Introduction to Internet Technology Overview of Web Authoring Internet Overview Introduction to Internet Technology Overview of Web Authoring Internet Technology

4/18/2018 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? google.com widit.knu.ac.kr www.whitehouse.gov 4/18/2018 What is the Internet? google.com 74.125.232.230 widit.knu.ac.kr 155.230.194.245 www.whitehouse.gov 104.118.93.61 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 HTTP, SMTP, SSH, SFTP Digitized data Communication protocols TCP/IP Connection to the Internet NIC, wire/wireless, routers Internet Technology

How does the Internet work? Key Components 4/18/2018 How does the Internet work? Key Components Need homogeneous communications between heterogeneous hardware and software. Communication Protocols Transmission Control Protocol / Internet Protocol Addressing System Domain Name System (Service) Networking Structure Four Layer Model Need efficient method of data exchange for a distributed and decentralized system Application Structure Client Server Architecture/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 Hello Who’s calling? Packet Switched Communication - Data is broken up into packets Receiver Sender A B C A B C A B C Internet Technology

Networking Structure: Four Layer Model 4/18/2018 Networking Structure: Four Layer Model Applications Interface e.g., HTTP, SMTP, SSH Applications Reliable Delivery i.e., TCP Transport Source to Destination i.e., IP Network Hosts, routers, wires, etc. Physical Internet Technology 7

Communication Protocols Transport & Network Layers 4/18/2018 Communication Protocols Transport & Network Layers 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 source/destination IP address Internet Technology

LAN Communication Protocols Applications Layer 4/18/2018 Communication Protocols Applications Layer 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

Communication on the Internet 4/18/2018 Communication on the Internet Application (e.g. Chrome) 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 4/18/2018 Internet Addressing IP address An unique number assigned to a host Assigned by IANA e.g. 155.230.194.245 Hostname A human-readable 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) 4/18/2018 Internet Addressing: Domain Name System (DNS) Hostname to IP Address mapping system DNS servers store the name-address pair. Applications use resolvers to 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 4/18/2018 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 4/18/2018 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

Fully qualified resource name 4/18/2018 Internet Addressing: Anatomy of a URL URL stands for Universal Resource Locator a.k.a. Uniform Resource Locator Certain protocols assume certain ports (e.g., http → port 80) When non-standard port is use, it can be specified in the URL http://widit.knu.ac.kr:8800/ Protocol Hostname Domain Item requested http:// widit. knu.ac.kr /~kiyang/teaching/IT/s16/schedule.htm Fully qualified resource name Internet Technology

Client-Server Model Client Server 4/18/2018 Client-Server Model Client Initiates a Connection Server Waits & Responds to Incoming Connections 155.230.194.233 155.230.194.245 Application Protocol (e.g., HTTP) Client Application Server Application program running on the client machine (e.g., Internet Explorer) program running on the server machine (e.g., Apache Web Server) Internet Technology

Client-Server Model: Overview 4/18/2018 Client-Server Model: Overview Servers Can refer to 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 server 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 http server SMTP server SSH server http client SMTP client http client http client SMTP client SSH client Internet Technology

Web Authoring Internet Technology

Publishing HTML Content Creation Mode #1 Content Creation Mode #2 Edit 4/18/2018 Publishing HTML Content Creation Mode #1 Create HTML pages on the local PC using Notepad, Dreamweaver, etc. Upload the files to the server to be displayed on the Web Content Creation Mode #2 Create HTML pages directly on the server using pico, vi, etc. Edit Edit Publish Display Display upload Publish Internet Tecnology

Q&A What is the Internet? How does it work? Describe Domain Name System Client-Server Model 4-Layer Model TCP/IP How can you publish content on the Web? Internet Technology

An Opte Project visualization of routing paths through a portion of the Internet Internet Technology

Internet Technology