Transcript Network Operating System

Chapter 10 Management of
Network Functions
CIS106
Microcomputer Operating Systems
Gina Rue
CIS Faculty
Ivy Tech State College Northwest Region 01
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
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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
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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
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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
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task
Comparison of Network and
Distributed 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) 6
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
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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
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installation of special driver software
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 9memory
DOS Development
– Process Management
• provides policies & mechanisms to
manipulate processes to provide realtime priority execution and the state of
execution
• each CPU in the network is required to
have its own kernel that manages lowlevel 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
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with its necessary operational
software
into units
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
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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
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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
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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
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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
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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 16
to deal with deadlock
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
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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,
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reply, request
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
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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
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access & resources, & security
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)
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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
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Summary
• NOS & DOS requirements:
– security from unauthorized users yet
accessible to authorized users
– communication links
– monitoring system resources:
• memory
• processor
• devices
• files
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