ATIS 0300217-2013 Integrated Service Digital Network (ISDN) Management - Primary Rate Physical Layer.pdf

1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-0300217.2013 INTEGRATED SERVICE DIGITAL NETWORK (ISDN) MANAGEMENT PRIMARY RATE PHYSICAL LAYER As a leading technology and solutions development organization, ATIS brings together the top global ICT companies to advance the industrys most-pressi

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11、 Customer Installation (4.2). The relationship between PRA lines and paths is shown on Figure 3. The Exchange Termination (ET), NT2, and TE/TA functional groupings terminate DS1 paths, while the Line Termination (LT) and NT1 functional groupings do not. When higher-rate multiplexers are not used on

12、the PRA (See Figure 3, Item a), then the line and path are coincident. When higher-rate multiplexers are used on the PRA (See Figure 3, Item b), then line and path may not be coincident. In these cases, DS1-rate lines exist between the ET and its nearest multiplexer, and between the NT2 or TE/TA and

13、 its nearest multiplexer. However, the DS1-rate path still exists between the ET and the NT2 or TE/TA. 4On an interim basis, to facilitate early implementation of this standard, use of existing 2 of 4, 2 of 5, 3 of 5, etc., framing-error detection criteria may be substituted for this criteria. ATIS-

14、0300217.2013 5 Figure 3 - Line and Path Monitoring 4.1 Customer Access Figure 4 shows a simple ISDN maintenance model for PRA transport. Figure 5 shows a multiple-facility PRA model. Maintenance aspects of these PRA models are described below. Maintenance for PRAs that use DCSs is discussed in Annex

15、 A. Figure 4 - ISDN Model for Primary Rate Customer Access ATIS-0300217.2013 6 Figure 5 - PRA Multiple Facility Model 4.1.1 Simple PRA Figure 4 shows a simple PRA architecture. A DS1 access is shown from an ET to the 1 NT1. Functionally, an ET performs D-channel processing, switching/routing, and re

16、lated tasks. The ET also constructs the DS1 signal that is sent towards the NT1. The DS1 access may optionally traverse non-ISDN intermediate offices and/or be multiplexed onto higher-rate facilities. Also, exchange carrier/interexchange carrier interfaces are possible on the PRA. ATIS-0300217.2013

17、7 4.1.2 Multiple DS1 Facilities The simple PRA model shown in Figure 4 is extended to show three multiple DS1 facility cases in Figure 5. Each of these three cases is described as follows. 4.1.2.1 PRAs with Facility Associated Signaling A model architecture showing multiple PRAs with facility-associ

18、ated signaling is given in Figure 5a. The term “facility-associated” indicates that the D-channel within the PRA provides the signaling for its own bearer-channels5(e.g., up to 23 B-channels) and no others. In Figure 5a, multiple individual DS1-PRA paths are shown connecting an ET via an LT and an N

19、T1 to an NT2. Each DS1-PRA provides its own facility-associated signaling D-channel yielding “n” separate PRA channel configurations of 23B + 1D. 4.1.2.2 PRA with Non-Facility-Associated Signaling When a D-channel can assign calls to bearer-channels6on more than one DS1, including the one carrying t

20、he D-channel, this is called non-facility-associated D-channel signaling. Figure 5b shows the same multiple interface with “n” DS1s as in Figure 5a, this time with non-facility-associated signaling in which a single D-channel may control all B- channels carried by the “n” DS1s e.g., a channel config

21、uration of 95B + 1D when “n” equals 4. 4.1.2.3 Non-Facility Associated Signaling PRA with Backup D-channels A multiple interface with non-facility-associated signaling may also be equipped with D-channel back-up using an active and standby D-channel7. This back-up arrangement provides signaling redu

22、ndancy when large numbers of bearer-channels are controlled. In this arrangement, the numbering of the B- and D-channels is static, regardless of any back-up switching. After back-up switching has occurred, the former standby D-channel becomes (and remains) the active D-channel until the next back-u

23、p event. In the D-channel back-up example in Figure 5c, two D- channels are used (only one active at a time), each located in a different DS1. 94B + 2D, when “n” equals 4, would be an example of such a channel configuration. In general, during the back-up process, stable calls on non-failed bearer c

24、hannels remain up, but some transient calls and temporary signaling connections may be impacted. Details of the failure conditions and the management states used for non-facility-associated signaling with and without backup will be covered in another standard. The protocol used to control the D-chan

25、nel backup is covered in ATIS-1000607 (also see Annex F of ITU-T Rec. Q.931). 5In this case, the bearer channels may be any combination of B- and H0-channels that use up to twenty-three 64-kb/sec timeslots or an H10 channel. 6In this case, the bearer channels may be any combination of B-, H0-, H10-,

26、 or H11- channels that use up to the capacity of the twenty-three 64- kb/s timeslots on the DS1 carrying the D-channel and the twenty-four 64- kb/s timeslots on the other DS1s, with the constraint that H-channels are not split across DS1s. 7D-channel back-up is not associated with any protection swi

27、tching provided on the DS1 or higher-order facilities. ATIS-0300217.2013 8 4.2 Customer Installation Figure 6 provides examples of primary rate customer configuration models. These show the relationships between the NT/TE/TA functional groups, reference points, interfaces and equipment realizations.

28、 Case A shows the S/T interface that applies when no NT2 functions are required, and the NT1 and TE/TA functions are in separate pieces of equipment. Case B has the NT1 and TA/TE functional groups combined into the same piece of equipment. Case C shows the NT1, NT2 and primary-rate TE/TAs all in sep

29、arate pieces of equipment. Case D has the NT1 and NT2 combined into one piece of equipment. Case E shows the same configuration as case C, except that the TE/TAs are at basic rate. Note that when a stand-alone NT1 is provided (e.g., cases A, C and E), then an NT1 power failure could appear to the TE

30、/TA or NT2 as a failed PRA. For more details on how the various maintenance capabilities described in this standard are combined in typical pieces of customer installation equipment see Annex B. Annex B also describes the relationships in the customer installation between the features at the NI, the

31、 U, T, and S reference points shown in Figure 6 and the Iaand Ibphysical interfaces to the primary rate customer equipment. ATIS-0300217.2013 9 Figure 6 - ISDN Equipment Realizations for Primary Rate Customer Installation 5 Required Capabilities This clause describes required capabilities in the fol

32、lowing areas: Transmission format maintenance features (5.1); Performance monitoring capabilities (5.2); and Testing capabilities (5.3). ATIS-0300217.2013 10 5.1 Transmission Format Maintenance Features Only primary access provided over transport systems that use the ESF8will be treated in this stan

33、dard. Continuous automatic surveillance requires the following operations features (see ATIS-0600403) to be included in the transmission format (ESF) for DS1 paths that carry primary access: CRC code; Performance report messages; EOC; and Alarms for service-affecting troubles. The functional capabil

34、ities provided by these features are briefly described as follows. 5.1.1 Cyclic Redundancy Check The CRC code is an error-detection code that is generated from the information bits in the superframe and inserted into the bit stream by the transmitter. At a downstream location, a CRC calculated from

35、the received information bits in the superframe is compared with the CRC received in the bit stream. If the two CRCs differ, there has been at least one error in the superframe. 5.1.2 Performance Report Messages Single-ended performance monitoring is accomplished by the use of the performance report

36、 message. Each path termination measures the errors in the incoming signal and periodically sends information on these to the far end path termination using the performance report message. 5.1.3 Embedded Operations Channel The EOC carries performance report messages, Remote Alarm Indication (RAI) si

37、gnals (described in 5.1.4), and loopback commands. Other EOC functions needed to support ISDN PRA are a subject for further study. The PRA architecture may be such that the EOC may be discontinuous (e.g., see Annex A). Other potential EOC functions are also discussed in Annex A. 8ESF is needed to ov

38、ercome operational limitations of the Superframe Format (SF). Some SF limitations that become apparent when transmitting digital data are the occurrence of false framing in the presence of marginal error performance, the occurrence of false yellow alarms, and limitations on in-service performance mo

39、nitoring capabilities (including the absence of any visibility on the performance of the signal received by the user). ATIS-0300217.2013 11 5.1.4 Alarms for Service-Affecting Troubles Service-affecting troubles prevent user channels from carrying user information, and put the PRA in the unavailable

40、state. Figure 7 shows a realization of the PRA with the NT1 and NT2/TE functional groups in separate pieces of equipment for four possible failure conditions. It also shows how the equipment responds to these failures. Figure 8 shows a realization of the PRA with the NT1 and NT2/TE functional groups

41、 in a single piece of equipment, and how this equipment responds to incoming and outgoing failures. Note that the behavior of the NT2/TE equipment in Figure 7 is identical to the behavior of the combined equipment in Figure 8. (The ET response is also the same in the two figures.) Annex C provides a

42、dditional details about the operational states associated with these failures. Figure 7 - Possible Fault Locations and Resulting Alarm Transmissions ATIS-0300217.2013 12 Figure 8 - Possible Fault Locations Fault detection and sectionalization to the responsible repair organization; Storage of perfor

43、mance data; Remote access to current and stored performance data; and Remotely-settable alert thresholds; Continuous monitoring of the transmission system, made possible by in-service performance measurements, allows for trouble-detection and possibly repair of the ISDN access lines before the custo

44、mer reports a trouble. When customers do report troubles, recent in-service data can be used to verify the trouble and, in some cases, sectionalize the problem to the responsible repair organization, leading to efficient trouble clearance. This serves to keep the quality and availability of the ISDN

45、 PRAs high. When responding to trouble reports, performance history data is needed to quickly assess the recent performance of the lines. Limited performance data shall be stored in network elements to allow performance assessment against long-term performance objectives. 5.2.1 Performance Monitorin

46、g from Network Point of View The Layer 1-monitored entities from the network point of view are: DS1 lines; DS1 paths; Intermediate DS1 paths9; DS3 or higher-rate facilities. For all layer 1-monitored entities, each direction of transmission is monitored separately. Figure 3 shows that DS1 lines (bet

47、ween two LTs) are monitored by Line Monitoring Functions (LMF). It also shows that DS1 paths (between two Path Terminations PTs) are monitored by Path Monitoring Functions (PMFs). The PMF uses CRC and performance report message information to monitor bi-directional path performance. Note that perfor

48、mance report messages also contain far-end line monitoring information. The Remote Line Monitoring Function (RLMF) uses this information to monitor far end line performance. DS3 or higher-rate facilities (between two multiplexers) are also monitored. Figure 9 shows an optional configuration in which

49、 intermediate DS1 paths (between a PT and an intermediate point) are monitored by Intermediate Monitoring Functions (IMFs). The network provider may optionally locate IMFs at non-ISDN central offices in order to sectionalize loop and inter-office troubles. Similarly, customers may optionally locate IMFs within NT1s to sectionalize troubles between customer and network plant. 9Points intermediate to DS1 paths may also be intermediate to DS1 lines. ATIS-0300217.2013 14 Figure 9 - Possible Locations for IMF In the remainder of 5.2, requirements are given f