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
