Data Communications Systems: Ethernet

Ethernet is a packet-switching transmission protocol that is primarily used in LANs. Ethernet is often characterized by its data transmission rate and type of transmission medium (e.g., twisted pair is T and fiber is F). Ethernet systems in 1972 operated at 1 Mbps. In 1992, Ethernet progressed to 10 Mbps data transfer speed (called 10BaseT). In 2001, Ethernet data transfer rates included 100 Mbps (100BaseT) and 1 Gbps (1000Base T). In the year 2000, 10 Gigabit fiber Ethernet prototypes had been demonstrated.

Ethernet can be provided on twisted pair, coaxial cable, wireless, or fiber cable. In 2001, the common wired connections for Ethernet was 10 Mbps or 100 Mbps. 100 Mbps Ethernet (100BaseT) systems are also called “Fast Ethernet.” Ethernet systems that can transmit at 1 Gbps (1 Gbps = 1 thousand Mbps) or more, are called “Gigabit Ethernet (GE).” Wireless Ethernet have data transmission rates that are usually limited from 2 Mbps to 11 Mbps.

Wired Ethernet conforms to IEEE 802.3 standards and wireless Ethernet conforms to 802.11. IEEE 802.3 standard and uses carrier sense multiple access with collision detection (CSMA/CD) media access control (MAC).

Ethernet is the older than token ring and is based on linear bus technology. Originally installed using RG-6/8 coaxial cable (called “thicknet”), it was used for high-speed bus applications to interconnect mainframes and mini-computers. With the growth of personal computer (PC) workstations in the 80’s and early 90’s, a new wiring strategy was implemented using thinner RG-58 coaxial cable (called “thinnet”). In the mid-90’s newer twisted pair standards were set and higher speeds were achieved. 10 Mbps (10BaseT) became achievable on Category 3 unshielded twisted pair (UTP) wire.

Because Ethernet systems can use different cabling systems (e.g., twisted pair and coax), network interface cards (NICs) must contain a connector that is compatible with the cabling systems. Some NIC cards come with multiple connectors. The different types of connectors include:

  • DB-15 AUI connector for thicknet, 10Base5

  • BNC coaxial connector for thinnet, 10Base2

  • RJ-45 for twisted pair, 10BaseT or 100BaseT.

  • The maximum distance between devices in an Ethernet network is determined by the type of cable selected and performance of the NIC. Figure 1 shows different types of Ethernet LAN systems and the approximate distances devices can be connected together in these networks. Thicknet Ethernet uses a low loss coaxial cable to provide up to 500 meters of interconnection without the need for repeaters. Thinnet systems use a relatively thin coaxial cable systems and the typical signal loss in this cable restricts the maximum distance to approximately 185 meters. 100 BaseT systems use category 5 UTP cable and the maximum distance is approximately 100 meters.

    Figure 1: Ethernet

    No comments:

    Telecom Made Simple

    Related Posts with Thumbnails