Understanding Networks II

1. Understanding Networks II

2. Objectives • Compare client and network operating systems • Learn about local area network technologies, including Ethernet, Token Ring, FDDI, and wireless • Use the OSI model to understand networking • Learn how network computers and servers are addressed

3. Network Architecture Overview • Network architecture is the overall design of a network, including how devices and components are connected, how devices and components communicate, and the network protocols needed to establish reliable communication among nodes on the network.

4. Network Architecture Overview • A node is any device that can be accessed by a computer on a LAN, such as a computer, server, or printer. • Physical topology is the physical arrangement or shape in which devices on a LAN are connected to each other.

5. How NICs Work • Typically, an internal NIC plugs into a motherboard expansion slot. • An individual NIC can be designed to support Ethernet, Token Ring, FDDI, or wireless architectures, but a single card will not support multiple architectures. • The NIC must convert the data it is transmitting into a signal that is in a form that is appropriate for the network. • The component on the card responsible for this signal conversion is called the transceiver.

6. How Ethernet Controls Data Traffic • An Ethernet network is a passive network, meaning that the network just sits there and waits for a computer to use it. • A computer that wants to send packets over Ethernet first listens on the network for silence. • If it hears nothing, it begins to transmit. • As it transmits, it also listens.

7. How Ethernet Controls Data Traffic (Continued) • If it hears something other than its own data being transmitted, it stops transmitting and sends out a signal indicating that there has been a collision, which occurs when two computers attempt to send data at the same time. • A collision can cause packets that were just sent to be corrupted. • Each computer waits for a random amount of time and then tries to transmit again, first listening for silence.

8. How Ethernet Controls Data Traffic (Continued) • This type of network technology is called a contention-based system because each computer must contend for an opportunity to transmit on the network. • Computers using Ethernet gain access to the network using the CSMA/CD (Carrier Sense Multiple Access with Collision Detection) method. • Another method that can be used by a network technology to control collisions is CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance).

9. Ethernet Hardware • Three variations of Ethernet are available, primarily distinguished from one another by speed: 10-Mbps Ethernet, Fast Ethernet, and Gigabit Ethernet. • A hub is a network device that can be used to connect devices that use a BNC or RJ-45 connector. • A hub, like the one shown in Figure 5-20, is generally inexpensive and is best suited for a small, simple network. • These devices can include computers, servers, or printers.

10. Ethernet Hardware (Continued) • Hubs are easy to configure because they broadcast data packets to every device at once. • A switch is used to connect computers on a LAN. • A switch reads the destination address at the beginning of a data packet and sends the packet only to the destination computer. • Attenuation occurs when signals are weakened due to being transmitted over long distances on a network.

11. Ethernet Hardware (Continued) • A repeater is a device that amplifies signals on a network. • There are two kinds of repeaters. • An amplifier repeater simply amplifies all incoming signals. • A signal-regenerating repeater reads the signal and then creates an exact duplicate of the original signal before sending it on.

12. Physical Topology • A bus topology connects each node in a line and does not include a centralized point of connection; cables just stretch from one computer to the next one, and to the next, and so on. • A star topology connects all nodes to a centralized hub or switch.

13. Physical Topology (Continued)

14. Wireless LAN • Wireless LAN (WLAN) technology, as the name implies, uses radio waves or infrared light instead of cables or wires to connect computers or other devices. • Connections are made using a wireless NIC, which includes an antenna to send and receive signals. • Wireless devices can communicate directly, or they can connect to a LAN by way of a wireless access point (AP).

15. Wireless LAN (Continued) • Access points are placed so that nodes can access at least on one access point from anywhere in the covered area. • The first IEEE standard that outlined wireless LAN specifications was IEEE 802.11, published in 1990. • Most current WLAN devices operate under the 1999 IEEE 802.11b standard. • This standard is also called Wi-Fi (Wireless Fidelity).

16. Token Ring and FDDI • Token Ring is an older LAN technology developed by IBM that transmits data at 4 Mbps or 16 Mbps. • A Token Ring network is physically arranged using a star topology, because each node connects to a centralized device. • The centralized device to which the network nodes connect is not a hub or switch, as used in Ethernet networks, but is called a Controlled Access Unit (CAU), a Multistation Access Unit (MSAU or sometimes just MAU), or a Smart Multistation Access Unit (SMAU).

17. Token Ring and FDDI (Continued) • A token is a special series of bits used to control which device transmits data on the network. • Because it has a physical star topology and a logical ring topology, a Token Ring network is sometimes said to have a star-wired ring topology. • Token Ring can also use another type of connector that has no “male” or “female” version, known as a Universal Data Connector (UDC) or an IBM Data Connector (IDC).

18. Token Ring and FDDI (Continued) • Fiber Distributed Data Interface (FDDI) is a type of network that also involves a token that travels in a ring. • With FDDI, data frames travel on the ring without the token, and multiple nodes can have data on the ring at the same time.