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ANNEX F (to Recommendation G.771) Proposed candidate protocol suites This annex contains the candidate protocol suites currently under consid- eration for selection as members of the PQ(lcn) family of protocol suites. The description of the individual protocol suites is of varying complete- ness, but each description is limited to the specification of the lower two or three OSI layers. For a complete protocol suite specification higher layers must be defined, however, the available information is provided here to guide hardware decisions. The completion of the descriptions and the selection is for further study. Candidate protocol suite No. 3 has the widest support, but no candidate protocol suite has yet been subjected to a formal selection process by CCITT. Each candidate protocol suite is described in the following sections. Fol- lowing the descriptions is a summary section which contains in TableF.5/ G.tmn the the candidate protocol selection attribute values (see AnnexE of this Recommendation). Differences of the values in TableF.5/G.tmn indicate differences in capabilities which may affect the suitability of individual candidates for particular application areas. Some initial applications are indicated for each candidate protocol suite. However, the range of applications appropriate to these suites has not been thoroughly examined. 1. Candidate protocol suite No.1 (CPS1) Initial application: Alarm surveillance, performance monitoring and configuration control of NEs found in reasonably large numbers in the telecommunications net- work (e.g., muldex, line transmission terminal). 1.1 OSI layer 1 1.1.1 Configuration One serial bus connects up to 30 nodes. Configurations with more than 30 nodes can be realized by a hierarchical structure of several serial buses. Such a hierarchical structure is characterized by a high throughput with a low transmission rate per bus. 1.1.2 Communication environment The serial bus configuration shall be used only for in-building applica- tion. 1.1.3 Physical connection One balanced, screened pair with a maximum length of 500 meters. 1.1.4 Electrical requirements Each bus interface shall be in accordance with V.11 multipoint intercon- nections. [1, 3, 14, and 23]. Each bus shall be terminated by resistors in accordance with [23]. Each receiver shall present a maximum of one unit load to the bus, as defined in [23]. 1.1.5 Line code The line code shall be NRZ (non return to zero). 1.1.6 Speed The bit rate shall be 19.2 kbit/s per second. The bit rate tolerance shall be + 1%. 1.1.7 Transmission mode The transmission mode shall be half duplex, asynchronous. 1.2 OSI layer 2 Asynchronous, byte oriented protocol according to [15]. 1.2.1 Transmission frame format The transmission frame format shall be in accordance with [15, i]. 1.2.2 Link transmission procedure The link transmission procedure shall be in accordance with [15, ii]. All standard transmission frames specified in [15] shall be used (frame with variable length, frame with fixed length and single character). The operation mode shall be: master/slave, cyclical polling. 1.2.3 Addressing The address one to 30 of the 256 possible addresses shall be used for cyclical polling. The address 255 shall be used for broadcasting (one message to all nodes). 1.2.4 Window size The window size is fixed to one. 1.3 Higher layers Under study. 2. Candidate protocol suite No. 2 (CPS 2) Initial application: Alarm surveillance, performance monitoring, testing commands, response and configuration control of NEs including cross-connect equipment, can be applied to both NEs found in reasonably large num- bers in the telephone network (e.g., muldex, line transmission terminal) and to high capability NEs found in limited numbers in the telecommuni- cations network (e.g., cross-connect). 2.1 OSI layer 1 2.1.1 Configuration: Bus. 2.1.2 Line speed: 1 Mbit per second. 2.1.3 Medium: Screened pair. 2.1.4 Electrical requirement: V.11 interface with pulse transformer. 2.1.5 Line code: CMI. 2.2 OSI layer 2 2.2.1 Frame format Frame components: - flag, - destination address --- 2 octets, - source address --- 2 octets, - control --- 1 octet, - LLC data --- variable length (maximum 512 octets), - frame check sequence --- CRC 16, - flag. 2.2.2 Media access control The media access control discipline known as carrier sense multiple access is used. 2.2.3 Logical link control layer Acknowledged connectionless mode protocol specification to be speci- fied in ISO8802-2/AD2 is used. 2.3 Upper layers Under study. 3. Candidate protocol suite No. 3 (CPS 3) Initial application: Alarm surveillance, performance monitoring, and configuration control of NEs found in reasonably large numbers in the telecommunications network (e.g., muldex, line transmission terminals). 3.1 OSI layer 1 3.1.1 Physical characteristics 3.1.1.1 Configuration Serial bus operation in accordance with ISODIS8482 (ring configura- tion under study). Use of full or half-duplex operation shall be determined by the adminis- tration. 3.1.1.2 Transmission pairs Two screened balanced pairs, one pair for each direction of transmission. Note - Two administrations have proposed using each of the pairs of half- duplex mode to provide additional bus security without additional wir- ing. Certain additional requirements relating to bus occupancy may then be necessary for correct operation in this mode. 3.1.1.3 Bus security Where additional bus security is required, bus duplication or output driver protection resistors may be considered. Note - Where duplicated buses are employed, no deliberate transmission should take place on both buses at the same time, and the functioning of one bus shall not be prejudiced by continuous noise to unintentioned transmissions on the other. 3.1.1.4 Connector The administration shall specify the connector type. 3.1.2 Electrical characteristics 3.1.2.1 Static and dynamic characteristics Static and dynamic characteristics of each bus connection shall be in accordance with [14]. 3.1.2.2 Bus termination Each bus end shall be terminated by resistors (120ohms +10%, -0%) in accordance with [14]. 3.1.2.3 Load connection Each receiver shall present a maximum of one unit load, as defined in [14] to the bus. The number of load connections is limited to 32. 3.1.2.4 Bit rate The bit rate shall be 19.2 or 64 kbit/s per second. A bit rate of 128kbit/s per second may be necessary in some applications. The bit rate tolerance shall be + 1%. 3.1.2.5 Turn off time A transmitting station shall put its generator in the high impedance state within 1ms from the end of the last bit of the final closing flag. Note - The need to reduce this time for bit rates above 19.2kbit/s per sec- ond is under study. 3.1.2.6 Preamble Following the enabling of the generator an implementation dependant preamble of no more than 4bit times is allowed. No assumption as to the state of the bus during this preamble is allowed. 3.1.3 Line code The line code shall be NRZI. Clock extraction by the remaining station is assumed. 3.1.3.1 Principle Each transition [14] shall represent a zero, and no transition shall repre- sent onebit. 3.1.3.2 Lock-in process For clock extraction, a lock-in sequence of either one octet of zeroes or one or two flags in accordance with [6], shall be sent immediately prior to the beginning of the opening flag of the frame to be transmitted and immediately following the preamble of º3.1.2.6 (if implemented). 3.1.4 Extended mode Where an extended mode capability is required (e.g., using a modem) the requirements of ºº3.1.1 to 3.1.3 shall apply with the following excep- tions: 3.1.4.1 Configuration - full duplex 3.1.4.2 Connector The connector shall conform to [16]. Appropriate signal leads are to be provided for modem control in accordance with CCITT RecommendationV.24 [2, 22]. See TableF.1/6.771. 3.1.4.3 Electrical requirements Data set control leads shall conform to RecommendationV.24 [2, 22]. 3.1.4.4 Line code NRZ line code shall be employed. A separate clock distribution shall be provided. 3.1.4.5 Speed The bit rate shall be 9.6 or 64kbit/s per second. Lower speed, e.g., 1.2, 2.4 and 4.8 kbit/s per second, may be necessary in some applications. 3.2 OSI layer 2 The data link protocol is synchronous HDLC type. 3.2.1 HDLC frame structure The HDLC frame structure shall conform to [6] (frame structure). 3.2.1.1 Addressing field The addressing field shall be one octet. 3.2.1.2 Information field The information field in any HDLC frame shall be an integral number of octets. Information field octets shall be sent least significant bit first. Maximum information field lengths of 128 and 256 octets shall be sup- ported. A maximum information field length of 512 octets may be necessary in some applications. 3.2.2 Addressing The secondary station shall be capable of being assigned any address in the range one to 254. 3.2.2.1 All-station address The address field pattern "11111111" is defined as the all-station address. 3.2.2.2 No station address The address field pattern "00000000" is defined as the no-station address. The no-station address shall never be assigned to a secondary station. 3.2.2.3 Group address Not used. 3.2.3 HDLC procedure The HDLC procedure is defined by [7]. 3.2.3.1 Commands and responses 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 Acknowledgment - DM: Disconnected Mode 3.2.3.2 Modes Two modes are selected: - one operational mode: Normal Response Mode (NRM) - one non-operational mode: Normal Disconnected Mode (NDM) 3.2.4 Class of procedure The Unbalanced operation Normal response mode Class (UNC) as defined by ISO7809 shall be implemented. 3.2.4.1 HDLC optional functions The following HDLC optional functions shall be implemented: - unnumbered information (option No. 4) - command UI - response UI - data link test (option No. 12) - command TEST - response TEST 3.2.5 Other parameters of OSI layer 2 3.2.5.1 Window size The window size is fixed to one. 3.2.5.2 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 has to be greater than the duration of the longest frame to be sent by the primary station, added with the response-time of the secondary station and the duration of the longest frame to be sent by the secondary station. 3.2.5.3 Number of repetitions In the situation of º3.2.5.2, the maximum number of repetitions before detecting a no-reply or a lost-reply condition is fixed to five (six requests). 3.2.5.4 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. (Note: the need to reduce this time for bit rates above 19.2kbit/s is under study). 3.3 Higher layers Under study. TABLE F.1/G.771 Pin description of 24-pin connector [16] - Equipment: removable strap to frame ground Cable: connected to shield * These circuits are optional for connection to an embedded opera- tions channel or modem and are not used for connections to a multi- point bus Circuits are grouped by function: ground, data, control and timing. Provision should be made at each interface point on a multipoint bus for the continuation of the interface to the next network element. Provision shall be made for the termination of the lines in their character- istic impedance (typically, 120ohms, resistive), should the equipment be at one end of a multipoint bus. For further information, see [2, 16, 22, 23]. 4. Candidate protocol suite No. 4 (CPS 4) Initial application: Alarm surveillance, performance monitoring, testing on specific NEs found in limited numbers in the telecommunications network (e.g., mul- dex, line transmission equipment). 4.1 Layer 1 Electrical - Recommendations V.24, V.28 Configuration - star Physical connection - ISO 211 (25 pin) (see Table F.2) Transmission mode - duplex, interface type D Operating speed - 1200, 2400, 4800 and 9600 bits per second (user option) Shield - ground strap to frame (user option) 4.2 Layer 2 It is mandatory that the data link layer conform to LAPB as defined in CCITT RecommendationX.25. In addition, provision shall be made for connection between Data Terminal Equipments (OSs and NEs) without an intervening packet switched network. The interface shall conform to [8]. Further detail is provided in the subsection entitled "Equipment type during link set-up and reset" below. The link layer specification that follows applies to all cases. 4.2.1 Equipment type during link set-up and reset When a packet switched network is used to connect the NE and OS, they each are designated "Data Terminal Equipment" (DTE) and the network acts as a "Data Circuit-Terminating Equipment" (DCE). When a dedi- cated or dial-up link is provided, other means must be used to supply the DCE role. At level 1, the modems will provide the DCE interface, supplying bit synch. At the link level, the procedures specified in [8] are followed. The NE or OS must be able to start the set-up or reset of the link (a DCE function in CCITT RecommendationX.25) as well as to respond to a start from the connecting equipment (a DTE function in CCITT RecommendationX.25). In addition, provision must be made for assign- ment of the A/B addresses. This mandatory option is to be field-settable and stored in non-volatile memory. Equipment which meets this require- ment is compatible with connection to either a DCE or remote DTE. 4.2.2 Window Modulo 8 operation shall be used. The window for unacknowledged frames is to be optional between 1 and 7 frames. Typical values are 7 and 2. 4.2.3 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, con- sistent with the range of values for the N1 parameter as shown in Table F.3. Maximum information field lengths that shall be supported are 131 and 259 octets with 515 octets optional. These values provide for three packet header octets and maximum length of packet data units of 128, and 256 and 512 octets respectively. 4.2.4 Other frame parameters Certain other frame parameters shall be set by the user to be consistent with the bit rate, frame size and characteristics of the connecting net- work. The NE design should be sufficiently flexible to accommodate parameter sets for diverse networks, both as order options and later reconfigurations. The range of parameters is shown in TableF.3. These options, like those of the physical layer, are to be set at installation, changeable by the user, and non- volatile. 4.3 Other layers No layer 3 is planned for this suite. Layers 4-7 are under study. 5. Candidate protocol suite No. 5 (CPS 5) Initial application: All management of high capability NEs found in limited numbers in the telecommunications network (e.g., digital cross-connect). Layer 1 Electrical - Recommendations V.24, V.28 Configuration - star Physical connection - ISO 2110 (25 pin) (see Table F.2) Transmission mode - duplex, interface type D Operating speed - 1200, 2400, 4800 and 9600 bits per second (user option) Shield - Ground strap to frame (user option) 5.2 Layer 2 It is mandatory that the data link layer conform to LAPB as defined in CCITT RecommendationX.25. In addition, provision shall be made for connection between Data Terminal Equipments (OSs and NEs) without an intervening packet switched network. The interface shall conform to [8]. Further detail is provided in the subsection entitled "Equipment type during link set-up and reset" below. The link layer specification that follow applies to all cases. 5.2.1 Equipment type during link set-up and reset When a packet switched network is used to connect the NE and OS, they each are designated "Data Terminal Equipment" (DTE) and the network acts as a "Data Circuit-Terminating Equipment" (DCE). When a dedi- cated or dial-up link is provided, other means must be used to supply the DCE role. At level 1, the modems will provide the DCE interface, supplying bit synch. At the link level, the procedures specified in [8] are followed. The NE or OS must be able to start the set-up or reset of the link (a DCE function in CCITT RecommendationX.25) as well as to respond to a start from the connecting equipment (a DTE function in CCITT RecommendationX.25). In addition, provision must be made for assign- ment of the A/B addresses. This mandatory option is to be field-settable and stored in non-volatile memory. Equipment which meets this require- ment is compatible with connection to either a DCE or remote DTE. 5.2.2 Window Modulo 8 operation shall be used. The window for unacknowledged frames is to be optional between 1 and 7 frames. Typical values are 7 and 2. 5.2.3 User information The user information is to be arranged in an integral number of octets. In other words, the data is to be structured in 8 bit bytes. The maximum length of the user information shall be user settable, con- sistent with the range of values for the N1 parameter as shown in TableF.3. Maximum information field lengths that shall be supported are 131 and 259 octets with 515 octets optional. These values provide for three packet header octets and maximum length of packet data units of 128, 256 and 512 octets, respectively. 5.2.4 Other frame parameters Certain other frame parameters shall be set by the user to be consistent with the bit rate, frame size and characteristics of the connecting net- work. The NE design should be sufficiently flexible to accommodate parameter sets for diverse networks, both as order options and later reconfigurations. The range of parameters is shown in TableF.3. These options, like those of the physical layer, are to be set at installation, changeable by the user, and non- volatile. 5.3 Layer 3 It is mandatory that the Packet Layer conform to CCITT RecommendationX.25. In addition the packet layer must provide for connection of Data Terminal Equipment (OSs and NEs) without an inter- vening packet network; the required interface for this purpose conforms to ISO 8208. In addition, the provisions of ISO 8878 shall apply. The attributes which must be supported are summarized in TableF.4. Note in particular that this table shows the different attributes needed to support PVCs (the X.25/PVC procedures) and SVCs (the X.25/SVC pro- cedures). 5.2.1 Equipment type during restart When the packet level X.25 interface is used, automatic selection of the DCE/DTE role during restart is required, as specified in ISO8208. 5.3.2 Other features and parameters The Packet Layer attributes are summarized in Table F.4. 5. Upper layers Under study. TABLE F.2/G.771 ISO 2110 pin description - Equipment: removable strap to frame ground Cable: connected to shield s Additional interchange circuits required for switched service t Additional interchange circuits required for synchronous channel x Basic interchange circuits, all systems = Circuit DA (CCITT 113) is not used in OS/NE interfaces Duplex, interface type D. Circuits are grouped by function: ground, data, control and timing. For further information, see [2, 3, 5, 19]. TABLE F.3/G.771 LAPB data link layer attributes ûûûûûûûûûûûûûûûûûûûû TABLE F.4/G.771 X.25 packet layer attributes ûûûûûûûûûû 6. Candidate protocol suite No. 8 (CPS 8) Initial application: Alarm surveillance, performance monitoring and configuration control of NEs found in reasonably large numbers in the telecommunications net- work (e.g., muldex, line transmission terminal). Interface characteristics 6.1 General characteristics - Network topology: "loop" (a variety of a ring chain configuration) - Serial data transmission - Master-slave principle - Maximum number of slaves: 30 - Transmission medium: one balanced screened pair (with the possi- bility of providing by-passes of faulty sections of the "loop" and slaves) - Maximum connection length between two connected slaves: 1000m 6.2 Layer 1 of the ISO-OSI reference model (physical layer) - Electrical characteristics in accordance with RecommendationsV.11 and V.24 [1, 2, 21] - Transmission method: asynchronous - Mode of operation of the slave: duplex - Transmission rate: < 19200 bits per second 6.3 Further layers are under study TABLE F.5/G.771 Candidate protocol selection attribute values +ûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+û ûûûûûû+ûûûûûûû+ _ Attribute _ CPS 1 _ CPS 2 _ CPS 3 _ CPS 4 _ CPS 5 _ CPS 6 _ +ûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+û ûûûûûû+ûûûûûûû+ _Layer 1 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ configuration _ B _ B _ B,R* _ S _ S _ R _ _ No. of ports per _ _ _ _ _ _ _ _ configuration _ M _ VL _ M _ M _ M _ M _ _ physical medium _ SP _ SP _ SP _ SP _ SP _ SP _ _ transmission mode _ AS-HD _ S-FD _S-HD,FD_ S-FD _ S-FD _ AS-HD _ _ operating speed _ 19200 _1000000_ 19200 _ 1200 _ 1200 _< 19200_ _ _ _ _ 64000 _ _ _ _ _ (bits per second) _ _ _128000 _ 9600 _ 9600 _ _ _ communication _ _ _ _ _ _ _ _ distance _ M _ M _ M(L) _ M(L) _ M(L) _ M _ _ communication _ _ _ _ _ _ _ _ environment _ IB _ IB _ IB(OB)_ IB(OB)_ IB(OB)_ IB _ _ availability* _ X _ X _ X _ X _ X _ X _ +ûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+û ûûûûûû+ûûûûûûû+ _Layer 2 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ data link connection _ CO _ CL _ CO _ CO _ CO _ CO _ _ data link initiator _ M _ AP _ M _ AP _ AP _ M _ _ data link address _ _ _ _ _ _ _ _ size _ M _ VL _ VL _ S _ S _ * _ _ receipt confirmation _ Y _ Y _ Y _ Y _ Y _ Y _ _ max. frame size _ S _ M _ S,M _ S,M _ S,M _ S _ _ max. frame frequency _ _ _ _ _ _ _ _ per port _ H _ H _ H _ H _ H _ M _ _ max. frame transmit _ _ _ _ _ _ _ _ delay _ M _ S _ M _ S,M _ S,M _ S _ _ error detection _ P+CS8 _ CRC16 _ CRC16 _ CRC16 _ CRC16 _ CRC _ _ hamming distance _ 4 _ _ _ _ _ _ _ error recovery _ R _ R _ R _ R _ R _ R _ +ûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+û ûûûûûû+ûûûûûûû+ _Layer 3 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ LCN network size _ _ _ _ _ VL _ _ _ routing _ _ _ _ _ Y _ _ _ (un) packing _ _ _ _ _ Y _ _ _ connections _ _ _ _ _ P,SW _ _ _ priority _ _ _ _ _ Y _ _ +ûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+û ûûûûûû+ûûûûûûû+ _Higher layers* _ _ _ _ _ _ _ +ûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+ûûûûûûû+û ûûûûûû+ûûûûûûû+ * Under study. 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