1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-1000111.2005 (R2015) SIGNALLING SYSTEM NUMBER 7 (SS7) MESSAGE TRANSFER PART (MTP) As a leading technology and solutions development organization, ATIS brings together the top global ICT companies to advance the industrys most-pressing business
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11、, “signal units“ of variable lengths are transferred, including control information for proper operation. Chapter T1.111.4 describes the functions and procedures for, and relating to, the transfer of messages between signalling points; these signalling network management functions ensure a reliable
12、transfer of signalling messages, according to the requirements specified in chapter T1.111.6. Chapter T1.111.5 describes aspects that are pertinent to, and should be considered in, the design of national and international signalling networks. Chapter T1.111.6 describes the signalling performance req
13、uirements of the Message Transfer Part; the signalling performance is the capability of the Message Transfer Part to transfer messages of variable lengths for different users in a defined manner. Chapter T1.111.7 describes means and procedures for the testing and maintenance of the signalling networ
14、k in order to realize the performance requirements for the Message Transfer Part, as identified in Chapter T1.111.6. Chapter T1.111.8 describes aspects that are pertinent to the numbering scheme of signalling codes for SS7 networks in the United States. ATIS-1000111.2005 ii FOREWORD The information
15、contained in this Foreword is not part of this American National Standard (ANS) and has not been processed in accordance with ANSIs requirements for an ANS. As such, this Foreword may contain material that has not been subjected to public review or a consensus process. In addition, it does not conta
16、in requirements necessary for conformance to the standard. This document is entitled Signalling System Number 7 (SS7) Message Transfer Part (MTP). It is based on ANSI T1.111-2001, and is intended to be compatible with ITU-T Recommendations Q.701 through Q.708, issued by the ITU-T Study Group XI (Vol
17、. VI Fascicle VI.8) for international use. A change bar on the right margin indicates a change from the 2001 issue of this American National Standard. These change bars are advisory only, and reflect the editors views of which textual changes constitute significant technical changes. Because of the
18、differences in style and content between this standard and the ITU-T Recommendations, it is not possible to indicate differences using margin marks. This standard contains the following eight chapters: T1.111.1, Functional Description of the Message Transfer Part (MTP). T1.111.2, Signalling Data Lin
19、k. T1.111.3, Signalling Link. T1.111.4, Signalling Network Functions and Messages. T1.111.5, Signalling Network Structure. T1.111.6, Message Transfer Part Signalling Performance. T1.111.7, Testing and Maintenance. T1.111.8, Numbering of Signalling Point Codes. (See below Note.) This standard is inte
20、nded for use in conjunction with T1.110-1999,Signalling system number 7 (SS7) General information, , which includes an overview of SS7, a glossary, and a chapter on abbreviations. The following are the key differences between T1.111-2001 and T1.111-2005: Addition of an extension mechanism for the Se
21、rvice Indicator (SI) field; and Update to the signalling point code assignment guidelines to assign point codes for internal CCS network/group use by any carrier. Information contained in a normative annex in these specifications is considered part of this standard. Information contained in an infor
22、mative annex in these specifications is not considered part of this standard but is rather auxiliary to the standard. Similarly, footnotes are not officially part of this standard. Caution should be exercised in using the Specification and Description Language (SDL) diagrams to interpret the standar
23、d since they may not fully align with the text. Please note that in case of any conflict between the text and the SDL diagrams, the text always takes precedence. NOTE - Chapter T1.111.8, Numbering of Signalling Points Codes: The document entitled Numbering of Signalling Points Codes - approved by th
24、e American National Standard Institute (ANSI) as T1.111a-2002 - is superseded by this document, T1.111-2005, Signalling System Number 7 (SS7) Message Transfer Part (MTP). This standard is intended for use in conjunction with American National Standard for Telecommunications Signalling System Number
25、7 (SS7) General information, T1.110-1999, which includes an overview of SS7, a glossary, and a chapter on abbreviations. ATIS-1000111.2005 iii Future control of this document will reside with PTSC. This control of additions to the specification, such as protocol evolution, new applications, and oper
26、ational requirements, will permit compatibility among U.S. networks. Such additions will be incorporated in an orderly manner with due consideration to the ITU-T layered model principles, conventions, and functional boundaries. Suggestions for improvement of this standard will be welcome. These shou
27、ld be sent to the Alliance for Telecommunications Industry Solutions, PTSC Secretariat, 1200 G Street, NW, Suite 500, Washington DC 20005. The Alliance for Telecommunication Industry Solutions (ATIS) serves the public through improved understanding between carriers, customers, and manufacturers. The
28、 Packet Technologies and Systems Committee (PTSC) - formerly T1S1 - develops and recommends standards and technical reports related to services, architectures, and signaling, in addition to related subjects under consideration in other North American and international standards bodies. PTSC coordina
29、tes and develops standards and technical reports relevant to telecommunications networks in the U.S., reviews and prepares contributions on such matters for submission to U.S. ITU-T and U.S. ITU-R Study Groups or other standards organizations, and reviews for acceptability or per contra the position
30、s of other countries in related standards development and takes or recommends appropriate actions. B. Hall, PTSC Chair J. Zebarth, PTSC Vice-Chair S. Carioti, ATIS Disciplines S. Barclay, ATIS Secretariat C. Underkoffler, ATIS Chief Editor R. Singh, PTSC Technical Editor Organization Represented Nam
31、e of Representative AcmePacket Kevin Klett Alcatel USA Inc. Ken Biholar AT 2. Flag imitation prevention by bit stuffing; 3. Error detection by means of check bits included in each signal unit; 4. Error correction by retransmission and signal unit sequence control by means of explicit sequence number
32、s in each signal unit and explicit continuous acknowledgments; and 5. Signalling link failure detection by means of signal unit error rate monitoring and signalling link recovery by means of special procedures. The detailed requirements for signalling link functions are given in Chapter T1.111.3. 2.
33、2.3A Signalling ATM Adaptation Layer (SAAL) and ATM Protocol Architecture 2.2.3A.1 Physical Layer The physical layer provides a means for ATM cells to be transmitted on a transport facility. At this time, SONET, DS1, and DS3 have been specified as physical layer methods for transmitting ATM cells. T
34、he physical transmission rates that have been specified are 51.840 Mbit/s, 155.520 Mbit/s, 622.080 Mbit/s, 2.48832 Gbit/s, 1.544 Mbit/s and 44.736 Mbit/s. The interface specifications of the SONET layer and DS3 are provided in T1.640-2001 (R2006). The interface specifications of the DS1 are provided
35、 in T1.646-2003. 2.2.3A.2 ATM Layer ATM is the transfer mode solution for implementing a B-ISDN. ATM provides high efficiency and flexibility because it provides “virtual channels” instead of dedicated physical channels, allowing better use of the physical resources with high performance capabilitie
36、s (low latency and high capacity). For signalling, the virtual channel connection constitutes a signalling link and can operate at a rate of 64 kbit/s or higher. ATM also allows sharing of Operations and Maintenance (OAM) across multiple services, provides variable information transfer rates, and ca
37、n support versatile call and connection structures. The multiplexed information flow is organized into fixed size cells. The protocol specification of the ATM layer is provided in T1.627-1993 (R2004). T1.111.1-3 ATIS-1000111.2005 Chapter T1.111.1 2.2.3A.3 SAAL The ATM Adaptation Layer (AAL) is defin
38、ed to enhance the services provided by the ATM layer to support the functions required by the next higher layer. One particular type of AAL service is the Signalling AAL (SAAL), which comprises AAL functions necessary to support signalling. The SAAL consists of the AAL Common Part (CP) type 5, the S
39、ervice Specific Connection Oriented Protocol (SSCOP), the Service Specific Coordination Function (SSCF), and the SAAL Layer Management. The SAAL at the Network Node Interface (NNI) provides signalling link functions for the transfer of signalling messages over one individual signalling data link. Th
40、e SAAL functions provide a signalling link for reliable transfer of signalling messages between two signalling points. A signalling message delivered by the higher levels is transferred over the signalling link in variable length protocol data units (PDUs). The overview to SAAL is provided in T1.636
41、-1999 (R2005). 2.2.3A.3.1 Common Part (CP) Several AAL CPs have been identified in T1.635.1999 (R2005); one is known as AAL type 5. The purpose of the type 5 CP is to support those capabilities necessary to meet the upper layer data transfer needs while using the service of the ATM layer. The protoc
42、ol provides the transport of variable length frames (1 to 65535 octets in length) with error detection. The frame is padded to align the resulting protocol data unit to fill an integral number of ATM cells. A CRC-32 is used to detect errors and the length field is used to extract the frame. The prot
43、ocol specification of the type 5 CP is provided in T1.636-1999 (R2005). 2.2.3A.3.2 Service Specific Connection Oriented Protocol (SSCOP) SSCOP is a connection oriented protocol with error recovery providing a generic reliable data transfer service for different AAL interfaces defined by the SSCF. Tw
44、o SSCFs have been defined for signalling: the signalling SSCF at the User Network Interface (UNI), and the signalling SSCF at the Network Node Interface (NNI). SSCOP utilizes the service of the AAL Type 5 CP, which provides an unassured information transfer and a mechanism for detecting corruption o
45、f SSCOP PDUs. The protocol specification of the SSCOP is provided in T1.637-1999 (R2005). 2.2.3A.3.3 Service Specific Coordination Function (SSCF) at the NNI The function of the SSCF is to map the service of the SSCOP of the AAL to the requirements of MTP Level 3. The SSCF at the NNI also provides c
46、ommunication with the SAAL Layer Management for proper operation of signalling links. The protocol specification of the SSCF is provided in T1.645-1995 (R2008). T1.111.1-4 ATIS-1000111.2005 Chapter T1.111.1 2.2.3A.3.4 SAAL Layer Management The layer management functions at the NNI perform a coordina
47、tion function between the system management function and the SAAL. The functions of the layer management at the NNI include error processing, measurements and determination of link quality during proving and normal operation. The protocol specification of the SAAL Layer Management is provided in T1.
48、652-1996(R2006). 2.2.4 Signalling Network Functions (Level 3) Level 3, in principle, defines those transport functions and procedures that are common to, and independent of, the operation of individual signalling links. As illustrated in Figure 2/T1.111.1, these functions fall into two major categor
49、ies: 1. Signalling Message Handling Functions. These are functions that, at the actual transfer of a message, direct the message to the proper signalling link or higher level function. 2. Signalling Network Management Functions. These are functions that, on the basis of predetermined data and information about the status of the signalling network, control the current message routing and configuration of signalling network facilities. In the event of changes in the status, they also control reconfigurations and other actions to preserve or restor
