In a distributed computing environment, operating system functions are either base or extended services. The base services are part of the...
In a distributed computing environment, operating system functions are either base or extended services. The base services are part of the standard operating system, while the extended services are additional modular software components that are layered on top of the base services. Functionally equivalent extended services are usually provided by more that one vendor. There is no hard to determine what gets bundled with base OS and extended OS. Today’s extended services may become the base services in the future.
Base Services:
A separate task will be assigned to each of the clients the server is designed to support. Task management is best done by multitasking operating system. Multitasking is the natural way to simplify the coding of complex applications that can be divided into a collection of discrete and logically distinct and concurrent tasks.
Servers also require a high level of concurrency within a single program. Server code will run moiré efficiently if tasks are allocated to parts of the same program rather than separate programs. These tasks are called Threads or Coroutines.
Server’s requirements from the operating system are as follows:
1.Task Preemption:
An operating system with preemptive multitasking must allot fixed time slots of execution to each task. Without preemptive multitasking, a task must voluntarily agree to give up the processor before another task can run. It is much safer and easier to write multitasking server programs in environments where the operating system automatically handles all the task switching.
Base Services:
A separate task will be assigned to each of the clients the server is designed to support. Task management is best done by multitasking operating system. Multitasking is the natural way to simplify the coding of complex applications that can be divided into a collection of discrete and logically distinct and concurrent tasks.
Servers also require a high level of concurrency within a single program. Server code will run moiré efficiently if tasks are allocated to parts of the same program rather than separate programs. These tasks are called Threads or Coroutines.
Server’s requirements from the operating system are as follows:
1.Task Preemption:
An operating system with preemptive multitasking must allot fixed time slots of execution to each task. Without preemptive multitasking, a task must voluntarily agree to give up the processor before another task can run. It is much safer and easier to write multitasking server programs in environments where the operating system automatically handles all the task switching.
2.Task Priority:
An operating system must dispatch tasks based on their priority. This feature allows the servers to differentiate the level of service based on their clients’ priority.
3.Semaphores:
An operating system must provide simple synchronization mechanisms for keeping concurrent tasks from bumping into one another when accessing a shared resource. These mechanisms, known as semaphores are used to synchronize the actions of independent server tasks and alert them when a significant error occurs.
4.Interprocess Communication:
An operating system must provide the mechanism that allow independent process to exchange and share data.
5.Local / Remote Interprocess Communication:
An operating system must allow the transparent redirection of interprocess calls to a remote process over a network without the application being aware of it. The extension of interprocess communication across machine boundaries is key to the development of applications where resources and processes can be easily moved across machines.
6.Threads:
These are units of concurrency provided within the program itself. Threads are used to create very concurrent, event-driven server programs. Each waiting event can be assigned to a thread that blocks until the event occurs. In the mean time, other threads can use the CPU cycles to productively perform useful work.
7.Intertask Protection:
The operating system must protect tasks from interfacing with each other’s resources. A single task must not be able to bring down the entire system. Protection also extends to the file system and calls to the operating system.
8.Multi-user High Performance File system:
The file system must support multiple tasks and provide the locks that produce the integrity of data. Server programs typically work on many files at the same time. The file system must support large number of open files without reducing the performance.
9.Efficient Memory Management:
The memory system must efficiently support very large programs and very large data objects. These programs and data objects must be easily swapped to and from disk, preferably in small granular blocks.
10.Dynamically linked Run time extensions:
The operating system services should be extendable. A mechanism must be provided to allow services to grow at run time without recompiling the entire operating system.
Extended Services:
Extended services provide the advanced system software that exploits the distributed potential of networks, provide flexible access to shared information and make the system easier to manage and maintain.
1. Ubiquitous communication:
The operating system extension must provide a rich set of communications protocol stacks that allow the server to communicate with greatest number of platforms. In addition, the server should be able to communicate with other server platforms in case it needs assistance in providing services.
2. Network operating system extensions:
The operating system extensions must provide facilities for extending the file and print services over the network. Ideally the applications should be able to transparently access any remote devices as if they were local.
3. Binary Large Objects:
Images, video, graphics, intelligent documents and database snapshots are about to test the capabilities of our operating systems, databases, and networks. These large objects are called BLOBs, require operating system extensions such as intelligent message streams and object representation formats. Networks must be prepared to move and transport these large BLOBs at high speeds. Databases and file systems must be prepared to store these BLOBs and provide access to them. Protocols are needed for the exchange of BLOBs across systems.
4. Global directories and network yellow pages:
The operating system extensions must provide a way for clients to locate servers and their services on the network using the global directory service. Network resources must be found by the name. Servers must be able to register dynamically their services with the directory provider.
5. Authentication and Authorization Services:
The operating system extensions must provide a way for clients to prove to the server that they are who they claim to be. The authorization system determines if the authorized clients has the permission to obtain a service.
6. System Management:
The operating system extensions must provide an integrated network and system management platform. The system should be managed as a single server or as multiple servers assigned to domains. System management includes services for configuring a system and facilities for monitoring the performance of all elements, generating alerts when things break, distributing and managing software packages on client workstations, checking for viruses and intruders and metering capabilities for pay-as-you-use server resources.
7. Network time:
The operating system extensions must provide a mechanism for clients and servers to synchronize their clocks. This time should be coordinated with some universal time authority.
8. Database and transaction services:
The operating system extensions must provide a robust multi-user database management system. This DBMS should support SQL for decision support and server stored procedures. The programmers create these stored procedures outside the operating system. More advanced functions include Transaction Processing Monitor. (TP Monitor) for managing stored procedures as atomic units of work that execute on one or more servers.
9. Internet Services:
The Internet is a huge area of growth opportunity for servers. Internet services will become standard server features- including HTTP daemons, Secure Sockets Layer (SSL), firewalls and Domain Name Service, HTML based file systems and electronic commerce frameworks.
10. Object Oriented Services:
This is an area where extended services will flourish for a long time. The operating system will provide object broker services that allow any object to interact with any other object across the network. The operating system must also provide object interchange services and object repositories. Client/Server applications of the future will be between communicating objects.
The file system must support multiple tasks and provide the locks that produce the integrity of data. Server programs typically work on many files at the same time. The file system must support large number of open files without reducing the performance.
9.Efficient Memory Management:
The memory system must efficiently support very large programs and very large data objects. These programs and data objects must be easily swapped to and from disk, preferably in small granular blocks.
10.Dynamically linked Run time extensions:
The operating system services should be extendable. A mechanism must be provided to allow services to grow at run time without recompiling the entire operating system.
Extended Services:
Extended services provide the advanced system software that exploits the distributed potential of networks, provide flexible access to shared information and make the system easier to manage and maintain.
1. Ubiquitous communication:
The operating system extension must provide a rich set of communications protocol stacks that allow the server to communicate with greatest number of platforms. In addition, the server should be able to communicate with other server platforms in case it needs assistance in providing services.
2. Network operating system extensions:
The operating system extensions must provide facilities for extending the file and print services over the network. Ideally the applications should be able to transparently access any remote devices as if they were local.
3. Binary Large Objects:
Images, video, graphics, intelligent documents and database snapshots are about to test the capabilities of our operating systems, databases, and networks. These large objects are called BLOBs, require operating system extensions such as intelligent message streams and object representation formats. Networks must be prepared to move and transport these large BLOBs at high speeds. Databases and file systems must be prepared to store these BLOBs and provide access to them. Protocols are needed for the exchange of BLOBs across systems.
4. Global directories and network yellow pages:
The operating system extensions must provide a way for clients to locate servers and their services on the network using the global directory service. Network resources must be found by the name. Servers must be able to register dynamically their services with the directory provider.
5. Authentication and Authorization Services:
The operating system extensions must provide a way for clients to prove to the server that they are who they claim to be. The authorization system determines if the authorized clients has the permission to obtain a service.
6. System Management:
The operating system extensions must provide an integrated network and system management platform. The system should be managed as a single server or as multiple servers assigned to domains. System management includes services for configuring a system and facilities for monitoring the performance of all elements, generating alerts when things break, distributing and managing software packages on client workstations, checking for viruses and intruders and metering capabilities for pay-as-you-use server resources.
7. Network time:
The operating system extensions must provide a mechanism for clients and servers to synchronize their clocks. This time should be coordinated with some universal time authority.
8. Database and transaction services:
The operating system extensions must provide a robust multi-user database management system. This DBMS should support SQL for decision support and server stored procedures. The programmers create these stored procedures outside the operating system. More advanced functions include Transaction Processing Monitor. (TP Monitor) for managing stored procedures as atomic units of work that execute on one or more servers.
9. Internet Services:
The Internet is a huge area of growth opportunity for servers. Internet services will become standard server features- including HTTP daemons, Secure Sockets Layer (SSL), firewalls and Domain Name Service, HTML based file systems and electronic commerce frameworks.
10. Object Oriented Services:
This is an area where extended services will flourish for a long time. The operating system will provide object broker services that allow any object to interact with any other object across the network. The operating system must also provide object interchange services and object repositories. Client/Server applications of the future will be between communicating objects.
