Chapter 1

TCP/IP

-Transmission Control Protocol/Internet Protocol, a protocol suite that governs how packets of data are transferred over the internet from one machine to another

HTML

-a textual language for creating web pages -HTML files usually saved with .html or .htm file extension -starts with an indication of the document type, then a head part with the page title and other page info, and finally a body part with the actual page content

cascading style sheets (CSS)

-a textual language for describing how a web page is styled for visual presentation, controls the look and layout of web page content -code : <style> h1 { color green; background-color: lightgray; } p{ font-family: arial; margin-left: 10px; } </style>

ETags

-aid in caching bed resources used by web browsers

WWW (the web) info...

-in the early 1990s -Tim Berners-Lee: CERN -more convenient way for computers to communicate files over the internet

the web involved what three things?

-text files, html = links to other text files -browser (program), for viewing html files -rules, HTTP protocol for transferring HTML files among computers

(SLD) second-level domain

-wikipedia.org (wikipedia), commonly an organizations name or indicates the purpose of a website

HTTP request and response are both made up of 4 parts..

1)Status line 2)Zero or more header fields 3)Empty line 4)Optional messagebody

root servers

13 main DNS servers, a computers operating system or an ISP keeps a reference to the root servers' IP addresses

when did computer networks evolve?

1960s

when did the internet begin and what as

1969, as four networked computers

entity tag

ETag -an identifier for a specific version of a web resource -when a web browser requests a cached resource, the browser sends the ETag request with an If-None-Match header, the web server will reply with a 304 Not Modified response status if the resource has not changed or a 200 OK with the changed resource and a new ETag

what was the early way for transferring files over the internet?

FTP file transfer protocol

whats used to create a web page

HTNL, CSS, JavaScript

HTML

HyperText markup language, standard markup language for web documents

IP address

Internet Protocol, a computers address on the internet. -32 bits, divided into four 8-bit groups, each often written as a decimal number

URL

Uniform Resource Locator, the location of a web resource on the web -domain names are most commonly seen in URLs

request method

a HTTP request method indicates the desired action to preform on a resource

browser cache

a area on the computers disk where web content can be stored by the web browser for quick retrieval later, can reduce network traffic required to display previously visited web pages(instead of re-downloading the web page),

website

a collection of related web pages get organized into a website

web server

a computer that serves web pages to web browsers, websites get stored on them

webpage

a document that is viewed in a web browser

an HTTP request is....

a message sent from the web browser to the web server, often the request asks the server to send back a web resource

an HTTP response is...

a message sent from the web server back to the web browser in response to an HTTP request, often the response contains the requested web resource

domain name

a name for an IP address

HyperText Transfer Protocol

a networking protocol that runs over TCP/IP and governs communications between web browsers and web servers

web browser

a program that downloads an HTML document from a server, displays the document to the user with the appropriate formatting, allows the user to interact with the document

JavaScript

a programming language that runs in a browser, enabling web pages supporting actions like responding to a button clink, JavaScript can be included in the HTML file's header part

HTTPS

a protocol that encrypts HTTP traffic between a browser and web server so a network sniffer cannot intercept sensitive info in the HTTP traffic like passwords

URL shortening

a technique to create shorter URLs the redirect to longer URLs, convent for sharing on social media

link

a web page is a clickable item that causes the web browser to jump to another web page when clicked, a button or image can also have a link

digital certificate

a website wanting to use HTTPS must acquire a digital certificate issued by a trusted certificate authority, which contains a public key needed to encrypt data between the browser and web server

status code

an HTTP response status code is a 3 digit number that indicates the status of the requested resource

web resource

any retrievable item like a HTMLfile

how does HTTP function

as a request-response protocol between web browsers and web servers

CSS color

can be a pre-defined name as in color: blue, or an rgb value as in color:rgb(50,100,255) 0 = none 155 = bright

markup

document markup is special markings in the document that provide additional info. about links, formatting, and images

(ccTLD) country code top-level domain

each country is assigned a unique two-letter ccTLD like .uk

a JavaScript function

is a named group of statements that can be run by referring to that name

the Web

just one particular use of the internet

(TLD) third-level domain, and further

refer to sub-computer systems local to an organization -cs.stanford.edu (cs) -common = www

GET

request a representation of the specified resource.. web server returns the requested resource with a 200 status code

HEAD

request a response identical to GET but without the response body, used by web services that allow new resources to be created, modified, and deleted on the web server

PUT

request the web server accept the message body enclosed in the request as a modification of an existing resource, used by web services that allow new resources to be created, modified, and deleted on the web server

POST

request the web server accept the message body enclosed in the request as a new resource, used by web services that allow new resources to be created, modified, and deleted on the web server

DELETE

request the web server delete the existing resource

a URL is composed of what

scheme- characters at the beginning of a URL followed by : or :// (http)://.......... Hostname- the complete domain name specified in the URL http://www.cdc.gov Path- all characters to the right of the hostname in the URL

CSS rule

selects specific HTML elements and specifies styling properties for that element, styling can occur within style tags in the HTML file's header part, each style rule indicates the element to be styled like h1(header1) or p(paragraph), followed by a list of braces{} of property: value items like color: blue

network sniffer

software that monitors network network traffic and allows users to inspect HTTP requests and responses

JavaScript variable

stores a value or a link to an element of a web page, using the link allows JavaScript to directly modify the properties of an element defined elsewhere in the HTML document

Hypertext

text that has links to other text, images, videos...

web accessibility

the ability of users with disabilities to access and use web pages with reasonable effort, insures equal access and opportunity for everyone

separation of concerns

the design principle of breaking up web content using distinct languages and documents that overlap as little as possible -in modern webpage design, document structure and text, visual layout, and page interaction are separately specified using three key languages 1)HTML: the language that describes the page content 2)CSS: the language that describes page layout 3)JavaScript: the language that provides interactive funtionality

JavaScript describes...

the dynamic behaviors and actions of a web page

Linkrot

the general name for once valid links that now return 404 status codes

Internet of Things (IoT)

the global collection of communicating devices that sense and control technology on behalf of humans -display one or more of the characteristics: gather info about the physical world using sensors, share the sensor data with control systems, interact with hardware to execute commands sent by control systems

internet

the interconnection of computers communication using a set of rules

CSS (Cascading Style Sheets) specifies...

the layout and visible appearance

ICANN

the organization that manages TLDs, now allows companies and organizations to create customized TLDs

IPv4

the original internet protocol, 32-bit addresses

HTML defines...

the structure and content of a web page

cognitive computing

the use of artificial intelligence techniques and access to vast amounts of data to simulate human problem solving in complex situations with ambiguity, changing data, and even conflicting info

before HTTP communications begin...

the web browser extracts the domain name from the URL and does a DNS lookup by sending the domain name to the local DNS and getting back the IP address of the web server hosting the domain name. the browser uses the IP address to establish a TCP connection with the web server and begins communication with the HTTP

W3C

the world wide web consortium, the international standards organization. with the standards, browsers now compete on browser speed, standard compliance, and browser features

why does a web browser use HTML

to understand the structure and semantics or meaning of the document

domain names belong to...

top-level domain (TLD), .com .net

IPv6

uses 128-bit addresses

DNS server (Domain Name System)

when a computer sends a packet using a domain name over the internet the first step is to contact a DNS server to convert the domain name to an IP address

browser redirect

when the web server returns a 301 or 302 status code with a Location header indicating the URL the browser should load next