distributed system
CHUKA
UNIVERSITY
DEPARTMENT OF COMPUTER SCIENCE
COMP 414:DISTRIBUTED ASSIGNMENT 1, DUE DATE 31/01/2014
(a) With examples describe Access, Location and Migration transparency in a distributed system. (4mks)
Access Transparency: Clients should be unaware of the distribution of the files. The files could be present on a totally different set of servers which are physically distant apart and a single set of operations should be provided to access these remote as well as the local files. Applications written for the local file should be able to be executed even for the remote files. The examples illustrating this property are the File system in Network File System (NFS), SQL queries, and Navigation of the web.
Location Transparency: Clients should see a uniform file name space. Files or groups of files may be relocated without changing their pathnames. A location transparent name contains no information about the named object’s physical location. This property is important to support the movement of the resources and the availability of services. The location and access transparencies together are sometimes referred as Network transparency.
The examples are File system in NFS and the pages of the web. Migration Transparency: This transparency allows the user to be unaware of the movement of information or processes within a system without affecting the operations of the users and the applications that are running. This mechanism allows for the load balancing of any particular client, which might be overloaded. The systems that implement this transparency are NFS and Web pages.
(b) With examples describe what Middleware is.(2 mks)
Middleware is systems software that resides between the applications and the underlying operating systems, network protocol stacks, and hardware. Its primary role is to;
1. Functionally bridge the gap between application programs and the lower-level hardware and software infrastructure in order
UNIVERSITY
DEPARTMENT OF COMPUTER SCIENCE
COMP 414:DISTRIBUTED ASSIGNMENT 1, DUE DATE 31/01/2014
(a) With examples describe Access, Location and Migration transparency in a distributed system. (4mks)
Access Transparency: Clients should be unaware of the distribution of the files. The files could be present on a totally different set of servers which are physically distant apart and a single set of operations should be provided to access these remote as well as the local files. Applications written for the local file should be able to be executed even for the remote files. The examples illustrating this property are the File system in Network File System (NFS), SQL queries, and Navigation of the web.
Location Transparency: Clients should see a uniform file name space. Files or groups of files may be relocated without changing their pathnames. A location transparent name contains no information about the named object’s physical location. This property is important to support the movement of the resources and the availability of services. The location and access transparencies together are sometimes referred as Network transparency.
The examples are File system in NFS and the pages of the web. Migration Transparency: This transparency allows the user to be unaware of the movement of information or processes within a system without affecting the operations of the users and the applications that are running. This mechanism allows for the load balancing of any particular client, which might be overloaded. The systems that implement this transparency are NFS and Web pages.
(b) With examples describe what Middleware is.(2 mks)
Middleware is systems software that resides between the applications and the underlying operating systems, network protocol stacks, and hardware. Its primary role is to;
1. Functionally bridge the gap between application programs and the lower-level hardware and software infrastructure in order