Transcript Topics discussed in this section
네트워크와데이타통신
2013. 09. 09.
멀티미디어공학전공 이 우 섭
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Chapter 1 Introduction
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1-1 DATA COMMUNICATIONS
The term telecommunication a distance.
means communication at The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data.
Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable.
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Figure 1.1
Five components of data communication
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Figure 1.2
Data flow (simplex, half-duplex, and full-duplex)
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1-2 NETWORKS
A network is a set of devices (often referred to as nodes ) connected by communication links .
A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.
Topics discussed in this section:
Distributed Processing Network Criteria Physical Structures Network Models Categories of Networks Interconnection of Networks: Internetwork
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Figure 1.3
Types of connections: point-to-point and multipoint
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Figure 1.4
Categories of topology
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Figure 1.5
A fully connected mesh topology (five devices)
특징 장점 단점 N 개의 장치 연결을 위해 / 2 개의 물리적 채널이 필요 n (n-1) 모든 장치는 필요 n-1 개의 I/O 포트가 전용 링크 사용으로 자료 전송 보장 안정성이 높다 비밀 유지와 보안 설치와 재구성이 어렵다 설치 공간과 비용이 많이 든다 .
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Figure 1.6
A star topology connecting four stations
10 특징 장점 단점 각 장치는 허브 (Hub) 라는 중앙 제어 장치와 전용 점대점 링크를 갖는다 .
각 장치간 직접적인 통신은 할 수 없으며 제어장치가 교환 역할 수행 1 개의 링크와 필요 ( 1 개의 I/O 비용이 적게 든다 ) 포트만 설치와 재구성이 쉽다 .
안정성 중앙 제어 장치 (Hub) 의 고장은 전체 망에 영향을 준다 .
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Figure 1.7
A bus topology connecting three stations
특징 장점 단점 점대다중점 형태 , 노드는 Tab 과 Drop line 으로 버스에 연결 버스가 수용할 수 있는 tab 의 수와 tab 간 간격은 제한됨 .
설치하기 쉽다 .
재구성이나 결함 분리가 어렵다 . ( 버스 케이블의 결함은 모든 전 송이 중단됨 ) 11 Multimedia Engineering Dept.
Figure 1.8
A ring topology connecting six stations
특징 장점 단점 각 장치는 자신의 양쪽에 있는 장치와 점대점 회선 구성 신호는 한 방향으로만 링을 따라 목적지에 도달 각 장치는 중계기 기능을 포함 설치와 재구성이 쉽다 . ( 송신매체와 통신량에 고려 필요 ) 결함 분리가 쉽다 .
단방향 전송 링의 결함은 전체 네트워크 사용 불가능 12 Multimedia Engineering Dept.
Figure 1.9
A hybrid topology: a star backbone with three bus networks
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Figure 1.10
An isolated LAN connecting 12 computers to a hub in a closet
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LAN (Local Area Network) :
– Office, building or campus ( 수 Km 로 제한 ) – 개인 PC 나 Workstation 의 자원 공유가 목적 ( 프린터 , 응용 프로그램 , 데이터 등 ) 14 Multimedia Engineering Dept.
MAN
◈
MAN (Metropolitan Area Network) :
– Expand network to the whole city (Metro Ethernet) 15 Multimedia Engineering Dept.
Figure 1.11
WANs: a switched WAN and a point-to-point WAN
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Figure 1.12
A heterogeneous network made of four WANs and two LANs
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1-3 THE INTERNET
The Internet has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the way we spend our leisure time.
The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use.
Topics discussed in this section:
A Brief History The Internet Today (ISPs)
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인터넷 발전과정
1969 1979 1983 1986 1989 1990 1991 1993 1994 1995 미국방성 프로젝트의 일환으로 ARPANET 개발 TCP/IP 프로토콜 개발완료 TCP/IP 가 ARPANET ARPANET 이 연구용 등 인터넷의 통신 표준안으로 채택 ARPANET 과 군사용 MILNET 으로 분리 미 과학재단에서 NSFNET 구축 , 인터넷 백본 스위스 입자물리연구소 CERN 에서 WWW 기술 개발 착수 ARPANET 해체 , 주된 기능을 NSFNET 으로 이전 , URL, HTTP, HTML WWW 개발완료 , CERN 에 WWW 설치 Mosaic 개발 Netscape 개발 NSFNET 은 연구망 운용을 전담하고 , 일반 인터넷은 상업용 통신망사업 자가 주관하여 운용하기 시작함 Multimedia Engineering Dept.
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한국의 초고속 인터넷 현황 ▣ 대한민국의 초고속 통신망 역사 ◈ ◈ ◈ ◈ ◈ 1996. 6. 두루넷 케이블 모뎀 개시 1998. 10. 하나로 통신 케이블 모뎀 개시 1999. 4. 하나로 통신 세계 최초 ADSL 서비스 개시 1999. 6. 한국 통신 ADSL 서비스 개시 2000. 12. 초고속 정보 통신망 2 단계 사업 완료 (144 개 지역에 광전송 및 ATM 기반의 초고속 국가망 구축 ) ◈ ◈ ◈ 2001. 6. 초고속 정보 통신망 3 단계 고도화 계획 수립 2002. 4. e-Korea Vision 2006 수립 2002. 10. 초고속 가입자 수 1000 만 돌파 ◈ ◈ 2003. 3. 하나로 , KT VDSL 서비스 개시 2005 년부터 LG 파워컴에서 FTTH 서비스 시작 ◈ 2013 년 현재 기가 이더넷을 이용한 FTTH 일반화 – 2006 년 6 월 기준으로 한국의 100 명당 초고속인터넷 가입자는 크 (29.3
명 ), 네덜란드 (28.8
명 ), 아이슬란드 (27.3
명 ) 에 이어 는 스위스 (26.2
명 ) 로 조사됐다 . 4 26.4
명으로 , 덴마 위를 기록했다 . 5 위 20 Multimedia Engineering Dept.
Figure 1.13
Hierarchical organization of the Internet
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1-4 PROTOCOLS AND STANDARDS
In this section, we define two widely used terms: protocols and standards . First, we define protocol, which is synonymous with rule. Then we discuss standards, which are agreed-upon rules.
Topics discussed in this section:
Protocols Standards Standards Organizations Internet Standards
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프로토콜과 표준 ▣
Standard
◈ 국내 및 국제간 데이터 및 전기통신 기술의 상호연동성을 보장 ◈ 사실 표준 , 법률 표준 ▣ 표준 기구 ◈ 표준제정위원회 (Standard Creation Committee) – ISO( 국제표준기구 ), ITU( 국제전기통신연합 ), ANSI( 미국 국립표준협회 ), IEEE( 전지전자공학자협회 ) ◈ 협의회 (Forum) – IETF(The Internet Engineering Task Force, www.ietf.org) Multimedia Engineering Dept.
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Chapter 2 Network Models
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2-1 LAYERED TASKS
We use the concept of layers in our daily life. As an example, let us consider two friends who communicate through postal mail. The process of sending a letter to a friend would be complex if there were no services available from the post office.
Topics discussed in this section:
Sender, Receiver, and Carrier Hierarchy
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Figure 2.1 Tasks involved in sending a letter
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2-2 THE OSI MODEL
Established in 1947, the International Standards Organization ( ISO ) is a multinational body dedicated to worldwide agreement on international standards.
An ISO standard that covers all aspects of network communications is the Open Systems Interconnection ( OSI ) model.
It was first introduced in the late 1970s.
Topics discussed in this section:
Layered Architecture Peer-to-Peer Processes Encapsulation
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Figure 2.2
Seven layers of the OSI model
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Figure 2.3
The interaction between layers in the OSI model
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Figure 2.4
An exchange using the OSI model
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2-3 LAYERS IN THE OSI MODEL
In this section we briefly describe the functions of each layer in the OSI model.
Topics discussed in this section:
Physical Layer Data Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer
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Figure 2.5
Physical layer
The physical layer is responsible for movements of individual bits from one hop (node) to the next.
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Figure 2.6
Data link layer
The data link layer is responsible for moving frames from one hop (node) to the next.
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Figure 2.7
Hop-to-hop delivery
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Figure 2.8
Network layer
The network layer is responsible for the delivery of individual packets from the source host to the destination host.
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Figure 2.9
Source-to-destination delivery
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Figure 2.10
Transport layer
The transport layer is responsible for the delivery of a message from one process to another.
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Figure 2.11
Reliable process-to-process delivery of a message
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Figure 2.14
Application layer
The application layer is responsible for providing services to the user.
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Figure 2.15
Summary of layers
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2-4 TCP/IP PROTOCOL SUITE
The layers in the TCP/IP protocol suite do not exactly match those in the OSI model.
The original TCP/IP protocol suite was defined as having four layers: host-to-network, internet, transport , and application .
However, when TCP/IP is compared to OSI, we can say that the TCP/IP protocol suite is made of five layers: physical, data link, network, transport, and application.
Topics discussed in this section:
Physical and Data Link Layers Network Layer Transport Layer Application Layer
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Figure 2.16
TCP/IP and OSI model
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2-5 ADDRESSING
Four levels of addresses are used in an internet employing the TCP/IP protocols: physical, logical, port, and specific.
Topics discussed in this section:
Physical Addresses Logical Addresses Port Addresses Specific Addresses
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Figure 2.17
Addresses in TCP/IP
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Figure 2.18
Relationship of layers and addresses in TCP/IP
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Example 2.1
In Figure 2.19 a node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by a link (bus topology LAN). As the figure shows, the computer with physical address the sender, and the computer with physical address 10 87 the receiver.
is is
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Figure 2.19
Physical addresses
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Example 2.2
Most local-area networks use a below: 48-bit (6-byte) physical address written as 12 hexadecimal digits; every byte (2 hexadecimal digits) is separated by a colon, as shown
07:01:02:01:2C:4B
A 6-byte (12 hexadecimal digits) physical address.
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Example 2.3
Figure 2.20 shows a part of an internet with two routers connecting three LANs.
Each device (computer or router) has a pair of addresses (logical and physical) for each connection.
In this case, each computer is connected to only one link and therefore has only one pair of addresses.
Each router, however, is connected to three networks (only two are shown in the figure). So each router has three pairs of addresses, one for each connection.
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Figure 2.20
IP addresses
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