1. Network Operating Systems Examples
Instructor: Dr. Najla Al-Nabhan
2015

2. Peer-to-Peer: Client/server Windows for workgroups/95 (Cont.)
Outline..
Peer-to-Peer:
Windows for workgroups/95 (Cont.)
Client/server
Windows NT

3. Review.. Peer-to-Peer LANs
In many offices and small businesses, there is a need for a simple peer-to-peer network. If security is not a concern and where 10 or fewer computers are located within a relatively small area, a peer-to-peer network might be the most economical option. In these networks, all workstations are equal and each can act as either a server or a client. In most cases, these networks will be sharing only files and printers. Most of the popular operating systems include the necessary software to configure a peer-to-peer network.

4. Windows for Workgroups
Introduced between
Windows for Workgroups (Windows 3.11) functions much like its predecessor, but includes:
a peer-to-peer NOS,
an application,
and an appointment-book application.
It allows a group of computers connected through workgroups can share printers and disk files.

5. Windows for Workgroups: screenshots

6. Sharing files and printers using Windows for Workgroups
Only items designated as shares can be seen by other members.
All other files and printers are hidden from all users except the local computer.
When you share a disk directory or printer from a workstation, you give the shared resource a name to which others can refer.
For Details & Steps: (Enabling File Sharing and Printer Sharing)

7. Sharing files and printers using Windows for Workgroups

8. Sharing files and printers using Windows for Workgroups
During the connection process, a drive letter is assigned to the shared directory and the redirector redirects the Line Printer Terminal (LPT port ) across the LAN to the correct printer.
Windows for workgroups supports SMB sharing.
LPT is used by IBM compatible computers as an identification for the parallel port such as LPT1, LPT2, or LPT3. This is commonly required when installing a printer on an IBM compatible computer. The majority of all computers utilize LPT1 and do not have an option for another LPT port unless additional ports are added to the computer

9. Server Message Block (SMB)
SMB operates as an application-layer network protocol mainly used for providing shared access to:
files, 
printers, 
serial ports, and
various communications between nodes on a network.
It also provides an authenticated inter-process communication mechanism.
Most usage of SMB involves computers running Microsoft Windows, Therefore, it was known as "Microsoft Windows Network" before the subsequent introduction of Active Directory.

10. Server Message Block (SMB) Features
SMB can run on top of the Session (and lower) network layers in several ways:
Directly over TCP, port 445;
Over the NetBIOS API, which in turn can run on several transport layer protocol :On UDP ports 137, 138 & TCP ports 137, 139 (NetBIOS over TCP/IP);
Over IPX/SPX protocol (Internetwork Packet Exchange/Sequenced Packet Exchange)
IPX/SPX stands for Internetwork Packet Exchange/Sequenced Packet Exchange. IPX and SPX are networking protocols used primarily on networks using the Novell NetWare operating systems.

11. Windows 95 and 98
Windows 95 and 98 operating systems include software necessary to create a peer-to-peer network and enable sharing of printers and files.
Computers running Windows 95 or 98 will also work well as clients on Windows NT and NetWare LANs. You will have to install the respective client (requester) software.
Note that users of Windows 95 and 98 cannot have the full benefit of Windows NT security features; those features require use of the NTFS file format, which is not compatible with Windows 95 or 98.

12. Windows NT Server Windows NT is a server operating system
Windows NT Server was first introduced in the mid-90s and is capable of managing workgroups just like Windows for Workgroups/95.
Windows NT Server has all of the advantages mentioned for the other Windows operating systems, plus, it contains several other features making it more robust.

13. Windows NT Server Features:
It is a client/server NOS that uses routable protocols, making it a true Internetworking Operating System enabling network administrators to connect LANs to WANs.
Windows NT Server also provides services for OS/2 and Novell NetWare clients
It is able to run on various microprocessors such as Intel Pentium, DEC Alpha, RISC, MIPS, and PowerPC based systems.

14. Windows NT Server Features:
The security on Windows NT allows a network administrator to not only provide passwords for resources but also to individuals or groups.
This operating system does require the use of a more powerful server computer whose sole function is to act as administrator of the NOS program.
Having a server where all access data is stored makes managing Windows NT Server Operating Systems efficient.

15. Security in Windows NT Server
Windows NT Server has more than one level of security beyond access/no access.
It offers the following security levels:
no access.
access that restricts the user to read only capabilities.
access that allows read and write usage.
access that allows you to change access permissions for network users.
Each user who wishes to access services on the network must have a password and a user account set up within the domain.

16. Next lecture
Complete NOS Examples.
Quiz 2

17. Security in Windows NT Server: Security Domains
A domain is a security model where the database of user accounts is stored on one or more computers known as domain controllers.
Important for the centralize control of the network.
The network administrator creates, deletes, and manages these accounts and passwords using the User Manager for Domains program that comes with Windows NT Server.

18. Security in Windows NT Server
For security reasons, companies often have two servers capable of authenticating passwords:
one that acts as the Primary Domain Controller (PDC) and
the other as the Backup Domain Controller (BDC).

19. Security in Windows NT Server
Primary Domain Controller (PDC):
The PDC is a computer on the network that maintains a database of users and security policies for the domain.
This database contains the names of users and the resources they may access.
User access may be defined for individual files or for entire directories.
Note that although the PDC is often a server computer, this is not necessary. Network services can be implemented on one computer and the PDC functions on another

20. Security in Windows NT Server
BDC (Backup Domain model) :
A BDC maintains a copy of the PDC database. This backup database prevents network disruption in the event of failure of the PDC.
If a failure occurs, the backup domain controller can be easily switched to the PDC.
With Windows NT Server networks can connect to other domains.

21. Security in Windows NT Server
There are four basic domain models:
Single Domain Model
Master Domain Model
Multiple Master Domain Model
Multiple Trust Domain Model

22. Windows NT Domain Models
Single Domain Model— In the single domain model, there is only one defined set of security and user accounts.
This means that all management functions are centralized.

23. Windows NT Domain Models
Master Domain Model— In this model, there is one master domain server that has the defined set of security and user account data of all other domain servers. However, each of these has only the specific security data for one domain.
A user on one domain cannot get permissions not found on her/his domain server.
This improves on the single domain model since it allows segmentation of networks, which increases security measures, yet still allows centralized management of network user accounts and accessibility.

24. Windows NT Domain Models
Multiple Master Domain Model—The Multiple Master Domain Model has several master domain servers, each with their own specific domains.
In this model, network management becomes somewhat decentralized and network administrators cannot maintain the entire network from one central domain server.

25. Windows NT Domain Models
Multiple Trust Domain Model— This model is really a peer-to-peer relationship among domain servers,
therefore it becomes decentralized and security is essentially the same as with Windows for Workgroups and Windows 95.