ANSI ATIS 0300206-2001 Digital Exchanges and PBXs C Digital Circuit Loopback Test Line with N C DS0 Capability.pdf

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1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-0300206.2001(R2011) Digital Exchanges and PBXs Digital Circuit Loopback Test Line with N DS0 Capability ATIS is the leading technical planning and standards development organization committed to the rapid development of global, market-driven st

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4、rtnership Project (3GPP), a member and major U.S. contributor to the International Telecommunication Union (ITU) Radio and Telecommunications Sectors, and a member of the Inter-American Telecommunication Commission (CITEL). For more information, please visit . AMERICAN NATIONAL STANDARD Approval of

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10、odically 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 some of which are associated with other North American telecommuni

11、cations networks. These standards may apply to planning, engineering and provisioning of network resources; to operations, maintenance or administration process; or to requirements and recommendations for support systems and equipment that may be used for these functions. ANSI guidelines specify two

12、 categories of requirements: mandatory and recommendation. The mandatory requirements are designated by the word shall and recommendations by the word should. Where both a mandatory requirement and a recommendation are specified for the same criterion, the recommendation represents a goal currently

13、identifiable as having distinct compatibility or performance advantages. Suggestions for improvement of this standard are welcome. They should be sent to the Alliance for Telecommunications Industry Solutions, T1 Secretariat, 1200 G Street NW, Suite 500, Washington, DC 20005. This standard was proce

14、ssed and approved for submittal to ANSI by Accredited Standards Committee on Telecommunications, T1. Committee approval of the standard does not necessarily imply that all members voted for its approval. At the time it approved this standard, the T1 Committee had the following members: E. R. Hapeman

15、, T1 Chair W.R. Zeuch, T1 Vice-Chair J. A. Crandall, T1 Director S. M. Carioti, T1 Disciplines S. D. Barclay, T1 Secretary C.A. Underkoffler, T1 Chief Editor EXCHANGE CARRIERS Organization Represented Name of Representative AT b) The switch selects the (potentially N DS0) trunk based on translation

16、of the address of the far-end test line (i.e., as in normal call processing); c) The tester selects a specific primary rate facility, and the switch selects the next available (potentially N DS0) channel on that facility; d) The tester selects a specific primary rate facility and the N-specific DS0

17、channels on that facility (N does not exceed the maximum number of DS0 channels on the facility); or e) In situations where the N DS0s that make up the N DS0 channel are required to be consecutive, the tester specifies the Circuit Under Test by referencing the leading (low-numbered) DS0 channel (tim

18、e-slot). 5.2 Far-end access Access to the digital loopback test lines at the far-end digital exchange shall be accomplished via the normal exchange switching equipment on a 4-wire basis on all incoming and two-way circuits. The test line address code is established for exchanges in the public switch

19、ed network in T1.207-2000.Currently, code 108 has been assigned to the digital loopback test line. Private networks may use this or other numbering. The bandwidth of the loopback shall be controlled by the signaling information conveyed between the near and far end by the Bearer Capability informati

20、on element or User Service Information parameter contained in the DSS1 SETUP message or the SS7 IAM, respectively. If neither of these means are available, only single DS0 testing is supported. The CUT is identified by the DSS1 Channel ID information element or the SS7 Circuit Identification Code or

21、 - for single channel testing - via in-band signaling, as appropriate. 6 Specification for digital loopback test line apparatus 6.1 Test equipment Currently, ITU-T Recommendation O.152 and ANSI/IEEE 1007 specify suitable digital signal generators and test receivers. ATIS-0300206.2001 6.2 Digital loo

22、pback test line specifications The loopback test line may be integrated into the switching system fabric of the digital exchange or may be provided in a stand-alone configuration similar to some existing test lines. 6.2.1 Single DS0 The digital loopback test line shall provide a dialable, 4-wire tes

23、t line capability and include circuitry that accepts and loops back received octets from a digital circuit. The octets, when looped back, shall be retransmitted so that the positions of the bits within the octets are preserved. This means that the most significant bit of the retransmitted octet corr

24、esponds to the most significant bit of the received octet. This requirement provides a non-inverting loopback test line capable of passing 64-kbit/s unrestricted signals. In this manner, all single channel digital services (e.g., 56 kbit/s, 64 kbit/s restricted, and 64 kbit/s unrestricted) can pass

25、digital test signals through this test line. In addition, digitally encoded analog test signals also can be passed through this test line. 6.2.2 Bit sequence integrity When a loopback supporting more than a single DS0 is implemented, bit sequence integrity across the N DS0 channel must be maintained

26、 by the loopback. 6.2.3 DS0 integrity In addition, loopbacks supporting more than a single DS0 shall apply the requirement in 6.2.1 to each individual DS0. That is to say, each DS0 shall be looped back into itself. This requirement on the test line is such that the tester may apply the digital test

27、pattern to only some of the channels in a N DS0 call and expect the test pattern to be returned in those same channels. However, it should be pointed out that such testing would not identify all problems on the N DS0 call. 7 Signaling system test line test sequence 7.1 Circuit seizure and disconnect

28、 When the outgoing circuit is to be seized and connected to the digital loopback test line at the distant end, the appropriate address information is transmitted in accordance with the specification for the signaling system in use. Normal switching system test call connection and disconnect procedur

29、es shall be followed for seizure and disconnect as associated with the circuit accessing the test line termination. Therefore, the originator (calling party) of a test call may seize and disconnect consistent with the processing procedures for a normal test call. In addition, the loopback test line

30、(called party) shall be capable of disconnecting independent of circuit supervision by the calling party (see 7.4). 7.2 Test line answer When access is gained to the test line, an answer supervision signal shall be returned. If the limit of the number of test lines available is reached, a busy indic

31、ation shall be returned to the originating end in accordance with the normal signaling for the circuit and the address concerned. ATIS-0300206.2001 7.3 Test line not equipped When a test line call is received at a digital exchange not equipped to handle single channel or N DS0 test calls, the called

32、 exchange shall respond with the standard “unallocated number” signal if available for the signaling system employed. If an N DS0 testline is requested and only a single channel test line is implemented the called exchange shall reject the call and indicate the cause as “Bearer Capability Not Implem

33、ented” (Cause value 65). 7.4 Automatic test line disconnect The digital loopback test line shall be automatically disconnected from the circuit under test at the terminating digital exchange independent of the circuit supervision state (off-hook) after a specified holding time. This holding time sha

34、ll be easily configurable by the switching system and be user changeable. Furthermore, a 20 minute holding time (15 minute maximum test time plus 5 minute calling party disconnect grace period) should be incorporated into the switching system as a default automatic disconnect parameter. 8 Number of

35、test lines A large number of loopback test lines may be integrated into a digital exchange subject to a limit based upon other network congestion and traffic considerations. The number of digital loopback test lines to be provided at a digital exchange or PBX should be specified by the switch admini

36、strator. The appropriate number of test lines should be determined with the following parameters taken into account: a) the maximum digital test interval employing this test line (15 minutes); b) the number of digital trunk groups terminating in the particular exchange or PBX (i.e., possible number

37、of simultaneous seizures); c) the digital circuit growth taking place within the exchange or PBX (i.e., circuit order test activities); and d) the number of N DS0 test calls that are likely to occur simultaneously. ATIS-0300206.2001 Annex A (informative) Bibliography T1.113-1995, Telecommunications

38、Signalling System No. 7 (SS7) Integrated Services Digital Network (ISDN) User Part2). T1.607a-1996, Telecommunications Integrated Services Digital Network (ISDN) Layer 3 Signaling Specification for Circuit-switched Bearer Service for Digital Subscriber Signaling System Number 1 (DSS1)2). ANSI/IEEE 1

39、007-1992, Methods and equipment for measuring the transmission characteristics of PCM telecommunications circuits and systems ITU-T Recommendation O.152, Error performance measuring equipment operating at the primary rate and above, Vol. IV, Fascicle IV.43) 2) Available from the Alliance for Telecommunications Industry Solutions, online at http:/www.atis.org. 3) Recommendations are available from the American National Standards Institute, 25 West 43rdStreet, New York, NY 10036.