Distributed Systems Bina Ramamurthy 12192021 From the CDK

Distributed Systems Bina Ramamurthy 12/19/2021 From the CDK text 1

Introduction Distributed system is the one in which hardware and software components at networked computers communicate and coordinate their activity only by passing messages. Examples: Internet, intranet and mobile computing systems. 12/19/2021 From the CDK text 2

Major Challenges Heterogeneity of components Openness n n interfacing and addition and removal of components Security Scalability : ability to work well when number of users increases n n n Failure handling Concurrency Transparency 12/19/2021 From the CDK text 3

Internet is a very large distributed system. Interconnection of a collection of heterogeneous networks of computers. Services: world wide web (www), file transfers (ftp), email, etc. 12/19/2021 From the CDK text 4

A typical portion of the Internet intranet % ISP % % % backbone satellite link desktop computer: server: network link: 12/19/2021 From the CDK text 5

A typical intranet 12/19/2021 From the CDK text 6

Mobile and Ubiquitous computing Technological advances in device miniaturization and wireless networking have led to integration of small and portable devices into distributed systems. n Laptop computers, hand held devices, wearable devices, appliances such as washing machines and refrigerators. What are some of the issues here? 12/19/2021 From the CDK text 7

Portable and handheld devices in a distributed system 12/19/2021 From the CDK text 8

Client/Server: refers to a process on a networked computer that accepts requests from other (local or remote) processes to perform a service and responds appropriately. Client: requesting process in the above is referred to as the client. Request and response are in the form of messages. Client is said to invoke an operation on the server. Many distributed systems today are constructed out of interacting clients/servers. 12/19/2021 From the CDK text 9

Web servers and web browsers www. google. com http: //www. google. comlsearch? q=kindberg Browsers Web servers www. cdk 3. net Internet http: //www. cdk 3. net/ www. w 3 c. org File system of www. w 3 c. org Protocols http: //www. w 3 c. org/Protocols/Activity. html Reading assignment: Section 1. 3. 1 12/19/2021 From the CDK text 10

Computers in the Internet Date 1979, Dec. 1989, July 1999, July 12/19/2021 Web servers Computers 188 0 130, 000 56, 218, 000 0 5, 560, 866 From the CDK text 11

Transparencies • Access transparency: enables local and remote resources to be accessed using identical operations. • Location transparency: enables resources to be accessed without knowledge of their location. • Concurrency transparency: enables several processes to operate concurrently using shared resources without interference between them. • Replication transparency: enables multiple instances of resources to be used to increase reliability and performance without knowledge of the replicas by users or application programmers. • Failure transparency: enables the concealment of faults, allowing users and application 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. • Performance transparency: allows the system and applications to expand in scale without change to the system structure or the application algorithms. 12/19/2021 From the CDK text 12