Transcript document
Hardware Concepts Chapter 4 Contents • Explain the different types of network topology • Describe the different types of network cabling • Describe and distinguish between the 802.2, 802.3, 802.5, and 802.11 IEEE networking standards Topology Topology • A topology describes how computers connect to each other Types of Topologies • Bus – All computers connect via a main line, called a bus cable • Ring – All computers attach to a central ring of cable • Star – All computers connect to a central wiring point, usually a hub • Mesh – Each computer has a dedicated line to every other computer Types of Topologies Network Technologies • A network technology is a practical application of a topology to get data from one computer or network to another – Ethernet – Token Ring – FDDI-(Fiber Distributed Data Interface) is a standard for data transmission on fiber optic lines in a local area network (LAN) that can extend in range up to 200 km Bus Topology • Ethernet was the first network technology that used the bus topology • Each computer on the network is connected to the single cable Bus Topology • If there is a break in the cable, the entire network would stop functioning – It has no fault tolerance to survive a problem Star Topology • Each computer is connected to a central device such as a hub – If a cable breaks only the one computer is affected Star Bus Topology • A star bus topology is a hybrid topology – Uses a physical star topology – Uses a logical bus topology – Most common topology used today Token Ring Topology • Token ring uses a star ring topology – Uses a physical star topology – Uses a logical ring topology – Declining in popularity Cabling Coax • Coaxial cable (or coax) contains a central conductor wire, surrounded by an insulating material, which in turn is surrounded by a braided metal shield EMI • Electro-magnetic interference (EMI) is caused by lights, fans, copy machines, and other devices • EMI corrupts the signal flowing through the cable • The braided shield helps to reduce the effects of EMI Types of Coax Cable • The Ohm rating is a measure of resistance in the cable and differentiates different types of coaxial cable • RG-8, RG-62, and RG-58 are used in computer networks RG-8 • RG-8 cable is also called Thick Ethernet – Oldest type of coax still in use – Rated at 50 ohms – Yellow or orange/brown color RG-62 • RG-62 cable is never installed in networks today – Was used with ARCnet RG-58 • RG-58 is also called Thin Ethernet – Still in widespread use today Twisted Pair • Shielded Twisted Pair (STP) and Unshielded Twisted Pair (UTP) are the most common types of cabling used today – Composed of multiple pairs of wires twisted together to reduce interference from adjacent wires, called crosstalk Shielded Twisted Pair (STP) • Twisted pairs of wires surrounded by shielding to protect them from EMI – Only used in older Token Ring networks Unshielded Twisted Pair (UTP) • Most common type of cabling used in networks – Twisted pairs of wires surrounded by a plastic jacket – Inexpensive and flexible CAT Ratings • Twisted pair cabling varies by things like the number of twists per foot • Cables are rated in categories or CAT ratings (or levels) CAT Ratings CAT Rating Bandwidth Typical Throughput in Networks CAT 1 <1 MHz Analog phone lines – not data CAT 2 4 MHz Speeds up to 4 Mbps CAT 3 16 MHz Speeds up to 16 Mbps CAT 4 20 MHz Speeds up to 20 Mbps CAT 5 100 MHz Speeds up to 100 Mbps CAT 5e 100 MHz Speeds up to 1000 Mbps CAT 6 200-250 MHz Speeds up to 10000 Mbps CAT Usage • Most new installations use CAT 5e cable since it is cheaper than CAT 6 cable CAT level CAT level Fiber Optic • Fiber optic cabling transmits light rather than electricity – Immune to EMI – Very long distances – Consists of the fiber, cladding, and insulating jacket – Defined by fiber and cladding measurements – Most common is 62.5/125 µm – Fiber generally requires two cables Light Sources • Fiber optic cables use two possible light sources – Light Emitting Diodes (LEDs) – called multimode – Lasers – called single-mode • Supports faster speeds and longer lengths Networking Industry Standards IEEE • Institute of Electrical and Electronic Engineers (IEEE) defines industry-wide standards • Organized the 802 committee in February of 1980 to define networking standards – Split up into smaller subcommittees IEEE Subcommittees IEEE 802 LAN/MAN Overview & Architecture IEEE 802.2 Logical Link Control (LLC) IEEE 802.3 CSMA/CD access method (Ethernet) IEEE 802.3ae 10 Gigabit Ethernet IEEE 802.5 Token Ring access method and Physical layer specifications IEEE 802.8 Fiber Optic IEEE 802.11 Wireless LAN Medium Access Control (MAC) and Physical layer specifications There are more subcommittees than listed in this table.