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Jen Golbeck College of Information Studies University of Maryland
The Internet and HTML Jen Golbeck College of Information Studies University of Maryland
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A Short History of the Internet
1969: Origins in government research Advanced Research Projects Agency (ARPAnet) 1983: Design adopted by other agencies Expansion from educational institutions to corporations 1991: World Wide Web added point-and-click capabilities
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The Internet Global collection of public networks
Private networks are often called “intranets” Each organization maintains its own network Use of shared protocols TCP/IP (Transmission Control Protocol/Internet Protocol): basis for communication DNS (Domain Name Service): basis for naming hosts HTTP (HyperText Transfer Protocol): World Wide Web
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Packet Routing (TCP/IP)
(Much simplified) Routing table for Destination Next Hop 52.55.*.* 18.1.*.* / 4.*.*.* …
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Addresses and Domain Names
Every computer has an IP address E.g Hard to remember, and hard wired Domain names are short cuts to IP addresses umd.edu, facebook.com, etc
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Domain Name Service (DNS)
“Domain names” improve usability Easier to remember than numeric IP addresses DNS coverts between names and numbers Written like a postal address: specific-to-general Each name server knows one level of names “Top level” name server knows .edu, .com, .mil, … .edu name server knows umd, umbc, stanford, … .umd.edu name server knows wam, glue, ttclass, … .wam.umd.edu name server knows rac1, rac2, …
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Domain Names Unsponsored Sponsored Infrastructure: .arpa .root
.biz .com .edu .gov .info .int .mil .name .net .org Sponsored .aero .asia .cat .coop .jobs .mobi .museum .pro .tel .travel Infrastructure: .arpa .root Proposed .berlin .bzh .cym .gal .geo .kid .kids .lat .mail .nyc .post .sco .web .xxx Deleted/retired: .nato Reserved .example .invalid .localhost .test
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If you want one… You need a web host
Company to host your web pages Alternatively, you can do it yourself, but it requires a lot of infrastructure (and permissions) you don’t have Cost ranges from $5/month (e.g. ) and up depending on services You register for a domain name and point it to the host Cost is about $35/year (less if you buy for multiple years)
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The Web Not the same thing as the Internet 1991 - now
Internet is the network of computers that sends information around ( , web pages, chat, skype, file transfers, etc) The web is a layer on top of the internet that sends files in a certain way (using HTTP) now
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Foundations of the Web TCP/IP DNS HTTP
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Standards No one owns the web or the internet
Platform and software independent - it should work the same everywhere W3C - World Wide Web Consortium A group of people (universities, businesses, governments, etc) who decide by committee what the web will be and how it changes Some people modify standards BAD! E.g. a web page that only works in Internet Explorer
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HTML and XHTML HTML based on meta-language SGML XHTML is based on XML
SGML has lots of freedom, but that makes it harder to parse XHTML is based on XML Almost identical to HTML, except for a few stricter rules There are billions of web pages that are valid HTML but not valid XHTML - Thus, HTML will keep being supported pretty much forever
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Why Code HTML by Hand? The only way to learn is by doing
WSIWYG editors… Often generate unreadable code Ties you down to that particular editor Cannot help you connect to backend databases Hand coding HTML allows you to have finer-grained control HTML is demonstrative of other important concepts: Structured documents Metadata
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Today’s Tutorial Your first HTML page
Uploading your page to the Web server via FTP
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HTML Basics Tags End Tags
<body> <b> <table> End Tags </body> </b> </table> Tag names are not case sensitive in HTML, are case sensitive and all lower case in XHTML
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HTML Basics II Every tag has an end tag (with a few exceptions)
In HTML, some tags don’t have an end tag E.g. the tag for putting an image on the page <img> or adding a line break <br> In XHTML, all tags need end tags. However, in some cases it doesn’t make sense Short hand for starting and ending a tag all at once <br /> Note there is a space and then a slash at the end
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HTML Basics III Attributes Structure Add features to a tag
<body bgcolor=“red”> Structure Attribute name = attribute value E.g. bgolor=red Values must be in quotes in XHTML Quotes are optional in HTML unless there is a space in the value. Then quotes are required Single or double quotes are fine
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HTML Basics IV Learning HTML is basically just learning all the tag names and attributes Becoming a web designer takes a lot more than that Practice Practice Practice
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“Hello World” HTML <html> <head>
This is the header <html> <head> <title>Hello World!</title> </head> <body> <p>Hello world! This is my first webpage!</p> </body> </html> This is the actual content of the HTML document
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Uploading Your Page Connect to “terpconnect.umd.edu”
Go up one level in the directories Change directory to “pub” Upload files We will do this in detail in the next session
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Tips Edit files on your own machine, upload when you’re happy
Save early, save often, just save! Reload browser
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A little bonus on the history of the internet…
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How did the Internet come to be?
It started as a research project to experiment with connecting computers together with packet switched networks. It was developed with funding and leadership of the Defense Department’s Advanced Research Projects Agency (ARPA).
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Who invented the Internet?
Leonard Kleinrock who did early work in packet switching Vint Cerf and Robert Kahn who defined the "Internet Protocol" (IP) and participated in the development of TCP Of course always much more complicated that 1 slide – how did it start and who invented it….
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: Connect Computers? 1958 – After USSR launches Sputnik, first artificial earth satellite, US forms the Advanced Research Projects Agency (ARPA), the following year, within the Department of Defense (DoD) to establish US lead in science and technology applicable to the military 1961 – First published work on packet switching (“Information Flow in Large Communication Nets”, Leonard Kleinrock, MIT graduate student) 1964 – other independent work in packet switching at RAND Institute and National Physics Laboratory in England
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1966 –1968: Connect Computers? Funded
1966 – Lawrence Roberts (colleague of Kleinrock from MIT) publishes overall plan for an ARPAnet, a proposed packet switch network 1968 – ARPA awards contracts for four nodes in ARPANET to UCLA (Network Measurement), Stanford Research Institute (Network Information Center), UCSB (Interactive Mathematics) and U Utah (Graphics); BBN gets contract to build the IMP switches Colleagues on Kleinrocks from MIT go on to lead computer science program at ARPA BBN = Bolt Beraneck and Newman Inc/ IMP = Interface Message Processors Senator Edward Kennedy sends message to BBN congratulating on Their million dollar ARPA grant to build the “Interfaith” Message Processor and praising them for their ecumenical efforts
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1969: First Connections 4/7/1969 – First RFC (“Host Software” by Steve Crocker) basis for the Network Control Protocol(NCP) 9/2/1969 – Leonard Kleinrock’s computer at UCLA becomes first node on the ARPANET 10/29/1969 – First packets sent; Charlie Kline attempts use of remote login from UCLA to SRI; system crashes as “G” in entered
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1967-1971: So what do we do with it?
– Vint Cerf, graduate student in Kleinrock’s lab, works on application level protocols for the ARPANET (file transfer and Telnet protocols) Ray Tomlinson of BBN writes application; derived from two existing: an intra-machine program (SENDMSG) and an experimental file transfer program (CPYNET)
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Networks Growing First cross-country link installed by AT&T between UCLA and BBN at 56kbps Other networks: ALOHAnet (microwave network in Hawaii), Telenet (commercial, BBN), Transpac (France) 1973 – Ethernet was designed in 1973 by Bob Metcalfe at Xerox Palo Alto Research Center (PARC) How do we connect these networks together? Initial ARPAnet was a single closed network – to communicate with an ARPA host one had to be attached to another ARPAnet IMP
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1972-1974: Protocol Development
– Robert Kahn and Vint Cerf develop protocols to connect networks without any knowledge of the topology or specific characteristics of the underlying nets 1972 – Robert Kahn gives first public demonstration of ARPAnet (now 15 nodes) at International Conference on Computer Communication NCP – first host to host protocol To get things moving Research and Development on the right replacement
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1974-1978: Development of TCP/IP
1974 – First full draft of TCP produced November First three-network TCP/IP based interconnection demonstrated linking SATNET, PRNET and ARPANET in a path leading from Menlo Park, CA to Univ. College London and back to USC/ISI (Marina del Ray, CA) 1978 – TCP split into TCP and IP
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1981 –1984: Base Protocols In Place
1981 – Term “Internet” coined to mean collection of interconnected networks 1982 – ISO releases OSI seven layer model; actual protocols die but model is influential 1/1/1983 – Original ARPANET NCP was banned from the ARPANET and TCP/IP was required 1984 – Cisco Systems founded
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1983-1986: Not Just a Research Project Anymore
1984 – Domain Name System introduced; hosts (200 hosts by end of 1970s; over by end of 1980s) 1986 – NSFNET created to provide access to 5 super computer centers (NSFNET backbone speeds 56 Kbps) 1983 – ARPANET split into ARPANET and MILNET; MILNET to carry defense related traffic : Open up to academics worldwide for real work
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: Growing Pains? Nodes on Internet began to double every year November 1988 – Internet worm affecting about 10% of the computers on the Internet Internet Assigned Numbers Authority (IANA) established in December with Jon Postel as its Director. Postel was also the RFC Editor and US Domain registrar for many years 1989 – Link between Australia’s AARNET and NFSNET 1989 – was this first link outside US – no? Link to univ college London?
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1990-1993: WWW Explosion 1990 – ARPANET ceases to exist
1990 – Tim Berners-Lee develops hypertext system with initial versions of HTML and HTTP and first GUI web browser called “WorldWideWeb” 1993 – Mosaic, a GUI web browser, written by Marc Andreessen and Eric Bina at NCSA takes world by storm (showed in-line images and was easy to install); WWW proliferates at a 341,634% annual growth rate of service traffic
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