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1CMPE 150- Introduction to Computer Networks
CMPE 150
Fall 2005Lecture 1
Introduction to Computer Networks
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2CMPE 150- Introduction to Computer Networks
Class Information• Class time and location:– M, W, F from 2:00 – 3:10.– E2 180
• Class Web page:– http://www.cse.ucsc.edu/classes/cmpe150/Fall05
• Instructor:– Katia Obraczka– E2 323– Office hours: TBD– [email protected]
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3CMPE 150- Introduction to Computer Networks
Class Information
• Teaching Assistant– Sudharsan Rangarajan• E-mail: [email protected].
• Lab Assistants– Jay Boice ([email protected]).
– Todd Nagengast ([email protected]).
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4CMPE 150- Introduction to Computer Networks
Textbook
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5CMPE 150- Introduction to Computer Networks
Pre-requisites
• CMPE 16• CMPE 12C/L
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6CMPE 150- Introduction to Computer Networks
Focus
• Intro to data networks from an engineering perspective.
• Broad coverage.– Network architectures.
– Network protocols,
– Layered design.
– Protocol stack.
– TCP/IP and the Internet,
• Hands-on aspect.
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7CMPE 150- Introduction to Computer Networks
Topics Covered
• Introduction and Overview.
• Physical Layer.• Medium Access Control
(MAC).• Link Layer.• Network Layer.• Routing.
• Internetworking and IP.• IP Routing and Control.• Transport Layer.• Application Layer.• Putting It All Together!
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8CMPE 150- Introduction to Computer Networks
Other Networking Courses• CE 151 Network Administration• CE 152 Protocols• CE 156 Network Programming• CE 107 Stochastic System Analysis • EE 103 Signals and Systems • CE 154 Data Communication • CE 153 Digital Signal Processing• EE 151 Communications Systems• CE 108 Data Compression• CE 163 Multimedia• CS 111 Operating Systems
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9CMPE 150- Introduction to Computer Networks
Grading• Mid-term 35%• Assignments 25%– Homework
– Labs
• Final 40%
No credit for work that is not your own.
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10CMPE 150- Introduction to Computer Networks
Academic Integrity
• Academic integrity policies will be strictly enforced!
• Academic integrity policy violations will NOT be tolerated!
• http://www.ucsc.edu/academics/academic_integrity/policy.html
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11CMPE 150- Introduction to Computer Networks
Course Outline
• Introduction– History, basic concepts, terminology.
– More, “not-so-basic” concepts:protocols, layering,, etc.
• Physical layer– Transmitting data.
• Data link layer– Reliable transmission.
– Accessing the communication medium• Medium access control protocols.
• LANs– Ethernet, token ring, wireless LANs.
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12CMPE 150- Introduction to Computer Networks
Course Outline (cont’d)
• Network layer– Types of network services.
– Circuit- vs. packet switching.
– Virtual circuits and datagrams.
– Routing.
– Addressing.
– Unicast and multicast.
• Internetworking– IP.
– The Internet.
– IP Routing and Control.
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13CMPE 150- Introduction to Computer Networks
Course Outline (cont’d)• Transport layer
– E2E communication..– Types of transport service.– Connectionless versus connection-oriented.– UDP.– TCP.
• Application layer– DNS, ssh, telnet, ftp, news, e-mail.– The Web.
• HTTP.• HTML.• Search engines.• Proxy and caches
– Peer-to-peer.– Security.
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14CMPE 150- Introduction to Computer Networks
What’s a network?
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15CMPE 150- Introduction to Computer Networks
What’s a network?
• Merriam-Webster Dictionary:– “|A fabric or structure of cords or wires that
cross at regular intervals…”
– “A system of computers, terminals and databases connected by communication lines”
• “A computer network is defined as the interconnection of 2 or more independent computers.” [Ramteke,”Networks”, pg. 24].
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16CMPE 150- Introduction to Computer Networks
Why network?
• Before networks: – One large computer (mainframe) used for all
processing in businesses, universities, etc.
• Smaller, cheaper computers…– Personal computers or workstations on
desktops.
– Interconnecting many smaller computers is advantageous! Why?
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17CMPE 150- Introduction to Computer Networks
Ubiquitous Computing
• Computers everywhere.• Also means ubiquitous communication.– Users connected anywhere/anytime.
– PC (laptop, palmtop) equivalent to cell phone.
• Networking computers together is critical!
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18CMPE 150- Introduction to Computer Networks
Computer Network
• Provide access to local and remote resources.• Collection of interconnected end systems: – Computing devices (mainframes, workstations,
PCs, palm tops)
– Peripherals (printers, scanners, terminals).
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19CMPE 150- Introduction to Computer Networks
Why network?• Resource sharing!– Hardware: printers, disks, terminals, etc.– Software: text processors, compilers, etc.– Data.
• Robustness.– Fault tolerance through redundancy.
• Load balancing.– Processing and data can be distributed over
the network.• Location independence.– Users can access their files, etc. from
anywhere in the network.
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20CMPE 150- Introduction to Computer Networks
Problems?
• Security!– It’s much easier to protect centralized
resources than when they are distributed.
– Network itself as the target..
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21CMPE 150- Introduction to Computer Networks
Some History
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22CMPE 150- Introduction to Computer Networks
Before the Internet
• Postal network.– Delivers different types of objects (letters,
packages, etc.) world-wide.– Relatively high delay but relatively cheap.– Sender and receiver identified by their postal
address (name, number, street, city, etc.).• Telephone network.– Engineered to deliver real-time voice.– Also world-wide.– Low delay but more expensive.– Users identified but telephone number.
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23CMPE 150- Introduction to Computer Networks
The Telephone Network
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24CMPE 150- Introduction to Computer Networks
The Telephone Network
• Telephone was patented by G. Bell in 1876.• For one telephone to be able to talk with
another telephone, a direct connection between the two telephones was needed.– Within one year, cities were covered with a
wild jumble of wires!
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25CMPE 150- Introduction to Computer Networks
The Telephone Network (cont’d)
• In 1878, the Bell Telephone company opened its first switching office (in New Haven, CT).
• Each user would connect to the local switching office.– When a user wanted to make a call, s/he rang
to the office, and would be manually connected to the other end.
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26CMPE 150- Introduction to Computer Networks
The Telephone Network (cont’d)
• To allow for long-distance calls, switching offices (switches) were connected .
• Several connections can go through inter-switch trunks simultaneously.
• At some point, there were too many connections between switching offices!
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27CMPE 150- Introduction to Computer Networks
• Thus, a second-level hierarchy was added.
• The current telephone system has at least five levels of hierarchy.
The Telephone Network (cont’d)
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28CMPE 150- Introduction to Computer Networks
Addressing
• Uniquely identifies users.• Examples: – Postal address, telephone number.
• Types of addresses:– Flat.
– Hierarchical.
– Are postal addresses flat or hierarchical?
– And phone numbers?
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29CMPE 150- Introduction to Computer Networks
POTS or PSTN
• For over 100 years, the POTS (Plain Old Telephone System) a.k.a. PSTN (Public Switched Telephone Network) handles voice-band communications.
• The PSTN is well designed and engineered for the transmission and switching of voice– Real-time.
– Low latency.
– High reliability.
– Moderate fidelity.
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30CMPE 150- Introduction to Computer Networks
Evolution of Communications Networks
• About 30 years ago, a second communications network was created with the goal of providing a better transport mechanism for data.
• In this class, we will study the technology underpinning data networks.
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31CMPE 150- Introduction to Computer Networks
Communication Model
Network
Source Destination
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32CMPE 150- Introduction to Computer Networks
Simplified Communication Model
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33CMPE 150- Introduction to Computer Networks
Components
• End systems (or hosts),• Routers/switches/bridges, and • Links (twisted pair, coaxial cable, fiber, radio,
etc.).
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34CMPE 150- Introduction to Computer Networks
Components (cont’d)• Source– generates data to be transmitted
• Transmitter– Converts data into transmittable signals
• Transmission System– Carries data
• Receiver– Converts received signal into data
• Destination– Takes incoming data
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35CMPE 150- Introduction to Computer Networks
Simplified Data Communications Model
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36CMPE 150- Introduction to Computer Networks
Key Tasks• Transmission.
• Signal Generation.
• Synchronization.
• Error detection and correction.
• Addressing and routing
• End-to-end Recovery.
• Security.
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37CMPE 150- Introduction to Computer Networks
Networking• Point to point communication not usually
practical– Devices are too far apart.
– Large set of devices would need impractical number of connections.
• Solution is a communications network.
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38CMPE 150- Introduction to Computer Networks
Simplified Network Model