(Lan systems (chapter 14

صفحه 1:
William Stallings Data and Computer Communications Chapter 14 LAN Systems 

صفحه 2:
Ethernet (CSAM/CD) I Carriers Sense Multiple Access with Collision Detection 0 Xerox - Ethernet 0 IEEE 802.3 

صفحه 3:
IEEE802.3 Medium Access Control 0 Random Access I Stations access medium randomly 1 Contention I Stations content for time on medium 

صفحه 4:
ALOHA I Packet Radio 0 When station has frame, it sends Station listens (for max round trip time)plus small increment If ACK, fine. If not, retransmit If no ACK after repeated transmissions, give up Frame check sequence (as in HDLC) If frame OK and address matches receiver, send ACK Frame may be damaged by noise or by another station transmitting at the same time (collision) Any overlap of frames causes collision 0 Max utilization 18% 

صفحه 5:
Slotted ALOHA 0 Time in uniform slots equal to frame transmission time 0 Need central clock (or other sync mechanism) 0 Transmission begins at slot boundary 0 Frames either miss or overlap totally 0 Max utilization 37% 

صفحه 6:
CSMA I Propagation time is much less than transmission time All stations know that a transmission has started almost immediately First listen for clear medium (carrier sense) If medium idle, transmit If two stations start at the same instant, collision Wait reasonable time (round trip plus ACK contention) No ACK then retransmit Max utilization depends on propagation time (medium length) and frame length | Longer frame and shorter propagation gives better utilization 0 

صفحه 7:
If Busy? 0 If medium is idle, transmit 0 If busy, listen for idle then transmit immediately 0 If two stations are waiting, collision 

صفحه 8:
CSMA/CD I With CSMA, collision occupies medium for duration of transmission Stations listen whilst transmitting o If medium idle, transmit If busy, listen for idle, then transmit If collision detected, jam then cease transmission 0 After jam, wait random time then start again | Binary exponential back off بت اج 1 

صفحه 9:
‎A B 8 ۱‏ ‎N'stransmission 22‏ و 2 سود ‎rise,‏ ‏ار ‏دا یی ‎(SSM‏ .م22 سصسمة 5-572 ل محر ۲ مس ند سس یت 7777 سا سوت ‎rise,‏ ‎As tansmission £22 222222222222222222222222222222 22220‏ ‎ ‎Csteansmission ‏کت‎ ‎2 LIZ TE LILLIE PEDDIE ‎ ‎a on as ‎CSMA/CD ‎Operation ‎ 

صفحه 10:
Collision Detection 1 On baseband bus, collision produces much higher signal voltage than signal Collision detected if cable signal greater than single station signal Signal attenuated over distance Limit distance to 500m (10Base5) or 200m (10Base2) For twisted pair (star-topology) activity on more than one port is collision Special collision presence signal a os ot oa ص 

صفحه 11:
IEEE 802.3 Frame Format 

صفحه 12:
10Mbps Specification (Ethernet) I <data rate><Signaling method><Max segment length> I 10Base5 10Base2 10Base-T 10Base-FP 0 Medium Coaxial Coaxial UTP 850nm fiber 0 Signaling Baseband Baseband 0 Manchester 0 Manchester Manchester Manchester On/Off ۲ Topology Bus Bus Star Star 0 Nodes 100 30 - 33 

صفحه 13:
100Mbps (Fast Ethernet) I 100Base-TX 100Base-FX 100Base- 14 0 2pair,STP 2pair,Cat5UTP 2 optical fiber 4 pair, cat 3,4,5 0 MLT-3 MLT-3 4B5B,NRZI 8B6T,NRZ 

صفحه 14:
Gigabit Ethernet Configuration 100/1000-Mbps Hubs 

صفحه 15:
Gigabit Ethernet - Differences 0 Carrier extension 0 At least 4096 bit-times long (512 for 10/100) 0 Frame bursting 

صفحه 16:
Gigabit Ethernet - Physical 0 1000Base-SX 1 Short wavelength, multimode fiber 0 1000Base-LX I Long wavelength, Multi or single mode fiber 0 1000Base-CX ! Copper jumpers <25m, shielded twisted pair 0 1000Base-T I 4 pairs, cat 5 UTP 0 Signaling - 8B/10B 

صفحه 17:
Token Ring (802.5) I mac protocol I Small frame (token) circulates when idle I Station waits for token I Changes one bit in token to make it SOF for data frame Append rest of data frame Frame makes round trip and is absorbed by transmitting station Station then inserts new token when transmission has finished and leading edge of returning frame arrives Under light loads, some inefficiency Under heavy loads, round robin 

صفحه 18:
Token Ring ‏هر‎ ‎Operation 

صفحه 19:
Token Ring MAC Frame Octets 6 sD ED = ending delice AC FS = teame status Fc 7 46 ‏اخ * 7 * 11 م‎ 2<[ (6) ‏مس رز اد مس شاه‎ its ‏اما موز‎ bi [ean ۳۳۳۳ ‏ماك‎ 02221111 52 ‏مس ع ل‎ ] ۰1۰1۰. -«TaTeTs ‏با‎ Aces onl ae Ae Ad cgi ‏د‎ ۳ ۰۶ ۰ ۰ 7 »۰1« .با مس 7 عالط عور سسا :وز ال لماو اس ۳ (a Prams Connced Pista 

صفحه 20:
5. A sees the high priority token and captures it. 6A generates token al the preempted lower priority level. D B; Deserves at higher level 3. D uses higher priority token to send data to C. Priority Scheme 

صفحه 21:
Dedicated Token Ring 0 Central hub 0 Acts as switch 0 Full duplex point to point link 0 Concentrator acts as frame level repeater 0 No token passing 

صفحه 22:
802.5 Physical Layer I Data Rate 4 16 100 Medium UTP,STP, Fiber 4 Signaling Differential Manchester 0 Max Frame 4550 18200 18200 o Access Control TPorDTR TPorDTR DTR 4 Note: 1Gbit in development 

صفحه 23:
FDDI 0 100Mbps 0 LAN and MAN applications 0 Token Ring 

صفحه 24:
FDDI MAC Frame Format Bits «4 8 8 Wor 48 lords 20 2 4 1 Frame Format Preamble | SD FC ED (b) Token Frame Format sp Fc DA = destination address starting delimiter SA = source address ED = endi frame control Fes frame check sequence FS. = framestatus 

صفحه 25:
FDDI MAC Protocol 0 As for 802.5 except: ص Station seizes token by aborting token transmission Once token captured, one or more data frames transmitted New token released as soon as transmission finished (early token release in 802.5) ص ص 

صفحه 26:
4 FDDI Operation 

صفحه 27:
FDDI Physical Layer 0 Medium Optical Fiber Twisted Pair 0 Data rate 100 100 0 Signaling 4B/5B/NRZI MLT-3 0 Max repeaters 100 100 1 Between repeaters 2km 100m 

صفحه 28:
LAN Generations I First ۱ CSMA/CD and token ring I Terminal to host and client server I Moderate data rates 5 Second ۱ ۴۵۵۱ I Backbone I High performance workstations Third ۱ I Aggregate throughput and real time support for multimedia applications 

صفحه 29:
Third Generation LANs 0 Support for multiple guaranteed classes of service I Live video may need 2Mbps I File transfer can use background class 0 Scalable throughput I Both aggregate and per host 0 Facilitate LAN/WAN internetworking 

صفحه 30:
ATM LANs I Asynchronous Transfer Mode 0 Virtual paths and virtual channels U Preconfigured or switched 0 Gateway to ATM WAN 0 Backbone ATM switch I Single ATM switch or local network of ATM switches 0 Workgroup ATM I End systems connected directly to ATM switch U Mixed system 

صفحه 31:
Example ATM LAN ATM LAN nk to other ATM LAN 100 Mbps Ethernet 155 Mbps to public عممسامم اد ‎SMbps‏ 10-Mbps Ethernet 100 Mbps: 10.Mbps Ethernet 

صفحه 32:
ATM LAN HUB ATM Serial Ethernet ‘Token EDDIE Fthernet port ports ports ring’ ports ports AVM teh = =a. 100-Mbps = thernet Je Mbps aN 52۲ ,مرس p01 

صفحه 33:
Compatibility ص Interaction between end system on ATM and end system on legacy LAN Interaction between stations on legacy LANs of same type Interaction between stations on legacy LANs of different types ص ص 

صفحه 34:
Fiber Channel - Background I 8 channel Direct point to point or multipoint comms link Hardware based High Speed Very short distance User data moved from source buffer to destiation buffer ۲ Network connection I Interconnected access points | Software based protocol | Flow control, error detection &recovery I End systems connections 

صفحه 35:
Fiber Channel I Best of both technologies 0 Channel oriented ! Data type qualifiers for routing frame payload I Link level constructs associated with I/O ops ! Protocol interface specifications to support existing I/O architectures leg. SCSI 0 Network oriented ! Full multiplexing between multiple destinations ! Peer to peer connectivity 1 Internetworking to other connection technologies 

صفحه 36:
Fiber Channel Elements 0 End systems - Nodes 0 Switched elements - the network or fabric 0 Communication across point to point links 

صفحه 37:
Fiber Channel Network 

صفحه 38:
Fiber Channel Protocol Architecture (1) 1 FC-0 Physical Media | Optical fiber for long distance I coaxial cable for high speed short distance I STP for lower speed short distance 0 FC-1 Transmission Protocol | 8B/10B signal encoding 1 FC-2 Framing Protocol | Topologies I Framing formats ! Flow and error control I Sequences and exchanges (logical grouping of frames) 

صفحه 39:
Fiber Channel Protocol Architecture (2) 0 FC-3 Common Services I Including multicasting 0 FC-4 Mapping ۱ Mapping of channel and network services onto fiber channel | e.g. IEEE 802, ATM, IP, SCSI 

صفحه 40:
Wireless LANs [IEEE 802.11 ( Basic service set (cell) I Set of stations using same MAC protocol 1 Competing to access shared medium ۱ May be isolated ۱ May connect to backbone via access point (bridge) 0 Extended service set 1 Two or more BSS connected by distributed system I Appears as single logic LAN to LLC level 

صفحه 41:
Types of station 0 No transition ۱ Stationary or moves within direct communication range of single BSS 0 BSS transition | Moves between BSS within single ESS 0 ESS transition | From a BSS in one ESS to a BSS in another ESS I Disruption of service likely 

صفحه 42:
Wireless LAN - Physical I Infrared I 1Mbps and 2Mbps I Wavelength 850-950nm 0 Direct sequence spread spectrum 1 2.4GHz ISM band I Up to 7 channels | Each 1Mbps or 2Mbps 1 Frequency hopping spread spectrum 1 2.4GHz ISM band I 1Mbps or 2Mbps 1 Others under development 

صفحه 43:
Media Access Control 0 Distributed wireless foundation MAC (DWFMAC) 0 Distributed coordination function (DCF) ۱ 65۸۵ I No collision detection U Point coordination function (PCF) I Polling of central master 

صفحه 44:
802.11 MAC Timing Immediate access mf Contention window, Tonge than DIFS 3 4 (a) Basic Aveess Method ‘Superframe fixed nominal length Superirame (fixed nominal length) Conta tse mention perio ‏سید‎ ‘Comencon period PCF (optionaly | ‏]سس تس‎ اجب ‎eter}‏ (0) PCF Supertrame Cor 

صفحه 45:
Required Reading 0 Stallings chapter 14 0 Web sites on Ethernet, Token ring, FDDI, ATM etc. 

William Stallings Data and Computer Communications Chapter 14 LAN Systems Ethernet (CSAM/CD)  Carriers Sense Multiple Access with Collision Detection  Xerox - Ethernet  IEEE 802.3 IEEE802.3 Medium Access Control  Random Access  Stations access medium randomly  Contention  Stations content for time on medium ALOHA  Packet Radio  When station has frame, it sends  Station listens (for max round trip time)plus small increment  If ACK, fine. If not, retransmit  If no ACK after repeated transmissions, give up  Frame check sequence (as in HDLC)  If frame OK and address matches receiver, send ACK  Frame may be damaged by noise or by another station transmitting at the same time (collision)  Any overlap of frames causes collision  Max utilization 18% Slotted ALOHA  Time in uniform slots equal to frame transmission time  Need central clock (or other sync mechanism)  Transmission begins at slot boundary  Frames either miss or overlap totally  Max utilization 37% CSMA  Propagation time is much less than transmission time  All stations know that a transmission has started almost immediately  First listen for clear medium (carrier sense)  If medium idle, transmit  If two stations start at the same instant, collision  Wait reasonable time (round trip plus ACK contention)  No ACK then retransmit  Max utilization depends on propagation time (medium length) and frame length  Longer frame and shorter propagation gives better utilization If Busy?  If medium is idle, transmit  If busy, listen for idle then transmit immediately  If two stations are waiting, collision CSMA/CD  With CSMA, collision occupies medium for duration of transmission  Stations listen whilst transmitting  If medium idle, transmit  If busy, listen for idle, then transmit  If collision detected, jam then cease transmission  After jam, wait random time then start again  Binary exponential back off CSMA/CD Operation Collision Detection  On baseband bus, collision produces much higher signal voltage than signal  Collision detected if cable signal greater than single station signal  Signal attenuated over distance  Limit distance to 500m (10Base5) or 200m (10Base2)  For twisted pair (star-topology) activity on more than one port is collision  Special collision presence signal IEEE 802.3 Frame Format 10Mbps Specification (Ethernet)  <data rate><Signaling method><Max segment length>  10Base5  Medium  Signaling  Coaxial Coaxial Baseband Baseband Manchester On/Off Bus Bus 100 30  Topology  Nodes 10Base2 10Base-T 10Base-FP UTP Baseband Manchester 850nm fiber Manchester Manchester Star - Star 33 100Mbps (Fast Ethernet)  100Base-TX 100Base-FX 100Base- T4  2 pair, STP 3,4,5  MLT-3 2 pair, Cat 5UTP 2 optical fiber 4 pair, cat MLT-3 4B5B,NRZI 8B6T,NRZ Gigabit Ethernet Configuration Gigabit Ethernet - Differences  Carrier extension  At least 4096 bit-times long (512 for 10/100)  Frame bursting Gigabit Ethernet - Physical  1000Base-SX  Short wavelength, multimode fiber  1000Base-LX  Long wavelength, Multi or single mode fiber  1000Base-CX  Copper jumpers <25m, shielded twisted pair  1000Base-T  4 pairs, cat 5 UTP  Signaling - 8B/10B Token Ring (802.5)  MAC protocol  Small frame (token) circulates when idle  Station waits for token  Changes one bit in token to make it SOF for data frame  Append rest of data frame  Frame makes round trip and is absorbed by transmitting station  Station then inserts new token when transmission has finished and leading edge of returning frame arrives  Under light loads, some inefficiency  Under heavy loads, round robin Token Ring Operation Token Ring MAC Frame Priority Scheme Dedicated Token Ring      Central hub Acts as switch Full duplex point to point link Concentrator acts as frame level repeater No token passing 802.5 Physical Layer  Data Rate  Medium  Signaling  Max Frame  Access Control 4 16 100 UTP,STP,Fiber Differential Manchester 4550 18200 18200 TP or DTR TP or DTR DTR  Note: 1Gbit in development FDDI  100Mbps  LAN and MAN applications  Token Ring FDDI MAC Frame Format FDDI MAC Protocol  As for 802.5 except:  Station seizes token by aborting token transmission  Once token captured, one or more data frames transmitted  New token released as soon as transmission finished (early token release in 802.5) FDDI Operation FDDI Physical Layer  Medium Pair  Data rate  Signaling  Max repeaters  Between repeaters Optical Fiber Twisted 100 4B/5B/NRZI 100 2km 100 MLT-3 100 100m LAN Generations  First  CSMA/CD and token ring  Terminal to host and client server  Moderate data rates  Second  FDDI  Backbone  High performance workstations  Third  ATM  Aggregate throughput and real time support for multimedia applications Third Generation LANs  Support for multiple guaranteed classes of service  Live video may need 2Mbps  File transfer can use background class  Scalable throughput  Both aggregate and per host  Facilitate LAN/WAN internetworking ATM LANs  Asynchronous Transfer Mode  Virtual paths and virtual channels  Preconfigured or switched  Gateway to ATM WAN  Backbone ATM switch  Single ATM switch or local network of ATM switches  Workgroup ATM  End systems connected directly to ATM switch  Mixed system Example ATM LAN ATM LAN HUB Compatibility  Interaction between end system on ATM and end system on legacy LAN  Interaction between stations on legacy LANs of same type  Interaction between stations on legacy LANs of different types Fiber Channel - Background  I/O channel      Direct point to point or multipoint comms link Hardware based High Speed Very short distance User data moved from source buffer to destiation buffer  Network connection     Interconnected access points Software based protocol Flow control, error detection &recovery End systems connections Fiber Channel  Best of both technologies  Channel oriented  Data type qualifiers for routing frame payload  Link level constructs associated with I/O ops  Protocol interface specifications to support existing I/O architectures  e.g. SCSI  Network oriented  Full multiplexing between multiple destinations  Peer to peer connectivity  Internetworking to other connection technologies Fiber Channel Elements  End systems - Nodes  Switched elements - the network or fabric  Communication across point to point links Fiber Channel Network Fiber Channel Protocol Architecture (1)  FC-0 Physical Media  Optical fiber for long distance  coaxial cable for high speed short distance  STP for lower speed short distance  FC-1 Transmission Protocol  8B/10B signal encoding  FC-2 Framing Protocol     Topologies Framing formats Flow and error control Sequences and exchanges (logical grouping of frames) Fiber Channel Protocol Architecture (2)  FC-3 Common Services  Including multicasting  FC-4 Mapping  Mapping of channel and network services onto fiber channel  e.g. IEEE 802, ATM, IP, SCSI Wireless LANs  IEEE 802.11  Basic service set (cell)     Set of stations using same MAC protocol Competing to access shared medium May be isolated May connect to backbone via access point (bridge)  Extended service set  Two or more BSS connected by distributed system  Appears as single logic LAN to LLC level Types of station  No transition  Stationary or moves within direct communication range of single BSS  BSS transition  Moves between BSS within single ESS  ESS transition  From a BSS in one ESS to a BSS in another ESS  Disruption of service likely Wireless LAN - Physical  Infrared  1Mbps and 2Mbps  Wavelength 850-950nm  Direct sequence spread spectrum  2.4GHz ISM band  Up to 7 channels  Each 1Mbps or 2Mbps  Frequency hopping spread spectrum  2.4GHz ISM band  1Mbps or 2Mbps  Others under development Media Access Control  Distributed wireless foundation MAC (DWFMAC)  Distributed coordination function (DCF)  CSMA  No collision detection  Point coordination function (PCF)  Polling of central master 802.11 MAC Timing Required Reading  Stallings chapter 14  Web sites on Ethernet, Token ring, FDDI, ATM etc.