1 Kyung Hee University Computer Network. 2 Kyung Hee University Part 1 : 데이터 통신과 네트워킹 개요

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Kyung Hee University

Computer NetworkComputer Network

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Part 1 : Part 1 : 데이터 통신과 네트워킹 개요데이터 통신과 네트워킹 개요

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Chapter 1. Introduction (Chapter 1. Introduction ( 서론서론 ))

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1.1 Data Communications1.1 Data Communications

Data communication is the process of communicating

information of binary form between two or more points.

Data communication is the exchange of data (in the

form of 0s and 1s) between two devices via some form

of transmission medium(such as a wire cable)

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Fundamental Characteristics (Fundamental Characteristics ( 기본 특성기본 특성 ))

The effectiveness of a data communication system depends on

three fundamental characteristics

전달 (Delivery)

~ must deliver data to the correct destination (the intended

device or user)

정확성 (Accuracy)

~ must deliver data accurately

적시성 (Timeliness)

~ must deliver data in a timely manner

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Data communication system componentsData communication system components

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Data communication system components (cont’d)Data communication system components (cont’d)

메시지 (Message)

~ is the information(data) to be communicated.

(text, numbers, pictures, sound, video or any combination of these)

송신자 (Sender)

~ is the device that sends the data message.

(computer, workstation, telephone handset, video camera)

수신자 (Receiver)

~ is the device that receives the message.

(computer, workstation, telephone handset, video camera)

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Data communication system components (cont’d)Data communication system components (cont’d)

전송매체 (Medium)

~ is the physically path by which a message travels from sender

to receiver.

(twisted pair wire, coaxial cable, fiber- optic cable, laser , or

radio waves(terrestrial or satellite microwave))

프로토콜 (Protocol)

~ is a set of rules that govern data communication.

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Data PresentationData Presentation

Text

ASCII : by ANSI, 7bits

Extended ASCII, 8bits

Unicode : 16 bits

ISO : 32bits

Numbers : see Appendix B

Images

Audio : continuous

Video

1010


Direction of Data FlowDirection of Data Flow

~ is used to define the direction of signal flow between two link devic

es

단방향 (Simplex)

is unidirectional, as on a one-way street (keyboard, monitor)

반이중 (Half-Duplex)

each station can both transmit and receive, but not at the same

time

전이중 (Full-Duplex)

both stations can transmit and receive simultaneously

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Simplex

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Half-Duplex

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Full-Duplex

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1.2 1.2 네트워크네트워크 (Networks)(Networks)

~ is a set of devices(nodes) connected by media links.

장치 (Device or Node)

- computer, printer, any other device capable of sending and/or receivin

g data generated by other nodes on the network.

링크 (Link)

- communication channel

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분산처리분산처리 (Distributed processing)(Distributed processing)

In which a task is divided among multiple computers.

Advantage

1. Security/encapsulation

- A system designer can limit the kinds of interactions that a

given user can have with the entire system. For example, ATM

(Automated Teller Machine)

2. Distributed databases

- No one system needs to provide storage capacity for the

entire database.

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Distributed processing (cont’d)Distributed processing (cont’d)

3. Faster problem solving

- Multiple computers working on parts of a problem concurrently can

often solve the problem faster than a single machine working alon

e.

4. Security through redundancy

- Multiple computers running the same program at the same time ca

n provide security through redundancy (ex: space shuttle)

5. Collaborative processing

- Both multiple computers and multiple users may interact on a task

(ex: multiuser network games)

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네트워크 평가기준네트워크 평가기준 (Network Criteria)(Network Criteria)

PerformancePerformance ReliabilityReliability SecuritySecurity

Data communicationnetwork criteria

Data communicationnetwork criteria

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Performance (Performance ( 성능성능 ))

Depends on a number of factors.

number of users

type of transmission medium(data rate)

hardware

software : error-free delivery

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Reliability (Reliability ( 신뢰성신뢰성 ))

Frequency of failure

Recovery time of a network after a failure

Catastrophe

Networks must be protected from catastrophic events such as fire,

earthquake, or theft.

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보안 보안 (Security)(Security)

Unauthorized access

Viruses and Worms

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Physical StructuresPhysical Structures

Type of Network Connection

점 - 대 - 점 (Point-to-point)

~ provides a dedicated link between two devices.

다중 점 (Multipoint) : multidrop

~ is configuration in which more than two specific devices share a single link

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Type of Network ConnectionType of Network Connection

point-to-point

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Type of Network ConnectionType of Network Connection

Multipoint

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Physical TopologyPhysical Topology

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Mesh

Every device has a dedicated point-to-point link to every other device.

A fully connected mesh network therefore has n(n-1)/2 physical channels to link n devices.

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Mesh

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Mesh (cont’d)Mesh (cont’d)

Advantages

The use of dedicated links guarantees that each

connection can carry its data load.

Mesh topology is robust.

Privacy and security.

Point-to-point links make fault identification and fault

isolation easy.

2828


그물형 그물형 (cont’d)(cont’d)

Disadvantages

~ are related to the amount of cabling and the number of I/O ports

because every device must be connected to every other device, installation and reconfiguration are difficult

the sheer bulk of the wiring can be greater than the available space(in walls, ceiling, or floors) can accommodate

the hardware required to connect each link (I/O port and cable) can be prohibitively expensive

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스타형 스타형 (Star (Star : : 성형성형 ))

Each device has a dedicated point-to-point link only to

a central controller, usually called a hub

스타형 (Star : 성형 )

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Star (cont’d)Star (cont’d)

Advantage

Each device needs only one link and one I/O port to

connect it to any number of others (easy to install

and reconfigure)

Robustness

if one link fails, only that link is affected

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트리형 트리형 (Tree)(Tree)

is a variation of a star

active hub(central hub)

~ contains a repeater, which is a hardware device

that generates the received bit patterns before

sending them out

passive hub

~ provides a simple physical connection between

the attached devices

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버스형 버스형 (Bus)(Bus)

is multipoint. One long cable acts as a backbone to link

all the devices in the network

Nodes are connected to the bus cable by drop lines and

taps

drop line

~ is a connection running between the device and the main

cable

tap

~ is a connector either splices into the main cable or

punctures the sheathing of a cable to create a contact with

the metallic core

3333


Bus Bus 형형

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Bus (cont’d)Bus (cont’d)

AdvantagesAdvantages

~ include ease of installation

DisadvantagesDisadvantages

~ include difficult reconfiguration and fault isolation

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링형 링형 (Ring)(Ring)

Each device has a dedicated point-to-point line configuration only

with the two devices on either side of it

AdvantageAdvantage

~ is relatively easy to install and reconfigure

~ fault isolation is simplified

DisadvantageDisadvantage

unidirectional traffic

break in the ring can disable the entire network

--> needs dual ring

3636


네트워크 분류 네트워크 분류 (Categories of Networks)(Categories of Networks)

three primary categories

근거리 통신망 (LAN)

도시 통신망 (MAN)

광역 통신망 (WAN)

size, ownership, distance it cover, physical architecture

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Categories of Networks (cont’d)Categories of Networks (cont’d)

Metropolitan area network(MAN)

Metropolitan area network(MAN)

Local area networks(LAN)

Local area networks(LAN)

Wide area network(WAN)

Wide area network(WAN)

NetworkNetwork

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LAN(Local Area Networks)

~ is usually privately owned and links the devices in a single office, building or campus

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MAN(Metropolitan Area Networks)

~ is designed to extend over an entire city

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WAN(Wide Area networks)

~ provides long-distance transmission of data, voice, image, and video information over large geographical areas that may comprise a country, a continent, or even the whole world

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WAN

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1.3 Internet1.3 Internet

A Brief History

Internet (not internet)

ARPANET (Advanced Research Projects Agency: ARPA) – mid-1960s

Advanced Research Projects Agency (ARPA) in the DOD : presented ideas of ARPANET, 1967

Reality : 1969 (UCLA, UCSB, SRI, U of Utah)

Birth of Internet : in 1972

Vint Cerf and Bob Kahn : Internetting Project

TCP/IP : A paper by Cerf and Kahn in 1973

In 1983, TCP/IP became to official protocol for the ARPANET

MILNET : in 1983

CSNET, NSFNET, ANSNET, …

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Internet TodayInternet Today 1969. Four-node ARPANET established.

1970. ARPA hosts implement NCP.

1973. Development of TCP/IP suite begins.

1977. An internet tested using TCP/IP.

1978. UNIX distributed to academic sites.

1983. TCP/IP becomes the official protocol

1983. MILNET was born.

1986. NSFNET established.

1990. ARPANET replaced by NSFNET.

1991. WWW by CERNWWW by CERN

1995. NSFNET became a research network.

1995. ISPs started.

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Internet TodayInternet Today

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1.4 Protocols and Standard1.4 Protocols and Standard

Communication in computer networks

~ occurs between entities in different systems

Entity

~ is anything capable of sending or receiving information

프로토콜 (Protocol)

~ is a set of rules that govern data communication

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Protocol & Standards (cont’d)Protocol & Standards (cont’d)

Protocol 의 주요 요소

문법 (Syntax)

~ refers to the structure or format of the data, meaning the order in which they are presented.

의미론 (Semantics)

~ refers to the meaning of each section of bits.

타이밍 (Timing)

~ refers to two characteristics (when data should be sent and how fast it can be sent)

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StandardsStandards

표준안 (Standards)

~ are essential in creating and maintaining an open and competitive market for equipment manufactures and in guaranteeing national and international interoperability of data and communications technology and processes.

StandardsStandards

De facto(by fact)

De facto(by fact)

De jure(by law)

De jure(by law)

4949


Standards Organizations (Standards Organizations ( 표준화 기구표준화 기구 ))

Standard Creation Committees

ISO (The International Standard Organization)

~ created in 1947

~ voluntary organization

~ is an organization dedicated to worldwide agreement on

international standards in a variety of fields (scientific,

technological, economic activity)

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Standards Organizations (cont’d)Standards Organizations (cont’d)

ITU-T(International Telecommunications Union -

Telecommunications Standards Sector)

~ is an international standards organization related to the

United Nations that develops standards for

telecommunications.

Two popular standards developed by ITU-T are the V series

(data transmission over phone lines) and the X series

(transmission over public digital networks)

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ANSI (American National Standard Institute)

~ is a nonprofit organization and is the U.S. voting representative to be both the ISO and the ITU-T

IEEE (Institute of Electrical and Electronic Engineers)

~ is the largest national professional group involved in developing standards for computing, communication, electrical engineering, and electronics)

EIA (Electronic Industries Association)

~ is an association of electronics manufactures in the United States. (EIA-232-D, EIA-530 standards)

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Forums

~ consist of representatives from corporation that test,

evaluate and standardize new technologies.

Frame Relay Forum

ATM Forum and ATM consortium

Regulatory agencies

FCC (Federal Communications Commission)

MIC (Ministry of Communication)

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Internet StandardsInternet Standards

Internet standard

is a thoroughly tested specification that is useful to and adhered by those who work with the Internet

A specification begins as an Internet draft

Working document with no official status and six-month life-time

RFC (Request for Comment)

Recommendation from Internet authorities

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Standards (cont’d)Standards (cont’d) by law standard

~ are those that have been legislated by an officially recognized body.

by fact standard

~ are often established originally by manufactures seeking to define the

functionality of a new product or technology.

proprietary(closed)

~ are those originally invented by a commercial organization as a

basis for the operation of its products.

nonproprietary(open)

~ are those originally developed by group or committees that have

passed them into the public domain.

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Standards Organizations (Standards Organizations ( 표준화 기구표준화 기구 ))

Standard Creation Committees

ISO (The International Standard Organization)

~ created in 1947

~ voluntary organization

~ is an organization dedicated to worldwide agreement on

international standards in a variety of fields (scientific,

technological, economic activity)

5656



ITU-T(International Telecommunications Union -

Telecommunications Standards Sector)

~ is an international standards organization related to the

United Nations that develops standards for

telecommunications.

Two popular standards developed by ITU-T are the V

series(data transmission over phone lines) and the X series

(transmission over public digital networks)

5757



ANSI (American National Standard Institute)

~ is a nonprofit organization and is the U.S. voting representative to be both the ISO and the ITU-T

IEEE (Institute of Electrical and Electronic Engineers)

~ is the largest national professional group involved in developing standards for computing, communication, electrical engineering, and electronics)

EIA (Electronic Industries Association)

~ is an association of electronics manufactures in the United States. (EIA-232-D, EIA-530 standards)

5858


Standards Organizations (cont’d)Standards Organizations (cont’d)Bellcore (now, Telcordia Technologies)

~ provides research and development resources for the adva

ncement of telecommunications technology.

Forums

~ consist of representatives from corporation that test, evalu

ate and standardize new technologies.

Frame Relay Forum

ATM Forum and ATM consortium

IETF(Internet Society and Internet Engineering Task Force)

TINA (Telecommunications Information Networking Architecture)

Regulatory agencies

FCC (Federal Communications Commission)

5959



한국정보통신기술협회 (TTA) : 정보통신부관련

http://www.tta.or.kr

1988 년 12 월 설립

통신 사업자 , 산업체 , 학계 , 연구기관 및 단체 등의 상호 협력과 유대 강화

국내외 정보통신분야의 최신기술 및 표준에 관한 각종 정보 수집 , 조사 연구 및 보급•활용

정보통신 산업 및 기술 진흥과 국민 경제 발전에 기여

6060



한국산업표준원 (KISI) : 산업자원부 관련

http://www.kisi.or.kr

산업표준 연구 개발

표준화 국제 협력 및 진흥

북한 표준 연구

정보산업 표준화

자본재 표준화

KSSN( 한국 표준 정보망 ) 운영

6161



한국전자거래진흥원 (KEB)

http://www.keb.or.kr

Korea EDI/EC Board

한국 표준 전자문서 (KEDIfact) 제정 , 고시

세계 전자문서 표준인 UN/EDIFACT 보급과 제정 활동 참여

전자 거래 실현에 필요한 표준 연구 개발

Documents

1 Kyung Hee University Computer Network. 2 Kyung Hee University Part 1 : 데이터 통신과 네트워킹 개요