COMPUTER NETWORKS HIMA 4160 Fall 2009 House Keeping

COMPUTER NETWORKS HIMA 4160 Fall 2009

House Keeping • Assignment 3 is due next Thursday

LEARNING OBJECTIVES • Define a network and its purpose. • Describe several uses for communications technology. • Understand the various topologies and architectures a computer network might use. • Explain the difference between a LAN, a WAN, and a PAN, and between an intranet, an extranet, and a VPN.

LEARNING OBJECTIVES, CONT’D • Understand characteristics about data and how it travels over a network. • Name specific types of wired and wireless transmission media and explain how they transmit data. • Identify different protocols that can be used to connect the devices on a network. • List several types of networking hardware and explain the purpose of each.

OVERVIEW • This class covers: Networking concepts and terminology Common networking and communications applications Technical issues related to networks, including the major types of networks, how data is transmitted over a network, and types of transmission media involved o Explanation of the various ways networked devices communicate with one another o Various types of hardware used in conjunction with a computer network o o o

WHAT IS A NETWORK? • Network: a connected system of objects or people • Computer network: a collection of computers and other hardware devices connected together so that users can share hardware, software, and data, as well as electronically communicate with each other • Internet: largest computer network

WHAT ARE SOME OF THE APPLICATIONS OF NETWORKING AND COMMUNICATION?

NETWORKING AND COMMUNICATIONS APPLICATIONS • Mobile phones (wireless phones) o Cellular (cell) phones (most common) o Satellite phones (used where cell service isn’t available) o Wi-Fi phones

NETWORKING AND COMMUNICATIONS APPLICATIONS, CONT’D • Paging: sending short numeric or text messages to a person’s pager o Most often used for onsite paging applications • Messaging: two-way paging o Most often takes place today via a mobile phone

NETWORKING AND COMMUNICATIONS APPLICATIONS, CONT’D • Global positioning system (GPS): Uses satellites and a receiver to determine the exact geographic location of the receiver o o o Commonly found in cars today Available as handheld units Used by the military, hikers, travelers, and others who need to know their precise location

NETWORKING AND COMMUNICATIONS APPLICATIONS, CONT’D • Monitoring systems—monitor status of or location of individuals, vehicles, assets, etc. o Electronic medical monitors o GPS-based monitoring systems o RFID short-range monitoring systems • Monitoring via the Internet Satellite radio—delivers digital radio content to satellite receivers, which can be o Car-mounted o Placed in the home o Carried around o

NETWORKING AND COMMUNICATIONS APPLICATIONS, CONT’D • e. ICU: use of communications technology to monitor ICU patients remotely o Remote monitoring and consultations

NETWORKING AND COMMUNICATIONS APPLICATIONS, CONT’D • Videoconferencing: use of communications technology for real-time, face-to-face meetings between individuals located in different places o Online conferencing (via the Internet) o Dedicated videoconferencing room o Video phone calls • Collaborative computing (workgroup computing): using a computer and communications technology to work together on documents and other project components

NETWORKING AND COMMUNICATIONS APPLICATIONS, CONT’D • Telecommuting: individuals work at home and communicate with their place of business and clients via communications technologies • Digital data distribution: transferring digital data(digital photos, music, movies, TV broadcasts, medical imaging files, etc. ) electronically from one place to another o Home use o Business use o Digital movie distribution

NETWORKING AND COMMUNICATIONS APPLICATIONS, CONT’D • Telemedicine: use of communications technology to provide medical information and services o Remote monitoring and consultations o Remote diagnosis o Tele-surgery

TYPES OF NETWORKS • Networks can be identified by their o Topology (physical arrangement) o Architecture (the way they are designed to communicate) o Size (how large of an area the network services)

NETWORK TOPOLOGIES • Star networks (all devices connect to a central device or hub) • Bus networks (all devices connect to a central cable) • Ring networks (devices connect to one another in a ring) • Mesh networks (multiple connections between devices) • Some networks use a combination of topologies

Network Architecture • Client-server • Peer to peer

NETWORK ARCHITECTURES • Client-server networks o o Client: PC or other device on the network that requests and utilizes network resources Server: computer dedicated to processing client requests

NETWORK ARCHITECTURES, CONT’D • Peer-to-peer networks (all computers at the same level) o Internet peer-to-peer (P 2 P) computing: performed via the Internet

Network Size • • LAN WAN MAN PAN Intranet Extranet VPN

LANS, WANS, AND OTHER TYPES OF NETWORKS • Local area network (LAN): covers a relatively small geographical area, such as a home, office building, or school • Wide area network (WAN): covers a large geographical area; may consist of two or more LANs, which could be relatively close to one another (such as in the same city) or far apart • Metropolitan area network (MAN): designed for a metropolitan area, typically a city or county

LANS, WANS, AND OTHER TYPES OF NETWORKS, CONT’D • Personal area network (PAN): connects personal devices for one individual, such as his or her portable PC, cell phone, and portable printer • Intranet: private network, such as a company LAN, set up by an organization for use by its employees • Extranet: intranet that is at least partially accessible to authorized outsiders • Virtual private network (VPN): group of secure paths over the Internet that provide authorized users a secure means of accessing a private network via the Internet

HOW DOES DATA TRAVEL OVER A NETWORK? • Data transmitted over a network has specific characteristics • Data can travel over a network in various ways • Network devices can communicate through a o o Wired connection: via physical cables Wireless connection: typically through radio signals

DATA TRANSMISSION CHARACTERISTICS • Analog vs. digital: continuous wave vs. discrete 0 s and 1 s • Bandwidth (throughput): amount of data that can be transmitted over a communications medium at one time (higher bandwidth will deliver data faster) • Serial vs. parallel transmission Serial: one bit a time (more common in communication) o Parallel: at least one byte at a time o

DATA TRANSMISSION CHARACTERISTICS, CONT’D • Transmission timing Synchronous transmission (at regular, specified intervals) o Asynchronous transmission (sent when ready) o Isochronous transmission (sent at the same time as other related data) o • Transmission directions o o o Simplex transmission (one way only) Half-duplex transmission (one way at a time) Full-duplex transmission (both ways at the same time)

WIRED VS. WIRELESS CONNECTIONS • Wired network connection: the PC is physically cabled to the network o Common in schools, business, and government facilities • Wireless networks: typically use radio waves to send data through the air o Rapidly becoming more popular in homes and businesses; wireless hotspots are commonly available in public locations

WIRED NETWORK TRANSMISSION MEDIA • Twisted-pair cable o o Pairs of wires twisted together Used for telephone and network connections • Coaxial cable o o Thick center wire Used for computer networks, short-run telephone transmissions, cable television delivery • Fiber-optic cable Glass or fiber strands through which light can pass o Used for high-speed communications o

WIRELESS NETWORK TRANSMISSION MEDIA • Broadcast radio transmissions o Short-range (such as Bluetooth): can connect a wireless keyboard or mouse to a PC o Medium-range (such as Wi-Fi): used for wireless LANs and to connect portable PC users to the Internet at public hot spots • Microwave and satellite transmissions o Microwave stations (earth based) o Communications satellites (placed in orbit)

Unites States Frequency Allocations The Radio Spectrum

Wireless Network Transmission Media, Cont’d

WIRELESS NETWORK TRANSMISSION MEDIA, CONT’D • Cellular radio transmissions o Use cellular towers within cells o Calls are transferred from cell tower to cell tower as the individual moves o o Different transmission frequencies are used to avoid interference and allow multiple conversations to take place via a single tower at one time Widely used, but cell service not available everywhere

ETHERNET • Ethernet: a widely used communications protocol for LANs o o o Typically used with LANs that have a bus or star topology and use twisted-pair or coaxial cables Original (10 Base-T) Ethernet networks run at 10 Mbps; newer 100 Mbps and 1 Gbps versions are now available Utilizes a set of procedures (CSMA/CD) to send data and make sure it arrives

COMMUNICATIONS PROTOCOLS • Communications protocol: an agreed-upon standard for transmitting data between two devices on a network • Protocols specify how o Devices physically connect to a network o Data is packaged for transmission o Receiving devices acknowledge signals (handshaking) o Errors are handled

TOKEN RING • Token Ring: Communications protocol usually used with a ring network topology o Utilizes a token to send and retrieve data o Token circulates in one direction o Token is either free or carries a message to be delivered to a device o Each device checks to see if the message is addressed to it o Devices can grab a free token and add a message

WI-FI (802. 11) • Wi-Fi (802. 11): family of wireless networking standards o o 802. 11 b: original standard (11 Mbps) 802. 11 a (Wi-Fi 5): about five times faster than 802. 11 b; more expensive, uses a different radio frequency (5 GHz) than 802. 11 b (2. 4 GHz), making the two standards incompatible 802. 11 g: current Wi-Fi standard; supports data transfer rates of 54 Mbps; it uses the same 2. 4 GHz frequency as 802. 11 b, so their products are compatible 802. 11 n (Fast Wi-Fi): in development, 248 MBps speed.

MESH NETWORKS, WIMAX, MOBILE-FI, AND XMAX • Mesh networks: use a mesh topology, so messages can take any of several possible paths from source to destination o Used to connect wireless networks o Can be used to enlarge hotspot areas o Can be used to allow emergency workers to communicate with one another o Most often used to create MANs

MESH NETWORKS, WIMAX, MOBILEFI, AND XMAX, CONT’D • Wi. MAX (802. 16): emerging wireless networking standard that is faster and has a greater range than Wi-Fi Expected to provide fast wireless Internet access over a distance of up to 30 miles o Mobile Wi. MAX is under development o • Mobile-Fi (802. 20): high-speed mobile Internet technology currently in development o Expected to be used while moving, such as in cars and trains • x. Max: recently developed, for longer range wireless connections; uses unused portions of radio channels

BLUETOOTH • Bluetooth: communications standard for very short-range wireless connections o o o The devices are automatically connected once they get within the allowable range Designed for communications between personal devices (within 10 meters or 33 feet), such as keyboards and PCs, cell phones and earpieces, PCs and printers, etc. Devices form piconets of up to 8 devices each

ULTRA WIDEBAND (UWB) • Ultra Wide Band (UWB): another short-range wireless technology o Faster and has a greater range than Bluetooth o Originally developed for the military in the 1960 s o o Beginning to be used to wirelessly network consumer multimedia devices to wireless deliver digital data (video, music, photos, etc. ) Emerging Bluetooth standards may use UWB to speed up connections between devices

TCP/IP AND WIRELESS APPLICATION PROTOCOL (WAP) • TCP/IP: Protocol used for transferring data over the Internet o Uses packet switching to facilitate the transmission of messages o Packets are sent separately and reassembled at the final destination o Also used with home networking • Wireless Application Protocol (WAP): Standard for delivering content, such as Web pages, to mobile devices

PHONELINE AND POWERLINE NETWORKS • Phone line or Home PNA standard o Allows computers to be networked through ordinary phone wiring and phone jacks, without interfering with voice telephone calls o Geared toward setting up quick and easy home networks • Powerline standard o Allows PCs to be networked over existing power lines using conventional electrical outlets o Emerging standard will also connect home entertainment devices

NETWORKING HARDWARE • Network adapters: used to connect a PC to a network o Also called network interface card (NIC) when in the form of an expansion card o Come in a variety of formats § PCI § USB § PC Card • Adapter must match the type of network being used (Ethernet, Wi-Fi, Bluetooth, etc. )

NETWORKING HARDWARE, CONT’D • Modem: device that connects a computer to the Internet o Term used even if not connecting via a phone line o Type of modem needed depends on the type of Internet access being used § Conventional dial-up § ISDN § DSL § Cable § Satellite

NETWORKING HARDWARE, CONT’D • Hubs, switches, routers, and wireless access points: used to connect devices and route data to the devices on a network o Hub: all data goes to all devices o Switch: data goes to just appropriate device o Router: more efficiently delivers data o Wireless access point: connects wireless devices to a wired network o Some devices contain more than one of these capabilities

NETWORKING HARDWARE, CONT’D • Gateways and bridges: connect one network to another o Gateway: connects dissimilar networks o Bridge: connects similar networks • Repeaters: amplify signals on a network so they can travel further • Multiplexers and concentrators: combine transmissions from multiple devices to send over a medium and then separates them again at the destination

OSI sample protocols 1. Physical: T 1, 802. 11 a/. b/g/n etc. 2. Data Link: MAC, ethernet etc. 3. Network: IP etc. 4. Transport: TCP, UDP etc. 5. Session: Net. BIOS etc. 6. Presentation: ASCII, MPEG etc. 7. Application: FTP, HL 7, Http, SMTP, Telnet etc.

SUMMARY • What is a Network? • Networking and Communications Applications • Types of Networks • How Does Data Travel Over a Network? • Communications Protocols • Networking Hardware