1. 1 Kyung Hee University Prof. Choong Seon HONG Introduction

2. 2 Kyung Hee University 1.1 Data Communication  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)

3. 3 Kyung Hee University Fundamental Characteristics ( 기본 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

4. 4 Kyung Hee University Data communication system components step 1: step 2: step 3: ……. 송신자 수신자 전송매체 step 1: step 2: step 3: ……. 프로토콜 메시지

5. 5 Kyung Hee University 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)

6. 6 Kyung Hee University 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.

7. 7 Kyung Hee University 1.2 네트워크 (Networks) ~ is a set of devices(node) connected by media links.  장치 (Device) - computer, printer, any other device capable of sending and/or receiving data generated by other nodes on the network.  링크 (Link) - communication channel

8. 8 Kyung Hee University 분산처리 (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.

9. 9 Kyung Hee University 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 alone. 4. Security through redundancy - Multiple computers running the same program at the same time can 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)

10. 10 Kyung Hee University 네트워크 평가기준 (Network Criteria) Performance Reliability Security Data communication network criteria Data communication network criteria

11. 11 Kyung Hee University Performance ( 성능 )  Depends on a number of factors. number of users type of transmission medium(data rate) hardware software : error-free delivery

12. 12 Kyung Hee University Reliability ( 신뢰성 )  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.

13. 13 Kyung Hee University 보안 (Security)  Unauthorized access  Viruses and Worms

14. 14 Kyung Hee University 네트워크 응용 (Applications)  Marketing and sales  Financial service  Manufacturing  Electronic message  Directory service  Information service  Electronic data interchange  Teleconferencing  Cellular telephone  Cable television

15. 15 Kyung Hee University 1.3 프로토콜과 표준 (Protocol & Standards)  프로토콜 (Protocol) ~ is a set of rules that govern data communication  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)

16. 16 Kyung Hee University Standards  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. Standards De facto (by fact) De facto (by fact) De jure (by law) De jure (by law)

17. 17 Kyung Hee University 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.

18. 18 Kyung Hee University Standards Organizations ( 표준화 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)

19. 19 Kyung Hee University 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. l 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)

20. 20 Kyung Hee University Standards Organizations (cont’d) 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)

21. 21 Kyung Hee University Standards Organizations (cont’d) Bellcore (now, Telcordia Technologies) ~ provides research and development resources for the advancement of telecommunications technology. Forums ~ consist of representatives from corporation that test, evaluate and standardize new technologies. l Frame Relay Forum l ATM Forum and ATM consortium l IETF(Internet Society and Internet Engineering Task Force) l TINA (Telecommunications Information Networking Architecture)  Regulatory agencies FCC

22. 22 Kyung Hee University Standards Organizations (cont’d)  한국정보통신기술협회 (TTA) 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

23. 23 Kyung Hee University Standards Organizations (cont’d)  한국산업표준원 (KISI) 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

24. 24 Kyung Hee University Standards Organizations (cont’d)  한국전자통신연구소 표준연구센터 http://pec.etri.re.kr 1989 년 ETRI 내 설립 초고속 정보통신 기반을 위한 표준 / 규격 / 기준 관련 기술의 연구 개발 주도 정보통신 산업체 중심의 표준화 활동 기반 조성 핵심 표준 기술의 산업체 이전 및 제공 국내 표준 활동 강화를 통한정보통신 시장의 균형적인 발전 및 활성화

25. 25 Kyung Hee University Standards Organizations (cont’d)  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