Consistent Behavior over All Links Using the Ethernet Data-Link Layer Although Ethernet includes many physical layer standards, Ethernet acts like a single LAN technology because it uses the same data-link layer standard over all types of Ethernet physical links. That standard defines a common Ethernet header and trailer. (As a reminder, the header and trailer […]

Typical Enterprise LANs Enterprise networks have similar needs compared to a SOHO network, but on a much larger scale. For example, enterprise Ethernet LANs begin with LAN switches installed in a wiring closet behind a locked door on each floor of a building. The electricians install the Ethernet cabling from that wiring closet to cubicles […]

Foundation Topics An Overview of LANs The term Ethernet refers to a family of LAN standards that together define the physical and data-link layers of the world’s most popular wired LAN technology. The standards, defined by the Institute of Electrical and Electronics Engineers (IEEE), define the cabling, the connectors on the ends of the cables, the […]

“Do I Know This Already?” Quiz Take the quiz (either here or use the PTP software) if you want to use the score to help you decide how much time to spend on this chapter. The letter answers are listed at the bottom of the page following the quiz. Appendix C, found both at the […]

Chapter Review The “Your Study Plan” element, just before Chapter 1, discusses how you should study and practice the content and skills for each chapter before moving on to the next chapter. That element introduces the tools used here at the end of each chapter. If you haven’t already done so, take a few minutes […]

OSI Networking Model and Terminology At one point in the history of the OSI model, many people thought that OSI would win the battle of the networking models discussed earlier. If that had occurred, instead of running TCP/IP on every computer in the world, those computers would be running with OSI. However, OSI did not […]

Data Encapsulation Terminology As you can see from the explanations of how HTTP, TCP, IP, and Ethernet do their jobs, when sending data, each layer adds its own header (and for data-link protocols, also a trailer) to the data supplied by the higher layer. The term encapsulation refers to the process of putting headers (and sometimes […]

TCP/IP Data-Link and Physical Layers The TCP/IP model’s data-link and physical layers define the protocols and hardware required to deliver data across some physical network. The two work together quite closely; in fact, some standards define both the data-link and physical layer functions. The physical layer defines the cabling and energy (for example, electrical signals) […]

Internet Protocol Addressing Basics IP defines addresses for several important reasons. First, each device that uses TCP/IP—each TCP/IP host—needs a unique address so that it can be identified in the network. IP also defines how to group addresses together, just like the postal system groups addresses based on postal codes (like ZIP codes in the […]

TCP/IP Network Layer The application layer includes many protocols. The transport layer includes fewer protocols, most notably, TCP and UDP. The TCP/IP network layer includes a small number of protocols, but only one major protocol: the Internet Protocol (IP). In fact, the name TCP/IP is simply the names of the two most common protocols (TCP […]