InfoTech Final Exam NYU

Telecommunications

the transmittal of data and information from one point to another; allows communications over large distances

Bandwidth

speed at which data is communicated
- also called transmission rate or bit rate

Bits per Second (bps)

unit of measure for bandwidth

Broadband

communications medium that can carry multiple transmissions simultaneously
ex. cable television, digital subscriber line (DSL), fiber-optic cables, and most wireless connections

Order of bps

bps: bits per second

Kbps: thousand bps

Mbps: million bps (mega bps)

Gbps: billion bps (giga bps)

Tbps: trillion bps (tera bps)

Tangible Media

includes twisted pair cable, coaxial cable, and optical fiber

Twisted Pair Cable

pairs of insulated copper wires twisted together
- flexible, reliable, and low cost
- connects devices with RJ-45 plug-in connector

Coaxial Cable

for cable television transmission
-used for internet connections via cable

Optical Fiber

uses light to represent bits
- not susceptible to electromagnetic interference (EMI)
- can carry signals for long distances

Electrical Power Lines

electrical power grid can be used for telecommunication
- Boradband over Power LInes (BPL) or Power Line Communication (PLC)

Intangible Media

includes media that we can’t physically touch / hold

- includes microwaves & radio waves

Radio Frequency (RF) Technologies

use radio waves to carry bits
- electromagnetic waves between 30 KHz and 300 GHz (or 300 billion waves that pass a given point in a second)
- usually a foot long to several miles long

Microwaves

high-frequency radio waves (a type of radio wave) that can carry signals over long distances with high accuracy (such as for radio and TV)
- electromagnetic waves are between 300 MHz and 300 GHz
- for outside transmission, weather conditions such as rain, pollen, etc. may degrade the quality
- microwave signals can be transmitted by satellite links
- used in cell phones, Bluetooth, etc. that's why it is considered dangerous to keep your phone nearby

WiFI

somewhere between microwaves and radiowaves

Radio Frequency Identification (RFID)

uses radio frequency to transmit data
- enables rapid transactions and payments
used at gas stations for payment at pump
used in vehicles for automatic road toll payment
- used to track and locate items in warehouses

How RFID Works

Tags are tiny and need little power
- objects are embedded with tags that contain a transponder ( a radio transciever activated by a signal transmitted to it)
- reader decode data stored in tag's memomry and pass the data to a host computer
- efficient for large companies, but expensive for smaller companies

Near-Field Communication (NFC)

a standard protocol to create a radio connection between two devices
- takes place within four centimeters
- found in phones and smart watches

- applications such as mobile payment, electronic wallets, opening lockers, getting information

Network Media Acquisition Considerations

1. Availability
2. Current and potential bandwidth
3. Vulnerability to EMI and radio frequency interference (RF!)

Twisted Pair Cable factors

Availability: high
Bandwidth: low to medium
Vulnerability to EMI: high

Radio Waves factors

Availability: high
Bandwidth: medium to high
Vulnerability to EMI: low (but vulnerable to RFI)

Microwave factors

Availability: low
Bandwidth: high
Vulnerability to EMI: low

Coaxial Cable factors

Availability: high
Bandwidth: high
Vulnerability to EMI: low

Optical Fiber factors

Availability: moderate but growing
Bandwidth: highest
Vulnerability to EMI: nonexistant

Electrical Power Lines (BPL) factors

Availability: very high
Bandwidth: high
Vulnerability to EMI: high

LiFi

uses light waves instead of radio waves to transfer data
- often implemented via light emitting devices such as lightbulbs

Network

combination of devices (or nodes) connected through a communication media
- any compatible device that can transmit and receive on a network can be part of a network

Basic Types of Networks

1. Personal Area Network (PAN)

2. Local Area Network (LAN)

3. Metropolitan Area Network (MAN)

4. Wide Area Network (WAN)

Local Area Networks (LAN)

established by a single organization and share among employees
- reaches 5 to 6 km

Server-Based LAN

central server controls communications

Peer-to-Peer LAN

no central device

WiFi (Wireless Fidelity)

same as a Wireless Local Area Network (WLAN), where radio waves is used to connect devices to each other and to the internet

Wireless LANS (WLANS) and Wifi Advantages

- easier installation
- more scalable
- more flexible; equipment is easily moved

Scalability

ease of expanding a system

WLAN Drawback

wireless networks are less secure than wired LANS

Metropolitan Area Network (MAN)

links multiple LANS within a large city
- uses fiber optic or wireless broadband connections between LANS
- up to 50 km (31 miles)
- often used by cities, hospitals within a city, etc.

Wide Area Network (WAN)

far-reaching system of networks composed of LANs or MANs
- may be public or private
- more than 48 km (30 miles)

Personal Area Network

wireless network designed for handheld and portable devices
- used by one or two people
- transmission speed is slower
- maximum distance is about ten meters

Virtual Private Network (VPN)

a public network that creates the illusion of a private network connection
- does not require leasing of lines
- utilizes the internet to simulate a private network that only authorized users can access
- enables the use of intranets and extranets

Why do companies use VPNS?

- greater security and privacy for companies
- people who want to protect their search history, or not face censorship of any sort

(in foreign countries with restricted content, people use VPNs to access banned content: facebook in China)

Protocol

set of rules governing communication between computers

- Most important set of protocols for telecommunications and networks is called TCP/IP

Ethernet

LAN protocol (IEE 802.3) using coaxial or CAT 5 or 6 twisted pair cable, usually used for LANs

Gigabit Ethernet

faster Ethernet connection of one Gbps or greater

IEE 802. 11

a family of wireless protocols known as WiFI
- supports wireless communication within 100 meters of router
- subtypes support various distances and speeds up to 248 Mbps

Access Point (AP)

connection between wireless device and a wired network

Hotspot

allows internet access within range of equipment

Bluetooth

(IEEE 802.15) allows devices to communicate within 10 meters
- transmits voice and data
- considered a PAN technology

Worldwide Interoperability for Microwave Access (WiMAX)

increases the range and speed of wireless communication
- works with metropolitan area networks (MANs); can be used as a back-up network
- would enable internet connection while in a moving vehicle

Wireless Protocol Summarized:

Protocol | Max Range | Max Speed | Main Use

802.11a | 75m (250 ft) | 54 Mpbs | LAN

802.11b | 100m (330 ft) | 11 Mbps | LAN

802.11g | 100m (330 ft) | 54 Mbps | LAN

802.11n | 160m (530 ft) | 248 Mbps | LAN

802.15 (Bluetooth) | 10m (33 ft) | 1 Mbps | PAN

802.16 (WiMax) | 50 km (30 miles) | 100 Mbps | MAN

802.11ac | 90m (300 ft) | new up to 1 GB | LAN

802.11ax| 120m (400 ft) | up to 9.6 Gbps | LAN

First Generation (1G)

analog using circuits switching (required large phones, poor quality); 2.4kbps

Second Generation (2G)

provided digital voice encoding (could not handle data or video, but allowed texting); 1Mbps

Third Generation (3g)

increased speeds of digital encoding that support video, videoconferencing, and full internet access; up to 2Mbps

Fourth Generation (4G)

digital only, with packet switching and tighter security, much faster (up to 1 Gpbs)

Fifth Generation (5G)

will be rolled out over next few years, much higher data speeds (up to 20 Gbps)

Long-Term Evolution (LTE)

a standard method of wireless communications, specifically for high-speed data transmission for mobile phones

Downstream

speed of receiving from network

Upstream

speed of transmitting to network

Network Services Takeaway

services with lower rates for upstream than downstream are suitable for most individuals and businesses

Network Services comparison chart:

Service | Downstream speed | Availability | Monthly $

Dial-up | 56 Kbps | Universal | $9-11

BPL | 0.25-3 Mbps | Limited availability | $20-40

Cable | 0.5-3 Mbps | Widespread | $30-50

DSL | 0.25-1.5 Mbps | little less widespread | $30-50

TI | 1.5 Mbps | Widespread | $250-500

T3 | 45 Mbps | Widespread | $4,000-16,000

Satellite | 0.5-10 Mbps | Widespread | $50-70

Fixed Wireless | 100 Mbps | Limited, spread | $30-50

FTTH | 5-30 Mbps | Limited, spread | $350

OC-3 | 155 Mbps | Limited availability | $10K-45K

OC-12 | 622 Mbps | Limited availability | hundreds K

OC-48 | 2.5 Gbps | Limited availability | hundreds K

OC-192 | 10 Gbps | Limited availability | hundreds K

OC-255 | 13 Gbps | Limited availability | hundreds K

Cable

internet links provided by television cable firms
- connected to internet server
- at residence, split into TV set and computer via a bridge called a cable modem
- shared by all subscribers connected to the node
- communication speeds may slow during peak times and as more subscribers join the service

Digital Subscriber Line (DSL)

data remains digital through entire transmission
- uses telephone lines connected to DSL bridge
- transmission bit rates
- closely related to distance from telephone company's central office

T1 and T3 Lines

point-to-point dedicated digital circuits provided by telephone companies
- expensive
- used by universities and large companies for backbone and internet connections

T1 Lines

made up of 24 channels of 64 Kbps each

T3 Lines

made up of 67 channels of 64 Kbps each

Broadband over Power Lines (BPL)

uses electric power lines to carry digital signals
- utility companies partner with telecommunications to provide the service

Fiber to the Home (FTTH)

optical fiber reaches the subscriber's living or work space and reach up to 100 Mbps
- subscribers connect computers or LAN routers to an optical fiber socket

Optical Carrier (OC)

provides services through optical fiber lines
- expensive
- very high connection speeds
- provides speeds in multiples of 51.84 Mbps; speeds today reach 100 Gbps
- typically used by ISPs, providers of search engines, and content-rich or high-traffic websites

How The Internet Works

1. connect computer to router which creates a local network and a specified IP address.
2. modem connects your router to an ISP provider through a cable line, tele line, etc.
3. Your ISP requests information from the Domain Name Server (DNS)
4. The DNS uses IP (Internet Protocol) to determine what the IP address of the Web Server (where specific data, text, etc is stored)
5. Your ISP then requests information from that Web Server and their ISP sends packets of information back your ISP to send to your laptop within your local network. Your browser then combines the packets and displays the information in your browser
6. In the internet, many web servers are connected
to many local networks, and these local networks are connected to each other via ISPs.

Transfer Control Protocol (TCP)

establishes how data overall is transferred through the internet

Internet Protocol (IP)

rules around delivery to a specific address

Hyper Text Transfer Protocol (HTTP)

the protocol for transferring text from one user to another (focuses on secure text transfer)

File Transfer Protocol (FTP)

rules for transferring files

Simple Mail Transfer Protocol (SMTP)

used to send emails, used to transfer emails between servers

Voice Internet Protocol (VoIP)

rules for transferring of voice over the internet

Web 1.0 Static Web

content is created by the website owner; there are static pages with information served from the company's server

Web 2.0 Participative Web and Social Web

User generated content and participatory culture for end users; users interact and collaborate (social media, gaming, blogs, wiki, video sharing sites, etc) to enhance

Web 3.0 Semantics Web

internet data is machine readable; the web can analyze all the data on the web (and across devices) using AI and ML to create a "global brain"
- it can interact and decipher intent of search like a human (AI); a good example is a smart chatbot

Web 3 Decentralized Web

web incorporates blockchain technology and decentralized web deployment

Uniform Resource Locator (URL): “http://www.google.com”

unique address given to each web site

- “http://” is the protocol (hyper-text transfer protocol)

IP Address

a special numeric address

Domain Name

unique name for a web site, constructed with letters: “google”

Subdomain

unique name for a web site, constructed with letters: “www”

Top-Level Domain (TLD)

last part of a URL: “com”

What are websites made of?

Content, Style, Interaction

Content

the text, links, and images; is handled using HTML

Style

the appearance and layout; is defined in CSS

Interaction

how it behaves; is controlled using JavaScript

Hyper Text Mark-Up Language (HTML)

way of labeling bits of content so the web browser knows what they are.

<title>_______<title>
- <ul> - an 'unordered list' (bullet points as opposed to numbers)
- <div> - a division, or part of a page
- <button> - a tag that lets the user interact via buttons (for example: "Add to basket")
- <img> - an image that you want to display on the page

HTML5

the latest version of HTML, and includes many new features, including natively embedding video/tagging videos using <video> without having a plug-in installed
- also includes some new ways of allowing JavaScript to interact with your web page
- new capabilities are provided by a series of application programming interfaces (APIs), which can be though of as librarires of code that give additional functionality

Cascading Style Sheets (CSS)

focuses on styling the page; the HTML code just provides "text" or "content"
- is used to define font, size, color, spacing, border, and location of HTML information on a web page, and can also be used to create a continuous look throughout multiple pages of a website
- modern webpages are designed to be 'responsive,' meaning that the layout of the page changes depending on the device that is being used to view it

JavaScript

a cross-platform, object-oriented scripting language; provides programmatic control of objects
- allows users to interact with data on a web page (such as submitting data, searching for information, playing videos, etc.)

Main Functions of Search Engines

1. crawling and building an index
2. providing a solution

Crawling and Building an Index

1. Links allow the search engines' automated robots, called "crawlers" or "spiders" to get to the billions of interconnected documents on the web (off 130 trillion pages)
2. After the engines find these pages, they extract code form them and store selected information in massive
databases, to be recalled during a search engine

Providing A Solution

returns the results of the search and ranks them based on the user's query

Mediums of Sharing & Collecting Data on the Web

Blogs

Wiki

Podcast

Instant Messaging (IM)

Cookie

Clickstream Tracking

Spyware

Blogs

contraction of “web log”; Invites surfers to post opinions and focuses on a topic or set of topics

Wiki

(from Hawaiian, meaning “quick”): web application that enables users to add to and edit the contents of web pages

Podcast

publishing sound and video on the web for download

Instant Messaging (IM)

“real-time email”

Cookie

small file that stores information about a web site visitor, stored on the visitor’s computer

Clickstream Tracking

tracks a surfer’s clicking activities