CSCE 515: Computer Network Programming

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CSCE 515Computer Network Programming

• Wenyuan Xu
• Department of Computer Science and Engineering
• University of South Carolina

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Course Goal

• Understand the basic principles of computer
  networks
• Network basic
• Basic design principles in network protocols
• Internet protocols
• Wireless network protocols
• Study the programming aspects of computer
  networks
• Socket programming
• Inter-process communication
•  Understand how network research is done
• How to determine what is important
• What are the trend

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Administrative

• Course website
• http//www.cse.sc.edu/wyxu/515Fall08/csce515.html
  
• Announcements
• Homework Assignments
• Lecture Notes
• Links to required/recommended readings
• How to reach me
• Email wyxu_at_cse.sc.edu
• Office Hours MW 400pm-500pm or by appointment
• Office SWGN 3A54
• Prerequisites CSCE 311 Operating Systems

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Textbook

• Required
• Unix Network Programming, The Sockets Networking
  API, Volumes 1, by W Richard Stevens, Bill
  Fenner, Andrew M. Rudoff, published by
  Addison-Wesley (UNP)
• Optional
• TCP/IP Illustrated Volumes 1, by W. Richard
  Stevens, published by Addison-Wesley, 1994 (TI).
• Java Network Programming, by Merlin Hughes,
  Michael Shoffner, Derek Hamner, Maria Winslow,
  Conrad Hughes, published Manning Publications
• Mailing list
• CSCE515-001_at_lists.cse.sc.edu

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Tentative topics

• OSI and TCP/IP Network models
• TCP/IP
• Socket programming
• The Internet and Internet protocol
• Web programming
• Other network programming

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Grading

• 0 Homework (1-2)
• QA
• 50 Computer Projects (4 three in C, one in
  Java)
• 20 Midterm
• 30 Final closed book, and comprehensive.
• Grading scale
• A 90 100
• B 87 89
• B 80 86
• C 77 79
• C 70 76
• D 60 69
• F lt 59

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Homework projects

• Programming Environments
• Unix workstation lab.
• 1D39 (Sun Linux)
• 1D45 (Linux)
• All students should have an account on Computer
  Science and Engineering Department Unix
  workstations
• All grading will be done on CSE Linux!
• Submission should be via Drop Box
• Make sure you understand how to submit (practice
  first)!
• Directions for submission will be posted on the
  course home page with the first assignment.

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Project grading

• It is expected that everyone is a good programmer
• Comment your code!
• Your code should be readable, structured!
• 25 of the grade depends on the quality of the
  code.
• Is the code easy to understand?
• Is it easy to make a small change of the
  functionality?
• Can code handle unexpected input, exceptions?
• Programs must come with a makefile
• Java programs must come with a shell script that
  starts them
• Sets CLASSPATH to the right value
• Remember that I will try your programs in a
  directory with a different name than you!

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Project grading

• 25 of the grade depends on documentation
• Documentations must contain
• Your name and student number
• How to use your programs
• Which program does what, which parameters are
  needed, screenshots
• A description of your programs design
• Documentations must not contain
• Your code in words
• After spending the whole weekend and today at my
  girlfriends house trying to solve the exercises
  for the Network Programming course which are due
  today, I must confess that I did not succeed in
  solving them all.

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Grading

• Horner code
• All submitted work should be yours!  
• NO sharing of code
• Do not copy code from Internet
• Discussion is encouraged

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Email Policies

• Make sure you put your course (CSCE515)  in the
  subject of the message.
• Remember that it is not my emergency if you need
  help at the last minute. I may check my messages
  in time to help you make a deadline, but this may
  not necessarily be the case.
• Ask specific question instead of general
  question.
• Bad example I dont know why it does not work?
• In general, I will answer quick questions sooner
  than one that will take a long time to answer
• In general I will monitor and respond to email
  during office hours, but in-person students will
  take precedence.

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Your Best Strategy

• Come to every lecture
• Read articles related to network protocols and
  network programming
• Do not wait till last minute to prepare for exam
  or work on project
• Enjoy the fun!

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Lectures need your help!

• Ask questions
• Correct Wenyuan! Extra credit!
• Make suggestions!
• Read something interesting and relevant to this
  course? Announce it in class!

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Introduction
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What is network?

• The term network can refer to any interconnected
  group or system.
• A computer network is composed of multiple
  computers connected together using a
  telecommunication system.
• communication system for connecting
  end-systems
• End-systems a.k.a. hosts
• PCs, workstations
• dedicated computers
• network components
• Interconnection may be any medium capable of
  communicating information
• Copper wire
• Lasers (optical fiber)
• Radio /Satellite link
• Cable (coax)
• Example Ethernet.

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Why network?

• Sharing resources
• Resources become available regardless of the
  users physical location (server based,
  peer2peer)
• Load Sharing/utilization
• Jobs processed on least crowed machine
• Resource can be shared
• High reliability
• Alternative source of supply (multiple copies)
• Computer as a communication tools

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Wide variety of types of networks

• Circuit switched
• dedicated circuit per call
• performance (guaranteed)
• call setup required
• telephone system
• Packet switched
• data sent thru net in discrete chunks
• user A, B packets share network resources
• resources used as needed
• store and forward packets move one hop at a time
• The Internet (TCP/IP)

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What is Internet?

• What is internet?
• Network of networks
• What is the Internet?
• A global internet based on IP protocol
• Internet applications
• Email
• File transfer
• Newsgroup
• File sharing
• Resource distribution
• World wide web
• Video conference
• Gaming

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Emerging networks

• Embedded networks
• Every physical object is connected
• Open/close your garage via network
• Know which milk can is about to expire
• Sensor networks
• Physical space is instrumented and connected
• Detect presence of people in a room and set
  temperature accordingly
• Know exactly how many cars on Route 26
• Disposable networks
• One time use network
• Disaster recovery, smart dust

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Characteristics

• Lots of them (density)
• Cheap unreliable elements
• Run on batteries
• Location becomes a key attribute
• Information sensing around users

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Some terms

• LAN
• WAN
• MAN

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LAN - Local Area Network

• connects computers that are physically close
  together ( lt 1 mile).
• high speed
• multi-access
• Technologies
• Ethernet 10 Mbps, 100Mbps
• Token Ring 16 Mbps
• FDDI 100 Mbps

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WAN - Wide Area Network

• connects computers that are physically far apart.
  long-haul network.
• typically slower than a LAN.
• typically less reliable than a LAN.
• point-to-point
• Technologies
• telephone lines
• Satellite communications

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MAN - Metropolitan Area Network

• Larger than a LAN and smaller than a WAN
• - example campus-wide network
• - multi-access network
• Technologies
• coaxial cable
• microwave

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Network Protocols
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Whats a protocol?

• a human protocol and a computer network protocol

TCP connection req.
Hi
Hi
protocols define format, order of msgs sent and
received among network entities, and actions
taken on msg transmission, receipt
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Organization of air travel
Although this course is about network programming
(and not about networking in general), an
understanding of a complete network model is
essential.
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Organization of air travel a different view

• Layers each layer implements a service
• via its own internal-layer actions
• relying on services provided by layer below

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Distributed implementation of layer functionality
ticket (purchase) baggage (check) gates
(load) runway takeoff airplane routing
ticket (complain) baggage (claim) gates
(unload) runway landing airplane routing
arriving airport
Departing airport
intermediate air traffic sites
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Protocol Stack ISO OSI Model
Header encapsulation and stripping
Data
TH
NH
TH
ISO the International Standards
Organization OSI Open Systems Interconnection
Reference Model (1984)
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Communicating between End Hosts
interface
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Why layering?

• Divide a task into pieces and then solve each
  piece independently (or nearly so).
• Establishing a well defined interface between
  layers makes porting easier.
• Functions of each layer are independent of
  functions of other layers
• Thus each layer is like a module and can be
  developed independently
• Each layer builds on services provided by lower
  layers
• Thus no need to worry about details of lower
  layers -- transparent to this layer
• Major Advantages
• Code Reuse
• Eases maintenance, updating of system

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Programs Processes

• A program is an executable file.
• A process or task is an instance of a program
  that is being executed.
• A single program can generate multiple processes.

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Client - Server

• A server is a process - not a machine !
• A server waits for a request from a client.
• A client is a process that sends a request to an
  existing server and (usually) waits for a reply.

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Client - Server Examples

• Server returns the time-of-day.
• Server returns a document.
• Server prints a file for client.
• Server does a disk read or write.
• Server records a transaction.

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Sample questions

• Difference?
• Subnet, a network, WAN
• Protocols vs. interface

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Assignment Next time

• Reading
• How NOT to go about a programming assignment
• TI Ch.1
• Next Lecture
• OSI model
• Data link layer