Computer NetworksComputer Networks

Dr. Taek Mu Kwon

Department of Electrical and Computer

Engineering

ECE 4321 Computer NetworksECE 4321 Computer Networks

• ECE Technical Elective Course

• 3 Credits

• Network Lab (MWAH 60)

• Network Programming Project (3 – 4)

• Written Exams

• Course Objective: On completion of this course students are expected to learn and understand characteristics of network transmission media, OSI model, TCP/IP, data link protocols, routing algorithms, various LAN technologies, WAN technologies, and network programming.

Computer Center ConceptComputer Center Concept

60’s to mid 80’sA powerful single computer is doing all the

work.Users bring work to the computer instead of

bringing the computer to the user.Expensive hardware cost.

Distributed Computing ConceptDistributed Computing Concept

A large number of separate but interconnected autonomous computers do the job (computer network).

Advantages of Distributed Advantages of Distributed ComputingComputing

Resource sharingHigher reliabilityBetter price/performance ratioBetter communication mediumSpecial server computers for efficient

computing (video server, database server)

Classification of Interconnections by ScaleClassification of Interconnections by Scale

0.1m Circuit Board Dataflow computer

1m System Multiprocessor

10m Room

Local Area Network100m Building

1Km Campus

10Km City Metropolitan Area Network

100Km Country Long haul network (Wide Area Network)

1000Km Continent

10,000Km Planet

Integrated Service Revolution (1990 - )Integrated Service Revolution (1990 - )

1) The fundamental difference between data processing (computer) and data communication (transmission and switching equipment) have blurred. Ex) Half of OS is concerned with computer networks.

2) The fundamental difference among data, voice, and video communication have blurred.

3) The line between single-processor computer, multi-processor computer, local network, metropolitan network, and long-haul network have blurred.

4) WWW became an integration point of all types of communications: data, voice, video.

Communication ModelCommunication Model

Source TransmitterTransmission

SystemReceiver Destination

Information Inputdata

Transmittedsignal

Receivedsignal

Outputdata

OutputInforma-tion

PCModem

Modem

Server

Interface: electrical and procedural connection between each stage from the source to destination

Synchronization: receiver must know a signal when it begins to arrive, when it ends, and the duration of each signal elements.

Exchange Management: For a two party telephone conversation, one party must dial the number of the other. The called party must then lift the receiver and confirm the connection of the intended party.

Error Detection and Correction: ACK, NACK, Telephone– ask repeat

Flow Control: the source should not send data faster than the receiver can process or absorb.

Addressing and Routing

Recovery: File transfer can be interrupted due to a system fault. The objective of recovery is to restore the activity at the point of interruption.

Message Formatting: An agreement between two parties as to the form of the data to be exchanged.

Security: Sender wishes to be assured that only intended parties receive the data or message.

Network Management: To monitor the status or configure the system.

David Clark’s Theory of StandardsDavid Clark’s Theory of Standards

Time

Activit

y

Early proliferation of propriety networksGM net, SABRE, SNA, DNA, ARPA net

Research

Standard

Billion dollarsof investments

Open System Interconnection (OSI) Open System Interconnection (OSI) reference modelreference model

This model is based on a proposal developed by the International Standards Organization (ISO) as a first step towards international standardization of various protocols. The reference model was adopted in 1984 as ISO 7498. It is not an actual working model, but serves as a standard model for classifying communication functions.

International Standards OrganizationInternational Standards Organization

It is a voluntary and non-treaty international organization found in 1946. Its members include national standard organizations of 89 member countries. Examples include ANSI (US), BSI (Great Britain), AFNOR (France), DIN (Germany), … It issues standards on a vast number of subjects from nuts and volts to telecommunication standards.

OSI ModelOSI Model

TCP/IP Protocol ArchitectureTCP/IP Protocol Architecture

TCP/IP architecture is a result of research and development conducted on the experimental packet-switched network, funded by the Defense Advanced Research Project Agency (DARPA). This protocol suite consists of a large collection of protocols that have been issued as Internet standards by the Internet Architecture Board (IAB).

Internet StandardsInternet Standards

IAB

Internet Architecture Board (IAB) issues standards by publishing a series of documents called Request for Comments.

Internet EngineeringTask Force (IETF)

Internet ResearchTask Force (IRTF)

TCP/IP Protocol SuiteTCP/IP Protocol Suite

TCP/IP CommunicationTCP/IP Communication

InternetInternet

IPv4 AddressIPv4 Address

IPv6 IPv6

128 bit address: Allow 6x1023 unique addresses per square meter of surface of the earth.

Address Auto-configurationImproved Option MechanismSupport Different Types of Traffic Flow