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). 2

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. 3

4 Network Operating Systems and Servers Determining optimal server hardware –Questions to ask 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?

5 Network Operating Systems and Servers Determining optimal server hardware (cont’d.) –Applications influence: 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

6 Client Support Very important NOS function –Allows efficient communication, resource sharing NOS client support tasks include: –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

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) 7

8 Client/Server Communication A client connecting to an NOS

9 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

10 Users and Groups After NOS client authentication –Client gains access to NOS services, resources –Start with none Administrator account –Most privileged user account –Unlimited rights to server, domain resources, objects –Created by default –Administrator - Windows –Root on UNIX or Linux systems –Admin - Netware

11 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

12 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

13 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

Sharing Applications Installing application on server –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 14

15 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

16 Sharing Printers Shared printers on a network

17 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

18 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

19 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

20 Multitasking Execution of multiple tasks at one time –All operating system perform this Does not mean performing more than one operation simultaneously Preemptive multitasking –Happens quickly –Appearance of tasks occurring simultaneously –Time sharing: UNIX –Windows also does it –Run, stop, put process state in memory, next task

21 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

22 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

23 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

24 File System File system –Method of organizing, managing, and accessing files Through logical structures, software routines 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

25 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

Misc Pacemaker hack can deliver deadly 830-volt jolt –Pacemakers and implantable cardioverter- defibrillators 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. 26

End of Network Operating Systems Questions