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 Feb 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 Feb 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. Security.................................................30 7. IANA Considerations......................................31 7.1 SCTP Payload Protocol Identifier.......................31 7.2 IUA Protocol Extensions................................31 8. Acknowledgements.........................................31 9. References...............................................32 10. Author's Addresses.......................................33 Morneault, et al [Page 2] Internet Draft SS7 MTP2 User Adaptation Layer Feb 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 active associations between the SG and MGC In other words, the Signaling Gateway will transport MTP Level 3 messages to a Media Gateway Controller (MGC) or IP Signaling Point (IPSP). In the case of delivery from an SG to an IPSP, both the SG and IPSP function as traditional SS7 nodes using the IP network as a new type of SS7 link. This allows for full MTP Level 3 message handling and network management capabilities. 1.2 Terminology MTP2-User - A protocol that normally uses the services of MTP Level 2 (i.e. MTP3). Interface - For the purposes of this document, an interface is a SS7 signaling link. 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]. 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. 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. 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. 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. Fail-over - The capability to re-route signaling traffic as required to an alternate Application Server Process, or group of ASPs, within an Application Server in the event of failure or unavailability of a currently used Application Server Process. Fail-back MAY apply upon the return to service of a previously unavailable Application Server Process. Morneault, et al [Page 3] Internet Draft SS7 MTP2 User Adaptation Layer Feb 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]. 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. 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 Network Byte Order: Most significant byte first, a.k.a Big Endian. Host - The computing platform that the ASP process is running on. 1.3 M2UA Overview The framework architecture that has been defined for SCN signaling transport over IP [6] uses multiple components, including 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 functional 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 Feb 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 dynamically registered remote 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. Active ASPs are those 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. 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 Feb 2001 ******** ************** * *_________________________________________* ******** * Host1 * * _________* * ASP1 * * * SG1 * SCTP Associations | * ******** * * *_______________________ | * * ******** | | ************** | | ******** | | * *_______________________________| * * | * SG2 * SCTP Associations | * *____________ | * * | | ******** | | ************** | |_________________* ******** * Host2 |____________________________* * ASP1 * * * ******** * * * ************** . . . 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 an SG from the SS7 network are assigned to a unique Application Server, based on the Interface Identifier of the message. The Application Server is in practical terms a list of all ASPs currently registered to process MTP2-User messages from certain Interface Identifiers. One or more ASPs in the list are normally active (i.e., handling traffic) while any others MAY be unavailable or inactive, to be possibly used in the event of failure or unavailability of the active ASP(s). The M2UA fail-over model supports an 1+k redundancy model, where 1 ASPs is the minimum number of redundant ASPs required to handle traffic and k ASPs are available to take over for a failed or unavailable ASP. Note that 1+1 active/standby redundancy is a subset of this model. A simplex 1+0 model is also supported as a subset, with no ASP redundancy. Morneault, et al [Page 6] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 To avoid a single point of failure, it is recommended that a minimum of two ASPs be in the 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 ASP1 in Host2. The AS list at SG1 might look like the following: Interface Identiers - Application Server #1 ASP1/Host1 - State = Active ASP1/Host2 - State = Inactive In this 1+1 redundancy case, ASP1 in Host1 would be sent any incoming message for the Interface Identifiers registered. ASP1 in Host2 would normally be brought to the active state upon failure of, or loss of connectivity to, 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. This includes the following services: 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 must be supported can be found in [7]. Morneault, et al [Page 7] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 1.4.2 Support for communication between Layer Management modules on SG and MGC It is envisioned that the M2UA layer needs to provide some messages that will facilitate communication between Layer Management modules on the SG and MGC. These primitives are shown below: 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., interface identifier value is not known to the SG). 1.4.3 Support for management of active associations between SG and MGC The M2UA layer on the SG keeps the state of various ASPs it is associated with. 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 Feb 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 Note that an ASP can be in more than one AS. 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(es). 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 user specified number of streams to be opened during the initialization. It is the responsibility of the M2UA layer to ensure proper management of these streams. Because of the unidirectional nature of streams, M2UA layers are not aware of the stream information from the peer M2UA layers. 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. It is recommended that a separate SCTP stream is used for each SS7 link. 1.5.3.2 SCTP Send Primitive M2UA shall set the lifetime parameter in the SEND primitive to SCTP when sending a message. When SCTP times out a message, M2UA shall abort the SCTP association and follow the same procedure as for a failed SCTP association. The default value for the lifetime shall be 2 seconds. Some messages, like STATUS_FLUSH_BUFFERS may need a shorter lifetime. This is for further study. 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. If the AS moves to the DOWN state while SS7 links are in-service, the SG SHOULD follow the MTP 2 processor outage procedures [2]. 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). If the M2UA layer on the SG receives an IP network congestion onset indication, the M2UA layer SHOULD inform the MTP2 layer of a Local Processor Outage. When the M2UA layer on the SG receives an IP network congestion abate indication, the M2UA layer SHOULD inform the MTP2 layer of a Local Processor Outage condition has been cleared. If the M2UA layer on the ASP receives an IP network congestion onset indication, the M2UA layer SHOULD inform the MTP3 layer of a Local Processor Outage. When the M2UA layer on the ASP receives an IP network congestion abate indication, the M2UA layer SHOULD inform the MTP3 layer of a Local Processor Outage condition has been cleared. 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 Feb 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-STCP 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 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 is 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 Feb 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/M3UA/SUA] 1 Transfer Messages [M3UA] 2 SS7 Signalling Network Management (SSNM) Messages [M3UA/SUA] 3 ASP State Maintenance (ASPSM) Messages [IUA/M2UA/M3UA/SUA] 4 ASP Traffic Maintenance (ASPTM) Messages [IUA/M2UA/M3UA/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 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 TTC Data 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 Feb 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 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 / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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 value of 65535 is reserved for IETF-defined extensions. Values other than those defined in specific parameter description are reserved for use by the IETF. 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) Morneault, et al [Page 12] Internet Draft SS7 MTP2 User Adaptation Layer Feb 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 (0xe) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Protocol Data field contains the MTP2-User application message in network byte order starting with the Signaling Information Octet (SIO). 3.3.1.2 TTC Data The TTC Data message contains a TTC SS7 MTP2-User Protocol Data Unit (PDU). The TTC Data message contains the following parameter: Protocol Data (Mandatory) The format for the TTC 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 (0xf) | 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. 3.3.1.3 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 of 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. 3.3.1.4 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. 3.3.1.5 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 Feb 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 (0x10) | 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 transmit and retransmit buffers STATUS_CONTINUE 0x5 Continue STATUS_AUDIT 0x6 Audit state of link 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. There is also a field to indicate whether or not the the State Request was successfully completed. Morneault, et al [Page 13] Internet Draft SS7 MTP2 User Adaptation Layer Feb 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 (0x16) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | State | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Result | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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 transmit and retransmit buffers STATUS_CONTINUE 0x5 Continue STATUS_AUDIT 0x6 Audit state of link The valid values for the Result field are shown in the following table. Define Value Description STATUS_SUCCESS 0x0 Successfully completed Request STATUS_FAILURE 0x1 Failed to complete Request 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 (0x11) | 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 3.3.1.7 Congestion Indication The Congestion Indication message can be sent from a 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 (0x15) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Congestion Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 For networks that do not support multiple levels of congestion, only the LEVEL_NONE and LEVEL_1 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. 3.3.1.8 Retrieval (Request, Confirm) The MTP2 Retrieval Request message is used during the MTP Level 3 changeover procedure to request the BSN, to retrieve PDUs from the retransmit queue or to flush PDUs from the retransmit queue. Morneault, et al [Page 14] Internet Draft SS7 MTP2 User Adaptation Layer Feb 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 (0x12) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Action | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x13) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | seq_num | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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 retransmit queue ACTION_DROP_MSGS 0x3 Drop the PDUs in the retransmit queue In the Retrieval Request message, the seq_num field SHOULD be ignored if the Action field is ACTION_RTRV_BSN or ACTION_DROP_MSGS. The seq_num field contains the Forward Sequnce Number (FSN) of the far end if the Action is ACTION_RTRV_MSGS. When the Signaling Gateway sends a Retrieval Confirm to this request, it echos the action and puts the Backward Sequence Number (BSN) in the seq_num field if the action was ACTION_RTRV_BSN. If there is a failure in retrieving the BSN, the seq_num SHOULD contain a -1 (0xffffffff). For a Retrieval Confirm with Action of ACTION_RTRV_MSGS, the value of of seq_num will be set to zero for success or -1 (0xffffffff) for failure. A failure means that the buffers could not be retrieved. For a Retrieval Confirm with an Action of ACTION_DROP_MSGS, the value received in the seq_num field will be ignored. 3.3.1.9 Retrieval Indication The Retrieval Indication message is sent by the Signaling Gateway with a PDU from the retransmit queue. The Retrieval Indication message does not contain the Action or seq_num fields, just a MTP3 Protocol Data Unit (PDU) from the retransmit queue. The M2UA implementation MAY consider the use of the bundling feature of SCTP for Retrieval Indication messages. 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 (0x14) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PDU from retransmit queue | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3.3.1.10 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 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 Feb 2001 The ASPUP message contains the following parameters 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 (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | INFO String* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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 Feb 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 Within a particular Interface Identifier, only one 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. Morneault, et al [Page 17] Internet Draft SS7 MTP2 User Adaptation Layer Feb 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 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 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 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 Traffic Mode Type (Mandatory) 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 (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 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 (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 Traffic Mode Type are shown in the following table: Value Description 0x1 Over-ride 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 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: Traffic Mode Type (Mandatory) 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 (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 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 (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 of the Traffic Mode Type and Interface Identifier parameters 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 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 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 Invalid Stream Identifier 0x8 Unsupported Interface Identifier Type 0x9 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. 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 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 Feb 2001 3.3.3.2 Notify (NTFY) The Notify message used to provide an autonomous indication of M2UA events to an M2UA peer. The NTFY message contains the following parameters: Status Type Status Identification 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 Identification | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 Identification | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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. 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 This notification is not based on the SG reporting the state change of an ASP or AS. In the Insufficient ASP Resources case, the SG is indicating to an "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, an ASP is informed when an alternate ASP transitions to the ASP-Active state in Over-ride mode. 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 Feb 2001 4.0 Procedures The M2UA layers 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 2) to its peer. The M2UA layer MUST fill in various fields of the common and specific headers correctly. In addition the message needs 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 Feb 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 these primitives from the local layer, the M2UA layer will send the corresponding MGMT message (Error) to its peer. The M2UA layer MUST fill in the various fields of the common and specific headers correctly. An M-SCTP ESTABLISH request from Layer Management will initiate the establishment of an SCTP association. An M-SCTP ESTABLISH confirm will be sent to Layer Management when the initiated association set-up is complete. An M-SCTP ESTABLISH indication is sent to Layer Management upon successful completion of an incoming SCTP association set-up from a peer M2UA node An M-SCTP RELEASE request from Layer Management will initiate the tear-down of an SCTP association. An M-SCTP RELEASE confirm will be sent by Layer Management when the association teardown is complete. An M-SCTP RELEASE indication is sent to Layer Management upon successful tear-down of an SCTP association initiated by a peer M2UA. M-SCTP STATUS request and indication support a Layer Management query of the local status of a particular SCTP association. 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. M-ASP STATUS request/indication and M-AS-STATUS request/indication support a Layer Management query of the local status of a particular ASP or AS. No M2UA peer protocol is invoked. M-ASP Up request, M-ASP Down request, M-ASP-INACTIVE request and M-ASP-ACTIVE request allow Layer Management at an ASP to initiate state changes. These requests result in outgoing M2UA ASP UP, ASP DOWN, ASP INACTIVE and ASP ACTIVE messages. M-ASP Up confirmation, M-ASP Down confirmation, M-ASP-INACTIVE confirmation and M-ASP-ACTIVE confirmation indicate to Layer Management that the previous request has been confirmed. 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 receipt of MGMT messages the M2UA layer MUST invoke the corresponding Layer Management primitives indications (e.g., M-AS Status ind., M-ASP Status ind., M-ERROR ind...) 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 State Maintenance The M2UA layer on the SG maintains the state of each AS, in each Appliction Server that it 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-INACT | | +-------------+ | ^ | ASP Down/ | ASP | | ASP Down / SCTP CDI | Up | | SCTP CDI | | v | +-------------+ +--------------------->| | | 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. 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. When an SCTP association fails at the ASP, M2UA shall either cause other ASPs to become active or send link-out-of-service primitives to MTP3. Morneault, et al [Page 22] Internet Draft SS7 MTP2 User Adaptation Layer Feb 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 SHALL send the Stop primitive to MTP2 to take the link out of service. 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 Feb 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 "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 indication from the underlying SCTP layer, it will inform the Layer Management by invoking the M-SCTP RELEASE indication primitive. The state of the ASP will be moved to "Down" at both the SG and ASP. At an ASP, the Layer Management MAY try to reestablish the SCTP association using M-SCTP ESTABLISH request primitive. 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 is used. 4.3.3.1 ASP-Inactive 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. The SG responds with an ASP Up Ack message in acknowledgement. The SG sends an-Up Ack message in response to a received ASP Up message even if the ASP is already marked as "Inactive" at the SG. If for any local reason the SG cannot respond with an ASP Up, the SG responds to a ASP Up with a ASP Down Ack message. When the ASP sends an ASP Up it starts timer T(ack). If the ASP does not receive a response to an ASP Up within T(ack), the ASP MAY restart T(ack) and resend ASP Up messages until it receives an ASP Up Ack message. T(ack) SHOULD be provisionable, with a default of 2 seconds. Alternatively, retransmission of ASP Up messages MAY be put under control of Layer Management. In this method, expiry of T(ack) results in a M-ASP-Up confirmation carrying a negative indication. The ASP MUST wait for the ASP Up Ack message from the SG before sending any ASP traffic control messages (ASPAC or ASPIA) or Data messages or it will risk message loss. If the SG receives Data messages before an ASP Up is received, the SG SHOULD discard. Morneault, et al [Page 24] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 4.3.3.2 ASP Down The ASP will send an ASP Down to an SG when the ASP is to be removed from the list of ASPs in all Application Servers that it is a member and no longer receive any M2UA traffic or management messages. Whether the ASP is permanently removed from an AS is a function of configuration management. The SG marks the ASP as "Down" and returns an ASP Down Ack message to the ASP if one of the following events occur: - an ASP Down message is received from the ASP, - another ASPM message is received from the ASP and the SG has locked out the ASP for management reasons. The SG sends an ASP Down Ack message in response to a received ASP Down message from the ASP even if the ASP is already marked as "Down" at the SG. At the ASP, the ASP Down Ack message received is not acknowledged. Layer Management is informed with an M-ASP Down confirm primitive. When the ASP sends an ASP Down it starts timer T(ack). If the ASP does not receive a response to an ASP Down within T(ack), the ASP MAY restart T(ack) and resend ASP Down messages until it receives an ASP Down Ack message. T(ack) SHOULD be provisionable, with a default of 2 seconds. Alternatively, retransmission of ASP Down messages MAY be put under control of Layer Management. In this method, expiry of T(ack) results in a M-ASP-Down confirmation carrying a negative indication. 4.3.3.3 M2UA Version Control If a ASP Up message with an unsupported version is received, the receiving end responds with an Error message, indicating the version the receiving node supports. This is useful when protocol version upgrades are being performed in a network. A node upgraded to a newer version SHOULD support the older versions used on other nodes it is communicating with. Because ASPs initiate the ASP Up procedure it is assumed that the Error message would normally come from the SG. 4.3.3.4 ASP-Active Any time after the ASP has received a ASP Up Ack from the SG, the ASP sends an ASP Active (ASPAC) to the SG indicating that the ASP is ready to start processing traffic. In the case where an ASP is configured/- registered to process the traffic for more than one Application Server across an SCTP association, the ASPAC contains one or more Interface Identifiers to indicate for which Application Servers the ASPAC applies. When an ASP Active (ASPAC) message is received, the SG responds to the ASP with a ASPAC Ack message acknowledging that the ASPAC was received and starts sending traffic for the associated Application Server(s) to that ASP. Note that the SG sends an ASP Active Ack message in response to a received ASP Active message even if the ASP is already marked as "Active" at the SG. The ASP MUST wait for the ASP Active Ack message from the SG before sending any Data messages or it will risk message loss. If the SG receives MAUP messages before an ASP Active is received, the SG SHOULD discard these messages. Morneault, et al [Page 25] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 When the ASP sends an ASP Active it starts timer T(ack). If the ASP does not receive a response to an ASP Active within T(ack), the ASP MAY restart T(ack) and resend ASP Active messages until it receives an ASP Active Ack message. T(ack) SHOULD be provisionable, with a default of 2 seconds. Alternatively, retransmission of ASP Active messages may be put under control of Layer Management. In this method, expiry of T(ack) results in a M-ASP-Active confirmation carrying a negative indication. There is one mode of Application Server traffic handling in the SG M2UA - Over-ride. The Type parameter in the ASPAC messge indicates the mode used in a particular Application Server. If the SG determines that the mode indicates in an ASPAC is incompatible with the traffic handling mode currently used in the AS, the SG responds with an Error message indicating Unsupported Traffic Handling Mode. For Over-ride mode AS, the reception of an ASPAC message at an SG causes the redirection of all traffic for the AS to the ASP that sent the ASPAC. The SG responds to the ASPAC with an ASP-Active Ack message to the ASP. Any previously active ASP in the AS is now considered Inactive and will no longer receive traffic from the SG within the AS. The SG sends a Notify (Alternate ASP-Active) to the previously active ASP in the AS, after stopping all traffic to that ASP. 4.3.3.5 ASP Inactive When an ASP wishes to withdraw from receiving traffic within an AS, the ASP sends an ASP Inactive (ASPIA) to the SG. In the case where an ASP is configured/registered to process the traffic for more than one Application Server across an SCTP association, the ASPIA contains one or more Interface Ids to indicate for which Application Servers the ASPIA applies. There is one mode of Application Server traffic handling in the SG M2UA when withdrawing an ASP from service - Over-ride. The Type parameter in the ASPIA messge indicates the mode used in a particular Application Server. If the SG determines that the mode indicates in an ASPAC is incompatible with the traffic handling mode currently used in the AS, the SG responds with an Error message indicating Unsupported Traffic Handling Mode. In the case of an Over-ride mode AS, where normally another ASP has already taken over the traffic within the AS with an Over-ride ASPAC, the ASP which sends the ASPIA is already considered by the SG to be "Inactive" (i.e., in the "Inactive" state). An ASPIA Ack message is sent to the ASP, after ensuring that all traffic is stopped to the ASP. When the ASP sends an ASP Inactive it starts timer T(ack). If the ASP does not receive a response to an ASP Inactive within T(ack), the ASP MAY restart T(ack) and resend ASP Inactive messages until it receives an ASP Inactive Ack message. T(ack) SHOULD be provisionable, with a default of 2 seconds. Alternatively, retransmission of ASP Inactive messages may be put under control of Layer Management. In this method, expiry of T(ack) results in a M-ASP-Inactive confirmation carrying a negative indication. If no other ASPs are Active in the Application Server, the SG either discards all incoming messages for the AS or starts buffering the incoming messages for T(r) seconds, after which messages will be discarded. T(r) is configurable by the network operator. If the SG receives an ASPAC from an ASP in the AS before expiry of T(r), the buffered traffic is directed to the ASP and the timer is cancelled. Morneault, et al [Page 26] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 4.3.3.6 Notify A Notify message reflecting a change in the AS state is sent to all ASPs in the AS, except those in the "Down" state, with appropriate Status Identification. In the case where a Notify (AS-Pending) message is sent by an SG that now has no ASPs active to service the traffic, the Notify does not explicitly force the ASP(s) receiving the message to become active. The ASPs remain in control of what (and when) action is taken. 5.0 Examples of MTP2 User Adaptation (M2UA) Procedures 5.1 Establishment of associations between SG and MGC examples 5.1.1 Single ASP in an Application Server (1+0 sparing) This scenario shows the example M2UA message flows for the establishment of traffic between an SG and an ASP, where only one ASP is configured within an AS (no backup). It is assumed that the SCTP association is already set-up. SG ASP1 | |<---------ASP Up----------| |--------ASP Up Ack------->| | | |<-------ASP Active--------| |------ASP_Active Ack----->| | | 5.1.2 Two ASPs in Application Server (1+1 sparing) This scenario shows the example M2UA message flows for the establishment of traffic between an SG and two ASPs in the same Application Server, where ASP1 is configured to be active and ASP2 to be standby in the event of communication failure or the withdrawal from service of ASP1. ASP2 MAY act as a hot, warm, or cold standby depending on the extent to which ASP1 and ASP2 share call/transaction state or can communicate call state under failure/withdrawal events. SG ASP1 ASP2 | | | |<--------ASP Up----------| | |-------ASP Up Ack------->| | | | | |<-----------------------------ASP Up----------------| |----------------------------ASP Up Ack------------->| | | | | | | |<-------ASP Active-------| | |-----ASP-Active Ack----->| | | | | Morneault, et al [Page 27] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 Morneault, et al [Page 28] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 5.2 ASP Traffic Fail-over Examples 5.2.1 (1+1 Sparing, withdrawal of ASP, Back-up Over-ride) Following on from the example in Section 5.1.2, and ASP withdraws from service: SG ASP1 ASP2 | | | |<-----ASP Inactive-------| | |----ASP Inactive Ack---->| | |--------------------NTFY(AS-Down) (Optional)------->| | | | |<------------------------------ ASP Active----------| |-----------------------------ASP-Active Ack)------->| | | In this case, the SG notifies ASP2 that the AS has moved to the Down state. The SG could have also (optionally) sent a Notify message when the AS moved to the Pending state. Note: If the SG detects loss of the M2UA peer (through a detection of SCTP failure), the initial SG-ASP1 ASP Inactive message exchange would not occur. 5.2.2 (1+1 Sparing, Back-up Over-ride) Following on from the example in Section 5.1.2, and ASP2 wishes to over- ride ASP1 and take over the traffic: SG ASP1 ASP2 | | | |<------------------------------ ASP Active----------| |-----------------------------ASP-Active Ack-------->| |----NTFY( Alt ASP-Act)-->| | (optional) | | In this case, the SG notifies ASP1 that an alternative ASP has overridden it. Morneault, et al [Page 29] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 5.3 SG to MGC, MTP Level 2 to MTP Level 3 Boundary Procedures When the M2UA layer on the ASP has a MAUP message to send to the SG, it will do the following: - Determine the correct SG - Find the SCTP association to the chosen SG - Determine the correct stream in the SCTP association based on the SS7 link - Fill in the MAUP message, fill in M2UA Message Header, fill in Common Header - Send the MAUP message to the remote M2UA peer in the SG, over the SCTP association When the M2UA layer on the SG has a MAUP message to send to the ASP, it will do the following: - Determine the AS for the Interface Identifier - Determine the Active ASP (SCTP association) within the AS - Determine the correct stream in the SCTP association based on the SS7 link - Fill in the MAUP message, fill in M2UA Message Header, fill in Common Header - Send the MAUP message to the remote M2UA peer in the ASP, over the SCTP association 5.3.1 SS7 Link Alignment The MGC can request that a SS7 link be brought into alignment using the normal or emergency procedure. An example of the message flow to bring a SS7 link in-service using the normal alignment procedure is shown below. MTP2 M2UA M2UA MTP3 SG SG ASP ASP <----Start Req---|<---Establish Req----|<----Start Req------ ---In Serv Ind-->|----Establish Cfm--->|----In Serv Ind----> An example of the message flow to bring a SS7 link in-service using the emergency alignment procedure. MTP2 M2UA M2UA MTP3 SG SG ASP ASP <----Emer Req----|<--State Req (STATUS_EMER_SET)----|<----Emer Req--- -----Emer Cfm--->|---State Cfm (STATUS_EMER_SET)--->|----Emer Cfm----> <---Start Req----|<-------Establish Req-------------|<---Start Req---- ---In Serv Ind-->|--------Establish Cfm------------>|---In Serv Ind--> Morneault, et al [Page 24] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 5.3.2 SS7 Link Release The MGC can request that a SS7 link be taken out-of-service. It uses the Release Request message as shown below. MTP2 M2UA M2UA MTP3 SG SG ASP ASP <-----Stop Req-----|<---Release Req------|<-----Stop Req------ --Out of Serv Ind->|----Release Cfm----->|--Out of Serv Ind--> The SG can autonomously indicate that a SS7 link has gone out-of-service as shown below. MTP2 M2UA M2UA MTP3 SG SG ASP ASP --Out of Serv->|----Release Ind----->|--Out of Serv--> 5.3.3 Set and Clear Local Processor Outage The MGC can set a Local Processor Outage condition. It uses the State Request message as shown below. MTP2 M2UA M2UA MTP3 SG SG ASP ASP <----LPO Req----|<---State Req (STATUS_LPO_SET)----|<----LPO Req--- -----LPO Cfm--->|----State Cfm (STATUS_LPO_SET)--->|----LPO Cfm----> The MGC can clear a Local Processor Outage condition. It uses the State Request message as shown below. MTP2 M2UA M2UA MTP3 SG SG ASP ASP <---LPO Req---|<---State Req (STATUS_LPO_CLEAR)----|<----LPO Req--- ----LPO Cfm-->|----State Cfm (STATUS_LPO_CLEAR)--->|----LPO Cfm----> 5.3.4 Notification of Remote Processor Outage The SG can indicate Remote has entered or exited the Processor Outage condition. It uses the State Indication message as shown below. MTP2 M2UA M2UA MTP3 SG SG ASP ASP ----RPO Ind---->|----State Ind (EVENT_RPO_ENTER)-->|-----RPO Ind----> -RPO Rcvr Ind-->|----State Ind (EVENT_RPO_EXIT)--->|--RPO Rcvr Ind--> Morneault, et al [Page 30] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 5.3.5 Notification of Link Congestion The SG can indicate that a link has become congested. It uses the Congestion Indication message as shown below. MTP2 M2UA M2UA MTP3 SG SG ASP ASP ----Cong Ind---->|--------Cong Ind (STATUS)------->|----Cong Ind----> -Cong Cease Ind->|--------Cong Ind (STATUS)------->|-Cong Cease Ind-> 5.3.6 SS7 Link Changeover An example of the message flow for an error free changeover is shown below. In this example, there were three messages in the retransmission queue that needed to be retrieved. MTP2 M2UA M2UA MTP3 SG SG ASP ASP <-Rtrv BSN Req-|<--Rtrv Req (ACTION_RTRV_BSN)--|<--Rtrv BSN Req--- (seq_num = 0) -Rtrv BSN Cfm->|---Rtrv Cfm (ACTION_RTRV_BSN)->|---Rtrv BSN Cfm--> (seq_num = BSN) <-Rtrv Msg Req-|<-Rtrv Req (ACTION_RTRV_MSGS)--|<--Rtrv Msg Req--- (seq_num = FSN) -Rtrv Msg Cfm->|--Rtrv Cfm (ACTION_RTRV_MSGS)->|---Rtrv Msg Cfm--> (seq_num = 0) -Rtrv Msg Ind->|---------Retrieval Ind ------->|---Rtrv Msg Ind--> -Rtrv Msg Ind->|---------Retrieval Ind ------->|---Rtrv Msg Ind--> -Rtrv Msg Ind->|---------Retrieval Ind ------->|---Rtrv Msg Ind--> -Rtrv Compl Ind->|----Retrieval Compl Ind ---->|-Rtrv Compl Ind--> Note: The number of Retrieval Indication is dependent on the number of messages in the retransmit queue that have been requested. Only one Retrieval Complete Indication SHOULD be sent. An example of a message flow with an error retrieving the BSN is shown below. MTP2 M2UA M2UA MTP3 SG SG ASP ASP <-Rtrv BSN Req-|<--Rtrv Req (ACTION_RTRV_BSN)--|<--Rtrv BSN Req--- -BSN Not Rtrv->|---Rtrv Cfm (ACTION_RTRV_BSN)->|---BSN Not Rtrv--> (seq_num = -1) An example of a message flow with an error retrieving the messages is shown below. <-Rtrv BSN Req-|<--Rtrv Req (ACTION_RTRV_BSN)--|<--Rtrv BSN Req--- -Rtrv BSN Cfm->|---Rtrv Cfm (ACTION_RTRV_BSN)->|---Rtrv BSN Cfm--> (seq_num = BSN) <-Rtrv Msg Req-|<-Rtrv Req (ACTION_RTRV_MSGS)--|<--Rtrv Msg Req--- (seq_num = FSN) -Rtrv Msg Cfm->|--Rtrv Cfm (ACTION_RTRV_MSGS)->|---Rtrv Msg Cfm--> (seq_num = -1) An example of a message flow for a request to drop messages (clear retransmission buffers) is shown below. MTP2 M2UA M2UA MTP3 SG SG ASP ASP <-Clr RTB Req-|<--Rtrv Req (ACTION_DROP_MSGS)--|<--Clr RTB Req--- -Clr RTB Ind->|---Rtrv Cfm (ACTION_DROP_MSGS)->|---Clr RTB Ind--> 5.3.7 Flush and Continue The following message flow shows a request to flush buffers. MTP2 M2UA M2UA MTP3 SG SG ASP ASP <--Flush Req----|<-State Req (STATUS_FLUSH_BUFS)--|<---Flush Req-- ---Flush Cfm--->|--State Cfm (STATUS_FLUSH_BUFS)->|---Flush Cfm--> The following message flow shows a request to continue. MTP2 M2UA M2UA MTP3 SG SG ASP ASP <---Cont Req----|<--State Req (STATUS_CONTINUE)---|<---Cont Req--- ----Cont Cfm--->|---State Cfm (STATUS_CONTINUE)-->|----Cont Cfm--> 5.3.8 Auditing of SS7 link state It may be necessary for the ASP to audit the current state of a SS7 link. The flows below show an example of the request and all the potential responses. Below is an example in which the SS7 link is out-of-service. MTP2 M2UA M2UA MGMT SG SG ASP ASP |<----State Req (STATUS_AUDIT)----|<----Audit------- |-----State Cfm (STATUS_AUDIT)--->| MTP3 ASP |-----------Release Ind---------->|-Out of Serv Ind -> Below is an example in which the SS7 link is in-service. MTP2 M2UA M2UA MGMT SG SG ASP ASP |<----State Req (STATUS_AUDIT)----|<----Audit------- |-----State Cfm (STATUS_AUDIT)--->| MTP3 ASP |-----------Establish Cfm-------->|---In Serv Ind --> Below is an example in which the SS7 link is in-service, but congested. MTP2 M2UA M2UA MGMT SG SG ASP ASP |<----State Req (STATUS_AUDIT)----|<----Audit------- |-----State Cfm (STATUS_AUDIT)--->| MTP3 ASP |-----------Establish Ind-------->|---In Serv Ind --> |----------Congestion Ind-------->|---Cong Ind -----> Below is an example in which the SS7 link is in-service, but in Remote Processor Outage. MTP2 M2UA M2UA MGMT SG SG ASP ASP |<----State Req (STATUS_AUDIT)----|<----Audit------- |-----State Cfm (STATUS_AUDIT)--->| MTP3 ASP |-----------Establish Ind-------->|---In Serv Ind --> |---State Ind (EVENT_RPO_ENTER)-->|----RPO Enter ---> 6.0 Security M2UA is designed to carry signaling messages for telephony services. As such, M2UA MUST involve the security needs of several parties: the end users of the services; the network providers and the applications involved. Additional requirements MAY come from local regulation. While having some overlapping security needs, any security solution SHOULD fulfill all of the different parties' needs. 6.1 Threats There is no quick fix, one-size-fits-all solution for security. As a transport protocol, M2UA has the following security objectives: * Availability of reliable and timely user data transport. * Integrity of user data transport. * Confidentiality of user data. M2UA runs on top of SCTP. SCTP [5] provides certain transport related security features, such as: * Blind Denial of Service Attacks * Flooding * Masquerade * Improper Monopolization of Services When M2UA is running in professionally managed corporate or service provider network, it is reasonable to expect that this network includes an appropriate security policy framework. The "Site Security Handbook" [10] SHOULD be consulted for guidance. Morneault, et al [Page 31] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 When the network in which M2UA runs in involves more than one party, it MAY NOT be reasonable to expect that all parties have implemented security in a sufficient manner. In such a case, it is recommended that IPSEC is used to ensure confidentiality of user payload. Consult [11] for more information on configuring IPSEC services. 6.2 Protecting Confidentiality Particularly for mobile users, the requirement for confidentiality MAY include the masking of IP addresses and ports. In this case application level encryption is not sufficient; IPSEC ESP SHOULD be used instead. Regardless of which level performs the encryption, the IPSEC ISAKMP service SHOULD be used for key management. 7.0 IANA Considerations 7.1 SCTP Payload Protocol Identifier A request will be made to IANA to assign an M2UA value for the Payload Protocol Identifier in SCTP Payload Data chunk. The following SCTP Payload Protocol Identifier will be registered: M2UA 0x10 The SCTP Payload Protocol Identifier is included in each SCTP Data chunk, to indicate which protocol the SCTP is carrying. This Payload Protocol Identifier is not directly used by SCTP but MAY be used by certain network entities to identify the type of information being carried in a Data chunk. The User Adaptation peer MAY use the Payload Protocol Identifier as a way of determining additional information about the data being presented to it by SCTP. 7.2 M2UA Protocol Extensions This protocol may also be extended through IANA in three ways: -- through definition of additional message classes, -- through definition of additional message types, and -- through definition of additional message parameters. The definition and use of new message classes, types and parameters is an integral part of SIGTRAN adaptation layers. Thus, these extensions are assigned by IANA through an IETF Consensus action as defined in [RFC2434]. The proposed extension must in no way adversely affect the general working of the protocol. 7.2.1 IETF Defined Message Classes The documentation for a new message class MUST include the following information: (a) A long and short name for the message class. (b) A detailed description of the purpose of the message class. 7.2.2 IETF Defined Message Types Documentation of the message type MUST contain the following information: (a) A long and short name for the new message type. (b) A detailed description of the structure of the message. (c) A detailed definition and description of intended use of each field within the message. (d) A detailed procedural description of the use of the new message type within the operation of the protocol. (e) A detailed description of error conditions when receiving this message type. When an implementation receives a message type which it does not support, it MUST respond with an Error (ERR) message with an Error Code of Unsupported Message Type. 7.2.3 IETF-defined TLV Parameter Extension Documentation of the message parameter MUST contain the following information: (a) Name of the parameter type. (b) Detailed description of the structure of the parameter field. This structure MUST conform to the general type-length-value format described in Section 3.1.5. (c) Detailed definition of each component of the parameter value. (d) Detailed description of the intended use of this parameter type, and an indication of whether and under what circumstances multiple instances of this parameter type may be found within the same message type. 8.0 Acknowledgements The authors would like to thank John Loughney, Neil Olson, Michael Tuexen, Nikhil Jain, Steve Lorusso, Dan Brendes, Joe Keller, Heinz Prantner, Barry Nagelberg, Naoto Makinae and Brian Bidulock for their valuable comments and suggestions. Morneault, et al [Page 32] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 9.0 References [1] ITU-T Recommendation Q.700, 'Introduction To ITU-T Signalling System No. 7 (SS7)' [2] ITU-T Recommendation Q.701-Q.705, 'Signalling System No. 7 (SS7) - Message Transfer Part (MTP)' [3] ANSI T1.111 'Signalling System Number 7 - Message Transfer Part' [4] Bellcore GR-246-CORE 'Bell Communications Research Specification of Signaling System Number 7', Volume 1, December 1995 [5] Stream Control Transmission Protocol, RFC 2960, October 2000 [6] Architectural Framework for Signaling Transport, RFC 2719, October 1999 [7] ITU-T Recommendation Q.2140, 'B-ISDN ATM Adaptation Layer', February 1995 [8] ITU-T Recommendation Q.2210, 'Message transfer part level 3 functions and messages using the services of ITU-T Recommendation Q.2140', August 1995 [9] ITU-T Recommendation Q.751.1, 'Network Element Management Information Model for the Messsage Transfer Part', October 1995 [10] Site Security Handbook, RFC 2196, September 1997 [11] Security Architecture for the Internet Protocol, RFC 2401 [12] draft-stewart-srwnd-sctp-sigtran-01.txt, SCTP Stream Based Flow Control, November 2000 10.0 Issues To Be Addressed 1. SCTP congestion (what does M2UA on SG and MGC do) Morneault, et al [Page 33] Internet Draft SS7 MTP2 User Adaptation Layer Feb 2001 10.0 Author's Addresses Ken Morneault Tel: +1-703-484-3323 Cisco Systems Inc. EMail: kmorneau@cisco.com 13615 Dulles Technology Drive Herndon, VA. 20171 USA Ram Dantu, Ph.D. Tel +1-469-255-0716 Cisco Systems EMail rdantu@cisco.com 17919 Waterview Dallas, TX 75252 USA Greg Sidebottom Tel: +1-613-763-7305 Nortel Networks EMail: gregside@nortelnetworks.com 3685 Richmond Rd, Nepean, Ontario Canada K2H5B7 Tom George Tel: +1-972-519-3168 Alcatel USA EMail: tom.george@usa.alcatel.com 1000 Coit Road Plano, TX 74075 USA Brian Bidulock Tel +1-972-839-4489 OpenSS7 Project EMail: bidulock@openss7.org c/o #424, 4701 Preston Park Blvd. Dallas, TX 75093 USA Jacob Heitz Tek +1-510-747-2917 Lucent Technologies Email: jheitz@lucent.com 1701 Harbor Bay Parkway Alameda, CA, 94502 USA This Internet Draft expires April 2001.