1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-1000640.2001(R2011) BROADBAND ISDN NETWORK NODE INTERFACES AND INTER-NETWORK INTERFACES RATES AND FORMATS SPECIFICATIONS ATIS is the leading technical planning and standards development organization committed to the rapid development of global,
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11、rd for Telecommunications Broadband ISDN Network Node Interfaces and Inter-Network Interfaces Rates and Formats Specifications Secretariat Alliance for Telecommunications Industry Solutions Approved August 21, 2001 American National Standards Institute, Inc. Abstract This standard provides specifica
12、tions of the rates and formats of signals for use at Network Node Interfaces (NNIs) and Inter-Network Interfaces (INIs) in a Broadband Integrated Services Digital Network (B-ISDN). ATIS-1000640.2001 ii Foreword The information contained in this Foreword is not part of this American National Standard
13、 (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 contain requirements necessary for conformance to the standard. Accredited Sta
14、ndards Committee T1, Telecommunications serves the public through improved understanding between carriers, customers, and manufacturers. Technical Subcommittee T1S1 of Committee T1 develops telecommunications standards and technical reports related to services, architectures, and signaling, in addit
15、ion to related subjects under consideration in other North American and international standards bodies. ANSI guidelines specify two categories of requirements: mandatory and recommendation. The mandatory requirements are designated by the word shall and recommendations by the word should. Where both
16、 a mandatory requirement and a recommendation are specified for the same criterion, the recommendation represents a goal currently identifiable as having distinct compatibility or performance advantages. Suggestions for improvement of this standard are welcome. They should be sent to the Alliance fo
17、r Telecommunications Industry Solutions, T1 Secretariat, 1200 G Street NW, Suite 500, Washington, DC 20005. This standard was processed and approved for submittal to ANSI by Accredited Standards Committee on Telecommunications, T1. Committee approval of the standard does not necessarily imply that a
18、ll members voted for its approval. At the time it approved this standard, the T1 Committee had the following members: E.R. Hapeman, 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 M. Dolly, T1S1
19、Technical Editor EXCHANGE CARRIERS Organization Represented Name of Representative AT for example, between different network providers or carriers. Inter-Network connections can also be found between different ATM Networks belonging to a single carrier. Figure 1 illustrates the reference architectur
20、e for inter-network connections and relates the Inter-Network Interface (INI) to the Network Interface (NI), which is one of the User-Network Interfaces (UNI). The INI connects two ATM Networks, either directly or via one or multiple tandem ATM Networks. The NI is the type of UNI that provides custo
21、mer access to the network; such access may be service specific, e.g., for Cell Relay Service (CRS), Frame Relay Service (FRS), Switched Multi-megabit Data Service (SMDS), or Circuit Emulation Service (CES). If the INI for B-ISDN connects two networks belonging to two different carriers, it is also k
22、nown as B-ISDN Inter-Carrier Interface (B-ICI). 2. Intra-network connections can be found within a single ATM Network between two Network Nodes, usually between two sites, as shown in Figure 2. This interface is termed Network Node Interface (NNI) and is also referred to as SONET (or other transport
23、 system) mid-span meet. Annex B shows a diagram that relates ATM Networks and customer installations and the various interfaces involved. ATIS-1000640.2001 5 Figure 1 - Inter-network reference architecture Figure 2 - Intra-network reference architecture 6 Interface physical realizations Two basicall
24、y different interface physical realizations can be distinguished: 1. The first one, labeled NNI/INI and shown in Figure 3, is a direct interoffice interconnection between two ATM Units. Thus, the NNI/INI may correspond to a transport interface such as a SONET mid-span meet. The interconnection may b
25、e between two Network Nodes within the same network (NNI), or between two Network Nodes in different networks (INI). ATIS-1000640.2001 6 2. The second one, labeled NNI/INI and shown in Figure 4, is a multiplexed interoffice interconnection between two SONET Transport Systems, where ATM represents a
26、logical channel or tributary that is only part of the overall transported payload that traverses the NNI/INI. SONET Transport Systems may be multiplexes or cross-connect systems capable of aggregating individual circuits (or channels, or tributaries) for transport over a higher capacity transport sy
27、stem. As in Figure 3, the interconnection may be between two Network Nodes within the same network (NNI) or between two Network Nodes in different networks (INI).2)The above definitions apply just as well for non-SONET Transport Systems. In particular, ATM on either DS1 or DS3 may be transported ove
28、r non-SONET systems. Figure 3 - Physical realization example of the NNI and INI 2The above definitions for the NNI/INI and NNI/INI interfaces are consistent with the definitions introduced in the B-ICI Specifications (see Annex C for reference) for the B-ICI and B-ICI interfaces, respectively. Thus,
29、 the INI and INI between networks belonging to different carriers correspond to the B-ICI and B-ICI, respectively. ATIS-1000640.2001 7 Figure 4 - Physical realization example of the NNI and INI 7 Physical layer specifications at 51.840 Mbit/s The B-ISDN interface at 51.840 Mbit/s is SONET-based and
30、utilizes the STS-1 payload structure. This interface, if implemented, shall comply with the specifications in this clause. 7.1 Bit rate At the physical layer, the nominal bit rate shall be 51.840 Mbit/s. The bit rate available for user information cells, signaling cells, and ATM layer OAM cells, exc
31、luding physical layer related maintenance information transported in SONET overhead bytes, shall be nominally 48.384 Mbit/s. This rate is equivalent to the STS-1 Synchronous Payload Envelope (SPE) payload capacity (i.e., the total STS-1 SPE capacity minus the portion allocated to POH and fixed stuff
32、 bytes in columns 30 and 59). 7.2 Interface symmetry The 51.840 Mbit/s interface shall be symmetric (i.e., the same bit rate shall be transmitted in both directions). 7.3 Signal format The 51.840 Mbit/s interface is based on SONET as specified in T1.105-2001 and shall utilize the SONET STS-1 frame s
33、tructure as specified in T1.646-1995 for the UNI. This frame structure contains fixed stuff bytes in columns 30 and 59. 7.3.1 Overhead bytes active across the interface The active overhead bytes within the SONET frame depend on implementation details of the physical circuit connection. The following
34、 overhead specifications are intended to maintain flexibility, while still ATIS-1000640.2001 8 allowing specific requirements on overhead activation and functionality for the physical realizations described in 6 that distinguish between two types of interfaces, the NNI/INI and the NNI/INI. In all th
35、ese realizations, the following requirement applies: The overhead bytes active across the two types of interfaces shall be consistent with the specifications given in T1.105-2001. A summary of the SONET overhead bytes and their requirement status is provided in Table 1.3Note that, consistent with th
36、e discussion in 6, only the Path Overhead is specified for NNI/INI in Table 1, while the Section and Line Overheads for NNI/INI are dictated by the multiplex/transport system. The tables notes are considered an integral part of the overhead specification. The following definitions apply to Table 1,
37、as well as to Table 2: Required (R) These signals at the interface shall contain valid information as defined by this standard. Optional (O) Valid information may or may not be present in these signals. Use of these functions is a local matter. Not Active (NA) This function is not defined at the int
38、erface. 3Table 1 applies to all SONET rates, not just to 51.840 Mbit/s. ATIS-1000640.2001 9 Table 1 - SONET overhead requirements for the interfaces Overhead byte Function NNI INI NNI INI Section overhead A1, A2 Framing R1they do not represent requirements set by this standard. ATIS-1000640.2001 11
39、7.9 PMD characteristics Information about the PMD characteristics can be found in T1.646-1995 for the short-reach, intermediate-reach, and long-reach optical OC-1 and the electrical STSX-1 applications.4The choice of interface parameter set is application specific. 7.10 Synchronization, timing, and
40、jitter In normal operation, the signal at the interface is synchronized by a source traceable to a Primary Reference Source (PRS) as described in T1.101-1999. This source may be a Stratum 3 (or better) quality clock that is traceable to a Stratum 1 clock. When the signal at the interface is not sync
41、hronized (e.g., when in the free-running mode), a failure condition exists that needs corrective action. Information about the network interface jitter limits can be found in T1.105.03-1994. 8 Physical layer specifications at 155.520 Mbit/s The B-ISDN interface at 155.520 Mbit/s is SONET-based and u
42、tilizes the STS-3c concatenated payload structure. This interface, if implemented, shall comply with the specifications in this clause. 8.1 Bit rate At the physical layer, the nominal bit rate shall be 155.520 Mbit/s. The bit rate available for user information cells, signaling cells, and ATM layer
43、OAM cells, excluding physical layer related maintenance information transported in SONET overhead bytes, shall be nominally 149.760 Mbit/s. This rate is equivalent to the STS-3c SPE payload capacity (i.e., the total STS-3c SPE capacity minus the portion allocated to POH). 8.2 Interface symmetry The
44、155.520 Mbit/s interface shall be symmetric (i.e., the same bit rate shall be transmitted in both directions). 8.3 Signal format The 155.520 Mbit/s interface is based on SONET as specified in T1.105-2001 and shall utilize the SONET STS-3c frame structure as specified in T1.646-1995 for the UNI. 4Tel
45、cordia (former known as Bellcore) GR-253-CORE may also be useful; see Annex C for reference. ATIS-1000640.2001 12 8.3.1 Overhead bytes active across the interface The overhead bytes active across the two types of interfaces described in 6 and further discussed in 7.3.1 shall be consistent with the s
46、pecifications given in T1.105-2001. A summary of the SONET overhead bytes and their requirement status is provided in Table 1 for the two types of interfaces. 8.3.2 ATM cell mapping The ATM cell stream shall be directly mapped into the STS-3c SPE payload capacity by aligning the byte structure of ev
47、ery cell with the byte structure of the SONET frame, as specified in T1.105-2001. The entire payload capacity is filled with cells, row by row. Because the payload capacity is not an integer multiple of the cell length, a cell may cross the SPE boundary. 8.3.3 Framing Framing information shall be co
48、ntained in the A1 and A2 bytes as defined in T1.105-2001. 8.4 Cell rate decoupling The physical layer shall expect cells to arrive from the ATM layer at a rate equal to the payload capacity of the SONET frame. This implies communication of the exact payload capacity to the ATM layer from the physica
49、l layer. The ATM layer inserts unassigned cells when assigned cells are not available to fill the payload capacity. Further information and detailed specification of unassigned and assigned ATM cells can be found in T1.627-1993 (R1999). An alternate method, where cell rate decoupling is performed at the physical layer by inserting idle cells when assigned and unassigned cells are not available from the ATM layer, is described in T1.646-1995. 8.5 Powering arrangements Power shall not be provided across the 155.520 Mbit/s interface. 8.6 HEC ge
