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
The Domain Name system
every device connected to the Internet (or another TCP/IP network) is assigned a unique Internet Protocol (IP) address – string of numbers
Domain Name System (DNS): converts domain names into IP addresses
Top domain level extensions / top-level domains: .com, .gov, .dk, .org
Second-level domains: google, congress, expedia,
Third level domain (host): sales –> sales.google.com
IPv6 (Internet Protocol version 6)
128 bit IP addresses
Since we were running out of IP addresses using 32 bit IP addresses, IPv6 is replacing them, and the system is still getting implemented which will take a few years
The Internet Infrastructure (Client/Server computing architecture)
Users control what they do on the Internet through client applications on their computers, such as web browser software
The data (including emails and web pages) are stored on servers, so when the client uses the Internet to request information from a web server, the server sends the information back to the client over the Internet
Client platforms today include computers as well as smartphones and tablets
Example: if you watch a video online, it is most likely stored in a database server, and then served to you through the web server you are connecting to through your desktop or mobile device over the Internet
See model
Voice over IP (VoIP)
VoIP technology delivers voice information in digital form using packet switching, avoiding the tolls charged by local and long-distance telephone networks
Because some packets might arrive sooner than others with packet switching, sometimes this can cause e.g. the voice to come before the video, which then stays frozen for a bit
Virtual Private Networks (VPN)
virtual private network (VPN) is a secure, encrypted, private network that has been configured within a public network to take advantage of the economies of scale and management facilities of large networks, such as the Internet
Hypertext
Web pages are based on a standard Hypertext Markup Language (HTML), which formats documents and incorporates dynamic links to other documents and other objects stored in the same or remote computers
Your computer accesses web pages using the Hypertext Transfer Protocol (HTTP), which is the communication standard for transfers pages on the web
Uniform Ressource Locator (URL): HTTP, the domain name, sometimes directory path and web page name –> helps the browser track down the requested page
Web Servers
software for locating and managing stored web pages. It locates the web pages a user requests on the computer where they are stored and delivers the web pages to the user’s computer
Web 2.0
second generation of internet based tools and services that enable users to easily generate content, share media, communication and collaborate in innovative ways
Web 2.0 are all tools and services provided over the Internet which have four key characteristics: interactive, real-time user control, social participation, user-generated content
Examples of web applications that share those charactertics: blogs (user generated websites), Wikis (created and edited by users), Social networking (communication and connect, e.g. Facebook), Social bookmarking (favourite sites with bookmarks using tags, e.g. Pinterest)
The date in Web 2.0 applications get richer as more people use them (add more content)
Digital Platform (Web 2.0 platform example) (players in a platform + examples of platforms)
The platform connects the producers (who are independent from the platform) to the consumers
E.g. Uber drivers are self employed, gets connected to riders using the platform, whereas a taxi company is not a digital platform since the taxi drivers are employed with the company
It is more attractive for producers to enter a platform is there are many customers on the platform, and the platform is more attractive for customers if there are a lot of producers
Examples: Amazon, Ebay, GoMore (book a lift with someone else), Uber, Facebook
The Future Web (4 trends)
Internet of Things (IoT): the growing use of sensors in industrial and consumer products –> smart products: the information comes from sensors in other products, such as an activity watch
The App Internet: growth of apps within the mobile platform, which is faster than loading browsers because you get direct access to the content
Cloud computing business model
Software as a Service (SaaS) business model
Search engine (and Search Engine Optimization)
Special software applications employed by a search engine continuously surf the visible web and for every new page they encounter, they store a copy on it on the search engine’s own servers, where they are indexed
When you enter a keyword, it is matched against the database of stored webpages and you on the client is shown the search engine page results (SEPR)
Search Engine Optimization (SEO): hundreds of criteria to rank websites, so managers of commercial web pages are motivated to find ways to increase visibility through optimizing content, maximizing inbound links, improving user traffic = search engine optimization (SEO)
Search Engine Criteria / Ranking factors
On-page criteria: how many times the keyword is present in the website, how frequently the website is updated
Off-page criteria: how many other websites link to a specific page, how important are the websites that link to it (important so that when you search “the white house”, the Actual White House comes first)
Behavioral data: the more users a page has, the higher it appears in search results
Spam filter: some web masters try to game the system by hiring people to click on the links and increase traffic, but the search engine system is set up to identify spam attempts (too many clicks from one IP address)
Network effect
The value of a network is proportional to the number of people in it
Web 2.0 has revolutionized the way value is produced in many industries
Network Neutrality
The idea that all internet traffic should be treated equally by Internet Service Providers (ISPs), regardless of the size, source or nature of the content
