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draft-ietf-sigtran-sua-14

Description: Request For Comments

You can download source copies of the file as follows:

draft-ietf-sigtran-sua-14.txt in text format.

Listed below is the contents of file draft-ietf-sigtran-sua-14.txt.


INTERNET-DRAFT                                    J. Loughney (Editor) 
Internet Engineering Task Force                                  Nokia 
                                                         G. Sidebottom 
                                                   gregside Consulting 
Issued:  30 June 2002                             L. Coene, G. Verwimp 
Expires: 30 December 2002                                      Siemens 
                                                             J. Keller 
                                                               Tekelec 
                                                           B. Bidulock 
                                                   OpenSS7 Corporation 
 
     Signalling Connection Control Part User Adaptation Layer (SUA) 
                    <draft-ietf-sigtran-sua-14.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 December 30th, 2002. 
    
Abstract 
    
   This Internet Draft defines a protocol for the transport of any      
   Signalling Connection Control Part-User signalling (e.g., 
   Transaction Capabilities Protocol, Radio Acccess Network Application 
   Protocol, etc.) over IP using the Stream Control Transport Protocol. 
   The protocol should 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.  Protocol elements are added to allow 
   operation between peers in the Signaling System No.7 and IP domains.  

 
Internet Draft                   SUA                     June 30, 2002 
 
Abstract..............................................................1 
1. Introduction.......................................................3 
1.1 Scope.............................................................3 
1.2 Terminology.......................................................3 
1.3 Signalling Transport Architecture.................................5 
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........................................................17 
3 Protocol Elements..................................................17 
3.1 Common Message Header............................................17 
3.2 SUA Connectionless Messages......................................21 
3.3 Connection Oriented Messages.....................................24 
3.4 Signalling Network Management (SNM) Messages.....................35 
3.5 Application Server Process State Maintenance Messages............41 
3.6 ASP Traffic Maintenance Messages.................................44 
3.7 SUA Management Messages..........................................47 
3.8 Routing Key Management (RKM) Messages............................49 
3.9 Common Parameters................................................52 
3.10 SUA-Specific parameters.........................................65 
4. Procedures........................................................81 
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.....................................84 
4.4 Routing Key Management Procedures................................97 
4.5 Availability and/or Congestion Status of SS7 Destination Support100 
4.6 MTP3 Restart....................................................102 
4.7 SCCP - SUA Interworking at the SG...............................103 
5 Examples of SUA Procedures........................................104 
5.1 SG Architecture.................................................104 
5.2 IPSP Examples...................................................106 
6 Security Considerations...........................................107 
6.1 Introduction....................................................107 
6.2 Threats.........................................................108 
6.3 Protecting Confidentiality......................................109 
6.4 IPsec Usage.....................................................109 
6.5  TLS Usage......................................................110 
6.6 Peer-to-Peer Considerations.....................................110 
7 IANA Considerations...............................................111 
7.1 SCTP Payload Protocol ID........................................111 
7.2 Port Number.....................................................112 
7.3 Protocol Extensions.............................................112 
8 Timer Values......................................................113 
9 Acknowledgements..................................................113 
10 Authors' Addresses...............................................114 
11 References.......................................................114 
11.1 Normative......................................................115 
11.2................................................................115 
Appendix A Signaling Network Architecture...........................116 
A.1 Generalized Peer-to-Peer Network Architecture...................116 
A.2 Signalling Gateway Network Architecture.........................117 
A.3 Signaling Gateway Message Distribution Recommendations..........118 
 
Loughney (editor)                                           [Page 2] 
 

 
Internet Draft                   SUA                     June 30, 2002 
 
1. Introduction 
    
   This draft defines a protocol for the transport SS7 SCCP [ANSI SCCP] 
   [ANSI SCCP] Users (i.e. TCAP, RANAP, etc.) signalling messages over 
   IP using the Stream Control Transmission Protocol (SCTP) [2960].  
   This protocol would be used between a Signalling Gateway (SG) and 
   Signaling Endpoint located in an IP network.  Additionally, the 
   protocol can be used to transport SS7 SCCP users between two 
   signaling endpoints located within an IP network. 
    
1.1 Scope 
    
   There is on-going integration of SCN networks and IP networks.  
   Network service providers are designing all IP architectures that 
   include 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 document details the delivery of SCCP-user messages (MAP & CAP 
   over TCAP [ANSI TCAP] [ITU TCAP], RANAP [RANAP], etc.) and new 3rd 
   Generation network protocol messages over IP between two signalling 
   endpoints.  Consideration is given for the transport from an SS7 
   Signalling Gateway (SG) 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 (TCAP, RANAP, 
          etc.) 
     *    Support for SCCP connectionless service. 
     *    Support for SCCP connection oriented service. 
     *    Support for the seamless operation of SCCP-User protocol 
          peers. 
     *    Support for the management of SCTP transport associations 
          between a SG and one or more IP-based signalling nodes). 
     *    Support for distributed IP-based signalling nodes. 
     *    Support for the asynchronous reporting of status changes to 
          management. 
    
1.2 Terminology 
    
   Signalling Gateway (SG) - Network element that terminates SCN 
   signalling 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 
 
Loughney (editor)                                           [Page 3] 
 

 
Internet Draft                   SUA                     June 30, 2002 
 
   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 a 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 
   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 
 
Loughney (editor)                                           [Page 4] 
 

 
Internet Draft                   SUA                     June 30, 2002 
 
   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. 
    
   Network Byte Order - Most significant byte first, a.k.a. Big Endian. 
    
   Layer Management - Layer Management is a nodal function that handles 
   the inputs and outputs between the SUA layer and a local management 
   entity.   
    
   Host - The computing platform that the SGP or ASP process is running 
   on. 
    
   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. 
    
   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 SCN 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 
   SCN 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-IP 
 
Loughney (editor)                                           [Page 5] 
 

 
Internet Draft                   SUA                     June 30, 2002 
 
   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 
    
   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 PC and 
   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 SG as relay-point 
    
   A Global Title translation is executed at the SG, 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", from an AS can be derived.  Selection of 
   the AS is thus based on the SCCP called party address  (and possibly 
   other SS7 parameters depending on the implementation).   
 
Loughney (editor)                                           [Page 6] 
 

 
Internet Draft                   SUA                     June 30, 2002 
 
    
1.3.2 Protocol Architecture for Connection-Oriented Transport  
    
   In this architecture, the SCCP and SUA layers interface in the SGP 
   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 
   SEP via SGP to ASP or the other way.  The routing of the Connect 
   Request message is done in the same way as described in 1.3.1. 
    
        ********   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 Application Protocol (e.g. - RANAP/RNSAP) 
          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, but is contained with an IP network.  
   This allows extra flexibility in developing networks, especially 
   when interaction between legacy signalling is not needed.  The 
   architecture removes the need for signalling gateway functionality. 

 
Loughney (editor)                                           [Page 7] 
 

 
Internet Draft                   SUA                     June 30, 2002 
 
    
          ********   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 SG and at the ASP support the seamless transport the user 
   messages between the SG and the ASP. 
    
1.4.2 SCCP Protocol Class Support 
    
   Depending upon the SCCP-users supported, the SUA shall support 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. 
    
 
Loughney (editor)                                           [Page 8] 
 

 
Internet Draft                   SUA                     June 30, 2002 
 
     *    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 on receipt of SSP, 
   SSA, SST or SSC to the appropriate ASPs.  See also chapter 1.4.5. 
   The primitives below are considered to be send between the SCCP and 
   SUA management functions in the SG to trigger events in the IP and 
   SS7 domain. 
    
   Generic   |Specific   |  
   Name      |Name       |ANSI/ITU Reference                         
   ----------+-----------+--------------------------------------------- 
   N-State   |Request    |ITU-Q.711   Chap 6.3.2.3.2 (Tab 14/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 15/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 13/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 should provide interworking with SCCP management 
   functions at the SG for seamless inter-operation between the SCN 
   network and the IP network.  It should: 
    

 
Loughney (editor)                                           [Page 9] 
 

 
Internet Draft                   SUA                     June 30, 2002 
 
     *    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.) 
    
   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.  
    

 
Loughney (editor)                                           [Page 10] 
 

 
Internet Draft                   SUA                     June 30, 2002 
 
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 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; 
   within the routing context which it is currently active and 
   receiving traffic.  The routing context itself is used by the ASP to 
   select the SGP. 
 
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.  
 
Loughney (editor)                                           [Page 11] 
 

 
Internet Draft                   SUA                     June 30, 2002 
 
     -    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. The SG/AS needs 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 supporting 
   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   
    -     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).  
    
 
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   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): 
    
   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 6.1.1.3.1 (Tab 7/Q.711)     
               |Indication|ANSI-T1.112 Chap 2.1.1.2.5 (Tab 6A/T1.112.1) 
   ------------+----------+------------------------------------------- 
   N-Unit Data |Request   |ITU-Q.711   Chap 6.2.2.3.1 (Tab 10/Q.711)    
               |Indication|ANSI-T1.112 Chap 2.2.2.3.1 (Tab 8A/T1.112.1) 
   ------------+----------+------------------------------------------- 
 
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   N-Notice    |Indication|ITU-Q.711   Chap 6.2.2.3.2 (Tab 11/Q.711)    
               |          |ANSI-T1.112 Chap 2.2.2.3.2 (Tab 8B/T1.112.1) 
    
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 
   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 
 
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   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  
   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. 
 
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   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. 
    
   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. 
 
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   If dynamic registration of RK is supported by the SUA layer, 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 
   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.  
    
3.1 Common Message Header 
    
 
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   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:  
    
      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 
      
 
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   Signalling Network Management (SNM) Messages  
    
     0         Reserved 
     1         Destination Unavailable (DUNA) 
     2         Destination Available (DAVA) 
     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 
      
 
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   Connection-Oriented (CO) Messages  
    
     0         Reserved 
     1         Connection Request (CORE)  
     2         Connection Acknowledge (COAK) 
     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 

 
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     padding bytes, since all parameters contained within this 
     composite parameter will be considered multiples of 4 bytes. 
      
   Parameter Value: variable-length. 
    
     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. 
    
       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                           | 
 
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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         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 
     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            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
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      |                        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 
     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) 
    
   This message is used to acknowledge receipt of data by the peer.  
   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  
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
 
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      |          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 
    
   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                        | 
 
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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         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                         / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         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 
 
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     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. 
    
       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            | 
 
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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                          Importance                           | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0114          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                      Message Priority                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x0103          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                     Destination Address                       / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         Tag = 0x010b          |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                             Data                              / 
      \                                                               \ 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   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. 
    
       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                         / 
      \                                                               \ 
 
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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |         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). 
    
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 
 
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       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 
 
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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), 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.   
                
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 
   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) 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 SSN is not included, the 
              SCON message corresponds to the SCCP N-PCSTATE primitive. 
    
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: 

 
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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 affected destination is currently 
   considered unavailable by the ASP, the peer should be informed that 
   traffic to the affected destination can 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.  

 
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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 = 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) 
    
 
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   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 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |            Tag = 0x0011       |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                        ASP Identifier                         | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |            Tag = 0x0004       |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          / 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     ASP Identifier                Optional *1 
     Info String                   Optional 
    
   Note 1:  ASP Identifier MUST be used where the IPSP/SGP cannot 
            identify the ASP by pre-configured address/port number 
            information (e.g., where an ASP is resident on a Host using 
            dynamic address/port number assignment).   
    
3.5.2 ASP Up Ack (UP ACK) 
    
   The ASP UP Ack message is used to acknowledge an ASP-Up message 
   received from a remote SUA peer. 
    
       0                     1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |            Tag = 0x0004       |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          / 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Info String              Optional 
    
3.5.3 ASP Down (DOWN) 
    
   The ASP Down (DOWN) message is used to indicate to a remote SUA peer 
   that the adaptation layer is not running. 

 
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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 = 0x0004        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          / 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Info String         Optional 
    
3.5.4 ASP Down Ack (DOWN ACK) 
    
   The ASP DOWN Ack message is used to acknowledge an ASP-Down message 
   received from a remote SUA peer. 
    
       0                     1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |           Tag = 0x0004        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                          Info String                          / 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Parameters 
     Info String         Optional 
    
   Note: ASP DOWN ACK will always be sent to acknowledge an ASP DOWN.   
    
3.5.5 Heartbeat (BEAT) 
    
   The Heartbeat message is optionally used to ensure that the SUA 
   peers are still available to each other.  
    
   The format for the BEAT message is as follows: 
    
       0                   1                   2                   3 
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |           Tag = 0x0009        |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      /                       Heartbeat Data                          / 
      \                                                               \ 
      +-+-+-+-+-