Principles and technologies of local area networks - Intelligent Buildings and Building Automation - page 63

Table 4.1 LAN standards of IEEE 802 series

Data Link Layer

Logical Link Control Media Access Control Physical Layer

Baseband coaxial 10/100 Mbps
Twisted pair 1, 10, 100 Mbps

CSMA/CD
802.3

Broadband coaxial 10 Mbps

Optical fibre 100/1000 Mbps

Broadband coaxial 1, 5, 10 Mbps

802.2 LLC
Logical Link Control

Token Bus
802.4

Carrier band 1, 5, 10 Mbps

Optical fibre 5, 10, 20 Mbps

Twisted pair 4, 16 Mbps

Token Ring
802.5

Unshielded twisted pair 4 Mbps

FDDI
(Token Ring)

Optical fibre 100 Mbps

IEEE 802.2 LLC: The main task of LLC is to even out differences in the
various types of local area network, so that there is no need for higher-level
software to take these differences into account. However, the LLC layer is
seldom used. In most cases this sub-layer is omitted in order to increase effi-
ciency. In such cases, the layer above, e.g. IP, works directly with the MAC
layer. So the software must be configured specially for the underlying layer
used in each case. In most cases this is the IEEE 802.3 Ethernet.

4.5 Examples of LAN technologies in applications

4.5.1 Ethernet (IEEE 802.3)

The term Ethernet refers to the family of LAN products covered by the IEEE
802.3 standard that defines what is commonly known as the CSMA/CD
protocol. Three data rates are currently defined for operation over optical-
fibre and twisted-pair cables: 10 Mbps (10Base-T Ethernet), 100 Mbps (Fast
Ethernet) and 1 Gbps (Gigabit Ethernet). Ethernet of even higher speed, such
as 10 Gigabit Ethernet, is under development.
Other technologies and protocols have been promoted as likely replace-
ments, but the market has made its selection. Ethernet has survived as the
major LAN technology in PC and workstation networks. It is also one of the
most popularly used LAN technologies in BA networks nowadays. Ethernet
protocol has the following characteristics. It: