Internet Intranet CIS536 Getting Started Introduction to Internet

Internet / Intranet CIS-536 Getting Started Introduction to Internet Technologies

Class 1 Agenda • Introduction – Syllabus – Homework • Introduction to Internet Technologies – Internet History and Protocols – Networking Principles: TCP/IP 3

Web Hierarchy TECHNOLOGY Key Components Web Applications Web Forms World Wide Web Core Internet Protocols The Internet Networking Scripting CGI HTML, Browsers, Web Servers SMTP (Mail), FTP, Telnet TCP/IP, DNS, Backbone OSI Model, Ethernet, LANs Operating Systems UNIX, Windows, Other O/S Computers Mainframes, Minis, PC’s 7

Networking Roots • Why? A Need to Transfer Data Between Computers • Issue: Computers Vary Widely – Multiple Manufacturers, Types • • • Mainframes: IBM, BUNCH Minis: Same + DEC, DG, HP, etc. PC’s: IBM, Apple Variations: Speed, Disk Space, Peripherals, Technology – Operating System (O/S): – • • – Now: Unix, Windows, Mac, Other Before: IBM, BUNCH, Unix, VMS User Interface: Text-Based, Graphical, Hand-Held • The Need: – File Transfer Between Computers – Data Transfer Between Computers • Session-Based 8

Networking Options • Basic: (One Sender / One Recipient at a Time) – “Print and Re. Key” – “Sneaker. Net” – Direct “Dumb” Connection • – E. g. Parallel Port Modem • • Protocols: File Transfer Protocols – E. g. XMODEM, ZMODEM • Advanced: Non-Dedicated – Shared Connection • • Broadcast – Filters Routing 9

Physical Networking Issues • Distance Between Machines – Local – LAN – Metropolitan (MAN) – National / International (WAN) • Public vs. Private Networks • Cable Type: (e. g. UTP, Coax, Fiber) • Wiring Topology 10

Network Topologies DIRECT STAR RING BUS 11

Communication Issues • Connection Type – Circuit vs. Packet • • – Circuit: Session Based Packet: Package Based Packet Details • • Size Format Routing – Bandwidth Sharing – • • Load Balancing Routing Error Handling – Security – 12

The OSI Networking Model • An Attempt to Separate Physical Issues, Communication Issues, etc. • The Concept: – Each Layer Is Independent • • • “Black Box Approach” A Layer Has No Knowledge of Other Layer’s Internal Structure Allows Layers to Be Swapped In and Out Easily • The Reality: – Pure OSI is Too Slow – Most Implementations Cross Layers – Nevertheless: Useful Conceptual Model to Understand Networking 13

OSI Networking Model 7 6 5 4 3 2 1 Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer 14

OSI Layers (1) • 1. Physical Layer – The physical cable that connects the computer to the network (e. g. RS-232 C, UTP) • 2. Data-Link Layer – Moves data from the computer to the cable – Physical addressing – Packages the data according to pre-determined rules • 3. Network Layer – Addressing • 4. Transport Layer – Reliability – Error Handling / Quality Control 15

OSI Layers(2) • 5. Session Layer – Connection Management – Interfaces between O/S and the lower layers. • 6. Presentation Layer – The Operating System / GUI • 7. Application Layer – The Application Doing the Communication 16

TCP / IP • The Basic Protocol of the Internet • Covers Layers 3 -4 of the OSI Model ( Network / Transport Layers) • Multiple Layer 1 -2 (Physical / Data Transport) Protocols Are Supported Ethernet – Direct Connection – Token Ring – Modems / Dial-Up – 17

Why Is the OSI Model Important? • Great Lesson in Practical Software Engineering and the Role of Standards: 1. The Goal Of Independent Layers Was Proper and Valuable – 2. The Model Turned Out to Be Impractical In Its Details – • • Only Implementation Could Expose All of the Impracticalities Some of It Was Probably Wrong Anyways 3. Implementer’s Violated The Model to Achieve Market Success – 4. Yet, The Goal Survived – – Question: Is the OSI Model a Success or a Failure? • • No: In Practice Nobody Actually Follows It Yes: Without It, We Wouldn’t Have As Many Choices For Connecting to the Internet 18

Web Hierarchy TECHNOLOGY Key Components Web Applications Web Forms World Wide Web Core Internet Protocols The Internet Networking Scripting CGI HTML, Browsers, Web Servers SMTP (Mail), FTP, Telnet TCP/IP, DNS, Backbone OSI Model, Ethernet, LANs Operating Systems UNIX, Windows, Other O/S Computers Mainframes, Minis, PC’s 19

Internet Enabling Technologies • TCP/IP – A Method to Assign a Unique Address to Computers • IP Address: 32 bit Address A Method to Create and Address Packages of Data – A Method to Route Data Between Computers – A Method to Share the Network Bandwidth – Error Handling and Other Advanced Networking Features – • DNS – A Method to Link Names to 32 Bit IP Addresses – Lookup the Name in a DNS Database – Efficient Method to Maintain DNS Databases Worldwide 20

TCP / IP • IP : Internet Protocol – Addressing – Routing – Packaging • TCP : Transmission Control Protocol – Advanced Traffic Management – Error Detection / Correction 21

IP Addressing Each Machine (“Host”) Has Its Own Unique Address – Related Machines Are Grouped Into “Networks” – • – The Address Identifies the Network as Well as the Node 32 Bit Address • • Broken into four 8 -bit chunks: – Written as: xxx Higher Order Bits Identify the Network 22

IP Addressing (2) – Different Classes of Networks: • • • – Subnetting • – Class A (Very Large Networks) – IP addresses: 1. 0. 0. 0 to 127. 0. 0. 0 Class B (Large Networks) – IP addresses: 128. 0. 0. 0 to 191. 254 Class C (Small/Medium Networks) – IP addresses: 192. 0. 0. 0 to 223. 254 Breaking Up a “Network” Into Smaller Networks – Subnet Mask: Logical And with IP Address to Define the Network Special Reserved Addresses • • 0, 1, 2, 255 – Reserved – Define Network, Broadcast, etc. 127. xxx – Loopback 23

IP Routing • Typical WAN Challenges – How to Balance the Load Across the Network? – Must Localize Traffic to Conserve Bandwidth Analogy: Postal Service Get a Package From Point A to B – Minimize the Number of Miles a Package Travels – Optimize Use of “Bandwidth” – • e. g. Jeeps/ Semi-Trailers / Airplanes 24

“Postal” Routing Example • Solution : Create a “Distribution Center” Hierarchy Boston Los Angeles UCLA Chicago Waltham Brandeis J. Smith Cambridge MIT Polaroid Feldberg 123 W 3 C 25

IP Routing Example • Solution : Emulate a “Distribution Center” Hierarchy NOTE: For Demonstration Only. Not Real IP Addresses or Structure Boston 129. 0. 0. 0 Los Angeles 164. 67. 0. 0 UCLA 164. 67. 80. 0 J. Smith 164. 67. 80. 123 Chicago 198. 23. 0. 0 Polaroid 129. 64. 95. 0 Waltham 129. 64. 0. 0 Brandeis 129. 64. 99. 0 Feldberg 123 129. 64. 99. 128 Cambridge 129. 70. 0. 0 MIT 129. 70. 53. 0 Lab 1 129. 70. 53. 41 26

IP Routing Details • IP Specifics – Routers (Gateways) Serve as Distribution Centers – Routers Responsible for Where Package Goes Next • • “Store and Forward” Multiple Paths From Sender to Recipient Nodes Within A Network Can Communicate Without Going Through the Router – Each Node Must Know the Name Of Its Router (Network) – • – Subnet Mask Used to Identify Routers (Networks) IP Address is Used For Routing • Hierarchical 27

IP Packets • The Challenge: – How to Share the Bandwidth Evenly? – How to Recover From Data Errors? • The Solution – Packet Based, not Circuit Based – Packet Size Limits – Large Packages broken-up into Smaller Packets – Each Packet Can Travel A Different Route • • – Packets May Arrive at Different Times Total Package Must Be Reassembled at Destination If an Error Occurs, Only the Damaged Packet Must Be Retransmitted 28

IP Packaging 4 1 1 2 3 4 5 Sender 4 5 I N T E R N E T 1 2 3 4 3 5 5 Recipient 29

The IP Packet • Byte 1: – Version (4 bits) • • Version 4 is Common Version 6 is Latest Packet Header Length (4 bits) – Type of Service (8 bits) – • – Priority – Ignored by Most Routers Length (8 bits) • • Total Length of Packet Min: 576 bytes, Max: 65, 525 bytes • Byte 2: – ID, Fragmentation Info • Unique ID for Packet and Fragmentation Info 30

The IP Packet (2) • Byte 3: – Time To Live (8 bits) • – Protocol ID (8 bits) • – Helps Identify When a Package is Undeliverable 6 is TCP Checksum (16 bits) • Byte 4: – Source IP Address • Byte 5: – Destination IP Address • Next Byte(s): – Optional Header Information • Next Bytes: – The Data Itself 31

The Future of IP • Current Version: IPv 4 – 4 Billion Theoretical IP Addresses • – “Smart Devices” Will Want IP Addresses • – In Practice, Many Less Available e. g. Refrigerators! Routing Tables Getting Less Efficient • IPng – IP Next Generation (IPv 6) – 128 Bit Addresses – Faster Routing – Security Mechanisms 32

The TCP in TCP / IP • Ports – IP Address Is Not Enough • • A Computer May Have Multiple Applications Running Allows Applications to Distinguish Communications Meant For Them • TCP – Transmission Control Protocol – Manages the Traffic More Efficiently • – e. g. Makes Sure That A Connection Exists Before Sending Full Package Advanced Error Detection / Correction • Breaks Up and Reassembles Packets • UDP – In Between IP and TCP – Less Error Detection – Therefore Faster – Sometimes Used Locally 33

The TCP Packet • Carried Within the IP Data • Byte 1: – Source Port (16 bits) – Destination Port (16 bits) • Byte 2: – Sequence Number • Byte 3: – Acknowledgment Number • Next Bytes: – Header Length, Flags, Options 34

DNS Naming Conventions • (Host). (Sub. Organization. . ). (Organization). Domain – Common Domains • • • Edu, Org, Com, Net Country: e. g. UK, NL “Right to Left” Hierarchy Find the Name Server for the Domain (e. g. edu) – Find the Name Server for The Organization – Then Suborganization(s), Host – 35

Internet Enabling Technologies • Core Communications Backbone – Others Connect to the Backbone via Established Node • New Connectivity Options – Dedicated (T 1, T 3) – Dial-Up Over Standard Telephone Lines • – Advanced Modem Technologies (e. g. 56 KB) Other Substitutes • • Cable. Modems x. DSL 36

In Class Exercise: IP Addresses • Feldberg Accounts • IP Exercises – ipconfig – tracert 37

Web Hierarchy TECHNOLOGY Key Components Web Applications Web Forms World Wide Web Core Internet Protocols The Internet Networking Scripting CGI HTML, Browsers, Web Servers SMTP (Mail), FTP, Telnet TCP/IP, DNS, Backbone OSI Model, Ethernet, LANs Operating Systems UNIX, Windows, Other O/S Computers Mainframes, Minis, PC’s 38

Core Internet Protocols • • Enable Computers to Share Data Using Non-Proprietary Standards Built on TCP/IP – Telnet • – FTP – File Transfer Protocol • • – Download/Upload Files From One Computer to Another Basic File-Type Conversion – ASCII / EBCDIC » Binary Format of Characters – UNIX, MS-DOS/Windows » Line Termination Characters Electonic Mail – SMTP/POP • • – Remote Login Mail Servers Established to Act as Post Offices Multiple Users Have Accounts at Post Office News Groups - NNTP • • Electronic Bulletin Boards Users Can Share Information 39

The Internet – In The Beginning – Late 1960’s • • • Limited to Military and Academic Researchers Military wanted a system that would continue to function when parts of network were disabled ARPA Net – Advanced Research Projects Agency (DOD) 1969 – 4 nodes – 1971 – 15 nodes – 1972 – BBN Wins Bid to Build a Packet Switched Protocol – • The Result: TCP/IP 1973 – International. Added London, Sweden. – 1979 – Usenet Created – • – Newsgroups 1983 – Split into 2 nets: • • • MILNET – military only NSFNET – (National Science Foundation) – Supercomputers linked for distributed processing Universities added on to allow their students access to supercomputers. 40

Internet: Pre-Commercialization – NSF’s Acceptable Use Policy: • • – Independent Bulletin Board Systems (BBS) Begin to Convert to Usenet • – For Research and Education Only. Commercial / For-Profit Activity Excluded 1985 – The WELL (Whole Earth Electronic Link) New Protocols Join email, telnet, usenet • • Gopher – Campus Information System WAIS – Document Retrieval 1987 – Over 10, 000 nodes – 1990 – 100, 000 nodes. 9 countries – 41

Before the Web • Information Shared Publicly via FTP – Relevant Documents Listed in a Directory • • • Must Be Organized By Directory User Must Know That Directory Exists File Names Only – No Descriptive Information • Clearly a Need to Organize Information – Archie • – Gopher • – Catalog of FTP Servers Menu Based Organization of Files WAIS • Library of Files With Search Capabilities 42

Archie The First Search Engine? – Maintains a Catalog of Anonymous FTP Servers – • – Users Login to an Archie Server • • – Can Search by Keyword Lists FTP Servers Where File Can Be Found Descriptive Index • • – Client Contacts Each Server Monthly – Lists All of the Files Available via Anonymous FTP – Maintains This List Locally – Based on FTP: No Special Process Needed on Server Administrator’s Keep Index of Available Files – Add Comments – No Standard Format Comments Become Searchable Email Interface • Submit Search via email, Get Results Back as an email 43

Gopher – A Desire to Distribute Campus Information Online • – Session Based • • – Requires a Client and Server TCP/IP Communication via Port 70 Menu Based System • • • – Originated at University of Minnesota List of Menu Choices Can “Drill Down” a Menu Text-Based – Most Terminals Support 25 Lines of Text Allows Links to Other Gopher Sites • • • Allows Different Groups to Maintain Their Own Files CSO – Text Based Forms / Processing Allows FTP Through Same Interface 44

WAIS – Wide Area Information Service • Improved Search Engine • Full-Text Search and Retrieval • Session Based – TCP/IP Communication via Port 210 • Requires a “Librarian” to Maintain an Index • Servers Can Ask Another to Perform a Search • XWAIS – X-Windows GUI to WAIS 45

Internet – Pre-Commercialization • Non-Commercial Culture Develops • Lots of Public Domain Software – UNIX – The Free Software Foundation • • Richard Stallman General Public License • Spirit of Cooperation – Newsgroups • “Netiquette” – Self-Policing Rules 46

Web Hierarchy TECHNOLOGY Key Components Web Applications Web Forms World Wide Web Core Internet Protocols The Internet Networking Scripting CGI HTML, Browsers, Web Servers SMTP (Mail), FTP, Telnet TCP/IP, DNS, Backbone OSI Model, Ethernet, LANs Operating Systems UNIX, Windows, Other O/S Computers Mainframes, Minis, PC’s 47

Web Beginnings • 1991 - Internet Commericalization – NSF lifts restriction forbidding commercial traffic • 1990 – Tim Berners-Lee Proposes Web Structure to CERN (Center for European Research) – Goal: To Distribute Research Across CERN’s Many Laboratories and Affiliates • New Protocol: HTTP – Encapsulates Multiple Internet Protocols • – FTP, Gopher, etc. Files Identified by URL – Uniform Resource Locator 48

Web Beginnings (2) • Hypertext Markup Language (HTML) – Modification of SGML – Standard Generalized Markup Language – Hypertext • • – Includes “Links” to Other Places Within the Document Includes Links to Other Documents Why Hypertext? • • • Allows Distributed Documents Maintainability - Documents More Current Storage Doesn’t Need to Be Duplicated 49

The Need For HTML – Need For Portable Method to Distribute Technical Documents • • • – Options • • • – GUI’s Not Prevalent – Most Used “Dumb Terminals” » Fonts, Characters Per Line, Lines Per Screen Varied Many Different Operating Systems – Hardware Limitations No Standard Word Processing Applications Plain Text – No Formatting Print-Based – Postscript, GIF – Large Files, No Searching Text-Based – Te. X, RTF, nroff – Describe How to Print Document » Display Capabilities Vary Solution: HTML • Describes Document’s Content, Not its Format 50

Web Client (Browser) Development • HTML Requires an Application to Display it • First Browser: www (1991) – Text Based • GUI’s Becoming More Prevalent – Apple Macintosh – MS-Windows – X/Motif (UNIX) • First Graphical Browsers – 1993 - Mosaic (NCSA – National Center for Supercomputing Applications) • • Available on all Platforms Public Domain • Netscape Communications Corporation (1994) – Private Corporation. Founded By Mosaic’s Creators • Microsoft Internet Explorer 51

Browser Wars • Netscape – Extended HTML With “Custom” Extensions – “Plug-Ins” – Allow Local Applications to Run Within Browser • Microsoft Internet Explorer – Based on Spyglass’ Mosaic – Custom Extensions to HTML – Active X – Microsoft Equivalent of Plug-Ins • Other Browsers Left Behind – Custom Extensions Make it Difficult to Keep Up – Changes the Web Significantly • – Universal Accessibility is Sacrificed – Requires GUI – Requires Current Hardware HTML Standards Expand Rapidly • Goal: To Create a Single Standard Used by Both Browsers 52

Who’s Managing the Web? • Web Commercialization/Competition Changes Culture – Internet Experiences Exponential Growth • 1994 - CERN/MIT Found the World Wide Web Consortium (W 3 C) Attempt to Manage/Control Standards – Member Organizations Only – IETF – Internet Engineering Task Force – • Protocol Engineering and Development – Open to Individuals • CERN Drops Out – INRIA Takes Over for CERN (Funded by EC) • New Extensions to Web Usage – Two-Way Communications (e. g. Forms) – Advanced UI Functionality (Scripting, Java) 53

Web Hierarchy TECHNOLOGY Key Components Web Applications Web Forms World Wide Web Core Internet Protocols The Internet Networking Scripting, Applets CGI HTML, Browsers, Web Servers SMTP (Mail), FTP, Telnet TCP/IP, DNS, Backbone OSI Model, Ethernet, LANs Operating Systems UNIX, Windows, Other O/S Computers Mainframes, Minis, PC’s 54

For More Information – Portal • – Internet History • • – Hobbes Internet Timeline – http: //info. isoc. org/guest/zakon/Internet/History/HIT. html Free Software Foundation /GNU – http: //www. gnu. org Networking • – http: //www. internet. com Brandeis: Computer Networks and Data Communications TCP/IP, FTP, etc. • • Brandeis: TCP/IP Winsock Programming – Windows Sockets Network Programming by Bob Quinn and Dave Shute. Addison-Wesley Brandeis University Internet/Intranet Spring 2000 57