1、 ATIS-1000615.2014 Digital Subscriber Signalling System No. 1 (DSS1) Layer 3 Overview AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS As a leading technology and solutions development organization, ATIS brings together the top global ICT companies to advance the industrys most-pressing business pr
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5、, visit . AMERICAN NATIONAL STANDARD Approval of an American National Standard requires review by ANSI that the requirements for due process, consensus, and other criteria for approval have been met by the standards developer. Consensus is established when, in the judgment of the ANSI Board of Stand
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8、rds. The American National Standards Institute does not develop standards and will in no circumstances give an interpretation of any American National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the Americ
9、an National Standards Institute. Requests for interpretations should be addressed to the secretariat or sponsor whose name appears on the title page of this standard. CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time. The procedures of the American National Stan
10、dards Institute require that action be taken periodically to reaffirm, revise, or withdraw this standard. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute. Notice of Disclaimer and American Nati
11、onal Standard for telecommunications - ISDN primary rate - Customer installation metallic interfaces - Layer 1 specification, ANSI T1.408-1990. Layer 2 functions are described in American National Standard for telecommunications - Integrated services digital network - ISDN signalling specification f
12、or application at the user-network interface - Layer 2 specification, ATIS-1000602. The Layer 3 protocols provide: the means to establish, maintain, and terminate network connections across an ISDN between communicating entities; and procedures that may be used to invoke and control supplementary se
13、rvices. This standard describes the Layer 3 DSS1 functions and protocol in general terms. Details of the Layer 3 protocols are provided in the standards listed in clause 8. A glossary of Layer 3 terms is provided in clause 3. 2 Normative References The following standards contain provisions which, t
14、hrough reference in this text, constitute provisions of this American National Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this American National Standard are encouraged to investigate the possibil
15、ity of applying the most recent editions of the standards indicated below. ANSI T1.408-1990, Telecommunications - ISDN primary rate - Customer installation metallic interfaces - Layer 1 specification. 1 ATIS-1000615.2014 ATIS-0600601.1999(R2009), Integrated services digital network (ISDN) - basic ac
16、cess interface for use on metallic loops for application at the network side of NT, Layer 1 specification.1ATIS-1000602.1996(R2014), Integrated services digital network (ISDN) Data-Link Layer signaling specification for application at the user-network interface - Layer 2 specification.2ATIS-0600605.
17、1991(R2009), Telecommunications - Integrated services digital network (ISDN) - basic access interface for S and T reference points - Layer 1 specification.3ATIS-1000607.2000(R2009), Telecommunications - Integrated services digital network (ISDN) - Layer-3 signaling specification for circuit- switche
18、d bearer service for digital subscriber signaling system no. 1 (DSS1).4ITU-T Recommendation 1.320, ISDN protocol reference mode.5ITU-T Recommendation 1.412, ISDN user- network interfaces - Interface structures and capabilities.7ITU-T Recommendation 0.920, ISDN user- network interface data link layer
19、 - General aspects.7ITU-T Recommendation 0.921, ISDN user- network interface - Data link layer specification.73 Definitions These terms are common among the standards in the suite of Layer 3 DSS1 standards. 3.1 access 3.1.1 access connection: A connection (using either the 8-Channel or a logical lin
20、k on the D-Channel) established between the user equipment and a packet-mode handler function, over which packet-mode calls (incoming and outgoing) are established. 3.1.2 incoming access: The ability of a user to terminate data calls via an ISDN. 3.1.3 outgoing access: The ability of a user to origi
21、nate data calls via an ISDN. 3.2 access unit: A conceptual unit of an ISDN which provides interworking functions between the circuit-switched data transmission services of an ISDN and the packet- switched data transmission services of a Packet Switched Public Data Network (PSPDN) for both incoming a
22、nd outgoing calls. 3.3 channel: A channel represents a specified portion of the information-carrying capacity of an interface. 3.3.1 B-channel: A 64-kbit/s channel ac- companied by timing, intended to carry a wide variety of user information streams, such as voice encoded at 64 kbit/s, data informat
23、ion at bit rates less than or equal to 1This document is available from the Alliance for Telecommunications Industry Solutions (ATIS), 1200 G Street N.W., Suite 500, Washington, DC 20005 2This document is available from the Alliance for Telecommunications Industry Solutions (ATIS), 1200 G Street N.W
24、., Suite 500, Washington, DC 20005 3This document is available from the Alliance for Telecommunications Industry Solutions (ATIS), 1200 G Street N.W., Suite 500, Washington, DC 20005 4This document is available from the Alliance for Telecommunications Industry Solutions (ATIS), 1200 G Street N.W., S
25、uite 500, Washington, DC 20005 5This document is available from the International Telecommunications Union. 2 ATIS-1000615.2014 64 kbit/s, wide- band voice encoded at 64 kbit/s, and voice encoded at bit rates less than 64 kbit/s alone or combined with other digital information streams. 3.3.2 Dchanne
26、l: A 16- or 64-kbit/s channel carrying control and signalling information and, optionally, packetized information and telemetry. 3.3.3 H-channel: A 384-, 1472-, or 1536-kbit/s channel (H0, H10, and H11 respectively) accompanied by timing, intended to carry a wide variety of user information streams,
27、 such as fast facsimile, video, high speed data, high quality audio, information streams each at rates less than the respective H-Channel bit rate that has been rate adapted or multiplexed together, and packet-switched information. 3.4 ITU-T (International Telecommunication Union Telecommunication S
28、tandardization Sector): The ITU has been a specialized agency of the United Nations since 1948. As the oldest international treaty organization, it traces its formal beginnings to 1865. The ITU-T traces its formal beginnings to 1954, when its predecessor, the International Telegraph and Telephone Co
29、nsultative Committee (CCITT) was founded for the purpose of promoting and ensuring the operation of international telecommunications systems. 3.5 Data unit 3.5.1 frame relaying service data unit (FSDU): This term refers to the data units exchanged at the functional boundary between the core function
30、s of ITU-T Recommendation Q.921 (ATIS-1000602) and the end-to-end protocol implemented above the core functions of Q.921 (ATIS-1000602). 3.5.2 frame relaying protocol data unit (FSDU): This term refers to the data units exchanged at the user-network interface. Their format is based on that defined i
31、n ITU-T Recommendation Q.921 (ATIS-1000602). 3.6 digital subscriber line: The physical line connecting the network and the user which allows for transmission of digital signals according to American National Standards. The digital subscriber line may be used, for example, to provide the basic rate i
32、nterface between the user and the network. 3.7 Frames 3.7.1 delivered duplicated frames: A frame D received by a particular destination user is defined to be a duplicated frame if both of the following conditions are true: D was not generated by the source user; D is exactly the same as a frame that
33、 was previously delivered to that destination. 3.7.2 delivered errored frame: A delivered frame is defined to be an errored frame when the value of one or more bits in the frame is in error, or when some, but not all, bits in the frame are lost bits or extra bits (i.e., bits that were not present in
34、 the original signal). 3.7.3 delivered out-of-sequence frame: Consider a sequence of frames F1, F2 , F3, Fn. Assume that F1is transmitted first, F2second, etc. A delivered frame Fiis defined to be out of sequence if it arrives at the destination after any of the frames F(i+1), F(i+2), Fn. 3.7.4 fram
35、e size: Frame size is the number of octets after the address field and before Frame Check Sequence (FCS) field in a frame. Octet count is done either before zero- bit insertion or after zero-bit extraction. 3.7.5 lost frame: A transmitted frame is declared to be a lost frame when the frame is not de
36、livered to the destination user within an agreed-upon measurement period, and the net- work is responsible. The procedure used to reach agreement on the measurement period should allow for the possibility that more than one network may be involved in the connection. 3.7.6 misdelivered frame: A misde
37、livered frame is a frame transferred from a source user to a destination user other than the intended destination user. It is considered inconsequential whether the information is correct or incorrect in content. 3 ATIS-1000615.2014 3.7.7 frame handling (FH) function: A conceptual part of the ISDN t
38、hat is used to interpret, process, and switch frame-mode data calls. 3.8 functional group: Sets of functions that may be needed in ISDN user access arrangements. In a particular access arrangement, specific functions in a functional group may or may not be present, and may be performed in one or mor
39、e pieces of equipment. 3.8.1 network termination 1 (NT1): A functional group that includes functions broadly equivalent to Layer 1 (physical) of the OSI Reference Model. These functions are associated with the proper physical and electromagnetic termination of the network, and include line transmiss
40、ion termination, Layer 1 line maintenance functions and performance monitoring, timing, power transfer, Layer 1 multiplexing, and interface termination. 3.8.2 network termination 2 (NT2): An ISDN functional group that includes functions broadly equivalent to Layer 1 and higher layers of the ITU-T Re
41、commendation X.200 Reference Model. PBXs, local area networks, and terminal controllers are examples of equipment or combinations of equipment that provide NT2 functions. These functions include Layer 2 and Layer 3 protocol handling, Layer 2 and Layer 3 multiplexing, switching, concentration, mainte
42、nance functions, and interface termination. 3.8.3 terminal equipment (TE): A functional group that includes functions broadly belonging to Layer 1 and higher layers of the ITU-T Recommendation X.200 Reference Model. Digital telephones, data terminal equipment, and integrated work stations are exampl
43、es of equipment (or combinations of equipment) that provide these functions. These functions include protocol handling, maintenance functions, interface functions, and connection functions to other equipments. In some publications, Terminal Equipments are called Terminal Endpoints. 3.8.4 terminal eq
44、uipment 1 (TE1): A functional group that includes functions belonging to the functional group TE, and with an interface that complies with the ITU-T ISDN user-network interface Recommendations. In some publications, Terminal Equipments are called Terminal Endpoints. 3.8.5 terminal equipment 2 (TE2):
45、 A functional group that includes functions belonging to the functional group TE, but with an inter- face that complies with national standards e.g., EIA/TIA-232-E or with interface Recommendations other than the ITU-T ISDN interface Recommendations (e.g., the X- Series interface Recommendations), o
46、r an interface not included in ITU-T Recommendations. In some publications, Terminal Equipments are called Terminal Endpoints. 3.8.6 terminal adapter (TA): A functional group that includes functions broadly be- longing to Layer 2 and higher layers of the Recommendation X.200 Reference Model that all
47、ow a TE2 terminal to be served by an ISDN user-network interface. 3.9 ISDN: An Integrated Services Digital Network (ISDN) is a network, in general evolving from an existing telephony network, that provides end-to-end digital connectivity to support a wide range of both voice and non-voice services.
48、User access to an ISDN is via a limited set of standard multi-purpose interfaces. 3.10 information rate: The information rate for a frame relay logical connection is the average number of end user bits transferred per second, in one direction, across a user-net- work interface as measured over an in
49、terval of duration t. The measurement interval t is network dependent. 3.11 Interface 3.11.1 primary-rate interface: An ISDN user-network interface structure where the interface structure is composed of multiple B- Channels and one D-Channel. The bit rate of the D-Channel in this structure is 64 kbit/s. When a 1544-kbit/s primary-rate interface is provided, the interface structure is 23B+D. 3.11.2 basic-rate interface: An ISDN inter- face where the interface structure is com- posed of two B-Channels and one D-Channel, 2B+D. The bit ra
