Multimedia Engineering Dept. 1 2013. 09. 09. 멀티미디어공학전공 이 우 섭 네트워크와데이타통신

Multimedia Engineering Dept.

1

2013. 09. 09.

멀티미디어공학전공

이 우 섭

네트워크와데이타통신


2

Chapter 1

Introduction


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1-1 DATA COMMUNICATIONS1-1 DATA COMMUNICATIONS

The term The term telecommunicationtelecommunication means communication at means communication at a distance. a distance. The word The word datadata refers to information presented in refers to information presented in whatever form is agreed upon by the parties creating whatever form is agreed upon by the parties creating and using the data. and using the data. Data communicationsData communications are the exchange of data are the exchange of data between two devices via some form of transmission between two devices via some form of transmission medium such as a wire cable. 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 NETWORKS1-2 NETWORKS

A A networknetwork is a set of devices (often referred to as is a set of devices (often referred to as nodesnodes) connected by communication ) connected by communication linkslinks. . A node can be a computer, printer, or any other device A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by capable of sending and/or receiving data generated by other nodes on the network.other nodes on the network.

Distributed ProcessingNetwork CriteriaPhysical StructuresNetwork ModelsCategories of NetworksInterconnection of Networks: Internetwork

Topics discussed in this section:Topics discussed in this section:


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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

- N 개의 장치 연결을 위해 n (n-1) / 2 개의 물리적 채널이 필요- 모든 장치는 n-1 개의 I/O 포트가 필요

장점

- 전용 링크 사용으로 자료 전송 보장- 안정성이 높다- 비밀 유지와 보안

단점- 설치와 재구성이 어렵다- 설치 공간과 비용이 많이 든다 .


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Figure 1.6 A star topology connecting four stations

특징

- 각 장치는 허브 (Hub) 라는 중앙제어 장치와 전용 점대점 링크를 갖는다 .

- 각 장치간 직접적인 통신은 할 수 없으며 제어장치가 교환 역할 수행

장점

- 1 개의 링크와 1 개의 I/O 포트만 필요 ( 비용이 적게 든다 )

- 설치와 재구성이 쉽다 .

- 안정성

단점- 중앙 제어 장치 (Hub) 의 고장은 전체 망에 영향을 준다 .


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Figure 1.7 A bus topology connecting three stations

특징- 점대다중점 형태 , 노드는 Tab 과 Drop line 으로 버스에 연결- 버스가 수용할 수 있는 tab 의 수와 tab 간 간격은 제한됨 .

장점 - 설치하기 쉽다 .

단점- 재구성이나 결함 분리가 어렵다 . ( 버스 케이블의 결함은 모든 전송이 중단됨 )


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Figure 1.8 A ring topology connecting six stations

특징- 각 장치는 자신의 양쪽에 있는 장치와 점대점 회선 구성-신호는 한 방향으로만 링을 따라 목적지에 도달- 각 장치는 중계기 기능을 포함

장점- 설치와 재구성이 쉽다 . ( 송신매체와 통신량에 고려 필요 )

- 결함 분리가 쉽다 .

단점- 단방향 전송- 링의 결함은 전체 네트워크 사용 불가능


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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

◈ 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 )


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◈ MAN (Metropolitan Area Network) : – Expand network to the whole city (Metro Ethernet)

MAN


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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 INTERNET1-3 THE INTERNET

The The InternetInternet has revolutionized many aspects of our has revolutionized many aspects of our daily lives. It has affected the way we do business as daily lives. It has affected the way we do business as well as the way we spend our leisure time. well as the way we spend our leisure time. The Internet is a communication system that has The Internet is a communication system that has brought a wealth of information to our fingertips and brought a wealth of information to our fingertips and organized it for our use. organized it for our use.

A Brief HistoryThe Internet Today (ISPs)



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인터넷 발전과정

1969 미국방성 프로젝트의 일환으로 ARPANET 개발

1979 TCP/IP 프로토콜 개발완료

1983 TCP/IP 가 ARPANET 등 인터넷의 통신 표준안으로 채택 ARPANET 이 연구용 ARPANET 과 군사용 MILNET 으로 분리

1986 미 과학재단에서 NSFNET 구축 , 인터넷 백본

1989 스위스 입자물리연구소 CERN 에서 WWW 기술 개발 착수

1990 ARPANET 해체 , 주된 기능을 NSFNET 으로 이전 , URL, HTTP, HTML

1991 WWW 개발완료 , CERN 에 WWW 설치

1993 Mosaic 개발

1994 Netscape 개발

1995 NSFNET 은 연구망 운용을 전담하고 , 일반 인터넷은 상업용 통신망사업자가 주관하여 운용하기 시작함


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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 26.4 명으로 , 덴마크 (29.3 명 ), 네덜란드 (28.8 명 ), 아이슬란드 (27.3 명 ) 에 이어 4 위를 기록했다 . 5 위는 스위스 (26.2 명 ) 로 조사됐다 .


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Figure 1.13 Hierarchical organization of the Internet


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1-4 PROTOCOLS AND STANDARDS1-4 PROTOCOLS AND STANDARDS

In this section, we define two widely used terms: In this section, we define two widely used terms: protocolsprotocols and and standardsstandards. First, we define protocol, . First, we define protocol, which is synonymous with rule. Then we discuss which is synonymous with rule. Then we discuss standards, which are agreed-upon rules.standards, which are agreed-upon rules.

ProtocolsStandardsStandards OrganizationsInternet Standards



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▣ 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)

프로토콜과 표준


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Chapter 2

Network Models


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2-1 LAYERED TASKS2-1 LAYERED TASKS

We use the concept of We use the concept of layerslayers in our daily life. As an in our daily life. As an example, let us consider two friends who communicate example, let us consider two friends who communicate through postal mail. The process of sending a letter to a through postal mail. The process of sending a letter to a friend would be complex if there were no services friend would be complex if there were no services available from the post office. available from the post office.

Sender, Receiver, and CarrierHierarchy



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Figure 2.1 Tasks involved in sending a letter


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2-2 THE OSI MODEL2-2 THE OSI MODEL

Established in 1947, the International Standards Established in 1947, the International Standards Organization (Organization (ISOISO) is a multinational body dedicated to ) is a multinational body dedicated to worldwide agreement on international standards. worldwide agreement on international standards. An ISO standard that covers all aspects of network An ISO standard that covers all aspects of network communications is the Open Systems Interconnection communications is the Open Systems Interconnection ((OSIOSI) model. ) model. It was first introduced in the late 1970s. It was first introduced in the late 1970s.

Layered ArchitecturePeer-to-Peer ProcessesEncapsulation



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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 MODEL2-3 LAYERS IN THE OSI MODEL

In this section we briefly describe the functions of each In this section we briefly describe the functions of each layer in the OSI model.layer in the OSI model.

Physical LayerData Link LayerNetwork LayerTransport LayerSession LayerPresentation LayerApplication Layer



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Figure 2.5 Physical layer

The physical layer is responsible for movements ofindividual 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 SUITE2-4 TCP/IP PROTOCOL SUITE

The layers in the The layers in the TCP/IP protocol suiteTCP/IP protocol suite do not exactly match those do not exactly match those in the OSI model. in the OSI model. The original TCP/IP protocol suite was defined as having four The original TCP/IP protocol suite was defined as having four layers: layers: host-to-network, internet, transporthost-to-network, internet, transport, and , and applicationapplication. . However, when TCP/IP is compared to OSI, we can say that the However, when TCP/IP is compared to OSI, we can say that the TCP/IP protocol suite is made of five layers: TCP/IP protocol suite is made of five layers: physical, data link, physical, data link, network, transport, and application.network, transport, and application.

Physical and Data Link LayersNetwork LayerTransport LayerApplication Layer



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Figure 2.16 TCP/IP and OSI model


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2-5 ADDRESSING2-5 ADDRESSING

Four levels of addresses are used in an internet Four levels of addresses are used in an internet employing the TCP/IP protocols: employing the TCP/IP protocols: physical, logical, port, physical, logical, port, and specific.and specific.

Physical AddressesLogical AddressesPort AddressesSpecific 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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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 10 is the sender, and the computer with physical address 87 is the receiver.

Example 2.1


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Figure 2.19 Physical addresses


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Most local-area networks use a 48-bit (6-byte) physical address written as 12 hexadecimal digits; every byte (2 hexadecimal digits) is separated by a colon, as shown below:

Example 2.2

07:01:02:01:2C:4B

A 6-byte (12 hexadecimal digits) physical address.


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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.

Example 2.3


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Figure 2.20 IP addresses

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Multimedia Engineering Dept. 1 2013. 09. 09. 멀티미디어공학전공 이 우 섭 네트워크와데이타통신