Internet intrarnet CIS class 1

Web HierarchyOperating Systems Networking The Internet Core Internet Protocols World Wide Web Web Forms Web Applications UNIX, Windows, Other O/S OSI Model, Ethernet, LANs TCP/IP, DNS,

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

Web Hierarchy

Operating Systems

Networking

The Internet Core Internet Protocols

World Wide Web

Web Forms Web Applications

UNIX, Windows, Other O/S OSI Model, Ethernet, LANs

TCP/IP, DNS, BackboneSMTP (Mail), FTP, TelnetHTML, Browsers, Web Servers

CGI Scripting

Mainframes, Minis, PC’s

Computers

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

Networking Options

• Basic: (One Sender / One Recipient at a Time)

– “Print and ReKey”

– “SneakerNet”

– Direct “Dumb” Connection

• E.g Parallel Port

– Modem

• Protocols:

• File Transfer Protocols

– E.g XMODEM, ZMODEM

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

Network Topologies

Communication Issues

• Connection Type

– Circuit vs Packet

• Circuit: Session Based

• Packet: Package Based

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

OSI Networking Model

Physical Layer Data Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer

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

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

Web Hierarchy

Operating Systems

Networking

The Internet

Core Internet Protocols

World Wide Web

Web Forms Web Applications

UNIX, Windows, Other O/SOSI Model, Ethernet, LANs

TCP/IP, DNS, Backbone

SMTP (Mail), FTP, TelnetHTML, Browsers, Web Servers

CGI Scripting

Mainframes, Minis, PC’sComputers

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

• TCP : Transmission Control Protocol

– Advanced Traffic Management

– Error Detection / Correction

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

IP Addressing (2)

– Different Classes of Networks:

• Class A (Very Large Networks)

• 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

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

“Postal” Routing Example

• Solution : Create a “Distribution Center” Hierarchy

IP Routing Example

• Solution : Emulate a “Distribution Center” Hierarchy

NOTE: For Demonstration Only Not Real IP Addresses or Structure

Los Angeles

164.67.0.0

Boston 129.0.0.0

Waltham129.64.0.0

Brandeis 129.64.99.0

Cambridge129.70.0.0

Polaroid 129.64.95.0

Feldberg 123 129.64.99.128

UCLA

164.67.80.0

MIT 129.70.53.0

Lab 1 129.70.53.41

J Smith

164.67.80.123

Chicago 198.23.0.0

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

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

4 2

1

3

1 2 3 4 5

I N T E R N E T

– 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

The IP Packet (2)

• Byte 3:

– Time To Live (8 bits)

• Helps Identify When a Package is Undeliverable

The Future of IP

• Current Version: IPv4

– 4 Billion Theoretical IP Addresses

• In Practice, Many Less Available

– “Smart Devices” Will Want IP Addresses

• e.g Refrigerators!

– Routing Tables Getting Less Efficient

• IPng – IP Next Generation (IPv6)

– 128 Bit Addresses

– Faster Routing

– Security Mechanisms

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

The TCP Packet

• Carried Within the IP Data

• Byte 1:

– Source Port (16 bits)

– Destination Port (16 bits)

DNS Naming Conventions

• (Host).(SubOrganization ).(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

Internet Enabling Technologies

• Core Communications Backbone

– Others Connect to the Backbone via Established Node

• New Connectivity Options

– Dedicated (T1, T3)

– Dial-Up Over Standard Telephone Lines

• Advanced Modem Technologies (e.g 56 KB)

– Other Substitutes

• CableModems

• xDSL

In Class Exercise: IP Addresses

• Feldberg Accounts

• IP Exercises

– ipconfig

– tracert

Web Hierarchy

Operating Systems

Networking The Internet

Core Internet Protocols

World Wide Web

Web Forms Web Applications

UNIX, Windows, Other O/SOSI Model, Ethernet, LANs TCP/IP, DNS, Backbone

SMTP (Mail), FTP, Telnet

HTML, Browsers, Web Servers

CGI Scripting

Mainframes, Minis, PC’sComputers

Core Internet Protocols

• Enable Computers to Share Data Using Non-Proprietary

Standards

• Built on TCP/IP

– Telnet

• Remote Login

– 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

• Mail Servers Established to Act as Post Offices

• Multiple Users Have Accounts at Post Office

– News Groups - NNTP

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.

Internet: Pre-Commercialization

– NSF’s Acceptable Use Policy:

• For Research and Education Only

• Commercial / For-Profit Activity Excluded

– Independent Bulletin Board Systems (BBS) Begin to Convert to Usenet

• 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

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– The First Search Engine?

– Maintains a Catalog of Anonymous FTP Servers

• 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

– Users Login to an Archie Server

• Can Search by Keyword

• Lists FTP Servers Where File Can Be Found

– Descriptive Index

• Administrator’s Keep Index of Available Files

– Add Comments – No Standard Format

• Comments Become Searchable

– Email Interface

– A Desire to Distribute Campus Information Online

• Originated at University of Minnesota

– Session Based

• Requires a Client and Server

• TCP/IP Communication via Port 70

– Menu Based System

• 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

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

Internet – Pre-Commercialization

• Non-Commercial Culture Develops

• Lots of Public Domain Software

Web Hierarchy

Operating Systems

Networking The Internet Core Internet Protocols

World Wide Web

Web Forms Web Applications

UNIX, Windows, Other O/SOSI Model, Ethernet, LANs TCP/IP, DNS, BackboneSMTP (Mail), FTP, Telnet

HTML, Browsers, Web Servers

CGI Scripting

Mainframes, Minis, PC’sComputers

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

Web Beginnings (2)

• Hypertext Markup Language (HTML)

– Modification of SGML – Standard Generalized Markup Language

• Allows Distributed Documents

• Maintainability - Documents More Current

• Storage Doesn’t Need to Be Duplicated

The Need For HTML

– Need For Portable Method to Distribute Technical

Documents

• 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

– Describe How to Print Document

» Display Capabilities Vary

– Solution: HTML

• Describes Document’s Content, Not its Format

Web Client (Browser) Development

• HTML Requires an Application to Display it

• 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

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

Who’s Managing the Web?

• Web Commercialization/Competition Changes Culture

– Internet Experiences Exponential Growth

• 1994 - CERN/MIT Found the World Wide Web

Consortium (W3C)

– 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)

Web Hierarchy

Operating Systems

Networking The Internet Core Internet Protocols

World Wide Web

Web Forms Web Applications

UNIX, Windows, Other O/SOSI Model, Ethernet, LANs TCP/IP, DNS, BackboneSMTP (Mail), FTP, TelnetHTML, Browsers, Web Servers

CGI Scripting, Applets

Mainframes, Minis, PC’sComputers

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