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1
The Internet and HTML
Jen GolbeckCollege of Information
StudiesUniversity of Maryland
2
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)128.0.1.5
4.8.15.2
192.28.2.5
63.6.9.12
52.55.64.2
18.1.1.4
Destination Next Hop
52.55.*.* 63.6.9.12
18.1.*.* 192.28.2.5/63.6.9.12
4.*.*.* 225.2.55.1
…
(Much simplified) Routing table for 4.8.15.2
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Addresses and Domain Names
• Every computer has an IP address– E.g. 128.135.20.100– 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
– .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. http://tinyurl.com/dw6qd ) 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– Internet is the network of computers that sends information around (email, 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)
• 1991 - 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– 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– <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– 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><title>Hello World!</title></head>
<body>
<p>Hello world! This is my first webpage!</p>
</body></html>
This is the header
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
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1958-1961: 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
27
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?
• 1967-1972 – Vint Cerf, graduate student in Kleinrock’s lab, works on application level protocols for the ARPANET (file transfer and Telnet protocols)
• 1971 - Ray Tomlinson of BBN writes email application; derived from two existing: an intra-machine email program (SENDMSG) and an experimental file transfer program (CPYNET)
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1971-1973 Networks Growing
• 1970 - 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?
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1972-1974: Protocol Development
• 1972-1974 – 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
31
1974-1978: Development of TCP/IP
• 1974 – First full draft of TCP produced• November 1977 - 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
32
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; 1000+ hosts (200 hosts by end of 1970s; over 100000 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
34
1988-1989: Growing Pains?
• 1988 - Nodes on Internet began to double every year
• November 1988 – Internet worm affecting about 10% of the 60000 computers on the Internet
• 1988 - 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
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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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