Local Area Networks Prof Choong Seon HONG Kyung

Local Area Networks Prof. Choong Seon HONG Kyung Hee University 1

12장 근거리 통신망(LAN) 12. 1 프로젝트 (Project) 802 12. 2 이더넷(Ethernet) 12. 3 토큰 버스(Token Bus) 12. 4 토큰 링(Token Ring) 12. 5 FDDI (Fiber Distributed Data Interface) Kyung Hee University 2

프로젝트 802 (Cont’d) q프로젝트 802 Kyung Hee University 5

프로젝트 802 (Cont’d) q IEEE 802. 1 v LAN간 인터네트워킹 표준 안 v 기존 어드레스지정, 액세스 및 오류 복구 메커니즘을 변경하지 않고 네트워크 구조 (architecture) 간의 비호환성 (incompatibility) 을 해 결 q LLC(Logical Link Control) v IEEE 802. 2 v데이터링크계층의 상위계층으로 모든 LAN 프로토콜에 공통 v Containing the synchronization, flag, flow, and error control specifications q MAC(Medium Access Control) v 데이터링크 계층의 하위 서브 계층으로 공유 매체접근방법 제공 Kyung Hee University 6

프로젝트 802 (Cont’d) q프로토콜 데이터 단위(PDU: Protocol Data Unit) v LLC 레벨 데이터 단위 v HDLC와 유사한 4개의 필드로 구성 Kyung Hee University 7

프로젝트 802(계속) q제어(Control) 필드 v HDLC의 제어 필드와 동일 Kyung Hee University 8

12. 2 이더넷(Ethernet) q Xerox 사에서 개발된 802. 3 표준 v. Extended by DEC, Intel, and Xerox q. IEEE 802. 3 (PSK) Kyung Hee University 9

이더넷(계속) q. ACCESS Method : CSMA/CD v Today the terms Ethernet, CSMA/CD, 802. 3 are used interchangeably Kyung Hee University 10

이더넷(계속) q Collision Kyung Hee University in CSMA/CD 11

이더넷(계속) q주소지정 v 이더넷 네트워크상의 각 Station (pc, workstation, print 등) 은 자신의 NIC(Network Interface card)를 가짐 v 6바이트 길이의 유일한 물리 주소 Kyung Hee University 12

이더넷(계속) q전자 규격 v신호 방식(Signaling) l 베이스밴드(Baseband)시스템 - Manchester digital Encoding l 브로드밴드(Broadband)시스템 - differential PSK v전송속도(data rate) l 1~100 Mbps Kyung Hee University 13

이더넷(계속) q프레임 형식( Frame Format) v Not providing any mechanism for acknowledging received Kyung Hee University 14

이더넷(계속) q 프레임형식 v Preamble(7바이트) – combined the alert, timing, start synchronization v SFD(Start frame delimiter) - 프레임 시작 Ø the everything that follows is data. v DA(Destination address) - 목적지 주소 v SA(Source address) - 발신지 주소 v PDU 길이/유형 v 802. 2 프레임(PDU) - 46~1500 바이트길이 v CRC - 오류 검출 정보, CRC-32 Kyung Hee University 15

이더넷(계속) q구현(Implementation) v 10 BASE 5: Thick Ethernet v 10 BASE 2: Thin Ethernet v 10 BASE-T: Twisted-pair Ethernet v 1 BASE 5: Star LAN v. Fast Ethernet Kyung Hee University 16

이더넷(계속) q 10 BASE 5: Thick Ethernet(버스형) Kyung Hee University 17

이더넷(계속) q 10 BASE 5: Thick Ethernet v. RG-8 케이블: 802. 3 표준 backbone thick 동축케이블 v트랜시버(transceiver): MAU(medium attachment unit), transmitter-receiver v. AUI(attachment unit interface) 케이블: 15 -wire케이블(DB 15 pin), 최대길이 50 m v트랜시버 탭(Transceiver Tap) : vampire tap Kyung Hee University 18

이더넷(계속) q이더넷 세그먼트 Kyung Hee University 19

이더넷(계속) q 10 BASE 5 트랜시버 연결 Kyung Hee University 20

이더넷(계속) q 10 BASE 2 : Thin Ethernet v. NIC - thick Ethernet NIC + transceiver v. Thin 동축케이블 - RG-58 v. BNC-T - T자형 연결자(3 ports: NIC, input, output) Kyung Hee University 21

이더넷(계속) q 10 BASE 2 : Thin Ethernet(버스형) Kyung Hee University 22

이더넷(계속) q 10 BASE-T : Twisted-pair Ethernet v. The most popular standard defined in the IEEE 802. 3 series v. Star형 v. UTP(Unshielded twisted pair) 케이블 v전송속도: 10 Mbps v최대길이: 100 M(hub to station) v. Intelligent hub 이용 v. Four-pair RJ-45 케이블 Kyung Hee University 23

이더넷(계속) q 10 BASE-T : Twisted-pair Ethernet(star형) Kyung Hee University 24

이더넷(계속) q 1 BASE 5 : Star LAN v. AT&T제품 v저속 전송속도: 1 Mbps v. Twisted-pair 케이블 v. Hub당 최대 10 station Kyung Hee University 25

이더넷(계속) q 1 BASE 5 : Star LAN Kyung Hee University 26

12. 3 Other Ethernet Networks q An Ethernet network using a hub Kyung Hee University 27

Other Ethernet Networks (cont’d) q An Ethernet Network Using a Switch Kyung Hee University 28

Other Ethernet Networks (cont’d) q. Fast Ethernet v고속 전송속도: 100 Mbps v. Star형 v 10 base-T와 같은 MAC 프로토콜의 프레임 형식 v 4 pair category 3, category 5 UTP (2 pairs for transmission and two pairs for reception) v 100 BASE-X : 2 pair high-quality category 5 v 100 BASE-FX : two optical fiber v 100 BASE-TX : 2 pair STP Kyung Hee University 29

Other Ethernet Networks (cont’d) q. Categories of Fast Ethernet Implementations Kyung Hee University 30

Other Ethernet Networks (cont’d) q 100 Base-Tx Implementation Kyung Hee University 31

Other Ethernet Networks (cont’d) q 100 Base-Fx The distance between the station and hub (or switch) should be less than 2000 meters Kyung Hee University 32

Other Ethernet Networks (cont’d) q 100 Base-T 4 Implementation v Using four pairs of category 3 (voice grade) UTP v splitting the 100 -Mbps flow of data into three 33. 66 -Mbps flows v Using 8 B/6 T l Eight bits is transformed into six bauds of three voltage levels (positive, negative, and zero) Kyung Hee University 33

Other Ethernet Networks (cont’d) q 100 Base-T 4 Implementation (cont’d) Kyung Hee University 34

Other Ethernet Networks (cont’d) q Gigabit Ethernet v 1000 bps ~ 1 Gbps v MAC layer and access method remain same, but the collision domain is reduced v Physical layer – transmission media and the encoding system – is changed v Used for backbone to connect Fast Ethernet networks Kyung Hee University 35

Other Ethernet Networks (cont’d) q Use of Gigabit Ethernet Kyung Hee University 36

Other Ethernet Networks (cont’d) q Comparison between the Gigabit Ethernet Implementation Feature Medium Signal Max. distance 1000 Base-SX 1000 Base-LX 1000 Base-CX 1000 Base-T Optical Fiber (multimode) Optical Fiber (multi-or single-mode) STP UTP Short-wave laser Long-wave laser Electrical 550 m(multimode) 5000 m(single mode) 25 m Kyung Hee University 37

12. 4 토큰 버스(Token Bus) q. IEEE 820. 4 q물리적으로는 버스형 v. Physical Configuration of Ethernet q논리적으로 토큰을 이용한 링형(Ring using token) v. Using the collision-free feature of token ring q공장 자동화와 프로세스 제어에 이용 Kyung Hee University 38

12. 5 토큰 링(Token Ring) q. IEEE 802. 5 qtoken passing 방식 : access method v. Using three-byte token qtoken possession v Token ring allows each station to send one frame per turn. Kyung Hee University 39

토큰 링(계속) Kyung Hee University 40

토큰 링(계속) q토큰 링 v우선순위(Priority)와 예약(Reservation) l use of access control (AC) field v시간제한(Time Limit): 10 ms l each station expects to receive frames within regular time intervals v감시(monitor) station l Monitoring, regenerating a new token v주소 l 6 바이트 주소 (imprinted on the NIC card) Kyung Hee University 41

토큰 링(계속) q전자 규격 v differential Manchester 디지털신호방식 v 전송속도: 4 -16 Mbps q프레임형식 v 데이터(data) v 토큰(token) v 중지(abort) Kyung Hee University 42

토큰 링(계속) q토큰 링 프레임 Kyung Hee University 43

토큰 링(계속) q토큰링 데이터 프레임 For Differential Manchester Error Detected Bit Control information or Data How to use the information in the AC field Kyung Hee University 44

토큰 링(계속) q 토큰 링 프레임 v SD (Start delimiter) : 동기 타이밍 신호 l l l used to alert the receiving station to the arrival of a frame equivalent to the flag field in HDLC adopted J and K violation to ensure transparency in the data field v AC (Access control) : 우선순위 l l Three bits : priority field the token bit : set to indicate that the frame is a data frame rather than a token or an abort frame v FC (Frame control) : 정보유형(제어, 데이터) l l the first one bit : used to indicate the type of information contained in the PDU (control information or data) 7 bits : containing information used by the token ring logic (e. g. , how to use the information in the AC field) Kyung Hee University 45

토큰 링(계속) v. DA(Destination address) v. SA(Source address) v. Data: 4500바이트 v. CRC: CRC-32 오류 검출 v. ED(end delimiter) v. FS(Frame status): 수신자의 읽기 확인 l l set by the receiver to indicate that the frame has been read, or by the monitor to indicate that the frame has been already been around the ring So, saying that the frame can now be discarded Kyung Hee University 46

토큰 링(계속) q토큰 프레임 v 3개의 필드로 구성 : SD, AC, ED v used as a reservation frame to serve access to the ring q중지(Abort) 프레임 v 전송 종료 v Just including SD and ED v generated either by the sender to stop its own transmission, or by the monitor to purge an old transmission from the line Kyung Hee University 47

토큰 링(계속) q Implementation v The ring in the Token Ring consists of a series of 150 ohm, STP sections linking each station to its immediate neighbors Kyung Hee University 48

토큰 링(계속) v Token ring Switch Kyung Hee University 49

토큰 링(계속) q. MAU(Multistation Access Unit) Kyung Hee University 50

12. 5 FDDI (Fiber Distributed Data Interface) q. ANSI와 ITU-U(ITU-TX. 3) 표준 q전송매체 : 광케이블 q Copper version of FDDI : CDDI q전송속도 : 100 Mbps q. FDDI 동작 Kyung Hee University 51

FDDI (cont’d) q. Access Method : Token Passing v access is limited by allotted time q. Each station has three Time Registers to control circulation of the token and distribute link access opportunities among the nodes equitably. q Values are set when the ring is initialized and do not vary in the course of operation v. SA (Synchronous Allocation) l l The length of time allowed each station for sending synchronization data (time sensitive data) The time value is different for each station and is negotiated during initialization of the ring Kyung Hee University 52

FDDI (cont’d) v. TTRT (Target Token Rotation Time) l The average time required for a token to circulate around ring v. AMT (Absolute Maximum Time) l l A value equal to twice the TTRT If a token takes longer than this time to make one rotation of the ring, the ring must be reinitialized. q Timers v. Token Rotation Timer (TRT) l The actual time taken by the token to complete a cycle v. Token Holding Timer (THT) l l Begins running as soon as the token is received Showing how much time remains for sending asynchronous frames Kyung Hee University 53

FDDI (cont’d) q Station Procedure v When a token arrives, each station follows this procedure; 1. THT is set the difference between TTRT and TRT (THT = TTRT –TRT) 2. TRT is reset to zero (TRT = 0) 3. The station is set to zero (TRT = 0) 4. The station sends asynchronous data as long as the value of THT is positive. Kyung Hee University 54

FDDI (Cont’d) 2 2 q FDDI Example Kyung Hee University 55

FDDI (Cont’d) q Addressing v six-byte address similar to Ethernet address q Electronic Specification v Signaling (physical layer) l using a special encoding mechanism called 4 B/5 B l encoding by NRZ-I v Data Rate l up to 100 Mbps Kyung Hee University 56

FDDI (Cont’d) q Encoding by NRZ-I Kyung Hee University 57

FDDI(계속) q. FDDI 계층구조 Kyung Hee University 58

FDDI(계속) q. FDDI 프레임 유형 Kyung Hee University 59

FDDI(계속) q. FDDI 링(Dual Ring) Kyung Hee University 60

FDDI(계속) q. FDDI 링 절단 v The secondary ring makes FDDI self-healing. Kyung Hee University 61

FDDI(계속) q Node connections Kyung Hee University 63

12. 6 LAN 비교 Network Access Method Signaling Data Rate Error Control Ethernet CSMA/CD Manchester 1, 10 Mbps No Fast Ethernet CSMA/CD Several 100 Mbps No Gigabit Ethernet CSMA/CD Several 1 Gbps No Token Ring Token passing Differential Manchester 4, 16 Mbps Yes FDDI Token passing 4 B/5 B, NRZ-I 100 Mbps Yes Kyung Hee University 64