Network Working Group Ken Morneault INTERNET-DRAFT Ram Dantu Cisco Systems Greg Sidebottom Nortel Networks Tom George Alcatel Brian Bidulock OpenSS7 Jacob Heitz Lucent Expires in six months July 2001 SS7 MTP2-User Adaptation Layer Status of This Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups MAY also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and MAY be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as 'work in progress'. The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. To learn the current status of any Internet-Draft, please check the '1id-abstracts.txt' listing contained in the Internet- Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast). Abstract This Internet Draft defines a protocol for backhauling of SS7 MTP2 User signaling messages over IP using the Stream Control Transmission Protocol (SCTP). This protocol would be used between a Signaling Gateway (SG) and Media Gateway Controller (MGC). It is assumed that the SG receives SS7 signaling over a standard SS7 interface using the SS7 Message Transfer Part (MTP) to provide transport. The Signaling Gateway would act as a Signaling Link Terminal. Morneault, et al [Page 1] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 TABLE OF CONTENTS 1. Introduction..............................................2 1.1 Scope..................................................2 1.2 Terminology............................................3 1.3 Signaling Transport Architecture.......................3 1.4 Services Provide by the M2UA Adaptation Layer..........6 1.5 Function Provided by the M2UA Layer....................8 1.6 Definition of the M2UA Boundaries......................9 2. Conventions...............................................9 3. Protocol Elements.........................................9 3.1 Common Message Header.................................10 3.2 M2UA Message Header...................................11 3.3 M2UA Messages.........................................11 4. Procedures...............................................20 4.1 Procedures to Support Service in Section 1.4.1........20 4.2 Procedures to Support Service in Section 1.4.2........21 4.3 Procedures to Support Service in Section 1.4.3........21 5. Examples of MTP2 User Adaptation (M2UA) Procedures.......26 5.1 Establishment of associations between SG and MGC......26 examples 5.2 MTP Level 2 / MTP Level 3 Boundary Examples...........28 5.3 Layer Management Communication Examples...............29 6. Timers...................................................30 7. Security.................................................30 8. IANA Considerations......................................31 8.1 SCTP Payload Protocol Identifier.......................31 8.2 IUA Protocol Extensions................................31 9. Acknowledgements.........................................31 10. References...............................................32 11. Author's Addresses.......................................33 Morneault, et al [Page 2] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 1. Introduction 1.1 Scope There is a need for Switched Circuit Network SCN signaling protocol delivery from an Signaling Gateway (SG) to a Media Gateway Controller (MGC) or IP Signaling Point (IPSP). The delivery mechanism SHOULD meet the following criteria: * Support for MTP Level 2 / MTP Level 3 interface boundary * Support for communication between Layer Management modules on SG and MGC * Support for management of SCTP active associations between the SG and MGC The SG will terminate up to MTP Level 2 and the MGC will terminate MTP Level 3 and above. In other words, the SG will transport MTP Level 3 messages over an IP network to a MGC or IPSP. 1.2 Terminology Application Server (AS) - A logical entity serving a specific application instance. An example of an Application Server is a MGC handling the MTP Level 3 and call processing for SS7 links terminated by the Signaling Gateways. Practically speaking, an AS is modeled at the SG as an ordered list of one or more related Application Server Processes (e.g., primary, secondary, tertiary, ...). Application Server Process (ASP) - A process instance of an Application Server. Examples of Application Server Processes are primary or backup MGC instances. Association - An association refers to a SCTP association. The association will provide the transport for the delivery of protocol data units for one or more interfaces. Backhaul - Refers to the transport of signaling from the point of interface for the associated data stream (i.e., SG function in the MGU) back to the point of call processing (i.e., the MGCU), if this is not local [4]. Fail-over - The capability to re-route signaling traffic as required to an alternate Application Server Process 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. Host - The computing platform that the ASP process is running on. Interface - For the purposes of this document, an interface is a SS7 signaling link. Interface Identifier - The Interface Identifier identifies the physical interface at the SG for which the signaling messages are sent/received. The format of the Interface Identifier parameter can be text or integer, the values of which are assigned according to network operator policy. The values used are of local significance only, coordinated between the SG and ASP. Layer Management - Layer Management is a nodal function in an SG or ASP that handles the inputs and outputs between the M2UA layer and a local management entity. Link Key - The link key is a locally unique (between ASP and SG) value that identifies a registration request for a particular Signaling Data Link and Signaling Terminal pair. MTP - The Message Transfer Part of the SS7 protocol. MTP2 - MTP Level 2, the signalling datalink layer of SS7 MTP3 - MTP Level 3, the signalling network layer of SS7 MTP2-User - A protocol that uses the services of MTP Level 2 (i.e. MTP3). Network Byte Order: Most significant byte first, a.k.a Big Endian. Morneault, et al [Page 3] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 Signaling Link Terminal (SLT) - Refers to the means of performing all of the functions defined at MTP level 2 regardless of their implementation [2]. 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. 1.3 M2UA Overview The framework architecture that has been defined for SCN signaling transport over IP [6] uses two components: 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. Within this framework architecture, this document defines a SCN adaptation module that is suitable for the transport of SS7 MTP2 User messages. The only SS7 MTP2 User is MTP3. The M2UA uses the services of the Stream Control Transmission Protocol [5] as the underlying reliable signaling common transport protocol. In a Signaling Gateway, it is expected that the SS7 MTP2-User signaling is transmitted and received from the PSTN over a standard SS7 network interface, using the SS7 Message Transfer Part Level 1 and Level 2 [3,4] to provide reliable transport of the MTP3-User signaling messages to and from an SS7 Signaling End Point (SEP) or Signaling Transfer Point (STP). The SG then provides a inter-working of transport functions with the IP transport, in order to transfer the MTP2-User signaling messages to and from an Application Server Process where the peer MTP2- User protocol layer exists. 1.3.1 Example - SG to MGC In a Signaling Gateway, it is expected that the SS7 signaling is received over a standard SS7 network termination, using the SS7 Message Transfer Part (MTP) to provide transport of SS7 signaling messages to and from an SS7 Signaling End Point (SEP) or SS7 Signaling Transfer Point (STP). In other words, the SG acts as a Signaling Link Terminal (SLT) [2]. The SG then provides interworking of transport functions with IP Signaling Transport, in order to transport the MTP3 signaling messages to the MGC where the peer MTP3 protocol layer exists, as shown below: Morneault, et al [Page 4] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 ****** SS7 ****** IP ******* *SEP *-----------* SG *-------------* MGC * ****** ****** ******* +----+ +----+ |S7UP| |S7UP| +----+ +----+ |MTP + |MTP | | L3 | (NIF) |L3 | +----+ +----+----+ +----+ |MTP | |MTP |M2UA| |M2UA| | | | +----+ +----+ |L2 | |L2 |SCTP| |SCTP| |L1 | |L1 +----+ +----+ | | | |IP | |IP | +----+ +---------+ +----+ NIF - Nodal Interworking Function SEP - SS7 Signaling Endpoint IP - Internet Protocol SCTP - Stream Control Transmission Protocol (Refer to Reference [5]) Figure 1 M2UA in the SG to MGC Application Note: STPs MAY be present in the SS7 path between the SEP and the SG. It is recommended that the M2UA use the services of the Stream Control Transmission Protocol (SCTP) as the underlying reliable common signaling transport protocol. The use of SCTP provides the following features: - explicit packet-oriented delivery (not stream-oriented) - sequenced delivery of user messages within multiple streams, with an option for order-of-arrival delivery of individual user messages, - optional multiplexing of user messages into SCTP datagrams, - network-level fault tolerance through support of multi-homing at either or both ends of an association, - resistance to flooding and masquerade attacks, and - data segmentation to conform to discovered path MTU size There are scenarios without redundancy requirements and scenarios in which redundancy is supported below the transport layer. In these cases, the SCTP functions above MAY NOT be a requirement and TCP can be used as the underlying common transport protocol. 1.3.2 Support for the management of SCTP associations between the SG and ASPs The M2UA layer at the SG maintains the availability state of all configured ASPs, in order to manage the SCTP associations and the traffic between the SG and ASPs. As well, the active/inactive state of remote ASP(s) are also maintained. The Active ASP(s) are the one(s) currently receiving traffic from the SG. The M2UA layer MAY be instructed by local management to establish an SCTP association to a peer M2UA node. This can be achieved using the M-SCTP_ESTABLISH primitive to request, indicate and confirm the establishment of an SCTP association with a peer M2UA node. The M2UA layer MAY also need to inform local management of the status of the underlying SCTP associations using the M-SCTP_STATUS request and indication primitive. For example, the M2UA MAY inform local management of the reason for the release of an SCTP association, determined either locally within the M2UA layer or by a primitive from the SCTP. Also the M2UA layer may need to inform the local management of the change in status of an ASP or AS. This may be achieved using the M-ASP STATUS request or M-AS_STATUS request primitives. 1.3.3 Signaling Network Architecture A Signaling Gateway will support the transport of MTP2-User signaling traffic received from the SS7 network to one or more distributed ASPs (e.g., MGCs). Clearly, the M2UA protocol description cannot in itself meet any performance and reliability requirements for such transport. A physical network architecture is required, with data on the availability and transfer performance of the physical nodes involved in any particular exchange of information. However, the M2UA protocol MUST be flexible enough allow its operation and management in a variety of physical configurations that will enable Network Operators to meet their performance and reliability requirements. To meet the stringent SS7 signaling reliability and performance requirements for carrier grade networks, these Network Operators SHOULD ensure that there is no single point of failure provisioned in the end- to-end network architecture between an SS7 node and an IP ASP. Depending of course on the reliability of the SG and ASP functional elements, this can typically be met by the spreading links in a linkset across SGs, the provision of redundant QoS-bounded IP network paths for SCTP Associations between SCTP End Points, and redundant Hosts. The distribution of ASPs within the available Hosts is also important. For a particular Application Server, the related ASPs SHOULD be distributed over at least two Hosts. An example logical network architecture relevant to carrier-grade operation in the IP network domain is shown in Figure 2 below: Morneault, et al [Page 5] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 ******** ************** * *_________________________________________* ******** * Host1 * * _________* * ASP1 * * * SG1 * SCTP Associations | * ******** * * *_______________________ | * * ******** | | ************** | | ******** | | * *_______________________________| * * | * SG2 * SCTP Associations | * *____________ | * * | | ******** | | ************** | |_________________* ******** * Host2 |____________________________* * ASP2 * * * ******** * * * ************** . . . Figure 2 - Logical Model Example For carrier grade networks, Operators SHOULD ensure that under failure or isolation of a particular ASP, stable calls or transactions are not lost. This implies that ASPs need, in some cases, to share the call/- transaction state or be able to pass the call/transaction state between each other. Also, in the case of ASPs performing call processing, coordination MAY be required with the related Media Gateway to transfer the MGC control for a particular trunk termination. However, this sharing or communication is outside the scope of this document. 1.3.4 ASP Fail-over Model and Terminology The M2UA layer supports ASP fail-over functions in order to support a high availability of call and transaction processing capability. All MTP2-User messages incoming to a SG from the SS7 network are assigned to the unique Application Server, based on the Interface Identifier of the message. The M2UA layer supports a n+k redundancy model (active-standby, loadsharing, broadcast) where n ASP 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. Morneault, et al [Page 6] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 To avoid a single point of failure, it is recommended that a minimum of two ASPs be configured in an AS list, resident in separate hosts and, therefore, available over different SCTP associations. For example, in the network shown in Figure 2, all messages for the Interface Identifiers could be sent to ASP1 in Host1 or ASP2 in Host2. The AS list at SG1 might look like the following: Interface Identiers - Application Server #1 ASP1/Host1 - State = Active ASP2/Host2 - State = Inactive In this 1+1 redundancy case, ASP1 in Host1 would be sent any incoming message for the Interface Identifiers registered. ASP2 in Host2 would normally be brought to the active state upon failure of ASP1/Host1. In this example, both ASPs are Inactive or Active, meaning that the related SCTP association and far-end M2UA peer is ready. The two ASPs MAY share state information via shared memory, or MAY use an ASP to ASP protocol to pass state information. The ASP to ASP protocol is outside the scope of this document. 1.3.5 Client/Server Model It is recommended that the SG and ASP be able to support both client and server operation. The peer endpoints using M2UA SHOULD be configured so that one always takes on the role of client and the other the role of server for initiating SCTP associations. The default orientation would be for the SG to take on the role of server while the ASP is the client. In this case, ASPs SHOULD initiate the SCTP association to the SG. The SCTP (and UDP/TCP) Registered User Port Number Assignment for M2UA is 2904. 1.4 Services Provided by the M2UA Adaptation Layer The SS7 MTP3/MTP2(MTP2-User) interface is retained at the termination point in the IP network, so that the M2UA protocol layer is required to provide the equivalent set of services to its users as provided by the MTP Level 2 to MTP Level 3. 1.4.1 Support for MTP Level 2 / MTP Level 3 interface boundary M2UA supports a MTP Level 2 / MTP Level 3 interface boundary that enables a seamless, or as seamless as possible, operation of the MTP2-User peers in the SS7 and IP domains. An example of the primitives that need to be supported can be found in [7]. Morneault, et al [Page 7] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 1.4.2 Support for communication between Layer Management modules on SG and MGC The M2UA layer needs to provide some messages that will facilitate communication between Layer Management modules on the SG and MGC. To facilitate reporting of errors that arise because of backhauling MTP Level 3 scenario, the following primitive is defined: M-ERROR The M-ERROR message is used to indicate an error with a received M2UA message (e.g., an interface identifier value is not known to the SG). 1.4.3 Support for management of active associations between SG and MGC As discussed in Section 1.3.2, the M2UA layer on the SG keeps the state of the configured ASPs. A set of primitives between M2UA layer and the Layer Management are defined below to help the Layer Management manage the association(s) between the SG and the MGC. The M2UA layer can be instructed by the Layer Management to establish a SCTP association to a peer M2UA node. This procedure can be achieved using the M-SCTP ESTABLISH primitive. M-SCTP_ESTABLISH The M-SCTP_ESTABLISH primitive is used to request, indicate and confirm the establishment of a SCTP association to a peer M2UA node. M-SCTP_RELEASE The M-SCTP_RELEASE primitives are used to request, indicate, and confirm the release of a SCTP association to a peer M2UA node. The M2UA layer MAY also need to inform the status of the SCTP association(s) to the Layer Management. This can be achieved using the following primitive. Morneault, et al [Page 8] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 M-SCTP_STATUS The M-SCTP_STATUS primitive is used to request and indicate the status of underlying SCTP association(s). The Layer Management MAY need to inform the M2UA layer of an AS/ASP status (i.e., failure, active, etc.), so that messages can be exchanged between M2UA layer peers to stop traffic to the local M2UA user. This can be achieved using the following primitive. M-ASP_STATUS The ASP status is stored inside M2UA layer on both the SG and MGC sides. The M-ASP_STATUS primitive can be used by Layer Management to request the status of the Application Server Process from the M2UA layer. This primitive can also be used to indicate the status of the Application Server Process. M-ASP_MODIFY The M-ASP_MODIFY primitive can be used by Layer Management to modify the status of the Application Server Process. In other words, the Layer Management on the ASP side uses this primitive to initiate the ASPM procedures. M-AS_STATUS The M-AS_STATUS primitive can be used by Layer Management to request the status of the Application Server. This primitive can also be used to indicate the status of the Application Server. 1.5 Functions Provided by the M2UA Layer 1.5.1 Mapping The M2UA layer MUST maintain a map of a Interface ID to a physical interface on the Signaling Gateway. A physical interface would be a V.35 line, T1 line/timeslot, E1 line/timeslot, etc. The M2UA layer MUST also maintain a map of Interface Identifier to SCTP association and to the related stream within the association. The SG maps an Interface Identifier to an SCTP association/stream only when an ASP sends an ASP Active message for a particular Interface Identifier. It MUST be noted, however, that this mapping is dynamic and could change at any time due to a change of ASP state. This mapping could even temporarily be invalid, for example during failover of one ASP to another. Therefore, the SG MUST maintain the states of AS/ASP and reference them during the routing of an messages to an AS/ASP. An example of the logical view of relationship between SS7 link, Interface Identifier, AS and ASP in the SG is shown below: /-------------------------------------------------+ / /----------------------------------------------|--+ / / v | / / +----+ act+-----+ +-------+ -+--+|-+- SS7 link1-------->|IID |-+ +-->| ASP |-->| Assoc | v / +----+ | +----+ | +-----+ +-------+ -+--+--+- / +->| AS |--+ Streams / +----+ | +----+ stb+-----+ SS7 link2-------->|IID |-+ | ASP | +----+ +-----+ where IID = Interface Identifier A SG can support more than one AS. An AS can support more than one Interface Identifier. 1.5.2 Status of ASPs The M2UA layer on the SG MUST maintain the state of the ASPs it is supporting. The state of an ASP changes because of reception of peer-to-peer messages (ASPM messages as described in Section 3.3.2) or reception of indications from the local SCTP association. ASP state transition procedures are described in Section 4.3.1. At a SG, an Application Server list MAY contain active and inactive ASPs to support ASP fail-over procedures. When, for example, both a primary and a back-up ASP are available, M2UA peer protocol is required to control which ASP is currently active. The ordered list of ASPs within a logical Application Server is kept updated in the SG to reflect the active Application Server Process. Also the M2UA layer MAY need to inform the local management of the change in status of an ASP or AS. This can be achieved using the M-ASP STATUS or M-AS_STATUS primitives. 1.5.3 SCTP Specifics 1.5.3.1 SCTP Stream Management SCTP allows a user specified number of streams to be opened during initialization of the association. It is the responsibility of the M2UA layer to ensure proper management of these streams. Because of the unidirectional nature of streams, a M2UA layer is not aware of the stream information from its peer M2UA layer. Instead, the Interface Identifier is in the M2UA message header. The use of SCTP streams within M2UA is recommended in order to minimize transmission and buffering delay, therefore improving the overall performance and reliability of the signaling elements. A separate SCTP stream can be used for each SS7 link. Or, an implementation may choose to split the SS7 link across several streams based on SLS. This method may be of particular interest for high speed links (MTP3b) since high speed links have a 24-bit sequence number and the stream sequence number is 16-bits. SCTP Stream '0' SHOULD not be used for MTP2 User Adaptation (MAUP) messages (see Section 3) since stream '0' SHOULD onlt be used for ASP Management (ASPM) messages (see Section 4.3.3). 1.5.4 Seamless SS7 Network Management Interworking The M2UA layer on the SG SHOULD pass an indication of unavailability of the M2UA-User (MTP3) to the local Layer Management, if the currently active ASP moves from the ACTIVE state. The actions taken by M2UA on the SG with regards to MTP Level 2 should be in accordance with the appropriate MTP specifications. 1.5.5 Flow Control / Congestion It is possible for the M2UA layer to be informed of IP network congestion onset and abatement by means of an implementation-dependent function (i.e. an indication from the SCTP). The handling of this congestion indication by M2UA is implementation dependent. 1.5.6 Audit of Link State After a failover of one ASP to another ASP, it may be necessary for the M2UA on the ASP to audit the current SS7 link state to ensure consistency. The M2UA on the SG would respond to the audit request with information regarding the current state of the link (i.e. in-service, out-of-service, congestion state, LPO/RPO state). Morneault, et al [Page 9] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 1.6 Definition of the M2UA Boundaries 1.6.1 Definition of the M2UA / MTP Level 3 boundary DATA ESTABLISH RELEASE STATE DATA RETRIEVAL DATA RETRIEVAL COMPLETE 1.6.2 Definition of the M2UA / MTP Level 2 boundary DATA ESTABLISH RELEASE STATE DATA RETRIEVAL DATA RETRIEVAL COMPLETE 1.6.3 Definition of the Lower Layer Boundary between M2UA and SCTP The upper layer and layer management primitives provided by SCTP are provided in Reference [5] Section 9. 1.6.4 Definition of Layer Management / M2UA Boundary M-SCTP_ESTABLISH request Direction: LM -> M2UA Purpose: LM requests ASP to establish an SCTP association with an SG. M-SCTP_ESTABLISH confirm Direction: M2UA -> LM Purpose: ASP confirms to LM that it has established an SCTP association with an SG. M-SCTP_ESTABLISH indication Direction: M2UA -> LM Purpose: SG informs LM that an ASP has established an SCTP association. M-SCTP_RELEASE request Direction: LM -> M2UA Purpose: LM requests ASP to release an SCTP association with SG. M-SCTP_RELEASE confirm Direction: M2UA -> LM Purpose: ASP confirms to LM that it has released SCTP association with SG. M-SCTP_RELEASE indication Direction: M2UA -> LM Purpose: SG or IPSP informs LM that ASP has released an SCTP association. M-SCTP_RESTART indication Direction: M2UA -> LM Purpose: SG or IPSP informs LM that a SCTP Restart indication has been received M-SCTP_STATUS request Direction: LM -> M2UA Purpose: LM requests M2UA to report status of SCTP association. M-SCTP_STATUS indication Direction: M2UA -> LM Purpose: M2UA reports status of SCTP association. M-ASP_STATUS request Direction: LM -> M2UA Purpose: LM requests SG to report status of remote ASP. M-ASP_STATUS indication Direction: M2UA -> LM Purpose: SG reports status of remote ASP. M-AS_STATUS request Direction: LM -> M2UA Purpose: LM requests SG to report status of AS. M-AS_STATUS indication Direction: M2UA -> LM Purpose: SG reports status of AS. M-NOTIFY indication Direction: M2UA -> LM Purpose: ASP reports that it has received a NOTIFY message from its peer. M-ERROR indication Direction: M2UA -> LM Purpose: ASP or SG reports that it has received an ERROR message from its peer. M-ASP_UP request Direction: LM -> M2UA Purpose: LM requests ASP to start its operation and send an ASP UP message to the SG. M-ASP_UP confirm Direction: M2UA -> LM Purpose: ASP reports that it has received an ASP UP Acknowledgement message from the SG. M-ASP_DOWN request Direction: LM -> M2UA Purpose: LM requests ASP to stop its operation and send an ASP DOWN message to the SG. M-ASP_DOWN confirm Direction: M2UA -> LM Purpose: ASP reports that is has received an ASP DOWN Acknowledgement message from the SG. M-ASP_ACTIVE request Direction: LM -> M2UA Purpose: LM requests ASP to send an ASP ACTIVE message to the SG. M-ASP_ACTIVE confirm Direction: M2UA -> LM Purpose: ASP reports that is has received an ASP ACTIVE Acknowledgement message from the SG. M-ASP_INACTIVE request Direction: LM -> M2UA Purpose: LM requests ASP to send an ASP INACTIVE message to the SG. M-ASP_INACTIVE confirm Direction: M2UA -> LM Purpose: ASP reports that is has received an ASP INACTIVE Acknowledgement message from the SG. 2.0 Conventions The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in [RFC2119]. 3.0 Protocol Elements This section describes the format of various messages used in this protocol. Morneault, et al [Page 10] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 3.1 Common Message Header The protocol messages for MTP2-User Adaptation require a message structure which contains a version, message class, 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Version | Spare | Message Class | Message Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3 Common Message Header All fields in an M2UA message MUST be transmitted in the network byte order, unless otherwise stated. 3.1.1 Version The version field (vers) contains the version of the M2UA adapation layer. The supported versions are: Value Version ----- ------- 1 Release 1.0 3.1.2 Message Type The following List contains the valid Message Classes: Message Class: 8 bits (unsigned integer) 0 Management (MGMT) Message [IUA/M2UA/M2UA/SUA] 1 Transfer Messages [M2UA] 2 SS7 Signalling Network Management (SSNM) Messages [M2UA/SUA] 3 ASP State Maintenance (ASPSM) Messages [IUA/M2UA/M2UA/SUA] 4 ASP Traffic Maintenance (ASPTM) Messages [IUA/M2UA/M2UA/SUA] 5 Q.921/Q.931 Boundary Primitives Tranport (QPTM) Messages [IUA] 6 MTP2 User Adaptatation (MAUP) Messages [M2UA] 7 Connectionless Messages [SUA] 8 Connection-Oriented Messages [SUA] 9 Routing Key Management (RKM) Messages (M2UA) 10 Interface Identifier Management (IIM) Messages (M2UA) 11 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined Message Class extensions The following list contains the message types for the defined messages. MTP2 User Adaptatation (MAUP) Messages 0 Reserved 1 Data 2 Establish Request 3 Establish Confirm 4 Release Request 5 Release Confirm 6 Release Indication 7 State Request 8 State Confirm 9 State Indication 10 Data Retrieval Request 11 Data Retrieval Confirm 12 Data Retrieval Indication 13 Data Retrieval Complete Indication 14 Congestion Indication 15 Data Acknowledge 16 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined MAUP extensions Morneault, et al [Page 11] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 Application Server Process State Maintenance (ASPSM) messages 0 Reserved 1 ASP Up (UP) 2 ASP Down (DOWN) 3 Reserved 4 ASP Up Ack (UP ACK) 5 ASP Down Ack (DOWN ACK) 6 Reserved 7 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined ASPSM extensions Application Server Process Traffic Maintenance (ASPTM) messages 0 Reserved 1 ASP Active (ACTIVE) 2 ASP Inactive (INACTIVE) 3 ASP Active Ack (ACTIVE ACK) 4 ASP Inactive Ack (INACTIVE ACK) 5 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined ASPTM extensions Management (MGMT) Messages 0 Error (ERR) 1 Notify (NTFY) 2 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined MGMT extensions Interface Identifier Management (IIM) Messages 0 Reserved 1 Registration Request (REG REQ) 2 Registration Response (REG RSP) 3 Deregistration Request (DEREG REQ) 4 Deregistration Response (DEREG RSP) 5 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined IIM extensions 3.1.3 Reserved The Reserved field is 8-bits. It SHOULD be set to all '0's and ignored by the receiver. 3.1.4 Message Length The Message Length defines the length of the message in octets, including the header. The Message Length includes parameter padding bytes, if any. 3.1.5 Variable-Length Parameter Format M2UA messages consist of a Common Header followed by zero or more variable-length parameters, as defined by the message type. The variable-length parameters contained in a message are defined in a Tag-Length-Value format as shown below. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Parameter Tag | Parameter Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / Parameter Value / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Mandatory paramters MUST be placed before optional parameters in a message. Parameter Tag: 16 bits (unsigned integer) The Type field is a 16 bit identifier of the type of parameter. It takes a value of 0 to 65534. The common parameter Tags (used by all User Adaptation layers) defined are as follows: Parameter Value Parameter Name --------------- -------------- 0 (0x0) Reserved 1 (0x1) Interface Identifier (Integer) 2 (0x2) Interface Identifier (Integer Range) 3 (0x3) Interface Identifier (Text) 4 (0x4) Info String 5 (0x5) Unused 6 (0x6) Unused 7 (0x7) Diagnostic Information 8 (0x8) Unused 9 (0x9) Heartbeat Data 10 (0xa) Reason 11 (0xb) Traffic Mode Type 12 (0xc) Error Code 13 (0xd) Status Type/Information 14 (0xe) ASP Identifier The M2UA specific parameter Tags defined are as follows: Parameter Value Parameter Name --------------- -------------- 768 (0x0300) Protocol Data 1 769 (0x0301) Protocol Data 2 (TTC) 770 (0x0302) State Request 771 (0x0303) State Event 772 (0x0304) Congestion Status 773 (0x0305) Discard Status 774 (0x0306) Action 775 (0x0307) Sequence Number 776 (0x0309) Retrieval Result 777 (0x030a) Link Key 778 (0x030b) Local-LK-Identifier 779 (0x030c) Signaling Data Terminal (SDT) Identifier 780 (0x030d) Signailng Data Link (SDL) Identifier 781 (0x030e) Registration Result 782 (0x030f) Registration Status 783 (0x0310) De-Registration Result 784 (0x0311) De-Registration Status 785 (0x0312) Correlation Id 786 (0x0313) Correlation Id Ack Parameter Length: 16 bits (unsigned integer) The Parameter Length field contains the size of the parameter in bytes, including the Parameter Tag, Parameter Length, and Parameter Value fields. The Parameter Length does not include any padding bytes. Parameter Value: variable-length. The Parameter Value field contains the actual information to be transferred in the parameter. The total length of a parameter (including Tag, Parameter Length and Value fields) MUST be a multiple of 4 bytes. If the length of the parameter is not a multiple of 4 bytes, the sender pads the Parameter at the end (i.e., after the Parameter Value field) with all zero bytes. The length of the padding is NOT included in the parameter length field. A sender SHOULD NOT pad with more than 3 bytes. The receiver MUST ignore the padding bytes. 3.2 M2UA Message Header In addition to the common message header, there will be a M2UA specific message header. The M2UA specific message header will immediately follow the common message header, but will only be used with MAUP messages. This message header will contain the Interface Identifier. The Interface Identifier identifies the physical interface at the SG for which the signaling messages are sent/received. The format of the Interface Identifier parameter can be text or integer, the values of which are assigned according to network operator policy. The values used are of local significance only, coordinated between the SG and ASP. The integer formatted Interface Identifier MUST be supported. The text formatted Interface Identifier MAY optionally be supported. 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 (0x1) | Length=8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier (integer) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4 M2UA Message Header (Integer-based Interface Identifier) The Tag value for Integer-based Interface Identifier is 0x1. The length is always set to a value of 8. 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 (0x3) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier (text) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5 M2UA Message Header (Text-based Interface Identifier) The Tag value for the Text-based Interface Identifier is 0x3. The length is variable. 3.3 M2UA Messages The following section defines the messages and parameter contents. The M2UA messages will use the common message header (Figure 3) and the M2UA message header (Figure 4). 3.3.1 MTP2 User Adaptation Messages 3.3.1.1 Data The Data message contains an SS7 MTP2-User Protocol Data Unit (PDU). The Data message contains the following parameter: Protocol Data (mandatory) Correlation ID (optional) Morneault, et al [Page 12] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 The format for the Data 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 (0x312) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Correlation Id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x300) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / \ \ Protocol Data / / \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Protocol Data field contains the MTP2-User application message in network byte order starting with the Signaling Information Octet (SIO). The Correlation Id parameter uniquely identifies the MSU carried in the Protocol Data within a Routing Context. This Correlation Id parameter is assigned by the sending M3UA. The format for a Data Message with TTC PDU 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 (0x312) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Correlation Id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x301) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / \ \ Protocol Data / / \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Protocol Data field contains the MTP2-User application message in network byte order starting with the Length Indicator (LI) octet. The Japanese TTC variant uses the spare bits of the LI octet for priority. 3.3.3 Data Acknowledge Message The Data Acknowlege message contains the Correlation Id of the Data message which the sending M2UA is acknowledging as successfully processed to the peer M2UA. The Data Acknowlege message contains the following parameter: Correlation Id Ack Mandatory The following format MUST be used for the Data Ack Message: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x313 | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Correlation Id Ack | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Correlation Id Ack parameter acknowledges to the perr the receipt and processing of the MSU to which the Correlation Id Ack parameter corresponds. 3.3.1.2 Establish (Request, Confirmation) The Establish Request message is used to establish the link or to indicate that the channel has been established. The MGC controls the state of the SS7 link. When the MGC desires the SS7 link to be in-service, it will send the Establish Request message. Note that the gateway MAY already have the SS7 link established at its layer. If so, upon receipt of an Establish Request, the gateway takes no action except to send an Establish Confirm. When the MGC sends an M2UA Establish Request message, the MGC MAY start a timer. This timer would be stopped upon receipt of an M2UA Establish Confirm. If the timer expires, the MGC would re-send the M2UA Establish Request message and restart the timer. In other words, the MGC MAY continue to request the establishment of the data link on periodic basis until the desired state is achieved or take some other action (notify the Management Layer). The mode (Normal or Emergency) for bringing the link in service is defaulted to Normal. The State Request (described in Section 3.3.1.4 below) can be used to change the mode to Emergency. 3.3.1.3 Release (Request, Indication, Confirmation) This Release Request message is used to release the channel. The Release Confirm and Indication messages are used to indicate that the channel has been released. 3.3.1.4 State Request The State Request message can be sent from a MGC to cause an action on a particular SS7 link supported by the Signaling Gateway. The gateway sends a State Confirm to the MGC if the action has been success- fully completed. The State Confirm reflects that state value received in the State Request message. Morneault, et al [Page 13] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 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 (0x302) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | State | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The valid values for State are shown in the following table. Define Value Description STATUS_LPO_SET 0x0 Request local processor outage STATUS_LPO_CLEAR 0x1 Request local processor outage recovered STATUS_EMER_SET 0x2 Request emergency alignment procedure STATUS_EMER_CLEAR 0x3 Request normal alignment (cancel emergency) procedure STATUS_FLUSH_BUFFERS 0x4 Flush or clear receive, transmit and retransmit queues STATUS_CONTINUE 0x5 Continue or Resume STATUS_CLEAR_RTB 0x6 Clear the retransmit queue STATUS_AUDIT 0x7 Audit state of link STATUS_CONG_CLEAR 0x8 Congestion cleared STATUS_CONG_ACCEPT 0x9 Congestion accept STATUS_CONG_DISCARD 0xa Congestion discard 3.3.1.5 State Confirm The State Confirm message will be sent by the SG in response to a State Request from the MGC. The State Confirm reflects that state value received in the State Request message. Morneault, et al [Page 13] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 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 (0x302) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | State | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The valid values for State are shown in the following table. The value of the State field should reflect the value received in the State Request message. Define Value Description STATUS_LPO_SET 0x0 Request local processor outage STATUS_LPO_CLEAR 0x1 Request local processor outage recovered STATUS_EMER_SET 0x2 Request emergency alignment procedure STATUS_EMER_CLEAR 0x3 Request normal alignment (cancel emergency) procedure STATUS_FLUSH_BUFFERS 0x4 Flush or clear receive, transmit and retransmit queues STATUS_CONTINUE 0x5 Continue or Resume STATUS_CLEAR_RTB 0x6 Clear the retransmit queue STATUS_AUDIT 0x7 Audit state of link STATUS_CONG_CLEAR 0x8 Congestion cleared STATUS_CONG_ACCEPT 0x9 Congestion accept STATUS_CONG_DISCARD 0xa Congestion discard 3.3.1.6 State Indication The MTP2 State Indication message can be sent from a gateway to an ASP to indicate a condition on a link. 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 (0x303) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Event | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The valid values for Event are shown in the following table. Define Value Description EVENT_RPO_ENTER 0x1 Remote entered processor outage EVENT_RPO_EXIT 0x2 Remote exited processor outage EVENT_LPO_ENTER 0x3 Link entered processor outage EVENT_LPO_EXIT 0x4 Link exited processor outage 3.3.1.7 Congestion Indication The Congestion Indication message can be sent from a Signaling Gateway to an ASP to indicate the congestion status and discard status of a link. When the MSU buffer fill increases above an Onset threshold or decreases below an Abatement threshold or crosses a Discard threshold in either direction, the SG SHALL send a congestion indication message. The SG shall send the message only when there is actually a change in either the discard level or the congestion level to report, meaning it is different from the previously sent message. In addition, the SG SHALL use an implementation dependent algorithm to limit the frequency of congestion indication messages. An implementation may optionally send Congestion Indication messages on a "high priority" stream in order to potentially reduce delay (Refer to [12] for more details). The Congestion Indication message contains the following parameters: Congestion Status (mandatory) Discard Status (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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x304) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Congestion Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x305) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Discard Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The valid values for Congestion Status and Discard Status are shown in the following table. Define Value Description LEVEL_NONE 0x0 No congestion. LEVEL_1 0x1 Congestion Level 1 LEVEL_2 0x2 Congestion Level 2 LEVEL_3 0x3 Congestion Level 3 LEVEL_4 0x4 Congestion Level 4 - Discarding For networks that do not support multiple levels of congestion, only the LEVEL_NONE and LEVEL_3 values will be used. For networks that support multiple levels of congestion, it is possible for all values to be used. Refer to [2] and [9] for more details. When the SG runs out of buffer space for MSUs received from the MGC, the SG MAY send a Congestion Indication message with Congestion Status and Discard Status set to LEVEL_4 and discard MSUs received from the MGC. 3.3.1.8 Retrieval Request The MTP2 Retrieval Request message is used during the MTP Level 3 changeover procedure to request the BSN, to retrieve PDUs from the transmit and retransmit queues or to flush PDUs from the retransmit queue. The Retrieval Request message contains the following parameters: Action (mandatory) Sequence Number (optional) Morneault, et al [Page 14] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 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 (0x306) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Action | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x307) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The valid values for Action are shown in the following table. Define Value Description ACTION_RTRV_BSN 0x1 Retrieve the backward sequence number ACTION_RTRV_MSGS 0x2 Retrieve the PDUs from the transmit and retransmit queues In the Retrieval Request message, the Sequence Number field SHOULD NOT be present if the Action field is ACTION_RTRV_BSN, ACTION_DROP_MSGS or ACTION_RTRV_TRANS. The Sequence Number field contains the Forward Sequnce Number (FSN) of the far end if the Action is ACTION_RTRV_MSGS. 3.3.1.9 Retrieval Confirm The MTP2 Retrieval Confirm message is sent by the Signaling Gateway in response to a Retrieval Request message. The Retrieval Confirm message contains the following parameters: Action (mandatory) Result (mandatory) Sequence Number (optional) Morneault, et al [Page 14] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 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 (0x306) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Action | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x308) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Result | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x307) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The valid values for Action are the same as in Retrieval Request. The values for Result are shown below: in the following table. Define Value Description RESULT_SUCCESS 0x0 Action successful RESULT_FAILURE 0x1 Action failed When the Signaling Gateway sends a Retrieval Confirm to a Retrieval Request, it echos the Action field. If the Action was ACTION_RTRV_BSN and the SG successfully retrieved the BSN, the SG will put the Backward Sequence Number (BSN) in the Sequence Number field and will indicate a success in the Result field. If the BSN could not be retrieved, the Sequence Number field will not be included and the Result field will indicate failure. For a Retrieval Confirm with Action of ACTION_RTRV_MSGS and ACTION_RTRV_TRANS, the value of of Result field will indicate success or failure. A failure means that the buffers could not be retrieved. The Sequence Number field is not used with ACTION_RTRV_MSGS. For a Retrieval Confirm with an Action of ACTION_DROP_MSGS, the Result value will indicate success or failure. The Sequence Number field is not used with ACTION_DROP_MSGS. 3.3.1.10 Retrieval Indication The Retrieval Indication message is sent by the Signaling Gateway with a PDU from the transmit or retransmit queue. The Retrieval Indication message does not contain the Action or seq_num fields, just a MTP3 Protocol Data Unit (PDU) from the transmit or retransmit queue. 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 (0x300) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PDU | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ For TTC Data messages, the following parameter will be used to indicate a TTC PDU which starts at LI. 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 (0x301) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TTC PDU | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The M2UA implementation MAY consider the use of the bundling feature of SCTP for Retrieval Indication messages. 3.3.1.11 Retrieval Complete Indication The MTP2 Retrieval Complete Indication message is exactly the same as the MTP2 Retrieval Indication message except that it also indicates that it contains the last PDU from the transmit or retransmit queue. 3.3.2 Application Server Process Maintenance (ASPM) Messages The ASPM messages will only use the common message header. 3.3.2.1 ASP Up (ASPUP) The ASP Up (ASPUP) message is used to indicate to a remote M2UA peer that the Adaptation layer is ready to receive traffic or maintenance messages. Morneault, et al [Page 15] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 The ASPUP message contains the following parameters ASP 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 (0xe) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ASP Identifier* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The optional ASP Identifier parameter would contain a unique value that is locally significant among the ASPs that support an AS. The SG should save the ASP Identifier to be used, if necessary, with the Notify message (see Section 3.3.3.2). The optional 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 for debugging purposes. Morneault, et al [Page 16] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 3.3.2.2 ASP Up Ack The ASP Up Ack message is used to acknowledge an ASP Up message received from a remote M2UA peer. The ASPUP Ack message contains the following parameters: INFO String (optional) The format for ASPUP Ack 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 (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format and description of the optional Info String parameter is the same as for the ASP UP message (See Section 3.3.2.1). 3.3.2.3 ASP Down (ASPDN) The ASP Down (ASPDN) message is used to indicate to a remote M2UA 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0xa) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reason | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format and description of the optional Info String parameter is the same as for the ASP Up message (See Section 3.3.2.1). The Reason parameter indicates the reason that the remote M2UA adaptation layer is unavailable. The valid values for Reason are shown in the following table: Value Description 0x1 Management 3.3.2.4 ASP Down Ack The ASP Down Ack message is used to acknowledge an ASP Down message received from a remote M2UA peer. The ASP Down Ack message contains the following parameters: Reason INFO String (optional) The format for the ASPDN Ack 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 (0xa) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reason | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format and description of the optional Info String parameter is the same as for the ASP UP message (See Section 3.3.2.1). The format of the Reason parameter is the same as for the ASP Down message (See Section 3.3.2.3). 3.3.2.5 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 Traffic Mode Type (mandatory) Interface Identifier (optional) - Combination of integer and integer ranges, OR - string (text formatted) INFO String (optional) The format for the ASPAC message using integer formatted Interface Identifiers 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 (0xb) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Traffic Mode Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x1=integer) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifiers* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x8=integer range) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier StartN* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier StopN* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Interface Identifiers | | of Tag Type 0x1 or 0x8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format for the ASPAC message using text formatted (string) Interface Identifiers 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 (0xb) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Traffic Mode Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x3=string) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Interface Identifiers | | of Tag Type 0x3 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Traffic Mode Type parameter identifies the traffic mode of operation of the ASP within an AS. The valid values for Type are shown in the following table: Value Description 0x1 Over-ride 0x2 Load-share 0x3 Broadcast Within a particular AS, only one Traffic Mode Type can be used. The Over-ride value indicates that the ASP is operating in Over-ride mode, where the ASP takes over all traffic in an Application Server (i.e., primary/back-up operation), over-riding any currently active ASPs in the AS. In Load-share mode, the ASP will share in the traffic distribution with any other currently active ASPs. In Broadcast mode, all of the Active ASPs receive all message traffic in the Application Server. Morneault, et al [Page 17] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 The optional Interface Identifiers parameter contains a list of Interface Identifier integers (Type 0x1 or Type 0x8) or text strings (Type 0x3)indexing the Application Server traffic that the sending ASP is configured/registered to receive. If integer formatted Interface Identifiers are being used, the ASP can also send ranges of Interface Identifiers (Type 0x8). Interface Identifier types Integer (0x1) and Integer Range (0x8) are allowed in the same message. Text formatted Interface Identifiers (0x3) cannot be used with either Integer (0x1) or Integer Range (0x8) types. If no Interface Identifiers are included, the message is for all provisioned Interface Identifiers within the AS(s) in which the ASP is provisioned. If only a subset of Interface Identifiers are included, the ASP is noted as Active for all the Interface Identifiers provisioned for that AS. Note: If the optional Interface Identifier parameter is present, the integer formatted Interface Identifier MUST be supported, while the text formatted Interface Identifier MAY be supported. An SG that receives an ASPAC with an incorrect or unsupported Traffic Mode Type for a particular Interface Identifier will respond with an Error Message (Cause: Unsupported Traffic Handling Mode). The format and description of the optional Info String parameter is the same as for the ASP UP message (See Section 3.3.2.1). 3.3.2.6 ASP Active Ack The ASP Active (ASPAC) Ack message is used to acknowledge an ASP Active message received from a remote M2UA peer. The ASPAC Ack message contains the following parameters: Traffic Mode Type (mandatory) Interface Identifier (optional) - Combination of integer and integer ranges, OR - string (text formatted) INFO String (optional) The format for the ASPAC Ack message with Integer-formatted Interface Identifiers 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 (0xb) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Traffic Mode Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x1=integer) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifiers* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x8=integer range) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier StartN* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier StopN* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Interface Identifiers | | of Tag Type 0x1 or 0x8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format for the ASP Active Ack message using text formatted (string) Interface Identifiers 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 (0xb) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Traffic Mode Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x3=string) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Interface Identifiers | | of Tag Type 0x3 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format and description of the optional Info String parameter is the same as for the ASP UP message (See Section 3.3.2.1.) The format of the Type and Interface Identifier parameters is the same as for the ASP Active message (See Section 3.3.2.5). 3.3.2.7 ASP Inactive (ASPIA) The ASP Inactive (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 Ack message and either discard incoming messages or buffer for a timed period and then discard. The ASPIA message contains the following parameters: Interface Identifiers (optional) - Combination of integer and integer ranges, OR - string (text formatted) INFO String (optional) The format for the ASP Inactive message parameters using Integer formatted Interface Identifiers 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 (0x1=integer) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifiers* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x8=integer range) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier StartN* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier StopN* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Interface Identifiers | | of Tag Type 0x1 or 0x8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format for the ASP Inactive message using text formatted (string) Interface Identifiers 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 (0x3=string) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Interface Identifiers | | of Tag Type 0x3 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format and description of the optional Interface Identifiers and Info String parameters is the same as for the ASP Active message (See Section 3.3.2.3). The optional Interface Identifiers parameter contains a list of Interface Identifier integers indexing the Application Server traffic that the sending ASP is configured/registered to receive, but does not want to receive at this time. 3.3.2.8 ASP Inactive Ack The ASP Inactive (ASPIA) Ack message is used to acknowledge an ASP Inactive message received from a remote M2UA peer. The ASPIA Ack message contains the following parameters: Interface Identifiers (optional) - Combination of integer and integer ranges, OR - string (text formatted) INFO String (optional) The format for the ASPIA Ack 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 (0x1=integer) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifiers* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x8=integer range) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier StartN* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier StopN* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Interface Identifiers | | of Tag Type 0x1 or 0x8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format for the ASP Inactive Ack message using text formatted (string) Interface Identifiers 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 (0x3=string) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Interface Identifiers | | of Tag Type 0x3 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format of the Interface Identifier parameter is the same as for the ASP Inactive message (See Section 3.3.2.7). The format and description of the optional Info String parameter is the same as for the ASP Up message (See Section 3.3.2.1). 3.3.3 Layer Management (MGMT) Messages 3.3.3.1 Error (ERR) The Error (ERR) message is used to notify a peer of an error event associated with an incoming message. For example, the message type might be unexpected given the current state, or a parameter value might be invalid. The ERR message contains the following parameters: Error Code (mandatory) Diagnostic Information (optional) 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0xc) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Error Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x7) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Diagnostic Information* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Error Code parameter indicates the reason for the Error Message. The Error parameter value can be one of the following values: Invalid Version 0x1 Invalid Interface Identifier 0x2 Unsupported Message Class 0x3 Unsupported Message Type 0x4 Unsupported Traffic Handling Mode 0x5 Unexpected Message 0x6 Protocol Error 0x7 Unsupported Interface Identifier Type 0x8 Invalid Stream Identifier 0x9 Invalid Parameter Value 0xa Refused - Management Blocking 0xb The "Invalid Version" error would be sent if a message was received with an invalid or unsupported version. The Error message would contain the supported version in the Common header. The Error message could optionally provide the supported version in the Diagnostic Information area. The "Invalid Interface Identifier" error would be sent by a SG if an ASP sends a message with an invalid (unconfigured) Interface Identifier value. The "Unsupported Traffic Handling Mode" error would be sent by a SG if an ASP sends an ASP Active with an unsupported Traffic Handling Mode. An example would be a case in which the SG did not support load-sharing. The "Unexpected Message" error would be sent by an ASP if it received a MAUP message from an SG while it was in the Inactive state. The "Protocol Error" error would be sent for any protocol anomaly (i.e. a bogus message). The "Invalid Stream Identifier" error would be sent if a message was received on an unexpected SCTP stream (i.e. a MGMT message was received on a stream other than "0"). The "Unsupported Interface Identifier Type" error would be sent by a SG if an ASP sends a Text formatted Interface Identifier and the SG only supports Integer formatted Interface Identifiers. When the ASP receives this error, it will need to resend its message with an Integer formatted Interface Identifier. The "Unsupported Message Class" error would be sent if a message with an unexpected or unsupported Message Class is received. The "Unsupported Interface Identifier Type" error would be sent by a SG if an ASP sends a Text formatted Interface Identifier and the SG only supports Integer formatted Interface Identifiers. When the ASP receives this error, it will need to resend its message with an Integer formatted Interface Identifier. The "Invalid Parameter Value" error is sent if a message is received with an invalid parameter value. The "Refused - Management Blocking" error is sent when an ASP Up or ASP Active message is received and the request is refused for management reasons (e.g., management lock-out"). The optional Diagnostic information can be any information germain to the error condition, to assist in identification of the error condition. In the case of an Invalid Version Error Code the Diagnostic information includes the supported Version parameter. In the other cases, the Diagnostic information MAY be the first 40 bytes of the offending message. Morneault, et al [Page 19] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 3.3.3.2 Notify (NTFY) The Notify message is used to provide an autonomous indication of M2UA events to an M2UA peer. The NTFY message contains the following parameters: Status Type (mandatory) Status Information (mandatory) ASP Identifier (optional) Interface Identifiers (optional) INFO String (optional) The format for the Notify message with Integer-formatted Interface Identifiers 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 (0xd) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Status Type | Status Information | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0xe) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ASP Identifier* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x1=integer) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifiers* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x8=integer range) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier StartN* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier StopN* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Interface Identifiers | | of Tag Type 0x1 or 0x8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The format for the Notify message with Text-formatted Interface Identifiers 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 (0xd) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Status Type | Status Information | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0xe) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ASP Identifier* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x3=string) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Additional Interface Identifiers | | of Tag Type 0x3 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Status Type parameter identifies the type of the Notify message. The following are the valid Status Type values: Value Description 0x1 Application Server state change (AS_State_Change) 0x2 Other The Status Information parameter contains more detailed information for the notification, based on the value of the Status Type. If the Status Type is AS_State_Change the following Status Information values are used: Value Description 1 Application Server Down (AS_Down) 2 Application Server Inactive (AS_Inactive) 3 Application Server Active (AS_Active) 4 Application Server Pending (AS_Pending) These notifications are sent from an SG to an ASP upon a change in status of a particular Application Server. The value reflects the new state of the Application Server. The Interface Identifiers of the AS MAY be placed in the message if desired. If the Status Type is Other, then the following Status Information values are defined: Value Description 1 Insufficient ASP resources active in AS 2 Alternate ASP Active 3 ASP Failure In the Insufficent ASP Resources case, the SG is indicating to an ASP-INACTIVE ASP(s) in the AS that another ASP is required in order to handle the load of the AS (Load-sharing mode). For the Alternate ASP Active case, the formerly Active ASP is informed when an alternate ASP transitions to the ASP Active state in Over-ride mode. The ASP ID (if available) of the Alternate ASP MUST be placed in the message. For the ASP Failure case, the SG is indicating to ASP(s) in the AS that one of the ASPs has failed (i.e. the ASP Transition to Down due to SCTP Communication Down Indication). The ASP ID (if available) of the failed ASP MUST be placed in the message. For each of the Status Information values in Status Type Other, the Interface Identifiers of the affected AS MAY be placed in the message if desired. The format and description of the optional Interface Identifiers and Info String parameters is the same as for the ASP Active message (See Section 3.3.2.3). Morneault, et al [Page 20] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 3.3.4 Interface Identifier Management (IIM) Messages The Interface Identifier Managmement messages are optional. They are used to support automatic allocation of Signaling Terminals or Signaling Data Links [2][3]. 3.3.4.1 Registration Request (REG REQ) The REG REQ message is sent by an ASP to indicate to a remote M2UA peer that it wishes to register one or more given Link Keys with the remote peer. Typically, an ASP would send this message to an SGP, and expectes to receive a REG RSP in return with an associated Interface Identifier value. The REG REQ message contains the following parameter: Link Key (mandatory) The format for the REG REQ message is as follows 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag = 0x030a | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / Link Key 1 / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / ... / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag = 0x030a | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / Link Key n / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Link Key: fixed length The Link Key parameter is mandatory. The sender of this message expects the receiver of this message will create a Link Key entry and assign a unique Interface Identifier value to it, if the Link Key entry does not yet exist. The Link Key parameter may be present multiple times in the same message. This is used to allow the registration of multiple Link Keys in a single message. The format of the Link Key parameter 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local-LK-Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Signalling Data Terminal Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Signalling Data Link Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Local-LK-Identifier: 32-bit integer The mandatory Local-LK-Identifier field is used to uniquely (between ASP and SG) identify the registration request. The Identifier value is assigned by the ASP, and is used to correlate the response in a REG RSP message with the original registration request. The Identifier value must remain unique until the REG RSP is received. The format of the Local-LK-Identifier field 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 = 0x030b | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local-LK-Identifier value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Signalling Data Terminal Identifier The Signalling Data Terminal Identifier parameter is mandatory. It identifies the Signalling Data Terminal associated with the SS7 link for which the ASP is registering. The format 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 = 0x030c | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | SDT Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The SDT Identifier is a 32-bit unsigned value which may only be significant to 12 or 14 bits depending on the SS7 variant which is supported by the MTP Level 3 at the ASP. Insignificant SDTI bits are coded 0. Signalling Data Link Identifier The Signalling Data Link Identifier parameter is mandatory. It identifies the Siganlling Data Link Identifier associated with the SS7 link for which the ASP is registering. The format 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 = 0x030d | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | SDL Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The SDL Identifier is a 32-bit unsigned value which may only be significant to 12 or 14 bits depending on the SS7 variant which is supported by the MTP Level 3 at the ASP. Insignificant SDLI bits are coded 0. 3.3.4.2 Registration Response (REG RSP) The REG RSP message is used as a response to the REG REQ message from a remote M2UA peer. It contains indications of success/failure for registration requests and returns a unique Interface Identifier value for successful registration requests, to be used in subsequent M2UA Traffic Management protocol. The REG RSP message contains the following parameter: Registration Results (mandatory) The format for the REG RSP message is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag = 0x030e | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / Registration Result 1 / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / ... / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag = 0x030e | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / Registration Result n / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Registration Results: fixed length The Registration Results parameter contains one or more results, each containing the registration status for a single Link Key in the REG REQ message. The number of results in a single REG RSP message MAY match the number of Link Key parameters found in the corresponding REG REQ message. The format of each result 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local-LK-Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Registration Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Local-LK-Identifier: 32-bit integer The Local-LK-Identifier contains the same value as found in the matching Link Key parameter found in the REG REQ message. The format of the Local-LK-Identifier is shown in Section 3.3.4.1. Registration Status: 32-bit integer The Registration Result Status field indicates the success or the reason for failure of a registration request. Its values may be one of the following: 0 Successfully Registered 1 Error - Unknown 2 Error - Invalid SDLI 3 Error - Invalid SDTI 4 Error - Invalid Link Key 5 Error - Permission Denied 6 Error - Overlapping (Non-unique) Link Key 7 Error - Link Key not Provisioned 8 Error - Insufficient Resources The format of the Registration Status field 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 = 0x030f | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Registration Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Interface Identifier: 32-bit integer The Interface Identifier field contains the Interface Identifier for the associated Link Key if the registration is successful. It is set to "0" if the registration was not successful. The format of integer-based and text-based Interface Identifier parameters are shown in Section 3.2. 3.3.4.3 De-Registration Request (DEREG REQ) The DEREG REQ message is sent by an ASP to indicate to a remote M2UA peer that it wishes to de-register a given Interface Identifier. Typically, an ASP would send this message to an SGP, and expects to receive a DEREG RSP in return reflecting the Interface Identifier and containing a de-registration status. The DEREG REQ message contains the following parameter: Interface Identifier (mandatory) The format for the DEREG REQ message is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag = 0x1 or 0x3 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / Interface Identifer 1 / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / ... / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag = 0x1 or 0x3 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / Interface Identifier n / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Interface Identifier The Interface Identifier parameter contains a Interface Identifier indexing the Application Server traffic that the sending ASP is currently registered to receive from the SG but now wishes to deregister. The format of integer-based and text-based Interface Identifier parameters are shown in Section 3.2. 3.3.4.4 De-Registration Response (DEREG RSP) The DEREG RSP message is used as a response to the DEREG REQ message from a remote M2UA peer. The DEREG RSP message contains the following parameter: De-Registration Results (mandatory) The format for the DEREG RSP message is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag = 0x0310 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / De-Registration Result 1 / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / ... / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag = 0x0310 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / De-Registration Result n / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ De-Registration Results: fixed length The De-Registration Results parameter contains one or more results, each containing the de-registration status for a single Interface Identifier in the DEREG REQ message. The number of results in a single DEREG RSP message MAY match the number of Interface Identifer parameters found in the corresponding DEREG REQ message. The format of each result 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | De-Registration Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Interface Identifier: 32-bit integer The Interface Identifier field contains the Interface Identifier value of the matching Link Key to deregister, as found in the DEREG REQ. The format of integer-based and text-based Interface Identifier parameters are shown in Section 3.2. De-Registration Status: 32-bit integer The De-Registration Result Status field indicates the success or the reason for failure of the de-registration. Its values may be one of the following: 0 Successfully De-registered 1 Error - Unknown 2 Error - Invalid Interface Identifier 3 Error - Permission Denied 4 Error - Not Registered The format of the De-Registration Status field 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 = 0x0311 | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | De-Registration Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 4.0 Procedures The M2UA layer needs to respond to various primitives it receives from other layers as well as messages it receives from the peer-to-peer messages. This section describes various procedures involved in response to these events. 4.1 Procedures to Support Service in Section 1.4.1 These procedures achieve the M2UA layer's "Transport of MTP Level 2 / MTP Level 3 boundary" service. 4.1.1 MTP Level 2 / MTP Level 3 Boundary Procedures On receiving a primitive from the local upper layer, the M2UA layer will send the corresponding MAUP message (see Section 3) to its peer. The M2UA layer MUST fill in various fields of the common and specific headers correctly. In addition the message SHOULD to be sent on the SCTP stream that corresponds to the SS7 link. 4.1.2 MAUP Message Procedures On receiving MAUP messages from a peer M2UA layer, the M2UA layer on an SG or MGC needs to invoke the corresponding layer primitives to the local MTP Level 2 or MTP Level 3 layer. Morneault, et al [Page 21] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 4.2 Procedures to Support Service in Section 1.4.2 These procedures achieve the M2UA layer's "Support for Communication between Layer Managements" service. 4.2.1 Layer Management Primitives Procedure On receiving primitives from the local Layer Management, the M2UA layer will take the requested action and provide an appropriate response primitive to Layer Management. An M-SCTP_ESTABLISH request primitive from Layer Management at an ASP or IPSP will initiate the establishment of an SCTP association. The M2UA layer will attempt to establish an SCTP association with the remote M2UA peer by sending an SCTP-ASSOCIATE primitive to the local SCTP layer. When an SCTP association has been successfully established, the SCTP will send an SCTP-COMMUNICATION_UP notification primitive to the local M2UA layer. At the SGP or IPSP that initiated the request, the M2UA layer will send an M-SCTP_ESTABLISH confirm primitive to Layer Management when the association set-up is complete. At the peer M2UA layer, an M-SCTP_ESTABLISH indication primitive is sent to Layer Management upon successful completion of an incoming SCTP association set-up. An M-SCTP_RELEASE request primitive from Layer Management initates the tear-down of an SCTP association. The M2UA layer accomplishes a graceful shutdown of the SCTP association by sending an SCTP-SHUTDOWN primitive to the SCTP layer. When the graceful shutdown of the SCTP association has been accomplished, the SCTP layer returns an SCTP-SHUTDOWN_COMPLETE notification primitive to the local M2UA layer. At the M2UA Layer that initiated the request, the M2UA layer will send an M-SCTP_RELEASE confirm primitive to Layer Management when the association teardown is complete. At the peer M2UA Layer, an M-SCTP_RELEASE indication primitive is sent to Layer Management upon successful tear-down of an SCTP association. An M-SCTP_STATUS request primitive supports a Layer Management query of the local status of a particular SCTP association. The M2UA layer simply maps the M-SCTP_STATUS request primitive to an SCTP-STATUS primitive to the SCTP layer. When the SCTP responds, the M2UA layer maps the association status information to an M-SCTP_STATUS confirm primitive. No peer protocol is invoked. M-NOTIFY indication and M-ERROR indication indicate to Layer Management the notification or error information contained in a received M2UA Notify or Error message respectively. These indications can also be generated based on local M2UA events. An M-ASP_STATUS request primitive supports a Layer Management query of the status of a particular local or remote ASP. The M2UA layer responds with the status in an M-ASP_STATUS confirm primitive. No M2UA peer protocol is invoked. An M-AS_STATUS request supports a Layer Management query of the status of a particular AS. The M2UA responds with an M-AS_STATUS confirm primitive. No M2UA peer protocol is invoked. M-ASP_UP request, M-ASP_DOWN request, M-ASP_ACTIVE request and M-ASP_ INACTIVE request primitives allow Layer Management at an ASP to initiate state changes. Upon successful completion, a corresponding confirm primitive is provided by the M2UA layer to Layer Management. If an invocation is unsuccessful, an Error indication primitive is provided in the primitive. These requests result in outgoing ASP Up, ASP Down, ASP Active and ASP Inactive messages to the remote M2UA peer at an SGP or IPSP. All MGMT messages are sent on a sequenced stream to ensure ordering. SCTP stream '0' SHOULD be used. 4.2.2 MGMT message procedures Upon successful state changes resulting from reception of ASP Up, ASP Down, ASP Active and ASP Inactive messages from a peer M2UA, the M2UA layer SHOULD invoke corresponding M-ASP_UP, M-ASP_DOWN, M- ASP_ACTIVE and M-ASP_INACTIVE, M-AS_ACTIVE, M-AS_INACTIVE, and M- AS_DOWN indication primitives to the local Layer Management. M-NOTIFY indication and M-ERROR indication indicate to Layer Management the notification or error information contained in a received M2UA Notify or Error message. These indications can also be generated based on local M2UA events. All MGMT messages are sent on a sequenced stream to ensure ordering. SCTP stream '0' SHOULD be used. 4.3 Procedures to Support Service in Section 1.4.3 These procedures achieve the M2UA layer's "Support for management of active associations between SG and MGC" service. 4.3.1 AS and ASP State Maintenance The M2UA layer on the SG maintains the state of each ASP, in each Appliction Server that is configured to receive traffic. 4.3.1.1 ASP States The state of the each ASP, in each AS that it is configured, is maintained in the M2UA layer on the SG. The state of an ASP changes due to events. The events include * Reception of messages from peer M2UA layer at that ASP * Reception of some messages from the peer M2UA layer at other ASPs in the AS * Reception of indications from SCTP layer The ASP state transition diagram is shown in Figure 6. The possible states of an ASP are the following: ASP Down: Application Server Process is unavailable and/or the related SCTP association is down. Initially all ASPs will be in this state. An ASP in this state SHOULD NOT not be sent any M2UA messages. ASP-INACTIVE: The remote M2UA peer at the ASP is available (and the related SCTP association is up) but application traffic is stopped. In this state the ASP can be sent any non-MAUP M2UA messages. ASP-ACTIVE: The remote M2UA peer at the ASP is available and application traffic is active. Figure 6 ASP State Transition Diagram +----------------+ +----------------------| | | Alternate +-------| ASP-ACTIVE | | ASP | | | | Takeover | +----------------+ | | ^ | | | ASP | | ASP | | Active | | Inactive | | | v | | +----------------+ | | | | | +------>| ASP-INACTIVE | | | | | +----------------+ | ^ | ASP Down/ | ASP | | ASP Down / SCTP CDI/ | Up | | SCTP CDI / SCTP RI | | v SCTP RI | +----------------+ +--------------------->| | | ASP-DOWN | | | +----------------+ SCTP CDI: The local SCTP layer's Communication Down Indication to the Upper Layer Protocol (M2UA) on an SG. The local SCTP will send this indication when it detects the loss of connectivity to the ASP's peer SCTP layer. SCTP CDI is understood as either a SHUTDOWN COMPLETE notification and COMMUNICATION LOST notification from the SCTP. SCTP RI: The local SCTP layer's Restart Indication to the Upper Layer Protocol (M2UA) on an SG. The local SCTP will send this indication when it detects a restart from the ASP's peer SCTP layer. When an SCTP association fails at the SG, M2UA shall change the states of all ASPs reached through the aborted SCTP association to ASP-DOWN. Morneault, et al [Page 22] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 4.3.1.2 AS States The state of the AS is maintained in the M2UA layer on the SG. The state of an AS changes due to events. These events include the following: * ASP state transitions * Recovery timer triggers The possible states of an AS are the following: AS-DOWN: The Application Server is unavailable. This state implies that all related ASPs are in the ASP Down state for this AS. When the AS transitions to the AS-DOWN state, all of the SS7 links (Interface Identifiers) for this AS should be taken out-of-service. Initially the AS will be in this state. AS-INACTIVE: The Application Server is available but no application traffic is active (i.e., one or more related ASPs are in the ASP-INACTIVE 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 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 queueing messages and discards all previously queued messages. In addition, the SG MAY send the Stop primitive to MTP2 to take the link out of service. Note that the actions taken by the SG should be accordance with the appropriate MTP specifications. The AS will move to AS-Inactive if at least one ASP is in ASP-INACTIVE state, otherwise it will move to AS-DOWN state. If an ASP transitions to the ASP-DOWN state and all ASPs in the AS are in the ASP-DOWN state, then the SG SHALL send the Stop primitive to MTP2 to take the link out of service and moves the AS to the AS-DOWN state. Figure 7 AS State Transition Diagram +----------+ one ASP trans ACTIVE +-------------+ | |------------------------>| | | AS-INACT | | AS-ACTIVE | | | | | | |< | | +----------+ \ +-------------+ ^ | \ Tr Expires ^ | | | \ at least one | | | | \ ASP in UP | | | | \ | | | | \ | | | | \ | | one ASP | | \ one ASP | | Last ACTIVE ASP trans | | all ASP \------\ trans to | | trans to INACT to | | trans to \ ACTIVE | | or DOWN INACT | | DOWN \ | | (start Tr timer) | | \ | | | | \ | | | | \ | | | v \ | v +----------+ \ +-------------+ | | -| | | AS-DOWN | | AS-PENDING | | | | (queueing) | | |<------------------------| | +----------+ Tr Expiry and no +-------------+ ASP in INACTIVE state Tr = Recovery Timer Morneault, et al [Page 23] Internet Draft SS7 MTP2 User Adaptation Layer July 2001 4.3.2 ASPM procedures for primitives Before the establishment of an SCTP association the ASP state at both the SG and ASP is assumed to be in the state ASP-DOWN. As the ASP is responsible for initiating the setup of an SCTP association to an SG, the M2UA layer at an ASP receives an M-SCTP ESTABLISH request primitive from the Layer Management, the M2UA layer will try to establish an SCTP association with the remote M2UA peer at an SG. Upon reception of an eventual SCTP-COMMUNICATION_UP confirm primitive from the SCTP, the M2UA layer will invoke the primitive M-SCTP_ESTABLISH confirm to the Layer Management. At the SG, the M2UA layer will receive an SCTP-COMMUNICATION_UP indication primitive from the SCTP. The M2UA layer will then invoke the primitive M-SCTP_ESTABLISH indication to the Layer Management. Once the SCTP association is established and assuming that the local M2UA-User is ready, the local ASP M2UA 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 4.3.3. The Layer Management and the M2UA layer on SG can communicate the status of the application server using the M-AS_STATUS primitives. The Layer Managements and the M2UA layers on both the SG and ASP can communicate the status of an SCTP association using the M-SCTP_STATUS primitives. If the Layer Management on SG or ASP wants to bring down an SCTP association for management reasons, they would send M-SCTP_RELEASE request primitive to the local M2UA layer. The M2UA layer would release the SCTP association and upon receiving the SCTP Communication Down indication from the underlying SCTP layer, it would inform the local Layer Management using M-SCTP_RELEASE confirm primitive. If the M2UA layer receives an SCTP-COMMUNICATION_DOWN or Restart indication from the underlying SCTP layer, it will inform the Layer Management by invoking the M-SCTP_RELEASE indication primitive. At the SG, M2UA shall change the states of all ASPs reached through the aborted SCTP association to ASP DOWN. At the ASP, the M2UA layer will take action based on the appropriate MTP specification. The ASP may indicate to another ASP that it should become active. However, the ASP to ASP communication is out of the scope of this document. At an ASP, the Layer Management MAY try to reestablish the SCTP association using M-SCTP_ESTABLISH request primitive. 4.3.3 ASPM procedures for peer-to-peer messages All ASPM messages are sent on a sequenced stream to ensure ordering. SCTP stream '0' SHOULD be used. 4.3.3.1 ASP Up After an ASP has successfully established an SCTP association to an SG, the SG waits for the ASP to send an ASP Up message, indicating that the ASP M2UA peer is available. The ASP is always the initiator of the ASP Up exchange. When an ASP Up message is received at an SG and internally the ASP is not considered locked-out for local management reasons, the SG marks the remote ASP as Inactive. If the ASP UP message contains an ASP Identifier, the SG should save the ASP Identifier for that ASP. The SG responds with an ASP Up Ack message in acknowledgement. The SG sends an ASP Up Ack message in response to a received ASP Up message even if the ASP is already marked as ASP-INACTIVE at the SG. If for any local reason (e.g., management lock-out) the SGP cannot respond with an ASP