Data Communications Networking Devices - 4th Ed.pdf

3.4 ETHERNET NETWORKS ________________________________________________________ 303Figure 3.13 Using a repeater. Cable segments can be joined together by a repeater R) toexpand the network. The repeater counts as a station on each cable segmentIEEE 802.3 networksThe IEEE 802.3 standard is based on Ethernet. However, it has several signi®cantdifferences, particularly its support of multiple physical layer options, whichinclude 50 and 75 ohm coaxial cable, unshielded twisted-pair wire, an operating rateof 100 Mbps for two recently standardized versions of Ethernet, and a pendingstandard referred to as Gigabit Ethernet that will support data transmission at 1Gbps. Other differences between various types of IEEE 802.3 networks andEthernet include the data rates supported by some 802.3 networks, their method ofsignaling, the maximum cable segment lengths permitted prior to the use ofrepeaters, and their network topologies.Network namesThe standards thad de®ne IEEE 802.3 networks have been given names thatgenerally follow the form `s type-1'. Here , s refers to the speed of the network inMbps, type is BASE for baseband and BROAD for broadband, and 1 refers to themaximum segment length in 100-meter multiples. Thus, 10BASE-5 refers to anIEEE 802.3 baseband network that operates at 10 Mbps and has a maximumsegment length of 500 meters. One exception to this general form is 10BASE-T,which is the name for an IEEE 802.3 network that operates at 10 Mbps usingunshielded twisted-pair UTP) wire.Table 3.9 compares the operating charateristics of six currently de®ned IEEE802.3 networks to Ethernet.10BASE-5An examination of the operating characteristics of Ethernet and 10BASE-5indicates that these networks are the same.