Chapter 10 - Management of Network Functions

1. Chapter 10 - Management of Network Functions CIS106 Microcomputer Operating Systems Gina Rue CIS Faculty Ivy Tech State College Northwest Region 01

2. Introduction - Management of Network Functions • Organizations are expanding networks with more computing devices • Two problems: • demand placed on data communication by many hardware interconnections • pressure for networks to operate with greater reliability and faster speed See Illustration p.225

3. History - Management of Network Functions • Early systems focused on sharing hardware resources • Physical network, coupled with a NOS, allowed increased availability of resources & spread cost among users • Data and information sharing increased • NOS were enhanced for centralized information resources

4. History - Management of Network Functions • Applications collectively known as groupware, use a set of technologies called distributed processing • Provide even greater access to centralized information • Assist users who need to work together to complete tasks

5. Comparison of Network &Distributed Systems • Network Operating System (NOS) developed from a need to provide • global resource allocation • global process management • complete transparency of network access for users and their sites’ OS (known as local OS) • To a local OS, the NOS is the actual server performing the task, when in reality it is the instrument for the actual task

6. Comparison of Network andDistributed OS • NOS does not consider memory, process, device, or file management from a global viewpoint • NOS sees them as local functions that must interact with each other but do not direct each other • Global control of all assets is a need that led to the development of a Distributed Operating System (DOS - not to be confused with MS-DOS)

7. Comparison of Network and Distributed OS • Major difference between NOS and DOS is in how each views and manages local and global resources • NOS build on capabilities provided by the local OS and extend it to satisfy new needs • DOS views systems resources as globally owned and manages them as such See Fig. 10.1 & 10.2 p. 226-227, Table 10.1 p.228

8. Distributed Operating System (DOS) Development • DOS manages the entire group of resources within a network in a global fashion • Viewed as a logical single system rather than a collection of independent cooperating systems • Control & allocation of resources are negotiated & compromised among peers sites in the DOS • Advantage is its ability to support file copying, email, & remote printing with installation of special driver software

9. DOS Development • Memory Management • memory allocation and deallocation will depend on the selected global scheduling and sharing schemes • similar to local OS, but it must be extended to accept requests for memory from both local & global resources • uses virtual memory, when an application tries to access a page not in memory, a page fault error will occur & the memory manager will automatically bring that page into memory

10. DOS Development • Process Management • provides policies & mechanisms to manipulate processes to provide real-time priority execution and the state of execution • each CPU in the network is required to have its own kernel that manages low-level operation on a physical device • two ways of looking at the DOS: • process-based: large collection that includes all the system processes & resources • object-based: clumps types of hardware with its necessary operational software into units

11. DOS Development • Process-based DOS • provides for process management through client/server processes synchronized & linked together through messages & ports (also known as channels or pipes) • high level of cooperation & sharing of actions and data maintained by the system sites • synchronization is key by using primitives such as “send and receive” • interrupts, which cause a processor to be assigned to another process, are represented as messages that are sent to the proper process for service

12. DOS Development • Object-based DOS • instead of being made up of resources & processes, the system is viewed as a collection of objects (all pc components) • process management becomes object management • capability lists for objects • synchronization & communication support are part of the kernel portion of a DOS • uses different communications primitives which are either synchronous or asynchronous

13. DOS Development • Object-based and process-based difference • objects contain all of their state information • information is not stored separately in another part of the system • information does not need to be stored in a process control block or other data structure separate from the object

14. DOS Development • Device Management • devices must be opened, closed, read from, and written to • status bit must be set or cleared & parameters must be initialized • can be done on a global, cluster, or localized basis • allocation is successfully completed after examination of the device’s status See Fig. 10.4 p. 235

15. DOS Development • Device Management • process-based DOS • all resources are controlled by servers that accept requests for service by others • object-based DOS • physical device viewed as an object manipulated by a set of operations to designate device functions See Fig. 10.5 p.236

16. DOS Development • File Management • goal of distributed file management is to give users the illusion of a single local file system • main function of a DOS file manager is to provide transparent mechanisms to find, open, read, write, close, create, & delete files in the network • similar environment to distributed database • controls to provide efficiency, consistency, and reliability • Detection & correction, prevention, & avoidance are used to deal with deadlock

17. DOS Development • Communication Management • unique to networked systems, stand-alone has no need for communication manager • provides policies & mechanisms to achieve intrasite & intersite communication among concurring processes • process is registered or logged in the network • ports are usually associated with physical buffers & I/O channels, & represent assets that must be used wisely

18. DOS Development • Communication Management • process-based DOS • interprocess communication is transparent to the user • network manager has functions of controlling allocation of ports to processes, etc. • object-based DOS • makes both intermode & intramode communications among cooperative objects easy • knowing the location of the receiver is not necessary, network managers: send, receive, reply, request

19. NOS Development • True operating system • memory, processing, file, & device management • NOS typically run on servers and perform services for network nodes or workstations called clients • NOS focuses on user interaction • NOS examples are: Novell Netware, Microsoft LAN manager, IBM’s LAN Server, Windows NT

20. NOS Development • Important Features in a NOS • 16-bit or 32-bit software to take advantage of modern processors • LAN standards: Ethernet, token ring, Localtalk, and Arcnet • heterogeneous: they support workstations with different OS • use a variety of third-party hardware devices and software applications • must be efficient and secure with core components to enable multiple clients quick access & resources, & security

21. NOS Development • Major Functions of NOS • allow users to access resources at a remote site; Internet Telnet • security, access to resources with user id & password • procedure to transfer files from one computer to another; Internet FTP (file transfer protocol)

22. Summary • Network operating systems (NOS) were developed to link free standing independent systems • Distributed Operating Systems (DOS) were developed to take full advantage of global resources available to all connected sites

23. Summary • NOS & DOS requirements: • security from unauthorized users yet accessible to authorized users • communication links • monitoring system resources: • memory • processor • devices • files