03-07-2013, 12:39 PM
Network Operating Systems
Network Operating.ppt (Size: 511.5 KB / Downloads: 27)
INTRODUCTION
The NOS is similar to a computer operating system like Windows and Linux but contains an array of utilities and programs that ensure data is transmitting to the correct user, computer, and other devices.
It includes special functions for connecting computers and devices into a local-area network (LAN). Some operating systems, such as UNIX and the Mac OS, have networking functions built in. The term network operating system, however, is generally reserved for software that enhances a basic operating system by adding networking features. Novell Netware, Microsoft Windows Server, and Windows NT are examples of an NOS.
NOS
Network operating systems (NOSs) distribute their functions over a number of networked computers.
It then adds functions that allow access to shared resources by a number of users concurrently.
NOS computers take on specialized roles to accomplish concurrent access to shared resources.
Client systems contain specialized software that allows them to request shared resources that are controlled by server systems responding to a client request.
NOS- The transparent illusion
NOS provides a real distributed computing environment that make the network transparent to user.
Transparency in the sense:
Location: one should not have to be aware of the location of the resource.
Namespace: one should be able to use the same naming conventions to locate any resource.
Logon: one should be able to use a single password that works on all servers and for all services.
Distributed time: one should not see any time difference across servers.
Failure: you must be shielded from network failures.
Administration: NOS must be integrated with the local management services.
NOS Server Hardware
NOS servers are large systems with additional memory to support multiple tasks that are all active, or resident, in memory at the same time.
Additional disk space is also required on servers to hold shared files and to function as an extension to the internal memory on the system.
Because a NOS depends on the continuous operation of its servers, the extra hardware components justify the additional expense.
LDAP
Stands for Lightweight Directory Access Protocol.
LDAP is a scaled-down implementation of the X.500 standard. . The X.500 protocols sit on top of the session/presentation layer of the OSI stack, whereas the LDAP runs on top of TCP.
The idea was to provide a lightweight PC client implementation that could access X.500 directory servers over the internet.
Active Directory and eDirectory are based on LDAP.
Netscape’s Directory Server was the first wide implementation of LDAP.
Most LDAP directories use a single master method of replication. Changes are made to the master databases and then propagated out to subordinate databases. The disadvantage of this scheme is that it has a single point of failure.
Objects within an LDAP directory are referenced using the object’s DN (Distinguished Name). The DN consists of the RDN (Relative Distinguished Name) appended with the names of ancestor entries