Data and Computer Communications Ninth Edition by William Stallings Chapter 16 – High Speed LANs Data and Computer Communications, Ninth Edition by William.

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1 Data and Computer Communications Ninth Edition by William Stallings Chapter 16 – High Speed LANs Data and Computer Communications, Ninth Edition by William Stallings, (c) Pearson Education - Prentice Hall, 2011

2 Introduction  rapid changes in technology designs  broader use of LANs  new schemes for high-speed LANs  high-speed technologies: Fast and Gigabit Ethernet Fast and Gigabit Ethernet Fibre Channel Fibre Channel High Speed Wireless LANs High Speed Wireless LANs

3 Characteristics of Some High- Speed LANs

4 CSMA/CD Precursors earliest was ALOHA developed for packet radio networks station may transmit a frame at any time if frame is determined invalid, it is ignored maximum utilization of channel about 18% next came slotted ALOHA organized slots equal to transmission time increased utilization to about 37%

5 Lappeenranta University of Technology / JP, PH, AH Pure (unslotted) ALOHA  unslotted Aloha: simpler, no synchronization  when frame first arrives transmit immediately transmit immediately  collision probability increases: frame sent at t 0 collides with other frames sent in [t 0 -1,t 0 +1] frame sent at t 0 collides with other frames sent in [t 0 -1,t 0 +1]

6 Lappeenranta University of Technology / JP, PH, AH Slotted ALOHA Assumptions:  all frames same size  time divided into equal size slots (time to transmit 1 frame)  nodes start to transmit only slot beginning  nodes are synchronized  if 2 or more nodes transmit in slot, all nodes detect collision Operation:  when node obtains fresh frame, transmits in next slot if no collision: node can send new frame in next slot if collision: node retransmits frame in each subsequent slot with prob. p until success

7 Lappeenranta University of Technology / JP, PH, AH Slotted ALOHA Pros  single active node can continuously transmit at full rate of channel  highly decentralized: only slots in nodes need to be in sync  simple Cons  collisions, wasting slots  idle slots  nodes may be able to detect collision in less than time to transmit packet  clock synchronization

8 CSMA/CD Precursors  Carrier Sense Multiple Access (CSMA) station listens to determine in there is another transmission in progress station listens to determine in there is another transmission in progress if idle, station transmits if idle, station transmits waits for acknowledgment waits for acknowledgment if no acknowledgment, collision is assumed and station retransmits if no acknowledgment, collision is assumed and station retransmits utilization far exceeds ALOHA utilization far exceeds ALOHA

9 Lappeenranta University of Technology / JP, PH, AH CSMA collisions collisions can still occur: propagation delay means two nodes may not hear each other’s transmission collision: entire packet transmission time wasted spatial layout of nodes note: role of distance & propagation delay in determining collision probability

10 Nonpersistent CSMA If the medium is idle, transmit; otherwise, go to step 2 If the medium is busy, wait an amount of time drawn from a probability distribution and repeat step 1 Disadvantage: capacity is wasted because the medium will generally remain idle following the end of a transmission even if there are one or more stations waiting to transmit

11 1-persistent CSMA  1-persistent CSMA avoids idle channel time  1-persistent CSMA rules:  1-persistent CSMA rules: 1. if medium idle, transmit; 2. if medium busy, listen until idle; then transmit immediately  1-persistent stations are selfish  if two or more stations waiting, a collision is guaranteed

12 P-persistent CSMA  a compromise to try and reduce collisions and idle time  p-persistent CSMA rules:  p-persistent CSMA rules: 1. if medium idle, transmit with probability p, and delay one time unit with probability (1–p) 2. if medium busy, listen until idle and repeat step 1 3. if transmission is delayed one time unit, repeat step 1  issue of choosing effective value of p to avoid instability under heavy load

13 Value of p?  have n stations waiting to send  at end of tx, expected number of stations is np if np>1 on average there will be a collision if np>1 on average there will be a collision  repeated tx attempts mean collisions likely  eventually when all stations trying to send have continuous collisions hence zero throughput  thus want np<1 for expected peaks of n if heavy load expected, p small if heavy load expected, p small but smaller p means stations wait longer but smaller p means stations wait longer

14 Lappeenranta University of Technology / JP, PH, AH CSMA/CD (Collision Detection) CSMA/CD: carrier sensing, deferral as in CSMA collisions detected within short time collisions detected within short time colliding transmissions aborted, reducing channel wastage colliding transmissions aborted, reducing channel wastage  collision detection: easy in wired LANs: measure signal strengths, compare transmitted, received signals easy in wired LANs: measure signal strengths, compare transmitted, received signals difficult in wireless LANs: received signal strength overwhelmed by local transmission strength difficult in wireless LANs: received signal strength overwhelmed by local transmission strength  human analogy: the polite conversationalist

15 Lappeenranta University of Technology / JP, PH, AH CSMA/CD collision detection

16 Description of CSMA/CD 1.If the medium is idle, transmit; otherwise, go to step 2. 2.If the medium is busy, continue to listen until the channel is idle, then transmit immediately. 3.If a collision is detected during transmission, transmit a brief jamming signal to assure that all stations know that there has been a collision and then cease transmission. 4.After transmitting the jamming signal, wait a random amount of time, referred to as the backoff, then attempt to transmit again (repeat from step 1).

17 CSMA/CD Operation

18 Which Persistence Algorithm?  IEEE 802.3 uses 1-persistent  both nonpersistent and p-persistent have performance problems because of greed of the stations wasted time due to collisions is short with random backoff unlikely to collide on next attempt to send 1-persistent seems more unstable than p-persistent

19 Binary Exponential Backoff  for backoff stability, IEEE 802.3 and Ethernet both use binary exponential backoff  stations repeatedly resend when collide on first 10 attempts, mean random delay doubled on first 10 attempts, mean random delay doubled value then remains same for 6 further attempts value then remains same for 6 further attempts after 16 unsuccessful attempts, station gives up and reports error after 16 unsuccessful attempts, station gives up and reports error  1-persistent algorithm with binary exponential backoff efficient over wide range of loads  backoff algorithm has last-in, first-out effect

20 Collision Detection on twisted pair (star-topology ) activity on more than one port is collision use special collision presence signal on baseband bus collision produces higher signal voltage collision detected if cable signal greater than single station signal signal is attenuated over distance limit to 500m (10Base5) or 200m (10Base2)

21 Lappeenranta University of Technology / JP, PH, AH Ethernet “dominant” wired LAN technology:  cheap $20 for NIC  first widely used LAN technology  simpler, cheaper than token LANs and ATM  kept up with speed race: 10 Mbps – 10 Gbps Metcalfe’s Ethernet sketch

22 IEEE 802.3 MAC Frame Format

23 10Mbps Specification (Ethernet)

24 IEEE 802.3 10-Mbps Physical Layer Medium Alternatives

25 Lappeenranta University of Technology / JP, PH, AH Fast Ethernet  Termi viittaa IEEE:n määrittelemiin 100 Mbps Ethernet-yhteensopiviin lähiverkkotekniikoihin  Käsitellään yhdessä otsikolla 100BASE-T  Erilaisia siirtoteitä käyttäville eri nimet 100BASE-TX käyttää 2 paria johtimia, joko STP tai Cat5 UTP 100BASE-TX käyttää 2 paria johtimia, joko STP tai Cat5 UTP 100BASE-FX käyttää 2 optista kuitua 100BASE-FX käyttää 2 optista kuitua 2 ylempää luokituksen 100BASE-X alla2 ylempää luokituksen 100BASE-X alla 100BASE-T4 käyttää 4 paria Cat3/4/5 UTP 100BASE-T4 käyttää 4 paria Cat3/4/5 UTP yhteensopivuus vanhojen kaapelointien kanssayhteensopivuus vanhojen kaapelointien kanssa

26 100Mbps Fast Ethernet

27 Lappeenranta University of Technology / JP, PH, AH Fast ethernet, 100BASE-X  100BASE-X viittaa tekniikoihin, joissa saadaan yhdellä linkillä (esim. yksittäinen kierretty pari) 100 Mbps yksisuuntainen nopeus 100BASE-TX (parikaapeli) 100BASE-TX (parikaapeli) 100BASE-FX (optinen kuitu) 100BASE-FX (optinen kuitu)  Mainitut 2 tekniikkaa eroavat paitsi siirtotieltään, myös signaloinniltaan T = Twisted pair (kierretty pari), F = fibre (kuitu)

28 100BASE-X  uses a unidirectional data rate 100 Mbps over single twisted pair or optical fiber link  encoding scheme same as FDDI 4B/5B-NRZI 4B/5B-NRZI two physical medium specifications 100BASE -TX uses two pairs of twisted-pair cable for tx & rx STP and Category 5 UTP allowed MTL-3 signaling scheme is used 100BASE -FX uses two optical fiber cables for tx & rx convert 4B/5B-NRZI code group into optical signals

29 Lappeenranta University of Technology / JP, PH, AH Fast Ethernet, 100BASE-T4  100BASE-T4:ssä mahdollisuus käyttää Cat3- kaapeleita, joten määrittely ei vaadi100 Mbps datanopeutta yhdeltä linkiltä 33 1/3 Mbps yhdessä linkissä 33 1/3 Mbps yhdessä linkissä 100 Mbps kaksisuuntaisena vaatii 3 datavirtaa molempiin suuntiin = 6 linkkiä 100 Mbps kaksisuuntaisena vaatii 3 datavirtaa molempiin suuntiin = 6 linkkiä johtimina 4 kierrettyä paria, joista kahden täytyy olla 2-suuntaisia johtimina 4 kierrettyä paria, joista kahden täytyy olla 2-suuntaisia

30 100BASE-T4  100-Mbps over lower-quality Cat 3 UTP takes advantage of large installed base takes advantage of large installed base does not transmit continuous signal between packets does not transmit continuous signal between packets useful in battery-powered applications useful in battery-powered applications  can not get 100 Mbps on single twisted pair so data stream split into three separate streams so data stream split into three separate streams four twisted pairs used four twisted pairs used data transmitted and received using three pairs data transmitted and received using three pairs two pairs configured for bidirectional transmission two pairs configured for bidirectional transmission  use ternary signaling scheme (8B6T)

31 Full Duplex Operation  traditional Ethernet half duplex  using full-duplex, station can transmit and receive simultaneously  100-Mbps Ethernet in full-duplex mode, giving a theoretical transfer rate of 200 Mbps  stations must have full-duplex adapter cards  and must use switching hub each station constitutes separate collision domain each station constitutes separate collision domain CSMA/CD algorithm no longer needed CSMA/CD algorithm no longer needed 802.3 MAC frame format used 802.3 MAC frame format used

32 Mixed Configurations  Fast Ethernet supports mixture of existing 10- Mbps LANs and newer 100-Mbps LANs  supporting older and newer technologies stations attach to 10-Mbps hubs using 10BASE-Tstations attach to 10-Mbps hubs using 10BASE-T hubs connected to switching hubs using 100BASE-Thubs connected to switching hubs using 100BASE-T high-capacity workstations and servers attach directly to 10/100 switcheshigh-capacity workstations and servers attach directly to 10/100 switches switches connected to 100-Mbps hubs use 100-Mbps linksswitches connected to 100-Mbps hubs use 100-Mbps links 100-Mbps hubs provide building backbone100-Mbps hubs provide building backbone connected to router providing connection to WANconnected to router providing connection to WAN

33 Gigabit Ethernet Configuration

34 Lappeenranta University of Technology / JP, PH, AH Gigabit Ethernet  Gigabit Ethernetissä käytössä sama MAC-protokolla (CSMA/CD) ja Ethernet-formaatti kuin 10BASE-T ja 100BASE-T –tekniikoissakin  Gigabit Ethernetiä käytetään yleensä 100 ja 10 Mbps nopeudella toimivien lähiverkkojen runkoverkkoina lisäksi suuria nopeuksia vaativia palvelimia yms. liitetään suoraan GE- kytkimiin lisäksi suuria nopeuksia vaativia palvelimia yms. liitetään suoraan GE- kytkimiin

35 Gigabit Ethernet - Differences  carrier extension at least 4096 bit-times long (512 for 10/100) at least 4096 bit-times long (512 for 10/100)  frame bursting  not needed if using a switched hub to provide dedicated media access

36 Lappeenranta University of Technology / JP, PH, AH Gigabit Ethernet, fyysinen kerros  Gigabit Ethernetissä on määritelty 4 erilaista fyysistä kerrosta 1000BASE-SX (optinen, pieni aallonpituus) 1000BASE-SX (optinen, pieni aallonpituus) 1000BASE-LX (optinen, suuri aallonpituus) 1000BASE-LX (optinen, suuri aallonpituus) 1000BASE-CX (erityissuojattu kierretty pari, max 25 metriä) 1000BASE-CX (erityissuojattu kierretty pari, max 25 metriä) 1000BASE-T (4 paria CAT5 UTP) 1000BASE-T (4 paria CAT5 UTP)  3 ensimmäistä käyttää samaa signaalin koodaustapaa, viimeinen monimutkaisempaa  (taulukko toimintaetäisyyksistä seuraavalla kalvolla)

37 Gigabit Ethernet – Physical

38 Lappeenranta University of Technology / JP, PH, AH 10 Gbps Ethernet  Vaikka Gigabit ethernet –tekniikat ovat vielä varsin uusia, 10 Gbps Ethernet –tekniikat ovat saaneet jo paljon huomiota  Laajentuva Internet ja intranet –liikenne vaatii aina vaan nopeampia yhteyksiä verkkoon liitettävien laitteiden määrät kasvavat verkkoon liitettävien laitteiden määrät kasvavat verkkoliittymät nopeutuvat (esim. 10 Mbps -> 100 Mbps; 56 kbps modeemi -> xDSL) verkkoliittymät nopeutuvat (esim. 10 Mbps -> 100 Mbps; 56 kbps modeemi -> xDSL) kaistaa vaativia sovelluksia (korkealaatuiset videot yms.) kaistaa vaativia sovelluksia (korkealaatuiset videot yms.) web hosting - ja application hosting -liikenne web hosting - ja application hosting -liikenne

39 Lappeenranta University of Technology / JP, PH, AH 10 Gigabit Ethernet  Aluksi 10 Gigabit Ethernetiä käytetään paikallisissa runkoverkkoyhteyksissä  Myöhemmin käytettäneen laajemmin, esim. ”palvelinfarmeissa”, kampusverkoissa, ja myös ISP- käytössä (internet service provider)  Ethernet alkaa kilpailla vanhojen WAN- tekniikoiden kanssa

40 10Gbps Ethernet Configurations

41 Lappeenranta University of Technology / JP, PH, AH 10 Gigabit Ethernet  IEEE 802.3ae, ak, an, ap, aq Kuitu (10GBase-R) Kuitu (10GBase-R) SR, LR, LRM (multimode), ER, ZR (80 km), LX4SR, LR, LRM (multimode), ER, ZR (80 km), LX4 Kupari (10GBase-X/10GBase-T) Kupari (10GBase-X/10GBase-T) CX4, KX4, Base-TCX4, KX4, Base-T WAN (10GBase-W) WAN (10GBase-W)

42 Lappeenranta University of Technology / JP, PH, AH 10 Gigabit Ethernet, fyysinen kerros  Neljä (optista kuitua käyttävää) määritystä: 10GBASE-S (short) – 850 nanometrin aallonpituus, multi-mode, max 300 m 10GBASE-S (short) – 850 nanometrin aallonpituus, multi-mode, max 300 m 10GBASE-L (long) – 1310 nm, single-mode, max 10 km 10GBASE-L (long) – 1310 nm, single-mode, max 10 km 10GBASE-E (extended) – 1550 nm, single-mode, jopa 40 km 10GBASE-E (extended) – 1550 nm, single-mode, jopa 40 km 10GBASE-LX4 1310 nm, single- tai multi-mode, käyttää aallonpituusjakokanavointia (WDM), 4 eri valoa käytössä 10GBASE-LX4 1310 nm, single- tai multi-mode, käyttää aallonpituusjakokanavointia (WDM), 4 eri valoa käytössä

43 Lappeenranta University of Technology / JP, PH, AH 10 Gigabit Ethernet, fyysinen kerros  10GBase - CX4 4 paria 4 paria Max 15 metriä Max 15 metriä  10GBase – KX4 ja KR 1 metri 1 metri  10GBase – T UTP, STP UTP, STP  10GBASE-W Yhteensopivuus OC-192/STM-64 SDH/SONET Yhteensopivuus OC-192/STM-64 SDH/SONET

44 10Gbps Ethernet Options

45 100-Gbps Ethernet  preferred technology for wired LAN  preferred carrier for bridging wireless technologies into local Ethernet networks  cost-effective, reliable and interoperable  popularity of Ethernet technology: availability of cost-effective products availability of cost-effective products reliable and interoperable network products reliable and interoperable network products variety of vendors variety of vendors

46 100Gbps Ethernet

47 Multilane Distribution  multilane distribution: switches implemented as multiple parallel channels switches implemented as multiple parallel channels separate physical wiresseparate physical wires  virtual lanes: if a different number of lanes are actually in use, virtual lanes are distributed into physical lanes in the PMD sublaver form of inverse multiplexing used to achieve the required data rates

48 Multiline Distribution for 100Gbps Ethernet

49 Media Options for 40-Gbps and 100-Gbps Ethernet

50 Multilane Distribution for 100 Gbps Ethernet

51 A VLAN Configuration

52 Summary  traditional Ethernet  high speed LANs emergence  Ethernet technologies CSMA & CSMA/CD media access CSMA & CSMA/CD media access 10Mbps Ethernet 10Mbps Ethernet 100Mbps Ethernet 100Mbps Ethernet 1Gbps Ethernet 1Gbps Ethernet 10Gbps Ethernet 10Gbps Ethernet  multilane distribution  IEEE 802.1Q VLAN standard