Internet.pdf

The Internet and the World Wide Web Difference between the Internet and WWW Internet – Massive network connecting a huge number of computers – Infrastructure for WWW, e-mail, instant messaging etc. – Many protocols World Wide Web (OR web) - Inside Internet...

The Internet and the World Wide Web Difference between the Internet and WWW Internet – Massive network connecting a huge number of computers – Infrastructure for WWW, e-mail, instant messaging etc. – Many protocols World Wide Web (OR web) - Inside Internet – Model for information sharing, built over the internet – Uses http(s) protocol – Uses browsers to access web pages linked through hyperlinks – Is a portion of the Internet Other portions can be email (using SMTP), file transfer (using FTP),... Types of Internet Connections Dial-up (over the telephone line (already existing), cannot use phone when online): Modem - Call ISP - Not use the phone when online - Slowest kind of connection - 50 KBPS (kilo beat per second) ISDN (Integrated Services Digital Network) (over the telephone line) - Faster than Dial Up - Upgrade from Dial-up DSL (Digital Subscriber Line) - Most Common - Telephone line – “always on” connection – Uses the telephone network, digital technology – ADSL, SDSL, HDSL, VDSL - Split line of copper wire, (different info simultaneously such as audio information and data) Cable (coaxial cable used by cable tv) – Shared bandwidth WIRELESS – Wi-Fi, WiMax etc. – Satellite (anywhere) An Internet connection is provided by an ISP (Internet Service Provider) Protocols - Rules of communication, steps when exchanging information - Clearly defined form - Deal with data compression, error checking - - Hierarchy - - Ethernet: physical component that connects computers to networks - OSI Model has 7 layers TCP/IP - 2 protocols that work together IP address - Locating computers - A lot of comp connected to the internet - A number that uniquely identifies a computer on a network (i.e. computer’s address) - All devices connected via the TCP/IP have their unique global number IPv4 uses a 32-bit address system (4 bytes) → about 4.3 billion addresses (4 x 10^9) - (232 = 4,294,967,296) - 2^10 - 1K : 1 billion Expressed in decimal numbers by separating every byte with “.” to four parts (Example: 130.158.65.1) → Binary 1000 0010 1001 1110 0100 0001 0000 0001 Address exhaustion (New IP address ) → IPv6 - uses a 128-bit address space (2^128, i.e. 3.4 x 10^38 addresses!) - 3 x 10^38 DNS ( Domain Name System) - Each comp has IP address - Doman name(www.google.com) is easier to remember - Stores all internet domain names and their IP addresses Domain Names - Domain: hierarchical space of names to facilitatethe identification of units of network management Root domain: The dot Top Level Domain Large group of comp in the internet Second Level Domain Specify even more Subdomain By specifying a subdomain to each unit of organization, networks can be managed independently (in uni, each school has diff subdomain) Host name Routers and IP addresses - To reach a comp, need to go through multiple routers - Routers are connected to each other - Do it fastest way. TCP( transmission control protocol) - IP knows how to locate comp - TCP knows hot to exchange data - Reliable when it comes to sharing information (built in error recovery) Retransmission - If file transmitted is corrupted or not found, it will ask to send the corrupted/ not found packets again. (optimize transmission) Acknowledgement - Packet 8,12…. Received. To the computer that sent the file. - A is sure B received all the data - Ensures Architecture Client-Server architecture - Computing model - Server hosts, delivers and manages resources to be consumed by the client - One or more client connected to the server. The system shares computing resources - A client makes a request to the server, the server provides the requested data - mini computer (each client is a terminal) , This architecture (each client is a computer) P2P (peer to peer) - Decentalized, no center - The computer both server and client at the same time - Most famous P2P protocol: BitTorrent Browser - Software used for browsing webpages - Requests webpage from a website - Accessed through www through http by using a URL - Ex: Firefox, Opera, Chrome, Safari, Edge, Brave… Web Server - Software (installed on a server) - Delivers web pages requested from browser URL (Uniform Resource Locator) - Address of webpages - Consists of domain name, location(path of the server) - Sending HTTP requests - Browser sends GET request followed by the page, Sent to the server  - Send the page back to the computer - HTML: Markup language for web pages - Hypertext: hyperlink to other text Webpage - Web Browser: analyze and display text files that follow the HTML syntax - - Two main parts: Head, Body HTML, JavaScrpt, CSS - HTML: Markput language, layout language, not programming language - Often used with JavaScript, and CSS(Cascading style sheet) - CSS: defines the presentation of document, appearance of text Emails - OLD: When email is sent, the mail gateway(server) receives it and relays it to the next gateway. - The gateway of receiving organizatio deliver the mail. Stay there until requested by the destination mailbox. - SMTP (Simple Mail Transfer Protocol) only sending - The user reads the mail by running an email program which has the mailbox or by downloading it to a computer - POP3(Post Office Protocol ver.3): Download all the messages before being able to read - IMAP (internet Message Agent Protocol): If the header of the email is clicked: Sender and subject and information - Microsoft Exchange… Search the diff between the 3 Accessing Emails: OLD: Typical program; Thunderbird, Microsoft Outlook - Need the dedicated applications (only emails) - Can work offline (Type offline) - Accessed through a web browser(web mail): - Can be accessed from anywhere (any browser) - Cannot work offline Push mail: - Gets pushed to its destination - Do not ned to be polled to be received (instantaneously) Internet Backbone The Internet backbone is the principal data routes between large, strategically interconnected computer networks and core routers of the Internet.