Presentation is loading. Please wait.

Presentation is loading. Please wait.

Telecommunications and Networks Chapter 6 – Understanding Technology (Third Edition)

Similar presentations

Presentation on theme: "Telecommunications and Networks Chapter 6 – Understanding Technology (Third Edition)"— Presentation transcript:

1 Telecommunications and Networks Chapter 6 – Understanding Technology (Third Edition)

2 William M. Pegram2 Data Transmission Characteristics Bandwidth – number of bits per second that can be transferred over a given medium (broadband vs. narrowband) Analog vs. digital – modems convert digital signals into analog form so that an analog medium (such as a telephone line) can carry these signals; at the other end, modems convert the analog signal back into digital form

3 William M. Pegram3 Data Transmission Characteristics (cont.) Parallel vs. serial transmission – in parallel transmission, bits are transmitted at the same time, one bit per path whereas in serial transmission, the bits are transmitted one after another Universal Serial Bus (USB) is a type of high-speed serial transmission

4 William M. Pegram4 Wired Communications Media Twisted-pair cable – telephone lines (“dial up”) Coaxial cable – commonly used for VCR and cable television connections – up to 10Mbps (million bits per second) Note that transmission speeds are given in bits whereas file sizes are normally quoted in bytes Integrated Services Digital Network (ISDN) lines – 64-128K (now made somewhat obsolete by cable and DSL)

5 William M. Pegram5 Wired Communications Media (cont.) Digital Subscriber Line (DSL) – 144K-1.56Mbps, uses existing copper telephone lines Fiber optic cable – light transmitted along string of glass – FIOS, offered by Verizon, is offering speeds in some markets up to 10Mbps upload and 50Mbps download T1 line – digital telephone connections up to 1.54Mbps T3 line – up to 44.7 Mbps - used for ISPs connecting to the internet backbone and the backbone itself

6 William M. Pegram6 Wireless Communications Media Microwave – stations at line-of-sight intervals Satellite – In geosynchronous orbit (which means they are always over the same point on Earth) – 22,236 miles above earth Cellular Infrared – e.g. wireless keyboard, mouse Wi-Fi – Wireless LAN technology based on the 802.11 IEEE standards Bluetooth – Short range (e.g. 15-20 feet)

7 William M. Pegram7 Networks Classified by Architecture Client-server – Networked personal computers, workstations, or terminals (clients) send requests and receive services from another computer (server) Peer-to-peer – Computers in the network have equal responsibilities

8 William M. Pegram8 Networks Classified by Coverage Local Area Networks (LANs) – private networks with computers located in the same area – LAN uses a special computer, called file server, to house all the network resources; Ethernet is the most commonly used LAN technology Wide Area Networks (WANs) – span two or more LANs Virtual Private Network (VPN) – offices can communicate as if they were within the same corporate network, even though they are using the internet to connect with each other

9 William M. Pegram9 Networks Classified by Users Intranets – internal users; access to intranet is typically protected by a firewall Extranet – external users have access to internal applications and data via the Internet – usernames and passwords

10 William M. Pegram10 Network Topologies Bus topology – all computers (nodes) are linked via a single line of cable – all communications travel the length of the bus –Terminator is a device that absorbs signals so they do not reflect back down the line Star topology (hub-and-spoke topology) – computers and devices are linked to a central computer called the host Ring topology – Each computer is connected to two other computers in a circular path

11 William M. Pegram11 Network and Communications Hardware Hub – Electronic device in older LANs to link computers Switch – Similar to hub, but can inspect data packets and forward to the appropriate destination Repeaters (amplifiers) – increase strength of signals and send along the network Router - used in large networks including the internet, used to connect different networks to ensure messages sent to the correct destination

12 William M. Pegram12 Network and Communications Hardware (cont.) Gateways – hardware or software that allow communication between dissimilar networks Bridge – hardware or software that allows communication between similar networks

13 William M. Pegram13 Communications Protocols Hypertext Transfer Protocol (HTTP) Simple Mail Transfer Protocol (SMTP) – sends email between servers Post Office Protocol (POP) – retrieves email from server, newest version is POP3 Internet Message Access Protocol (IMAP) – retrieves email from server Transmission Control Protocol/Internet Protocol (TCP/IP) – host computers on internet File Transfer Protocol (FTP) – allows large files to be transferred over the internet

14 William M. Pegram14 Directional Protocols Simplex – Communications flow in only one direction Half-Duplex – Communications can flow in both directions, but not at the same time Full-Duplex – Simultaneous transmission in both directions is possible

15 William M. Pegram15 Determining Stop and Start of Transmission Asynchronous transmission – Each byte is surrounded by control bits – start bit and stop bit – also there is an error checking bit called a parity bit Synchronous transmission – Blocks of bytes are wrapped in start and stop bytes

16 William M. Pegram16 Wireless Application Protocols Internet Protocol (IP) Wi-Fi (802.11 protocol) –802.11b (up to 11MB) – uses the 2.4 GHz band –802.11a (up to 54Mbps if within 60 feet) – uses the 5 GHz band –801.11g (transfer rates similar to a)- uses the 2.4 GHz band and compatible with b devices –802.11n (up to 74MB) – not approved yet but products sold

17 William M. Pegram17 NVCC Courses ITN 100 – Introduction to Telecommunications (required for AS in IT degree) ITN 101 – Introduction to Network Concepts

Download ppt "Telecommunications and Networks Chapter 6 – Understanding Technology (Third Edition)"

Similar presentations

Ads by Google