Introduction to Internet

Contents What is Internet Some key concepts Internet history, Internet Services World Wide Web, types of web sites Internet and Libraries Example applications at NCSI, IISc Internet Resources: Examples

What is Internet? Interconnection of computers and computer networks using TCP/IP communication protocol Transport Control Protocol/ Internet Protocol (TCP/IP) What is a protocol? – A protocol is a set of rules defining communication between systems

What is Internet? Intranet: Use of TCP/IP to connect computers on an organizational LAN Internet: Use of TCP/IP to interconnect such networks TCP/IP is the basic Internet protocol Various application protocols operate over TCP/IP – SMTP ( ), HTTP (Web), IRC (Chat), FTP (File transfer), etc.

Internet consists of many different types of networks – Ethernet – Token ring Different types of operating systems and other software How do they work together? – Standards

Divide Work into Layers b a physically encode bits on “wire” physically encode bits on “wire” connect segments, address (locating points on graph) and route (navigating graph) connect segments, address (locating points on graph) and route (navigating graph) make network simple and reliable make network simple and reliable

Sending Data Along Wires Connection-oriented – Circuit switched Persistent connection set up between sender and receiver – Example: telephone system Connectionless – Packet switched Data partitioned into packets and sent individually from sender to receiver Reassembled at receiver

TCP/IP Rules for information exchange between computers over a network ‘Packet’ based – segment/ de-segment information Client-Server (Request/ Response) – Web browser (client), Website (Server) TCP – Handles data part IP – Handles address part – Identification of every computer on the Internet – IP address

Internet – Some Key Concepts Backbone network Client/ Server IP Address Host name/ Domain name – URL: Uniform Resource Locator – Address for identifying a resource on a host with a specific protocol – access protocol://host.domain [:port]/path/file name (Ex.:

Comparison of Switching Technologies Circuit switched Advantages – Only route once – Latency and bandwidth constant Disadvantages – Idle resources unavailable for other connections – Large setup time – Single point of failure Distributed state Packet switched Advantages – Efficient use of wires – Small startup overhead Disadvantages – Route each packet – Per packet overhead

Ethernet Bob Metcalfe at Xerox PARC Used for local area networks (LANs) – Physically near one another – 200 computers within 100 meters Broadcast medium – Single wire connects all computers Each computer has unique 48-bit MAC address – All computers constantly listen “Carrier Sense, Multiple Access with Collision Detect” – Sender waits until wire unused before sending – If hears collision, stops, waits random time, retransmits

Ethernet

Ethernet Variations

Ethernet Properties Shared Distributed (not Centralized) Insecure Unpredictable Latency & Bandwidth

Alternative to Ethernet: Token Ring Alternative introduced by IBM (1980s) “Passing the Conch Shell”

Applications of the Internet Traditional core applications: News Remote Login File Transfer The killer application: World-Wide Web (WWW) New applications: Videoconferencing Telephony P2P applications Internet Broadcast

Time Line of the Internet

Growth of the Internet

Internet Infrastructure

The infrastructure of the Internet consists of a federation of connected networks that are each independently managed (“autonomous system”) – Note: Each “autonomous system may consist of multiple IP networks – Autonomous systems have a number (AS number) Hierarchy of network service providers (NSPs) – Tier-1: nation or worldwide network (US: less than 20) – Tier-2: regional networks (in US: less than 100) – Tier-3: local Internet service provider (in US: several thousand)

Internet Infrastructure Location where a network (ISP, corporate network, or regional network) gets access to the Internet is called a Point-of-Presence (POP). Locations (Tier-1 or Tier-2) networks are connected for the purpose of exchanging traffic are called peering points. – Public peering: Traffic is swapped in a specific location, called Internet exchange points (IXPs) – Private peering: Two networks establish a direct link to each other.

Topology of a Tier-1 NSP

Organization of a single node in a Tier-1 network

Who is Who on the Internet ? Internet Society (ISOC): Founded in 1992, an international nonprofit professional organization that provides administrative support for the Internet. Founded in 1992, ISOC is the organizational home for the standardization bodies of the Internet. Internet Engineering Task Force (IETF): Forum that coordinates the development of new protocols and standards. Organized into working groups that are each devoted to a specific topic or protocol. Working groups document their work in reports, called Request For Comments (RFCs). IRTF (Internet Research Task Force): The Internet Research Task Force is a composed of a number of focused, long-term and small Research Groups. Internet Architecture Board (IAB): a technical advisory group of the Internet Society, provides oversight of the architecture for the protocols and the standardization process The Internet Engineering Steering Group (IESG): The IESG is responsible for technical management of IETF activities and the Internet standards process. Standards. Composed of the Area Directors of the IETF working groups.

Internet Services – One-to-one – One-to-many (e.g. discussion forums) Telnet – remote login (e.g. library catalogue access) FTP: File transfer (e.g. software packages) Web (HTTP): Hypertext linking/navigation IRC: Internet Relay Chat Internet telephony, mobile access, etc.

IISc World Wide Web (WWW) “Killer Application” Hypertext linking of multi-media documents “Point and Click” Lingua-franca of Web: HTML Websites: Host multimedia documents, linked using HTML (web pages) Web browsers: Access websites, “browse” Medium for Publishing, distributing, and accessing information UNIQUE!

Growth of the Web Web is the totality of web pages stored on web servers Spectacular growth in web-based information sources and services: – Education and research – Entertainment – Business and commerce – Personal home pages Estimated to contain several billion documents Doubling each year Over a billion web sites Almost every telephone owner – Internet user

Types of Websites Shopping sites – (book store) – (gardening) – (book store) – (clothes, etc.) Community sites – (American Chemical Society) – – (Bangalore) – (stock traders

Types of Websites Entertainment sites – disney.go.com (Walt Disney) – – – Identity sites – – –

Types of Websites Learning sites – (web-based training in IT) – (Internet training) – Information sites – – (Encyclopaedia Britannica) – –

Finding Information on Web Search Engines – General – Meta search engines – Domain specific Directories – General (e.g. Yahoo) – Subject/Resource specific gateways (e.g. EEVL)

Internet & Libraries Provide access to Internet resources – Gateway services Electronic publishing and provision of L&I services over intranet/ Internet – OPAC, Portals, Digital Libraries Library administration and management – Acquisition, Technical processing, etc. Professional self-learning