Transcript Network Operating Systems

CEG 2400 FALL 2012
Network Operating Systems
Characteristics of Network Operating
Systems (NOS)
• Client/Server type architecture
• NOS do the following:
– Server enables multiple clients to share resources
managed by the NOS
– Centrally manage network resources, such as
programs, data, and devices (for example, printers).
– Secure access to a network.
– Allow remote users to connect to a network.
– Allow users to connect to other networks (for
example, the Internet).
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Characteristics of Network Operating
Systems
• NOS do the following:(con’t)
– Back up data and make sure it's always available
– Allow for simple additions of clients and resources
– Monitor the status and functionality of network
elements.
– Distribute programs and software updates to clients.
– Ensure efficient use of a server's capabilities.
– Provide fault tolerance in case of a hardware or
software problem.
• Not all of these functions are built in to every NOS
installation; some are optional.
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Network Operating Systems and Servers
• Determining optimal server hardware
– Questions to ask
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What kinds of applications will run on the server?
How many clients will connect to the server?
How much storage space will each user need?
How much downtime, if any, is acceptable?
What can the organization afford?
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Network Operating Systems and Servers
• Determining optimal server hardware (cont’d.)
– Applications influence:
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Type of application
Resources used
Processing burden
Vendor reputation - High quality, dependability,
excellent technical support
– Server Reliability
• Spend as much as necessary
• Component failure: widespread effects, costs
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Client Support
• Very important NOS function
– Allows efficient communication, resource sharing
• NOS client support tasks include:
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Creating and managing client accounts
Enabling clients to connect to the network
Allowing clients to share resources
Managing clients’ access to shared resources
Facilitating communication between clients
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Client/Server
Communication Process
• Logon process – Both client and server software
• Redirector - Client
– Intercepts requests, determines where to send
– The server’s OS, clients’ OSs, and redirectors must be
compatible for a multivendor environment to succeed
• File Access Protocol - Server
– Windows client communication with Windows Server 2008
• CIFS (Common Internet File System)
• Older protocol SMB (Server Message Block)
– Broad support allows every client type to authenticate, access
resources (Mac, Linux, etc)
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Client/Server Communication
A client connecting to an NOS
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Client/Server Communication
• Middleware Software
– Translates requests, responses between different
types of clients and the server
• A 3-tier architecture
– Client/server environment incorporating middleware
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Users and Groups
• After NOS client authentication
– Client gains access to NOS services, resources
– Start with none
• Administrator account
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Most privileged user account
Unlimited rights to server, domain resources, objects
Created by default
Administrator - Windows
Root on UNIX or Linux systems
Admin - Netware
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Users and Groups
Access Rights
• User names
– NOS grants each network user access to files and
other shared resources
• Groups
– Basis for resource and account management
– Greatly assists in resource sharing and security
control
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Groups
• Nesting or hierarchical group arrangement
– Simplifies management
– Group arrangement
• Affects permissions granted to each group’s members
• Inherited permissions
– Passed down from parent group to child group
• After user, group restrictions applied
– Client allowed to share network resources
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Sharing Applications
• Shared applications
– Specifically designed to run applications on file server
• Application licensing types
– Per user licensing – number of active users
– Per seat licensing – number of potential users
– Site license – unlimited users
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Sharing Applications
• Installing application on server
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Purchase appropriate type and number of licenses
Verify server resources
Install application
Make application available to users
• NOS responsible for arbitrating file access
• Problem with shared file access
– Multiple users simultaneously accessing same data
files, same program files
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Sharing Printers
• Increases resource management efficiency; reduces
costs
• Print server
– Manages print services
• All NOSs perform common tasks in managing
printers
• Client redirector
– Determines where print request should transmitted
• Network, workstation
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Sharing Printers
Shared printers on a network
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Memory
• Physical memory: RAM chips
• Virtual memory: stored on hard drive
– Page file (paging file, swap file)
• Managed by operating system
– Paging
• Moving blocks (pages) from RAM into virtual memory
• Virtual memory can boost total memory available
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Memory
• Virtual memory advantages
– Easily expands memory available to server
applications
– Engaged by default
• Virtual memory disadvantage
– Slows operations
• Hard drive access much slower versus physical
memory access
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Memory Model
• Addressing schemes
– 32-bit addressing scheme (4 G limit)
– 64-bit addressing scheme (18 exabytes – big number)
• NOS assigns each application (process)
– Own 32-bit memory area
• Logical subdivision of memory available to server
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Multitasking
• Execution of multiple tasks at one time
– All operating system perform this
• Does not mean performing more than one operation
simultaneously
• Preemptive multitasking
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Happens quickly
Appearance of tasks occurring simultaneously
Time sharing: UNIX
Windows also does it
Run, stop, put process state in memory, next task
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Multiprocessing
• Process
– Routine of sequential instructions that runs until goal
is achieved
• Thread
– Self-contained; well-defined task within process
– Main thread
• All processes have one
• One processor systems
– One thread handled at any time
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Multiprocessing NOS
• Support use of multiple processors to handle
multiple threads
• Technique to improve response time
• Splits tasks among more than one processor
– Expedites single instruction completion
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Multiprocessing
• 1. Symmetric multiprocessing*
– Splits all operations equally among two or more
processors
• 2. Asymmetric multiprocessing
– Assigns each subtask (thread) to specific processor
• Multiprocessing is an advantage to servers with high
processor usage
– Speed
– Run numerous tasks simultaneously
• Almost all NOSes do multiprocessing
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File System
• File system
– Method of organizing, managing, and accessing files
• Through logical structures, software routines
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Windows - NTFS (New Technology File System)
Netware – NSS
Solaris - UFS (UNIX file system)
Linux native file system type
– ext4: “fourth extended” file system (NFS, Samba)
• Disk data distribution
– Difference is how they set up the file structure
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Summary
• Characteristics common to all NOS
– Systems and servers, client support, identifying and
organizing network elements, sharing applications
and printers, memory, processing modes, managing
system resources
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Misc
• Pacemaker hack can deliver deadly 830-volt jolt
– Pacemakers and implantable cardioverterdefibrillators could be manipulated for an anonymous
assassination
– Pacemakers from several manufacturers can be
commanded to deliver a deadly, 830-volt shock from
someone on a laptop up to 50 feet away, the result of
poor software programming by medical device
companies.
– The trend is now to go wireless. Several medical
manufacturers are now selling bedside transmitters
that replace the wand and have a wireless range of
up to 30 to 50 feet.
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End of Network Operating Systems
Questions