Copyright © 2008 IEEE. All rights reserved. 1
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 THREE: This section includes Clause 34 through Clause 43 and Annex 36A through
Annex 43C. (Third printing: 22 June 2010.)
34. Introduction to 1000 Mb/s baseband network
34.1 Overview
Gigabit Ethernet couples an extended version of the ISO/IEC 8802-3 (CSMA/CD MAC) to a family of
1000 Mb/s Physical Layers. The relationships among Gigabit Ethernet, the extended ISO/IEC 8802-3 (CSMA/
CD MAC), and the ISO/IEC Open System Interconnection (OSI) reference model are shown in Figure 34–1
.
Gigabit Ethernet uses the extended ISO/IEC 8802-3 MAC layer interface, connected through a Gigabit
Media Independent Interface layer to Physical Layer entities (PHY sublayers) such as 1000BASE-LX,
1000BASE-SX, and 1000BASE-CX, and 1000BASE-T.
Gigabit Ethernet extends the ISO/IEC 8802-3 MAC beyond 100 Mb/s to 1000 Mb/s. The bit rate is faster,
and the bit times are shorter—both in proportion to the change in bandwidth. In full duplex mode, the mini-
mum packet transmission time has been reduced by a factor of ten. Achievable topologies for 1000 Mb/s full
duplex operation are comparable to those found in 100BASE-T full duplex mode. In half duplex mode, the
minimum packet transmission time has been reduced, but not by a factor of ten. Cable delay budgets are
similar to those in 100BASE-T. The resulting achievable topologies for the half duplex 1000 Mb/s CSMA/
CD MAC are similar to those found in half duplex 100BASE-T.
34.1.1 Reconciliation Sublayer (RS) and Gigabit Media Independent Interface (GMII)
The Gigabit Media Independent Interface (Clause 35) provides an interconnection between the Media
Access Control (MAC) sublayer and Physical Layer entities (PHY) and between PHY Layer and Station
Management (STA) entities. This GMII supports 1000 Mb/s operation through its eight bit wide (octet wide)
transmit and receive paths. The Reconciliation sublayer provides a mapping between the signals provided at
the GMII and the MAC/PLS service definition.
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