Introduction to the Internet/WWW

Introduction to the Internet/WWW

Internet Resources Discovery (IRD) Introduction to the Internet/WWW 1 T.Sharon-A.Frank Introduction to the Internet Internet Resources/Services What is the Internet Standards/Protocols 2 T.Sharon-A.Frank Internet Resources/Services

3 Electronic Mail (E-Mail) News (Usenet) File Transfer (FTP) Remote Login (Telnet) Information Browsing (Gopher) Automated Title Search (Archie, Veronica) Automatic Content Search (WAIS) Advanced Browsing (WWW) T.Sharon-A.Frank Internet Resources Discovery (IRD)

Resources discovery - locating unfamiliar resources. Resources can be documents, files, users and services, both textual and multimedia. IRD is resource discovery on the internet and in the Web. 4 T.Sharon-A.Frank ?What is the Internet 5

Internet is a Multi-Network Architecture Internet = Interconnected Network Internet is based on TCP/IP Protocol Set IP = Internet Protocol TCP = Transmission Control Protocol Based on former ARPANET by DOD T.Sharon-A.Frank Whats the Internet: nuts and bolts view millions of connected computing devices: hosts, end-systems pcs workstations, servers PDAs phones, toasters router server regional ISP

fiber, copper, radio, satellite routers: forward packets (chunks) of data thru network 6 mobile local ISP running network apps communication links T.Sharon-A.Frank workstation company network

Internet Infrastructure LAN Corporate Network Router WAN LAN Campus Ethernet Regional and National Providers (ISP) Router Router

Router Router 7 T.Sharon-A.Frank Interconnected Network Private Dedicated Public Circuit Switched Router Local Area ISDN Bridge

Router Metropolitan Area Local Area Gateway Gateway Public Packet Switched Who Runs the Internet? nobody

Standards:Internet Engineering Task Force (later) Numbers: IANA (Internet Assigned Numbers Authority) Names: Internic (US), RIPE (Europe), Network: ISPs (Internet Service Providers), NAPs (Network Access Points), Fibers: telephone companies (mostly) Content: thousands of companies, universities, individuals, 9 T.Sharon-A.Frank ?Whats a protocol human protocols: whats the time? I have a question introductions network protocols:

machines rather than humans all communication activity in Internet governed by protocols specific messages sent protocols define format, order of messages sent and specific actions taken when messages received,received among network entities, and actions taken on message or other events transmission, receipt 10 T.Sharon-A.Frank ?Whats a protocol

a human protocol and a computer network protocol: Hi TCP connection req. Hi TCP connection reply. Got the time? Get http://gaia.cs.umass.edu/index.htm 2:00 time

? Q: Other human protocol 11 T.Sharon-A.Frank TCP/IP TCP breaks the message data into pieces Data IP Packet 12 T.Sharon-A.Frank TCP/IP TCP takes a long message and breaks it up: Each piece has a sequence number. Each piece is sent using IP:

Destination has enough info to reassemble message. Will request missing piece until all is there. TCP IP 13 TCP Internet T.Sharon-A.Frank IP IP Packet Packet Data From: 192.112.36.5 To: 128.174.5.6 IP Address

14 Packet Envelope T.Sharon-A.Frank IP Properties IP will get it there, but Network Delay is Variable Message might be lost, or sent out of order. Message cant be too long (about 1K max). For email, web, want reliable transfer of big files. Still doesnt say for which process a packet is intended: Message come to a machine, but are handled by a process.

Like a house with many people in it. Solution is TCP. 15 T.Sharon-A.Frank Protocols in the TCP/IP Model Protocols Application Transport TELNET FTP TCP IP ARPANET

SATNET Networks 16 DNS UDP Network Physical+ data link SMTP T.Sharon-A.Frank Packet radio

LAN Internet/WWW Standards Internet Domain Name System (DNS) WWW Uniform Resource Locator (URL) Hypertext Markup Language (HTML) Hypertext Transfer Protocol (HTTP) 17 T.Sharon-A.Frank Domain Name Service (DNS) cs.biu.ac.il

18 www.netscape.com www.cmu.edu Map Domain Name to IP Address Domain Names must be Unique Domain Names have many Parts Suffix of Domain Names Significant T.Sharon-A.Frank Domain Names cs.biu.ac.il il

ac tau biu cs 19 T.Sharon-A.Frank DNS - Domain Name Lookup Search in cache Search in local repository If the name is in the same domain If the name was retrieved lately Ask other servers

20 T.Sharon-A.Frank DNS - Domain Name Lookup Users computer in Israel Domain name server in Israel Users computer in USA Name IP Address 21

Internet T.Sharon-A.Frank DNS - Domain Name Lookup Users computer in Israel Domain name server in Israel Name Domain name server in USA Name IP Address

IP Address 22 Internet T.Sharon-A.Frank Users computer in USA Uniform Resource Locator (URL) URL is an address of a Web page in the Internet. Protocol://domain-name:port/directory/file-name

Protocol: http, ftp, gopher... Domain-Name (or IP-address) Port (for security purposes) Directory File-Name Example: http://www.cs.biu.ac.il:8080/~taly/mm/index.html 23 T.Sharon-A.Frank

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