Network Working Group K. Morneault Request for Comments: 3331 Cisco Systems Category: Standards Track R. Dantu NetRake G. Sidebottom Signatus Technologies B. Bidulock OpenSS7 J. Heitz Lucent September 2002 Signaling System 7 (SS7) Message Transfer Part 2 (MTP2) - User Adaptation Layer Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract This document defines a protocol for the backhauling of Signaling System 7 Message Transfer Part 2 (SS7 MTP2) User signalling messages over IP using the Stream Control Transmission Protocol (SCTP). This protocol would be used between a Signalling Gateway (SG) and Media Gateway Controller (MGC). It is assumed that the SG receives SS7 signalling over a standard SS7 interface using the SS7 Message Transfer Part (MTP) to provide transport. The Signalling Gateway would act as a Signalling Link Terminal. Morneault, et. al. Standards Track [Page 1] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 Table of Contents 1. Introduction.............................................. 2 1.1 Scope.................................................. 3 1.2 Terminology............................................ 3 1.3 M2UA Overview.......................................... 5 1.4 Services Provided by the M2UA Adaptation Layer......... 7 1.5 Functions Provided by the M2UA Layer................... 9 1.6 Definition of the M2UA Boundaries..................... 12 2. Conventions.............................................. 16 3. Protocol Elements........................................ 16 3.1 Common Message Header................................. 16 3.2 M2UA Message Header................................... 22 3.3 M2UA Messages......................................... 23 4. Procedures............................................... 58 4.1 Procedures to Support the M2UA-User Layer............. 58 4.2 Receipt of Primitives from the Layer Management....... 59 4.3 AS and ASP State Maintenance.......................... 61 4.4 Link Key Management Procedures........................ 73 5. Examples of MTP2 User Adaptation (M2UA) Procedures....... 75 5.1 Establishment of associations between SGP and MGC..... 75 examples 5.2 ASP Traffic Fail-over Examples........................ 77 5.3 SGP to MGC, MTP Level 2 to MTP Level 3 Boundary Procedures............................................ 78 6. Timer Values............................................. 85 7. Security Considerations.................................. 85 7.1 Threats................................................ 85 7.2 Protecting Confidentiality............................. 86 8. IANA Considerations...................................... 86 8.1 SCTP Payload Protocol Identifier....................... 86 8.2 M2UA Protocol Extensions............................... 86 9. Acknowledgements......................................... 87 10. References............................................... 88 Appendix A: Signalling Network Architecture.................. 90 Authors' Addresses........................................... 92 Full Copyright Statement..................................... 94 1. Introduction This document defines a protocol for the backhauling of SS7 [1] MTP2 User [2] [3] [4] (i.e. MTP3) signalling messages over IP using the Stream Control Transmission Protocol (SCTP) [8]. This protocol would be used between a Signalling Gateway (SG) and Media Gateway Controller (MGC). Morneault, et. al. Standards Track [Page 2] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 1.1 Scope There is a need for Switched Circuit Network (SCN) signalling protocol delivery from a Signalling Gateway (SG) to a Media Gateway Controller (MGC) [9]. The delivery mechanism addresses the following objectives: * Support for MTP Level 2 / MTP Level 3 interface boundary * Support for communication between Layer Management modules on SG and MGC * Support for management of SCTP active associations between the SG and MGC The SG will terminate up to MTP Level 2 and the MGC will terminate MTP Level 3 and above. In other words, the SG will transport MTP Level 3 messages over an IP network to a MGC. 1.2 Terminology Application Server (AS) - A logical entity serving a specific application instance. An example of an Application Server is a MGC handling the MTP Level 3 and call processing for SS7 links terminated by the Signalling 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 active or standby MGC instances. Association - An association refers to a SCTP association. The association will provide the transport for the delivery of protocol data units for one or more interfaces. Backhaul - Refers to the transport of signalling 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 [9]. Fail-over - The capability to reroute signalling traffic as required to an alternate Application Server Process within an Application Server in the event of failure or unavailability of a currently used Application Server Process. Fail-back MAY apply upon the return to service of a previously unavailable Application Server Process. Host - The computing platform that the ASP process is running on. Morneault, et. al. Standards Track [Page 3] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 Interface - For the purposes of this document, an interface is a SS7 signalling link. Interface Identifier - The Interface Identifier identifies the physical interface at the SG for which the signalling messages are sent/received. The format of the Interface Identifier parameter can be text or integer, the values of which are assigned according to network operator policy. The values used are of local significance only, coordinated between the SG and ASP. Layer Management - Layer Management is a nodal function in an SG or ASP that handles the inputs and outputs between the M2UA layer and a local management entity. Link Key - The link key is a locally unique (between ASP and SG) value that identifies a registration request for a particular Signalling Data Link and Signalling Terminal pair. MTP - The Message Transfer Part of the SS7 protocol MTP2 - MTP Level 2, the signalling data link layer of SS7 MTP3 - MTP Level 3, the signalling network layer of SS7 MTP2-User - A protocol that uses the services of MTP Level 2 (i.e. MTP3). Network Byte Order: Most significant byte first, a.k.a Big Endian. Signalling Data Link - An SDL refers to a specific communications facility that connects two Signalling Link Terminals. Signalling Gateway (SG) - An SG is a signalling agent at the edge of the IP network. An SG appears to the SS7 as one or more Signalling Link Terminals that are connected to one or more Signalling Data Links in the SS7 network. An SG contains a set of one or more unique Signalling Gateway Processes, on which one or more is normally actively processing traffic. Where an SG contains more than one SGP, the SG is a logical entity. Signalling Gateway Process (SGP) - A process instance that uses M2UA to communicate to and from a Signalling Link Terminal. It serves as an active, backup or load-sharing process of a Signalling Gateway. Signalling Link Terminal (SLT) - Refers to the means of performing all of the functions defined at MTP level 2 regardless of their implementation [2,3]. Morneault, et. al. Standards Track [Page 4] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 Stream - A stream refers to an SCTP stream; a unidirectional 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 unordered delivery service. 1.3 M2UA Overview The framework architecture that has been defined for SCN signalling transport over IP [9] uses two components: a signalling common transport protocol and an adaptation module to support the services expected by a particular SCN signalling protocol from its underlying protocol layer. 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 [8] as the underlying reliable signalling common transport protocol. In a Signalling Gateway, it is expected that the SS7 MTP2-User signalling is transmitted and received from the PSTN over a standard SS7 network interface, using the SS7 Message Transfer Part Level 1 and Level 2 [2,3,4] to provide reliable transport of the MTP3-User signalling messages to and from an SS7 Signalling End Point (SEP) or Signalling Transfer Point (STP). The SG then provides an interworking of transport functions with the IP transport, in order to transfer the MTP2-User signalling messages to and from an Application Server Process where the peer MTP2-User protocol layer exists. Morneault, et. al. Standards Track [Page 5] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 1.3.1 Example - SG to MGC In a Signalling Gateway, it is expected that the SS7 signalling is received over a standard SS7 network termination, using the SS7 Message Transfer Part (MTP) to provide transport of SS7 signalling messages to and from an SS7 Signalling End Point (SEP) or SS7 Signalling Transfer Point (STP). In other words, the SG acts as a Signalling Link Terminal (SLT) [2,3]. The SG then provides an interworking of transport functions with IP Signalling Transport, in order to transport the MTP3 signalling messages to the MGC where the peer MTP3 protocol layer exists, as shown below: ****** 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 Signalling Endpoint IP - Internet Protocol SCTP - Stream Control Transmission Protocol (Reference [8]) 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) [8] as the underlying reliable common signalling 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, Morneault, et. al. Standards Track [Page 6] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 - network-level fault tolerance through the 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 ASP Fail-over Model and Terminology The M2UA layer supports ASP fail-over functions in order to support a high availability of call and transaction processing capability. All MTP2-User messages incoming to a SGP from the SS7 network are assigned to the unique Application Server, based on the Interface Identifier of the message. The M2UA layer supports a n+k redundancy model (active-standby, load sharing, broadcast) where n 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. 1.3.3 Client/Server Model It is recommended that the SGP 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 SGP to take on the role of server while the ASP is the client. In this case, ASPs SHOULD initiate the SCTP association to the SGP. The SCTP and 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. Morneault, et. al. Standards Track [Page 7] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 1.4.1 Support for MTP Level 2 / MTP Level 3 interface boundary M2UA supports a MTP Level 2 / MTP Level 3 interface boundary that enables a seamless, or as seamless as possible, operation of the MTP2-User peers in the SS7 and IP domains. An example of the primitives that need to be supported can be found in [10]. 1.4.2 Support for communication between Layer Management modules on SG and MGC The M2UA layer needs to provide some messages that will facilitate communication between Layer Management modules on the SG and MGC. To facilitate reporting of errors that arise because of the backhauling MTP Level 3 scenario, the following primitive is defined: M-ERROR The M-ERROR message is used to indicate an error with a received M2UA message (e.g., an interface identifier value is not known to the SG). 1.4.3 Support for management of active associations between SG and MGC The M2UA layer on the SG keeps the state of the configured ASPs. A set of primitives between M2UA layer and the Layer Management are defined below to help the Layer Management manage the association(s) between the SG and the MGC. The M2UA layer can be instructed by the Layer Management to establish a SCTP association to a peer M2UA node. This procedure can be achieved using the M-SCTP ESTABLISH primitive. M-SCTP_ESTABLISH The M-SCTP_ESTABLISH primitive is used to request, indicate and confirm the establishment of a SCTP association to a peer M2UA node. M-SCTP_RELEASE The M-SCTP_RELEASE primitives are used to request, indicate, and confirm the release of a SCTP association to a peer M2UA node. The M2UA layer MAY also need to inform the status of the SCTP association(s) to the Layer Management. This can be achieved using the following primitive. M-SCTP_STATUS The M-SCTP_STATUS primitive is used to request and indicate the status of underlying SCTP association(s). Morneault, et. al. Standards Track [Page 8] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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 the 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 an Interface ID to a physical interface on the Signalling Gateway. A physical interface would be a V.35 line, T1 line/time slot, E1 line/time slot, etc. The M2UA layer MUST also maintain a map of the Interface Identifier to SCTP association and to the related stream within the association. The SGP 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 fail-over of one ASP to another. Therefore, the SGP MUST maintain the states of AS/ASP and reference them during the routing of any messages to an AS/ASP. Note that only one SGP SHOULD provide Signalling Link Terminal services to an SS7 link. Therefore, within an SG, an Application Server SHOULD be active for only one SGP at any given point in time. Morneault, et. al. Standards Track [Page 9] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 An example of the logical view of the relationship between an SS7 link, Interface Identifier, AS and ASP in an SGP is shown below: /-------------------------------------------------+ / /----------------------------------------------|--+ / / v | / / +----+ act+-----+ +-------+ -+--+|-+- SS7 link1-------->|IID |-+ +-->| ASP |-->| Assoc | v / +----+ | +----+ | +-----+ +-------+ -+--+--+- / +->| AS |--+ Streams / +----+ | +----+ stb+-----+ SS7 link2-------->|IID |-+ | ASP | +----+ +-----+ where IID = Interface Identifier A SGP MAY support more than one AS. An AS MAY support more than one Interface Identifier. 1.5.2 Support for the management of SCTP associations between the SGPs and ASPs The M2UA layer at the SG maintains the availability state of all configured ASPs, in order to manage the SCTP associations and the traffic between the SG and ASPs. As well, the active/inactive state of remote ASP(s) are also maintained. The Active ASP(s) are the one(s) currently receiving traffic from the SG. The M2UA layer MAY be instructed by local management to establish an SCTP association to a peer M2UA node. This can be achieved using the M-SCTP_ESTABLISH primitive to request, indicate and confirm the establishment of an SCTP association with a peer M2UA node. The M2UA layer MAY also need to inform local management of the status of the underlying SCTP associations using the M-SCTP_STATUS request and the indication primitive. For example, the M2UA MAY inform local management of the reason for the release of an SCTP association, determined either locally within the M2UA layer or by a primitive from the SCTP. Also the M2UA layer may need to inform the local management of the change in status of an ASP or AS. This may be achieved using the M- ASP STATUS request or M-AS_STATUS request primitives. Morneault, et. al. Standards Track [Page 10] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 1.5.3 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 the reception of peer-to-peer messages (ASPM messages as described in Section 3.3.2) or the reception of indications from the local SCTP association. The ASP state transition procedures are described in Section 4.3.1. At a SGP, an Application Server list MAY contain active and inactive ASPs to support ASP fail-over procedures. When, for example, both a primary and a backup ASP are available, the 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 SGP to reflect the active Application Server Process. Also the M2UA layer MAY need to inform the local management of the change in status of an ASP or AS. This can be achieved using the M- ASP_STATUS or M-AS_STATUS primitives. 1.5.4 SCTP Specifics 1.5.4.1 SCTP Stream Management SCTP allows a user specified number of streams to be opened during initialization of the association. It is the responsibility of the M2UA layer to ensure proper management of these streams. Because of the unidirectional nature of streams, a M2UA layer is not aware of the stream information from its peer M2UA layer. For this reason, 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, thereby, improving the overall performance and reliability of the signalling elements. A separate SCTP stream can be used for each SS7 link. Or, an implementation may choose to split the SS7 link across several streams based on SLS. This method may be of particular interest for high speed SS7 links (MTP3b) since high speed links have a 24-bit sequence number and the stream sequence number is 16-bits. SCTP Stream '0' SHOULD NOT be used for MTP2 User Adaptation (MAUP) messages (see Section 3) since stream '0' SHOULD only be used for ASP Management (ASPM) messages (see Section 4.3.3). Morneault, et. al. Standards Track [Page 11] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 1.5.5 Seamless SS7 Network Management Interworking The M2UA layer on the SGP SHOULD pass an indication of unavailability of the M2UA-User (MTP3) to the local Layer Management, if the currently active ASP moves from the ACTIVE state. The actions taken by M2UA on the SGP with regards to MTP Level 2 should be in accordance with the appropriate MTP specifications. 1.5.6 Flow Control / Congestion It is possible for the M2UA layer to be informed of the IP network congestion onset and abatement by means of an implementation dependent function (i.e. an indication from the SCTP). The handling of this congestion indication by M2UA is implementation dependent. However, the actions taken by the SG should be in accordance with the appropriate MTP specification and should enable SS7 functionality (e.g. flow control) to be correctly maintained. 1.5.7 Audit of SS7 Link State After a fail-over 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 SGP would respond to the audit request with information regarding the current state of the SS7 link (i.e. in-service, out-of-service, congestion state, LPO/RPO state). 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 Morneault, et. al. Standards Track [Page 12] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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 [8] Section 10. 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 SGP. M-SCTP_ESTABLISH confirm Direction: M2UA -> LM Purpose: ASP confirms to LM that it has established an SCTP association with an SGP. M-SCTP_ESTABLISH indication Direction: M2UA -> LM Purpose: SGP 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 SGP. M-SCTP_RELEASE confirm Direction: M2UA -> LM Purpose: ASP confirms to LM that it has released SCTP association with SGP. M-SCTP_RELEASE indication Direction: M2UA -> LM Purpose: SGP informs LM that ASP has released an SCTP association. M-SCTP_RESTART indication Direction: M2UA -> LM Purpose: M2UA informs LM that a SCTP Restart indication has been received. M-SCTP_STATUS request Direction: LM -> M2UA Purpose: LM requests M2UA to report status of SCTP association. M-SCTP_STATUS indication Direction: M2UA -> LM Purpose: M2UA reports status of SCTP association. Morneault, et. al. Standards Track [Page 13] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 M-ASP_STATUS request Direction: LM -> M2UA Purpose: LM requests SGP to report status of remote ASP. M-ASP_STATUS indication Direction: M2UA -> LM Purpose: SGP 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 SGP 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 SGP. M-ASP_UP confirm Direction: M2UA -> LM Purpose: ASP reports that it has received an ASP UP Acknowledgment message from the SGP. M-ASP_DOWN request Direction: LM -> M2UA Purpose: LM requests ASP to stop its operation and send an ASP DOWN message to the SGP. M-ASP_DOWN confirm Direction: M2UA -> LM Purpose: ASP reports that is has received an ASP DOWN Acknowledgment message from the SGP. Morneault, et. al. Standards Track [Page 14] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 M-ASP_ACTIVE request Direction: LM -> M2UA Purpose: LM requests ASP to send an ASP ACTIVE message to the SGP. M-ASP_ACTIVE confirm Direction: M2UA -> LM Purpose: ASP reports that is has received an ASP ACTIVE Acknowledgment message from the SGP. M-ASP_INACTIVE request Direction: LM -> M2UA Purpose: LM requests ASP to send an ASP INACTIVE message to the SGP. M-ASP_INACTIVE confirm Direction: M2UA -> LM Purpose: ASP reports that is has received an ASP INACTIVE Acknowledgment message from the SGP. M-LINK_KEY_REG Request Direction: LM -> M2UA Purpose: LM requests ASP to register Link Key with SG by sending REG REQ message. M-LINK_KEY_REG Confirm Direction: M2UA -> LM Purpose: ASP reports to LM that it has successfully received a REG RSP message from SG. M-LINK_KEY_REG Indication Direction: M2UA -> LM Purpose: SG reports to LM that it has successfully processed an incoming REG REQ message from ASP. M-LINK_KEY_DEREG Request Direction: LM -> M2UA Purpose: LM requests ASP to de-register Link Key with SG by sending DEREG REQ message. M-LINK_KEY_DEREG Confirm Direction: M2UA -> LM Purpose: ASP reports to LM that it has successfully received a DEREG RSP message from SG. M-LINK_KEY_DEREG Indication Direction: M2UA -> LM Purpose: SG reports to LM that it has successfully processed an incoming DEREG REQ message from ASP. Morneault, et. al. Standards Track [Page 15] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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. 3.1 Common Message Header The protocol messages for MTP2-User Adaptation require a message structure that contains a version, message class, message type, message length, and message contents. This message header is common among all signalling protocol adaptation layers: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Version | Spare | Message Class | Message Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2 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 contains the version of the M2UA adaptation layer. The supported versions are: Value Version ----- ------- 1 Release 1.0 3.1.2 Spare The Spare field is 8-bits. It SHOULD be set to all '0's by the sender and ignored by the receiver. Morneault, et. al. Standards Track [Page 16] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 3.1.3 Message Class 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 Transport (QPTM) Messages [IUA] 6 MTP2 User Adaptation (MAUP) Messages [M2UA] 7 Connectionless Messages [SUA] 8 Connection-Oriented Messages [SUA] 9 Routing Key Management (RKM) Messages (M3UA) 10 Interface Identifier Management (IIM) Messages (M2UA) 11 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined Message Class extensions 3.1.4 Message Type The following List contains the Message Types for the valid Message Classes: MTP2 User Adaptation (MAUP) Messages 0 Reserved 1 Data 2 Establish Request 3 Establish Confirm 4 Release Request 5 Release Confirm 6 Release Indication 7 State Request 8 State Confirm 9 State Indication 10 Data Retrieval Request 11 Data Retrieval Confirm 12 Data Retrieval Indication 13 Data Retrieval Complete Indication 14 Congestion Indication 15 Data Acknowledge 16 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined MAUP extensions Morneault, et. al. Standards Track [Page 17] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 Application Server Process State Maintenance (ASPSM) messages 0 Reserved 1 ASP Up (UP) 2 ASP Down (DOWN) 3 Heartbeat (BEAT) 4 ASP Up Ack (UP ACK) 5 ASP Down Ack (DOWN ACK) 6 Heartbeat Ack (BEAT ACK) 7 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined ASPSM extensions Application Server Process Traffic Maintenance (ASPTM) messages 0 Reserved 1 ASP Active (ACTIVE) 2 ASP Inactive (INACTIVE) 3 ASP Active Ack (ACTIVE ACK) 4 ASP Inactive Ack (INACTIVE ACK) 5 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined ASPTM extensions Management (MGMT) Messages 0 Error (ERR) 1 Notify (NTFY) 2 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined MGMT extensions Interface Identifier Management (IIM) Messages 0 Reserved 1 Registration Request (REG REQ) 2 Registration Response (REG RSP) 3 Deregistration Request (DEREG REQ) 4 Deregistration Response (DEREG RSP) 5 to 127 Reserved by the IETF 128 to 255 Reserved for IETF-Defined IIM extensions 3.1.5 Message Length The Message Length defines the length of the message in octets, including the header. The Message Length MUST include parameter padding bytes, if any. The Message Length MUST NOT be longer than a MTP3 message [2,3,4,5] plus the length of the common and M2UA message headers. Morneault, et. al. Standards Track [Page 18] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 3.1.6 Variable-Length Parameter Format M2UA messages consist of a Common Header followed by zero or more variable-length parameters, as defined by the message type. The variable-length parameters contained in a message are defined in a Tag-Length-Value format as shown below. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Parameter Tag | Parameter Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ \ \ / Parameter Value / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Mandatory parameters MUST be placed before optional parameters in a message. Parameter Tag: 16 bits (unsigned integer) The Type field is a 16 bit identifier of the type of parameter. It takes a value of 0 to 65534. The common parameters used by the adaptation layers are in the range of 0x00 to 0xff. The M2UA specific parameters have Tags in the range 0x300 to 0x3ff. Morneault, et. al. Standards Track [Page 19] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 The common parameter tags (used by all User Adaptation layers) that M2UA uses are defined below: Parameter Value Parameter Name --------------- -------------- 0 (0x00) Reserved 1 (0x01) Interface Identifier (Integer) 2 (0x02) Unused 3 (0x03) Interface Identifier (Text) 4 (0x04) Info String 5 (0x05) Unused 6 (0x06) Unused 7 (0x07) Diagnostic Information 8 (0x08) Interface Identifier (Integer Range) 9 (0x09) Heartbeat Data 10 (0x0a) Unused 11 (0x0b) Traffic Mode Type 12 (0x0c) Error Code 13 (0x0d) Status Type/Information 14 (0x0e) Unused 15 (0x0f) Unused 16 (0x10) Unused 17 (0x11) ASP Identifier 18 (0x12) Unused 19 (0x13) Correlation Id 18-255 Reserved Morneault, et. al. Standards Track [Page 20] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 The M2UA specific parameter Tags defined are as follows: Parameter Value Parameter Name --------------- -------------- 768 (0x0300) Protocol Data 1 769 (0x0301) Protocol Data 2 (TTC) 770 (0x0302) State Request 771 (0x0303) State Event 772 (0x0304) Congestion Status 773 (0x0305) Discard Status 774 (0x0306) Action 775 (0x0307) Sequence Number 776 (0x0308) Retrieval Result 777 (0x0309) Link Key 778 (0x030a) Local-LK-Identifier 779 (0x030b) Signalling Data Terminal (SDT) Identifier 780 (0x030c) Signalling Data Link (SDL) Identifier 781 (0x030d) Registration Result 782 (0x030e) Registration Status 783 (0x030f) De-Registration Result 784 (0x0310) De-Registration Status 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. Thus, a parameter with a zero-length Parameter Value field would have a Length field of 4. 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 MUST NOT pad with more than 3 bytes. The receiver MUST ignore the padding bytes. Morneault, et. al. Standards Track [Page 21] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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 signalling 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 3 M2UA Message Header (Integer-based Interface Identifier) The Tag value for the 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 4 M2UA Message Header (Text-based Interface Identifier) The Tag value for the Text-based Interface Identifier is 0x3. The encoding of the Identifier is ANSI X3.4-1986 [7]. The maximum string length of the text-based Interface Identifier is 255 octets. The tag length is equal to the string length of the Interface Identifier name plus four bytes for the Tag and Length fields. Morneault, et. al. Standards Track [Page 22] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 3.3 M2UA Messages The following section defines the messages and parameter contents. The M2UA messages will use the common message header (Figure 2) and the M2UA message header (Figure 3 and Figure 4). 3.3.1 MTP2 User Adaptation Messages 3.3.1.1 Data The Data message contains an SS7 MTP2-User Protocol Data Unit (PDU). The Data message contains the following parameter: Protocol Data (mandatory) Correlation Id (optional) 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 (0x300) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / \ \ Protocol Data / / \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x13) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Correlation Id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Protocol Data field contains the MTP2-User application message in network byte order starting with the Signalling Information Octet (SIO). The Correlation Id parameter uniquely identifies the MSU carried in the Protocol Data within an AS. This Correlation Id parameter is assigned by the sending M2UA. The purpose of the Correlation Id is to permit the newly active ASP to synchronize its processing of the traffic in each ordered stream with other ASPs in the broadcast group. Morneault, et. al. Standards Track [Page 23] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 The format for a Data Message with TTC PDU parameters is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x301) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / \ \ TTC Protocol Data / / \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x13) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Correlation Id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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. The length of the Protocol Data and TTC Protocol Data MUST NOT exceed the length of a MTP2-User application message [2,3,5]. 3.3.1.2 Data Acknowledge Message The Data Acknowledge message contains the Correlation Id of the Data message that the sending M2UA is acknowledging as successfully processed to the peer M2UA. The Data Acknowledge message contains the following parameter: Correlation Id Mandatory The following format MUST be used for the Data Ack Message: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x13) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Correlation Id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Correlation Id parameter of the Data message and the Data Ack message provide a mechanism, for those SG implementations capable of taking advantage of them, to obtain an acknowledgment that the MSU has been transferred to the M2UA peer before acknowledging the MSU to Morneault, et. al. Standards Track [Page 24] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 the SS7 peer, removing the risk of losing messages due to association failure or SCTP congestion. The Data Ack message MUST be sent if a Correlation Id parameter is received from the peer. Otherwise, the Data Ack message MUST NOT be sent. If the Data Acknowledge is not sent for Correlation Id(s) or is sent with Invalid Correlation Id(s), the SS7 link will eventually fail due to lack of MTP Level 2 acknowledgments of the SS7 peer's MSUs. 3.3.1.3 Establish (Request, Confirmation) The Establish Request message is used to establish the SS7 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 SGP MAY already have the SS7 link established at its layer. If so, upon receipt of an Establish Request, the SGP 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 resend 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 a periodic basis until the desired state is achieved or some other action is taken (notify the Management Layer). The mode (Normal or Emergency) for bringing the SS7 link in service is defaulted to Normal. The State Request (described in Section 3.3.1.5 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 Signalling Gateway Process. The SGP sends a State Confirm to the MGC if the action has been successfully completed. The State Confirm reflects that state value received in the State Request message. Morneault, et. al. Standards Track [Page 25] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 The State Request message contains the following parameter: State (mandatory) 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x302) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 STATUS_EMER_CLEAR 0x3 Request normal alignment (cancel emergency) STATUS_FLUSH_BUFFERS 0x4 Flush or clear receive, transmit and retransmit queues STATUS_CONTINUE 0x5 Continue or Resume STATUS_CLEAR_RTB 0x6 Clear the retransmit queue STATUS_AUDIT 0x7 Audit state of link STATUS_CONG_CLEAR 0x8 Congestion cleared STATUS_CONG_ACCEPT 0x9 Congestion accept STATUS_CONG_DISCARD 0xa Congestion discard 3.3.1.6 State Confirm The State Confirm message will be sent by the SGP in response to a State Request from the MGC. The State Confirm reflects that state value received in the State Request message. The State Confirm message contains the following parameter: State (mandatory) 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x302) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | State | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Morneault, et. al. Standards Track [Page 26] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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 STATUS_EMER_CLEAR 0x3 Request normal alignment (cancel emergency) STATUS_FLUSH_BUFFERS 0x4 Flush or clear receive, transmit and retransmit queues STATUS_CONTINUE 0x5 Continue or Resume STATUS_CLEAR_RTB 0x6 Clear the retransmit queue STATUS_AUDIT 0x7 Audit state of link STATUS_CONG_CLEAR 0x8 Congestion cleared STATUS_CONG_ACCEPT 0x9 Congestion accept STATUS_CONG_DISCARD 0xa Congestion discard 3.3.1.7 State Indication The MTP2 State Indication message can be sent from a SGP to an ASP to indicate a condition on a SS7 link. The State Indication message contains the following parameter: Event (mandatory) 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x303) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Event | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The valid values for Event are shown in the following table. Define Value Description EVENT_RPO_ENTER 0x1 Remote entered processor outage EVENT_RPO_EXIT 0x2 Remote exited processor outage EVENT_LPO_ENTER 0x3 Link entered processor outage EVENT_LPO_EXIT 0x4 Link exited processor outage Morneault, et. al. Standards Track [Page 27] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 3.3.1.8 Congestion Indication The Congestion Indication message can be sent from a Signalling Gateway Process to an ASP to indicate the congestion status and discard status of a SS7 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 SGP SHALL send a congestion indication message when it supports SS7 MTP2 variants that support multiple congestion levels. The SGP 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 SGP 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. The Congestion Indication message contains the following parameters: Congestion Status (mandatory) Discard Status (optional) 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x304) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Congestion Status | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x305) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 Morneault, et. al. Standards Track [Page 28] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 For SS7 networks that do not support multiple levels of congestion, only the LEVEL_NONE and LEVEL_3 values will be used. For SS7 networks that support multiple levels of congestion, it is possible for all values to be used. Refer to [2], [3] and [12] for more details on the Congestion and Discard Status of SS7 signalling links. 3.3.1.9 Retrieval Request The MTP2 Retrieval Request message is used during the MTP Level 3 changeover procedure to request the BSN, to retrieve PDUs from the transmit and retransmit queues or to flush PDUs from the retransmit queue. Examples of the use of Retrieval Request for SS7 Link Changeover are provided in Section 5.3.6. The Retrieval Request message contains the following parameters: Action (mandatory) Sequence Number (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 (0x306) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Action | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x307) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The valid values for Action are shown in the following table. Define Value Description ACTION_RTRV_BSN 0x1 Retrieve the backward sequence number ACTION_RTRV_MSGS 0x2 Retrieve the PDUs from the transmit and retransmit queues In the Retrieval Request message, the Sequence Number field SHOULD NOT be present if the Action field is ACTION_RTRV_BSN. The Sequence Number field contains the Forward Sequence Number (FSN) of the far end if the Action is ACTION_RTRV_MSGS. Morneault, et. al. Standards Track [Page 29] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 3.3.1.10 Retrieval Confirm The MTP2 Retrieval Confirm message is sent by the Signalling Gateway in response to a Retrieval Request message. Examples of the use of the Retrieval Confirm for SS7 Link Changeover are provided in Section 5.3.6. The Retrieval Confirm message contains the following parameters: Action (mandatory) Result (mandatory) Sequence Number (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 (0x306) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Action | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x308) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Result | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x307) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The valid values for Action are the same as in Retrieval Request. The values for Result are shown below: Define Value Description RESULT_SUCCESS 0x0 Action successful RESULT_FAILURE 0x1 Action failed When the Signalling Gateway Process sends a Retrieval Confirm to a Retrieval Request, it echos the Action field. If the Action was ACTION_RTRV_BSN and the SGP successfully retrieved the BSN, the SGP will put the Backward Sequence Number (BSN) in the Sequence Number field and will indicate a success in the Result field. If the BSN could not be retrieved, the Sequence Number field will not be included and the Result field will indicate failure. Morneault, et. al. Standards Track [Page 30] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 For a Retrieval Confirm with Action of ACTION_RTRV_MSGS, the value of the Result field will indicate success or failure. A failure means that the buffers could not be retrieved. The Sequence Number field is not used with ACTION_RTRV_MSGS. 3.3.1.11 Retrieval Indication The Retrieval Indication message is sent by the Signalling Gateway with a PDU from the transmit or retransmit queue. The Retrieval Indication message does not contain the Action or Sequence Number fields, just a MTP3 Protocol Data Unit (PDU) from the transmit or retransmit queue. Examples of the use of the Retrieval Indication for SS7 Link Changeover are provided in Section 5.3.6. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x300) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / \ \ Protocol Data / / \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ For TTC Data messages, the following parameter will be used to indicate a TTC PDU which starts at LI. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x301) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / \ \ TTC Protocol Data / / \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The M2UA implementation MAY consider the use of the bundling feature of SCTP for Retrieval Indication messages. 3.3.1.12 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 retrieval is complete. In addition, it MAY contain a PDU (which MUST be the last PDU) from the transmit or retransmit queue. Morneault, et. al. Standards Track [Page 31] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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. The ASPUP message contains the following parameters ASP Identifier (optional) Info String (optional) Note: The ASP Identifier MUST be used where the SGP cannot identify the ASP by pre-configured address/port number information (e.g., where an ASP is resident on a Host using dynamic address/port number assignment). 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 (0x11) | Length = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ASP Identifier* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x4) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / \ \ INFO String* / / \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The optional ASP Identifier parameter would contain a unique value that is locally significant among the ASPs that support an AS. The SGP should save the ASP Identifier to be used, if necessary, with the Notify message (see Section 3.3.3.2). The optional INFO String parameter can carry any meaningful UTF-8 [6] character string along with the message. Length of the INFO String parameter is from 0 to 255 octets. No procedures are presently identified for its use but the INFO String MAY be used for debugging purposes. Morneault, et. al. Standards Track [Page 32] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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 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 (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). Morneault, et. al. Standards Track [Page 33] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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: 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 (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). 3.3.2.5 Heartbeat (BEAT) The Heartbeat message is optionally used to ensure that the M2UA peers are still available to each other. The BEAT message contains the following parameter: Heartbeat Data Optional The format for the BEAT message is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag = 0x0009 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / Heartbeat Data / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The sending node defines the Heartbeat Data field contents. It may include a Heartbeat Sequence Number and/or time stamp, or other implementation specific details. Morneault, et. al. Standards Track [Page 34] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 The receiver of a Heartbeat message does not process this field as it is only of significance to the sender. The receiver echoes the content of the Heartbeat Data in a BEAT ACK message. 3.3.2.6 Heartbeat Ack (BEAT ACK) The Heartbeat ACK message is sent in response to a BEAT message. A peer MUST send a BEAT ACK in response to a BEAT message. It includes all the parameters of the received Heartbeat message, without any change. The BEAT ACK message contains the following parameter: Heartbeat Data Optional The format for the BEAT 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 = 0x0009 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / Heartbeat Data / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The sending node defines the Heartbeat Data field contents. It may include a Heartbeat Sequence Number and/or time stamp, or other implementation specific details. The receiver of a Heartbeat message does not process this field as it is only of significance to the sender. The receiver echoes the content of the Heartbeat Data in a BEAT ACK message. 3.3.2.7 ASP Active (ASPAC) The ASPAC message is sent by an ASP to indicate to an SGP that it is Active and ready to be used. The ASPAC message contains the following parameters: Traffic Mode Type (optional) Interface Identifier (optional) - Combination of integer and integer ranges, OR - string (text formatted) INFO String (optional) Morneault, et. al. Standards Track [Page 35] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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 = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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* / / \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Morneault, et. al. Standards Track [Page 36] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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 Override 0x2 Load-share 0x3 Broadcast Within a particular AS, only one Traffic Mode Type can be used. The Override value indicates that the ASP is operating in Override mode, where the ASP takes over all traffic in an Application Server (i.e., primary/backup operation), over-riding any currently active ASPs in the AS. In Load-share mode, the ASP will share in the traffic distribution with any other currently active ASPs. In Broadcast mode, all of the Active ASPs receive all message traffic in the Application Server. Morneault, et. al. Standards Track [Page 37] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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 for an AS 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 SGP that receives an ASPAC with an incorrect or unsupported Traffic Mode Type for a particular Interface Identifier will respond with an Error Message (Cause: Unsupported Traffic Handling Mode). The format and description of the optional Info String parameter is the same as for the ASP UP message (See Section 3.3.2.1). 3.3.2.8 ASP Active Ack The ASP Active (ASPAC) Ack message is used to acknowledge an ASP Active message received from a remote M2UA peer. The ASPAC Ack message contains the following parameters: Traffic Mode Type (optional) Interface Identifier (optional) - Combination of integer and integer ranges, OR - string (text formatted) INFO String (optional) Morneault, et. al. Standards Track [Page 38] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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 = 8 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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* / / \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Morneault, et. al. Standards Track [Page 39] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 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 optional Interface Identifier parameter is the same as for the ASP Active 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). 3.3.2.9 ASP Inactive (ASPIA) The ASP Inactive (ASPIA) message is sent by an ASP to indicate to an SGP that it is no longer an active ASP to be used from within a list of ASPs. The SGP will respond with an ASPIA Ack message and either discard incoming messages or buffer for a timed period and then discard. Morneault, et. al. Standards Track [Page 40] RFC 3331 SS7 MTP2 User Adaptation Layer September 2002 The ASPIA message contains the following parameters: Interface Identifiers (optional) - Combination of integer and integer ranges, OR - string (text formatted) INFO String (optional) The format for the ASP Inactive message parameters using Integer formatted Interface Identifiers is as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x1=integer) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / \ \ Interface Identifiers* / / \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag (0x8=integer range) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop1* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Start2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Identifier Stop2* | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . .