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802.3-2008 section 2.pdf

802.3-2008 section 2.pdf

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简介:本文档为《802.3-2008 section 2pdf》,可适用于电信技术领域,主题内容包含IEEEStandardforInformationtechnologyTelecommunicationsandinformationexchan符等。

IEEE Standard for Information technology— Telecommunications and information exchange between systems— Local and metropolitan area networks— Specific requirements Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access method and Physical Layer specifications SECTION TWO: This section includes Clause 21 through Clause 33 and Annex 22A through Annex 33E. 21. Introduction to 100 Mb/s baseband networks, type 100BASE-T 21.1 Overview 100BASE-T couples the IEEE 802.3 CSMA/CD MAC with a family of 100 Mb/s Physical Layers. While the MAC can be readily scaled to higher performance levels, new Physical Layer standards are required for 100 Mb/s operation. The relationships between 100BASE-T, the existing IEEE 802.3 (CSMA/CD MAC), and the ISO/IEC Open System Interconnection (OSI) reference model is shown in Figure 21–1. 100BASE-T uses the existing IEEE 802.3 MAC layer interface, connected through a Media-Independent Interface layer to a Physical Layer entity (PHY) sublayer such as 100BASE-T4, 100BASE-TX, or 100BASE-FX. 100BASE-T extends the IEEE 802.3 MAC to 100 Mb/s. The bit rate is faster, bit times are shorter, packet transmission times are reduced, and cable delay budgets are smaller—all in proportion to the change in bandwidth. This means that the ratio of packet duration to network propagation delay for 100BASE-T is the same as for 10BASE-T. 21.1.1 Reconciliation Sublayer (RS) and Media Independent Interface (MII) The Media Independent Interface (Clause 22) provides an interconnection between the Media Access Con- trol (MAC) sublayer and Physical Layer entities (PHY) and between PHY Layer and Station Management (STA) entities. This MII is capable of supporting both 10 Mb/s and 100 Mb/s data rates through four bit wide (nibble wide) transmit and receive paths. The Reconciliation sublayer provides a mapping between the signals provided at the MII and the MAC/PLS service definition. Copyright 2008 IEEE. All rights reserved. 1 IEEE Std 802.3-2008 REVISION OF IEEE Std 802.3: 21.1.2 Physical Layer signaling systems The following portion of this standard specifies a family of Physical Layer implementations. Typically 100BASE-TX (Clauses 24 and 25) uses two pairs of Category 5 balanced cabling as defined by ISO/IEC 11801, 100BASE-FX (Clauses 24 and 26) uses two multimode fibers. There are a number of other PHY types and their associated media. 21.1.3 Repeater Repeater sets (Clause 27) are an integral part of any 100BASE-T network with more than two DTEs in a collision domain. They extend the physical system topology by coupling two or more segments. Multiple repeaters are permitted within a single collision domain to provide the maximum path length. 21.1.4 Auto-Negotiation Auto-Negotiation (Clause 28) provides a linked device with the capability to detect the abilities (modes of operation) supported by the device at the other end of the link, determine common abilities, and configure for joint operation. Auto-Negotiation is performed out-of-band using a pulse code sequence that is compati- ble with the 10BASE-T link integrity test sequence. PRESENTATION APPLICATION SESSION TRANSPORT NETWORK DATA LINK PHYSICAL OSI REFERENCE MODEL LAYERS LAN CSMA/CD LAYERS LLC (LOGICAL LINK CONTROL) MAC—MEDIA ACCESS CONTROL PMA HIGHER LAYERS MDI = MEDIUM DEPENDENT INTERFACE MII = MEDIA INDEPENDENT INTERFACE PCS = PHYSICAL CODING SUBLAYER * MII is optional for 10 Mb/s DTEs and for 100 Mb/s systems and is not specified for 1 Mb/s systems. PMA = PHYSICAL MEDIUM ATTACHMENT PHY PHY = PHYSICAL LAYER DEVICE *MII MDI PCS ** PMD PMD = PHYSICAL MEDIUM DEPENDENT ** PMD is specified for 100BASE-X only; 100BASE-T4 does not use this layer. RECONCILIATION ** PMD PHY MDI PMA PCS 100BASE-T Repeater Baseband ** PMD PHY MDI PMA 100 Mb/s link segment PCS MEDIUM 100 Mb/s link segment MEDIUM Use of MII between PCS and Baseband Repeater Unit is optional. ***AUTONEG***AUTONEG***AUTONEG *** AUTONEG is optional. 100BASE-T Baseband Repeater Unit Figure 21–1—Architectural positioning of 100BASE-T Set OR OTHER MAC CLIENT 2 Copyright 2008 IEEE. All rights reserved. IEEE CSMA/CD Std 802.3-2008 21.1.5 Management Managed objects, attributes, and actions are defined for all 100BASE-T components (Clause 30). This clause consolidates all IEEE 802.3 management specifications so that 10 Mb/s, 100 Mb/s or 10/100 Mb/s agents can be managed by existing 10 Mb/s-only network management stations with little or no modification to the agent code. 21.2 References See 1.3. 21.3 Definitions See 1.4. 21.4 Abbreviations See 1.5. 21.5 State diagrams State diagrams take precedence over text. The conventions of 1.2 are adopted, with the following extensions. 21.5.1 Actions inside state blocks The actions inside a state block execute instantaneously. Actions inside state blocks are atomic (i.e., uninterruptible). After performing all the actions listed in a state block one time, the state block then continuously evaluates its exit conditions until one is satisfied, at which point control passes through a transition arrow to the next block. While the state awaits fulfillment of one of its exit conditions, the actions inside do not implicitly repeat. The characters • and [bracket] are not used to denote any special meaning. Valid state actions may include .indication and .request messages. No actions are taken outside of any state block. 21.5.2 State diagram variables Once set, variables retain their values as long as succeeding blocks contain no references to them. Setting the parameter of a formal interface message assures that, on the next transmission of that message, the last parameter value set will be transmitted. Testing the parameter of a formal interface messages tests the value of that message parameter that was received on the last transmission of said message. Message parameters may be assigned default values that persist until the first reception of the relevant message. Copyright 2008 IEEE. All rights reserved. 3 IEEE Std 802.3-2008 REVISION OF IEEE Std 802.3: 21.5.3 State transitions The following terms are valid transition qualifiers: a) Boolean expressions b) An event such as the expiration of a timer: timer_done c) An event such as the reception of a message: PMA_UNITDATA.indication d) An unconditional transition: UCT e) A branch taken when other exit conditions are not satisfied: ELSE Any open arrow (an arrow with no source block) represents a global transition. Global transitions are evalu- ated continuously whenever any state is evaluating its exit conditions. When a global transition becomes true, it supersedes all other transitions, including UCT, returning control to the block pointed to by the open arrow. 21.5.4 Operators The state diagram operators are shown in Table 21–1. Table 21–1—State diagram operators Character Meaning Boolean AND + Boolean OR Boolean XOR ! Boolean NOT < Less than Less than or equal to = Equals (a test of equality) Not equals Greater than or equal to > Greater than ( ) Indicates precedence Assignment operator Indicates membership Indicates nonmembership | Catenate ELSE No other state condition is satisfied 4 Copyright 2008 IEEE. All rights reserved. IEEE CSMA/CD Std 802.3-2008 21.6 Protocol implementation conformance statement (PICS) proforma 21.6.1 Introduction The supplier of a protocol implementation that is claimed to conform to any 100 Mb/s portion of this stan- dard shall complete a protocol implementation conformance statement (PICS) proforma. A completed PICS proforma is the PICS for the implementation in question. The PICS is a statement of which capabilities and options of the protocol have been implemented. A PICS is included at the end of each clause as appropriate. The PICS can be used for a variety of purposes by various parties, including the following: a) As a checklist by the protocol implementor, to reduce the risk of failure to conform to the standard through oversight; b) As a detailed indication of the capabilities of the implementation, stated relative to the common basis for understanding provided by the standard PICS proforma, by the supplier and acquirer, or potential acquirer, of the implementation; c) As a basis for initially checking the possibility of interworking with another implementation by the user, or potential user, of the implementation (note that, while interworking can never be guaranteed, failure to interwork can often be predicted from incompatible PICS); d) As the basis for selecting appropriate tests against which to assess the claim for conformance of the implementation, by a protocol tester. 21.6.2 Abbreviations and special symbols The following symbols are used in the PICS proforma: M mandatory field/function ! negation O optional field/function O.<n> optional field/function, but at least one of the group of options labeled by the same numeral <n> is required O/<n> optional field/function, but one and only one of the group of options labeled by the same numeral <n> is required X prohibited field/function <item>: simple-predicate condition, dependent on the support marked for <item> <item1>*<item2>: AND-predicate condition, the requirement must be met if both optional items are implemented 21.6.3 Instructions for completing the PICS proforma The first part of the PICS proforma, Implementation Identification and Protocol Summary, is to be com- pleted as indicated with the information necessary to identify fully both the supplier and the implementation. The main part of the PICS proforma is a fixed-format questionnaire divided into subclauses, each containing a group of items. Answers to the questionnaire items are to be provided in the right-most column, either by simply marking an answer to indicate a restricted choice (usually Yes, No, or Not Applicable), or by entering a value or a set or range of values. (Note that there are some items where two or more choices from a set of possible answers can apply; all relevant choices are to be marked.) Each item is identified by an item reference in the first column; the second column contains the question to be answered; the third column contains the reference or references to the material that specifies the item in the main body of the standard; the sixth column contains values and/or comments pertaining to the question Copyright 2008 IEEE. All rights reserved. 5 IEEE Std 802.3-2008 REVISION OF IEEE Std 802.3: to be answered. The remaining columns record the status of the items—whether the support is mandatory, optional or conditional—and provide the space for the answers. The supplier may also provide, or be required to provide, further information, categorized as either Additional Information or Exception Information. When present, each kind of further information is to be provided in a further subclause of items labeled A<i> or X<i>, respectively, for cross-referencing purposes, where <i> is any unambiguous identification for the item (e.g., simply a numeral); there are no other restric- tions on its format or presentation. A completed PICS proforma, including any Additional Information and Exception Information, is the proto- col implementation conformance statement for the implementation in question. Note that where an implementation is capable of being configured in more than one way, according to the items listed under Major Capabilities/Options, a single PICS may be able to describe all such configurations. However, the supplier has the choice of providing more than one PICS, each covering some subset of the implementation’s configuration capabilities, if that would make presentation of the information easier and clearer. 21.6.4 Additional information Items of Additional Information allow a supplier to provide further information intended to assist the inter- pretation of the PICS. It is not intended or expected that a large quantity will be supplied, and the PICS can be considered complete without any such information. Examples might be an outline of the ways in which a (single) implementation can be set up to operate in a variety of environments and configurations; or a brief rationale, based perhaps upon specific application needs, for the exclusion of features that, although optional, are nonetheless commonly present in implementations. References to items of Additional Information may be entered next to any answer in the questionnaire, and may be included in items of Exception Information. 21.6.5 Exceptional information It may occasionally happen that a supplier will wish to answer an item with mandatory or prohibited status (after any conditions have been applied) in a way that conflicts with the indicated requirement. No pre- printed answer will be found in the Support column for this; instead, the supplier is required to write into the Support column an X<i> reference to an item of Exception Information, and to provide the appropriate ratio- nale in the Exception item itself. An implementation for which an Exception item is required in this way does not conform to this standard. Note that a possible reason for the situation described above is that a defect in the standard has been reported, a correction for which is expected to change the requirement not met by the implementation. 21.6.6 Conditional items The PICS proforma contains a number of conditional items. These are items for which both the applicability of the item itself, and its status if it does apply—mandatory, optional, or prohibited—are dependent upon whether or not certain other items are supported. Individual conditional items are indicated by a conditional symbol of the form “<item>:<s>” in the Status column, where “<item>” is an item reference that appears in the first column of the table for some other item, and “<s>” is a status symbol, M (Mandatory), O (Optional), or X (Not Applicable). 6 Copyright 2008 IEEE. All rights reserved. IEEE CSMA/CD Std 802.3-2008 If the item referred to by the conditional symbol is marked as supported, then 1) the conditional item is applicable, 2) its status is given by “<s>”, and 3) the support column is to be completed in the usual way. Otherwise, the conditional item is not relevant and the Not Applicable (N/A) answer is to be marked. Each item whose reference is used in a conditional symbol is indicated by an asterisk in the Item column. 21.7 Relation of 100BASE-T to other standards Suitable entries for Table G.1 of ISO/IEC 11801, Annex G would be as follows: a) Within the section Balanced Cabling Link Class C (specified up to 16 MHz): CSMA/CD 100BASE-T2 ISO/IEC 8802-3/DAD 1995 2 CSMA/CD 100BASE-T4* ISO/IEC 8802-3/DAD 1995 4 b) Within the section Optical Link: CSMA/CD 100BASE-FX ISO/IEC 8802-3/DAD 1995 2 c) Within the section Balanced Cabling Link Class D (defined up to 100 MHz): CSMA/CD 100BASE-TX ISO/IEC 8802-3/DAD 1995 2 *To support 100BASE-T4 applications, Class C links shall have a NEXT value of at least 3 dB in excess of the values specified in 6.2.4. Suitable entries for Table G.4 of ISO/IEC 11801, Annex G, would be as follows: aIEEE 802.3 imposes additional requirements on propagation delay. A suitable entry for Table G.5 of ISO/IEC 11801, Annex G, would be as follows: Balanced cabling Performance based cabling per Clause 6 per Clauses 5, 7, and 8 Class A Class B Class C Class D C a t 3 1 0 0 Ω C a t 4 1 0 0 Ω C a t 5 1 0 0 Ω C a t 3 1 2 0 Ω C a t 4 1 2 0 Ω C a t 5 1 2 0 Ω 1 5 0 Ω 1 0 0 Ω 1 2 0 Ω 1 5 0 Ω 1 0 0 Ω 1 2 0 Ω 1 5 0 Ω 1 0 0 Ω 1 2 0 Ω 1 5 0 Ω 1 0 0 Ω 1 2 0 Ω 1 5 0 Ω 802.3: 100BASE-T2 Ia I I I I I I I Ia I I 802.3: 100BASE-T4 Ia I I I I I Ia I 802.3: 100BASE-TX Ia Ia Ia Ia Fibre Optical link per Clause 8 per 5, 7, and 8 Horizontal Building backbone Campus backbone 62.5/ 125 mm MMF 50/ 125 mm MMF 10/ 125 mm MMF 62.5/ 125 mm MM F 50/ 125 mm MM F 10/ 125 mm MM F 62.5/ 125 mm MM F 50/ 125 mm MM F 10/ 125 mm MM F 62.5/ 125 mm MM F 50/ 125 mm MM F 10/ 125 mm MM F 802.3: 100BASE-FX N I N I N I N I Copyright 2008 IEEE. All rights reserved. 7 IEEE Std 802.3-2008 REVISION OF IEEE Std 802.3: 21.8 MAC delay constraints (exposed MII) 100BASE-T makes the following assumptions about MAC performance. These assumptions apply to any MAC operating in half duplex mode with an exposed MII. Table 21–2—MAC delay assumptions (exposed MII) Sublayer measurement points Event Min (bits) Max (bits) Input timing reference Output timing reference MAC MII MAC transmit start to TX_EN sampled 4 TX_CLK rising CRS assert to MAC detect 0 8 CRS de-assert to MAC detect 0 8 CRS assert to TX_EN sampled (worst case nondeferred transmit) 16 TX_CLK rising COL assert to MAC detect 0 8 COL de-assert to MAC detect 0 8 COL assert to TXD = Jam sampled (worst-case collision response) 16 TX_CLK rising; first nibble of jam 8 Copyright 2008 IEEE. All rights reserved. IEEE CSMA/CD Std 802.3-2008 22. Reconciliation Sublayer (RS) and Media Independent Interface (MII) 22.1 Overview This clause defines the logical, electrical, and mechanical characteristics for the Reconciliation Sublayer (RS) and Media Independent Interface (MII) between CSMA/CD media access controllers and various PHYs. Figure 22–1 shows the relationship of the Reconciliation sublayer and MII to the ISO/IEC OSI reference model. The purpose of this interface is to provide a simple, inexpensive, and easy-to-implement interconnection between Media Access Control (MAC) sublayers and PHYs for data transfer at 10 Mb/s and 100 Mb/s, and between Station Management (STA) and PHY entities supporting data transfer at 10 Mb/s or above (see 22.2.4). This interface has the following characteristics: a) It is capable of supporting 10 Mb/s and 100 Mb/s rates for data transfer, and management functions for PHYs supporting data transfer at 10 Mb/s or above (see 22.2.4). b) Data and delimiters are synchronous to clock references. c) It provides independent four bit wide transmit and receive data paths. d) It uses TTL signal levels, compatible with common digital CMOS ASIC processes. e) It provides a simple management interface. f) It is capable of driving a limited length of shielded cable. g) It provides full duplex operation. Figure 22–1—MII relationship to the ISO/IEC Open Systems Interconnection (OSI) reference model and the IEEE 802.3 CSMA/CD LAN model PRESENTATION APPLICATION SESSION TRANSPORT NETWORK DATA LINK PHYSICAL OSI REFERENCE MODEL LAYERS LAN CSMA/CD LAYERS AUI MII MDI MDI = MEDIUM DEPENDENT INTERFACE MII = MEDIA INDEPENDENT INTERFACE MDI 100 Mb/s, 1 Gb/s10 Mb/s MEDIUM PLS PMA PMA PCS PMD HIGHER LAYERS LLC (LOGICAL LINK CONTROL) OR OTHER MAC CLIENT MAC CONTROL (OPTIONAL) MII/GMII MAC—MEDIA ACCESS CONTROL RECONCILIATION PLS = PHYSICAL LAYER SIGNALING PHY PMA = PHYSICAL MEDIUM ATTACHMENT PHY = PHYSICAL LAYER DEVICE PMD = PHYSICAL MEDIUM DEPENDENT AUI = ATTACHMENT UNIT INTERFACE GMII = GIGABIT MEDIA INDEPENDENT INTERFACE MAU = MEDIUM ATTACHMENT UNIT MAU PCS = PHYSICAL CODING SUBLAYER RECONCILIATION MEDIUM Copyright 2008 IEEE. All rights reserved. 9 IEEE Std 802.3-2008 REVISION OF IEEE Std 802.3: 22.1.1 Summary of major concepts a) Each direction of data transfer is serviced with seven (making a total of 14) signals: Data (a four-bit bundle), Delimiter, Error, and Clock. b) Two media status signals are provided. One indicates the presence of carrier, and the other indicates the occurrence of a collision. c) A management interface comprised of two signals provides access to management parameters and services. d) The Reconciliation sublayer maps the signal set provided at the MII to the PLS service definition specified in Clause 6. 22.1.2 Application This clause applies to the interface between MAC sublayer and PHYs, and betwee

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