DCNSA Level II
Network Operating Systems cheat sheet
Every chapter's key points, formulas and definitions on one page, for the last week before the exam. Each heading links to the chapter that explains it.
Network operating systems
- A network operating system manages and coordinates resources across a network, extending the single-machine work of managing processes, memory and files to many connected computers at once.
- A server provides resources or services to other computers, a terminal is the device or interface used to reach it, and a directory is the central store of information about resources, users and devices.
- Server roles give a server a specific function such as file sharing, authentication or name resolution; one server can run several roles, or a large organisation can dedicate a server to each.
- The networking features a NOS provides are multiprocessing, resource sharing, backup and web services, internetworking, network security and directory services.
- Client-server centralises administration and security and scales to thousands of users; peer-to-peer needs no dedicated server but is practical only for a handful of machines.
Key terms
- Server
- A computer that provides resources or services (files, authentication, DNS, web content) to other computers on a network, typically running a network operating system and dedicated hardware built for continuous operation.
- Terminal
- A device or interface used to access and interact with a server or network system, historically a simple screen-and-keyboard device with no processing of its own, now more often a full client computer or a remote-desktop session acting the same role.
- Directory
- A structured store of information about network resources, users and devices, such as Active Directory: names, passwords, group memberships, computer accounts and the policies attached to them, held centrally rather than scattered across every machine.
- Multiprocessing
- Using more than one processor (or core) to handle multiple tasks in parallel, important for a server handling many simultaneous requests from client machines rather than one user's own work.
- Resource sharing
- Making files, printers and storage centrally accessible to network users, the most immediately visible benefit of a NOS to an ordinary user.
- Backup and web services
- Built-in support for scheduled backups of server and client data, and for hosting web-accessible resources such as an intranet site or a portal.
- Internetworking
- Connecting and coordinating across multiple interconnected networks, so a NOS's services can be reached from, and can reach, more than one local network.
- Network security
- Authentication, authorisation and access control enforced centrally by the NOS rather than configured separately, and inconsistently, on every individual machine.
- Directory services
- A centralised store of user, computer and resource information, the backbone of centralised administration: a password changed once in the directory takes effect everywhere that account is used.
- Client-server systems
- Dedicated servers provide services (files, authentication, printing) to many client machines. Centralised, scalable, and the dominant model for organisations of any real size, because administration, security policy and backup are all applied in one place rather than machine by machine.
- Peer-to-peer network operating system
- Every computer can act as both client and server, sharing its own resources directly with others, with no dedicated central server. Simpler and cheaper to set up, needing no server hardware or licence, but harder to secure (each machine manages its own accounts and shares) and harder to scale, since there is no single place to apply a policy change across every machine.
The rest of the sheet covers
- Installing a network operating system
- Configuring a network operating system
- Exam technique and revision
- Glossary