Download Ch Ext 10

Chapter
Extension 10
How the Internet Works
Study Questions
Q0:How did the Internet get started?
Q.5:Who manages the Internet?
Q1: How does email travel?
Q2: What is a communications protocol?
Q3: What are the functions of the five TCP/IP— OSI
layers?
Q4: How does the Internet work?
Q5: How does www.pearsonhighered.com become
165.193.123.253?
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CE10-2
Q0:How did the Internet get started?
• Department of Defense needed a way to connect with
contractors and research partners. (1968)
– Advanced Research Project Agency Network - ARPANet
• Critical Technical components
– X.25 Packet Switching Protocol
(Network, Data Link and Physical Layers)
– TCP/IP Transmission Control Protocol/ Internet Protocol
• Network Layer and above
• Authors – Vin Cerf and Robert Kahn (1977)
– Interface Message Processors – Routers today
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CE10-3
Q0:How did the Internet get started?
(cont.)
• Killer App!! (Applications…)
– (1971) Ray Tomlinson created e-Mail
• Added attachments at the request of users
– (1991) Tim Berniers-Lee created World-Wide Web
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Q.5:Who manages the Internet?
• ARPANet becomes a public network and DoD builds a
secure alternative Milnet (1983)
• NSF inherits ARPANet but replaces with NSFNet Internet II or Information Super Highway. (1991)
• ARPANet infrastructure is sold to public companies.
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CE10-5
Q.5:Who manages the Internet?
(cont.)
• Internet Society (ISOC.org) is established
with four pillars
1.
2.
3.
4.
Standards – Internet Engineering Taskforce (IETF)
Public Policy
Training
Membership
• Internet Corporation for Assigned Names
and Numbers (ICANN.org)
• Worldwide Web Consortium (W3C.org)
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Q1: How Does Email Travel?
• Messages and attachments sent from your computer
– Broken down into pieces called packets
– Packets sent to LAN switch
• Routers determine the best way to move messages
through Internet to destination
• Software at destination email server ensures all
packets are received
– Requests missing packets to be resent
• Messages and attachments reassembled at
recipient’s email server and readied to be opened by
recipient.
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CE10-7
Q2: What Is a Communications
Protocol?
• Protocol
– Standardized means for coordinating activity
between two or more entities
– Follows a sequence of ordered steps
• Communications protocol
– Means for coordinating activities between
communicating computers
• Computers agree on protocol to use
– Broken down into layers based on category of task
performed
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CE10-8
Q3: What Are the Functions of the
Five TCP/IP— OSI Layers?
1. Reference Model for Open Systems Interconnection
(OSI)
• Seven layers
• Developed by International Organization for
Standardization (ISO)
2. Transmission Control Program/Internet Protocol
(TCP/IP)
• Four layers
• Developed by the Internet Engineering Task
Force (IETF)
3. TCP/IP-OSI architecture is a five-layer blend of OSI
and TCP/IP
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CE10-9
The Internet’s TCP/IP - OSI
Application or
Process Layer
Host-to-Host Transport Layer
Internet Protocol (IP)
Network Interface
Physical Layer
Application
Layer
Presentation
Layer
Session
Layer
Transport
Layer
Network
Layer
Data Link
Layer
Physical
Layer
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TCP/IP-OSI Architecture
• Figure CE10-3
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Layer 5: Protocols
•
•
•
•
SMTP – Simple Mail Transfer Protocol
HTTP – Hypertext Transfer Protocol
FTP – File Transfer Protocol
Three important terms
1. Architecture—arrangement of protocol layers in
which each layer is given specific tasks to
accomplish
2. Protocol—a set of rules that accomplish tasks
assigned to its layer
3. Program—a specific computer product that
implements a protocol (Example: browser)
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Layer 4: Transmission Control
Program (TCP)
• Email program (SMTP) interacts with TCP
• TCP operates at Layer 4
• TCP
– Breaks email message and attachments into
segments
– Attaches To/From addresses to each segment
– Ensures reliability that all segments are received
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Layer 3: Internet Protocol (IP)
• TCP interacts with Layer 3 protocols
• Purpose of IP:
– Route messages across an Internet
– Packages each segment into a packet
– Places IP data in front of TCP data on each packet
• Routers use IP data to decide where to send
packets
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Layers 1 and 2
• Handles basic computer connectivity
• Packages packets into frames
• Frames transmitted between programs,
switches (SW1, SW3), internal routers (RH)
• Switches facilitate communication
• TCP/IP doesn’t care what you use for Layers
1 and 2…
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TCP/IP-OSI on Your Computer
• Figure CE10-4
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Q4: How Does the Internet Work?
• Each computer and device has two
addresses: (1) physical address; (2) logical
address
• Layer 2 protocol programs use physical
addresses or MAC addresses
• Layer 3 and 4 programs use logical addresses
or IP addresses
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Network Addresses: MAC and IP
• MAC addresses
– Physical addresses
– Implemented by programs that use Layer 2
protocols
– Each NIC card given an address by manufacturer
– Address only shared within network or segment
• IP addresses
– Logical addresses
– Written as series of dotted decimals (4 or 6 Octets)
• 192.68.2.28
– Not permanently associated with hardware device
• Can be reassigned as necessary
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Public Versus Private IP Addresses
• Public IP address
– Used on Internet
– Assigned by ICANN (Internet Corporation for
Assigned Names and Numbers)
– Each address is unique
• Private IP address
– Used within private networks
– Controlled through Network Address Translation
(NAT)
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Dynamic Host Configuration Protocol
• Distributes temporary IP address to
computers and devices connecting to the
Private network
– Address loaned while computer connected to LAN
– When computer disconnected, IP address made
available to others
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CE10-20
Using TCP/IP-OSI Protocols
over the Internet
Network Address Translation
• LAN use private IP addresses
• Internet traffic uses public IP addresses
• Router has multiple IP addresses
– Private ones assigned by organization for local traffic
– Public ones assigned by ISP for Internet traffic
• Network Address Translation (NAT)
– Process of changing public IP addresses into private
addresses and reverse
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Domain Name Resolution
• Uniform Resource Locator (URL)
– User-friendly document Web address
– For Example: www.pearsonhighered.com/kroenke
• Domain name resolution
– Process of converting a domain name into a public IP
address
– Starts from the Top Level Domain (TLD)
• ICANN manages 13 special computers called root
servers distributed around the world.
– Each root server maintains a list of IP addresses of servers
that resolve each type of TLD
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Domain Name Resolution (cont’d)
• Domain name resolvers
– Thousands of computers at academic institutions,
large companies, government organizations
– Cache domain names and IP addresses locally
– Save time by not needing to go through entire
resolution process somewhere else
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CE10-23
U.S. Top-level Domains
• Figures CE10-8
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Active Review
Q0:How did the Internet get started?
Q.5:Who manages the Internet?
Q1: How does email travel?
Q2: What is a communications protocol?
Q3: What are the functions of the five TCP/IP— OSI
layers?
Q4: How does the Internet work?
Q5: How does www.pearsonhighered.com become
165.193.123.253?
Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall
CE10-25
Chapter
Extension 10
How the Internet Works