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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.

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 is optional.

100BASE-T

Baseband

Repeater

Unit

Figure 21–1—Architectural positioning of 100BASE-T

Set

OR OTHER MAC CLIENT

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

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