CertiGuide to A+ (A+ 4 Real)  9  Chapter 13: Basic Networking Terminology       9  OSI Reference Model and Networking Protocols and Technologies            9  Layer 2 - Data Link Layer

Duplex 1 CSMA/CD

Ethernet is the most widespread standard in local area networks. The total number of networks using this protocol is estimated to be in the range of 30 million ranges. With the rising of the nominal speed to 1000 bps and higher in 2005, the supporting of Quality of Service parameters, this network technology finds its switched variant in such spheres as storage networks and metropolitan infrastructures.

Historically, Ethernet has appeared based on an experimental network: Ethernet Network for the Xerox Company in 1975. In 1980 DEC, Intel and Xerox developed and published the standard for Ethernet of Version 2 for a network based on coaxial cabling. Based on the given standard the IEEE 802.3 standard was developed. The differences can be found in the 2nd layer of OSI and divided between two sub layers - MAC and LLC.

The technician must distinguish the type of cable ¹⁸⁴ being used: 10Base-5, 10Base-2, 10Base-T ¹⁸⁵, 10Base-FL and 10Base-FB. Each one working on 10Mbps will differ in distance accessibility in communication.

In 1995, the standard Fast Ethernet was accepted which was named 802.3u, working at the speed of 100Mbps at 100 meters with a UTP cable.

In 1998, the standard Gigabit Ethernet 802.3z was accepted, working at the speed of 1000Mbps at 100 meters.

In summer of 2002, 10 Gigabit Ethernet (10GigE) standards were accepted and it was named IEEE-803.2ae, working at the speed of 10000Mbps with 8 different interfaces – at 65m, 300m and 10 and 40 km. Ethernet has become high-speed in division technologies. With its productivity, it is like OC-192 SONET/SHD ¹⁸⁶, but in price, it is 10 times cheaper. 10GigE allows you to refuse expensive technologies such as, Dense Wavelength Division Multiplexing (DWDM). It is easy to migrate to 10GigE if the basic infrastructure is there. Another advantage is flexibility in bandwidth when contrasted to SONET/SDH, whose speed of transfer can only have a specific predetermined value, but a 10GigE-required bandwidth can be configured on demand so that metropolitan users can regulate bandwidth in accordance with their real needs.

In 2005, by experts’ opinion, 40-Gigabit Ethernet standards will have been accepted.

Ethernet uses a method of division in the transfer medium - CSMA/CD (carrier-sense-multiply-access with collision detection), but the last two standards used fiber optic duplex technology.

Duplex 1 CSMA/CD