This part of the local area network (LAN) standard mainly discusses the various components of the token passing bus access method and its related physical signaling and media technology. In order to make the interconnection of all stations of the local area network using the token passing bus access method compatible, this standard: 1) specifies the electrical characteristics and/or optical and physical characteristics of the transmission media; 2) specifies the electrical or optical signaling method used; 3) specifies the transmission frame format; 4) specifies the actions taken by the station when a frame is received; 5) specifies the services provided at the conceptual interface between the media access control (MAC) sublayer and the logical link control (LLC) sublayer above it; 6) specifies the actions, entities and values ​​used to manage the MAC sublayer and the physical layer entity (PLE). GB/T 15629.4-1997 Information Processing System Local Area Network Part 4: Token Passing Bus Access Method and Physical Layer Specification GB/T15629.4-1997 Standard Download Decompression Password: www.bzxz.net

GB/T 15629.4—1997 Local Area Network Part 4: Token Passing General
This standard is equivalent to the international standard 15629.4:1990 Information Processing System Line Access Method and Physical Layer Specification".
This standard is consistent with the international standard in both technical content and format. The following parts are included under the general title of "Local Area Network": GR/T 15629 Local Area Network Part 4: Token Passing General
This standard is equivalent to the international standard 15629.4:1990 Information Processing System Line Access Method and Physical Layer Specification".
This standard is consistent with the international standard in both technical content and format. The following parts are included under the general title of "Local Area Network": GR/T 15629 Local Area Network Part 1: Overview of Local Area Network Standards
Part 2: Interconnection Link Control;
Part 3: Baseband Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specification; Part 4: Token Passing Bus Access Method and Physical Layer Specification; Part 5: Token Ring Access Method and Physical Layer Specification. Appendix A of this standard is a suggestive appendix. This standard was issued by the Ministry of Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of the Standardization Institute of the Ministry of Electronics Industry. The drafting unit of this standard: the Standardization Institute of the Ministry of Electronics Industry. The main contributors to the standardization are Luo Ren and Huang Jiaying. ng
GB 15629.4-1997
ISO/IEC Foreword
ISO (International Electrotechnical Organization for Standardization) and JFC (International Electrotechnical Commission) are global standardization organizations. National member bodies (which are all member states of ISO () or IEC) participate in the formulation of international standards for specific technical scopes through various technical committees established by international organizations. JSD and IEC technical committees cooperate in areas of common interest. Other official or non-official international organizations associated with ISO and IEC can also participate in the formulation of international standards. For the field of information technology, ISO and IEC have established a joint technical committee, namely ISO/IEC JTC1. The draft international standards proposed by the joint technical committee are circulated to national member bodies for voting. To publish an international standard, at least 75% of the national member bodies participating in the voting need to vote on the cumulative voting fee.
In 1985, ISO Technical Committee 97\Information Processing Systems" accepted IEEE sid802.4:1985 as a draft international standard 1SO/LIS8RO2-4. Subsequently, 1SO/IEC JTC1 approved a further revised version, which is the new version, and it was published as international standard IS/IEC8802-41990. This standard is part of the local area network (LAN) series of standards. The relationship between this standard and other components of the series of standards is shown in the figure below ( The numbers in the code refer to ISO standard numbers). 8822
Broadband
88112-3
8802-
Physical Link
This series of standards refers to the physical layer and data link layer defined in the ISO open-source system interconnection reference model (ISO7498:1981). The access standard defines four types of media access technologies and their associated physical media, each suitable for a specific application or system goal. The standards that define these technologies are:
(1)1ISO 8802-3 [IEEEstd 802.3:19B8], using CSMA/CD bus as access method (2) ISO/IEC8802-4 [IEEEstd802.4:1990], using token passing bus as access method (3) ISO/IEC8802-7 using split ring as access method ISO8802-2 [IEEEstd802.2:1989] \ Logical Link Control Protocol \ Used with various media access standards It is recommended that readers of this standard be familiar with the complete list of standards. Unless otherwise specified, it is not used as a standard The main body of this standard is available as both 1S0/IEC8802-4:1990 and [IEEE802.4:1990] except for the contents that are part of the IEEE standard. Those contents that are specifically stated apply only to the IEEE standard. The annexes to each chapter serve as useful reference material for both standards.
National Standard of the People's Republic of China
Infurmation pracessing systems-Local area network-Part 4:Token-passing bus access method and physical layer specifications 1 Introduction and Overview
GB/T 15629.4—1997
idt 1S0/IEC 8802-4:1990
This part of the Local Area Network (LAN) standard discusses the various components of the token-passing bus access method and its associated physical signaling and media technology. This access function coordinates the use of the shared medium by all connected stations. The relationship between it and other protocol functions is shown in Figure 1-1.
Route requirements
Chapter 2
Chapter 4, 5, 5.7
Chapter 8
Chapter 10, 12.14:16.18
Chapter 13, 15.17.19
1.1 Scope
Medium access control
Object and personnel
Figure 1-1 Adjacency protocol Relationship of layers
Chapter 9
In order to make the interconnection of all stations in the local area network using the token passing bus access method compatible, this standard: 1) specifies the electrical characteristics and/or optical and physical characteristics of the transmission medium; 2) specifies the electrical or optical signaling method used; 3) specifies the send reply format;
4) specifies the actions taken by the station when receiving a burst; 5) specifies the services provided at the conceptual interface between the media access control (MAC) sublayer and the logic link control (LLC) sublayer above it;
6) specifies the operations, entities and values ​​used to manage the MAC sublayer and the physical layer entity (P[.E) Within the scope of this standard, the operation of a station is specified using the layered model shown in Figure 1-1 and described in GB 9387. Approved by the State Administration of Industry and Information Technology on September 2, 1997 and implemented on April 1, 1998
CB/T15629.4-·1997
The details of the LAN802 standard can be found in the IEEE802.1A standard. Figure 1-1 also shows which clauses in this standard specify the interfaces between layers and which clauses specify the operation of the layers themselves. Recommendations on the allocation of power for use in CATV systems are specified by other standards and are not covered by this standard. 1.2 Definitions
The definitions used in this standard are consistent with GR5271.9 and IS/IEC2382-25. 1.3 Referenced Standards
The clauses included in the following standards constitute the clauses of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards will be revised. Parties using this standard should explore the possibility of using the latest versions of the following standards. IFF.E and ISA standards are not part of this standard. CGB4943-1995 Safety of information technology equipment (including electronic business equipment) (idtIEC950: 1986) GB5271.9-86 Data processing vocabulary Part 09: Data communication (eqvISO2382-9: 1984) GB7247-1995 Laser product radiation safety, equipment classification, requirements and user guide (idtIEC825: 1984) [B9251--88 Information technology equipment optical interference limit values ​​and test functions Method (dtCISPR22:1985GB9387-88 Information Processing System Open System Interconnection Basic Reference Model (dtISO7498:1984) GB9387.4-1996 Information Processing System Open System Interconnection Basic Reference Model Part 4: Management Framework (idtISO/IEC7498-4:1989)
GB/T15629.2-1995 Information Processing System Local Area Network Part 2: Logical Link Control (idt 1SO 8802-2:1989)
GB/TI6262—I996 Information Processing System Open System Interconnection Abstract Syntax Notation One (ASN.1) Specification (idt 150 8824:1987)
G13/T16678.3—1996 Information Processing System Fiber Distributed Data Interface [1 (FDD1) Part 3: Token Ring Physical Layer Media Dependent (PMD) Part (idtIS()/IEC9314-3:1990) IEC)169-8:1978 Radio Frequency Connector Part 8; The inner diameter of the outer conductor is 6.5mm (0.256in), bayonet locking RF coaxial connector (- characteristic impedance 500 (BNC type) (idtIEC169-8:1978) ISO/IEC2382-25:1992 Information technology vocabulary Part 25, local area network ISO/IEC9595:1991 Information processing system open system interconnection public management information service definition IS()/IEC:9596:199T Information processing system open system interconnection public management information protocol specification Information technology open system interconnection local area network media access control (MAC) service definition IS0/TEC100391991
CC1TTX.150:1988 Maintenance test principles for public data networks using data terminal equipment (DTE) data circuit terminating equipment (DCE) test loop
5 Frequencies below 3MHz Rectangular connectors Part 2: Circular contacts (fixed contact welding type) connection IEC 807-2:1985
Equipment Specification
ANSI/1SA-S72.01:1986PROWAY-LAN.T Industrial Data Channel 1EEEC37.90.1:1989Test Standard for Wave Resistance for Protection Relays and Maintenance Electrical Systems (ANS1)TEFF802.1A:1990IEEE Standard for Local Area Networks and Urban Area Networks: Overview of Network Standards and ArchitectureEEE 802.1B:1992
Local Area Network and Metropolitan Area Network Management
IEF802.7:19891EEE Recommended Practice for Broadband Local Area Network Implementations 1.4 Conformance
Implementations claiming to conform to this standard must: 1) provide the mandatory LLCMAC interface services specified in Section 2; 2) support the mandatory layer management actions, entities, and values ​​specified in Sections 3 and 9; 3) generate, send, receive, and recognize the mandatory sequences specified in Section 4; 4) perform the mandatory media access protocol specified in Sections 6 and 7. Capabilities, restrictions and behaviors: 342
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5) Provide the necessary MAC sublayer·physical layer interface services specified in Chapter 8:
6) Support the necessary capabilities, characteristics and restrictions and media specifications of at least one PL.E defined in Chapters 12 and 13, Chapters 14 and 15, Chapters 16 and 17, and Chapters 18 and 19, 7) Support at least one selected PI.E specified data speed, 8) Support the capabilities, behaviors or values ​​defined for each option that the implementation claims to support. Unless otherwise specified, all specifications should be fully applicable to the entire range of operating environments that the manufacturer claims to be consistent. This standard also specifies many options, and the implementation should indicate which options are supported. 1.5 Overview of the token access method
1.5.1 The essence of the token access method
1) The token controls the right to access the physical medium: The station holding the token temporarily controls the medium. 2) Stations residing on the medium pass tokens to each other, and when the token is passed from one station to another, a logical ring is formed. 3) Steady-state operation consists of a data transfer phase and a token transfer phase. 4) The ring maintenance function within the station provides general transaction processing for ring initialization, recovery of lost tokens, addition of new stations to the logical ring, and invitation to the logical ring. All stations on the network that use tokens should have ring maintenance functions. Shared media can generally be classified into two major types, namely broadcast and sequential. This standard only deals with broadcast. On broadcast media, each station can receive all transmitted signals. Broadcast media are usually configured as a physical bus. In Figure 1-2, note that the token media access method is always sequential in an logical sense. That is, during normal steady-state operation, the right to access the space medium is passed from one station to another. Moreover, physical connectivity has no effect on the order of the logical ring, and even the stations that can respond to the token holder's query are not necessarily part of the logical ring (for example, stations H and F can receive traffic and respond, but cannot initiate transmission because they never get a token). The MA sublayer provides sequential access to the shared medium by passing control of the medium from one station to another in a logically circular manner. The MAC layer determines when the station has the right to access the shared medium by identifying and receiving the token from the predecessor station, and determines when the token should be passed to the successor station.
1.5.2 Sublayer Functions of Communication
1) Lost Token Timer,
2) Distributed Optimization:
3) Token Holding Timer:
4) Limited Data Buffering,
5) Node Address Error;
6) Encapsulation (including token preparation);
7) Recovery Check Sequence (FCS) Generation and Verification
8) Valid Token Identification,
9) Ring Negative Addition/Removal:
10) Node Failure Error Recovery.
Figure 1-2 Physical and logical loops on the bus
1.6 Internal structure of the MAC sublayer
GB/T15629.4—1997
MAC performs several loosely coupled functions. The description and specification of the MAC sublayer in this standard is organized according to one of the possible divisions of these functions. Figure 1-3 illustrates the division adopted here, which shows five asynchronous logical "machines", each of which will perform some auxiliary functions of the MAC, see the discussion in 1.6.1 to 1.6.5. Among the five machines, the access control machine (ACM) is the most critical and complex. It is the key control mechanism of the token-passing bus access method, and it cooperates closely with the ACMs of other stations based on limited information about the network status. Due to its importance and the fact that its operation is not easy to infer from its functional requirements, Chapters 5, 6, and 7 are mainly about the interpretation and description of the ACM:
IFM and RxM are deeply involved in the MAC sublayer protocol operations. However, their discussion is intended to be sufficient to give the reader an understanding of the role they play in the MAC sublayer and in supporting ACM. This depth of discussion was chosen to avoid any ambiguity that would jeopardize the coexistence of consistent stations on a single bus. LiC
Interface Machine
Valve Control Machine
Receiver
Regenerative Repeater Machine (RRM)
(and selected》
TransmitterWww.bzxZ.net
Figure 1-3 Division of MAC sublayer functions
1.6.1 Interface Machine (IFM)
This machine is mainly used as an interface between the LIC layer and the MAC sublayer, and between the network management and the MAC sublayer. It interprets all MA-UNITDATA and other service primitives and generates appropriate outgoing service primitives. Where necessary, this machine handles the mapping of "quality of service parameters" from the LIC point of view to the MAC point of view. It also handles service requests (for example, a request to send an LLC protocol data unit (PDU)). Finally, it also performs a "request identification" function on the received data frames, but only accepts those that are addressed to this station. 1.6.2 Access Control Machine ( ACM)
This machine cooperates with the ACMs of all other stations on the bus in processing tokens to control transmission access to the shared bus. The ACM can also manage multiple MAC access categories (optional) to provide different levels of "quality of service" to the LIC\ sublayer. The ACM is also responsible for initialization and maintenance of the logical ring, including admission of new stations. Finally, it is responsible for detecting faults and failures in the token transmission bus network and recovering from them when possible.
1.6-3 Receiver (RxM)
This machine accepts atomic symbols input from the physical layer and assembles them into valid transmissions to the IFM and ACM. RxM accomplishes this task by identifying the start and end delimiters (SD and ED) of the packet and checking the FCS and the structure of the valid packet. RxM also identifies and indicates the received burst noise and bus-sensitive quiet state. 1.6.4 Transmitter (TxM)
This machine generally receives the frame from the ACM meter and sends it to the PLE in the correct format in the order of atomic symbols. TxM adds the required preamble and SI in front of each frame in s14
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, and adds FCS and ED at the end of the packet to form a MAC protocol data unit. When working with a Bosen repeater machine (RRM), the operation of TxM is slightly different. 1.6-5 Regeneration repeater machine (RRM)
This machine is an optional MAC component that only appears in a specific "repeater" station, for example, a "wideband remodulator". In this repeater station, RRM will be from the physical layer entity (PLE) to the human-source sub-symbol relay invitation back to the PLE for retransmission + in this case, it should be understood as PL.1.7 PLE and Media
This clause provides an overview of the various chapters of this standard regarding PLE and also introduces the various physical host signaling technologies and media defined for LANs using the token passing MAC protocol.
Four bus media and corresponding PLEs are defined for the token passing MAC protocol. Each PLE and corresponding bus media are described in two adjacent chapters (i.e., Chapters 12 and 13, Chapters 14 and 15, Chapters 16 and 17, and Chapters 18 and 19), consisting of the following: 1) A chapter specifies a specific PLE, including how to specify the generic management objects (Chapter 9) in that PLE: 2) A chapter specifies the media corresponding to that PLE. This standard specifies four different PLEs and their corresponding media using the token passing bus MAC protocol. They are mainly distinguished by the different signaling and media forms specified for each PLE type. The rest of this clause describes the key points of each PLE type and the corresponding media.
1.7.1 Phase coherent frequency shift keying (FSK) topology: Full-interval bus.
Cable: 75 coaxial cable, such as RG-1t type or semi-rigid. Station connector: 75 F series, specified by GB11313. Recommended cable configuration: RG-I1 type CATV trunk cable or semi-rigid and flexible branch cable. Up to 50m: Trunk connection unit: 750 omnidirectional 20dB non-irrigated impedance matching branch. Repeater: Active regeneration relay used as high fan-out branch and system expansion beyond the limit of a single cable segment. Transmit level: +63~+66dB (1mV752) [aBmV] Receive sensitivity, +10 dBmV~+66 dBmV. Data speed: 5Mibit/s and 10Mbit/s. Signaling data and non-data symbols are directly encoded as an integer period of a fixed frequency, and the rate changes only when the waveform crosses zero. Two rates are used:
1) The low one is 1Hz(bit/s) (i.e. 5MHz at 5Mbit/s and 10MHz at 10Mbit/s) 2) The high one is 2Hz(bit/s) (i.e. 10MHz at 5Mhit/s and 20MHz at 10Mbit/s). Symbols are represented as:
0 - two full periods of the high frequency:
1 - one full period of the low frequency.
non.data pair: one full period of the high frequency, one full period of the low frequency, plus one full period of the high frequency. pad.idle: starts with 1: alternating 1 and 0 symbols. Clock recovery, from equal changes in the received signal. Transmit data timing: The transmit rate is phase locked. All regenerative repeaters use the same transmit data timing and therefore have exactly the same transmit frequency.
1.7.2 Multi-level dual binary amplitude modulation/phase shift keying (AM/PSK) topology: Directed bus with active relay. Cable +750 coaxial cable, such as RG-6 type or semi-rigid. Station connector: 752 F series, specified by GB11313 (see note to 15.5.1-). :13
GB/T15629.4—1997
Recommended cable matching, similar to CATV semi-rigid trunk cable and flexible drop cable. Line connection unit: 75 directional passive anti-matching tap, Repeater: Regenerative relay is used as the system data rate clock source and central monitor of contention and noise, and retransmits all signaling received on the directed media.
Amplifier; Standard CATV two-way (one-way for dual power distribution) broadband micro-amplifier used as system expansion exceeding the basic signal loss budget,
Channel bandwidth: 1. 5MHz, 6MHz and 12MHz. Transmitter level: +41dB (1mV, 750) [dBmV3 at 1.5MHz bandwidth, +47dB (]mV, 75a> [dBmV at 6MHz bandwidth, +50dB (1mV, 75Q> [BmV at 12MHz bandwidth. Receiver sensitivity: -13+4dH (1mV, 752) [dRrnV] at 1.5MHz, -7~+10dB (ImV.75m[dBmV] at 6MHz. -4~+13dE (1mV, 75) [dBmV] at 12MHz. Data rate: 1MLit/s at 1.5MHz, 6MHz 5 Mbit/s at 12 MHz and 10 Mbit/s at 5 MHz. Channel frequency allocation: Channel frequency allocation is the subject of other standards. The following recommended channel allocations are only an example. They are not part of this standard.
For 10 Mbit/s, channels 3 and 4 (59.75 to 71.75 MHz) and P and Q (252 to 264 MHz). For 5 Mbit/s, channels 3 (59.75 to 65.75 MHz) and P (252 to 2258 MHz) or channel 4 (65.75 to 71.75 MHz) and P (252 to 2258 MHz). and Q (258～264MHz), for 1Mbit/s, any eight sub-channels of the reverse channels 3° and 4' and the corresponding front channels P and Q with equal intervals of 1.5MHz.
Scrambler: A self-scrambler with a generating polynomial 1+×-+X, which acts on all data before scrambling for transmission, with the purpose of increasing the average number of transitions in transmission and randomizing the spectral components of the modulation being transmitted. Signaling: data and pon.data symbols are encoded to specify the final amplitude. This standard defines a single form - each ||tt| |PHY symbol and one MAC symbol, and also consider the compatibility of the additional form described in 14.1.1P. In both signaling forms, the intermediate level is only used to represent non-tlata symbols, which are used in the delimiter and report "quiet", and are also used to interrupt other single long sequences of valid signals. See 14.8.2.14>>7. Because a scrambler is added before the data is encoded and sent, such a long sequence is unlikely to occur. For the signaling of one MAC symbol per PHY symbol, the symbol is represented at the receiver as: 10]=0——cold amplitude,
{4}= r—"maximum\amplitude,
2inon.—.The amplitude is half of the "maximum\amplitude", the intermediate amplitude, thanks: multi-level dual binary AM/PSK.
pad_idle: starts with (4), alternating (4) and t0) symbols. Report "quiet" A repeated symbol sequence sent by the remodulator, reporting that no signaling has been received. The sequence has four symbol periods, and the repetition can be destroyed after any symbol in the sequence. By listening to the modulation transients used, their automatic gain control (AGC) can be set, and the signaling method of the system can be quickly determined. For the signaling of one MAC symbol per PHY symbol, the sequence is: 12)(2)(01(4)
For the signaling mode of two MAC symbols per PHY symbol, the following sequence is retained: 12)121(4+101
The implementation that finds this repetitive sequence must switch to the enhanced operation mode and prohibit transmission. Clock recovery: from the level change in the received signaling. 16
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Send data timing: The modulator is the timing source, and all other stations rely on the timing of the received data. 1.7.3 Overview of fiber optic media
Topology: Use active or passive star-shaped bus. Cable: This standard uses silica fiber waveguide with the following nominal characteristics, and its properties are: Core diameter 62.5mm, outer diameter 125mm, effective digital aperture 0.275,
Note: 16.10 and 17.9 describe the operation of using a 50mm replacement test optical fiber. Station connector: The cable plant interface connector (CPIC) is a duplex connector, which is defined in GB/T16678. Repeater: Active regenerative repeater for high fan-out topology. Transmission characteristics: Using a central waveguide between 800 and 910nm, the effective optical transmission power is -7 to -11dBm. Receiver sensitivity: Medium sensitivity, using a -40dBm quiescent level, the effective power is -11 to -31dBm; distance, using a 50dBm quiescent level, the effective power is -21 to -41dBm. Data speed: 5Mbit/s, l0Mbit/s,and 20Mbit/s. Signaling: Manchester coding of data and non-data symbols, the symbols are represented as:
(I) =0
LLHH) and (HHLL) non-data symbol pairs. pad_idle: starting with 1, alternating 1 and 0 symbols. Clock recovery: derived from the Manchester coding generation. Transmit data timing: transmit rate phase locked. All regenerative repeaters use alternate transmit data timing, so there is exactly the same transmit frequency,
1.7.4 Summary of phase continuous FSK
Topology: omnidirectional bus.
Trunk cable t75 coaxial cable, such as RG-6, RG-11 and semi-rigid. Branch cable: 35~502 coaxial short cable, less than 350mm in length. Station connector; 50Q male BNC series, see GB11313, 8. Recommended power configuration: long unbranched trunk cable with drop cables. F-line connection unit: 752T-type connector.
Intermediate: A regenerative repeater used as a branch and system expansion that exceeds the basic signal loss budget. Transmit level: +54～+60dB(lmV,37.52). Receiver sensitivity: +24dB (1mV, 37.5) Data rate: 1Mbit/s.
Signaling: Manchester coding of data and non-data symbols, whose symbols are represented by 1
(HL)=0 -—starting high level, last low level, [IH) =1——starting low level, recording high level, (1.I.HH: and (HHLL} a non-data symbol pair, the first pair of low levels returns to a pair of high levels, and vice versa. Modulation: Phase-linked FSK (a form of frequency modulation) represented by Manchester 1) High level frequency (6.25±0.08)MHz12) Low level frequency =3.75±0.08)Hz. patl_idle: Start with 1, alternating 1 and 1 symbols. Time recovery, the variable generated by Manchester coding. 1.7.5 Industrial Control Alternative Physical Layers and Media 317
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Industrial Control Alternative Physical Layers and Media are specified in ANSI/ISA--S72.01. These alternative physical layers and media are compatible at the MAC sublayer-physical layer interface. 1-B Access Method Characteristics
To better understand when and where the token passing bus is a suitable LAN technology, it is helpful to understand the basic characteristics of the token passing access method. Some important features of this media access method are as follows: 1) Under heavy load, the coordination of each station requires only a small percentage of the media capacity. In this sense, the method is efficient. 2) It provides each station with an equal shared media capacity. In this sense, the method is fair. However, it does not require each station to use up its allocated bandwidth.
3) The method allows multiple service classes.
4) The method coordinates the transmission of stations so that the interference between stations is small and controllable. 5) The method does not impose additional requirements on the media and PIE beyond the necessary integration for the transmission and reception of multi-bit, multi-frame sequences at a specified average bit error rate. 6) The method provides calculable, qualitative and performance bounds for the highest priority service class under conditions of no system noise for any given network and load configuration. 7) The controlled F-resistance periods are distinguishable and it is possible to save system noise in the remaining periods. 8) The method places minimal restrictions on the controlling media station's use of its shared media capacity. 9) The method effectively supports the proposed L1.C3 type service by allowing the token holding station to wait for the receiving station to respond to the token holding station's transmission.
10) Although not specified in this standard, this method allows a large number of low-cost, low-function stations to coexist with one or more full-function stations on the network (at least one full-function station is required for system operation). For example, a low-function station is a station that does not contain access control logic.
1.9 Structure of the Standard
This standard consists of 19 chapters:
Chapter 1 begins with a general discussion of the token passing bus access method. This chapter introduces the functional division of the MAC sublayer discussed in subsequent chapters. The choice of PLE and media is also reviewed here. Finally, the characteristics of the token passing bus access method are discussed. Chapter 2 describes the interface between the LLC sublayer and the MAC sublayer, and defines the service and command interface provided to the LLC sublayer (an overview).
Chapter 3 describes the management parameters, actions, and events within the MAC sublayer. Chapter 4 describes the general MAC structure, including delimiters, addressing, and FCS. All forms of MAC processing, including MAC control statements, are described.
Chapter 5 discusses the basic concepts of the access protocol and informally describes the actions of each state of the access control mechanism (ACM). Other state machines in the MAC layer are also described in Chapter 5. Chapter 6 contains definitions of basic MAC terms and components. Chapter 7 specifies the ACM of the MAC using the state machine model. This is the definitive specification of the operation of the token passing bus MAC. Chapter 7 also describes the MAC sublayer variables, functions and procedures used in the state machine. Chapter 8 describes the logical interface between the MA sublayer and the physical layer. It also includes a summary of the interface symbols, requirements and applications, and Chapter 9 defines the management parameters, actions and properties within the PLE. Chapter 10 defines the logical, electrical and mechanical interfaces within the PLE between stations and independent modems. Chapter 11 is reserved.
Chapter 12 and Chapter 13 describe the PLE and media for a 1Mbit/s or 10Mbit/s single channel (i.e. omnidirectional) phase coherent FSK coaxial cable bus, respectively.
Chapter 14 and Chapter 15 describe the PLE and media for a 1Mbit/s, 5Mbit/5, or 10Mbit/s dual channel (i.e. head end) wideband duobinary AM/PSK coaxial cable bus, respectively.
GB/T 15629. 4
Chapter 16 and Chapter 17 describe the PLE and media for a 5Mbit/s, 10M1bit/s, or 20Mbit/s optical fiber bus, respectively. Chapter 18 and Chapter 19 describe the PLE and media for a 1Mbit/s single channel (i.e. omnidirectional) phase continuous FSK coaxial cable bus, respectively.
2LLC-.MAC Interface Service Specification
This chapter specifies the services provided to the Logical Link Control (1.IC) sublayer and to the replacement sublayer specified in ANSI/1SAS72.01 at the boundary between the Media Access Control (MAC) layer and LLC functions of the data link layer of the reference model. This standard specifies these services in an abstract form. It does not specify or restrict the implementation of entities and interfaces in a computer system. The relationship between this chapter and other chapters of this standard and the local network specification is shown in Figure 2-1. Note
The exact relationship between the layers described in this chapter and the layers defined in the Open System Interconnection (OSI) Basic Reference Model (GB9BB7) is subject to further study. 2 The single service specifications common to all MAC sublayers are under development, see ISO/IEC10039. 2.1 L1,C-MAC Services
2.1.1 General Description of Services Provided
Computational Link Control
Fast Selection Mechanism
Figure 2-1 Relationship to LAN Model
This clause informally describes the services provided by the token-passing MAC sublayer to the LLC sublayer, which are two sublayers in the data link layer. These services provide connectionless data transfer services only between peer LLC entities. They provide the means by which MAC service data units (M_SDUs) can be exchanged without establishing a point-to-point connection with the underlying layer. Data transfer can be point-to-point or multipoint, unacknowledged or acknowledged.
2.1.2 Model used in service specification
The model and the description method are detailed in Appendix A (informative appendix). 2.1.3 Interaction Description
The primitives associated with this connectionless data transfer service are: 1) MA_UNITDATA request
2) MA UNITDATA indication
3) MA_UNITDATAconfirm
The MA_UNITDATArequest primitive is passed to the MAC sublayer to request the transmission of an M.SDU, (all M_SDUs are sent using the connectionless procedure). The MA_UNITDATAindication primitive is passed from the MAC sublayer to indicate the arrival of an M_SDU. The MA_UNITDATAconfitm primitive is passed back from the MAC sublayer to indicate the status of the previous related MA_UNITDATAconfirm primitive.
2- 1. 4 Basic Services and Options
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All service calls are mandatory and are required in all implementations. 2.2 (Details of LC Entity Interactions
This clause describes in detail the primitives and parameters associated with the LIC connectionless data transfer service. Note that the parameters are defined in an inferred sense. The parameters define information that must be used by the receiving entity. There is no restriction on the way in which this information is used in a particular implementation. For example, the M-SDUI parameters associated with certain data transfer service primitives may be provided by actually transmitting a MAC service data unit, or by passing a sequence symbol or other methods: some optional parameter values ​​may be included later in the implementation. 2.2.1 MA_UNITDATArequest
2.2.1.1 Function
This primitive is the service request primitive for the connectionless data transfer service. 2-2. 1 2 Semantics
This primitive shall provide the following parameters:
MA.. UNITDATA requst (
destination..address.
source- address,
M_SDU,
desired_quality
destiation_acldress parameter specifies a single or group of MAC entity addresses. The source_address parameter specifies the originating MAC entity address, typically the local station. The M_SDUI parameter specifies the MAC service data unit sent by the MAC layer entity in response to the LLC sublayer entity request. The dsired-quality parameter specifies the desired quality of service. The semantics of this parameter includes the MAC level priority, which ranges from 0 (lowest) to 7 (highest), see 6.6,1.2, to issue a MAC level delivery confirmation service, and its values ​​are no response request, response avoidance request, and response. 2.2.1.3. Generate Conditions
This primitive is passed from the I.LC sublayer entity to the MAC: sublayer entity so that the MAC
2.2.1.4 Effect of Receipt
Receipt of this primitive shall cause the MAC entity to compose and send the specified response. 2.2.1.5 Additional Comments
The delivery confirmation component of the quality parameters used in the response request shall indicate that the next MA_UNITDATA indication shall itself have the quality parameters for the specified response, in which case the next MA_UNITDATA indication is associated with this MA_UNITDATA request.
The delivery confirmation component of the quality parameters used in the response response shall itself have the quality parameters for the specified response request.
When specifying a response request, the group destination address shall not be used. 2-2.2 MA_UNIT1ATA indication 2.2.2.1 Capability
This primitive is a service indication primitive for the connectionless data transfer service. 2. 2. 2.2 Semantics
The source language shall provide the following parameters:
MA_UNITDATAindicazion（
destination_address,
soutce. address,
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