Summary on Distributed System Concepts and Architectures Vijay Neelakandan

What is Distribution system? A distributed system is a collection of autonomous computers linked by a computer network that appears to the user as a single computer A distributed system is a collection of autonomous computers linked by a computer network that appears to the user as a single computer

Why distributed system? Resource sharing Specialized hardware Specialized hardware Data/Database Data/Database Computation speedup Partitioning computations allowing concurrent processing Partitioning computations allowing concurrent processing Load balancing Load balancingReliability In event of system resource failure, shift its processing load to another similar resource

Distributed System Categories? Multiple computer systems collaborating to deliver a single application Multiple applications collaborating together as a system Architecture depends on the category.

Disadvantages of Distributed Systems Difficulties of developing distributed software Networking Problems Security problems[B. Karp, S. Hailes]

Goals Access Transparency Local and remote resources are accessed using identical operations Location Transparency Users cannot tell where hardware and software resources (files, CPU's) are located; the name of the resource shouldn't encode the location of the resource

Goals Contd.. Migration(Mobility) Transparency Resources should be free to move from one location to another without having their names changed Failure Transparency Applications should be able to complete their task despite failures occurring in certain parts of the system

Goals contd.. Concurrency Transparency The users will not notice the existence of other users in the system(even if they access the same resources) Performance Transparency Load variation should not lead to performance degradation. This could be achieved by automatic reconfiguration as response to changes of the load

Goals Contd.. Replication Transparency The system is free to make additional copies of files and other resources (for purpose of performance and/or reliability), without the users noticing. Example: several copies of a file; at a certain request that copy is accessed which is closest to the client The system is free to make additional copies of files and other resources (for purpose of performance and/or reliability), without the users noticing. Example: several copies of a file; at a certain request that copy is accessed which is closest to the client

What is an Operating System??? A program acting as an intermediary between the user and the hardware. Purpose: To provide an environment, where user can execute programs in a convenient and efficient manner. The operating systems provides certain services to the users to make their tasks easier.

Operating System Design Goals EfficiencyFlexibilityConsistencyRobustness

Why Operating System Services? OS provides an environment for the executions of the programs. OS provides an environment for the executions of the programs. Services are provided for the convenience of the programmer, to make the programming task easier. Services provided differ from one operating system to another operating system.

Services provided by the operating system? Program Execution I/O Operations File-system manipulation Communications Error Detection Resource Allocation AccountingProtection

Communication Network Protocol

Application Layer This layer provides application services for file transfers, , and other network software services. Telnet and FTP are applications that exist entirely in the application level. This layer provides application services for file transfers, , and other network software services. Telnet and FTP are applications that exist entirely in the application level. file transfers networksoftwareTelnetFTPapplicationsfile transfers networksoftwareTelnetFTPapplications

Transport Layer This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer. This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer.hosts flow controldata transferhosts flow controldata transfer

Design Issues of Distributed Systems OpennessSecurity Reliability and fault tolerance ScalabilityConcurrency Achieving Transparency[A. S. Tanenbaum]

Flexibility The flexible operating systems are taken to be those whose designs have been motivated to some degree by the desire to allow the system to be tailored, either statically or dynamically, to the requirements of specific applications or application domains.

Reliability In general, reliability (systemic def.) is the ability of a person or system to perform and maintain its functions in routine circumstances, as well as hostile or unexpected circumstances. Reliability is generally considered important by end users

Distributed Computing Environment  The DCE is a software that supplies a framework and toolkit for developing client/server applications. The framework includes a Remote Procedure Call (RPC) mechanism, a naming (directory) service, a time service, an authentication service, an authorization service and a Distributed File System.  DCE runs on all major computing platforms and is designed to support distributed applications in heterogeneous hardware and software environments. DCE is a key technology in three of today's most important areas of computing: security, the World Wide Web, and distributed objects. securityWorld Wide Webdistributed objectssecurityWorld Wide Webdistributed objects

DCE

RESEARCH

Distributed Wireless Communication System by by Shidong Zhou Ming Zhao Xibin Xu Jing Wang Yan Yao Tsinghua Univ., Beijing, China Shidong Zhou Ming Zhao Xibin Xu Jing Wang Yan Yao Tsinghua Univ., Beijing, China

Abstract The Distributed wireless communication system is the new architecture for future public wireless access. This can be done with the help of distributed antennas, distributed processors, and distributed control.

Abstract contd.. With distributed antennas, the system capacity can be expanded through dense frequency reuse, and the transmission power can be greatly decreased. With distributed processors control, the system capacity can be increased by co-processing of signals to and from multiple antennas.

How Load Balancing Done? By the simulation of the distributed time-driven algorithm, the efficiency of load balancing and the division method are proved to be acceptable. Load balancing can also be done by Distributed private network in DWCS.

References 1)Distributed Wireless communication system er= er= er= er= )How load balancing done? 3)Distributed Cache for wireless communication system

References 4)Distributed Operating Systems & Algorithms, Randy Chow and Theodore Johnson, Addison Wesley, ) Distributed Systems principles and paradigms by Andrew S. Tanenbaum, Maarten van Steen, ) Ge, Z.; Figueiredo, D.R.; Sharad Jaiswal; Kurose, J.; Towsley, D.; Modeling peer-peer file sharing systems, INFOCOM Twenty-Second Annual Joint Conference of the IEEE Computer and Communications Societies. IEEE Volume 3, 30 March-3 April 2003 Page(s): vol.3

THANK YOU