learning objectives: is infrastructure: standards and...
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IS Infrastructure:Standards and Protocols
Fundamentals of IT andE-CommerceFall 2002 - Session 1bProf. Foster Provost
© Copyright IS MBA Core Faculty, 20022
Learning Objectives:
§ Discuss the technical, economic and strategic issuesassociated with information technology standards in general, and network communications in particular§ Briefly explain the concept of “abstraction” as it relates
to the representation of information in general, and the (standard) TCP/IP network protocol in particular§ Distinguish between circuit switched and packet
switched networks§ Very briefly describe the major components, operations,
and standards of the Internet and the Web (hosts, IP addresses, routers, TCP/IP, http, html)• distinguish between the Internet and the Web
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N e t w o r k s&
D a t a b a s e s
Transact ionP r o c e s s i n g
S y s t e m s ( T P S )
M a n a g e m e n tIn format ion
S y s t e m s ( M I S )
K n o w l e d g e S y s t e m s ( K S )D e c i s i o n S u p p o r t S y s t e m s
( D S S )A Unified Framework
more structuredtasks
less structuredtasks
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Standards for Representing and Communicating Information
§ Representation:• ASCII (American Standard Code for Information Interchange)• HTML (HypterText Markup Language)• XML (eXtensible Markup Language)
• PDF (Portable Document Format)• .doc, .ppt, .xls
§ Communication:• SMTP (Simple Mail Transfer Protocol) (E-mail)• HTTP (HyperText Transfer Protocol) (Web)• FTP (File Transfer Protocol)
• TCP/IP (Transmission Control Protocol/Internet Protocol) (Packet Switching -> the Internet)
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What is HTML?
§ Hypertext Markup Language
§ A formatting language: Specifies how to format and display text and graphics.
§ Web programminglanguages:• Java• JavaScript• ActiveX• CGI scripts• Perl scripts
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Abstraction: Representing, Processing & Communicating Information
1 0 1 1 0 1 1 0 1 0 0 1
Representations
AND, OR, NOT
12.34, 42, $15.45, “Sam” +, -, *, /, ^, <, >
Customer Product Ship(customer, product)
Operations
1 0 1 1 0 1 1 0 1 0 0 1
Representations
AND, OR, NOT
12.34, 42, $15.45, “Sam” +, -, *, /, ^, <, >
Customer Product Ship(customer, product)
Operations
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Abstraction – bits to … web pages?
01000001011100110110101100100000010001100110111101110011011101000110010101110010
•web page• html• text
• characters• ascii
• numbers• bytes• bits
“Ask Foster”
A = 65 = 01000001
8 bits = 1 byte
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Information on the “Web”
Fall 2002
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HTML – Hypertext Markup Language
<html><head>
<title>Welcome!</title></head><body><h1>Welcome to the IT Core Example Page!</h1><h2>Fall 2002</h2><p><br>This is an example of a simple html web page.<p><i>ENJOY!</i><p><i>(<a href="http://www.stern.nyu.edu/~fprovost">Want to go to Provost'shome page?</a>)</i> </body></html>
“marked up”
http://www.stern.nyu.edu/~fprovost/Classes/Core-S2002/example.html 10
Information on the Web
§ Hypertext -- allows linking between “pages”§ Markup Language
• a structured language that allows you to specify logical structure of a document
• by “marking it up” -- adding tags along with text
§ Browser interprets tags• displays text according to logical structure• different browsers may choose to display the same logical
structure differently• example: a “first-level heading”
– bold vs. large vs. italic vs. colored vs. ...
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Hypermedia
Text with Hyperlink (HTML):
<p><i>(<a href="http://www.stern.nyu.edu/~fprovost“> Want to go to Provost's home page?</a>)</i>
Image with Hyperlink (HTML):
<p> Professor Bakos:
<a href="http://www.stern.nyu.edu/~bakos/bakos-max.jpg"><img src="http://www.stern.nyu.edu/~bakos/bakos.jpg"
alt="Bakos photo" width="186" height="250"></a>
http://www.stern.nyu.edu/~fprovost/Classes/Core-F2001/example2.html
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Circuit-Switched Network
§ Set of switches connected by lines (channels)§ Communication takes place by opening circuits:
• end-to-end dedicated connection between two communicating stations
§ Example: Telephone network
Line
Switch
Circuit
Circuit
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Circuit-Switched Network
§ Key concept: Reserved Capacity§ The line and switches are dedicated for the
duration of communication§ This guarantees continuous communication
• Never get less than reserved capacity• No congestion or delays (once you have a circuit)
§ …but is expensive• Pay for bandwidth whether you use it or not• Good for voice• Inefficient for data
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§ Packet Switching• Breaks each message into packets (frames)• Sends these packets one after the other
§ When a packet arrives, the switch must decide which of several successor switches to send it to• decision needs to be made continuously at each switch• Each packet of a message may go through a different
sequence of switches
• may arrive out of order, get lost, etc.• layers of protocols deal with problems
Switch A
B
C
D
Packet Switched Data Network
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?
?Packet01101010101000010101011100
……..
01101010101000010101011100
01101010101000010101011100
01101010101000010101011100
Packets0110110111101111101111101010110111……….01110
Message
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How the Internet works…
……..
01101010101000010101011100
01101010101000010101011100
01101010101000010101011100
2. broken into packets
5. packets reassembled
0110110111101111101111101010110111……….01110
1. binary representation on sender’s computer
3. packets sent over network
Internet 4. packets received by
receiver’s computer
01101010101000010101011100
01101010101000010101011100
01101010101000010101011100
……..
6. binary representation on receiver’s computer
0110110111101111101111101010110111……….01110
What the sender sees
What the receiver sees
Internet
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The Internet
Network Addresses• Unique address for each computer (“host”) on the Internet• IP addresses, host names• 128.171.17.13, fprovost.stern.nyu.edu• Domain name servers map IP addresses (numbers) to host names
Host
Host
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The Internet: Routers
§ Routers• Cooperate to give an end-to-end route for each packet• Have “routing table” to determine appropriate next
“hop” for a packet, based on destination IP address• Internet is “self healing” – routing tables updated
Host
Host
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§ The TCP/IP Standard
Networking Standards
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Standards: Technical Rationale
§ How many different “interfaces” are required to connect N different computers to all others in a network?• Without a standard
– At worst N*(N -1)
• With a single standard– At worst 2N
§ Not just network-communication standards• B2C Web interactions• office collaboration (de facto standards e.g., .pdf., MS-Word)• B2B data transactions• etc.
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Standards: Economic Rationale and Strategic Implications
§ Economic Rationale• Economies of scale in production• Demand-side economies of scale
– The more common a standard the cheaper it is to use– Consumer value increases as more users follow standard
(network externalities)
§ Strategic Implications• Standards may affect competitive advantage• Standards enable new strategies, products and
markets (e.g., Dell On-line, Voice over IP, Web Services)