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7/28/2019 Distributed System Examples
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NJIT
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Distributed SystemExamples
Introduction to key topics in
Distributed Computing
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Warning
This is a difficult course, because it requires youto learn how to configure heterogeneouslanguages and environments.
You will work in teams to solve problems. Theinstructor cannot provide individual technicalsupport. All technical support will be on Moodle,
with students answering each others questions. You should be familiar with Java, and have
some knowledge of C or C++.
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The Fourth Wave
Starting about 2000, there has been a movetoward parallel computing using inexpensive
blade servers, often using Linux. The next slide give an example from a
company named Cassat formed byspecialists from the Cray supercomputercompany. Note that the example gives 7times the performance for one tenth the cost!
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The Fourth Wave
Cassatts program, Collage sits atop a pool of
servers and shifts processing power on the fly
Pharmaceutical giant Pfizer became a Cassat
customer after a demo in which Collage enabled a$300,000 cluster of IBM blade servers, running 24ordinary Intel microprocessors, to crunch through anOracle data warehousing job in 45 minutes.Previously Pfizer had run the job on a $3 million Sunmachine. It took five and a half hours. 11Forbes magazine, September 18, 2006, page 106.
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Subsequent Developments
Key developments since 1998 include theFurther development of the Internet,
including portable Internet technologiessuch as WiFi and Bluetooth, as well as thegrowth of Peer-to-Peer systems starting
with the great popularity of Napster.
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Not about technology
The Distributed Systems marketplace wasdriven by technology until 2000. That is
no longer true. Now it is driven bybusiness value.
Knowing the latest and greatest
technology will no longer get you a job.Now you have to deliver increased profitand/or lower cost to a company.
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Distributed Computing -Strategic Factors
End-User
Organization
Flexibility
Real-Time Access
to information
ScalabilityFaster Development
And deployment of
Business Solutions
Code
Reusability
Interoperability
Portability
Reduced
Complexity
Increased
Complexity
Lack of
ManagementTools
Changing
Technology
Personalized Environment
Predictable Response
Location IndependencePlatform Independence
Applic
ationDeveloper
SystemAdministr
ator
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Distributed ComputingReference Model
Network
Managem
ent
Mana
gement
AndS
upport
Enterprise Systems:
Perform enterprise activities
Application Systems:
Support enterprise systems
Distributed Computing platform
Application Support Services (OS,
DB support, Directories, RPC)
Communication Network Services
(Network protocols,Physical devices)
Hardware
Interoper
ability
P
ortability
Integration
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Expanded Model
Common Network Services
Network protocols & interconnectivityOSI
ProtocolsTCP/IP SNA
Distributed Computing Platform
Application Support Services
C/S SupportDist. Data
Trans. Mgmt.Distributed
OS
Application Systems:
User
Interfaces
Processing
Programs
Data files &
Databases
Enterprise Systems:
.Engineering Systems .Manufacturing
.Business Systems .Office Systems
Network
Manag
ement&
Manageme
nt
Support
Interoperability
Portability
Integration
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The Internet
The Internet is a vast interconnectedcollection of computer networks of many
different types. [Coulouriset al, p.3] It is the dominant distributed system at the
current time, although intranets, the public
switched telephone network (PSTN) andother networks are still important.
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Effect of the Web
Some industries have already beenchanged beyond all recognition by the
web. Nearly all new car buyers haveshopped the web first. That hasdramatically changed the balance of
power between dealer and customer. Thestock brokerage and travel businesseshave also been impacted dramatically.
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Mobile and UbiquitousComputing
Small portable devices have beenintegrated into information systems with
wireless networking. These devices include laptop computers,
handheld devices such as personal digital
assistants, cell phones, wearable deviceslike smart watches, and devicesembedded in appliances and automobiles.
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Resource Sharing and theWeb
Distributed Systems began with thesharing of printers and files. Today, we
take for granted the ready access to vastquantities of information. While theInternet may be little more than the ability
to share information from a vast collectionof files, the speed, search capabilities, andtools have changed much of our society.
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Web Portable Protocols
KISS
Platform Independent
Read-only; first generation Internet as backbone
URL Global naming
HTTP RPC-Like protocol HTML documents
Web browsers as universal clients
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A Web Client/Server Interaction
Simple Web Client/Server Interaction
1. Select target URL
2. Browser send HTTP request to server3. Server processes request
a. Well-known port 80 for HTTP
b. Send back requested HTML file; close
connection4. Browser interprets HTML commands
If HTML type, displays page.
Otherwise, launches helper
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URL (Uniform Resource Locator)
Naming scheme + how to get to resource
Protocol scheme
HTTP, Gopher, News, FTP, Mailto, nntp, Telnet
HTTP is native Web protocol
Servername
Internet host domain name or raw IP address
Port number (or default)
HTTP = 80; Gopher = 70; FTP = 21
Path to resource
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HTTP:
Web's RPC on top of TCP/IP
Stateless protocol
Separate TCP connection to download each BLOBdocument with 5 inline images = 6 connections
Typed data using RPC
Negotiate representation for each connection
MIME-like content minus Internet Mail
MIME's 7 types: Plain text, audio, video, stillimages, message, multipart message, application-specific data
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CGI: Common Gateway Interface
Supported by most Web servers Appropriate for small amounts of dynamic content
E.g. mostly static web pages plus phone number
lookup Unacceptable for highly interactive web sites
Each CGI request starts a processstartup delayProcess-per-request requirement: overloads theserver if many requests
Now mostly obsolete, but important as anillustration of emerging need for efficiency.
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XML: Structured Data in aText File
l Spreadsheets, address books,configuration parameters, financialtransactions, product catalogs
l XML defines a set of rules andconventions for designing text formats forsuch data
l Easy to generate and read by computer
l Extensible
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Role of XML
Applications built on differenttechnologies can communicate via XML.
New integration tools and integrationservers capitalize on emergence of XMLas an integration technology.
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Challenges
Heterogeneity
Openness
Security Scalability
Failure Handling
Concurrency
Transparency
The concernsintroduced at the endof chapter one in
Coulouris et alwill bemajor topics fordiscussion in futurelectures in thiscourse.
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Distributed System Challengesfrom a Systems Perspective
Communication
Processes
Naming Synchronization
Data Storage/Access
Consistency/Replication Fault Tolerance
Security
API and Transparency
Scalability/Modularity
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Distributed System Challengesfrom an Algorithmic Perspective
Execution models andFrameworks
Distributed Graph andRouting Algorithms
Time and Global States
Synchronization and
Coordination
Group communicationand multicasting
Monitoring distributedevents
Design and verificationtools
Distributed debugging
Replication and
consistency
Web design cache,search, scheduling
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More Challenges from anAlgorithmic Perspective
Distributed sharedmemory
Reliable and faulttolerant systems
Load balancing
Real time scheduling
Performance
These are broad topics,and each of them mayhave several sub-topics. For example,Distributed sharedmemory is concerned
with wait-freealgorithms, mutualexclusion, andconsistency models.
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