Communications and Networks Reading: Chapter 9

Why are networks so useful? 60 They facilitate communications They allow for sharing of resources Both of the above

Network Uses of communications technologies Network Internet Global Positioning System (GPS) Short Message Service (SMS) Network Interconnected group of computers and devices connected via communications devices and media Facilitates sharing of resources and supports communications Requires Sending & receiving devices Communications devices Communications channel or path Network OS (NOS)

Networks – Communications Devices Hardware capable of sending/receiving data Convert signals so that they are suitable for the communications channel May convert between analog and digital Common types Dial-up modems ISDN and DSL modems Cable modems Network interface cards Wireless access points Routers

Networks – Communications Devices Dial-up Modem Modulate/demodulate External modem Connects to serial or RS-232 port Internal modem Card inserted to expansion slot/PC Slot ISDN and DSL Modems Do not modulate/demodulate External Sends and receives data over a digital telephone line ISDN line DSL line

Networks – Communications Devices Cable modem Cable television network Faster than dial-up access or ISDN line Splitter runs separate cables to TV’s and cable modem External USB port or Ethernet NIC via a cable Network Interface Card (NIC) Coordinates transmission/receipt of data to/from the device Card installed in an expansion slot of a PC, printer, PC slot Wireless transmission includes antenna Works with a particular network technology Ethernet or token ring

Networks – Communications Devices Hub Provides a central point of connectivity for cables in a network May include a router Router Connects multiple computers and routers together Transmits packets to correct destination May include built-in firewall Wireless access point Allows computers and devices to communicate wirelessly Allows data transfer to a wired network

Communications devices include ______. 45 routers hubs modems NICs All of the above

Networks – Communications Channels Communications path between two devices Transmission rate Speed at which data flows through the channel Bandwidth of the channel Bits per second (bps), Hertz (cycles per second) Transmission media Materials or techniques capable of carrying one or more signals Baseband media – carry one signal at a time Broadband media – carry multiple signals concurrently Physical transmission media Twisted pair, Coaxial, Fiber Optic Wireless transmission media Infrared, Radio Frequency, Infrared, Microwave

Networks – Physical Transmission Media Twisted-pair cable Used for network cabling and telephone systems One or more twisted-pair wires bundled together Each pair has two insulated copper wires twisted together Coaxial cable (coax) Used for network cabling and cable TV Single copper wire surrounded by 3 layers Insulating material Woven/braided metal Plastic outer coating

Networks – Physical Transmission Media glass cladding optical fiber core Fiber optic cable Light used to send signals Thin glass or plastic strands Surrounded by insulating glass cladding and a protective coating Carries many signals High speed Less noise Smaller size Expensive, difficult to install and modify Protective coating

Networks – Physical Transmission Media

All of the following except ______ are examples of physical media. 45 coaxial cable twisted pair microwave cable fiber optic cable

Networks – Wireless Transmission Media Radio Frequency Antenna, transmitter, receiver Bluetooth (2.45 GHz) 802.11b & g (2.4 GHz) Cellular Radio Waves Cell phones, mobile devices High frequency radio waves 824 to 849 MHz Microwaves High-speed signal transmission Signals sent between microwave stations Fixed-point wireless Requires line-of-sight Communications Satellites Satellite receives microwave signal and amplifies Retransmits over wide-area, to a number of land-based stations Infrared Signals IR light waves with line-of-sight transmission

Networks – Wireless Transmission Media

All of the following except ______ are examples of wireless media. 45 microwaves satellites radio frequency waves fiber optic waves

Networks Classified according to Geography – Geographic Distribution LAN MAN WAN Architecture Topology Protocol/Communications Technology

Networks – Geographic Distribution Local Area Network (LAN) Connects computers in a limited geographical area Each computer and device is a node Metropolitan Area Network (MAN) High-speed network that connects LANs in a metropolitan area Managed by a consortium of users or a single network provider

Networks – Geographic Distribution Wide Area Network (WAN) Connects computers and devices in a large geographical area Connected via many types of media One large network or two or more interconnected LANs, MANs Others CAN HAN TAN

A ______ is a network that encompasses a limited geographic area. 45 MAN WAN LAN PAN

Networks Classified according to Geography Architecture – Broad outline of the network Peer-to-Peer Client/Server Topology Protocol/Communications Technology

Network Architectures – Client/Server and Peer-to-Peer printer Client/Server Server controls resources More storage space, power Serves as a repository Dedicated servers Client relies on the server for access to resources Peer-to-Peer Share peripheral devices Up to 10 “peer” computers NOS & applications software, storage Internet Peer-to-Peer (P2P) Users connect directly to each other’s hard disk Popular, inexpensive

Networks Can be classified according to Geography Architecture Topology – Physical arrangement of devices connected to the network Bus Ring Star Networks often use a combination of topologies Protocol/Communications Technology

Network Topologies – Bus and Ring Networks Bus Network Single central cable connects computers and devices Transmits in both directions If a device fails, network continues to function Reliable Popular, inexpensive Ring Network Cable forms a closed ring Transmits in only one direction If one device fails, all those after the device cannot function Spans larger distance than bus network LANs and WANs

Network Topologies – Star and Other Networks Star Network Devices connect to a central computer Hub If one device fails, only that device is affected Hub fails Other Topologies Mesh Redundant interconnections between nodes Tree Star networks connected together via a bus

With ______ topology, the devices on the network are connected together in a closed loop. 45 bus ring star tree

Networks Can be classified according to Geography Architecture Topology Protocol/Communications Technology – Standards that govern how data/instructions flow over the network Ethernet Token Ring TCP/IP WAP Others

Networks – Network Communications Technologies Communications Protocol Set of rules and procedures for exchanging information among computers Ethernet Token ring TCP/IP WAP Others

Network Communications Technologies – Ethernet Widely used LAN standard Developed by Xerox, DEC, Intel - 1976 Fast Ethernet (100Base-T) - 100 Mbps Gigabit Ethernet - 1000 Mbps 10-Gigabit Ethernet – 10 Gbps Bus or star topology PCs in the network to contend for access Collision

Network Communications Technologies – Token Ring Ring or star topology LAN standard Passes a signal called a token Special bit pattern Only device with token can transmit Device catches the token, attaches message , sends it to travel around the network to receiving device Receiving device catches token, strips off the message, resends token

Network Communications Technologies – TCP/IP Used to connect hosts on the Internet Includes several protocols Transmission Control Protocol and Internet Protocol Data broken up into small packets Origin information Destination information Sequence information Data/information/instructions Packet switching Break up message into packets, route packets, destination reassembles the message Routers direct packets individually along fastest path

Network Communications Technologies – WAP Wireless Application Protocol (WAP) Access Internet via mobile devices 2.0 Specification Open Mobile Alliance (OMA) Web sites provide wireless content to display on microbrowsers WML – XML application designed for small screens

Network Communications Technologies – 802.11, Bluetooth, IrDA IEEE 802.11 (802.11b, g – “WiFi”) Family of standards used with wireless LANs Used for public Internet access points Bluetooth Devices contain special chip Short-range radio waves transmit between Bluetooth devices Short distance IrDA IrDA devices contain IrDA ports Infrared light waves Line-of-sight transmission

With TCP/IP is used to send data over the Internet, the data is divided into small pieces or ______. 45 bundles packets tokens hubs

Networks – Intranets Intranet Internal network in an organization used to share information Uses Internet technologies (TCP/IP, Web server, Web pages) Enterprise network Connects to the Internet Extranet - Allows outside user access Firewall Designed to prevent unauthorized access to a private network Firewall blocks messages that do not meet security criteria Uses hardware, software, combination of both All messages entering or leaving the intranet must pass through the firewall

Networks – Home Area Networks (HAN) Network within a home Connects digital devices HomePLC – electrical lines; cables connect card/USB/parallel port to wall outlet Phoneline – telephone lines; cables connect NIC/PC card to telephone jack Network card that plugs into PCI slot and wall outlet for home power-line network Howstuffworks.com HomeRF, 802.11b – radio waves; NIC connects to transceiver with antenna or to wireless access point Ethernet – twisted pair cables; Ethernet NIC cards and cables to connect devices

Do you have a home area network? 30 Yes No

Networks Summary Uses of Communications Technology Networks Communications Devices Communications Channels Physical and Wireless Transmission Media Geographic LAN, MAN, WAN Architectures Peer-to-Peer, Client/Server Topologies Bus, Ring, Star Protocols Ethernet, Token Ring, TCP/IP, WAP, 802.11, others Intranets and Firewalls Home Networks