네트워크와데이타통신
2013. 09. 09.
멀티미디어공학전공
이우섭
1
Multimedia Engineering Dept.
Chapter 1
Introduction
2
Multimedia Engineering Dept.
1-1 DATA COMMUNICATIONS
The term telecommunication means communication at
a distance.
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.
3
Multimedia Engineering Dept.
Figure 1.1 Five components of data communication
4
Multimedia Engineering Dept.
Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)
5
Multimedia Engineering Dept.
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
6
Multimedia Engineering Dept.
Figure 1.3 Types of connections: point-to-point and multipoint
7
Multimedia Engineering Dept.
Figure 1.4 Categories of topology
8
Multimedia Engineering Dept.
Figure 1.5 A fully connected mesh topology (five devices)
9
특징
- N개의 장치 연결을 위해 n (n-1)
/ 2 개의 물리적 채널이 필요
- 모든 장치는 n-1개의 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.
Multimedia Engineering Dept.
Figure 1.6 A star topology connecting four stations
10
특징
- 각 장치는 허브(Hub)라는 중앙
제어 장치와 전용 점대점 링크를
갖는다.
- 각 장치간 직접적인 통신은 할
수 없으며 제어장치가 교환 역할
수행
장점
- 1개의 링크와 1개의 I/O 포트만
필요 (비용이 적게 든다)
- 설치와 재구성이 쉽다.
- 안정성
단점
- 중앙 제어 장치 (Hub)의 고장은
전체 망에 영향을 준다.
Multimedia Engineering Dept.
Figure 1.7 A bus topology connecting three stations
특징
- 점대다중점 형태, 노드는 Tab과 Drop line으로 버스에 연결
- 버스가 수용할 수 있는 tab의 수와 tab간 간격은 제한됨.
장점
- 설치하기 쉽다.
단점
- 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
- 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
12
Multimedia Engineering Dept.
Figure 1.9 A hybrid topology: a star backbone with three bus networks
13
Multimedia Engineering Dept.
Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet
◈ LAN (Local Area Network) :
– Office, building or campus (수 Km로 제한)
– 개인 PC나 Workstation의 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
16
Multimedia Engineering Dept.
Figure 1.12 A heterogeneous network made of four WANs and two LANs
17
Multimedia Engineering Dept.
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)
18
Multimedia Engineering Dept.
인터넷 발전과정
1969
미국방성 프로젝트의 일환으로 ARPANET 개발
1979
TCP/IP 프로토콜 개발완료
1983
TCP/IP가 ARPANET 등 인터넷의 통신 표준안으로 채택
ARPANET이 연구용 ARPANET과 군사용 MILNET으로 분리
1986
미 과학재단에서 NSFNET 구축 , 인터넷 백본
1989
스위스 입자물리연구소 CERN에서 WWW 기술 개발 착수
1990
ARPANET 해체, 주된 기능을 NSFNET으로 이전, URL, HTTP, HTML
1991
WWW 개발완료, CERN에 WWW 설치
1993
Mosaic 개발
1994
Netscape 개발
1995
NSFNET은 연구망 운용을 전담하고, 일반 인터넷은 상업용 통신망사업
자가 주관하여 운용하기 시작함
19
Multimedia Engineering Dept.
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 2단계 사업 완료
(144개 지역에 광전송 및 ATM 기반의 초고속 국가망 구축)
◈ 2001. 6. 초고속 정보 통신망 3단계 고도화 계획 수립
◈ 2002. 4. e-Korea Vision 2006 수립
◈ 2002. 10. 초고속 가입자 수 1000만 돌파
◈ 2003. 3. 하나로, KT VDSL 서비스 개시
◈ 2005년부터 LG 파워컴에서 FTTH 서비스 시작
◈2013년 현재 기가 이더넷을 이용한 FTTH 일반화
– 2006년 6월 기준으로 한국의 100명당 초고속인터넷 가입자는 26.4명으로, 덴마
크(29.3명), 네덜란드(28.8명), 아이슬란드(27.3명)에 이어 4위를 기록했다. 5위
는 스위스(26.2명)로 조사됐다.
20
Multimedia Engineering Dept.
Figure 1.13 Hierarchical organization of the Internet
21
Multimedia Engineering Dept.
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
22
Multimedia Engineering Dept.
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)
23
Multimedia Engineering Dept.
Chapter 2
Network Models
24
Multimedia Engineering Dept.
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
25
Multimedia Engineering Dept.
Figure 2.1
Tasks involved in sending a letter
26
Multimedia Engineering Dept.
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
27
Multimedia Engineering Dept.
Figure 2.2 Seven layers of the OSI model
28
Multimedia Engineering Dept.
Figure 2.3 The interaction between layers in the OSI model
29
Multimedia Engineering Dept.
Figure 2.4 An exchange using the OSI model
30
Multimedia Engineering Dept.
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
31
Multimedia Engineering Dept.
Figure 2.5 Physical layer
The physical layer is responsible for movements of
individual bits from one hop (node) to the next.
32
Multimedia Engineering Dept.
Figure 2.6 Data link layer
The data link layer is responsible for moving
frames from one hop (node) to the next.
33
Multimedia Engineering Dept.
Figure 2.7 Hop-to-hop delivery
34
Multimedia Engineering Dept.
Figure 2.8 Network layer
The network layer is responsible for the
delivery of individual packets from
the source host to the destination host.
35
Multimedia Engineering Dept.
Figure 2.9 Source-to-destination delivery
36
Multimedia Engineering Dept.
Figure 2.10 Transport layer
The transport layer is responsible for the delivery
of a message from one process to another.
37
Multimedia Engineering Dept.
Figure 2.11 Reliable process-to-process delivery of a message
38
Multimedia Engineering Dept.
Figure 2.14 Application layer
The application layer is responsible for
providing services to the user.
39
Multimedia Engineering Dept.
Figure 2.15 Summary of layers
40
Multimedia Engineering Dept.
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
41
Multimedia Engineering Dept.
Figure 2.16 TCP/IP and OSI model
42
Multimedia Engineering Dept.
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
43
Multimedia Engineering Dept.
Figure 2.17 Addresses in TCP/IP
44
Multimedia Engineering Dept.
Figure 2.18 Relationship of layers and addresses in TCP/IP
45
Multimedia Engineering Dept.
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 10 is
the sender, and the computer with physical address 87 is
the receiver.
46
Multimedia Engineering Dept.
Figure 2.19 Physical addresses
47
Multimedia Engineering Dept.
Example 2.2
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:
07:01:02:01:2C:4B
A 6-byte (12 hexadecimal digits) physical address.
48
Multimedia Engineering Dept.
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.
49
Multimedia Engineering Dept.
Figure 2.20 IP addresses
50
Multimedia Engineering Dept.