Digital Network Technologies Flashcards
Computer network
two or more connected computers
a simple computer network can contain computers, a network operating system (NOS) residing on a dedicated server computer, cable (wiring) connecting the devices, switches, and a router –> see image
Networking operating system (NOS): routes and manages communications on the network and coordinates network resources – either resides on every computer or on a dedicated server computer, which displays web pages, stores data and NOS
Includes a hub or a switch: hubs connects network components through sending data packets to all connected devices, whereas switches are more intelligent and can filter and forward data to a specified destination on the network
Router: communications processor that routes data packets through different networks, ensuring it gets sent to the correct address
Software-defined network (SND)
Network approach where many of the normal network components and control functions are managed by one central program which runs on servers separate from the network devices themselves
Useful for cloud computing where many pieces of hardware because it allows network administrators to manage traffic loads in a flexible and more efficient manner
Corporate network infrastructure (connecting small networks)
Small networks can be tied together into a corporate-wide networking infrastructure, which consists of a large number of the small local area networks linked together to other local area networks and to firm-wide corporate networks
Powerful servers support a corporate website, intranet and extranet, and some of these servers link to other large computers supporting back-end systems
See model
Client/Server Computer
distributed computing model where some of the processing power is located within small inexpensive client computers (desktops or laptops or in handheld devices), and which are linked through a network controlled by a network server computer
largely replaced mainframe computing
Packet Switching
method of slicing digital messages into parcels called packets, sending the packets along different communication paths as they become available and then reassembling the packets once they arrive at their destinations
data travelling through the network are represented by digital signals (sequences of 1s and 0s), which are sliced into smaller packets that can be more easily managed to travel over a network
it routes each packet different ways until they reach their destination and are assembled –> more reflible and resilient to disruption because they can take a million different paths
TCP / IP — Transmission Control Protocol / Internet Protocol:
a single common worldwide standard –> ensures computers can communicate regardless of their hardware
TCP: handles movement of data between computers by establishing a connection between the computers, sequences the transfer of packets and acknowledges the packets sent
IP: delivery of packets, including disassembling and reassembling packets during transmission
Four-Layered model of TCP/IP: Data passes down the four layers and from the network interface layer to the other computer, where it travels up the layers and are reassembled into a format the receiving computer can use
See model
Signals (Digital vs Analog)
Analog signal: a continuous waveform that passes through a communications medium, such as telephone handset, speakers on electronic devices
Digital signal: discrete binary waveform (rather than a continuous waveform), which communicates information as strings of two discrete states: 1 bits and 0 bits, which are represented as on-off electrical pulses
Modem: modulator-demodulator, used to convert digital signals into analog signals that can be sent through and received by telephone lines, cable lines and wireless media that uses analog signals
Modem (converts digital signals into analog signals) – 3 types
modulator-demodulator, used to convert analog signals into digital signals to send via packet switching, and from digital signals into analog signals that can be sent through and received by telephone lines, cable lines and wireless media that uses analog signals
Cable modems: connect your computer to the Internet using a cable network
DSL modems: connect your computer to the Internet using a telephone company’s landline network
Wireless modems: connects your computer to a wireless network that could be a cell phone network or a WiFi network
See model
Local Area Network (LAN)
Connects personal computers and other digital devices within a half-mile or 500-meter radius
Few computers in a small office, all computers in one building or all the computers in several buildings in close proximity
The server determines who gets access to what and in which sequence. The router connects the LAN to other networks, which could be the Internet, or another corporate network, so that the LAN can exchange information with networks external to it
Client/server architecture: operating system resides primarily on a single server, and the server provides much of the control and resources for the network
Peer-to-peer architecture: treats all processors equally and is used primarily in small networks with ten or fewer users. The various computers on the network can exchange data by direct access and can share peripheral devices without going through a separate server.
Wide Area Network (WAN)
Broad geographical distance (regions, states, continents, entire globe)
The Internet is an example
Computers connect to WAN through public networks such as the telephone system of private cable systems
Metropolitan Area Network (MAN)
Spans a metropolitan area, usually a city and its major suburbs
Geographical scope between WAN and LAN
Bandwidth (transmission speed)
total amount of digital information that can be transmitted through any telecommunications medium is measured in bits per second (bps)
Bandwidth: the range of frequencies that can be accommodated on a particular telecommunications channel
The bandwidth is the difference between the highest and lowest frequencies that can be accommodated on a single channel
The greater the range of frequencies, the greater the bandwidth and the greater the channel’s transmission capacity
Internet Service Provider (ISP)
a commercial organization with a permanent connection to the Internet that sells temporary connections to retail subscribers
Used to be mainly through telephone lines but high speed broadband has replaced it
Digital Subscriber Line (DSL)
technologies operate over existing telephone lines to carry voice, data, and video at transmission rates ranging from 385 Kbps to over 100 Mbps, depending on usage patterns and distance
Cable Internet connections
provided by cable television vendors use digital cable coaxial lines to deliver high-speed Internet access to homes and businesses
