C:\WINWORD\CCITTREC.DOT_______________ Recommendation G.773 Recommendation G.773 PROTOCOL SUITES FOR Q-INTERFACES FOR MANAGEMENT OF TRANSMISSION SYSTEMS 1 Introduction 1.1 Scope This Recommendation defines the characteristics of protocol suites for Q-interfaces of transmission systems/equipments, as defined in Recom- mendations M.30 [1] and G.771 [58]. Protocol suites for Q-interfaces of other systems/equipments will be specified in other Recommendations. The interfaces will support bidirectional data transfer for the management of telecommunications systems. This Recommendation defines: – the layer services; – the layer protocols; – the application service elements and protocols; – the conformance requirements to be met by an implementation of these interfaces. This Recommendation does not define: – the structure or meaning of the management information that is transmitted by means of the protocol suites; – the manner in which management is accomplished as a result of the application protocol exchanges; – the interactions which result in the use of the application layer proto- cols. 1.2 Abbreviations and symbols 1.2.1 Abbreviations AARE A-associate responseaare a-associate response AARQ A-associate request ACSE Association control service element AFI Authority and format identifier APDU Application protocol data unit ASE Application Service element ASN.1 Abstract syntax notation one CD Collision detection CDO Connect data overflow CLNS Connectionless-mode network service CMIP Common management information protocol CMIS Common management information service CMISE Common management information service element Conf Confirm CONS Connection oriented-mode network service CSMA Carrier sense multiple access DCE Data circuit terminating equipment DCN Data communication network DIS Draft international standard DLC Data link connection DLS Data link service DSP Domain specific part DTE Data terminal equipment EOC Embedded operations channel FU Functional unit HDLC High-level data link control IDI Initial domain identifier IDP Initial domain part Ind Indication ISO International organization for standardization LCN Local communication network LLC Logical link control LME Layer management entity MAC Media access control MD Mediation device NDM Normal disconnected mode NE Network element NLR Network layer relay NM-ASE Network management-application service element NRM Normal response mode NRZ Non return to zero NRZI Non return to zero inverted NS Network service NSAP Network service access point OA Overflow accept OS Operations system OSI Open systems interconnection PDU Protocol data unit PhC Physical connection Ph Physical PhS Physical service PICS Protocol implementation conformance statement PLS Physical layer service PPDU Presentation protocol data unit PV Parameter value PVC Permanent virtual circuit PU Protocol unit QOS Quality of service Req Request Res Response ROSE Remote operations service element SDH Synchronous digital hierarchy SP Session protocol SPDU Session protocol data unit SPF Segmentation permitted flag SVC Switched virtual circuit 1) TMN Telecommunications management network TPDU Transport protocol data unit TSAP Transport service access point UNC Unbalanced operation normal response mode class 1.2.2 Symbols and abbreviations used in tables 2) M Mandatory – The parameter is not present in the interaction described by the ser- vice or primitive concerned. (=) The value of the parameter is equal to the value of the parameter in the column to the left. 2 Protocol suites overview 2.1 Introduction RecommendationG.771 [58] provides guidance for the selection of protocol suites from RecommendationG.773 and the domain of application of these standard protocol suites. The structures of the protocol suites with the present layers are shown in Figure1/G.773. The defined communication services and protocols are in accordance with the Open System Interconnection (OSI) reference model[2]. The protocols for the different layers are based on Recommendations and/or ISO standards. Two types of protocol suites are defined in this Recommendation: – short stack: protocol suitesA1 and A2, – full 7layer stack: protocol suitesB1, B2 and B3. The short stack protocol suites (A1 and A2) will be used mainly for LCNapplication as specified in RecommendationM.30[1]. The full 7layer stack protocol suites (B1, B2 and B3) can be applied to both LCN and DCNapplications, as defined by Recommendation M.30[1]. Because of the nulling of the transport layer, session layer and presentation layer for short stack protocol suites, mapping functions have been defined. The full 7layer protocol suites satisfy the requirements of complex NEs (e.g. equipments for the SDH). To support already existing networks and to provide maximum flexibility, several possibilities are defined for layers1, 2 and 3. Each Administration should select depending on its own specific requirements and needs. Layers5, 6 and 7 are identical for the three proto- col suitesB1, B2 and B3, whilst almost identical requirements apply to layer4. 3 Protocol suitesA1 and A2 3.1 Physical layer 3.1.1 Physical layer for A1 3.1.1.1 Service 3.1.1.1.1 Definition The service definition for the physical layer is in accordance with RecommendationX.211[3]. The following classes of physical services shall be supported: – type of transmission is synchronous; – mode of operation is half-duplex; – topology is point-to-multipoint by a bus. Figure 1/G.773 = 22 cm 3.1.1.1.2 Service provided by the physical layer The physical layer provides the physical service primitives and parameters as listed in Table1/G.773. The services PhC-Activation and PhC-Deactivation will be provided to the Layer Management Entity (LME) of the physical layer. 3.1.1.2 Physical interface 3.1.1.2.1 Physical characteristics 3.1.1.2.1.1 Configuration Serial bus operation in accordance with ISO8482 3) [4], in half-duplex mode. 3.1.1.2.1.2 Transmission pairs Two screened balanced pairs, one for each direction of transmission. 3.1.1.2.1.3 Connector The Administration shall specify the connector type. 3.1.1.2.2 Electrical characteristics 3.1.1.2.2.1 Static and dynamic characteristics The static and dynamic characteristics of each bus connection shall be in accordance with ISO8482[4]. When all generators connected to the bus are in the high impedance state, the bus shall be set to logical level“1”. 3.1.1.2.2.2 Bus termination Each bus end shall be terminated in accordance with ISO8482[4]. 3.1.1.2.2.3 Load connection Each receiver shall present a maximum of one unit load, as defined in ISO8482[4], to the bus. The number of load connections is limited to 32. 3.1.1.2.2.4 Bit rate The bit rate shall be 19200bit/s or 64000bit/s. A bit rate of 128000bit/s may be necessary in some applications. The bit rate tolerance shall be ±0.05%. 3.1.1.2.2.5 Turn-off time For bit rates of 19200bit/s and 64000bit/s a transmitting station shall put its generator in the high impedance state within 0.750ms from the end of the last bit of the closing flag. For a bit rate of 128000bit/s the turn- off time shall be not more than 0.375ms. This point is not applicable to a primary station (see §3.2.1.2.1.3). 3.1.1.2.2.6 Switch-on transient Following the enabling of the generator an implementation dependent preamble of no more than 4bit times is allowed. No assumption as to the state of the bus during this preamble is allowed. 3.1.1.2.3 Line code The line code shall be NRZI. 3.1.1.2.3.1 Principle Each ISO8482 [4] transition shall represent a ZERO, and no transi- tion shall represent a ONE bit. 3.1.1.2.3.2 Lock in sequence Where required for clock extraction, it shall be possible to send a lock in sequence containing at least four transitions immediately prior to the beginning of the starting flag of the frame to be transmitted. 3.1.1.2.4 Extended mode An example of extended mode is given in AnnexA. 3.1.2 Physical layer for A2 3.1.2.1 Overview Protocol suite A2 employs local area network technology for the physical and data link layers. Administrations will select the appropriate physical medium, e.g. coaxial cable, screened pairs, optical fibre according to technological and operational requirements. 3.1.2.2 Service 3.1.2.2.1 Definition The service definition for the physical layer shall comply with that specified in clause6 of ISO8802-3[20]. 3.1.2.2.2 Service provided by the physical layer All of the primitives defined and listed in Table2/G.773 are manda- tory. 3.1.2.3 Bit rate The bit rate will be 1Mbit/s or higher. 3.2 Data link layer 3.2.1 Data link layer for A1 3.2.1.1 Service 3.2.1.1.1 Definition The service definition of the data link layer is in accordance with RecommendationX.212[5]. The class of data link service that shall be pro- vided by the data link layer is: – a connection-mode service. 3.2.1.1.2 Service required from the physical layer The data link layer requires the Data Transfer service from the physi- cal layer. 3.2.1.1.3 Service provided by the data link layer The data link layer shall provide the Data Link service, primitives and parameters as listed in Tables3/G.773 to 5/G.773. 3.2.1.1.3.1 DLC-Establishment 3.2.1.1.3.2 DLC-Release 3.2.1.1.3.3 Normal Data Transfer 3.2.1.2 Data link protocol The data link protocol is synchronous HDLC type. 3.2.1.2.1 HDLC frame structure The HDLC frame structure shall conform to ISO3309 (frame structure)[6]. 3.2.1.2.1.1 Addressing field The addressing field shall be one octet. 3.2.1.2.1.2 Information field The information field in any HDLC frame shall be an integral number ofoctets. Information field octets shall be sent least significant bit first. The maximum length of the information field shall be 256octets. 3.2.1.2.1.3 Interframe time fill A primary station shall transmit contiguous flags as interframe time fill. 3.2.1.2.2 Addressing The secondary station shall be capable of being assigned any address in the range1 to 254. 3.2.1.2.2.1 All station address The address field pattern “11111111” is defined as the all-station address. 3.2.1.2.2.2 No-stationaddress The address field pattern “00000000” is defined as the no-station address. The no-station address shall never be assigned to a secondary sta- tion. 3.2.1.2.2.3 Group addresses Not used. 3.2.1.2.3 HDLC procedure The HDLC procedure is defined in ISO4335[7]. 3.2.1.2.3.1 Commands and response The following HDLC commands and responses must be supported: – commands SNRM: Set normal response mode DISC: Disconnect – commands or responses I: Information RR: Receive ready RNR: Receive not ready – responses FRMR: Frame reject UA: Unnumbered acknowledgement DM: Disconnect mode 3.2.1.2.3.2 Modes Two modes are selected: – one operational mode: normal response mode (NRM); – one non-operational mode: normal disconnected mode (NDM). 3.2.1.2.4 Class of procedure The unbalanced operation normal response mode class (UNC) as defined in ISO7809[8] shall be implemented. 3.2.1.2.4.1 HDLC optional functions The following HDLC optional functions shall be implemented: – unnumbered information (option No.4); – data link test (option No.12). 3.2.1.2.5 Other parameters of data link layer 3.2.1.2.5.1 Window size The window size for unacknowledged frames is to be optional between1 and7. The default value is 1. 3.2.1.2.5.2 Waiting-time before a repetition In the case of no-reply or lost-reply, the primary station shall provide a waiting time function. The waiting-time before a repetition shall be greater than the duration of the longest frame to be sent by the primary station, added to the response-time of the secondary station and the duration of the longest frame to be sent by the secondary station. 3.2.1.2.5.3 Number of repetitions Under the conditions described in § 3.2.1.2.5.2, the maximum number of repetition before detecting a no-reply or a lost-reply condition is fixed to 5(6requests). 3.2.1.2.5.4 Response time The secondary station shall commence the opening flag of its response not later than 5ms after the end of the closing flag of the frame sent from the primary station. 3.2.2 Data link layer for A2 3.2.2.1 Overview The data link layer provides the acknowledged connectionless-mode service. The access method employed is Carrier Sense Multiple Access with Collision Detection (CSMA/CD). 3.2.2.2 Media access control (MAC) 3.2.2.2.1 The services and protocol of the CSMA/CD access method shall comply with those specified in ISO8802-3[20]. 3.2.2.2.2 The address length used at the MAC sublayer shall be 48bits. 3.2.2.3 Logical link control (LLC) 3.2.2.3.1 The definition of the acknowledged connectionless mode LLCservice shall comply with that specified in ISO8802-2/DAD2[23]. All of the primitives defined for type3 operation (Table6/G.773) are man- datory. 3.2.2.3.2 The protocol used to provide the acknowledged connectionless- mode LLCservice shall be as specified in ISO8802-2[22] and ISO8802/ DAD2[23]. All of the commands and responses defined for type3 opera- tion (Table7/G.773) are mandatory. 3.3 Network layer for A1 and A2 3.3.1 Service 3.3.1.1 Service definition The definition of the connectionless-mode network service shall com- ply with that specified in ISO8348/AD1[9]. Address formats supported shall conform to ISO8348/AD2[10]. 3.3.1.2 Service required from the data link layer The network layer requires the Normal Data Transfer service from the data link layer. 3.3.1.3 Service provided by the network layer The network layer shall provide the N-UNITDATA service as listed in Table8/G.773. 3.3.2 Network protocol 3.3.2.1 General The Network protocol is as specified in ISO8473 [11]. The sub-net- work dependent convergence function required for protocol suite A1 is specified in ISO8473/AD3[19]. ISO8473 [11] defines in addition to the full protocol (see §3.3.2.4), two subsets namely: – inactive network layer protocol (see § 3.3.2.2), – non-segmenting network layer protocol (see § 3.3.2.3). The address part shall have the structure as defined in ISO 8348/AD2 [10]. For protocol suite A1 the Authority and Format Identifier (AFI) shall be set to 49, coded by 2 decimal digits as defined in ISO 8348/AD2 [10], which specifies “local” and binary coding of the Domain Specific Part (DSP). For protocol suite A2 the authority and format identifier (AFI) shall be set to 38, 39, 48 or 49, coded by two decimal digits as defined in ISO8348/AD2 [10], which means ISO Data Country Code (ISODCC) and decimal coding of domain specific part (DSP), ISO DCC and binary coding of DSP, “local” and decimal coding of DSP, or “local” and binary coding of DSP, respec- tively. The full protocol and the two subsets permit the use of known sub-network characteristics and are therefore not sub-network independent. Depending on the required usage and the sub-network architecture the full protocol, or one or both subsets, shall be supported by protocol suiteA. The selection shall be put in the Protocol Implementation Conformance State- ment (PICS). 3.3.2.2 Inactive network layer protocol The protocol shall be in accordance with the inactive subset of the protocol as defined in ISO8473[11]. 3.3.2.3 Non-segmenting network layer protocol The protocol shall be in accordance with category type1 functions of the non-segmenting subset of the protocol as defined in ISO8473[11]. From the optional functions (type3) defined in the non-segmenting subset only the “priority function” shall be supported as defined in ISO8473 [11]. 3.3.2.4 Full network layer protocol The full protocol subset of category type1 functions, as specified in ISO8473 [11], shall be supported. An implementation shall not transmit PDUs encoded using the inac- tive subset. Received PDUs encoded using the inactive subset will be dis- carded. An implementation shall not generate data PDUs without a segmenta- tion part, i.e. the Segmentation Permitted Flag (SPF) shall be set to 1 and the segmentation part shall be included. However, an implementation shall be capable of receiving and correctly processing PDUs which do not contain the segmentation part. 3.4 Mapping functions for A1 and A2 3.4.1 Introduction No transport layer, session layer and presentation layer will be speci- fied for protocol suites A1 and A2. To provide the required service to the application layer and using the provided service of the network layer a mapping function is defined. No protocol for the mapping function is defined. 3.4.2 Service 3.4.2.1 Service definition The service definition of the mapping function, which provides the required presentation service to the application layer, shall be in accordance with RecommendationX.216[12]. 3.4.2.2 Service required from network layer The mapping function requires the N-UNITDATA as the connection- less-mode network service. 3.4.2.3 Service provided by the mapping function The mapping function shall provide the presentation service as listed in Table9/G.773. When ACSE is supported in the application layer the mapping function shall also provide the presentation services P-CONNECT, P-RELEASE, P- U-ABORT and P-P-ABORT. Only the parameters defined as mandatory in RecommendationX.216[12] shall be supported. The value of the Mode parameter of P-CONNECT shall be “normal”. 3.4.3 Procedure The mapping function will provide the values for the source address, destination address, QOS and NS-User data as required by the network ser- vice parameters. The mapping function will translate the presentation addresses to the Network-Service-Access-Point (NSAP) addresses and vice versa. It will provide the value of the quality of service parameter of N- UNITDATA Request. The NS-User data will be provided by the User data of P-DATA and vice versa. Note – This is not a mapping protocol. While the service description of this function is standard, the implementation itself needs not to be stan- dardized. 3.5 Application layer for A1 and A2 3.5.1 Overview The network management application layer shall provide the CMISE service to the NM-ASE. The required application service elements for this service are Com- mon Management Information Service Element (CMISE) and Remote Operations Service Element (ROSE). Some applications may require the addition of the Association Control Service Element (ACSE). 3.5.2 Syntax and encoding The application layer protocol data unit presentation is described by using Abstract Syntax Notation One (ASN.1), as defined in RecommendationX.208 [15] and is encoded in accordance with the basic encoding rules for ASN.1, as defined in RecommendationX.209[16]. 3.5.3 Association control 3.5.3.1 The ACSE service description is detailed in RecommendationX.217[25]. When the ACSE is used all of the defined ACSE services (Table10/G.773) are mandatory. The value of mode param- eter of A-ASSOCIATE shall be “normal”. 3.5.3.2 The protocol specification for ACSE shall follow RecommendationX.227[26]. When the ACSE is used all five APDUs (see Table10/G.773) specified in the standard are mandatory. The value of pro- tocol version field of AARQ and AARE shall be version1 only. 3.5.4 Remote operations 3.5.4.1 The remote operations service element (ROSE) shall be a mandatory service element for the protocol suitesA1 and A2. The ROSE service description is detailed in RecommendationX.219[14]. All of the defined ROSE services (Table11/G.773) are mandatory. 3.5.4.2 The protocol specification for ROSE shall follow RecommendationX.229[18]. All four APDUs specified in the standard (see Table11/G.773) are mandatory. In addition, the ability to support cor- rect origination and reception of the linked-ID protocol element is required for protocol suites A1 and A2. The requirement specified in Table11/G.773 implies association class3 in ROSE. 3.5.5 Common management information 3.5.5.1 The common management information service element (CMISE) shall be a mandatory service element for the protocol suitesA1 and A2. The CMISE service description is detailed in ISO9595[13], ISO9595/ DAD1[27] and ISO9595/DAD2[28]. The CMISE services are listed in Table12/G.773. 3.5.5.2 The protocol specification for CMISE shall follow ISO9596[17], ISO9596/DAD1[29] and ISO9596/DAD2[30]. 3.6 Conformance For further study. 4 Protocol suitesB1, B2 and B3 4.1 Physical layer 4.1.1 Physical layer for B1 and B2 4.1.1.1 Protocol The protocol of the physical layer of protocol suites B1 and B2 shall comply with the following specifications: – X.21 interface in accordance with § 1.1 of RecommendationX.25[39]; – X.21 bis interface in accordance with § 1.2 of Recommendation X.25 [39]; – V-Series interface in accordance with § 1.3 of RecommendationX.25 [39]. 4.1.1.2 Bit rate The supported bit rates are: 1200, 2400, 4800, 9600, 19200 and 64000bit/s. The bit rates 48000 bit/s and 56000bit/s may be used for an interim period (see notea) to Table19b/G.773). 4.1.1.3 Connector Table 13/G.773 lists the connectors to be used in accessing the X.21[61] and X.21bis[62] interfaces. Tables14/G.773, 15/G.773 and 16/ G.773 list respectively the pin descriptions of ISO2110 [37], ISO2593 [38], ISO4902[24] and ISO4903 [63]. 4.1.2 Physical layer for B3 4.1.2.1 Overview Protocol suiteB3 employs local area network technology for the physical and data link layers. Administrations will select the appropriate physical medium, e.g. coaxial cable, screened pairs, optical fibre according to technological and operational requirements. 4.1.2.2 Service The service definition for the physical layer shall comply with that specified in clause6 of ISO8802-3[20]. All of the primitives defined and listed in Table 17/G.773 are manda- tory. 4.1.2.3 Bit rate The possible bit rate will be 1Mbit/s, 10Mbit/s or higher. 4.2 Data link layer 4.2.1 Data link layer for B1 and B2 It is mandatory that the data link layer conforms to LAPB as defined in RecommendationX.25[39]. In addition, provision shall be made for con- nection between data terminal equipments without an intervening packet switched network. The interface shall conform to ISO7776[40]. Further detail is provided in §4.2.1.1. The following link layer specification applies to all cases. 4.2.1.1 Equipment type during link set-up and reset When a packet switched network is used to connect systems, they are each designated Data Terminal Equipment (DTE) and the network acts as a Data Circuit-Terminating Equipment (DCE). When a dedicated or dial-up link is provided, other means must be used to supply the DCE role. At the physical layer, the modems will provide the DCE interface, supplying bit synchronization. At the link level, the procedures specified in ISO7776[40] shall be followed. A system must be able to start the set-up or reset of the link (a DCEfunction in RecommendationX.25 [39]). In addition, provision must be made for assignments of the A/B addresses. This mandatory option is to be field-settable and stored in non-volatile memory. Equipment which meets this requirement is compatible with connection to either a DCE or remote DTE. 4.2.1.2 Window Modulo 8 operation shall be used. Support of modulo128 is optional. The window for unacknowledged frames is to be optional between 1 and 7 frames and 1 to 127 with modulo128. The standard default is 7. 4.2.1.3 User information The user information is to be arranged in an integral number of octets. The maximum length of the user information shall be user settable, consistent with the range of values for the N1 parameter as shown in Table18/G.773. Maximum information field lengths that shall be supported are 131 and 259octets with optionally 515, 1027, 2051 or 4099 octets. These values provide for three packet header octets and maximum length of packet data units of 128, 256, 512, 1024, 2048 and 4096 octets, respectively. 4.2.1.4 Other frame parameters Certain other frame parameters shall be set by the user to be consis- tent with the bit rate, frame size and characteristics of the connecting net- work. A system design should be sufficiently flexible to accommodate parameter sets for diverse networks, both as order options and later recon- figurations. The range of parameters is shown in Table18/G.773. These options, like those of the physical layer, are to be set at installation, change- able by the user, and non-volatile. 4.2.2 Data link layer for B3 4.2.2.1 Overview The data link layer provides the unacknowledged connectionless- mode service. The access method employed is carrier sense multiple access with collision detection (CSMA/CD). 4.2.2.2 Media access control (MAC) The services and protocol of the CSMA/CD access method shall com- ply with those specified in ISO8802-3[20]. The address length used at the MAC sublayer shall be 48bits. 4.2.2.3 Logical link control (LLC) The definition of the unacknowledged connectionless-mode LLC ser- vice shall comply with that specified in ISO8802-2[22]. All of the primi- tives defined for type1 operation shall be supported. The protocol used to provide the unacknowledged connectionless- mode LLCservice shall be as specified in ISO8802-2[22]. All of the com- mands and responses defined for type1 operation shall be supported. 4.3 Network layer 4.3.1 Network layer for B1 It is mandatory that the packet layer conforms to RecommendationX.25[39]. In addition, the packet layer must provide for connection of data terminal equipment without an intervening packet net- work; the required interface for this purpose conforms to ISO8208[41]. In addition, the provisions of RecommendationX.223[42] shall apply. The attributes which must be supported are summarized in Tables19a/G.773 and 19b/G.773. Note in particular that these tables show the different attributes needed to support PVCs (the X.25/PVC [39] proce- dures) and SVCs(the X.25/SVC [39] procedures). 4.3.1.1 Equipment type during restart When the packet level X.25 [39] interface is used, automatic selection of the DCE/DTE role during restart is required, as specified in ISO8208[41]. 4.3.1.2 Other features and parameters The packet layer attributes are summarized in Tables19a/G.773 and 19b/G.773. 4.3.1.3 Expedited data negotiation The initiator shall be capable of proposing the non-use of the Expe- dited Data service. Responders shall be capable of receiving requests for the Expedited Data service, but shall be capable of responding with non-use of the service. The Expedited Data service is neither required nor precluded by this Recommendation. 4.3.1.4 Receipt confirmation negotiation The initiator shall be capable of setting bit7 of the general format identifier to 0. Responders shall be capable of receiving bit7 set to 1, but shall be capable of responding with bit7 set to 0. The Receipt Confirmation service is neither required nor precluded by this Recommendation. 4.3.1.5 Throughput class When the end system requires only one network layer connection on a physical access port, support of throughput classes up to the access line transmission rate is required. When multiple network layer connections are required, support of the throughput class equal to the access line transmis- sion rate is optional. Further study of throughput class range and default val- ues at various access line rates is needed. 4.3.1.6 Packet size negotiation Interoperability is achieved by having the initiator propose a packet size from the set specified in Tables19a/G.773 and 19b/G.773, and by the responder selecting the most appropriate packet size between 128 and the proposed packet size. The rules for negotiation of the size of the packet to be used in a given instance of communication are specified in ISO8208[41]. The choice of packet size is a local issue which can depend on, for example, the quality of service requested or needed by the user or applica- tion and the sub-network characteristics. 4.3.1.7 User data field When layers above X.25 [39] are used, the initial octets of a DATA primitive and the corresponding data transfer packet are used for peer-to- peer protocol data for those layers. In following the procedures of Recommendation X.244[43], ISODTR9577[44], AnnexB of RecommendationX.224 [49] and ISO8073/AD1[45], the initial octets of the user data field of the call request packet may only be used for protocol identification. For those cases in which the fast select feature is used, the call request packet may contain a call user data field of up to 128octets. 4.3.1.8 Numbering plans To support communications over public networks, public numbering plans may be used on the packet-switched network between OSs/MDs and NEs. The RecommendationsE.164[21] and X.121[46] specify public numbering plans. Equipment may be assigned numbers in accordance with either of these international Recommendations. The escape code values of “0” and “9” shall be supported as specified in Table2/X.121 of RecommendationX.121 [46]. Where a public numbering plan is not neces- sary, a private numbering plan may be used. 4.3.1.9 Addressing Network layer addressing as specified in Recommendation X.213, AnnexA[47] and ISO8348/AD2[10] shall be supported. 4.3.2 Network layer for B2 4.3.2.1 Protocol The protocols for the network layer shall be identical to the network layer protocol of protocol suite B1 (see§4.3.1) with the inclusion of ISO8473[11] as specified in ISO8880/3[59] §3, to provide the connec- tionless-mode network service over the connection-mode network service. For those instances of communication requiring interworking between a Connection Oriented Service (CONS) and a Connectionless- mode Network Service (CLNS), ISODTR10172[60] provides an ISO compatible interworking capability. This capability is known as a Network Layer Relay (NLR) and utilizes the ISO8473[11] protocol to provide this service. 4.3.2.2 Network layer attributes Characteristics of the connectionless-mode network layer service, and the connectionless-mode network layer protocol shall be as shown in Table20/G.773. 4.3.3 Network layer for B3 4.3.3.1 Service The definition of the connectionless-mode network service shall com- ply with that specified in ISO8348/AD1[9]. Address formats supported shall conform to ISO8348/AD2[10]. The network layer shall provide the N-UNITDATA service as speci- fied in ISO8348/AD1[9]. 4.3.3.2 Protocol The protocol shall be in accordance with the full protocol subset of category type1 functions, as specified in ISO8473[11]. 4.3.3.3 Network layer attributes Characteristics of the connectionless-mode network layer service and the connectionless-mode network layer protocol shall be as shown in Table20/G.773. 4.4 Transport layer 4.4.1 Transport layer for B1 It is mandatory that for the connection-oriented network service, the transport layer shall conform to RecommendationsX.214[48] and X.224[49] and to those provisions of ISO8072[50] and 8073[51] that apply to the use of the Connection-Oriented Network Service (CONS). 4.4.1.1 Class of service Classes4, 2 and 0 shall be supported as shown in Table21/G.773 in countries requiring the features of transport layer class4. The conformance rules of Recommendation X.224[49] require that classes0 and 2 be sup- ported as well when class4 is specified. In addition to the requirements specified in RecommendationX.224[49], equipment shall meet the following requirement: if a responder receives an alternate class of “none”, it shall respond with the preferred class. Rules for responders are specified in Table22a/G.773. Acceptance rules for initiators are specified in Table22b/G.773. User options shall be provided to designate the preferred and alternate classes (see Table3 of RecommendationX.224 [49]). When all of the classes are supported, the preferred class for connection is class4. 4.4.1.2 Protocol identification For the purpose of transport layer protocol identification, the proce- dures specified in RecommendationX.224[49] AnnexB and ISO8073/AD 1[45] shall be used. The conventions for protocol identification given in ISODTR10172[60] should be followed. Selection of codes not specified in the referenced standards is for further study. The absence of call user data in a call request or call accept packet of RecommendationX.25[39] and ISO8208[41] indicates the operation of the transport layer procedures of ISO8073[51] and RecommendationX.224[49]. 4.4.1.3 Attributes Attributes of the transport layer for use with CONS are summarized in Table21/G.773. The selection of values within required and optional ranges depends on characteristics of the messages. Note – The need to support high priority messages that require low transit delay on a given transport connection must be reflected in the quality of service parameters requested when the transport connection is estab- lished. A properly implemented transport entity should not multiplex high priority messages that require low transit delay if it cannot provide the requested quality of service. 4.4.1.4 User data in connection request and connection confirm TPDUs User data in the connection request and connection confirm TPDUs are optional in RecommendationX.224[49]. No transport service user shall send it: all protocol implementations shall be prepared to receive it and all implementations may ignore it, i.e. it shall not cause a disconnect. 4.4.1.5 Splitting Responders may refuse network connections which could impose an unnecessary restriction on the ability to establish outgoing network connec- tions. To prevent repeated ineffective attempts during splitting, initiators shall refrain from immediately requesting additional network connections for a transport connection after a network connection has been refused. The time delay before requesting additional network connections is for further study. 4.4.1.6 Quality of service negotiation Quality of service negotiation is outside the scope of this Recommen- dation. If quality of service negotiation is not supported, receipt of the parameters “throughput”, “residual error rate”, “priority” and “transit delay” in the CR and CC TPDUs shall be ignored. 4.4.1.7 TPDU size negotiation Interoperability is achieved by having the initiator propose a TPDU size from the set specified in Table21/G.773 and by the responder selecting the most appropriate TPDU size between 128 octets and the proposed TPDU size. The rules for negotiation of the size of the TPDU to be used in a given instance of communication are specified in ISO8073[51]. The choice of the TPDU size is a local implementation issue. 4.4.1.8 Class 0 error TPDU When transport class 0 has been negotiated, the error transport proto- col data unit (ER-TPDU) may be used at any time and upon receipt requires that the recipient disconnect the network connection and, by extension, the transport connection. 4.4.1.9 Negotiation of protection Negotiation of protection is outside the scope of this Recommenda- tion. If negotiation of protection is not supported, receipt of the protection parameters in any CRTPDU and any CCTPDU shall be ignored. 4.4.1.10 Unknown CR TPDU parameters An unknown parameter in any received CRTPDU shall be ignored. 4.4.1.11 Invalid values of known CR TPDU parameters Known parameters with valid lengths but with invalid values in a CRTPDU shall be handled as depicted in Table23/G.773. 4.4.1.12 Additional options parameter Unrecognized or not applicable bits of the Additional Options shall be ignored. 4.4.1.13 Code misalignment For further study. A misalignment between RecommendationX.224[49] and ISO8073[51] code values for subsequence number and flow control confir- mation has been identified. As a short-term solution, ISO8073 [51] shall apply. Subsequence number 1000 1010 Flow control confirmation 1000 1100 It is intended that when an ISO/CCITT solution to this defect is available, this Recommendation will be modified to align with the solution. 4.4.2 Transport layer for B2 and B3 4.4.2.1 Protocol Operation of the transport protocol over the connectionless-mode net- work layer service (CLNS), as described in ISO8348/AD 1[9], shall use the elements of ISO8073/AD 2[52], class4 operation over the CLNS. 4.4.2.2 Class of service Support of class4 operation of ISO8073/AD 2[52] is mandatory. 4.4.2.3 Transport layer attributes Transport layer attributes for class4 operation over the connection- less-mode network layer service shall be as shown in Table24/G.773. 4.5 Session layer for B1, B2 and B3 The session layer conforms to the service definition and protocol specification in RecommendationsX.215[53] and X.225[54] respectively. Support of version2 of the session protocol is mandatory. Two session layer functional units (FU) are required in this Recommendation: 1) Kernel 2) Duplex Restrictions applied to parameters and their values are specified in the fol- lowing sections. 4.5.1 Session protocol data units The following Session Protocol Data Units (SPDUs) associated with the Kernel and Duplex functional units shall be supported as detailed in Table25/G.733. 4.5.2 Transport expedited service The use of the Transport Expedited service is as stated in RecommendationX.225 [54]: if available, it must be used. When the Trans- port Expedited service is available, the Prepare (PR) SPDU shall be sup- ported as in RecommendationX.225 [54]. The Prepare Type parameter value in the PRSPDU, to indicate the arrival of an Abort (AB) SPDU, is ABORT. 4.5.3 Parameters All mandatory parameters defined in RecommendationX.225 [54] for the SPDUs required by the Kernel and Duplex FUs are mandatory parame- ters for this Recommendation. 4.5.4 User data The maximum length of the session user data shall be 10240octets. This restriction implies that the Overflow Accept (OA) and Connect Data Overflow (CDO) SPDUs are not required to be supported. Session-selector (s-selector) parameter values shall have a maximum length of 16octets. 4.5.5 Reuse Reuse of the transport connection is not required. The Transport Dis- connect parameter value (PV) field may be absent or set to “transport con- nection is released” in appropriate SPDUs. Furthermore, on receipt of a transport disconnect PV field indicating “transport connection is kept”, the transport connection can be released. 4.5.6 Segmentation The segmentation feature in the session layer is not required. Support for extended concatenation of SPDUs is not required. 4.5.7 Invalid SPDUs Upon receipt of an invalid SPDU, the session protocol machine shall take any action specified in §A.4.3.2 of RecommendationX.225[54] with the exception of action “d” (take no action). 4.6 Presentation layer for B1, B2 and B3 It is mandatory that the presentation layer conform to the services and protocols specified in RecommendationsX.216[12] and X.226[55] respec- tively. One presentation layer Functional Unit (FU) is required in this Rec- ommendation: Kernel The presentation protocol shall be used in the normal mode. Restric- tions applied to parameters and their values are specified in the following sections. 4.6.1 Presentation protocol units The following presentation protocol data units (PPDU) associated with the Kernel functional unit shall be supported as detailed in Table 26/ G.733. 4.6.2 Parameters All mandatory parameters defined in RecommendationX.226[55] for the above PPDUs are mandatory for this Recommendation. The “presen- tation context identifier” value shall be encoded in no more than 2octets. Also, the value(s) in the parameter presentation context definition list shall be consistent with the value(s) defined in the application-specific standards. Presentation-selector (p-selector) parameter values shall have a maximum length of 4octets. 4.6.3 Encoding rules for transfer syntax The encoding rules defined in RecommendationX.209[16] shall be applied to derive the transfer syntax for the Application Protocol Data Units (APDUs). The ASN.1 OBJECT IDENTIFIER {joint-iso-ccittasn1(1) basic-encoding (1)} shall be used as the value for the transfer syntax name. The maximum value of an ASN.1 basic encoding tag that needs to be han- dled for conformance to this Recommendation is 16383. This is the largest unsigned integer that can be represented in 14bits. Hence the identifier octets shall consist of an initial octet and up to two more octets, thus occu- pying a maximum of 3octets. Also, the largest number of octets in the “con- tents octets” component of an ASN.1 data value encoding that needs to be handled for conformance to this Recommendation is 4294967295. This is the largest unsigned integer that can be represented in 32bits. Hence in the “long form” encoding, the length octets shall consist of an initial octet and up to four more octets, thus occupying a maximum of 5octets. (Note that this restriction does not apply to “indefinite length” encodings.) 4.7 Application layer for B1, B2 and B3 It is mandatory that the application layer conforms to the architecture for the application layer outlined in ISO9545[56]. Abstract Syntax Nota- tion One (ASN.1) shall be used as the abstract syntax for specifying applica- tion protocols. 4.7.1 Supporting ASE It is mandatory that the association control service elements (ACSE) conform to the services and protocols specified in RecommendationsX.217[25] and X.227[26]. The ACSE shall establish, release and abort the associations required. The ACSE service shall operate in the “normal mode”. Network management applications shall use the common manage- ment information service element (CMISE). Services defined by CMISE that are applicable include: 1) the reporting of an event to an OS/MD; 2) the transfer of information between OSs/MDs and NEs; 3) the transer of action requests and results between OSs/MDs andNEs. 4.7.2 Application protocol data units The following application protocol data units shall be supported as detailed in Table 27/G.773. All mandatory parameters defined in RecommendationX.227[26] for the above APDUs are mandatory for this Recommendation. 4.7.3 Abstract syntax name The ACSE abstract syntax name has the ASN.1 type OBJECT IDEN- TIFIER. The following value shall be used to identify the ACSE abstract- syntax-definition: { joint-iso-ccitt association-control (2) abstract-syntax (1) apdus (0) version (1) } 4.7.4 Common management information service (CMIS) The common management information service element (CMISE) shall be a mandatory service element for the Protocol Suite B1, B2 and B3. The CMISE service description is detailed in ISO 9595 [13], ISO 9595/ DAD 1 [27] and ISO9595/DAD2[28]. Multiple object selection filter and Multiple reply functional units as defined in ISO9595[13] are optional. Their use is application dependent. The negotiation during association establishment to use or not use the Func- tional Units shall be supported. Support of the extended service functional unit defined in ISO9595[13] is not required for conformance to this Recommendation and negotiation shall be supported, at association establishment, for its non-use. 4.7.5 Common management information protocol Implementations shall support those operations defined in ISO9596[17], ISO9596/DAD1[29] and ISO9596/DAD2[30] that are required by specific applications. All mandatory parameters defined in ISO9596[17], ISO9596/DAD1[29] and ISO9596/DAD2[30] for the required operations are mandatory parameters for this Recommendation. 4.7.6 Remote operations service element (ROSE) Network Management Transaction-oriented applications shall use the following underlying service defined in RecommendationX.219[14]: – Remote operations service element (ROSE). The protocol is speci- fied in RecommendationX.229[18]. The requirement specified above implies association class3 in ROSE. 4.8 Conformance For further study. ANNEX A (to Recommendation G.773) Example of extended mode for A1 protocol suite A.1 Extended mode For those cases where it is required to extend beyond the range of the bus, one or several different capabilities may be used. For the case using modems the requirements of §§3.1.1.2.1 to 3.1.1.2.3 apply with the follow- ing exceptions: A.1.1 Configuration – Full duplex The connector shall conform to IEEE488 [31]. Appropriate signal lines are to be provided for modem control in accordance with RecommendationV.24 [32]. See TableA-1/G.773. A.1.2 Electrical requirements Data set control leads shall conform to RecommendationV.24 [32]. A.1.3 Line code NRZ line code shall be employed. A separate clock distribution shall be provided. A.1.4 Speed The bit rate shall be 9600bit/s or 64000 bit/s. Lower speeds, e.g. 1200, 2400 and 4800bit/s, may be necessary in some applications. References [1] CCITT Recommendation Principles for a telecommunications man- agement network (TMN), Vol. IV, Rec.M.30. [2] CCITT Recommendation Reference model of open system intercon- nection for CCITT applications, Vol. VIII, RecX.200 (ISO7498, 1984). [3] CCITT Recommendation Physical layer service definition of open system interconnection (OSI) for CCITT applications, Vol. VIII, Rec. X.211 (ISO 10022, 1989). [4] ISO8482 Information processing systems – Data communication – Twisted pair multipoint interconnections, 1987. [5] CCITT Recommendation Data link service definition for open system interconnection for CCITT applications, Vol. VIII, Rec.X.212 (ISO8886, 1988). [6] ISO3309 Information processing systems – Data communication – High-level data link control procedures – Frame structure, 1984. [7] ISO 4335 Information processing systems – Data communication – Consolidation of elements of procedures, 1987. [8] ISO 7809 Information processing systems – Data communication – High-level data link control procedures – Consolidation of classes of procedures, 1984. [9] ISO 8348/AD 1 Information processing systems – Data communica- tions – Network service definition; Addendum 1: Connectionless- mode transmission, 1987. [10] ISO 8348/AD 2 Information processing systems – Data communica- tions – Network service definition; Addendum 2: Network layer addressing, 1988. [11] ISO 8473 Information processing systems – Data communications – Protocol for providing the connectionless-mode network service, 1988. [12] CCITT Recommendation Presentation service definition for open sys- tem interconnection for CCITT applications, Vol. VIII, Rec. X.216 (ISO8822, 1987). [13] ISO9595 Information processing systems – Open systems intercon- nection – Common management information service definition (CMIS), 1990. [14] CCITT Recommendation Remote operations: model, notation and service definition, Vol. VIII, Rec.X.219, (ISO9072-1, 1988). [15] CCITT Recommendation Specification of abstract syntax notation one (ASN.1), Vol. VIII, Rec.X.208 (ISO8824, 1987). [16] CCITT Recommendation Specification of basic encoding rules for abstract syntax notation one (ASN.1), Vol. VIII, Rec.X.209 (ISO8825, 1987). [17] ISO9596 Information processing systems – Open systems intercon- nection – Common management information protocol specification (CMIP), 1990. [18] CCITT Recommendation Remote operations: protocols specification, Vol. VIII, Rec.X.229. [19] ISO8473/AD 3 Information processing systems – Data communica- tions – Protocol for providing the connectionless-mode network ser- vice; Addendum 3: Provision of the underlying service assumed by ISO8473 over sub-networks which provide the OSI data link service, 1988. [20] ISO 8802-3 Information processing systems – Local area networks – Part3: Carrier sense multiple access with collision detection – Access method and physical layer specifications, 1989. [21] CCITT Recommendation Numbering plan for the ISDN area, Vol. II, Rec.E.164. [22] ISO8802-2 Information processing systems – Local area networks – Part2: Logical link control, Rec.E.164, 1988. [23] ISO8802-2/DAD2 Logical Link Control; Addendum2: Acknowl- edged connectionless-mode service and protocol, Type3 operation, 1988. [24] ISO 4902 Data communication – 37 pin and 9 pin DTE/DCE inter- face connectors and pin assignments, 1989. [25] CCITT Recommendation Association control service definition for open system interconnections for CCITT applications, Vol. VIII, Rec.X.217 (ISO8649,1988). [26] CCITT Recommendation Association control protocol specification for open system interconnections for CCITT applications, Rec.X.227 (ISO8650, 1988). [27] ISO9595/DAD 1 Information processing systems – Open system interconnection – Common management information service element definition, CANCEL-GET. [28] ISO9595/DAD 2 Information processing systems – Open system interconnection – Common management information service element definition, REMOVE. [29] ISO9596/DAD 1 Information processing systems – Open system interconnection – Common management information protocol speci- fication, CANCEL--GET. [30] ISO9596/DAD 2 Information processing systems – Open system interconnection – Common management information protocol speci- fication, REMOVE. [31] IEEE STD488 Standard digital interface for programmable instru- mentation, 1978. [32] CCITT Recommendation List of definitions for interchange circuits between data terminal equipment (DTE) and data circuit- terminating equipment (DCE), Vol. VIII, Rec.V.24. [33] EIA RS 449 General purpose 37-position and 9-position interface for data terminal equipment and data circuit-terminating equipment employing serial binary data interchange, 1977. [34] CCITT Recommendation Electrical characteristics for unbalanced double-current interchange circuits, Vol.VIII, Rec.V.28. [35] CCITT Recommendation Data transmission at 48kbits per second using 60-108kHz group band circuits, Vol. VIII, Rec.V.35. [36] CCITT Recommendation Electrical characteristics for balanced dou- ble-current interchange circuits for general use with integrated circuit equipment in the field of data communications, Vol. VIII, Recs.V.11 andX.27. [37] ISO2110 Data communication – 25-pin DTE/DCE interface connec- tor and pin assignments, 1989. [38] ISO2593 Data communications – 34-pin DTE/DCE interface con- nector and pin assignments, 1984. [39] CCITT Recommendation Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit, Vol. VIII, Rec.X.25 (ISO 8208, 1984 and ISO 7776, 1986). [40] ISO7776 Information processing systems – Data communications – High-level data link control proce- dures –Description of the X.25 –LAPB-compatible DTE data link procedures, 1986. [41] ISO8208 Information processing systems data communications – X.25 packet level protocol for data terminal equipment, 1987. [42] CCITT Recommendation Use of X.25 to provide the OSI connection- mode network service for CCITT applications, Vol. VIII, Rec.X.223 (ISO8878, 1987). [43] CCITT Recommendation Procedure for exchange of protocol identifi- cation during virtual call establishment on packet switched public data networks, Vol. VIII, Rec.X.244 (ISO TR 9577, 1990). [44] ISOTR 9577 Information technology – Telecommunications and information exchange between systems – Protocol identification in the OSI network layer, 1990. [45] ISO IEC8073/AD 1 Information processing systems – Open systems interconnection – Connection oriented transport protocol specification–Addendum1: Network connection management sub- protocol, 1988 . [46] CCITT Recommendation International numbering plan for public data networks, Vol. VIII, Rec.X.121. [47] CCITT Recommendation Network service definition for open sys- tems interconnection for CCITT applications, Rec.X.213, 1988 (ISO8348, 1987; 8348/AD2, 1989; 8348/AD 3, 1988). [48] CCITT Recommendation Transport service definition for open sys- tems interconnection for CCITT applications, Vol. VIII, Rec.X.214 (ISO8072, 1986). [49] CCITT Recommendation Transport protocol specification for open systems interconnection for CCITT applications, Vol. VIII, Rec.X.224 (ISO8073, 1988). [50] ISO8072 Information processing systems – Open systems intercon- nection – Transport service definition, 1986. [51] ISO 8073 Information processing systems – Open systems intercon- nection – Connection-oriented transport protocol specification, 1988. [52] ISO 8073/AD 2 Information processing systems – Open systems interconnection – Connection-oriented transport protocol specifica- tion, 1988 – Addendum2: Class4 operation over connectionless net- work service, 1989. [53] CCITT Recommendation Session service definition for open system interconnection for CCITT applications, Vol. VIII, Rec.X.215 (ISO8326, 1987 – 8326/AD1, 1988 – 8326/AD 3, 1989). [54] CCITT Recommendation Session protocol specification for open sys- tem interconnection (OSI) for CCITT applications, Vol. VIII, Rec.X.225 (ISO8327 – 8327/AD 1 – 8327/AD 3, 1988). [55] CCITT Recommendation Presentation protocol specification for open system interconnection for CCITT applications, Vol. VIII, Rec.X.226 (ISO8823, 1988). [56] ISO 9545 Open systems interconnection application layer structure, 1989. [57] EIA RS 485 Standard for electrical characteristics of generators and receivers for use in balanced digital multipoint systems, 1983. [58] CCITT Recommendation Q-interfaces protocol selection process for transmission equipment, Vol.III, Rec.G.771. [59] ISO 8880/3 Specification of protocols to provide and support the OSI network service – Part 3: Provision and support of connectionless- mode network service, 1988. [60] ISO DTR 10172 Informations processing systems – Data communica- tions network/transport protocol interworking specification. [61] CCITT Recommendation Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for synchronous operation on public data networks, Vol. VIII, Rec.X.21. [62] CCITT Recommendation Use on public data networks of data termi- nal equipment (DTE) which is designed for interfacing to synchro- nous V-Series modems, Vol. VIII, Rec.X.21bis. [63] ISO 4903 Data communication – 15-pin DTE/DCE interface connec- tor and pin assignments, 1980. [64] CCITT Recommendation Electrical characteristics for unbalanced double-current interchange circuits for general use with field of data communications, Vol. VIII, Recs.V.10 and X.26. INTERNATIONAL TELECOMMUNICATION UNION CCITT G.773 THE INTERNATIONAL TELEGRAPH AND TELEPHONE CONSULTATIVE COMMITTEE GENERAL ASPECTS OF DIGITAL TRANSMISSION SYSTEMS; TERMINAL EQUIPMENTS PROTOCOL SUITES FOR Q-INTERFACES FOR MANAGEMENT OF TRANSMISSION SYSTEMS Recommendation G.773 Geneva, 1990 FOREWORD The CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of the International Telecommuni- cation Union (ITU). CCITT is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approves Recommendations pre- pared by its Study Groups. The approval of Recommendations by the members of CCITT between Plenary Assemblies is covered by the procedure laid down in Resolution No. 2 (Melbourne, 1988). Recommendation G.773 was prepared by Study Group XV and was approved under the Resolution No. 2 procedure on the 14th of December 1990. ___________________ CCITT NOTE In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication Administration and a recognized private operating agency. ãITU1990 All rights reserved. No part of this publication may be reproduced or uti- lized in any form or by any means, electronic or mechanical, including pho- tocopying and microfilm, without permission in writing from the ITU.