Chapter 2 The OSI Model and the TCP IP

Chapter 2 The OSI Model and the TCP/IP Protocol Suite Objectives Upon completion you will be able to: • Understand the architecture of the OSI model • Understand the layers of the OSI model and their functions • Understand the architecture of the TCP/IP Protocol Suite • Differentiate between the OSI model and the TCP/IP Suite • Differentiate between the three types of Internet addresses Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 1

CONTENTS • THE OSI MODEL • LAYERS IN THE OSI MODEL • TCP/IP PROTOCOL SUITE • ADDRESSING • TCP/IP VERSIONS Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 2

2. 1 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 1970 s. The topics discussed in this section include: Layered Architecture Peer-to-Peer Processes Encapsulation Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 3

2. 1 OSI 모델 Ü Open System Interconnection Ü ISO 7498 OSI Basic Reference Model Ü 모든 종류의 컴퓨터 시스템간 통신을 가능하게 하 는 네트워크 설계를 위한 계층 구조 Ü 서로 연관된 7 계층으로 구성 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 4

Note: ISO is the organization. OSI is the model Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 5

2. 1 OSI 모델(계속)

2. 1 OSI 모델(계속)

Headers are added to the data at layers 6, 5, 4, 3, and 2. Trailers are usually added only at layer 2. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 8

2. 1 OSI 모델(계속)

2. 2 Layers in the OSI Model The functions of each layer in the OSI model is briefly described. The topics discussed in this section include: Physical Layer Data Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer Summary of Layers Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 10

2. 2 OSI 모델의 계층 <물리계층(physical layer) Ü물리적인 매체를 통하여 비트 스트림을 전송하는데 필요한 기능 제공 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 11

Note: The physical layer is responsible for the movement of individual bits from one hop (node) to the next. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 12

2. 2 OSI 모델의 계층(계속) <물리계층의 주요 기능 Ü장치와 전송 매체간의 인터페이스 특성과 전송 매체 유형 규정 Ü비트 표현 방법(부호화 유형) Ü데이터 전송 속도(bps) Ü비트의 동기화(송수신자간 클록) Ü회선 구성(점대점, 다중점) Ü접속형태(mesh, star, ring, bus, tree) Ü전송 모드(simplex, half-duplex, full-duplex) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 13

2. 2 OSI 모델의 계층(계속) <데이터링크계층(data link layer) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 14

2. 2 OSI 모델의 계층(계속) <데이터링크층의 주요 기능 Ü프레임(frame) 구성 Ü물리 주소 지정(송수신자 주소) Ü흐름 제어 Ü오류 제어 Ü접근 제어 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 15

Note: The data link layer is responsible for moving frames from one hop (node) to the next. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 16

2. 2 OSI 모델의 계층(계속) <노드-대-노드 전달 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 17

2. 2 OSI 모델의 계층(계속) <네트워크계층(network layer) Ü패킷(packet)을 네트워크를 통하여 발신지에서 목적 지까지 전달 책임 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 18

Note: The network layer is responsible for the delivery of individual packets from the source host to the destination host. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 19

2. 2 OSI 모델의 계층(계속) <네트워크계층 주요 기능 Ü논리 주소 지정 Ü라우팅 w 패킷이 최종 목적지에 전달될 수 있도록 경로를 지정하거 나 교환 기능 제공 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 20

2. 2 OSI 모델의 계층(계속) <종단-대-종단 전송 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 21

2. 2 OSI 모델의 계층(계속) <전송계층(transport layer) Ü발신지에서 목적지(종단-대-종단)까지 전체 메시 지 전달기능 제공 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 22

Note: The transport layer is responsible for the delivery of a message from one process to another. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 23

2. 2 OSI 모델의 계층(계속) <전송계층 주요 기능 Ü서비스 지점 주소지정(포트 주소) Ü분할과 재조립(Segmentation and reassembly) Ü연결 제어(Connection Control) Ü흐름 제어(Flow Control) Ü오류 제어(Error Control) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 24

2. 2 OSI 모델의 계층(계속) <신뢰성 있는 종단-대-종단 메시지 전송 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 25

2. 2 OSI 모델의 계층(계속) <세션계층(session layer) Ü통신 시스템간의 상호 대화 설정, 유지, 동기화 기능 제 공 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 26

2. 2 OSI 모델의 계층(계속) <세션계층의 주요 기능 Ü대화 제어(반이중, 전이중) Ü동기화(검사점 추가) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 27

2. 2 OSI 모델의 계층(계속) <표현계층(presentation layer) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 28

2. 2 OSI 모델의 계층(계속) <표현계층의 주요 기능 Ü변환(Translation) Ü암호화(Encryption) Ü압축(Compression) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 29

2. 2 OSI 모델의 계층(계속) <응용계층(application layer) Ü사용자나 소프트웨어를 네트워크에 접근 가능하도록 하는 기능 제공 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 30

2. 2 OSI 모델의 계층(계속) <응용계층 주요 기능 Ü네트워크 가상 터미널(Network Virtual Terminal) Ü파일 접근, 전송 및 관리(File Transfer, Access, and Management) Ü우편 서비스(Mail Service) Ü디렉토리 서비스(Directory Service) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 31

2. 2 OSI 모델의 계층(계속) <계층별 요약 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 32

2. 3 TCP/IP Protocol Suite The TCP/IP protocol suite is made of five layers: physical, data link, network, transport, and application. The first four layers provide physical standards, network interface, internetworking, and transport functions that correspond to the first four layers of the OSI model. The three topmost layers in the OSI model, however, are represented in TCP/IP by a single layer called the application layer. The topics discussed in this section include: Physical and Data Link Layers Network Layer Transport Layer Application Layer Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 33

2. 3 TCP/IP 프로토콜

2. 3 TCP/IP 프로토콜(계속) < TCP/IP 프로토콜 1. 물리계층과 데이터링크계층 w 기존의 모든 표준과 기술적인 프로토콜 지원 2. 네트워크 계층 w 인터넷 프로토콜(IP) : host-to-host protocol w 주소변환 프로토콜(ARP) w 역주소변환 프로토콜(RARP) w 인터넷 제어 메시지 프로토콜(ICMP) w 인터넷 그룹 메시지 프로토콜(IGMP) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 35

2. 3 TCP/IP 프로토콜(계속) 3. 전송계층 w 사용자 데이터그램 프로토콜(UDP) w 전송 제어 프로토콜(TCP) 4. 응용계층 w OSI 모델의 세션, 표현, 응용층을 합친것 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 36

2. 4 Addressing Three different levels of addresses are used in an internet using the TCP/IP protocols: physical (link) address, logical (IP) address, and port address. The topics discussed in this section include: Physical Address Logical Address Port Address Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 37

2. 4 주소지정

2. 4 주소지정(계속)

2. 4 주소지정(계속) <물리 주소 Ü링크 주소 ÜWAN이나 LAN에서 정의된 노드의 주소 Ü이더넷 네트워크 인터페이스 카드(NIC) 6바이트(48 비트) 주소 Ü유니캐스트(unicast), 멀티캐스트(multicast), 브로드 캐스트(broadcast) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 40

example 1 In Slide 42 a node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by a link. At the data link level this frame contains physical (link) addresses in the header. These are the only addresses needed. The rest of the header contains other information needed at this level. The trailer usually contains extra bits needed for error detection. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 41

2. 4 주소지정(계속) <물리 주소 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 42

example 2 As we will see in Chapter 3, most local area networks use a 48 -bit (6 bytes) physical address written as 12 hexadecimal digits, with every 2 bytes separated by a colon as shown below: 07: 01: 02: 01: 2 C: 4 B A 6 -byte (12 hexadecimal digits) physical address. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 43

2. 4 주소지정(계속) <인터넷 주소 Ü현재 인터넷에 연결된 호스트 식별 : 32비트 주소 체계 Ü유니캐스트(단일사용자), 멀티캐스트(그룹수신자), 브 로드캐스트(네트워크 내의 모든 시스템) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 44

example 3 In Slide 47 we want to send data from a node with network address A and physical address 10, located on one LAN, to a node with a network address P and physical address 95, located on another LAN. Because the two devices are located on different networks, we cannot use link addresses only; the link addresses have only local jurisdiction. What we need here are universal addresses that can pass through the LAN boundaries. The network (logical) addresses have this characteristic. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 45

example 3 (Continued) The packet at the network layer contains the logical addresses, which remain the same from the original source to the final destination (A and P, respectively, in the figure). They will not change when we go from network to network. However, the physical addresses will change as the packet moves from one network to another. The boxes labeled routers are internetworking devices, which we will discuss in Chapter 3. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 46

2. 4 주소지정(계속)

example 4 As we will see in Chapter 4, an Internet address (in IPv 4) is 32 bits in length, normally written as four decimal numbers, with each number representing 1 byte. The numbers are separated by a dot. Below is an example of such an address. 132. 24. 75. 9 An internet address in IPv 4 in decimal numbers Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 48

example 5 Slide 51 shows an example of transport layer communication. Data coming from the upperlayers have port addresses j and k ( j is the address of the sending process, and k is the address of the receiving process). Since the data size is larger than the network layer can handle, the data are split into two packets, each packet retaining the service-point addresses ( j and k). Then in the network layer, network addresses (A and P) are added to each packet. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 49

example 5 (Continued) The packets can travel on different paths and arrive at the destination either in order or out of order. The two packets are delivered to the destination transport layer, which is responsible for removing the network layer headers and combining the two pieces of data for delivery to the upper layers. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 50

2. 4 주소지정(계속) <포트 주소 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 51

example 6 As we will see in Chapters 11, 12, and 13, a port address is a 16 -bit address represented by one decimal number as shown below. 753 A 16 -bit port address represented as one single number. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 52

2. 5 IP Versions IP became the official protocol for the Internet in 1983. As the Internet has evolved, so has IP. There have been six versions since its inception. We look at the latter three versions here. The topics discussed in this section include: Version 4 Version 5 Version 6 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 53

알림 연습문제 풀이해서 Report로 다음주까지(일주일 후) 제출해 주세요! Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 54