WPCL 2BJ|x H   X  6p&6p& I  HH  c4 P   c4 P styleref head_footRecommendation G. 782 c4 P  PAGE1 c4 P    HH  c4 P PAGE24  c4 P styleref head_footRecommendation G. 782  HH Hp P X`h!(# X   c4 P  Recommendation G. 782 HP X`h!(#Ё c4 P  Recommendation G. 782 Hp P X`h!(#Ђ88  c4 P TYPES AND GENERAL CHARACTERISTICS OF SYNCHRONOUS 89DIGITAL HIERARCHY (SDH) MULTIPLEXING EQUIPMENT  c4 P   The CCITT, considering  H  (a)pthat Recommendations G.707, G.708 and G.709 form a coherent set of specifications for the synchronous digital hierarchy (SDH) and the network node interface (NNI);  H  (b)pthat Recommendation G.781 gives the structure of Recommendations on multiplexing equipment for the SDH;  (c)pthat Recommendation G.783 specifies the characteristics of SDH multiplexing equipment functional blocks;  H  (d)pthat Recommendation G.784 addresses management aspects of the SDH;  (e)pthat Recommendation G.957 specifies characteristics of optical interfaces for use within the SDH;  H  (f)pthat Recommendation G.958 specifies digital line systems based on the SDH for use on optical fibre cables;  H  (g)pthat Recommendation G.703 describes electrical interfaces for use within the SDH, recommends  H  that SDH multiplexing equipment should have general characteristics as described in this Recommendation. 1X Introduction 1.1h  Scope  Recommendation G.781 gives the structure of Recommendations on SDH multiplexers. This Recommendation gives an overview of the functions of SDH multiplexing equipment, examples of various multiplexing equipment types and general performance requirements.  The possibilities of add/drop features, mixed payloads and flexible tributary/channel associations in SDH multiplexers make it difficult to provide a Recommendation which is unambiguous while remaining generic enough not to constrain implementation. To overcome these difficulties, the "functional reference model" approach has been adopted. Therefore this series of Recommendations describes the equipment in terms of various functional blocks. This logical partitioning is used to simplify and generalize the description. It does not imply any physical partitioning or implementation.  H  Only external interface requirements will be specified. For payloads these will conform to either STMN (according to Recommendations G.707, G.708 and G.709) or Recommendation G.703. The interface to the transmission management network (TMN) will conform to Recommendation G.773. The points between function blocks exist only as logical reference points and not as internal interfaces; there is therefore no interface description or interface specification associated with these points.  1.2pAbbreviations   AISp Alarm indication signal   AUp Administrative unit   AUGpAdministrative unit group   DCCpData communications channel   FEBE Far end block error   FERF Far end receive failure   HPApHigher order path adaptation   HPCp Higher order path connection   HPTp Higher order path termination   LPAp Lower order path adaptation   LPC  Lower order path connection   LPTp Lower order path termination   MCFpMessage communications function   MSOH Multiplex section overhead   MSPpMultiplex section protection   MST  Multiplex section termination   MTPI Multiplexer timing physical interface   MTS  Multiplexer timing source   NNIp Network node interface   NOMC Network operators maintenance channel   PDHpPlesiochronous digital hierarchy   PIp Physical interface   POHpPath overhead   RSOH Regenerator section overhead   RSTp Regenerator section termination   SAp Section adaptation   SDHpSynchronous digital hierarchy   SEMF Synchronous equipment management function   SOHpSection overhead   SPIp SDH physical interface   STMpSynchronous transport module   TMNpTelecommunications management network   TUp Tributary unit   TUGpTributary unit group   VCp Virtual container HH   1.3pDefinitions  H  Note - The following definitions are relevant in the context of SDHrelated Recommendations.  H1.3.1 Administrative unit (AU)  See Recommendation G.708.  H1.3.2 Administrative unit group (AUG)  See Recommendation G.708.  H1.3.3 Data communications channel (DCC)  See Recommendation G.784.  H1.3.4  higher order path  In an SDH network, the higher order (HO) path layers provide a server network for the lower order (LO) path layers. The comparative terms lower  H and higher refer only to the two participants in such a client/server relationship. VC1/2 paths may be described as lower order in relation to VC-3 and VC4 while the VC3 path may be described as lower order in relation to VC4.  H1.3.5  higher order path adaptation (HPA)  H  The HPA function adapts a lower order VC (VC1/2/3) to a higher order VC (VC3/4) by processing the TU pointer which indicates the phase of the VC1/2/3 POH relative to the VC3/4 POH and assembling/disassembling the complete VC3/4.  H1.3.6  higher order path connection (HPC)  H  The HPC function provides for flexible assignment of higher order VCs (VC3/4) within an STMN signal.  H1.3.7  higher order path termination (HPT)  H  The HPT function terminates a higher order path by generating and adding the appropriate VC POH to the relevant container at the path source and removing the VC POH and reading it at the path sink.  H1.3.8 Lower order path  See higher order path above.  H1.3.9  lower order path adaptation (LPA)  The LPA function adapts a PDH signal to an SDH network by mapping/demapping the signal into/out of a synchronous container. If the signal is asynchronous, the mapping process will include bit level justification.  H1.3.10  lower order path connection (LPC)  H  The LPC function provides for flexible assignment of lower order VCs in a higher order VC.  H1.3.11  lower order path termination (LPT)  H  The LPT function terminates a lower order path by generating and adding the appropriate VC POH to the relevant container at the path source, removing the VC POH and reading it at the path sink.  H1.3.12 Message communications function (MCF)  See Recommendation G.784.  1.3.13  multiplex section overhead (MSOH)  HH  The MSOH comprises rows 5 to 9 of the SOH of the STMN signal.  H1.3.14  multiplex section protection (MSP)  H  The MSP function provides capability for switching a signal between and including two MST functions, from a working to a protection section.  H1.3.15  multiplex section termination (MST)  H  The MST function generates the MSOH in the process of forming an SDH frame signal and terminates the MSOH in the reverse direction.  H1.3.16  multiplexer timing physical interface (MTPI)  The MTPI function provides the interface between an external synchronization signal and the multiplexer timing source.  H1.3.17  multiplexer timing source (MTS)  H  The MTS function provides timing reference to the relevant component parts of a multiplexing equipment and represents the SDH network element clock.  H1.3.18 Path overhead (POH)  See Recommendation G.708.  H1.3.19  regenerator section overhead (RSOH)  The RSOH comprises rows 1 to 3 of the SOH of the STMN signal.  H1.3.20  regenerator section termination (RST)  H  The RST function generates the RSOH in the process of forming an SDH frame signal and terminates the RSOH in the reverse direction.  H1.3.21  section adaptation (SA)  H  The SA function processes the AU3/4 pointer to indicate the phase of the VC3/4 POH relative to the STM-N SOH and assembles/disassembles the complete STMN frame.  H1.3.22 Synchronous digital hierarchy (SDH)  See Recommendation G.707.  H1.3.23  synchronous equipment management function (SEMF)  H  The SEMF converts performance data and implementation specific hardware alarms into objectoriented messages for transmission over the DCC(s) and/or a Q interface. It also converts object-oriented messages related to other management functions for passing across the Sn reference points.  H1.3.24 Section overhead (SOH)  See Recommendation G.708.  1.3.25  SDH physical interface (SPI)  H  The SPI function converts an internal logic level STMN signal into an STMN line interface signal.  H1.3.26 Synchronous transport module (STM)  See Recommendation G.708.  H1.3.27 Telecommunications management network (TMN)  See Recommendation M.30.  H1.3.28 Tributary unit (TU)  See Recommendation G.708.  H1.3.29 Tributary unit group (TUG)  See Recommendation G.708.  H1.3.30 Virtual container (VC)  See Recommendation G.708. 2 Overview of equipment functions 2.1  Multiplexing method 2.1.1 Generalized logical blocks  H  Figure 21/G.782 is a generalized Multiplexer Logical Block Diagram. It illustrates the steps that are required to assemble various payloads and multiplex them into an STMN output. It does not represent a useful or practical network function. Examples of some configurations that may be deployed are given in S3.  The only function blocks that are payload specific are the physical interface/path adaptation blocks used at the G.703 interfaces; all other functions are nonpayload specific. Therefore all operations functions, except those associated with G.703 interfaces, are payload independent. New payload types can be added by providing a new interface function; all other parts of the system will be unaffected.  A brief description of the signal flow between a Recommendation G.703 interface and the STMN output is provided in SS2.1.2 and 2.1.3. Description of functions performed by each of the logical blocks in Figure21/G.782 is provided in Recommendations G.783 and G.784. Further descriptions of the synchronous equipment management function (SEMF) and message communications function (MCF) are given in S2.2 and descriptions of the multiplexer timing source (MTS) and multiplexer timing physical interface (MTPI) are given in S4. c4 P  LFIGURE 21/G.782 = 18,5 cm  c4 P  2.1.2 Signal flow G.703 input to STMN output: multiplexing H "҇Hp P Ђ Physical interface/ x!lower order path1p2adaptation Hh8`h!"ЁProvides the appropriate G.703 interface and maps the payload into the container as specified in RecommendationG.709. H "҇Hp P Ђ Lower order pathtermination Hh8`h!"ЁAdds the VC path overhead (VCPOH). H "҇Hp P Ђ Lower order pathconnection Hh8`h!"ЁAllows flexible assignment of the VC1/2 within the VC3/4. H "҇Hp P Ђ Higher order pathadaptation Hh8`h!"ЁProcesses the TU pointer to indicate the phase of the VC1/2 POH relative to the VC3/4 POH and assembles the complete VC3/4. H "҇Hp P Ђ Higher order pathtermination Hh8`h!"ЁAdds the VC3/4 path overhead. H "҇Hp P Ђ Higher order path connection Hh8`h!"ЁAllows flexible assignment of the VC3/4 within the STMN.  HH Hp P X`h!(# H "҇  Hp P XHHSection adaptation  h8`h!"ЁProcesses the AU3/4 pointer to indicate the phase of the VC3/4 POH relative to the STMN SOH. Bytemultiplexes the AU Groups (AUGs) to construct the complete STMN frame. H "҇p P Ђ Multiplex section protection h8`h!"ЁProvides capability for branching the signal onto another line system for protection purposes. H "҇p P Ђ Multiplex section termination h8`h!"ЁGenerates and adds rows 5 to 9 of the SOH. H "҇p P Ђ Regenerator section termination h8`h!"ЁGenerates and adds rows 1 to 3 of the SOH; the STMN signal is then scrambled except for row 1 of the SOH. H "҇p P Ђ SDH physical interface h8`h!"ЁConverts the internal logic level STMN signal into an STMN interface signal. This may be an instation electrical signal, an instation optical signal or an interstation optical signal.  HH Hp P X`h!(#2.1.3 Signal flow STMN input to G.703 output: demultiplexing H "҇HP Ђ SDH physical interface HX`h!"ЁConverts the interface signal into an internal logic level and recovers timing from the line signal. H "҇HP Ђ Regenerator section termination HX`h!"ЁIdentifies the STMN frame word, descrambles the signal, and processes rows 1 to 3 of the SOH.  Hh Hp P X`h!(#  The remaining operations are the inverse of those performed when multiplexing except that the C1/2 interface function must provide a buffer store and smoothing circuit to attenuate the clock jitter caused by the multiplex process, pointer moves and bit stuffing (if applicable). 2.2h  Operations, administration, maintenance and provisioning (OAM&P)  H2.2.1 Overhead applications  H  Recommendation G.708 specifies bandwidth allocated within the SDH frame structure for various control and maintenance functions. Two types of overhead are identified: Virtual Container Path Overhead (VCPOH) and Section Overhead (SOH).  H2.2.1.1pPOH application  Details of the functions provided by the POH are contained in Recommendations G.708 and G.709.  H  The VCPOH is generated and terminated at the point where the payload is assembled or disassembled. Itisused for end to end monitoring of the payload and may transit several multiplex and line systems. Some of the VC-POH is completely payload independent, while other parts of the VCPOH are used  H in specific ways according to the type of payload. In all cases, the VCPOH is independent of user information. Thus it may be monitored at any point within an SDH network to confirm network operation.  H2.2.1.2pSOH application  The section overhead (SOH) is subdivided into regenerator SOH (RSOH) comprising rows 1 to 3 and multiplex SOH (MSOH) comprising rows 59. The MSOH is accessible only at terminal equipments, whereas the RSOH is accessible at both terminal equipments and regenerators.  Details of the functions provided by RSOH and MSOH are given in Recommendation G.708. These functions include performance monitoring and section maintenance and operations functions.  H  In order to permit regenerators to read from and write to the RSOH without disrupting the primary performance monitoring, the RSOH is excluded from the B2 (BIP24) calculation. Since B1 is recomputed at each regenerator, fault sectionalization is simplified.  H  The set of bytes E1, E2, F1 and D1 to D12 is referred to as the network operators maintenance channel (NOMC).  H2.2.1.3pProtection of the Network operators maintenance channel (NOMC)  H  In a 1+1 protection system, the NOMC will be on both channels. In a 1:n protection system, the NOMC will be on only one channel, normally channel 1. If channel 1 fails, the NOMC will be switched to the protection channel, along with traffic.  H   It should be noted that failure of channel 1 will result in the loss of the NOMC under the following conditions:  H   i)pthe protection channel is carrying extra traffic and a FORCED switch is in operation;   ii)pthe protection channel is LOCKED OUT.  H  Loss of the NOMC under conditions i) and ii) above, and in the case of diversely routed protection spans, requires further study.  Bytes K1 and K2 shall be transmitted on the protection channel. In addition, they may also be transmitted on working channels. The receiver must be able to ignore bytes K1 and K2 on any of the working channels.  H2.2.1.4pMaintenance signals  H  The maintenance signals defined in Recommendation G.709 S2.3.1 at the section layer are section AIS and far end receive failure (FERF). At the path layer, Recommendation G.709 S2.3.2 defines path AIS and path status information in the form of path FERF and far end block error (FEBE). These path maintenance signals apply at both higher order and lower order path level. Figure 22/G.782 illustrates the layertolayer and peertopeer maintenance interaction provided in the SDH overhead. 2.2.1.5pLoss of signal at regenerators  H  If a regenerator loses its input signal, a standby clock is activated and a signal containing valid RSOH and MSAIS is transmitted downstream. This enables the NOMC functions carried by the RSOH to be activated if required.  H2.2.2 TMN access  H  SDH multiplexers should provide interfaces for messages to or from the TMN via either the DCC or a Qinterface or both. Messages arriving at the interface not addressed to the local multiplex should be relayed to the appropriate Q or DCC interface. The TMN can thus be provided with a direct logical link to any SDH equipment via a single Q interface and the interconnecting DCCs. M c4 P Figure 22/G.782 = 22 cm  c4 P   H2.2.2.1pQ interface  H  When access to the TMN is provided by a Qinterface, the interface will conform to RecommendationG.773. A choice has to be made between the B1, B2 and B3 protocol suites specified in that Recommendation.  H2.2.2.2pData communications channel (DCC)  The use of the DCC is dependent on the network operator's maintenance strategy and the specific situation. It may not always be required as it is possible to carry out the required functions by other means.  There are two ways of using the DCC:  H   i)puse of the D1 to D3 bytes located in the RSOH (DCC c4 P R c4 P ) and accessible at regenerators and other NEs;  Hx   ii)puse of the D4 to D12 bytes located in the MSOH (DCC c4 P M c4 P ) and not accessible at regenerators. The specific use of the D4 to D12 bytes is for further study.  H  These channels are message based and provide communications between network elements. They can be used to support communications between sites and the TMN. Two examples are given in Figures 23/G.782 and2-4/G.782. N c4 P Figure 23/G.782= 10 cm  c4 P  M c4 P Figure 24/G.782 = 13 cm  c4 P   H2.2.2.3pFunctionalities  H2.2.2.3.1pSynchronous equipment management function (SEMF)  H  This converts performance data and implementation specific hardware alarms into objectoriented messages for transmission on the DCC(s) and/or a Qinterface. It also converts objectoriented messages related to other management functions for passing across the Sn reference points.  H2.2.2.3.2pMessage communications function (MCF)  This function receives and buffers messages from the DCC(s), Qand Finterfaces and SEMF. Messages not addressed to the local site are relayed to one or more outgoing DCC(s) in accordance with local routing procedures and/or Qinterface(s). The function provides layer 1 (and layer 2 in some cases) translation between a DCC and a Q-interface or another DCC interface.  2.2.3 Orderwire  H  Use of the E1 and/or E2 bytes for providing an orderwire is optional. Byte E1 can be accessed at all regenerators and terminals to provide a  H local orderwire. Byte E2 can only be accessed at terminals and may be used to provide an orderwire between terminal sites.  H2.2.4 User channel  H  Use of the F1 byte for providing a special user channel is optional. Byte F1 can be accessed at all regenerators and terminals. 2.3h  STMN protection switching  H  Protection switching of a signal provides a capability, using equipment redundancy and switching action, such that in the event of the failure of a "working" channel, the signal is available via a protection channel.  H   The use of protection switching is dependent on the network operator's maintenance strategy. It may not always be required. If required on SDH  H line systems, redundancy is provided for functions and physical medium between, and including, two MST functions, i.e. for the multiplex section. Thus, the Multiplex Section Protection (MSP) function included in multiplexing equipment provides protection for the STMN signal against failures within a multiplex section.  H  The MSP function communicates with the corresponding far end MSP function to coordinate the switch action, via a bitoriented protocol defined for the K bytes of the MSOH. It also communicates with the SEMF for automatic and manual switch control. Automatic protection switching is initiated based on the condition of the received signals. Manual protection switching provides both local and remote switching from commands received via the SEMF. The details of switch initiation, control and operation are described in Recommendation G.783.  H2.3.1 MSP architectures  H  Two MSP architectures are defined: 1+1 (one plus one) and 1:n (one forn).  H2.3.1.1p1+1 architecture  H  In a 1+1 MSP architecture shown in Figure 25/G.782, the STMN signal is transmitted simultaneously on both multiplex sections, designated working and protection sections; i.e. the STMN signal is permanently connected (bridged) to the working and protection sections at the transmitting end. The MSP function at the receiving end monitors the condition of the STMN signals received from both sections and connects (selects) the appropriate signal. Due to permanent bridging of the working channel, the 1+1 architecture does not allow an unprotected extra traffic channel to be provided. c4 P  MFigure 25/G.782= 4,5 cm  c4 P  2.3.1.2p1:n architecture  In a 1:n MSP architecture shown in Figure 26/G.782, the protection section is shared by a number of working channels; the permitted values for n are 1 through 14. At both ends, any one of the n STMN channels or an extra traffic channel (or possibly a test signal) is bridged to the protection section. The MSP functions monitor and evaluate the conditions of the received signals and perform bridging and selection of the appropriate STMN signals from the protection section.  H  Note that 1:1 architecture is a subset of 1:n (n=1) and may have the capability to operate as 1+1 for interworking with a 1+1 architecture at the other end.  H2.3.2 Operation modes  H  The MSP may operate either bidirectionally or unidirectionally and in either a revertive or nonrevertive mode, depending on the network management.  H  In bidirectional operation, the channel is switched to the protection section in both directions, and switching of only one direction is not allowed. In unidirectional operation, the switching is complete when the channel in the failed direction is switched to protection.  H  In revertive mode of operation, the working channel is switched back to the working section, i.e. restored, when the working section has recovered from failure. In nonrevertive mode of operation, the switch is maintained even after recovery from failure. For 1:n architectures, only revertive mode is allowed. 2.4h  Integrated interfaces  H  Section 3 describes multiplexer configurations for multiplexer functions that may be integrated with the line terminating function. It is envisaged that such direct SDH interfaces will also be provided on other network elements such as digital crossconnects or digital switches. These interfaces may be either intrastation or interstation. L c4 P Figure 26/G.782 = 10,5 cm  c4 P  3X Multiplexing equipment types  This section provides some examples of equipment configurations and network applications for SDH equipment, based on the generalized multiplexer logical block diagram (Figure 21/G.782). The description of these examples is generic and no particular physical partitioning of functions is implied. The examples are not a complete set; other configurations may be useful in other network applications. 3.1h  Type I (Figure 31/G.782)  H  This provides a simple G.703 to STMN multiplex function. For example, 632048 kbit/s signals could be multiplexed to form an STM1 output or, 1244736 kbit/s signals could be multiplexed to form an STM4. The location  H of each of the tributary signals in the aggregate signal is fixed and dependent on the multiplex structure chosen. 3.2h  Type Ia (Figure 32/G.782)  H  The ability to provide flexible assignment of an input to any position in the STMN frame can be provided by including a VC1/2 and/or VC3/4 path connection function. 3.3h  Type II (Figure 33/G.782)  This provides the ability to combine a number of STMN signals into a single STMM signal. For example, four STM1 signals (from multiplexers or line systems) could be multiplexed to provide a single STM4 signal. The location of each of the VC3/4s of the STMN signals is fixed in the aggregate STMM signal.  3.4pType IIa (Figure 34/G.782)  H  The ability to assign flexibly a VC3/4 on one STMN to any position in the STMM frame can be provided by including a VC3/4 path connection function. 3.5h  Types IIIa and IIIb  H  These provide the ability to access any of the constituent signals within an STMN signal without demultiplexing and terminating the complete signal. The interface provided for the accessed signal could be either according to G.703 or an STMM (M