Ethernet (5.4)
When you are connecting to a network using a wired interface, you are using the Ethernet protocol. Even most wireless networks ultimately connect to a wired Ethernet network. Ethernet is an important data link layer protocol used in LANs and most wide-area networks (WANs).
The Rise of Ethernet (5.4.1)
In the early days of networking, each vendor used its own proprietary methods of interconnecting network devices and networking protocols. If you bought equipment from different vendors, there was no guarantee that the equipment would work together. Equipment from one vendor might not communicate with equipment from another.
As networks became more widespread, standards were developed that defined rules by which network equipment from different vendors operated. Standards are beneficial to networking in many ways:
Facilitate design
Simplify product development
Promote competition
Provide consistent interconnections
Facilitate training
Provide more vendor choices for customers
There is no official local-area networking standard protocol, but over time, one technology, Ethernet, has become more common than the others. Ethernet protocols define how data is formatted and how it is transmitted over the wired network. The Ethernet standards specify protocols that operate at Layer 1 and Layer 2 of the OSI model. Ethernet has become the de facto standard, which means that it is the technology used by almost all wired local-area networks, as shown in Figure 5-8.
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Figure 5-8 The Evolution from Proprietary LAN Protocols to Ethernet
Ethernet Evolution (5.4.2)
The Institute of Electrical and Electronic Engineers, or IEEE (pronounced “eye-triple-e”), maintains the networking standards, including Ethernet and wireless standards. IEEE committees are responsible for approving and maintaining the standards for connections, media requirements, and communication protocols. Each technology standard is assigned a number that refers to the committee that is responsible for approving and maintaining the standard. The committee responsible for Ethernet standards is 802.3.
Since the creation of Ethernet in 1973, standards have evolved for specifying faster and more flexible versions of the technology. This ability for Ethernet to improve over time is one of the main reasons that it has become so popular. Each version of Ethernet has an associated standard. For example, 802.3 100BASE-T represents the 100 megabit Ethernet using twisted-pair cable standards. The standard notation translates as follows:
100 is the speed in Mbps.
BASE stands for baseband transmission.
T stands for the type of cable—in this case, twisted-pair.
Early versions of Ethernet were relatively slow at 10 Mbps. The latest versions of Ethernet operate at 10 gigabits per second and more. Imagine how much faster these new versions are than the original Ethernet networks.
Video—Ethernet Addressing (5.4.3)
Refer to the online course to view this video.
The Ethernet MAC Address (5.4.4)
All communication requires a way to identify the source and destination. The source and destination in human communication are represented by names.
When your name is called, you listen to the message and respond. Other people in the room may hear the message, but they ignore it because it is not addressed to them.
On Ethernet networks, a similar method exists for identifying source and destination hosts. Each host connected to an Ethernet network is assigned a physical address that serves to identify the host on the network.
Every Ethernet network interface has a physical address assigned to it when it is manufactured. This address is known as the Media Access Control (MAC) address. The MAC address identifies each source and destination host on the network, as shown in Figure 5-9.
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Figure 5-9 MAC Addresses Identify Unique Hosts on a LAN
Lab—Determine the MAC Address of a Host (5.4.5)
In this lab, you will complete the following objectives:
Determine the MAC address of a Windows computer on an Ethernet network using the ipconfig /all command.
Analyze a MAC address to determine the manufacturer.