Def ining Dist r ibut ed Syst ems • ”A dist ribut ed syst em is one in which component s locat ed at net worked Dist r ibuer ade syst em comput ers communicat e and coordinat e t heir act ions only by passing messages” C-kurs • ”Om en maskin som du aldrig hört t alas om 5 poäng går ner och det hindrar dig f r ån at t j obba HT-02 så har du et t dist ribuerat syst em” 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 1 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 2 Exemples of DS: I nt er net Exemples of DS: I nt r anet Desktop email server computers print and other servers intranet ☎ ☎ ISP Local area ☎ Web server network ☎ email server backbone print File server other servers satellite link the rest of desktop computer: the Internet server: router/firewall network link: 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 3 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 4 Exemples of DS: Mobile Comput ing Consequences of DS • Concurr ency Internet • No global clock • I ndependent f ailures WAP Host intranet Home intranet Wireless LAN gateway Mobile phone Printer Laptop Host site Camera 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 5 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 6 1
Vad händer i dag? Kur splan • Kur sdelt agar na ska f ör vär va • Kursledning – kunskaper om t eoret iska modeller f ör dist ribuer ade syst em • Kursplan – kunskaper om problem och lösningar i samband med design och konst rukt ion av dist ribuerade syst em • Förra år et • Kur sen behandlar: • Året s kurs – Arkit ekt urmodeller f ör dist r ibuerade syst em – Klient -Server, peer-t o-peer, t r ansakt ioner, t ransparens, • Regist rering namngivning, f elhant ering, resursf ördelning och • I nt rodukt ion t ill Dist ribuerade syst em synkroniser ing – Dat asäkerhet saspekt er i et t bret t per spekt iv – Met oder och t ekniker f ör dat asäker het – Dist r ibuerad progr ammer ing och ”middleware” 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 7 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 8 Kur splan (f or t s) För r a år et • Moment 1, t eoridel, 3 poäng • Flera f öreläsare – Teor ier , met oder , algor it mer och pr inciper • Kursdisposit ion – Bra, men spridda åsikt er • Moment 2, laborat ionsdel, 2 poäng • Gruppövningar – Den var bra – Obligat or iska uppgif t er • Kurslit t erat ur – Bra, men f ormell och t ungläst • Koppling t eori och labbar – Okej , blandat • Tyngd på labbar – Lagom • Lit e högre arbet sbelast ning än snit t et 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 9 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 10 År et s kur s Labor at ioner • Kurslit t erat ur • 3 st ycken • Fokus på – Debat t om säker het – Middlewar e – progr ammer ing – E-handelssyst em, huvudlabben – Säker het – En lit en om EJ B – Dist r ibuerade algor it mer • Tid t ill f örf ogande • Upplägg • Grupper om 2 eller 3, gäller ej debat t en – Föreläsningar • Koppling t ill t eorin – Gr uppövningar • MA336 – Labor at ioner 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 11 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 12 2
Under visning The r est of t oday • Challenges • P edagogisk t anke • Archit ect ural models • Val av present at ionshj älpmedel • Fundament al models • OH-bilder – Källa – I nnehåll – Spr åk • Vad bör man lära sig? 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 13 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 14 Resour ce shar ing: The Web Dist r ibut ed Syst ems • What is dist r ibut ed? • Challenges http://www.google.comlsearch?q=kindberg www.google.com – Dat a – Het erogeneit y Browsers Web servers – Comput ing power – Openness – Services – Securit y Internet www.cdk3.net http://www.cdk3.net/ – Ent it ies – Scalabilit y – Securit y – Failur e handling www.w3c.org – Name space – Concurr ency http://www.w3c.org/Protocols/Activity.html File system of Protocols – Time – Transparency www.w3c.org Activity.html 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 15 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 16 Het er ogeneit y Openness • Applies t o • Middlewar e - sof t war e • Ext ended and re- • Open syst ems; layer t hat provides implement ed – Net works – Key int erf aces are pr ogr amming published – Comput er hardwar e • Ver y impor t ant in t he abst r act ion and mask • Open dist r ibut ed – Operat ing syst ems indust r y het erogeneit y syst ems can be – Progr amming languages • RFC (r equest s f or – I mplement at ions by • Mobile code - code – const ruct ed f rom comment s) dif f erent developers het erogeneous t hat can be sent f r om – You’ll use it in your hardware and sof t ware. one comput er t o work. I n t his course. anot her And probably in t he rest of your lif e 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 17 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 18 3
Scalabilit y Scalabilit y • Cont r olling t he cost of physical r esour ses • Cont r olling t he perf or mance loss • P r event ing sof t war e resour se r unning out Date Computers Web servers Percentage • Avoiding per f ormance bot t lenecks 1,776,000 130 0.008 1993, July 1995, July 6,642,000 23,500 0.4 Date Web servers Computers 1997, July 19,540,000 1,203,096 6 188 0 1999, July 56,218,000 6,598,697 12 1979, Dec. 1989, July 130,000 0 1999, July 56,218,000 5,560,866 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 19 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 20 Failur e handling Tr anspar ency Access transparency : enables local and remote resources to be accessed using identical operations. • Techniques f or dealing wit h f ailures Location transparency : enables resources to be accessed without knowledge of their – Det ect ing f ailures location. Concurrency transparency : enables several processes to operate concurrently using shared – Masking f ailur es resources without interference between them. Replication transparency : enables multiple instances of resources to be used to increase – Tolerat ing f ailur es reliability and performance without knowledge of the replicas by users or application – Recovery f rom f ailures programmers. Failure transparency : enables the concealment of faults, allowing users and application – Redundancy programs to complete their tasks despite the failure of hardware or software components. Mobility transparency : allows the movement of resources and clients within a system without affecting the operation of users or programs. Performance transparency : allows the system to be reconfigured to improve performance as loads vary. Scaling transparency : allows the system and applications to expand in scale without change to the system structure or the application algorithms. 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 21 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 22 Syst em Models Sof t war e and har dwar e layer s • Ar chit ect ur al models • Fundament al models Applications, services – Concerned wit h t he – Concerned wit h a more placement s of it s par t s f ormal descript ion of and t he relat ionships t he propert ies t hat are bet ween t hem. common in ar chit et ur al Middleware models – Examples – Models • Client -ser ver • I nt er act ion model • Peer -t o-peer • Failur e model Operating system • Secur it y model Platform Computer and network hardware 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 23 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 24 4
Client -ser ver Mult iple - ser ver s Service Server Client Server invocation invocation Client result result Server Server Client Key: Process: Computer: Client Server 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 25 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 26 Web pr oxy ser ver Peer pr ocesses Application Application Web Coordination Coordination Client code code server Proxy server Web Client server Application Coordination code 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 27 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 28 Mobile code - web applet s Thin client s a) client request results in the downloading of applet code Compute server Network computer or PC Web Client server Applet code Application Thin network Process b) client interacts with the applet Client Web Client Applet server 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 29 3/9 - 02 Distribuerade system - Jonny Pettersson, UmU 30 5
Recommend
More recommend
