Computer Networks Dr. Taek Mu Kwon Department of Electrical and Computer Engineering

ECE 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 Concept 60’s to mid 80’s A 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 Concept A large number of separate but interconnected autonomous computers do the job (computer network).

Advantages of Distributed Computing Resource sharing Higher reliability Better price/performance ratio Better communication medium Special server computers for efficient computing (video server, database server)

Classification of Interconnections by Scale 0.1m Circuit BoardDataflow computer 1m SystemMultiprocessor 10m Room Local Area Network 100m Building 1Km Campus 10Km CityMetropolitan Area Network 100Km CountryLong haul network (Wide Area Network) 1000Km Continent 10,000Km Planet

Integrated Service Revolution ( ) 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 Model Source Transmitter Transmission System ReceiverDestination Information Input data Transmitted signal Received signal Output data Output Informa- tion PC 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 Standards Time Activity Early proliferation of propriety networks GM net, SABRE, SNA, DNA, ARPA net Research Standard Billion dollars of investments

Open System Interconnection (OSI) reference 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 It is not an actual working model, but serves as a standard model for classifying communication functions.

International Standards Organization It is a voluntary and non-treaty international organization found in 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 Model

TCP/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 Standards IAB Internet Architecture Board (IAB) issues standards by publishing a series of documents called Request for Comments. Internet Engineering Task Force (IETF) Internet Research Task Force (IRTF)

TCP/IP Protocol Suite

TCP/IP Communication

Internet

IPv4 Address

IPv6 128 bit address: Allow 6x10 23 unique addresses per square meter of surface of the earth. Address Auto-configuration Improved Option Mechanism Support Different Types of Traffic Flow