8 ARP RARP 8 1 ARP 8 2

제 8 장 ARP와 RARP 8. 1 ARP 8. 2 ARP 설계 8. 3 RARP 8. 4 요약 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 1

인터넷에서 사용하는 주소(계속) <ARP(Address Resolution Protocol) <RARP(Reverse Address Resolution Protocol) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 6

8. 1 ARP <ARP 동작 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 7

ARP(계속) <ARP 패킷 형식 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 8

ARP(계속) < Hardware type : 네트워크 유형 정의(이더넷 : 1) < Protocol type : 프로토콜 정의(IPv 4 : 080016) < Hardware length : 물리 주소의 바이트 단위 길이 < Protocol length : 논리 주소의 바이트 단위 길이 < Operation : 패킷 유형-ARP 요청(1), ARP 응답(2) < Sender hardware address : 송신자 물리 주소 < Sender protocol address : 송신자 논리 주소 < Target hardware address : 타겟 물리 주소 < Target protocol address : 타겟 논리 주소 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 9

ARP(계속) <캡슐화(Encapsulation) ÜARP 패킷의 캡슐화 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 10

ARP(계속) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 14

ARP(계속) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 15

ARP(계속) <프록시 ARP Ü 서브넷팅 효과를 만들기 위해 사용 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 16

ARP 설계(계속) < 캐쉬 테이블의 엔트리 구성 Ü 상태(State) : FREE, PENDING, RESOLVED Ü 하드웨어 유형(Hardware type) : Ü 하드웨어 길이(Hardware length) : Ü 프로토콜 길이(Protocol length) : Ü 인터페이스 번호(Interface number) : Ü 큐 번호(Queue number) : Ü 시도(Attempt) : ARP 요청 횟수 Ü 타임아웃(Time-out) : 엔트리 수명 Ü 하드웨어 주소(Hardware address) : 목적지 하드웨어 주소 Ü 프로토콜 주소(Protocol address) : 목적지 IP 주소 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 19

ARP 설계(계속) < 출력 모듈 Receive: an IP datagram from the processing module 1. Sleep until an IP packet is received from IP software. 2. Check the cache table to find an entry corresponding to this IP packet. 3. If(found) 1. If(the state is RESOLVED) 1. Extract the value of the hardware address from the entry. 2. Send the packet and the hardware address to data link layer. 3. Return. 2. If(the state is PENDING) 1. Enqueue the packet to the corresponding queue. 2. Return. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 20

ARP 설계(계속) 4. If(not found) 1. Create a queue. 2. Enqueue the packet. 3. Create a cache entry with state set to PENDING and ATTEMPTS set to 1. 4. Send an ARP request. 5. Return. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 21

ARP 설계(계속) < 입력 모듈 1. Sleep until an ARP packer(request or reply) arrives. 2. Check the cache table to find an entry corresponding to this ARP packet. 3. If(found) 1. If(the state is PENDING) 1. Update the entry. 2. While the queue is not empty 1. Dequeue one packet. 2. Send the packet and the hardware address to data link Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 22

ARP 설계(계속) 2. If(the state is RESOLVED) 1. Update the entry. 4. If(not found) 1. Create an entry. 2. Add the entry to the table. 5. If(the packet is a request) 1. Send an ARP relay 6. Return. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 23

ARP 설계(계속) < 캐쉬 제어 모듈 1. Sleep until the periodic timer matures. 2. For every entry in the cache table 1. If(the state is FREE) 1. Continue. 2. If(the state is PENDING) 1. Increment the value of attempts by 1. 2. If(attempts greater than maximum) 1. Change the state to FREE. 2. Destroy the corresponding queue. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 24

ARP 설계(계속) 3. If(not) 1. Send an ARP request. 4. Continue. 3. If(the state is RESOLVED) 1. Decrement the value of time-out by the value of elagsed time. 2. If(time-out less than or equal to zero) 1. Change the state to FREE. 2. Change the state to FREE. 3. Return. Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 25

ARP 설계(계속) <ARP 예제 Ü캐쉬 테이블의 초기 값 State Queue Attempt Time-out Protocol Addr. Hardware Addr. R 5 900 180. 3. 6. 1 ACAE 32457342 P 2 2 129. 34. 4. 8 P 14 5 201. 11. 56. 7 R 8 P 12 450 1 114. 5. 7. 89 457342 ACAE 32 220. 55. 5. 7 F R 9 P 18 Http: //netwk. hannam. ac. kr 60 3 19. 1. 7. 82 4573 E 3242 ACA 118. 11. 8. 71 HANNAM UNIVERSITY 26

ARP 설계(계속) <예제 2의 갱신된 테이블 State Queue R 5 P 2 2 129. 34. 4. 8 P 14 5 201. 11. 56. 7 R 8 P 12 1 220. 55. 5. 7 P 23 1 116. 1. 7. 22 R 9 P 18 Http: //netwk. hannam. ac. kr Attempt Time-out Protocol Addr. Hardware Addr. 900 180. 3. 6. 1 ACAE 32457342 450 60 3 114. 5. 7. 89 457342 ACAE 32 4573 E 3242 ACA 19. 1. 7. 82 188. 11. 8. 71 HANNAM UNIVERSITY 29

ARP 설계(계속) <예제 3의 갱신된 캐쉬 테이블 State Queue R 5 P 2 2 129. 34. 4. 8 P 14 5 201. 11. 56. 7 R 8 P 12 1 220. 55. 5. 7 P 23 1 116. 1. 7. 82 R 9 60 19. 1. 7. 82 R 18 900 118. 11. 8. 71 Http: //netwk. hannam. ac. kr Attempt Time-out Protocol Addr. Hardware Addr. 900 180. 3. 6. 1 ACAE 32457342 450 114. 5. 7. 89 457342 ACAE 32 E 34573242 ACA HANNAM UNIVERSITY 31

ARP 설계(계속) <예제 4의 갱신된 캐쉬 테이블 State Queue R 5 P 2 Attempt Time-out Protocol Addr. Hardware Addr. 840 180. 3. 6. 1 ACAE 32457342 2 129. 34. 4. 8 F R 8 390 114. 5. 7. 89 P 12 2 220. 55. 5. 7 P 23 2 116. 1. 7. 82 457342 ACAE 32 F P 18 Http: //netwk. hannam. ac. kr 840 118. 11. 8. 71 E 34573242 ACA HANNAM UNIVERSITY 33

RARP(계속) <RARP 동작 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 35

RARP(계속) <패킷 형식 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 36

RARP(계속) <RARP 패킷의 캡슐화 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 37

RARP(계속) <RARP 외의 다른 해결책 ÜBOOTP(15 장) ÜDHCP(15 장) Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 38

8. 4 요약 Http: //netwk. hannam. ac. kr HANNAM UNIVERSITY 39