Bài giảng Network+ Certification - Chapter 2, Network Hardware

Chapter 2, Network Hardware |1| Chapter Overview A. Network Cables B. Network Interface Adapters C. Network Hubs Chapter 2, Lesson 1 Network Cables |2| 1. Cable Topologies |3| A. Bus topology 1. Uses coaxial cable 2. Used by thick and thin Ethernet networks 3. The nodes are connected in series. 4. A bus network must be terminated at both ends. 5. The signals transmitted by a computer travel in both directions. 6. Cable faults affect the entire network. a. A cable fault breaks the network in two, preventing signals from passing from one segment to the other. b. The lack of termination on the broken ends further degrades performance. |4| B. Star topology 1. Most common topology used in LANs today a. Used primarily with Ethernet 2. Uses various cable types, especially unshielded twisted pair (UTP) 3. Requires a hub (or concentrator) 4. Computers are connected to the hub, not to each other. 5. Cable faults affect only one computer. 6. The hub is a central point of failure, but hub faults are rare. |5| C. Ring topology 1. A ring network is like a bus network with the two ends connected. 2. Used primarily by Token Ring and Fiber Distributed Data Interface (FDDI) protocols 3. Most (but not all) ring networks are logical rings. a. The physical network takes the form of a star. 4. Most ring networks use the token passing Media Access Control (MAC) mechanism. |6| 5. In a physical ring, a cable fault affects the entire network. 6. A logical ring is physically cabled as a star and has the fault tolerance of a star network. 7. FDDI can use a physical ring topology or a double ring topology. 8. Double ring topology 2 Outline, Chapter 2 Network+ Certification, Second Edition a. Consists of two separate rings, with traffic flowing in opposite directions b. Requires a computer to have a network interface with two jacks c. If a cable fails, traffic is shunted to the other ring. |7| D. Hierarchical star topology 1. Also known as a branching tree network 2. Expands a star network beyond a single hub E. Mesh topology |8| 1. Mesh LANs a. Mesh LANs are generally theoretical; LANs do not actually use them. b. In a mesh LAN, every computer is directly connected to every other computer. |9| 2. Mesh internetworks a. In a mesh internetwork, there are multiple routes to a destination. b. Mesh internetworks use redundant routers to provide fault tolerance. |10| F. Wireless topologies 1. Wireless LANs have two basic topologies: ad hoc and infrastructure. a. Ad hoc topology. Connects two or more wireless computers communicating only with each other b. Infrastructure network. Connects wireless computers communicating with a wireless interface device called a network access point (1) The network access point provides access to a standard cabled network. 2. Cable Types |11| A. Coaxial cable 1. Consists of two conductors separated by insulation: a. A central core that carries the signals b. A copper mesh that surrounds the central core and functions as a ground 2. Used on LANs only for thick and thin Ethernet 3. Obsolete on LANs today |12| 4. RG-8 type a. Thick Ethernet b. 0.405 inch thick c. Uses N connectors d. The sheath is often yellow (“frozen yellow garden hose”). e. Uses a separate Attachment Unit Interface (AUI) cable to connect the computer to the RG-8 cable 5. RG-58 type a. Thin Ethernet b. 0.195 inch thick c. Uses bayonet-Neill-Concelman (BNC) connectors with a T fitting, which plug into the computer Outline, Chapter 2 3 Network+ Certification, Second Edition |13| B. Twisted-pair cable 1. UTP cable contains eight separate insulated wires twisted into four pairs. a. Each pair is twisted at a different rate, to prevent crosstalk and outside interference. 2. Twisted-pair cables are traditionally wired straight through; all circuit crossovers are performed in the hub. 3. Crossover cables are available for special applications (such as hubless, two-node networks). 4. Individual wires can be solid or stranded. a. Solid wires are stiffer but carry signals better and are used for longer runs. b. Stranded wires are more flexible and are used for shorter runs. 5. Uses RJ-45 connectors |14| 6. Unshielded twisted-pair (UTP) cable a. Most popular cable type for LANs b. Classified in six categories by the Electronics Industry Association/Telecommunications Industry Association (EIA/TIA) (1) Most UTP networks installed today use Category 5 cable. (2) Some legacy networks use Category 3, the standard grade for voice telephone cabling. 7. Shielded twisted-pair (STP) cable a. Contains two pairs of wires b. Each pair is individually shielded. c. Originally used on IBM Token Ring networks d. Rarely used today e. Type 1A cables are used for longer runs. f. Type 6A cables are used for shorter patch cables. g. Uses IBM data connectors (IDCs) h. Used in environments vulnerable to electromagnetic interference |15| C. Fiber optic cable 1. Uses glass or plastic filaments 2. The signals are pulses of light, not electrical charges as with copper- based cables. 3. Used for FDDI, fiber optic Ethernet, and many types of wide area network (WAN) technologies 4. Offers several advantages: a. Impervious to electromagnetic interference b. More resistant to attenuation than copper is c. More secure than copper cable 5. Contains a single conductor surrounded by reflective cladding and a protective sheath |16| 6. Typically uses straight tip (ST) or subscriber connector (SC) connectors 7. The cable size is referenced by the diameter of the core followed by the diameter of the cladding, measured in microns. 4 Outline, Chapter 2 Network+ Certification, Second Edition a. Example: 62.5/125 |17| 8. There are two primary types of fiber optic cable: singlemode and multimode. a. Singlemode fiber optic (1) Typical size: 8.3/125 (2) More expensive than multimode (3) Uses a single-wavelength laser light source (4) Used for long-distance cable runs (5) Generally used for WANs b. Multimode fiber optic (1) Typical size: 62.5/125 (2) Less expensive than singlemode (3) Uses a light-emitting diode (LED) light source (4) Cannot span distances as long as singlemode fiber optic cable can (5) Used mostly in LAN installations Chapter 2, Lesson 2 Network Interface Adapters |18| 1. Understanding Network Interface Adapter Functions A. A network interface adapter is known as a NIC when it is installed in an expansion slot. B. Provides the computer with an interface to the network C. Usually takes the form of an expansion card that plugs into one of the following: 1. Peripheral Component Interconnect (PCI) bus 2. Industry Standard Architecture (ISA) bus 3. PC Card bus D. Can be integrated into the motherboard |19| E. Functions 1. Data-link layer protocol implementation (with a network adapter driver) 2. Data encapsulation 3. Signal encoding and decoding 4. Data transmission and reception 5. Data buffering 6. Serial/parallel conversion 7. Media Access Control (MAC) |20| F. What to check for when purchasing a NIC 1. Does the NIC use the correct data-link layer protocol? 2. Does the NIC use the correct bus type? 3. Does the NIC have the correct network cable connector? Outline, Chapter 2 5 Network+ Certification, Second Edition 2. Installing a NIC |21| A. To install a NIC into a standard expansion slot on a desktop computer: 1. Power off the computer. 2. Open the computer case. 3. Locate a free slot. 4. Remove the slot cover. 5. Insert the card into the slot. 6. Secure the card in the slot. 7. Close the computer case. 3. Configuring a NIC A. NICs need access to hardware resources in order to communicate with the computer. |22| B. NICs use the following hardware resources: 1. Interrupt request (IRQ) 2. Input/output (I/O) port address 3. Memory address 4. Direct memory access (DMA) channel C. Most NICs require only an IRQ and an I/O port address. 4. Installing Network Adapter Drivers A. Every network interface adapter requires a driver. B. Network adapter drivers must be configured to use the same hardware resources as the adapter itself. |23| 5. Troubleshooting a Network Interface Adapter A. A network interface adapter rarely malfunctions. B. Before checking the network interface adapter, check the following for problems: 1. Check the adapter’s connections to the computer and the network. 2. Check the driver. 3. Check the configuration of the computer’s other networking components. 4. Check the network cable by swapping it with one that you know is functional. C. NIC manufacturers sometimes provide a diagnostic program. 1. If the diagnostic program finds a problem with the card, open the computer and examine the NIC. 2. Ensure that the NIC is fully seated in the slot. D. Replace faulty NICs rather than trying to repair them. 6 Outline, Chapter 2 Network+ Certification, Second Edition Chapter 2, Lesson 3 Network Hubs |24| 1. Understanding Ethernet Hubs A. A hub is a device used to connect all of the computers on a star or ring network. 1. Also called a concentrator or a multiport repeater 2. Usually a physical-layer device B. Available in various sizes 1. The number of ports varies from 4 to 24 or more. 2. Some hubs are small, inexpensive, standalone devices intended for home or small business networks. 3. Larger hubs can be stacked together or mounted in a rack. C. The hub creates a shared network medium on a LAN. 1. Functions as a repeater: a device that amplifies signals to counteract the effects of attenuation 2. When signals enter any of the hub’s ports, the hub amplifies them and transmits them through all of the other ports. 3. Hub ports have a crossover circuit that routes the transmit signals generated by one computer to the receive inputs of the others. 4. Ethernet hubs are in most cases purely electrical devices that work with signals at their most basic level. a. The hub does not read the contents of data packets or even recognize them as data packets. D. Smart hubs (also known as intelligent hubs) have greater data processing capabilities, including the following services: 1. Store and forward a. The hub contains buffers used to store packets temporarily before it retransmits stored packets out through specific ports. b. Function approaches that of a switch (as covered in Chapter 3, “Network Connections”) 2. Managed hub a. Uses Simple Network Management Protocol (SNMP) to transmit periodic reports to a network management console b. Allows you to monitor the operation of each port |25| E. Connecting Ethernet hubs 1. Most hubs have an uplink port (an extra port used to connect to other hubs). a. The uplink port provides a straight-through circuit, while the other ports all have crossovers. b. The uplink port can sometimes be switched to a standard port. 2. To connect two hubs, you plug a cable into the uplink port on one hub and into a standard port on the other hub. Outline, Chapter 2 7 Network+ Certification, Second Edition |26| 2. Understanding Token Ring MAUs A. A multistation access unit is called a MAU (or MSAU). B. Similar in appearance to an Ethernet hub, but very different in function C. MAUs are not repeaters. D. MAU functions 1. MAUs receive signals through one port and transmit them out through the next port in line. 2. Computers connected to a MAU are responsible for transmitting all signals they receive from the MAU back to the MAU. 3. By sending signals to and receiving them back from each connected computer in turn, the MAU implements the logical ring topology. E. Each port on a MAU must be initialized to add the connected computer to the ring network. |27| Chapter Summary A. The network topology is the pattern used to connect computers and other devices with the cable or other network medium. B. The three primary LAN topologies are bus, star, and ring. C. UTP cable in the star topology is the most common network medium used today. D. A network interface adapter provides the interface that enables a computer to connect to a network. E. The network interface adapter and its driver implement the data-link layer protocol on the computer. F. Hubs are devices that connect computers on a star or ring network.