NOSs are evolving from being a collection of independent workstations, able to communicate via a shared file system, to become real distribu...
NOSs are evolving from being a collection of independent workstations, able to communicate via a shared file system, to become real distributed computing environments that make the network transparent to users.
Transparency:
Transparency:
Transparency means hiding the network and its servers from the users and even the application programmers. Some types of transparencies are:
- Location Transparency: Users should not have to be aware of the location of a resource. Users need not include the location information in the resource’s name.
- Namespace Transparency: Users should be able to use the same naming conventions to locate any resource on the network.
- Logon Transparency: Users should be able to provide a single password that works on all servers and for all services on the network.
- Replication Transparency: Users should be able to tell how many copies of a resource exist. If a naming directory is shadowed on many machines, it is up to the NOS to synchronize updates and take care of locking issues.
- Local/Remote access transparency: Users should be able to work with any resources on the network as if it were on the local machine. The NOS must handle access controls and provide directory services.
- Distributed time transparency: Users should not see any time differences across servers. The NOS must synchronize the clocks on all servers.
- Failure transparency: Users must be shielded from network failures. The NOS must handle retries and session reconnects. It must also provide some levels of service redundancy for fault tolerance.
- Administration transparency: Users should have to deal with a single-system management interface. NOS must be integrated with the local management services.
