, except that
   it uses SUA in a peer-to-peer fashion.  Conceptually, an IPSP does
   not use the services of a Signalling Gateway.

   Signalling Gateway Process (SGP) - A process instance of a
   Signalling Gateway.  It serves as an active, load-sharing or
   broadcast process of a Signalling Gateway.

   Signalling Process - A process instance that uses SUA to communicate
   with other signalling process.  An ASP, a SGP and an IPSP are all
   signalling processes.

   Association - An association refers to an SCTP association.  The
   association provides the transport for the delivery of SCCP-User
   protocol data units and SUA layer peer messages.

   Routing Key - The Routing Key describes a set of SS7 parameters
   and/or parameter-ranges that uniquely defines the range of
   signalling traffic configured to be handled by a particular
   Application Server. An example would be where a Routing Key consists
   of a particular SS7 SCCP SSN plus an identifier to uniquely mark the
   network that the SSN belongs to, for which all traffic would be

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   directed to a particular Application Server.  Routing Keys are
   mutually exclusive in the sense that a received SS7 signalling
   message cannot be directed to more than one Routing Key.  Routing
   Keys can be provisioned, for example, by a MIB or registered using
   SUA's dynamic registration procedures. Routing keys MUST NOT span
   multiple network appearances.

   Routing Context - An Application Server Process may be configured to
   process traffic within more than one Application Server.  In this
   case, the Routing Context parameter is exchanged between the SGP and
   the ASP (or between two ASPs), identifying the relevant Application
   Server.  From the perspective of an SGP/ASP, the Routing Context
   uniquely identifies the range of traffic associated with a
   particular Application Server, which the ASP is configured to
   receive. There is a 1:1 relationship between a Routing Context value
   and a Routing Key within an AS.  Therefore the Routing Context can
   be viewed as an index into an AS Table containing the AS Routing
   Keys.

   Address Mapping Function (AMF) - The AMF is an implementation
   dependent function that is responsible for resolving the address
   presented in the incoming SCCP/SUA message to correct SCTP
   association for the desired endpoint. The AMF MAY use routing
   context / rouging key information as selection criteria for the
   appropriate SCTP association.

   Fail-over - The capability to re-route signalling traffic as
   required to an alternate Application Server Process, or group of
   ASPs, within an Application Server in the event of failure or
   unavailability of a currently used Application Server Process.
   Fail-over may apply upon the return to service of a previously
   unavailable Application Server Process.

   Host - The computing platform that the SGP or ASP process is running
   on.

   Layer Management - Layer Management is a nodal function that handles
   the inputs and outputs between the SUA layer and a local management
   entity.

   Network Appearance - The Network Appearance is an SUA local
   reference (typically an integer) shared by SG and AS that together
   with a Signalling Point Code uniquely identifies an SS7 node by
   indicating the specific SS7 network it belongs to.

   Network Byte Order - Most significant byte first, a.k.a. Big Endian.

   Stream - A stream refers to an SCTP stream; a uni-directional
   logical channel established from one SCTP endpoint to another
   associated SCTP endpoint, within which all user messages are
   delivered in-sequence except for those submitted to the un-ordered
   delivery service.

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   Transport address - an address that serves as a source or
   destination for the unreliable packet transport service used by
   SCTP. In IP networks, a transport address is defined by the
   combination of an IP address and an SCTP port number.  Note, only
   one SCTP port may be defined for each endpoint, but each SCTP
   endpoint may have multiple IP addresses.

1.3 Signalling Transport Architecture

   The framework architecture that has been defined for switched
   circuit networks signalling transport over IP [2719] uses multiple
   components, including an IP transport protocol, a signalling common
   transport protocol and an adaptation module to support the services
   expected by a particular switched circuit networks signalling
   protocol from its underlying protocol layer.

   In general terms, the SUA architecture can be modeled as a peer-to-
   peer architecture. The first section considers the SS7 to IP
   interworking architectures for connectionless and connection-
   oriented transport.  For this case, it is assumed that the ASP
   initiates the establishment of the SCTP association with SG.

1.3.1 Protocol Architecture for Connectionless Transport

   In this architecture, the SCCP and SUA layers interface in the SG.
   Interworking between the SCCP and SUA layers is needed to provide
   for the transfer of the user messages as well as the management
   messages.

        ********   SS7   ***************   IP   ********
        * SEP  *---------*             *--------*      *
        *  or  *         *      SG     *        * ASP  *
        * STP  *         *             *        *      *
        ********         ***************        ********

        +------                                 +------+
        | SUAP |                                | SUAP |
        +------+         +------+------+        +------+
        | SCCP |         | SCCP | SUA  |        | SUA  |
        +------+         +------+------+        +------+
        | MTP3 |         | MTP3 |      |        |      |
        +------+         +------+ SCTP |        | SCTP |
        | MTP2 |         | MTP2 |      |        |      |
        +------+         +------+------+        +------+
        |  L1  |         |  L1  |  IP  |        |  IP  |
        +------+         +------+------+        +------+
            |               |         |            |
            +---------------+         +------------+

          SUAP - SCCP/SUA User Protocol (TCAP, for example)
          STP  - SS7 Signalling Transfer Point

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   See Appendix A.3.1 for operation recommendations.

1.3.1.1 SG as endpoint

   In this case, the connectionless SCCP messages are routed on point
   code (PC) and subsystem number (SSN).  The subsystem identified by
   SSN and Routing Context is regarded as local to the SG.  This means
   from SS7 point of view, the SCCP-user is located at the SG.

1.3.1.2 Signalling Gateway as relay-point

   A Global Title translation is executed at the signalling gateway,
   before the destination of the message can be determined.  The actual
   location of the SCCP-user is irrelevant to the SS7 network.  GT
   Translation yields an "SCCP entity set", from which an Application
   Server can be derived.  Selection of the Application Server is based
   on the SCCP called party address  (and possibly other SS7 parameters
   depending on the implementation).

1.3.2 Protocol Architecture for Connection-Oriented Transport

   In this architecture, the SCCP and SUA layers share an interface in
   the signalling gateway process to associate the two connection
   sections needed for the connection-oriented data transfer between
   SEP and ASP.  Both connection sections are setup when routing the
   Connect Request messages from the signalling end point via
   signalling gateway process to ASP and visa-versa.  The routing of
   the Connect Request message is performed in the same way as
   described in 1.3.1.

        ********   SS7   ***************   IP   ********
        * SEP/ *---------*      SG     *--------* ASP *
        * STP  *         *             *        *      *
        ********         ***************        ********

        +------+                                +------+
        | SUAP |                                | SUAP |
        +------+         +------+------+        +------+
        | SCCP |         | SCCP | SUA  |        | SUA  |
        +------+         +------+------+        +------+
        | MTP3 |         | MTP3 |      |        |      |
        +------|         +------+ SCTP |        | SCTP |
        | MTP2 |         | MTP2 |      |        |      |
        +------+         +------+------+        +------+
        |  L1  |         |  L1  |  IP  |        |  IP  |
        +------+         +------+------+        +------+
            |               |         |            |
            +---------------+         +------------+

          SUAP - SCCP/SUA Application Protocol (e.g. - RANAP/RNSAP)

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          STP  - SS7 Signalling Transfer Point

   See Appendix A.3.2 for operation recommendations.

1.3.3 All IP Architecture

   This architecture can be used to carry a protocol that uses the
   transport services of SCCP within an IP network.  This allows
   flexibility in developing networks, especially when interaction
   between legacy signalling is not needed.  The architecture removes
   the need for signalling gateway functionality.

          ********   IP   ********
          * IPSP *--------* IPSP *
          ********        ********

          +------+        +------+
          | SUAP |        | SUAP |
          +------+        +------+
          | SUA  |        | SUA  |
          +------+        +------+
          | SCTP |        | SCTP |
          +------+        +------+
          |  IP  |        |  IP  |
          +------+        +------+
             |                |
             +----------------+

       SUAP - SCCP/SUA Application Protocol (e.g. - RANAP/RNSAP)

1.3.4 ASP Fail-over Model and Terminology

   The SUA protocol supports ASP fail-over functions to support a high
   availability of transaction processing capability.

   An Application Server can be considered as a list of all ASPs
   configured/registered to handle SCCP-user messages within a certain
   range of routing information, known as a Routing Key.  One or more
   ASPs in the list may normally be active to handle traffic, while
   others may be inactive but available in the event of failure or
   unavailability of the active ASP(s).

   For operation recommendations, see Appendix A.

1.4 Services Provided by the SUA Layer

1.4.1 Support for the transport of SCCP-User Messages

   The SUA supports the transfer of SCCP-user messages. The SUA layer
   at the signalling gateway and at the ASP support the seamless
   transport of user messages between the signalling gateway and the
   ASP.

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1.4.2 SCCP Protocol Class Support

   Depending upon the SCCP-users supported, the SUA supports the 4
   possible SCCP protocol classes transparently.  The SCCP protocol
   classes are defined as follows:

     *    Protocol class 0 provides unordered transfer of SCCP-user
          messages in a connectionless manner.

     *    Protocol class 1 allows the SCCP-user to select the in-
          sequence delivery of SCCP-user messages in a connectionless
          manner.

     *    Protocol class 2 allows the bi-directional transfer of SCCP-
          user messages by setting up a temporary or permanent
          signalling connection.

     *    Protocol class 3 allows the features of protocol class 2 with
          the inclusion of flow control.  Detection of message loss or
          mis-sequencing is included.

   Protocol classes 0 and 1 make up the SCCP connectionless service.
   Protocol classes 2 and 3 make up the SCCP connection-oriented
   service.

1.4.3 Native Management Functions

   The SUA layer provides the capability to indicate errors associated
   with the SUA-protocol messages and to provide notification to local
   management and the remote peer as is necessary.

1.4.4 Interworking with SCCP Network Management Functions

   SUA uses the existing ASP management messages for ASP status
   handling.  The interworking with SCCP management messages consists
   of DUNA, DAVA, DAUD, DRST, DUPU or SCON messages (defined in section
   3) on receipt of SSP, SSA, SST or SSC (defined by SCCP) to the
   appropriate ASPs.  See also chapter 1.4.5. The primitives below are
   sent between the SCCP and SUA management functions in the SG to
   trigger events in the IP and SS7 domain.












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   Generic   |Specific   |
   Name      |Name       |ANSI/ITU Reference
   ----------+-----------+---------------------------------------------
   N-State   |Request    |ITU-Q.711   Chap 6.3.2.3.2 (Tab 16/Q.711)
             |Indication |ANSI-T1.112 Chap 2.3.2.3.2 (Tab 8E/T1.112.1)
   ----------+-----------+---------------------------------------------
   N-Pcstate |Indication |ITU-Q.711   Chap 6.3.2.3.3 (Tab 1/Q.711)
             |           |ANSI-T1.112 Chap 2.3.2.3.4 (Tab 8G/T1.112.1)
   ----------+-----------+---------------------------------------------
   N-Coord   |Request    |ITU-Q.711   Chap 6.3.2.3.1 (Tab 15/Q.711)
             |Indication |ANSI-T1.112 Chap 2.3.2.3.3 (Tab 8F/T1.112.1)
             |Response   |
             |Confirm    |

1.4.5 Support for the management between the SGP and ASP.

   The SUA layer provides interworking with SCCP management functions
   at the SG for interoperation between the switched circuit networks
   and the IP network.  It should:

     *    Provide an indication to the SCCP-user at an ASP that a SS7
          endpoint/peer is unreachable.
     *    Provide an indication to the SCCP-user at an ASP that a SS7
          endpoint/peer is reachable.
     *    Provide congestion indication to SCCP-user at an ASP.
     *    Provide the initiation of an audit of SS7 endpoints at the
          SG.

1.4.6 Relay function

   For network scalability purposes, the SUA may be enhanced with a
   relay functionality to determine the next hop SCTP association
   towards the destination SUA endpoint.

   The determination of the next hop may be based on Global Title
   information (e.g. E.164 number), in analogy with SCCP GTT in SS7
   networks, modeled in [ITU-T Q.714]. It may also be based on Hostname
   information, IP address or pointcode contained in the called party
   address.

   This allows for greater scalability, reliability and flexibility in
   wide-scale deployments of SUA.  The usage of a relay function is a
   deployment decision.

1.5 Internal Functions Provided in the SUA Layer

   To perform its addressing and relaying capabilities, the SUA makes
   use of an Address Mapping Function (AMF). This function is
   considered part of SUA, but the way it is realized is left
   implementation / deployment dependent (local tables, DNS [2916],
   LDAP, etc.)


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   The AMF is invoked when a message is received at the incoming
   interface. The AMF is responsible for resolving the address
   presented in the incoming SCCP/SUA message to SCTP associations to
   destinations within the IP network. The AMF will select the
   appropriate SCTP association based upon routing context / routing
   key information available. The destination might be the end SUA node
   or a SUA relay node. The Routing Keys reference an Application
   Server, which will have one or more ASPs processing traffic for the
   AS.  The availability and status of the ASPs is handled by SUA ASP
   management messages.

   Possible SS7 address/routing information that comprise a Routing Key
   entry includes, for example, OPC, DPC, SIO found in the MTP3 routing
   label, SCCP subsystem number, or Transaction ID. IP addresses and
   hostnames can also be used as Routing Key Information.

   It is expected that the routing keys be provisioned via a MIB,
   dynamic registration or external process, such as a database.

1.5.1 Address Mapping at the SG

   Normally, one or more ASPs are active in the AS (i.e., currently
   processing traffic) but in certain failure and transition cases it
   is possible that there may not be an active ASP available. The SGP
   will buffer the message destined for this AS for a time T(r) or
   until an ASP becomes available. When no ASP becomes available before
   expiry of T(r), the SGP will flush the buffered messages and
   initiate the appropriate return or refusal procedures.

   If there is no address mapping match for an incoming message, a
   default treatment MAY be specified.  Possible solutions are to
   provide a default Application Server to direct all unallocated
   traffic to a (set of) default ASP(s), or to drop the messages and
   provide a notification to management. The treatment of unallocated
   traffic is implementation dependent.

1.5.2 Address Mapping at the ASP

   To direct messages to the SS7 network, the ASP MAY perform an
   address mapping to choose the proper SGP for a given message.  This
   is accomplished by observing the Destination Point Code and other
   elements of the outgoing message, SS7 network status, SGP
   availability, and Routing Context configuration tables.

   A Signalling Gateway may be composed of one or more SGPs. There is,
   however, no SUA messaging to manage the status of an SGP. Whenever
   an SCTP association to an SGP exists, it is assumed to be available.
   Also, every SGP of one SG communicating with one ASP regarding one
   AS provides identical SS7 connectivity to this ASP.

   An ASP routes responses to the SGP that it received messages from;


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   within the routing context which it is currently active and
   receiving traffic.

1.5.3 Address Mapping Function at a Relay Node

   The relay function is invoked when:

     -    Routing is on Global Title
     -    Routing is on Hostname
     -    Routing is on SSN and PC or SSN and IP Address and the
          address presented is not the one of the relay node

   Translation/resolution of the above address information yields one
   of the following:

     -    Route on SSN: SCTP association ID towards the destination
          node, SSN and optionally Routing Context and/or IP address.
     -    Route on GT: SCTP association ID towards next relay node,
          (new) GT and optionally SSN and/or Routing Context.
     -    Routing on Hostname: SCTP association ID towards next relay
          node, (new) Hostname and optionally SSN and/or Routing
          Context.
     -    A local SUA-user (combined relay/end node)

   To prevent looping, an SS7 hop counter is used. The originating end
   node (be it an SS7 or an IP node) sets the value of the SS7 hop
   counter to the maximum value (15 or less). Each time the relay
   function is invoked within an intermediate (relay) node, the SS7 hop
   counter is decremented. When the value reaches zero, the return or
   refusal procedures are invoked with reason "Hop counter violation".

1.5.4 SCTP Stream Mapping

   The SUA supports SCTP streams. Signalling Gateway SG and Application
   Servers need to maintain a list of SCTP and SUA-users for mapping
   purposes.  SCCP-users requiring sequenced message transfer need to
   be sent over a stream with sequenced delivery.

   SUA uses stream 0 for SUA management messages.  It is OPTIONAL that
   sequenced delivery be used to preserve the order of management
   message delivery.

   Stream selection based on protocol class:

     -    Protocol class 0: SUA MAY select unordered delivery.  The
          stream selected is based on traffic information available
          to the SGP or ASP.
     -    Protocol class 1: SUA MUST select ordered delivery.  The
          stream selected is based upon the sequence parameter given by
          the upper layer over the primitive interface and other
          traffic information available to the SGP or ASP


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    -     Protocol classes 2 and 3: SUA MUST select ordered delivery.
          The stream selected is based upon the source local reference
          of the connection and other traffic information available to
          the SGP or ASP.

1.5.5 Flow Control

   Local Management at an ASP may wish to stop traffic across an SCTP
   association to temporarily remove the association from service or to
   perform testing and maintenance activity.  The function could
   optionally be used to control the start of traffic on to a newly
   available SCTP association.

1.5.6 Congestion Management

   The SUA layer is informed of local and IP network congestion by
   means of an implementation-dependent function (e.g., an
   implementation-dependent indication from the SCTP of IP network
   congestion).

   At an ASP or IPSP, the SUA layer indicates congestion to local SCCP-
   Users by means of an appropriate SCCP primitive (e.g. N-INFORM, N-
   NOTICE), as per current SCCP procedures, to invoke appropriate upper
   layer responses.  When an SG determines that the transport of SS7
   messages is encountering congestion, the SG MAY trigger SS7 SCCP
   Congestion messages to originating SS7 nodes, per the congestion
   procedures of the relevant SCCP standard. The triggering of SS7 SCCP
   Management messages from an SG is an implementation-dependent
   function.

   The SUA layer at an ASP or IPSP MAY indicate local congestion to an
   SUA peer with an SCON message.  When an SG receives a congestion
   message (SCON) from an ASP, and the SG determines that an endpoint
   is now encountering congestion, it MAY trigger congestion procedures
   of the relevant SCCP standard.

1.6 Definition of SUA Boundaries

1.6.1 Definition of the upper boundary

   The following primitives are supported between the SUA and an SCCP-
   user (a reference to ITU and ANSI sections where these primitives
   and corresponding parameters are described, is also given):










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   Generic     |Specific  |
   Name        |Name      |ANSI/ITU Reference
   ------------+----------+-------------------------------------------
   N-CONNECT   |Request   |ITU-Q.711   Chap 6.1.1.2.2 (Tab 2/Q.711)
               |Indication|ANSI-T1.112 Chap 2.1.1.2.2 (Tab 2/T1.112.1)
               |Response  |
               |Confirm   |
   ------------+----------+-------------------------------------------
   N-DATA      |Request   |ITU-Q.711   Chap 6.1.1.2.3 (Tab 3/Q.711)
               |Indication|ANSI-T1.112 Chap 2.1.1.2.3 (Tab 3/T1.112.1)
   ------------+----------+-------------------------------------------
   N-EXPEDITED |Request   |ITU-Q.711   Chap 6.1.1.2.3 (Tab 4/Q.711)
   DATA        |Indication|ANSI-T1.112 Chap 2.1.1.2.3 (Tab 4/T1.112.1)
   ------------+----------+-------------------------------------------
   N-RESET     |Request   |ITU-Q.711   Chap 6.1.1.2.3 (Tab 5/Q.711)
               |Indication|ANSI-T1.112 Chap 2.1.1.2.3 (Tab 5/T1.112.1)
               |Response  |
               |Confirm   |
   ------------+----------+-------------------------------------------
   N-DISCONNECT|Request   |ITU-Q.711   Chap 6.1.1.2.4 (Tab 6/Q.711)
               |Indication|ANSI-T1.112 Chap 2.1.1.2.4 (Tab 6/T1.112.1)
   ------------+----------+-------------------------------------------
   N-INFORM    |Request   |ITU-Q.711   Chap 6.1.1.3.2 (Tab 8/Q.711)
               |Indication|ANSI-T1.112 Chap 2.1.1.2.5 (Tab 6A/T1.112.1)
   ------------+----------+-------------------------------------------
   N-UNITDATA  |Request   |ITU-Q.711   Chap 6.2.2.3.1 (Tab 12/Q.711)
               |Indication|ANSI-T1.112 Chap 2.2.2.3.1 (Tab 8A/T1.112.1)
   ------------+----------+-------------------------------------------
   N-NOTICE    |Indication|ITU-Q.711   Chap 6.2.2.3.2 (Tab 13/Q.711)
               |          |ANSI-T1.112 Chap 2.2.2.3.2 (Tab 8B/T1.112.1)
   ------------+----------+--------------------------------------------
   N-STATE     |Request   |ITU-Q.711   Chap 6.3.2.3.2 (Tab 16/Q.711)
               |Indication|ANSI-T1.112 Chap 2.3.2.3.2 (Tab 8E/T1.112.1)
   ------------+----------+--------------------------------------------
   N-PCSTATE   |Indication|ITU-Q.711   Chap 6.3.2.3.3 (Tab 17/Q.711)
               |          |ANSI-T1.112 Chap 2.3.2.3.4 (Tab 8G/T1.112.1)
   ------------+----------+--------------------------------------------
   N-COORD     |Request   |ITU-Q.711   Chap 6.3.2.3.1 (Tab 15/Q.711)
               |Indication|ANSI-T1.112 Chap 2.3.2.3.3 (Tab 8F/T1.112.1)
               |Response  |
               |Confirm   |

1.6.2 Definition of the lower boundary

   The upper layer primitives provided by the SCTP are provided in
   [SCTP].

1.6.3 Definition of the Boundary between SUA and Layer Management

   M-SCTP_ESTABLISH request
   Direction: LM -> SUA


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   Purpose:  LM requests ASP to establish an SCTP association with its
             peer.

   M-STCP_ESTABLISH confirm
   Direction: SUA -> LM
   Purpose:  ASP confirms to LM that it has established an SCTP
             association with its peer.

   M-SCTP_ESTABLISH indication
   Direction: SUA -> LM
   Purpose:  SUA informs LM that a remote ASP has established an SCTP
             association.

   M-SCTP_RELEASE request
   Direction: LM -> SUA
   Purpose:  LM requests ASP to release an SCTP association with its
             peer.

   M-SCTP_RELEASE confirm
   Direction: SUA -> LM
   Purpose:  ASP confirms to LM that it has released SCTP association
             with its peer.

   M-SCTP_RELEASE indication
   Direction: SUA -> LM
   Purpose:  SUA informs LM that a remote ASP has released an SCTP
             Association or the SCTP association has failed.

   M-SCTP RESTART indication
   Direction: SUA -> LM
   Purpose:  SUA informs LM that an SCTP restart indication has been
             received.

   M-SCTP_STATUS request
   Direction: LM -> SUA
   Purpose:  LM requests SUA to report the status of an SCTP
             association.

   M-SCTP_STATUS confirm
   Direction: SUA -> LM
   Purpose:  SUA responds with the status of an SCTP association.

   M-SCTP STATUS indication
   Direction: SUA -> LM
   Purpose:  SUA reports the status of an SCTP association.

   M-ASP_STATUS request
   Direction: LM -> SUA
   Purpose:  LM requests SUA to report the status of a local or remote
               ASP.

   M-ASP_STATUS confirm

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   Direction: SUA -> LM
   Purpose:  SUA reports status of local or remote ASP.

   M-AS_STATUS request
   Direction: LM -> SUA
   Purpose:  LM requests SUA to report the status of an AS.

   M-AS_STATUS confirm
   Direction: SUA -> LM
   Purpose:  SUA reports the status of an AS.

   M-NOTIFY indication
   Direction: SUA -> LM
   Purpose:  SUA reports that it has received a Notify message from its
             peer.

   M-ERROR indication
   Direction: SUA -> LM
   Purpose:  SUA reports that it has received an Error message from its
             peer or that a local operation has been unsuccessful.

   M-ASP_UP request
   Direction: LM -> SUA
   Purpose:  LM requests ASP to start its operation and send an ASP Up
             message to its peer.

   M-ASP_UP confirm
   Direction: SUA -> LM
   Purpose:  ASP reports that is has received an ASP UP Ack message
             from its peer.

   M-ASP_UP indication
   Direction: SUA -> LM
   Purpose:  SUA reports it has successfully processed an incoming ASP
             Up message from its peer.

   M-ASP_DOWN request
   Direction: LM -> SUA
   Purpose:  LM requests ASP to stop its operation and send an ASP Down
             message to its peer.

   M-ASP_DOWN confirm
   Direction: SUA -> LM
   Purpose:  ASP reports that is has received an ASP Down Ack message
             from its peer.

   M-ASP_DOWN indication
   Direction: SUA -> LM
   Purpose:  SUA reports it has successfully processed an incoming ASP
             Down message from its peer, or the SCTP association has
             been lost/reset.


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   M-ASP_ACTIVE request
   Direction: LM -> SUA
   Purpose:  LM requests ASP to send an ASP Active message to its peer.

   M-ASP_ACTIVE confirm
   Direction: SUA -> LM
   Purpose:  ASP reports that is has received an ASP Active Ack message
             from its peer.

   M-ASP_ACTIVE indication
   Direction: SUA -> LM
   Purpose:  SUA reports it has successfully processed an incoming ASP
             Active message from its peer.

   M-ASP_INACTIVE request
   Direction: LM -> SUA
   Purpose:  LM requests ASP to send an ASP Inactive message to its
             peer.

   M-ASP_INACTIVE confirm
   Direction: LM -> SUA
   Purpose:  ASP reports that is has received an ASP Inactive
             Ack message from its peer.

   M-ASP_INACTIVE indication
   Direction: SUA -> LM
   Purpose:  SUA reports it has successfully processed an incoming ASP
             Inactive message from its peer.

   M-AS_ACTIVE indication
   Direction: SUA -> LM
   Purpose:  SUA reports that an AS has moved to the AS-ACTIVE state.

   M-AS_INACTIVE indication
   Direction: SUA -> LM
   Purpose: SUA reports that an AS has moved to the AS-INACTIVE state.

   M-AS_DOWN indication
   Direction: SUA -> LM
   Purpose: SUA reports that an AS has moved to the AS-DOWN state.

   If the SUA layer supports dynamic registration of Routing Key, the
  layer MAY support the following additional primitives:

   M-RK_REG request
   Direction: LM -> SUA
   Purpose:  LM requests ASP to register RK(s) with its peer by sending
             REG REQ message

   M-RK_REG confirm
   Direction: SUA -> LM


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   Purpose:  ASP reports that it has received REG RSP message with
             registration status as successful from its peer.

   M-RK_REG indication
   Direction: SUA -> LM
   Purpose:  SUA informs LM that it has successfully processed an
             incoming REG REQ message.

   M-RK_DEREG request
   Direction: LM -> SUA
   Purpose:  LM requests ASP to deregister RK(s) with its peer by
             sending DEREG REQ message.

   M-RK_DEREG confirm
   Direction: SUA -> LM
   Purpose:  ASP reports that it has received DEREG RESP message with
             deregistration status as successful from its peer.

   M-RK_DEREG indication
   Direction: SUA -> LM
   Purpose:  SUA informs LM that it has successfully processed an
             incoming DEREG REQ from its peer.

2 Conventions

   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
   SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when
   they appear in this document, are to be interpreted as described in
   [RFC2119].

3 Protocol Elements

   The general message format includes a Common Message Header together
   with a list of zero or more parameters as defined by the Message
   Type.

   For forward compatibility, all Message Types may have attached
   parameters even if none are specified in this version.

   The Reserved field is set to 0 in messages sent and is not to be
   examined in messages received.

3.1 Common Message Header

   The protocol messages for the SCCP-User Adaptation Protocol requires
   a message structure which contains a version, message class, message
   type, message length and message contents. This message header is
   common among all signalling protocol adaptation layers:





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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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Version    |   Reserved    | Message Class | Message Type  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        Message Length                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Message Data                          |

   Note that the 'data' portion of SUA messages SHALL contain SCCP-User
   data, not the encapsulated SCCP message.

   Optional parameters can only occur at most once in an SUA message.

3.1.1 SUA Protocol Version

   The version field (ver) contains the version of the SUA adaptation
   layer.  The supported versions are:

     1   SUA version 1.0

3.1.2 Message Classes

   Message Classes

     0         SUA Management (MGMT) Message
     1         Reserved
     2         Signalling Network Management (SNM) Messages
     3         ASP State Maintenance (ASPSM) Messages
     4         ASP Traffic Maintenance (ASPTM) Messages
     5         Reserved
     6         Reserved
     7         Connectionless Messages
     8         Connection-Oriented Messages
     9         Routing Key Management (RKM) Messages.
     10 - 127  Reserved by the IETF
     128 - 255 Reserved for IETF-Defined Message Class Extensions

3.1.3 Message Types

   SUA Management Messages

     0         Error (ERR)
     1         Notify (NTFY)
     2 - 127   Reserved by the IETF
     128- 255  Reserved for IETF-Defined Message Class Extensions

   Signalling Network Management (SNM) Messages

     0         Reserved
     1         Destination Unavailable (DUNA)
     2         Destination Available (DAVA)

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     3         Destination State Audit (DAUD)
     4         Network Congestion (SCON)
     5         Destination User Part Unavailable (DUPU)
     6         Destination Restricted (DRST)
     7 - 127   Reserved by the IETF
     128 - 255 Reserved for IETF-Defined Message Class Extensions

   Application Server Process State Maintenance (ASPSM) Messages

     0         Reserved
     1         ASP Up (UP)
     2         ASP Down (DOWN)
     3         Heartbeat (BEAT)
     4         ASP Up Ack (UP ACK)
     5         ASP Down Ack (DOWN ACK)
     6         Heartbeat Ack (BEAT ACK)
     7 - 127   Reserved by the IETF
     128 - 255 Reserved for IETF-Defined Message Class Extensions

   ASP Traffic Maintenance (ASPTM) Messages

     0         Reserved
     1         ASP Active (ACTIVE)
     2         ASP Inactive (INACTIVE)
     3         ASP Active Ack (ACTIVE ACK)
     4         ASP Inactive Ack (INACTIVE ACK)
     5 - 127   Reserved by the IETF
     128 - 255 Reserved for IETF-Defined Message Class Extensions

   Routing Key Management (RKM) Messages

     0         Reserved
     1         Registration Request (REG REQ)
     2         Registration Response (REG RSP)
     3         Deregistration Request (DEREG REQ)
     4         Deregistration Response (DEREG RSP)
     5 - 127   Reserved by the IETF
     128 - 255 Reserved for IETF-Defined Message Class Extensions

   Connectionless (CL) Messages

     0         Reserved
     1         Connectionless Data Transfer (CLDT)
     2         Connectionless Data Response (CLDR)
     3 - 127   Reserved by the IETF
     128 - 255 Reserved for IETF-Defined Message Class Extensions

   Connection-Oriented (CO) Messages

     0         Reserved
     1         Connection Request (CORE)
     2         Connection Acknowledge (COAK)

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     3         Connection Refused (COREF)
     4         Release Request (RELRE)
     5         Release Complete (RELCO)
     6         Reset Confirm (RESCO)
     7         Reset Request (RESRE)
     8         Connection Oriented Data Transfer (CODT)
     9         Connection Oriented Data Acknowledge (CODA)
     10        Connection Oriented Error (COERR)
     11        Inactivity Test (COIT)
     12 - 127  Reserved by the IETF
     128 - 255 Reserved for IETF-Defined Message Class Extensions

3.1.4 Message Length

   The Message Length defines the length of the message in octets,
   including the header and including all padding bytes. Message Length
   is a 32-bit identifier.

3.1.5 Tag-Length-Value Format

   SUA messages consist of a Common Header followed by zero or more
   parameters, as defined by the message type.  The Tag-Length-Value
   (TLV) parameters contained in a message are defined in a Tag-Length-
   Value format as shown below.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Parameter Tag        |       Parameter Length        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     \                                                               \
     /                       Parameter Value                         /
     \                                                               \
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameter Tag: 16 bits (unsigned integer)

      Tag field is a 16-bit identifier of the type of parameter. It
      takes a value of 0 to 65535.

   Parameter Length: 16 bits (unsigned integer)

     The Parameter Length field contains the size of the parameter in
     bytes, including the Parameter Tag, Parameter Length, and
     Parameter Value fields. The Parameter Length does not include any
     padding bytes. However, composite parameters will contain all
     padding bytes, since all parameters contained within this
     composite parameter will be considered multiples of 4 bytes.

   Parameter Value: variable-length.



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     The Parameter Value field contains the actual information to be
     trasnfered in the parameter.

     The total length of a parameter (including Tag, Parameter Length
     and Value fields) MUST be a multiple of 4 bytes. If the length of
     the parameter is not a multiple of 4 bytes, the sender pads the
     parameter at the end (i.e., after the Parameter Value field) with
     all zero bytes. The length of the padding is NOT included in the
     parameter length field. A sender should NEVER pad with more than 3
     bytes. The receiver MUST ignore the padding bytes.

   Implementation note: the use of TLV in principle allows the
   parameters to be placed in a random order in the message. However,
   some guidelines should be considered for easy processing in the
   following order:

     -    Parameters needed to correctly process other message
          parameters, preferably should precede these parameters (such
          as Routing Context).
     -    Mandatory parameters preferably SHOULD precede any optional
          parameters.
     -    The data parameter will normally be the final one in the
          message.
     -    The receiver SHOULD accept parameters in any order, except
          where explicitly mandated.

3.2 SUA Connectionless Messages

   The following section describes the SUA Connectionless transfer
   messages and parameter contents.  The general message format
   includes a Common Message Header together with a list of zero or
   more parameters as defined by the Message Type.  All Message Types
   can have attached parameters.

3.2.1 Connectionless Data Transfer (CLDT)

   This message transfers data between one SUA to another.
















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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 = 0x0006         |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                       Routing Context                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0115          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Protocol Class                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0102          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Source Address                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0103          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                     Destination Address                       /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0116         |             Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Control                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0101          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         SS7 Hop Count                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0113          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Importance                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0114          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Message Priority                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0013          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Correlation ID                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0117          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Segmentation                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010b          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                             Data                              /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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   Parameters
     Routing Context               Mandatory
     Protocol Class                Mandatory
     Source Address                Mandatory
     Destination Address           Mandatory
     Sequence Control              Mandatory
     SS7 Hop Count                 Optional
     Importance                    Optional
     Message Priority              Optional
     Correlation ID                Optional
     Segmentation                  Optional
     Data                          Mandatory

   Implementation note: This message covers the following SCCP
   messages: unitdata (UDT), extended unitdata (XUDT), long unitdata
   (LUDT).

3.2.2 Connectionless Data Response (CLDR)

   This message is used as a response message by the peer to report
   errors in the received CLDT message, when the return on error option
   is set.































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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 = 0x0006         |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                       Routing Context                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0106          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           SCCP Cause                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0102          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Source Address                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0103          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                     Destination Address                       /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0101          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         SS7 Hop Count                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0113          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Importance                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0114          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Message Priority                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0013          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Correlation ID                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0117          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Segmentation                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010b          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
      /                             Data                              /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Mandatory
     SCCP Cause                    Mandatory
     Source Address                Mandatory

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     Destination Address           Mandatory
     SS7 Hop Count                 Optional
     Importance                    Optional
     Message Priority              Optional
     Correlation ID                Optional
     Segmentation                  Optional
     Data                          Optional

   Implementation note: This message covers the following SCCP
   messages: unitdata service (UDTS), extended unitdata service (XUDTS)
   and long unitdata service (LUDTS).

3.3 Connection Oriented Messages

3.3.1 Connection Oriented Data Transfer (CODT)

   This message transfers data between one SUA to another for
   connection-oriented service.

       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 = 0x0107          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0105          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Reference Number                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0114          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Message Priority                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0013          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Correlation ID                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010b          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                             Data                              /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Mandatory
     Sequence Number               Optional *1

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     Destination Reference Number  Mandatory
     Message Priority              Optional
     Correlation ID                Optional
     Data                          Mandatory

   NOTE *1:   This parameter is not present in case of Expedited Data
              (ED).

   Implementation note: In order for the CODT to represent DT1, DT2 and
   ED messages, the following conditions MUST be met:

   DT1 is represented by a CODT when:
     Sequence Number parameter is present (contains "more" indicator).

   DT2 is represented by a CODT when:
     Sequence Number parameter is present (contains P(S), P(R) and more
    indicator)

   ED is represented by a CODT with:
     Sequence Number parameter is not present

3.3.2 Connection Oriented Data Acknowledge (CODA)

   The peer uses this message to acknowledge receipt of data.  This
   message is used only with protocol class 3.

       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 = 0x0105          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Reference Number                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0108          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Receive Sequence Number                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010A          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            Credit                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Mandatory
     Destination Reference Number  Mandatory
     Receive Sequence Number       Optional *1
     Credit                        Mandatory *1

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   NOTE *1:    Mandatory when representing Data Acknowledgement (AK).

   Implementation note: In order for the CODA to represent DA and EA
   messages, the following conditions MUST be met:

   DA is represented by a CODA when:
     Receive Sequence Number parameter is present (contains P(S), P(R)
    and more indicator)

   EA is represented by a CODA when:
     Receive Sequence Number parameter is not present

3.3.3 Connection Request (CORE)

   This message is used for establishing a signalling connection
   between two peer endpoints.

        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 = 0x0115          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Protocol Class                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0104          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Source Reference Number                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0103          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                     Destination Address                       /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0116          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Control                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0107          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0102          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Source Address                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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      |         Tag = 0x0101          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         SS7 Hop Count                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0113          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Importance                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0114          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Message Priority                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010A          |           Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            Credit                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010b          |           Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                             Data                              /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Mandatory
     Protocol Class                Mandatory
     Source Reference Number       Mandatory
     Destination Address           Mandatory
     Sequence Control              Mandatory
     Sequence Number               Optional *1
     Source Address                Optional
     SS7 Hop Count                 Optional
     Importance                    Optional
     Message Priority              Optional
     Credit                        Optional *1
     Data                          Optional

   NOTE *1: Manditory for protocol class 3 only.

   Implementation note: This message covers the following SCCP message:
   Connection Request (CR).

3.3.4 Connection Acknowledge (COAK)

   This message is used to acknowledge a connection request from the
   peer endpoint.








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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 = 0x0006         |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                       Routing Context                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0115          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Protocol Class                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0105          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Reference Number                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0104          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Source Reference Number                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x01116          |            Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Control                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010A          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            Credit                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0102          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Source Address                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0113          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Importance                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0114          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Message Priority                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0103          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                     Destination Address                       /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010b          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                             Data                              /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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   Parameters
     Routing Context               Mandatory
     Protocol Class                Mandatory
     Destination Reference Number  Mandatory
     Source Reference Number       Mandatory
     Sequence Control              Mandatory
     Credit                        Mandatory *2
     Source Address                Optional
     Importance                    Optional
     Message Priority              Optional
     Destination Address           Optional *1
     Data                          Optional

   NOTE *1:    Destination Address parameter will be present in case
               that the received CORE message conveys the Source
               Address parameter.

   NOTE *2:    Only applicable for protocol class 3.

   Implementation note: This message covers the following SCCP message:
   Connection Confirm (CC).

3.3.5 Connection Refused (COREF)

   This message is used to refuse a connection request between two peer
   endpoints.



























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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 = 0x0006         |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                       Routing Context                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0105          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Reference Number                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0106          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           SCCP Cause                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0102          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Source Address                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0103          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                     Destination Address                       /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0113          |             Length = 8        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Importance                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010b          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                             Data                              /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context                    Mandatory
     Destination Reference Number       Mandatory
     SCCP Cause                         Mandatory
     Source Address                     Optional
     Destination Address                Optional *1
     Importance                         Optional
     Data                               Optional

   Note *1:   Destination Address parameter will be present in case
              that the received CORE message conveys the Source Address
              parameter.

   Implementation note: This message covers the following SCCP message:
   Connection REFused (CREF).


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3.3.6 Release Request (RELRE)

   This message is used to request a signalling connection between two
   peer endpoints be released.  All associated resources can then be
   released.

       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 = 0x0105          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Reference Number                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0104          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Source Reference Number                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0106          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          SCCP Cause                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0113          |             Length = 8        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Importance                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010b          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                             Data                              /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Mandatory
     Destination Reference Number  Mandatory
     Source Reference Number       Mandatory
     SCCP Cause                    Mandatory
     Importance                    Optional
     Data                          Optional

   Implementation note: This message covers the following SCCP message:
   connection ReLeaSeD (RLSD).

3.3.7 Release Complete (RELCO)

   This message is used to acknowledge the release of a signalling
   connection between two peer endpoints.  All associated resources
   should be released.

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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 = 0x0006         |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                       Routing Context                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0105          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Reference Number                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0104          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Source Reference Number                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0113          |             Length = 8        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Importance                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Mandatory
     Destination Reference Number  Mandatory
     Source Reference Number       Mandatory
     Importance                    Optional

   Implementation note: This message covers the following SCCP message:
   ReLease Complete (RLC).

3.3.8 Reset Request (RESRE)

   This message is used to indicate that the sending SCCP/SUA wants to
   initiate a reset procedure (re-initialization of sequence numbers)
   to the peer endpoint.

















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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 = 0x0006         |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                       Routing Context                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0105          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Reference Number                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0104          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Source Reference Number                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0106          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           SCCP Cause                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Mandatory
     Destination Reference Number  Mandatory
     Source Reference Number       Mandatory
     SCCP Cause                    Mandatory

   Implementation note: This message covers the following SCCP message:
   ReSet Request (RSR).

3.3.9 Reset Confirm (RESCO)

   This message is used to confirm the Reset Request.

       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 = 0x0105          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Reference Number                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0104          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Source Reference Number                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters

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     Routing Context               Mandatory
     Destination Reference Number  Mandatory
     Source Reference Number       Mandatory

   Implementation note: This message covers the following SCCP message:
   ReSet Confirmation (RSC).

3.3.10 Connection Oriented Error (COERR)

   The COERR message is sent to indicate a protocol data unit error.

       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 = 0x0105          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Reference Number                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0106          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          SCCP Cause                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Mandatory
     Destination Reference Number  Mandatory
     SCCP Cause                    Mandatory

   Implementation note: This message covers the following SCCP message:
   Protocol Data Unit ERRor (ERR).

3.3.11 Connection Oriented Inactivity Test (COIT)

   This message is used for auditing the signalling connection state
   and the consistency of connection data at both ends of the
   signalling connection.












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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 = 0x0006          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                       Routing Context                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0115          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Protocol Class                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0104          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Source Reference Number                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0105          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Destination Reference number                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0107          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010A          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            Credit                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Mandatory
     Protocol Class                Mandatory
     Source Reference Number       Mandatory
     Destination Reference number  Mandatory
     Sequence Number               Mandatory *1
     Credit                        Mandatory *1

   NOTE *1:   Information in these parameter fields reflects those
              values sent in the last data form 2 or data
              acknowledgement message. They are ignored if the protocol
              class indicates class 2.

   Implementation note: This message covers the following SCCP message:
   Inactivity Test (IT).

3.4 Signalling Network Management (SNM) Messages

3.4.1 Destination Unavailable (DUNA)

   In the scope of SUA, this message is covered by the PC- or N-state
   indication passed between SCCP and local SCCP-user. The DUNA message
   is sent from the SG or relay node to all concerned ASPs (servicing

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   SCCP-users considered local to the SG or relay node, see chapter
   1.3.1.1), when a destination or SCCP-user has become unreachable.
   The SUA-User at the ASP is expected to stop traffic to the affected
   destination or SCCP-user through the SG or relay node initiating the
   DUNA.

   The format for DUNA Message parameters 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                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0012          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Affected Point Code                    /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x8003          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              SSN                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0112          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              SMI                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0004          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                          Info String                          /

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

   Parameters
     Routing Context               Optional
     Affected Point Code           Mandatory *1
     SSN                           Optional *1
     SMI                           Optional
     Info String                   Optional

          Note 1:  When the SSN is included, the DUNA message
                   corresponds to the SCCP N-STATE primitive. When SSN
                   is not, the DUNA message corresponds to the SCCP N-
                   PCSTATE primitive.   When SSN is not, the DUNA
                   message corresponds to the SCCP N-PCSTATE primitive.

3.4.2 Destination Available (DAVA)

   In the scope of SUA, this message is covered by the PC- and N-state
   indication passed between SCCP and local SCCP-user. The DAVA message

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   is sent from the SG or relay node to all concerned ASPs (servicing
   SCCP-users considered local to the SG or relay node, see chapter
   1.3.1.1) to indicate that a destination (PC or SCCP-user) is now
   reachable. The ASP SUA-User protocol is expected to resume traffic
   to the affected destination through the SG or relay node initiating
   the DAVA.

       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 = 0x0012          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Affected Point Code                    /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x8003          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              SSN                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0112          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              SMI                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0004          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                          Info String                          /

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

   Parameters
     Routing Context               Optional
     Affected Point Code           Mandatory *1
     SSN                           Optional *1
     SMI                           Optional
     Info String                   Optional

   Note 1:    When the SSN is included, the DAVA message corresponds to
              the SCCP N-STATE primitive. When SSN is not included, the
              DAVA message corresponds to the SCCP N-PCSTATE primitive.
              The Affected Point Code can only contain one point code
              when SSN is present.

3.4.3 Destination State Audit (DAUD)

   The DAUD message can be sent from the ASP to the SG (or relay node)
   to query the availability state of the routes to an affected
   destination. A DAUD may be sent periodically after the ASP has

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   received a DUNA, until a DAVA is received. The DAUD can also be sent
   when an ASP recovers from isolation from the SG (or relay node).

       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 = 0x0012          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Affected Point Code                    /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x8003          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              SSN                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010c          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           User/Cause                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0004          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                          Info String                          /

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

   Parameters
     Routing Context               Optional
     Affected Point Code           Mandatory *1
     SSN                           Optional *1
     User / Cause                  Optional
     Info String                   Optional

   Note 1:    If the SSN is present, the DAUD is "soliciting" N-STATE
              primitives, otherwise it is "soliciting" N-PCSTATE
              primitives.

3.4.4 Network Congestion (SCON)

   The SCON message can be sent from the SG or relay node to all
   concerned ASPs to indicate that the congestion level in the SS7
   network to a specified destination has changed.







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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 = 0x0006          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                       Routing Context                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0012          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Affected Point Code                    /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x8003          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              SSN                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0118          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Congestion Level                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0112          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              SMI                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0004          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                          Info String                          /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Optional
     Affected Point Code           Mandatory *1
     SSN                           Optional *1
     Congestion Level              Mandatory
     SMI                           Optional
     Info String                   Optional

   Note 1:    When the SSN is included, the SCON message corresponds to
              the SCCP N-STATE primitive.  When the SSN is not
              included, the SCON message corresponds to the SCCP N-
              PCSTATE primitive reporting signalling point or network
              congestion status.

3.4.5 Destination User Part Unavailable (DUPU)

   The DUPU message is used by an SG to inform an ASP that a remote
  peer at an SS7 node is unavailable.

   The format for DUPU message parameters is as follows:


Loughney (editor)                                           [Page 41]

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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 = 0x0006          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                       Routing Context                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0012          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Affected Point Code                    /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x010c          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           User/Cause                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0004          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      \                                                               \
      /                          INFO String                          /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Optional
     Affected Point Code           Mandatory *1
     User/Cause                    Mandatory
     Info String                   Optional

   Note 1:    The DUPU corresponds to the SCCP N-PCSTATE primitive.

3.4.6 Destination Restricted (DRST)

   The DRST message is optionally sent from the SG to all concerned
   ASPs to indicate that the SG has determined that one or more
   destinations are now restricted from the point of view of the SG, or
   in response to a DAUD message if appropriate. The SUA layer at the
   ASP is expected to send traffic to the affected destination via an
   alternate SG of equal priority, but only if such an alternate route
   exists and is available. If the ASP currently considers the affected
   destination unavailable, the peer should be informed that traffic to
   the affected destination could be resumed.  In this case, the SUA
   layer should route the traffic through the SG initiating the DRST
   message.

   This message is optional for the SG to send and it is optional for
   the ASP to act on any information received in the 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Loughney (editor)                                           [Page 42]

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      |         Tag = 0x0006          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                       Routing Context                         /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0012          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                        Affected Point Code                    /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x8003          |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              SSN                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0112          |            Length = 8         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Reserved                  |       SMI      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Tag = 0x0004          |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      /                          Info String                          /
      \                                                               \
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Parameters
     Routing Context               Optional
     Affected Point Code           Mandatory *1
     SSN                           Optional *1
     SMI                           Optional *1
     Info String                   Optional

  Note 1:    The Affected Point Code referes to the node to which
              become restricted or which has requested coordinated
              service outgage.  When SSN is included in the message
              parameter, the DRST message corresponds to the SCCP N-
              COORD primitive.  If the SMI parameter is also included
              in the message, the DRST message corresponds to the N-
              COORD Request and N-COORD Indication primitives,
              otherwise, the DRST message corresponse to the N-COORD
              Response and N-COORD Confirm primitives. The Affected
              Point Code can only contain one point code when SSN is
              present. When SSN is not present, DRST corresponds to N-
              PCSTATE primitive.

3.5 Application Server Process State Maintenance Messages

3.5.1 ASP Up (UP)

   The ASP UP (UP) message is used to indicate to a remote SUA peer
   that the Adaptation layer is up and running.

       0                     1                   2                   3

Loughney (editor)                                           [Page 43]