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INTERNET-DRAFT                                     J. Loughney Internet
 Engineering Task Force                                           Nokia
                                            G. Sidebottom, Guy Mousseau
Issued:  8 March 2000                                   Nortel Networks
Expires: 8 September 2000                                    S. Lorusso
                                                    Unisphere Solutions


                SS7 SCCP-User Adaptation Layer (SUA)
                <draft-loughney-sigtran-sua-00.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.

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ftp.isi.edu (US West Coast).

Abstract

This Internet Draft defines a protocol for the transport of any SS7
SCCP-User signaling (e.g., TCAP, RANAP, etc.) over IP using the Simple
Control Transport Protocol.  Protocol elements are added to enable a
seamless operation of the SCCP-User peers in the SS7 and IP domains.
This protocol could be used between a Signaling Gateway (SG) and an IP-
based signaling node (or an IP-resident Database).  It is assumed that
the SG receives SS7 signaling over a standard SS7 interface using the
SS7 Signaling Connection Control Part (SCCP) to provide transport from
the SS7 network to the SG.


Internet Draft        SS7 SCCP-User Adaptation Layer      March 8, 2000



1.  Introduction.......................................................4
 1.1 Scope ............................................................4
 1.2 Terminology ......................................................4
 1.3 Signaling Transport Architecture .................................6
  1.3.1 Protocol Architecture for TCAP Transport ......................6
  1.3.2 Protocol Architecture for RANAP Transport .....................6
  1.3.3 IP-Based Signaling Network Architecture .......................7
  1.3.4 ASP Fail-over Model and Terminology ...........................8
 1.4 Services Provided by the SUA Layer ...............................9
  1.4.1 Support for the transport of SCCP-User Messages ...............9
  1.4.2 SCCP Protocol Class Support ...................................9
  1.4.3 Native Management Functions ...................................9
  1.4.4 Interworking with SCCP Network Management Functions ..........10
  1.4.5 Support for the management between the SG and ASP. ...........10
 1.5 Internal Functions Provided in the SUA Layer ....................10
  1.5.1 Address Translation and Mapping at the SG ....................10
  1.5.2 SCTP Stream Mapping ..........................................10
  1.5.3 Congestion Control ...........................................10
 1.6 Definition of SUA Boundaries ....................................10
  1.6.1 Definition of the upper boundary .............................10
  1.6.2 Definition of the lower boundary .............................11
  1.6.3 SUA Peer Messages ............................................11
2 Protocol Elements...................................................11
 2.1 Common Message Header ...........................................11
  2.1.1 SUA Protocol Version .........................................12
  2.1.2 Message Types ................................................12
  2.1.3 Message Length ...............................................13
 2.2 SUA Transfer Messages ...........................................13
  2.2.1 Data Transfer ................................................13
  2.2.2 Data Acknowledge .............................................14
 2.3 Connection Messages .............................................15
  2.3.1 Connection Request ...........................................15
  2.3.2 Connection Acknowledge .......................................16
  2.3.3 Release Request ..............................................17
  2.3.4 Release Complete .............................................18
  2.3.5 Reset Confirm ................................................18
  2.3.6 Reset Request ................................................18
 2.4 SS7 Signaling Network Management Messages .......................19
  2.4.1 Destination Unavailable ......................................19
  2.4.2 Destination Available ........................................19
  2.4.3 Destination State Audit ......................................20
  2.4.4 SS7 Network Congestion .......................................20
  2.4.5 Destination User Part Unavailable ............................21
 2.5 Application Server Process Maintenance Messages .................22
  2.5.1 ASP Up (ASPUP) ...............................................22
  2.5.2 ASP Down (ASPDN) .............................................22
  2.5.3 ASP Active (ASPAC) ...........................................23
  2.5.4 ASP Inactive (ASPIA) .........................................24
  2.5.5 ASP Inactive Ack (ASPIAK) ....................................24
  2.5.6 ASP Takeover (ASPTO) .........................................25
  2.5.7 Notify (NTFY) ................................................26
  2.5.8 No Active ASP (NAASP) ........................................27
 2.6  Management Messages ............................................28
  2.6.1 Error (ERR) ..................................................28
  2.6.2 Audit ........................................................28
  2.6.3 Stream Configuration .........................................29
  2.6.4 Stream Configuration Ack .....................................30
 2.7 Vendor Specific Message .........................................30

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 2.8 Paramters .......................................................32
  2.8.1 Data .........................................................32
  2.8.2 Sequence Number ..............................................32
  2.8.3 Source Reference Number ......................................32
  2.8.4 Destination Reference Number .................................33
  2.8.5 Sending Address ..............................................33
  2.8.6 Destination Address ..........................................33
  2.8.7 Cause ........................................................33
  2.8.8 Protocol Identifier ..........................................33
  2.8.9 Network Appearance ...........................................34
  2.8.10 Affected Destination Point Code .............................34
  2.8.11 Info String .................................................34
  2.8.12 Congestion Level ............................................35
  2.8.13 Adaptation Layer Identifier .................................35
3 Procedures..........................................................35
 3.1 Procedures to support the SUA Services ..........................35
  3.1.1 Receipt of Local primitives ..................................36
 3.2 Procedures to support the SUA Layer Management Services .........36
  3.2.1 Layer Management primitives procedures .......................36
  3.2.2 Receipt of Peer Management messages ..........................36
 3.3 Procedures to support the SUA SCTP Management Services ..........36
  3.3.1 State Maintenance ............................................36
  3.3.2 ASPM procedures for primitives ...............................39
  3.3.3 ASPM procedures for peer-to-peer messages ....................39
 3.4 Procedures to support the SUA Services ..........................40
  3.4.1 At an SG .....................................................40
  3.4.2 At an ASP ....................................................41
4 Examples of SUA Procedures..........................................41
 4.1 Establishment of Association ....................................41
 4.2 ASP fail-over Procedures ........................................41
  4.2.1 For Primary/Backup model .....................................41
  4.3.2 ASP administrative switch-over for Primary/Backup model ......42
 4.3 SUA/SCCP-User Boundary Examples .................................43
  4.3.1 Data Tranfer .................................................43
5 Security............................................................43
 5.1 Introduction ....................................................43
 5.2 Threats .........................................................43
 5.3 Protecting Confidentiality ......................................44
6 IANA Considerations.................................................44
 6.1 SCTP Protocol ID ................................................44
 6.2 Port Number .....................................................44
7 Acknowledgements....................................................44
8 Author's Addresses..................................................44
9 References..........................................................45
ANNEX A:  IP-Endpoint to IP-Endpoint Architecture.....................45















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1.  Introduction

1.1 Scope

There is on-going integration of SCN networks and IP networks.  IP
provides an effective way to transport user data, as well as for
operators to expand their networks.  This document details the delivery
of SCCP-user messages (MAP & CAP over TCAP, RANAP, etc.) over IP, from
an SS7 Signaling Gateway (SG) to an IP-based signaling node (such as an
IP-resident Database) as described in the Framework Architecture for
Signaling Transport [1].  The delivery mechanism SHOULD meet the
following criteria:

*  Support for transfer of SS7 SCCP-User Part messages (e.g., 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 an
   SG and one or more IP-based signaling nodes).
*  Support for distributed IP-based signaling nodes.
*  Support for the asynchronous reporting of status changes to
   management

In other words, the SG will terminate SS7 MTP layers and SCCP layer and
deliver TCAP, RANAP and/or any other SCCP-User protocol messages over
SCTP associations to SCCP-User peers in distributed IP-Based signaling
nodes.  Depending upon the SCCP-users supported, the SUA will need to
support SCCP connectionless service, SCCP connect-orient service or both
services.

1.2 Terminology

Application Server (AS) - A logical entity serving a specific Routing
Key.  An example of an Application Server is a virtual switch element
handling all call processing for a unique range of PSTN trunks,
identified by an SS7 DPC/OPC/SSN.  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 standby process of an Application Server (e.g., part of
a distributed virtual switch 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.

Association - An association refers to an SCTP association.  The
association provides the transport for the delivery of MTP3-User
protocol data units and M3UA adaptation layer peer messages.

Routing Key - At the SG, the Routing Key describes a set of SS7
parameter/parameter-ranges that uniquely defines the range of signaling
traffic configured to be handled by a particular Application Server. An
example would be where a Routing Key consists of a particular DPC and
SSN to which all traffic would be directed to a articular Application
Server.  Routing Keys are mutually exclusive in the sense that a
received SS7 signaling message cannot be directed to more than one
Routing Key.   A Routing Key cannot extend across more than a single SS7

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DPC, in order to more easily support SS7 Management procedures. It is
not necessary for the parameter ranges within a particular Routing Key
to be contiguous.

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 SG and the ASP,
identifying the relevant Application Server.  From the perspective of an
ASP, the Routing Context uniquely identifies the range of traffic
associated with a particular Application Server, which the ASP is
configured to receive from the SG.  There is a 1:1 relationship between
a Routing Context value and a Routing Key at an SG.  Therefore the
Routing Context can be viewed as an index into an SG Table containing
the SG Routing Keys.

Fail-over - The capability to re-route signaling 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-back may apply upon the
return to service of a previously unavailable Application Server
Process.

Signaling Point Management Cluster (SPMC) - A complete set of
Application Servers represented to the SS7 network under the same SS7
Point Code.  SPMCs are used to sum the availability/congestion/User_Part
status of an SS7 destination point code that is distributed in the IP
domain, for the purpose of supporting MTP Level 3 management procedures
at an SG.

Network Appearance - The Network Appearance identifies an SS7 network
context for the purposes of logically separating the signaling traffic
between the SG and the Application Server Processes over a common SCTP
Association.  An example is where an SG is logically partitioned to
appear as an element in four separate national SS7 networks.  A Network
Appearance implicitly defines the SS7 Point Code(s), Network Indicator
and MTP3 protocol type/variant/version used within a specific SS7
network partition. An physical SS7 route-set or link-set at an SG can
appear in only one network appearance. The Network Appearance is not
globally significant and requires coordination only between the SG and
the ASP.

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

Layer Management - Layer Management is a nodal function in an SG or ASP
that handles the inputs and outputs between the M3UA layer and a local
management entity.

Host - The computing platform that the 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 which 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


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defined for each endpoint, but each SCTP endpoint may have multiple IP
addresses.

1.3 Signaling Transport Architecture

The framework architecture that has been defined for SCN signaling
transport over IP [1] uses multiple components, including an IP
transport protocol, a signaling common transport protocol and an
adaptation module to support the services expected by a particular SCN
signaling protocol from its underlying protocol layer.

In general terms, the architecture can be modeled as a client-server
architecture, where SG acts as the server and the ASP acts as the
client.

1.3.1 Protocol Architecture for TCAP Transport

In this architecture, the SCCP and SUA layers interface in the SG. There
needs to be interworking between these layers to provide for the
seamless transfer of the user messages as well as the management
messages.  The SUA handles the SS7 address to IP address mapping.

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

  +------+                                +------+
  | TCAP |                                | TCAP |
  +------+         +------+------+        +------+
  | SCCP |         | SCCP | SUA  |        | SUA  |
  +------+         +------+------+        +------+
  | MTP3 |         | MTP3 |      |        |      |
  +------|         +------+ SCTP |        | SCTP |
  | MTP2 |         | MTP2 |      |        |      |
  +------+         +------+------+        +------+
  |  L1  |         |  L1  |  IP  |        |  IP  |
  +------+         +------+------+        +------+
      |_______________|         |____________|

    TCAP - Transaction Capability Application Protocol
    STP  - SS7 Signaling Transfer Point

1.3.2 Protocol Architecture for RANAP Transport

In this architecture, the SS7 application protocol is invoked at the SG.
For messages destined for an ASP, the SUA handles address translation,
for example by way of Global Title Translation or via mapping table,
resolving the destination specified by SS7 Application to a SCTP
association / IP address.









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

  +------+         +-------------+        +------+
  | S7AP |         |    S7AP     |        | S7AP |
  +------+         +------+------+        +------+
  | SCCP |         | SCCP | SUA  |        | SUA  |
  +------+         +------+------+        +------+
  | MTP3 |         | MTP3 |      |        |      |
  +------|         +------+ SCTP |        | SCTP |
  | MTP2 |         | MTP2 |      |        |      |
  +------+         +------+------+        +------+
  |  L1  |         |  L1  |  IP  |        |  IP  |
  +------+         +------+------+        +------+
      |_______________|         |____________|

    S7AP - SS7 Application Protocol (e.g. - RANAP/RNSAP)
    STP  - SS7 Signaling Transfer Point

This architecture may simplify, in some cases, to carrying an SS7
application protocol between two IP based endpoints.  In this scenario,
full SG functionality may not be needed.  This architecture is
considered in Annex A.

1.3.3 IP-Based Signaling Network Architecture

The Signaling Gateway (SG) is the gateway node between the SS7 network
and the IP network.  The SG will transport SCCP-user signaling traffic
from the SS7 network to the IP-based signaling nodes (for example  IP-
resident Databases).  The SUA protocol does not specify the performance
and reliability requirements needed for the transport of user signaling,
but relies on SCTP and the layers below to provide it.  The SUA protocol
should be flexible enough to allow different configurations and
transport technology to allow the network operators to meet their
operation, management and performance requirements.

It is recommended that when realizing this protocol,  the network
architecture allows for multiple hosts,  to be attached to the SG(s).
Multiple associations can be used between the SGs and hosts to provide
failover scenarios.  Also, it is advisable for several ASPs to be
located within the hosts, again for failover use.
















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Figure 1 shows an example network architecture which can support robust
operation and failover support.


  ********                                          **************
  *      *__________________________________________*  ********  * HOST1
  *      *                                          *  * ASP1 *  *
  *  SG1 *   SCTP Associations                      *  ********  *
  *      *__________________________________________*  ********  *
  *      *                                          *  * ASP2 *  *
  *      *                                          *  ********  *
  *      *_______________________                   *  ********  *
  *      *                       |                  *  * ASP3 *  *
  ********                       |                  *  ********  *
                                 |                  *      .     *
  ********                       |                  *      .     *
  *      *------------------------------------------*            *
  *      *                       |                  *  ********  *
  *  SG2 *    SCTP Associations  |                  *  * ASPn *  *
  *      *____________           |                  *  ********  *
  *      *            |          |                  **************
  *      *________    |          |                  **************
  *      *        |   |          |__________________*  ********  * HOST2
  *      *        |   |                             *  * ASP1 *  *
  ********        |   |                             *  ********  *
                  |   |_____________________________*  ********  *
                  |                                 *  * ASP2 *  *
                  |                                 *  ********  *
                  |_________________________________*  ********  *
                                                    *  * ASP3 *  *
                                                    *  ********  *
                                                    *      .     *
                                                    *      .     *
                                                    *            *
                                                    *  ********  *
                                                    *  * ASPn *  *
                                                    *  ********  *
                                                    **************
                                                           .
                                                           .
                                                           .

                    Figure 1 - Physical Model

1.3.4 ASP Fail-over Model and Terminology

The network address translation and mapping function of the SUA supports
ASP fail-over functions in order to support a high availability of
transaction processing capability.  The SUA at the SG assign a unique
Application Server to all SCCP-user messages incoming from the SS7
network based on some information in the SCCP-user message.  The SUA at
the SG may use a combination of the following information to make the
AS/ASP assignment:

     Destination Point Code (DPC)
     Originating Point Code (OPC)
     Sub-System Number (SSN)
     Global Title (GT)


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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
while any others are inactive but available in the event of failure or
unavailability of the active ASP(s).

The fail-over model supports an "n+k" redundancy model, where "n" ASPs
is the minimum number of redundant ASPs required to handle traffic and
"k" ASPs are available to take over for a failed or unavailable ASP.
Note that "1+1" active/standby redundancy is a subset of this model. A
simplex "1+0" model is also supported as a subset, with no ASP
redundancy.

To avoid a single point of failure, it is recommended that a minimum of
two ASPs be resident in the list, resident in separate physical hosts
and therefore available over different SCTP Associations.

1.4 Services Provided by the SUA Layer

1.4.1 Support for the transport of SCCP-User Messages

The SUA needs to support the transfer of SCCP-user messages. The SUA
layer at the SG needs to seamlessly transport the SCCP-user messages.

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.

     *    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 signaling
          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 may provide management of the underlying SCTP layer to
ensure that SG-ASP transport is available according to the degree
specified by the SCCP-user application.

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.


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1.4.4 Interworking with SCCP Network Management Functions

The SUA layer needs to support the following SCCP network management
functions:

     Coord Request
     Coord Indication
     Coord Response
     Coord Confirm
     State Request
     State Indication
     Pcstate Indication

1.4.5 Support for the management between the SG and ASP.

The SUA layer MUST provide interworking with SCCP management functions
at the SG for seamless inter-operation between the SCN network and the
IP network.  It SHOULD:

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

1.5 Internal Functions Provided in the SUA Layer

1.5.1 Address Translation and Mapping at the SG

SCCP users may present the following options to address their peer
endpoints:

     Global Title
     DPC + SSN
     OPC + SSN

If Global Titles are used, the rules detailed in Annex B of ITU Q.713
[2] should be consulted.

1.5.2 SCTP Stream Mapping

The SUA supports SCTP streams. The SG 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 MUST use stream 0 for SUA management messages.  Stream 0 MUST
support sequenced delivery, in order to preserve the order of management
message delivery.

1.5.3 Congestion Control

1.6 Definition of SUA Boundaries

1.6.1 Definition of the upper boundary


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The following primitives are supported between the SUA and an SCCP-user.

     Connect Request
     Connect Indication
     Connect Responding
     Connect Confirm
     Data Request
     Data Indication
     Expedited Data Request
     Expedited Data Indication
     Disconnect Request
     Disconnect Indication
     Reset Request
     Reset Indication
     Reset Response
     Reset Confirm

1.6.2 Definition of the lower boundary

The upper layer primitives provided by the SCTP are provided in [7].

1.6.3 SUA Peer Messages

     data transfer
     data acknowledge
     connection request
     connection acknowledge
     release request
     release complete
     reset confirm
     reset request
     ASP Up
     ASP Down
     ASP Active
     ASP Inactive
     ASP Takeover
     Notify
     No Active ASP
     Error
     Audit
     Stream Configuration
     Stream Configuration Acknowledge
     Destination Unavailable
     Destination Available
     Destination State Audit
     SS7 Network Congestion State
     Destination User Part Unavailable
     Vendor-Specific Message

2 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.

2.1 Common Message Header

The protocol messages for SCCP-User Adaptation require a message

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structure which contains a version, message type, message length, and
message contents.   This message header is common among all signaling
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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    ver          |   spare     |           msg type            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        message length                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.1.1 SUA Protocol Version

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

      01   SUA version 1.0

2.1.2 Message Types

     Data Transfer Messages

        Data Transfer (DATR)                     0x0501
        Data Acknowledge (DAAC)                  0x0502

     Connection Messages

        connection request (CORE)                0x0601
        connection acknowledge (COAK)            0x0602
        release request (RELRE)                  0x0603
        release complete (RELCO)                 0x0604
        reset confirm (RESCO)                    0x0605
        reset request (RESRE)                    0x0606

     Application Server Process Maintenance (ASPM) Messages

        ASP Up (ASPUP)                           0x0301
        ASP Down (ASPDN)                         0x0302
        ASP Active (ASPAC)                       0x0401
        ASP Inactive (ASPIA)                     0x0402
        ASP Takeover (ASPTO)                     0x0403
        Notify (NTFY)                            0x0404
        No Active ASP (NAASP)                    0x0405

     SUA Management Messages

        Error (ERR)                              0x0001
        Audit (AUD)                              0x0002
        Stream Configuration (SCO)               0x0003
        Stream Configuration Acknowledge (SCA)   0x0004

     SS7 Signaling Network Management (SSNM) Messages

        Destination Unavailable (DUNA)           0x0201
        Destination Available (DAVA)             0x0202
        Destination State Audit (DAUD)           0x0203
        SS7 Network Congestion State (SCON)      0x0204
        Destination User Part Unavailable (DUPU) 0x0205

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      Other

        Vendor-Specific Message (VEN)            0xFFFE

2.1.3 Message Length

The Message Length defines the length of the message in octets,
including the header.

2.2 SUA Transfer Messages

The following section describes the SUA 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.

2.2.1 Data Transfer

This message transfers data between one SUA to another.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | a |b| c | d |                     spare                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       optional parameters                     /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1|             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                             data                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Flags

     A    class
     B    priority
     C    ack
     D    segmentation

The class flag indicates which SCCP class this data transfer is
supporting. The valid values for class are shown in the following table.

     Value      Description
     0x0        Class 0 (connectionless service)
     0x1        Class 1 (connectionless service)
     0x2        Class 2 (connection-oriented service)
     0x3        Class 3 (connection-oriented service)

The priority parameter indicates if the data expects expedited services.
The valid values are:

     Value     Description
     0x0       Normal priority
     0x1       Expedited priority



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The acknowledge flag indicates the receiving end should send an
acknowledgement on receiving the data message.  The valid values are:

     Value     Description
     0x0       No acknowledgement
     0x1       Acknowledge on error
     0x2       Acknowledgement required

The segmentation flag indicates if message segmentation is present.  The
valid values for segmentation are:

     Value     Description
     0x0       No segmentation
     0x1       First piece of segmented data
     0x2       middle piece of segmented data
     0x3       final piece of segmented data

Optional parameters include:

     Sequence number
     source reference number
     destination reference number
     sending address
     destination address

Section 2.8 defines the format (in TLV format) for the optional
paramters.

Implementation note:

This message covers the following SCCP messages: unitdata (UDT),
extended unitdata (XUDT), data form 1 (DT1), data form 2 (DT2),
expedited data (ED), long unitdata (LUDT).

2.2.2 Data Acknowledge

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | a |b| c | d |                     spare                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                      optional parameters                      /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Flags

     A    class
     B    priority
     C    ack
     D    segmentation

The class flag indicates which SCCP class this data transfer is
supporting. The valid values for class are shown in the following table.

     Value      Description
     0x0        Class 0 (connectionless service)

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     0x1        Class 1 (connectionless service)
     0x2        Class 2 (connection-oriented service)
     0x3        Class 3 (connection-oriented service)

The priority parameter indicates if the data expects expedited services.
The valid values are:

     Value     Description
     0x0       Normal priority
     0x1       Expedited priority

The acknowledge flag is set to 0

The segment parameter is set to 0.

Reason code MUST be included.  See section 2.8 for additional
details.

Optional parameters include:

     data
     cause
     sequence number
     destination reference number
     sending address
     destination address

Implementation note:

This message covers the following SCCP messages: protocol data unit
error (ERR), long unitdata service (LUDTS), unitdata service (UDTS),
extended unitdata service (XUDTS), data acknowledgement (AK), expedited
data acknowledgement (EA).

2.3 Connection Messages

The connection messages are used in the connection-oriented services
provided by the SUA, indicated by protocol class 2 or 3.  The release
messages are used only for SCCP-users requesting protocol class 3.

2.3.1 Connection 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | a |b| c | d |                     spare                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   source reference number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0|      Parameter Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                     destination address                       /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       optional paramters                      /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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     Flags

     A    class
     B    priority
     C    ack
     D    segmentation

The class flag indicates which SCCP class this data transfer is
supporting. The valid values for class are shown in the following table.

     Value      Description
     0x2        Class 2 (connection-oriented service)
     0x3        Class 3 (connection-oriented service)

The priority flag indicates if the data expects expedited services.  The
valid values are:

     Value     Description
     0x0       Normal priority
     0x1       Expedited priority

The acknowledge flag is not used, it MUST be set to 0.

The segmentation flag is not used, it MUST be set to 0.

Optional parameters include:

     Data
     Sending Address

2.3.2 Connection Acknowledge

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | a |b| c | d |                     spare                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 destination reference number                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Flags

     A    class
     B    priority
     C    ack
     D    segmentation

The class flag indicates which SCCP class this data transfer is
supporting. The valid values for class are shown in the following table.

     Value      Description
     0x2        Class 2 (connection-oriented service)
     0x3        Class 3 (connection-oriented service)

The priority flag indicates if the data expects expedited services.  The
valid values are:

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     Value     Description
     0x0       Normal priority
     0x1       Expedited priority

The acknowledge flag is not used, it MUST be set to 0.

The segmentation flag is not used, it MUST be set to 0.

Optional parameters include:

     Data
     cause
     Source reference number
     destination reference number
     destination address

Implementation note:

This message covers the following SCCP messages: connection confirm
(CC), connection refused (CREF).

2.3.3 Release 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | a |b| c | d |                     spare                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   source reference number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 destination reference number                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          reason code                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       optional parameters                     /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Flags

     A    class
     B    priority
     C    ack
     D    segmentation

The class flag indicates which SCCP class this data transfer is
supporting. The valid values for class are shown in the following table.

     Value      Description
     0x2        Class 2 (connection-oriented service)
     0x3        Class 3 (connection-oriented service)


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The priority parameter indicates if the data expects expedited services.
The valid values are:

     Value     Description
     0x0       Normal priority
     0x1       Expedited priority

The acknowledge flag is not used, it MUST be set to 0.

The segmentation flag is not used, it MUST be set to 0.

Optional parameters include:

     data
     result

Section 2.8 defines the format (in TLV format) for the optional
paramters.

2.3.4 Release Complete

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | a |b| c | d |                     spare                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   source reference number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 destination reference number                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     All flags MUST be set to 0.

2.3.5 Reset Confirm

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | a |b| c | d |                     spare                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   source reference number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 destination reference number                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     All flags MUST be set to 0.

2.3.6 Reset Request




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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | a |b| c | d |                     spare                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   source reference number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 destination reference number                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          reason code                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     All flags MUST be set to 0.

2.4 SS7 Signaling Network Management Messages

2.4.1 Destination Unavailable

The DUNA message is sent from the SG to all concerned ASPs to indicate
that the SG has determined that an SS7 destination is unreachable.  The
MTP3-User at the ASP is expected to stop traffic to the affected
destination through the SG 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Affected DPC                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       optional parameters                     /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


The DUNA message contains the following parameters:

     Affected Destination Point Code

Optional parameters include:

     Protocol Identifier
     Network Appearance
     Info String

2.4.2 Destination Available

The DAVA message is sent from the SG to all concerned ASPs to indicate
that the SG has determined that an SS7 destination is now reachable. The
ASP MTP3-User protocol is expected to resume traffic to the affected
destination through the SG initiating the DUNA.

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Affected DPC                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       optional parameters                     /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


The DUNA message contains the following parameters:

     Affected Destination Point Code

Optional parameters include:

     Protocol Identifier
     Network Appearance
     Info String

2.4.3 Destination State Audit

The DAUD message can be sent from the ASP to the SG to query the
availability state of the SS7 routes to an affected destination.  A
DAUD may be  sent periodically after the ASP has received a DUNA, until
a DAVA is received.   The DAUD can also be sent when an ASP recovers
from isolation from the SG.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Affected DPC                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       optional parameters                     /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


The DUNA message contains the following parameters:

     Affected Destination Point Code

Optional parameters include:

     Protocol Identifier
     Network Appearance
     Info String

2.4.4 SS7 Network Congestion

The SCON message can be sent from the SG 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Affected DPC                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       optional parameters                     /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


The DUNA message contains the following parameters:

     Affected Destination Point Code

Optional parameters include:

     Protocol Identifier
     Network Appearance
     Info String
     Congestion Level

Implementation note:

This message covers the following SCCP message: subsystem congested
(SSC).

2.4.5 Destination User Part Unavailable

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

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Affected DPC                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          reason code                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       optional parameters                     /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The DUPU message contains the following parameters:

     Affected Destination Point Code
     Reason

Optional parameters include:

     Protocol Identifier
     Network Appearance
     Info String


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2.5 Application Server Process Maintenance Messages

2.5.1 ASP Up (ASPUP)

The ASP UP (ASPUP) message is used to indicate to a remote M3UA peer
that the Adaptation layer is ready to receive traffic or maintenance
messages.

The ASPUP message contains the following parameters:

     Adaptation Layer Identifier (optional)
     INFO String (optional)

The format for ASPUP 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 (0x2)           |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Adaptation Layer Identifier*                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Tag (0x3)           |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          INFO String*                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The optional Adaptation Layer Identifier (ALI) is a string that
identifies the adaptation layer.  This string MUST be set to "SUA" which
results in a length of 4.  The ALI would normally only be used in the
initial ASP Up message across a new SCTP association to ensure both
peers are assuming the same adaptation layer protocol.

Note: Strings are padded to 32-bit boundaries.  The length field
indicates the end of the string.

2.5.2 ASP Down (ASPDN)

The ASP Down (ASPDN) message is used to indicate to a remote M3UA peer
that the adaptation layer is not ready to receive traffic or maintenance
messages.

The ASPDN message contains the following parameters:

     Reason
     INFO String (Optional)

The format for the ASPDN 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              Reason                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Tag (0x4)           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         INFO String*                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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The format and description of the optional Info String parameter is the
same as for the DUNA message (See Section 2.3.2.1.)

The Reason parameter indicates the reason that the remote SUA adaptation
layer is unavailable.  The valid values for Reason are shown in the
following table.

     Value      Description
     0x1        Processor Outage
     0x2        Management Inhibit

Implementation note:

This message covers the following SCCP message: subsystem-prohibited
(SSP).

2.5.3 ASP Active (ASPAC)

The ASPAC message is sent by an ASP to indicate to an SG that it is
Active and ready to be used.

The ASPAC message contains the following parameters:

     Routing Context (Optional)
     INFO String (Optional)

The format for the ASPAC 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 (0xx)             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Type                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Routing Context*                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag (0x4)             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          INFO String*                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


The Type parameter identifies the ASPAC as an Over-ride or Load-share
Active message.  The valid values for Type are shown in the following
table.

     Value          Description
     0x1            Over-ride
     0x2            Load-share

Within a particular Routing Context, only one Type can be used.  An SG
that receives an ASPAC with an incorrect type for a particular Routing
Context will respond with an Error Message.

The optional Routing Context parameter contains (a list of) integers
indexing the Application Server traffic that the sending ASP is
configured to receive.  There is one-to-one relationship between an
index entry and an AS Name.  Because an AS can only appear in one

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Network Appearance, the Network Appearance parameter is not required in
the ASPAC message

An Application Server Process may be configured to process traffic for
more than one logical Application Server.  From the perspective of an
ASP, a Routing Context defines a range of signaling traffic that the ASP
is currently configured to receive from the SG.  For example, an ASP
could be configured to support call processing for multiple ranges of
PSTN trunks and therefore receive related signaling traffic, identified
by separate SS7 DPC/OPC.

The format and description of the optional Info String parameter is the
same as for the DUNA message.

Implementation note:

This message covers the following SCCP message: subsystem-allowed (SSA).

2.5.4 ASP Inactive (ASPIA)

The ASPIA message is sent by an ASP to indicate to an SG that it is no
longer an active ASP to be used from within a list of ASPs.  The SG will
respond with an ASPIA message and either discard incoming messages or
buffer for a timed period and then discard.

The contains the following parameters:

     Routing Context (Optional)
     INFO String (Optional)

The format for the ASPIA 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 (0xx)           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Routing Context                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Tag (04)           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          INFO String*                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The format and description of the optional Routing Context and Info
String parameters is the same as for the ASPAC message.

Implementation note:

This message covers the following SCCP message: subsystem-out-of-
service-request (SOR).

2.5.5 ASP Inactive Ack (ASPIAK)

The ASPIAK message is sent by the SG in response to an ASPIA to the
sending ASP that it acknowledges the ASPIA.

The contains the following parameters:


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     Routing Context (Optional)
     INFO String (Optional)

The format for the ASPIAK 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 (0xx)           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Routing Context                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Tag (04)           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          INFO String*                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


Implementation note:

This message covers the following SCCP message: subsystem-out-of-
service-grant (SOG).

2.5.6 ASP Takeover (ASPTO)

The ASPTO message is sent by an ASP to indicate to an SG that it will be
replacing an active ASP, in a controlled manner.

The ASPTO message contains the following parameters:

     Routing Context (Optional)
     ASP id (Optional)
     INFO String (Optional)

The format for the ASPAC 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 (0xx)             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                           ASP id*                             /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       Routing Context*                        /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag (0x4)             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                          INFO String*                         /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


The optional ASP id parameter identifies an ASP, that will be taken over
by the ASP that is sending this message. SG would keep sending traffic
to both the ASPs for some time. Either because of a timer or an explicit
ASPIA message from the taken over ASP, the SG would remove that ASP from
the active ASPs list. During the time when both ASPs receive traffic,

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all messages/traffic corresponding to new transactions/calls will be
sent to the new ASP and traffic corresponding to the continued work
would be sent to the old ASP.

The optional Routing Context parameter contains (a list of) integers
indexing the Application Server traffic that the sending ASP is
configured to receive.  There is one-to-one relationship between an
index entry and an AS Name.  Because an AS can only appear in one
Network Appearance, the Network Appearance parameter is not required in
the ASPAC message

An Application Server Process may be configured to process traffic for
more than one logical Application Server.  From the perspective of an
ASP, a Routing Context defines a range of signaling traffic that the
ASP is currently configured to receive from the SG.  For example, an
ASP could be configured to support call processing for multiple ranges
of PSTN trunks and therefore receive related signaling traffic,
identified by separate SS7 DPC/OPC_ranges.

The format and description of the optional Info String parameter is the
same as for the DUNA message.

2.5.7 Notify (NTFY)

The NTFY message is sent by an SG to indicate any change of status in
the AS or ASP to an ASP. SG sends this message to all concerned ASPs in
an AS.

The NTFY message contains the following parameters:

     Status Type
     Status Id
     INFO String (Optional)

The format for the NTFY 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 (0xx)             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Status Type           |         Status Id             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       Routing Context*                        /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Tag (0x4)             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                          INFO String*                         /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


The Status Type parameter identifies the type of the status that is
being notified. The valid values are shown in the following table.

     Value         Description
     0x1           AS_STATE_CHANGE

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     0x2           ASP_STATE_CHANGE

The Status Id parameter identifies the status that is being notified.
The valid values are shown in the following table.

If the Status Type is AS_STATE_CHANGE

     Value         Description
     0x1           AS_DOWN
     0x2           AS_UP
     0x3           AS_PART_ACTIVE
     0x4           AS_ACTIVE
     0x5           AS_PENDING


If the Status Type is ASP_STATE_CHANGE

     Value         Description
     0x1           ASP_DOWN
     0x2           ASP_UP
     0x3           ASP_ACT_NEW
     0x4           ASP_ACT_OLD
     0x5           AS_ACTIVE

The format and description of the optional Routing Context and Info
String parameters is the same as for the ASPAC message.

2.5.8 No Active ASP (NAASP)

The NAASP message is sent by the SG when there are no active ASPs within
an AS. The determination on whether to send a NAASP message occurs when
an ASP moves from Active to Inactive.  When this occurs, if there are no
other ASPs in the active state, then the NAASP message is sent to every
ASP defined within the AS.

The NAASP message contains the following parameters:

     AS Definition (Mandatory)
     INFO String (Optional)

The format for the NAASP 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 (0xx)           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                        AS Definition                          /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Tag (0x4)                   |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                          INFO String*                         /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The format of the AS Definition field is implementation-dependent, and
therefore is specific to individual configurations.  This field is an


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unstructured text string that carries the AS name and its associated
ASPs.

The following is an example.

AS Definition string
{
  AS: boston_region
  {
    ASP1:  primary segment1
    ASP2:  backup segment1
    ASP3:  primary segment2
    ASP4:  backup segment2
    ...
  }
}

2.6  Management Messages

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

2.6.1 Error (ERR)

The ERR message is sent when an invalid value is found in an incoming
message.

The ERR message contains the following parameters:

     Error Code

The format for the ERR 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Message Type =             |          length               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Error Code                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The Error Code can be one of the following values:

     Invalid Version                        0x1
     Invalid Network Appearance             0x2
     Invalid SCN Version                    0x3
     Invalid Adaptation Layer Identifier    0x4
     Invalid Stream Identifier              0x5
     Invalid Message Type                   0x6

2.6.2 Audit









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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | a |b| c | d |                     spare                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                      Optional Parameters                      /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Flags

     A    class
     B    priority
     C    ack
     D    segmentation

The class flag indicates which SCCP class this data transfer is
supporting. The valid values for class are shown in the following table.

     Value      Description
     0x0        Class 0 (connectionless service)
     0x1        Class 1 (connectionless service)
     0x2        Class 2 (connection-oriented service)
     0x3        Class 3 (connection-oriented service)

The priority flag MUST be set to 0.

The acknowledge flag MUST be set to 0.

The segmentation flag MUST be set to 0.

Optional parameters include:

     sending address
     destination address

Implementation note:

This message covers the following SCCP messages: inactivity test (IT),
subsystem-status-test (SST).

2.6.3 Stream Configuration

The Stream Configuration message allows for an ASP to indicate what
which streams are supported and what range of traffic they can handle.
Traffic ID is a locally configured variable, it has only local
significance.  It must be configured in the ASP and in the SG.  A value
of 0 indicates that any traffic may be supported on the stream.

The SCO message contains the following parameters:

      Number of Streams
      Stream ID
      Traffic ID

The format for the SCO message 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Message Type =             |          length               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      number of streams                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           stream id           |         Traffic ID            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                             . . .                             /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.6.4 Stream Configuration Ack

The Stream Configuration Ack message acknowledges the Stream
Configuration message.

The SCA message contains the following parameters:

      Number of Streams
      Stream ID
      Traffic ID

The format for the SCO message is as follows:

      Result
      Data (optional)

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Message Type =             |          length               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            result                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                             DATA                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The Result parameter can be one of the following values:

      Success                               0x0
      Failure                               0x1

The Data parameter contains a list of stream IDs and Traffic IDs that
the SG can support.

2.7 Vendor Specific Message

This is to allow vendors to support their own extended message not
defined by the IETF. It MUST not affect the operation of the SUA.

Endpoints not equipped to interpret the vendor-specific messages sent by
a remote endpoint MUST ignore it (although it may be reported).
Endpoints that do not receive desired vendor-specific information SHOULD
make an attempt to operate without it, although they may do so (and
report they are doing so) in a degraded mode.


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A summary of the Vendor-specific extension format is shown below. The
fields are transmitted from left to right.

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     Message Type = 0xFFFE     |      Parameter Length         |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |                          Vendor-Id                            |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  \                                                               \
  /                        Parameter Value                        /
  \                                                               \
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Type: 16 bit u_int

     0xFFFE for all Vendor-Specific parameters.

  Length: 16 bit u_int

     Indicate the size of the parameter in octets, including the
     Type, Length, Vendor-Id, and Value fields.

  Vendor-Id: 32 bit u_int

     The high-order octet is 0 and the low-order 3 octets are the
     SMI Network Management Private Enterprise Code of the Vendor
     in network byte order, as defined in the Assigned Numbers (RFC
     1700).

  Value: variable length

     The Value field is one or more octets.  The actual format of the
     information is site or application specific, and a robust
     implementation SHOULD support the field as undistinguished
     octets.

     The codification of the range of allowed usage of this field is
     outside the scope of this specification.

     It SHOULD be encoded as a sequence of vendor type / vendor length
     / value fields, as follows.  The parameter field is dependent on
     the vendor's definition of that attribute.  An example encoding
     of the Vendor-Specific attribute using this method 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Parameter Type = 0xFFFE    |      Parameter Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Vendor-Id                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          VS-Type              |             VS-Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                          VS-Value                             /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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   VS-Type: 16 bit u_int

     This field identifies the parameter included in the VS-Value
     field. It is assigned by the vendor.

   VS-Length: 16 bit u_int

     This field is the length of the vendor-specific parameter and
     Includes the VS-Type, VS-Length and VS-Value (if included) fields.

   VS-Value:  Variable Length

     This field contains the parameter identified by the VS-Type field.
     It's meaning is identified by the vendor.

2.8 Paramters

     Parameter Name                     Parameter ID
     ==============                     ============
     Data                               0x0001
     Sequence Number                    0x0002
     Source Reference Number            0x0003
     Destination Reference Number       0x0004
     Source Address                     0x0005
     Destination Address                0x0006
     Cause                              0x0007

2.8.1 Data

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1|            length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                             data                              /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.8.2 Sequence Number

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Sequence number                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.8.3 Source Reference Number

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   source reference number                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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2.8.4 Destination Reference Number

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 destination reference number                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.8.5 Sending Address

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1|      Parameter Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                       sending address                         /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.8.6 Destination Address

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0|      Parameter Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                     destination address                       /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.8.7 Cause

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          reason code                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Reason code may be one of the following reasons:

     Invalid Version                        0x1
     Invalid Network Appearance             0x2
     Invalid SCN Version                    0x3
     Invalid Adaptation Layer Identifier    0x4
     Invalid Stream Identifier              0x5
     Invalid Message Type                   0x6

2.8.8 Protocol Identifier

The Protocol Identifier parameter identifies the SCCP version/variant.






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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          protocol id                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.8.9 Network Appearance

The Network Appearance parameter identifies the SS7 network
context for the message, for the purposes of logically separating
the signaling traffic between the SG and the Application Server
Processes over common SCTP Associations.  An example is where an
SG is logically partitioned to appear as an element in four
different national SS7 networks.  A Network Appearance implicitly
defines the SS7 Destination Point Code used, the SS7 Network
Indicator value and SCCP/SCCP-User protocol type/variant/version
used within the SS7 network partition.  Where an SG operates in
the context of a single SS7 network, or individual SCTP
associations are dedicated to each SS7 network appearance, the
Network Appearance parameter is not required.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        network appearance                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.8.10 Affected Destination Point Code

The Affected DPC is provisionally a three-octet parameter to allow 14-,
16- and 24-bit binary formatted SS7 Point Codes.  Where the Affected
Point Code is less than 24-bits, it is padded on the left to the 24-bit
boundary.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Affected DPC                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.8.11 Info String

The INFO String parameter can carry any meaningful 8-BIT ASCII character
string along with the message.  Length of the INFO String parameter is
from 0 to 255 characters.  No procedures are presently identified for
its use but the INFO String may be used by Operators for debugging
purposes.







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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1|            length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /                          info string                          /
   \                                                               \
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2.8.12 Congestion Level

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       congestion level                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The valid values for the optional Congestion Level parameter are shown
in the following table.

                Value       Description
                 00     No Congestion or Undefined
                 01     Congestion Level 1
                 02     Congestion Level 2
                 03     Congestion Level 3

2.8.13 Adaptation Layer Identifier

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              ALI                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The optional Adaptation Layer Identifier (ALI) is a string that
identifies the adaptation layer.  This string MUST be set to "SUA" which
results in a length of 3.  The ALI would normally only be used in the
initial ASP Up message across a new SCTP association to ensure both
peers are assuming the same adaptation layer protocol.

3 Procedures

The SUA layer needs to respond to various local primitives it receives
from other layers as well as the messages that it receives from the peer
SUA layers.  This section describes the SCU procedures in response to
these events.

3.1 Procedures to support the SUA Services

These procedures support the SUA transport of SCCP-User/SCCP boundary
primitives.





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3.1.1 Receipt of Local primitives

3.2 Procedures to support the SUA Layer Management Services

3.2.1 Layer Management primitives procedures

3.2.2 Receipt of Peer Management messages

3.3 Procedures to support the SUA SCTP Management Services

These procedures support the SUA management of SCTP Associations and ASP
Paths between SGs and ASPs

3.3.1 State Maintenance

The M3UA layer on the SG needs to maintain the state of each ASP as
input to the SGs address translation and mapping function.

3.3.1.1  ASP States

The state of each ASP is maintained in the M3UA layer in the SG. The
state of an ASP changes due to events. The events include:

   * Reception of messages from that ASP's M3UA layer
   * Reception of messages from a different ASP's M3UA layer
   * Reception of indications from the SCTP layer
   * Switch over timer triggers

The ASP state transition diagram is shown in Figure 4.  The possible
states of an ASP are:

ASP-DOWN: The Application Server Process is unavailable.  Initially all
ASPs will be in this state.

ASP-UP: The Application Server Process is available but application
traffic is stopped.

ASP-ACTIVE: The Application Server Process is available and application
traffic is active.

ASP-ACT-OLD: The Application Server Process is available and application
traffic is active for continued work only.

ASP-ACT-NEW: The Application Server Process is available and application
traffic is active for new work only.














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                 Figure 4: ASP State Transition Diagram

                                  +-------------+
           +----------------------|             |
           |       Some other    /|  ASP-ACTIVE |<--------+
           |       ASP        /   +-------------+         |
           |       Takeover  /        ^     |             | Ts
           |               /   ASP    |     | ASP         |
           |              /    Active |     | Inactive    |
           |             v            |     v             |
           | +-------------+      +-------------+       +-------------+
           | |             |      |             |       |             |
           | | ASP-ACT-OLD |----->|  ASP-UP     |------>| ASP-ACT-NEW |
           | +-------------+ Ts / +-------------+ ASP   +-------------+
           |    |    ASP Inactive  ^    |        Takeover   |
           |<---|                  |    |                   |
           |                       |    |                   |
 ASP Down/ |                  ASP  |    | ASP Down /        | ASP
 SCTP CDI  |                  Up   |    | SCTP CDI          | Down/
           |                       |    v                   | SCTP
           |                   +-------------+              | CDI
           |                   |             |              |
           +------------------>|             |<-------------+
                               |  ASP-DOWN   |
                               +-------------+


SCTP CDI: The local SCTP layer's Communication Down Indication to the
Upper Layer Protocol (M3UA) on an SG. The local SCTP will send this
indication when it detects the loss of connectivity to the ASP's SCTP
layer.

Ts: Switch over Timer Triggers

3.3.1.2  AS States

The state of the AS is maintained in the M3UA layer on the SG.

The state of an AS changes due to events. These events include:

   * ASP state transitions
   * Recovery timer triggers

The possible states of an AS are:

AS-DOWN: The Application Server is unavailable.  This state implies
that all related ASPs are in the ASP-DOWN state for this AS. Initially
the AS will be in this state.

AS-UP: The Application Server is available but no application traffic
is active (i.e., one or more related ASPs are in the ASP-UP state, but
none in the ASP-Active state).

AS-ACTIVE: The Application Server is available and application traffic
is active.  This state implies that one ASP is in the ASP-ACTIVE state.

AS-PENDING: An active ASP has transitioned from active to inactive or
down and it was the last remaining active ASP in the AS. A recovery


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timer T(r) will be started and all incoming SCN messages will be queued
by the SG. If an ASP becomes active before T(r) expires, the AS will
move to AS-ACTIVE state and all the queued messages will be sent to the
active ASP.

If T(r) expires before an ASP becomes active, the SG stops queuing
messages and  discards all previously queued messages. The AS will move
to AS-UP if at least one ASP is in ASP-UP state, otherwise it will move
to AS-DOWN state.


                 Figure 5: AS State Transition Diagram


                             +--------------------------------------+
                             |                                      |
                             V                                      |
                       +-------------+                              |
                       |             |                              |
                       | AS-PART-ACT |----------------------------+ |
                     ->|             |     Last ACTIVE ASP        | |
      N <> 1 and    /  |             |     trans to UP or DOWN    | |
      an ASP trans/    +-------------+                            | |
      ACTIVE    /                  \  ^                           | |
              /         Nth ASP      \  \   N <> 1 and            | |
            /           trans ACTIVE   \  \  Nth ACTIVE ASP       | |
           /                             \  \  trans to UP        | |
         /                                 \  \  or DOWN          | |
        /           N = 1 and                V  \                 | |
      +----------+  one ASP trans ACTIVE   +-------------+        | |
      |          |------------------------>|             |        | |
      |  AS-UP   |                         |  AS-ACTIVE  |        | |
      |          |                         |             |        | |
      |          |<                       -|             |        | |
      +----------+ \                     / +-------------+        | |
         ^   |      \ Tr Trigger        /       ^    |            | |
         |   |       \ at least one    /        |    |            | |
         |   |        \ ASP in UP     /         |    |            | |
         |   |         \             /          |    |            | |
         |   |          \           /           |    |            | |
         |   |           \     /---/   N=1 and  |    | Last       | |
 one ASP |   |            \   /        one ASP  |    | ACTIVE ASP | |
 trans   |   | all ASP     \-/----\    trans to |    | trans to   | |
 to UP   |   | trans to     /      \   ACTIVE   |    | UP or DOWN | |
         |   | DOWN        /        \           |    |            | |
         |   |            /          \          |    |            | |
         |   |           /            \         |    |            | |
         |   |          /all ASP       \        |    |            | |
         |   v         / trans to       \       |    v            | |
      +----------+    /  DOWN            \ +-------------+        | |
      |          |<--/                    -|             |        | |
      | AS-DOWN  |                         | AS-PENDING  |<-------+ |
      |          |                         |  (queuing) |          |
      |          |<------------------------|             |----------+
      +----------+    Tr Trigger no ASP    +-------------+ N <> 1 and
                       in UP state                an ASP trans ACTIVE

    Tr = Recovery Timer


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3.3.2 ASPM procedures for primitives

Before the establishment of an SCTP association the ASP state at both
the SG and ASP is assumed to be "Down".

When the SUA layer receives an M-SCTP ESTABLISH request primitive from
the Layer Management, the SUA layer will try to establish an SCTP
association with the remote SUA peer.  Upon reception of an eventual
SCTP-Communication Up confirm primitive from the SCTP, the SUA layer
will invoke the primitive M-SCTP ESTABLISH confirm to the Layer
Management.

Alternatively, if the remote SUA-peer establishes the SCTP association
first, the SUA layer will receive an SCTP Communication Up indication
primitive from the SCTP. The SUA layer will then invoke the primitive M-
SCTP ESTABLISH indication to the Layer Management.

Once the SCTP association is established, The SUA layer at an ASP will
then find out the state of its local SUA-user from the Layer Management
using the primitive M-ASP STATUS.  Based on the status of the local SUA-
User, the local ASP SUA Application Server Process Maintenance (ASPM)
function will initiate the ASPM procedures, using the ASP-Up/-Down/-
Active/-Inactive messages to convey the ASP-state to the SG - see
Section 3.3.3.

If the SUA layer subsequently receives an SCTP-Communication Down
indication from the underlying SCTP layer, it will inform the Layer
Management by invoking the M-SCTP STATUS indication primitive. The state
of the ASP will be moved to "Down" at both the SG and ASP.

At an ASP, the Layer Management may try to reestablish the SCTP
association using M-SCTP ESTABLISH request primitive.

3.3.3 ASPM procedures for peer-to-peer messages

3.3.3.1 ASP-Up

The SG will mark the path as up if an explicit ASP UP (ASPUP) message is
received and internally the path is allowed to come up (i.e., not in a
locked local maintenance state). An ASP UP (ASPUP) message will be sent
to acknowledge the received ASPUP. The SG will respond to a ASPUP with a
ASPDN message if the path is in a locked maintenance state.

The SG will send a ASPUP message in response to a received ASPUP message
from the ASP even if that path was already marked as UP at the SG.

The paths are controlled by the ASP. The SG will only send ASPUP in
response to the reception of a ASPUP message.

The ASP will send ASPUP messages every 2 (add text regarding this being
a configurable timer) seconds until the path comes up (i.e. until it
receives a ASPUP message from the SG for that path).  The ASP may decide
to reduce the frequency (say to every 5 seconds) if the an
acknowledgement is not received after a few tries.

The ASP should wait for the ASPUP message from the SG before
transmitting ASP maintenance messages (ASPIA or ASPAC) or SUA messages


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or it will risk message loss.  The ASPUP message received from the SG is
not acknowledged by the ASP.

3.3.3.2 ASP Down

The SG will mark the ASP as down and send a ASPDN message to the ASP if
one of the following events occur:

     - an ASP Down(ASPDN) message is received from the ASP,
     - the ASP is locked by local maintenance.

The SG will also send a ASPDN message when the ASP is already down and a
ASPDN) message is received from the ASP.

The ASP will send ASPDN whenever it wants to take down a ASP.  Since the
ASPDN messages to the SG or the ASPDN responses from the SG can be lost
(for example, during a node failover), the ASP can send ASPDN messages
every 2 seconds until the path comes down (i.e. until it receives a
ASPDN message from the SG for that path).


3.3.3.3 ASP Version Control

If a ASP Up message with an unknown version is received, the receiving
end will respond with an Error message.  This will indicate to the
sender which version the receiving node supports.

This is useful when protocol version upgrades are being performed.  A
node with the newer version should support the older versions used on
other nodes it is communicating with.

The version field in the Error message header associated will indicate
the version supported by the node.

3.3.3.4 ASP Active

When an ASP Active (ASPAC) message is received, the SG will start
routing to that ASP.  Reception of a ASPAC message overrides any
previous ASPAC messages and results in the ASP associated with the ASPAC
message to become the newly active ASP.

3.3.3.5 ASP Inactive

When a ASPIA message is received, message transmission to that ASP
ceases.  The SG will either discard all incoming messages or start
buffering the incoming messages for T(r)seconds after which messages
will be discarded.

If the ASP is down, all of the Paths that were supported by that ASP
are, by default, down.

3.4 Procedures to support the SUA Services

3.4.1 At an SG

Details to be provided.




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3.4.2 At an ASP

Details to be provided.

4 Examples of SUA Procedures

4.1 Establishment of Association

     SG               ASP1                ASP2
                      (Primary)           (Backup)
      |                  |                   |
      <----ASP Up--------+                   |
      +----ASP Up (Ack)-->                   |
      |                  |                   |
      <-----------------------ASP Up---------+
      +-----------------------ASP Up (Ack)--->
      |                  |                   |
      <----ASP Active----+                   |
      +-ASP Active Ack--->                   |
      |                  |                   |

4.2 ASP fail-over Procedures

4.2.1 For Primary/Backup model

      SG               ASP1                ASP2
                      (Primary)           (Backup)
      |                  |                   |
      <----ASP Up--------+                   |
      +----ASP Up (Ack)-->                   |
      |                  |                   |
      <-----------------------ASP Up---------+
      +-----------------------ASP Up (Ack)--->
      |                  |                   |
      <----ASP Active----+                   |
      +-ASP Active Ack--->                   |
      |                  |                   |
      +-Stream1 Proceed-->                   |
      +-Stream2 Proceed-->                   |
      |       ...        |                   |
      +-StreamN Proceed-->                   |
      |                  |                   |
      |   Backhaul       |                   |
      <===  Flow   ======>                   |
      |    Begins        |                   |
      |                  |                   |
      |               *********              |
      |               *Failure*              |
      |               *Occurs *              |
      |  SCTP         *********   ASP1       |
      <--Communication   |        Failure --->
      |  Down            |        Detection  |
      |                  |                   |
   SG locally            |                   |
   changes ASP1          |                   |
   to Inactive/Down      |                   |
      |                  |                   |
      +----+      ***************            |
      | Queue     *Backhaul Flow*            |

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      | Msgs      *Suspended    *            |
      <----+      ***************            |
      |                  |                   |
      +--No Active ASP--->                   |
      +--------------------No Active ASP----->
      |                  |                   |
      <---------------------ASP Active-------+
      +---------------------ASP Active (Ack)->
      |                  |                   |
      +-Stream1 Proceed---------------------->
      +-Stream2 Proceed---------------------->
      |       ...        |                   |
      +-StreamN Proceed---------------------->
      |                  |                   |
      <=====================Backhaul Flow====>
      |                  |     Resumes       |

4.3.2 ASP administrative switch-over for Primary/Backup model


     SG               ASP1                ASP2
                     (Primary)           (Backup)
     |                  |                   |
     <----ASP Up--------+                   |
     +----ASP Up (Ack)-->                   |
     |                  |                   |
     <-----------------------ASP Up---------+
     +-----------------------ASP Up (Ack)--->
     |                  |                   |
     <----ASP Active----+                   |
     +-ASP Active Ack--->                   |
     |                  |                   |
     |  **********      |                   |
     |  *Backhaul*      |                   |
     <==*  Flow  *======>                   |
     |  * Begins *      |                   |
     |  **********      |                   |
     |                  |                   |
     <--ASP Inactive----+                   |
     |                  |                   |
     +-Stream1 Inhibit-->                   |
     +-Stream2 Inhibit-->                   |
     |       ...        |                   |
     +-StreamN Inhibit-->                   |
     |                  |                   |
     +-ASP Inactive Ack->                   |
     |                  |                   |
     |                  |  ASP1 to ASP2     |
     |                  +--State Transfer--->
     |                  |                   |
     +----+      ***************            |
     | Queue     *Backhaul Flow*            |
     | Msgs      *Suspended    *            |
     <----+      ***************            |
     |                  |                   |
     +--No Active ASP--->                   |
     +------------------+-No Active ASP----->
     |                  |                   |
     <---------------------ASP Active-------+

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     +---------------------ASP Active (Ack)->
     |                  |                   |
     +-Stream1 Proceed---------------------->
     +-Stream2 Proceed---------------------->
     |       ...        |                   |
     +-StreamN Proceed---------------------->
     |                  |                   |
     <=====================Backhaul Flow====>
     |                  |     Resumes       |


4.3 SUA/SCCP-User Boundary Examples

4.3.1 Data Tranfer

This is an example of data tranfer, assuming associations are already
established.

     SEP                SG                  ASP
      |                  |                   |
      +--------UDT------->                   |
      |                  +-------DATR-------->
      |                  |                   |


5 Security

5.1 Introduction

SUA is designed to carry signaling messages for telephony services. As
such, SUA must involve the security needs of several parties: the end
users of the services; the network providers and the applications
involved.  Additional security requirements may come from local
regulation.  While having some overlapping security needs, any security
solution should fulfill all of the different parties' needs.

5.2 Threats

There is no quick fix, one-size-fits-all solution for security.  As a
transport protocol, SUA has the following security objectives:

 * Availability of reliable and timely user data transport.
 * Integrity of user data transport.
 * Confidentiality of user data.

SUA runs on top of SCTP.  SCTP [6] provides certain transport related
security features, such as:

 * Blind Denial of Service Attacks
 * Flooding
 * Masquerade
 * Improper Monopolization of Services

When SUA is running in professionally managed corporate or service
provider network, it is reasonable to expect that this network includes
an appropriate security policy framework. The "Site Security Handbook"
[11] should be consulted for guidance.



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When the network in which SUA runs in involves more than one party, it
may not be reasonable to expect that all parties have implemented
security in a sufficient manner.  In such a case, it is recommended that
IPSEC is used to ensure confidentiality of user payload.  Consult [9]
for more information on configuring IPSEC services.

5.3 Protecting Confidentiality

Particularly for mobile users, the requirement for confidentiality may
include the masking of IP addresses and ports.  In this case application
level encryption is not sufficient; IPSEC ESP should be used instead.
Regardless of which level performs the encryption, the IPSEC ISAKMP
service should be used for key management.

6 IANA Considerations

6.1 SCTP Protocol ID

A request will be made to IANA to assign protocol IDs.  A protocol ID
for the SUA will be registered.

The protocol ID is included in each SCTP data chunk, to indicate which
protocol SCTP is carrying. This protocol ID is not directly used by SCTP
but may be used by certain network entities to identify the type of
information being carried in this DATA chunk.

6.2 Port Number

A request will be made to IANA to assign an SUA Port Number.  This Port
Number is the port which the SG listen to when receiving SCTP datagrams.

7 Acknowledgements

The authors would like to thank Marja-Liisa Hamalainen and Markus
Maanoja for their insightful comments and suggestions.

8 Author's Addresses

John Loughney
Nokia Research Center
PO Box 407
FIN-00045 Nokia Group
Finland
john.loughney@nokia.com

Greg Sidebottom
Nortel Networks
3685 Richmond Rd,
Nepean, Ontario, Canada  K2H 5B7
gregside@nortelnetworks.com

Guy Mousseau
Nortel Networks
3685 Richmond Rd
Nepean, Ontario, Canada  K2H 5B7

Stephen Lorusso
Unisphere Solutions
200 Wheeler Road

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Burlington, MA 01803
USA
SLorusso@unispheresolutions.com

9 References

[1] RFC 2719, "Framework Architecture for Signaling Transport"

[2] ITU-T Recommendations Q.711-714, 'Signaling System No. 7 (SS7) -
    Signaling Connection Control Part (SCCP)'

[3] ANSI T1.112 'Signaling System Number 7 - Signaling Connection
    Control Part'

[4] ITU-T Recommendation Q.771-775 'Signaling System No. 7 SS7) -
    Transaction Capabilities (TCAP)

[5] ANSI T1.114 'Signaling System Number 7 - Transaction Capabilities
    Application Part'

[6] 3G TS 25.413 V3.0.0 (2000-01) 'Technical Specification 3rd
    Generation Partnership Project; Technical Specification Group Radio
    Access Network; UTRAN Iu Interface RANAP Signalling'

[7] Simple Control Transport Protocol <draft-ietf-sigtran-sctp-05.txt>,
    Dec. 1999, Work in Progress

[8] MTP3-User Adaptation Layer <draft-ietf-sigtran-m3ua-01.txt>, Dec.
    1999, Work in Progress

[9] RFC 2401, "Security Architecture for the Internet Protocol", S.
    Kent, R. Atkinson, November 1998.

[10]3G TS 25.420 V3.0.0 (2000-01) "Technical Specification 3rd
    Generation Partnership Project; Technical Specification Group Radio
    Access Network; UTRAN Iur Interface General Aspects and Principles"

[11] RFC 2196, "Site Security Handbook", B. Fraser Ed., September 1997

ANNEX A:  IP-Endpoint to IP-Endpoint Architecture

It is possible for the SUA protocol to be used between two endpoints
located with an IP endpoint.  In this architecture, only IP transport
would be considered.  This may be a likely scenario in an all IP
wireless mobile network.  In this architecture, the model would simplify
to the figure below.














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  ********         ********
  *      *         * IPEP *
  * IPEP *---------*  or  *
  *      *         *IPSTP *
  ********         ********

  +------+         +------+
  | S7AP |         | S7AP |
  +------+         +------+
  | SUA  |         | SUA  |
  +------+         +------+
  | SCTP |         | SCTP |
  +------+         +------+
  |  IP  |         |  IP  |
  +------+         +------+
      |_______________ |
      +----------------+

    S7AP - SS7 Application Protocol (e.g. - RANAP/RNSAP)

It is possible that the IP endpoints would have connections to other
hosts, for signaling transport purposes.  This annex will consider
possible modifications to the SUA protocol.

Details to be provided.

This draft expires September 8, 2000.

































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