Course Overview Internet Technology

Course Objectives Develop an understanding of how web pages work. Become familiar with SSH, SFTP, HTML, CSS/JavaScript. Gain hands-on experience in web authoring. Construct a website Internet Technology

Course Requirements Grading Prerequisites Homework Assignments (40%) Midterm Project (20%) Final Projects (40%) Participation (Extra Credit) Prerequisites Basic computer skills (e.g., know how to use PC and Web browser) Technical background is not required. Internet Technology

Course Policy Students are encouraged to work together in all aspects of the course (e.g., homework and group projects) except for the final exam. This class advocates an open book policy of allowing students to consult textbooks, Internet resources, and classmates when working on assignments to facilitate learning and promote collaboration. Internet Technology

Course Resources Homepage Required Readings Supplemental Readings http://widit.knu.ac.kr/~kiyang/teaching/IT/ Required Readings Lecture material and online contents Supplemental Readings Creating Web Pages for Dummies (9th Edition, 2008)  by Bud E Smith, November The Wiley Publishing The Internet for Dummies (13th Edition, November 2011) by John R. Levine, Margaret Levine Young The Wiley Publishing Internet Technology

Internet Overview Internet Technology

6/12/2018 What is the Internet? An internet is a set of computer networks that are connected to each other (e.g. intranet). The Internet is a world-wide set of networks that interoperate using TCP/IP protocols. Think of “communication software” or “standards” when you see “protocol” more on TCP/IP and other protocols later… A global channel for digital communication and data exchange. Internet Technology

What is the Internet? An internet 6/12/2018 What is the Internet? An internet Local Area Network “kiyang.kmu.ac.kr” 203.247.29.10 “www.whitehouse.gov” 96.16.242.135 Internet Technology

How does the Internet work? What happens between Point A and Point B? 6/12/2018 How does the Internet work? What happens between Point A and Point B? Point A Point B Internet Technology

How does the Internet work? Postal Analogy Common language e.g., Korean, English A letter An envelope stamped & addressed Physical delivery via the postal stream Internet Application protocols HTML, SMTP, SSH, SFTP Digitized data Communication protocols TCP/IP Connection to the Internet NIC, wire/wireless, routers Internet Technology

Networking Basics: Main considerations for the Internet 6/12/2018 Networking Basics: Main considerations for the Internet Need homogeneous communications between heterogeneous hardware and software. Communication Protocols Transmission Control Protocol / Internet Protocol Addressing System Domain Name System (Service) Layered Networking Structure Need efficient method of data exchange for a distributed and decentralized system Client-Server model Layered structure makes it easier for hetero to homo Maximize trade-offs between speed and distance. Internet Technology

Networking Basics: Circuit and Packet Switching Circuit Switched Communication Dedicated Line Packet Switched Communication Receiver Sender Data broken up into packets Internet Technology

Communication Protocol 6/12/2018 Communication Protocol TCP (Transmission Control Protocol) Responsible for ensuring reliable & accurate delivery of data e.g., error-checking, end-to-end acknowledgement, etc. Breaks up a file to transmit into a set of TCP “segments”. TCP header contains sequence #, ACK, checksum IP (Internet Protocol) Method for Routing Data Defines how packets reach specified destination Best-effort delivery (i.e. connectionless, unreliable) data corruption, lost packets can occur Encapsulates a TCP segment in an IP packet IP header contains the destination IP address Internet Technology

Internet Protocols Application Layer Protocols 6/12/2018 Internet Protocols Application Layer Protocols Application layer protocols ensure that the sender and receiver are speaking the same language, and that the letter can be interpreted HTTP, FTP, SMTP , Telnet, SSH HyperText Transfer Protocol File Transfer Protocol Simple Mail Transfer Protocol Telnet Protocol Transmission Control Protocol Internet Protocol LAN IP Packet Internet Technology

Networking Basics: Four Layer Model 6/12/2018 Networking Basics: Four Layer Model Applications Applications Interface e.g., HTTP, SMTP, SSH Transport Reliable Delivery i.e., TCP Network Source to Destination i.e., IP Physical Hosts, routers, wires, etc. Internet Technology 15

How does the Internet work? Communication on the Internet 6/12/2018 How does the Internet work? Communication on the Internet Application (e.g. Firefox) Application (e.g. Web server) Data Data Network Interface (i.e. TCP/IP) Network Interface (i.e. TCP/IP) Is TCP/IP driver right for NI? You can see there are layers of things going on and several pieces that all work together. We will talk about later why data gets chopped up. Packet Packet Packet Packet Packet Packet Physical (wire, router, hosts) Internet Technology

Internet Addressing IP address Hostname Domain name 6/12/2018 Internet Addressing IP address a unique number assigned to a host assigned by IANA e.g. 155.230.194.245 Hostname a unique name assigned to a host named by organizations e.g. widit.knu.ac.kr Domain name a name assigned to an entity. e.g. knu.ac.kr Internet Technology

Internet Addressing: Domain Name System (DNS) 6/12/2018 Internet Addressing: Domain Name System (DNS) Hostname to IP Address mapping system DNS servers store the name/address pair. Applications use resolvers query DNS servers. Main Characteristics Hierarchical Sub-domains on the left (e.g. lis.knu.ac.kr) Distributed Authoritative name servers for each domain & sub-domains When a DNS server is missing an entry, next server is checked A client (resolver) must know at least 1 DNS server The domain name system (DNS) is the way that Internet domain names are located and translated into IP (Internet Protocol) addresses. A domain name is a meaningful and easy-to-remember "handle" for an Internet address. Because maintaining a central list of domain name/IP address correspondences would be impractical, the lists of domain names and IP addresses are distributed throughout the Internet in a hierarchy of authority. There is probably a DNS server within close geographic proximity to your access provider that maps the domain names in your Internet requests or forwards them to other servers in the Internet. Originally included com, gov, edu, org, net Also country codes (doled out by IANA) Ca canada Au australia Ch switzerland New domain names governance in place Internet Technology

Internet Addressing: DNS is Hierarchical 6/12/2018 Internet Addressing: DNS is Hierarchical .edu ncsu.edu unc.edu duke.edu cs.unc.edu med.unc.edu ils.unc.edu Internet Technology

Internet Addressing Hostname vs. IP Address Most Least Least Most 6/12/2018 Internet Addressing Hostname vs. IP Address widit.knu.ac.kr Top Level Domain Specificity Most Least 155.230.194.245 IANA assigned Assigned locally Specificity Least Most Internet Technology

Internet Addressing: Anatomy of a URL 6/12/2018 Internet Addressing: Anatomy of a URL URL stands for Universal Resource Locator sometimes seen as Uniform Resource Locator Protocol Hostname Domain Item requested http:// widit. knu.ac.kr /~kiyang/teaching/IT/s13/schedule.htm Fully qualified resource name Certain protocols assume certain ports (e.g., http → port 80) When non-standard port is use, it can be specified in the URL - e.g., http://widit.knu.ac.kr:8800/ Internet Technology

Client-Server Model Client Server 6/12/2018 Client-Server Model Client Initiates a Connection Server Waits & Responds to Incoming Connections 155.230.194.233 155.230.194.245 Application Protocol (HTTP) Client Application Server Application program running on client machine (e.g., Internet Explorer) program running on server machine (e.g., Apache Web Server) Internet Technology

Client-Server Model: Overview 6/12/2018 Client-Server Model: Overview Servers Can be hardware (computers) or software (programs) One computer can run many server applications. e.g., http (web), ftp, email, telnet, etc. Server Address = IP address + port number Each server application listens on a different port e.g., http → 80, SMTP → 25, telnet → 23, ssh → 22, ftp → 21 Clients There can be many clients for a given application People interface with them directly HTTP Clients: Internet Explorer, Firefox, Chrome Email Clients: Outlook, Pine, Lotus Notes Telnet/SSH Clients: Putty, SSH Secure Shell Internet Technology