Distributed Operating System / Distributed System : BE - [Comp & IT]

    An important and very interesting subject introduced in the final year, final semester of the Engineering Curriculum. The subject requires Operating System as a pre-requisite. Syllabus for Computer & IT differs in a small perspective. The Syllabus for Computer Engineering is as follows: 

Unit I

Fundamentals – Fundamentals of OS, What is Distributed System? Evolution of Distributed Computing System, Distributed Computing System Models , Distributed Computing gaining popularity Issues in Designing Distributed System, Introduction to Distributed Computing Environment, Protocols for Distributed System, Network, Interprocess Communication, Issues in Interprocess Communication

Message Passing - Introduction , Desirable features of good message passing system, Issues in IPC by Message passing, RPC, RMI Synchronization, Buffering, Multidatagram messages, Encoding and decoding of message data, Process addressing, Failure Handling, Group communication, Case Study: RMI, CORBA. Advances in Distributed Systems

Unit II

Architecture of Distributed System – Introduction, Motivations, Concepts of Distributed System, Process Synchronization, System architecture types, Distributed operating system, NOS, Middleware Communication Networks, Communication primitives, Architectural models of Distributed System

Synchronization

Introduction, Inherent Limitations of a Distributed System, Lamport’s logical clock, Vector clock, Global states, Concept of Process, Process Migration, Threads Clock synchronization, Event ordering, Mutual Exclusion, Deadlock, Election Algorithms

Issues in Designing Distributed System and role of middleware in Distributed System

Unit III

Distributed Mutual Exclusion – Introduction, Classification of mutual exclusion algorithms, Preliminaries, A simple solution to distributed mutual exclusion, non token based algorithms, Ricart Agrawala algorithm, Token based algorithms, Suzuki Kasami’s broadcast algorithms

Distributed Deadlock detection – Introduction, Preliminaries , Deadlock handling strategies , Issues in deadlock detection and resolution, Control organizations for distributed deadlock detection, Centralized deadlock detection algorithms, Distributed deadlock detection algorithms, Avoidance and Prevention algorithms, Hierarchical deadlock detection algorithms

Agreement Protocols – Introduction, System Model, Classification of agreement problems, Solutions to the Byzantine Agreement problem, Applications of Agreement algorithm, Distributed Synchronization and Agreement Protocol, Concepts of Mutual exclusion, Deadlock Solution to Distributed Mutual exclusion

Unit IV

Distributed Resource Management, Concepts of File System, Scheduling Algorithms

Distributed File System :Introduction , Architecture, Mechanisms for building distributed file system, Design issues, Case studies, Log structured file systems, Google FS

Distributed Shared Memory – Introduction, Architecture and Motivation, algorithms for implementing DSM, Memory Coherence, Coherence protocols, Design issues, Case studies-Linda

Distributed Scheduling – Introduction, Motivation, Issues in load distribution, Components of load distributing algorithms, Stability, Load distributing algorithms, Performance Comparison, Selecting a suitable load sharing algorithms, Requirements for load distributing, Load sharing policies, Task migration

Distributed File System: Comparisons

Unit V

Recovery and Security mechanism, Concepts of Database system Security, Basic concepts of Recovery and Types of Failures Recovery – Introduction, Basic concepts, Classification of failures, Backward and forward error recovery, Backward error recovery, Recovery in concurrent systems, Consistent set of checkpoints, Synchronous and Asynchronous check pointing and recovery

Fault tolerance – Introduction, Issues, Atomic actions and committing, Commit Protocols, Non blocking Commit protocols, Voting protocols, Majority based Dynamic Voting protocol, Dynamic vote, Reassignment protocols, Failure Resilient Processes, Reliable communication, Case studies-BAR Fault Tolerance, Targon/32 UNIX

Access and Flow control – Introduction, Preliminaries, Access matrix Model, Implementations of Access Matrix, Safety in Access matrix model, advanced models of protection, Case studies-Unix OS

Distributed Fault tolerance and Security, Advances in Recovery and security mechanisms

Unit VI

Emerging Trends in Distributed System, Concepts of Cluster, Concepts of Grid Computing

Grid Computing

Introduction to GRID Computing, How Grid Computing Works, Grid Middleware, Grid Architecture, Types of Grids Grid Computing Applications, Simulators

SOA: Basic SOA Definition, Overview of SOA, SOA and Web Services, Service Oriented Grid, SOA Design and Development, Advantages and Future of SOA

Grid computing, Cloud and SOA

Syllabus for IT Engineering is as follows :

Unit I: Introduction

Introduction to Distributed Systems: Goals, Architecture, Examples of Distributed Systems, Characteristics, Hardware and Software Concepts, Design Issues, Challenges.

System Models: Architectural models, fundamental models and Failure Model.

Unit II :

Inter-process Communication and Coordination

Message Passing Communication: Communication Primitives, Message Synchronization and Buffering, Pipe, Pipe and Socket APIs, Group Communication, Multicasting Remote Procedural Call: Basic Operation, Implementation and Call Semantics,

Failure Handling, LRPC

Object Oriented Distributed Computing Technologies – Basics, design issues of various technologies like RMI and CORBA with semantics and executions.

Unit III: Synchronization and Election

Clock Synchronization: Logical and Physical Clocks, Algorithms and Uses

Mutual Exclusion: Centralize, Distributed and Token Ring Algorithms, Comparison

Logical Clocks: Lamport’s Logical Clock, Vector Clocks

Global State: Needs, Properties and Various Global States

Election Algorithm: Bully and Ring Algorithm

Unit IV: Distributed File Systems

Introduction, Characteristics, File Service Architecture Sun Network and CODA File System: Overview of NFS, Communication, Processes, Naming, Synchronization, Consistency and Replication, Fault Tolerance and Security

Naming Services: Case Study of Global Name Service and X.500 Directory Service

Unit V: Distributed Shared Memory

Replication: Introduction, Reasons for Replication, Object Replication and Scaling Technique

Distributed Shared Memory: Design and Implementation Issue;

Data Centric Consistency Models - Strict, Sequential, Casual, PRAM, Weak, Release, Entry

Client-Centric Consistency Models: Eventual, Monotonic Reads, Monotonic Writes, Read Your Writes, Writes Follow Reads

Unit VI: Fault Tolerant and Recovery

Fault Tolerance: Concepts, Failure Models, Failure Masking by Redundancy

Process Resilience: Design Issues, Failure Masking and Replication, Agreement in Faulty Systems

Recovery: Introduction, Check-pointing, Message Logging – Synchronous and Asynchronous, Adaptive Logging 

Books for Download :

Distributed Systems – Concept and Design

Coulouris, Dollimore, Kindberg

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File Type : PDF

Size : 36.09 MB

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Distributed Systems – Principles andParadigms

Tanenbaum , Steen

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File Type : PDF

Size : 9 MB

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Distributed Systems Architecture

Puder,Romer,Pilhofer

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File Type : PDF
Size : 1.8 MB

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Distributed Systems
Andrew S. Tannenbaum, Marteen Steen

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File Type : PDF
Size : 32MB

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Video Lectures

Introduction  to Distributed System

 ..... a few more comming soon

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How Denial of Service Attack Works?

How a "denial of service" attack works

     In a typical connection, the user sends a message asking the server to authenticate it. The server returns the authentication approval to the user. The user acknowledges this approval and then is allowed onto the server.

    

         In a denial of service attack, the user sends several authentication requests to the server, filling it up. All requests have false return addresses, so the server can't find the user when it tries to send the authentication approval. The server waits, sometimes more than a minute, before closing the connection. When it does close the connection, the attacker sends a new batch of forged requests, and the process begins again--tying up the service indefinitely.

Typical connection

"Denial of service" attack

How to block a "denial of service" attack

    One of the more common methods of blocking a "denial of service" attack is to set up a filter, or "sniffer," on a network before a stream of information reaches a site's Web servers. The filter can look for attacks by noticing patterns or identifiers contained in the information. If a pattern comes in frequently, the filter can be instructed to block messages containing that pattern, protecting the Web servers from having their lines tied up.

Distributed Denial of Service Attacks

       Sometimes a  attacker uses a network of zombie computers to sabotage a specific Web site or server. The idea is pretty simple -- the attacker tells all the computers on his botnet to contact a specific server or Web site repeatedly. The sudden increase in traffic can cause the site to load very slowly for legitimate users. Sometimes the traffic is enough to shut the site down completely. We call this kind of an attack a Distributed Denial of Service (DDoS) attack.

   Some particularly tricky botnets use un-corrupted computers as part of the attack. 

Here's how it works:

• The attacker sends the command to initiate the attack to his zombie army. 
• Each computer within the army sends an electronic connection request to an innocent computer called a reflector. 
• When the reflector receives the request, it looks like it originates not from the zombies, but from the ultimate victim of the attack. 
• The reflectors send information to the victim system, and eventually the system's performance suffers or it shuts down completely as it is inundated with multiple unsolicited responses from several computers at once.

   From the perspective of the victim, it looks like the reflectors attacked the system. From the perspective of the reflectors, it seems like the victimized system requested the packets. The zombie computers remain hidden, and even more out of sight is the cracker himself.

The list of DDoS attack victims includes some pretty major names. Microsoft suffered an attack from a DDoS called MyDoom. Crackers have targeted other major Internet players like Amazon, CNN, Yahoo and eBay. The DDoS names range from mildly amusing to disturbing:

• Ping of Death - bots create huge electronic packets and sends them on to victims
• Mailbomb - bots send a massive amount of e-mail, crashing e-mail servers
• Smurf Attack - bots send Internet Control Message Protocol (ICMP) messages to reflectors, see above illustration
• Teardrop - bots send pieces of an illegitimate packet; the victim system tries to recombine the pieces into a packet and crashes as a result

     Once an army begins a DDoS attack against a victim system, there are few things the system administrator can do to prevent catastrophe. He could choose to limit the amount of traffic allowed on his server, but this restricts legitimate Internet connections and zombies alike. If the administrator can determine the origin of the attacks, he can filter the traffic. Unfortunately, since many zombie computers disguise (or spoof) their addresses, this isn't always easy to do.

Demonstration of DDOS Attack

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