(C) Ho-Won Jung, Korea University 1 Chapter 13:Accessing and Using the Internet College of Business Administration Korea University Ho-Won Jung, office B309 ( ) College of Business Administration Korea University

(C) Ho-Won Jung, Korea University 2 Figure 13-3 ISP Configuration

(C) Ho-Won Jung, Korea University 3 Figure 13-6 Generic Firewall

(C) Ho-Won Jung, Korea University 4 Figure 13-7 Gateway Firewall

(C) Ho-Won Jung, Korea University 5 Figure 13-8 Screened Subnet Firewall

(C) Ho-Won Jung, Korea University 6 Chapter 14: Internet technology College of Business Administration Korea University Ho-Won Jung, office B309 ( ) College of Business Administration Korea University

(C) Ho-Won Jung, Korea University 7 TCP/IP  TCP/IP: 이기종 컴퓨터간 internetworking 및 interoperability 의 solution  LAN, MAN, WAN, 또는 이들의 조합은 TCP/IP 를 지원  User-to-user 또는 computer-to-computer 간 범 세계적인 통신지원  Internet 의 의미 ① 동사 : IBM 의 SAN 와 DEC 의 DECnet 과 internetworking 한다. ② 명사 : 두개 이상의 network 로 구성된 network ③ 고유명사 : User-to-user 또는 computer-to-computer 간 범 세계적인 통신 지원을 목적으로 전세계에 설치되어 있는 network group

(C) Ho-Won Jung, Korea University 8 Internet history  1969  ARPANET (Advanced Research Projects Agency Network) 으로 탄생  DARPA (U.S. Defense Advanced Research Projects Agency) 가 후원  Packet switching network 의 능력 시험을 목적으로 함  Bolt, BBN Communications Inc. 가 구축 계약자  SRI, UCSB9 (University of California at Santa Barbara), UCLA, University of Utah 에서 개통  IMP (Interface Message Processor) 로 Honeywell 316 minicomputer 사용

(C) Ho-Won Jung, Korea University 9  1981  NSF (National Science Foundation) 의 CSNET(Computer Science Network) 자금지원  1984  ARPANET 을 MILNET ( 비밀 분류 안된 군사용 ) 과 ARPANET ( 비군사용 ) 의로 구분  NSF 의 슈퍼컴퓨터 개발 및 이의 access 를 위한 OASC (Office of Advanced Scientific Computing) 설립. 6 개의 슈퍼컴퓨팅센터를 T-1 으 로 연결하기 위한 NSFNET 개발. 추후 T-3 로 대체.  1990 년 6 월 미국방성은 ARPANET 폐기 선언

(C) Ho-Won Jung, Korea University 10 Internet 의 문서화  IAB (Internet Activity Board)  Internet design 과 planing  Standard 개발, RFC (Request For Comments) 문서의 출판, IEFT (Internet Engineering Task Force) 감독  산하의 두 개의 task forces  IETF(Internet Engineering Task Force): Internet 의 기술적인 측면과 protocol 조정  IRTF (Internet Research Task Force): 새로운 기술 연구  IR (Internet Registry)  Internet address, documents 의 중앙관리

(C) Ho-Won Jung, Korea University 11 DARPA 와 OSI  DARPA 와 OSI Reference model 의 공통점  이기종 컴퓨터의 연결  DARPA 와 OSI Reference model 의 차이점  OSI RM 이 보다 넓은 범위  ISO 개발  표준개발에서 전 세계적인 input  보다 광범위한 open systems 의 상호연결 및 연결될 시스템의 type( 군사용 또는 비군사용 ) 의 제약이 없음  이를 위해 7 layer 로 정의

(C) Ho-Won Jung, Korea University 12 ARP: Address Resolution Protocol BGP: Border Gateway Protocol CHARGEN : Character Generator Protocol DISCARD : Discard Protocol DNS: Domain Name Services EGP: Exterior Gateway Protocol FTP: File Transfer Protocol GGP: Gateway-to-Gateway Protocol ICMP: Internet Control Message Protocol IGMP: Internet Group Multicast Protocol IGP: Interior Gateway Protocol IP : Internet Protocol MIB : Management Information Base MINE : Multipurpose Internet Mail Extensions NETBIOS: NETwork Basic Input Output System NTP: Network Time Protocol PPP: Point-to-Point Protocol QUOTE: Quote of the Day Protocol RARP : Reverse Address Resolution Protocol RIP : Routing information Protocol SMI : Structure of Management Information SMTP: Single Mail Transfer Protocol SNP: Subnetwork Protocol TCP : Transmission Control Protocol TELNET : Telecommunications Network TFTP: Trivial File Transfer Protocol UDP: User Datagram Protocol

(C) Ho-Won Jung, Korea University 13 Internet Standard Protocols RFC Protocol Description 1060 Assigned Numbers 1009 Gateway Requirements 1122 Host Requirements - Communication 1123 Host requirements - Applications 791 IP Internet Protocol 950 IP Subnet Extension 919 IP Broadcast Datagram 922 IP Broadcast Datagram- with Subnets 792 ICMP Internet Control Message Protocol 1112 IGMP Internet Group Multicast Protocol 768 UDP User Datagram Protocol 793 TCP Transmission Control Protocol 1155 SMI Structure of Management Information 1156 MIB Management Information Base 1157 SNMP Simple Network Management Protocol 1034,1035 Domain Domain Name System 854 TELNET TELNET Protocol 959 FTP File Transfer Protocol 821 SMTP Simple Mail Transfer Protocol 822 MAIL Format of Electronic Mail Messages 1049 CONTENT Content Type Header Field 904 EGP Exterior Gateway Protocol 862 ECHO Echo Protocol RFC Protocol Description 1119 NTP Network Time Protocol 1001,1002 NETBIOS NetBIOS Service Protocol 863 DISCARD Discard Protocol 864 CHARGEN Character Generator Protocol 865 QUOTE Quote of the Day Protocol 866 USERS Active Users Protocol 867 DAYTIME Daytime Protocol 868 TIME Time Server Protocol 826 ARP Address Resolution Protocol 903 RARP Reverse Address Resolution Protocol B1822 IP-ARPA Internet Protocol on ARPANET 907 IP-WB Internet Protocol on Wideband Net 877 IP-X25 Internet Protocol on X.25 Nets 894 IP-E Internet Protocol on Ethernets 895 IP-EE Internet Protocol on Exp. Ethernets 1042 IP-IEEE Internet Protocol on IEEE IP-DC Internet Protocol on Dc Networks 1044 IP-HC Internet Protocol on Hyperchannel 1051 IP-ARC Internet Protocol on ARCNET 1055 IP-SLIPTransmission of IP over Serial Lines 1088 IP-NETBIOSTransmission of IP over NETBIOS 1103 IP-FDDI Transmission of IP over FDDI 1132 IP-IPX Transmission of IP over IPX Nets

(C) Ho-Won Jung, Korea University 14 DARPA protocol 과 OSI 구조 비교 FTP: File Transfer Protocol SMTP: Simple Mail Transfer Protocol VFTP: Trivial File Transfer Protocol NFS: (Sun Microsystems) Network File System SNMP: (Simple Network Management Protocol) UDP: User Datagram Protocol TCP: Transaction Control Protocol IP: Internet protocol ICMP: Internet Control Message Protocol Network access layer Physical layer Internet layer Transport Application

(C) Ho-Won Jung, Korea University 15 Layer 1: Physical Layer m Physical interface between a DTE (e.g. computer or terminal) and a trans mission medium m Specifies: ê Characteristics of medium ê Nature of signals ê Data rate

(C) Ho-Won Jung, Korea University 16 Layer 2: Network Access Layer m Exchange of data between end system and network  frame 생성  frame 은 Ethernet LAN, PDN, WAN 의 X.25 interface 와 같이 H/W 에 의 해 정의 m Software at this layer depends on network (e.g. X.25 vs. Ethernet) m Address of host and destination m Prioritization of transmission

(C) Ho-Won Jung, Korea University 17 Layer 3: Internet Layer m An Internet is an interconnection of two or more networks m Internet layer handles tasks similar to network access layer, but between n etworks rather than between nodes on a network m Uses IP for addressing and routing across networks m Implemented in workstations and routers  Packet 를 host 에서 host 로 전송  packet 은 internetwork 간의 travel 를 위한 address 포함.  참조로 frame header address 는 같은 local network 상의 host 에서 host 로 frame 전송  ARP (Address Resolution Protocol) : IP address 와 LAN address 간의 변환 방법 제공  RARP (Reverse Address Resolution Protocol) : LAN address 로 부터 IP address 로 변환  ICMP: Host 나 gateway 상의 IP S/W 가 다른 시스템과 통신 방법 제공  예 ) Ping (echo request; 통신경로 시험 )

(C) Ho-Won Jung, Korea University 18 IP and IPv6 m IP provides for 32-bit source and destination addresses. m IPv6 (1996 standard) provides for 128-bit addresses. m Migration to IPv6 will be a very slow process.

(C) Ho-Won Jung, Korea University 19  Version: IP protocol 의 현재 Version  IHL (Internet Header Length): word 로 header 길이 측정  Type of service: datagram 이 요구하는 서비스 품질  Total length: Octet 로 표현된 IP datagram 의 길이 (IP header + 상위정보 ).  모든 host 는 적어도 576 octets 의 datagram 처리 가능해야 하며  IP 는 최대 65,536 ( 2^32 ) octets 까지 위 datagram 허용

(C) Ho-Won Jung, Korea University 20

(C) Ho-Won Jung, Korea University 21 Layer 4: Transport Layer (Host-to-Host) m Also called host-to-host layer m Reliable exchange of data between applications  Packet 분실이나 error 없음을 보장  delivery 보장 m Uses TCP protocols for transmission

(C) Ho-Won Jung, Korea University 22 TCP and UDP m Most TCP/IP applications use TCP for transport layer. m TCP provides a connection (logical association) between two entities to re gulate flow check errors. m UDP (User Datagram Protocol) does not maintain a connection, and there fore does not guarantee delivery, preserve sequences, or protect against du plication.

(C) Ho-Won Jung, Korea University 23 Port = SAP 16 bit frame check sequence in the TCP segment Refer to pager 88 in detail. See Table 4.2 (p. 89)

(C) Ho-Won Jung, Korea University 24 Layer 5: Application Layer m Logic needed to support variety of applications. m Separate module supports each type of application (e.g. file transfer) ê 신뢰성 보장을 위해 TCP 위에 구현 Þ FTP: File Transfer Protocol (TCP 위에 구현 ) Þ SMTP: Simple Mail Transfer Protocol (TCP 위에 구현 ) Þ TELNET: remote host 의 access 및 terminal emulation 제공 (TCP 위에 구현 ) ê 송신을 경제적으로 하며, UDP 위에 구현 Þ VFTP: Trivial File Transfer Protocol Þ NFS: (Sun Microsystems) Network File System Þ SNMP: (Simple Network Management Protocol) SNMP: 최소한의 overhead 로 콘솔과 agent ( 관리되는 장치 ) 간 통신. 좀더 복잡한 방법은 CMIP (Common Management Information Protocol) 이며, TCP/IP 와 함께 사용하면 CMOT (CMIP over TCP/IP) 라 함.

(C) Ho-Won Jung, Korea University 25 Operation of TCP/IP

(C) Ho-Won Jung, Korea University 26 Transport header  Destination SAP (DSAP)  Sequence number  Error detection code Network header  Destination computer address (Dhost)  Facilities requests (e.g., priority)

(C) Ho-Won Jung, Korea University 27 Internet Addressing  Source and destination addresses (32 bits)  Host ID  Network ID  Class A ∼ E (5 개 formats): 첫 3 bits 에 의해 식별  Dotted decimal notation ê (binary) ê (decimal)  Network ID 는 국가의 중앙 단체가 할당하고 host ID 는 local network 관리자가 부여

(C) Ho-Won Jung, Korea University 28

(C) Ho-Won Jung, Korea University 29 Internet address  Source and destination addresses (32 bits)  Host ID  Network ID  Class A ∼ E (5 개 formats): 첫 3 bits 에 의해 식별  Network ID 는 국가의 중앙 단체가 할당하고 host ID 는 local network 관리자가 부여

(C) Ho-Won Jung, Korea University 30 Internet address classes  Class A  많은 host 를 가진 큰 network 을 위해 설계  Network ID 에서 2^7  128 개 address 중에 0 과 127 address 는 유보  Class B  LAN 과 host 를 포함하는 분산처리 시스템을 가지는 조직에서 사용  Network ID 에서 2^14  16,383 개 address 중에 0 과 16,384 address 는 유보  Class C  LAN 과 같은 소규모 network 을 위해 사용  Network ID 에서 2^21  2,097,152 개 address 중에 0 과 2,097,152 address 는 유보

(C) Ho-Won Jung, Korea University 31 IP address formats

(C) Ho-Won Jung, Korea University 32