로봇SW교육원 강의자료

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1 UNIT 01 컴퓨터네트워크소개 광운대학교로봇학부 최용훈

2 학습목표 2 컴퓨터네트워크와인터넷에대한전반적인이해를한다. 본과목에서사용할용어들에대해서살펴본다. 다양한전송매체를알아본다. 네트워크에서사용하는성능지표들을살펴본다.

3 본과목에서사용하는교재 3 주교재 Jim Kurose and Keith Ross, Computer Networking: A Top Down Approach, 6th edition, Addison-Wesley March 주교재에서제공하는슬라이드를활용하였습니다. (All material copyright , J.F Kurose and K.W. Ross, All Rights Reserved) 부교재 Richard Stevens, UNIX Network Programming: The Sockets Networking API, 3 rd edition, Addison-Wesley, 최지훈, 네트워크프로그래밍, 프리렉, 2014 년 10 월.

4 인터넷이란? 4 PC server wireless laptop smartphone wireless links wired links millions of connected computing devices: hosts = end systems running work apps communication links fiber, copper, radio, satellite transmission rate: bandwidth mobile work home work global ISP regional ISP router Packet switches: forward packets (chunks of data) routers and switches institutional work

5 프로토콜이란? 5 a human protocol and a computer work protocol: Hi Hi Got the time? 2:00 time TCP connection request TCP connection response Get <file> protocols define format, order of msgs sent and received among work entities, and actions taken on msg transmission, receipt

6 Network Edge 6 Access Network DSL (Digital Subscriber Line, 전화망활용 ) Cable Modem ( 케이블 TV 망활용 ) Ether Wireless LAN (Wi-Fi) 3G, 4G

7 전송매체 Guided media: signals propagate in solid media: copper, coax, fiber 7 Twisted Pair (TP) Unguided media: signals propagate freely, e.g., radio Coaxial Cable Fiber Optic Cable

8 전송매체 (Radio) 8 지상파 (Terrestrial Microwave) Bluetooth, ZigBee, Wi-Fi, 3G/4G, TV 방송, 라디오방송, 지상파 DMB, 재난망 (TETRA) 테라헤르츠 ~ 가시광대역이용 가시광통신, 적외선통신, mmwave 위성 (Satellite) 저궤도, 중궤도, 정지궤도위성 C 밴드, Ku 밴드, Ka 밴드

9 전송매체 (Radio) 9 회절성높음 Omni-directional (NLOS) 직진성높음 Directional (LOS) 긴안테나필요 짧은안테나

10 Network Core 10 mesh of interconnected routers packet-switching: hosts break application-layer messages into packets forward packets from one router to the next, across links on path from source to destination each packet transmitted at full link capacity

11 Two key work-core functions 11 routing: determines sourcedestination route taken by packets routing algorithms forwarding: move packets from router s input to approp riate router output routing algorithm local forwarding table header value output link dest address in arriving packet s header

12 인터넷구성도 12 Option: connect each ISP to every other ISP? connecting each ISP to each other directly doesn t scale: O(N 2 ) connections.

13 인터넷구성도 13 Option: connect each ISP to a global transit ISP? Customer and provider ISPs have economic agreement. ISP A IXP IXP ISP B ISP C regional

14 성능지표 : 지연 (Delay) 14 A transmission propagation B nodal processing queueing d nodal = d proc + d queue + d trans + d prop d proc : nodal processing check bit errors determine output link typically < msec d queue : queueing delay time waiting at output link for transmission depends on congestion level of router

15 성능지표 : 지연 (Delay) 15 A transmission propagation B nodal processing queueing d nodal = d proc + d queue + d trans + d prop d trans : transmission delay: L: packet length (bits) R: link bandwidth (bps) d trans = L/R d trans and d prop very different d prop : propagation delay: d: length of physical link s: propagation speed in medium (~2x10 8 m/sec) d prop = d/s

16 성능지표 : 패킷손실 (Packet Loss) 16 queue (aka buffer) preceding link in buffer has finite capacity packet arriving to full queue dropped (aka lost) lost packet may be retransmitted by previous node, by source end system, or not at all A buffer (waiting area) packet being transmitted B packet arriving to full buffer is lost

17 성능지표 : 처리율 (Throughput) 17 throughput: rate (bits/time unit) at which bits transferred between sender/receiver instantaneous: rate at given point in time average: rate over longer period of time server server, sends with bits (fluid) file of into F bits pipe to send to client link pipe capacity that can carry R s bits/sec fluid at rate R s bits/sec) link pipe capacity that can carry R c bits/sec fluid at rate R c bits/sec)

18 인터넷에서경로와지연측정방법 18 what do real Inter delay & loss look like? traceroute program: provides delay measurement from source to router along end-end Inter path towards destination. For all i: sends three packets that will reach router i on path towards destination router i will return packets to sender sender times interval between transmission and reply. 3 probes 3 probes 3 probes

19 실습 1: 인터넷에서지연과경로측정 19 아래순서대로따라하세요. 1) 윈도우실행창 ( 도스창 ) 을띄운다. 2) ipconfig 명령을실행하여, IP 주소, 게이트웨이주소확인.

20 실습 1: 인터넷에서지연과경로측정 20 아래순서대로따라하세요. 3) 목적지의 IP 주소확인을위해, nslookup 명령실행 예 : 로의경로및지연측정 구글의 IP 주소. ( 내컴퓨터에서가장가까운곳에위치한서버목록임 )

21 실습 1: 인터넷에서지연과경로측정 21 아래순서대로따라하세요. 4) tracert 또는 tracert 명령 게이트웨이 경로 해당노드까지의지연 최종목적지

chapter4

chapter4 Basic Netw rk 1. ก ก ก 2. 3. ก ก 4. ก 2 1. 2. 3. 4. ก 5. ก 6. ก ก 7. ก 3 ก ก ก ก (Mainframe) ก ก ก ก (Terminal) ก ก ก ก ก ก ก ก 4 ก (Dumb Terminal) ก ก ก ก Mainframe ก CPU ก ก ก ก 5 ก ก ก ก ก ก ก ก ก ก