局域网：软件及支持系统

1 .Chapter 8 Local Area Networks: Software and Support Systems

2 .Network Operating Systems An operating system manages all applications and resources in a computer A multitasking operating system supports the execution of multiple processes at one time A network operating system is a large, complex program that manages the resources common on most local area networks Besides performing standard operating system functions, also called upon for additional functions (refer to next slide)

3 .3

4 .Current NOS Several popular network OSs currently exist: Windows Server family Unix Linux NetWare derivatives Even though NetWare installations are now much fewer than any of the first three, NetWare is introduced first since it was the first to introduce the modern directory structure

5 .Novell NetWare Version 3 - Popular but older version no longer supported by Novell (end of 2000) user logs onto a particular server bindery maintains directory system. Version 4 unlike version 3 this version allows single network login bindery replaced by powerful NDS database no longer supported by Novell (beginning of 2004) Version 5 allows administrator to use IP protocol instead of Novell’s proprietary IPX/SPX protocols

6 .Novell NetWare Version 6 A client anywhere on the Internet can print and use storage services from a NetWare 6 server without loading a single byte of Novell’s Client32 software Powerful Internet printing services ( iPrint ) make printing nearly idiot-proof User clicks on graphical image of floor plan showing printers If user does not have printer driver, it is loaded automatically in background iFolder : Very effective background application powered by Apache Web Server to “synchronize” the documents in each system’s My Documents folder with an identical set on the server Volumes can hold 8 terabytes of data in up to 8 trillion files and can keep 1 million files open concurrently

7 .Novell NDS (NetWare Directory Services) Novell NDS: Database that maintains information on, and access to, every resource on the network, including users, groups of users, printers, data sets and servers Network administrator creates a hierarchical tree structure that represents the layout of the organization Tree structure is composed of: Organizational units Ú composed of further objects Leaf objects Ú not composed of further objects

8 .8

9 .Designing a Network Tree Hierarchical directory design Whether the NOS is NetWare or Windows 2003, there are basic elements to designing a solid tree structure Some designers like to base the root of the tree on the company’s wide area network layout For example, the next slide breaks the root over three wide area locations Once the wide area has been designed, you can break each city into the various departments Some designers like to break departments by their logical location, while others break departments by their physical location

10 .10

11 .Windows NT Version 4 (I) User interface based on popular Windows operating system, but is NOT the same as Windows 98 or Windows Me Full service multi-tasking operating system capable of supporting multiple servers NT systems work very well with other Microsoft products Questionable if NT can support large systems Blue screen of death (BSOD) plagues NT systems

12 .Windows NT Version 4 (II) Domain Group of users, servers, and other resources that share account and security information May have from 1 to several hundred domains depending on size of system Every domain has one and only one primary domain controller (PDC) (a server) Centrally manages account information and security Each domain should have at least one backup domain controller (BDC) (a server)

13 .Windows NT Version 4 (III) Single domain model Simplest Windows NT domain model One domain that services every user and resource Multiple domain model Multiple domains, but no hierarchy Each domain is equal to all other domains To allow data to transfer between domains required the creation of trusts Master domain model Uses single domain to exert control over user account information Separate resource domains manage resources such as networked printers Multiple master domain model Uses two or more master domains that are joined in two-way trusts to manage many resource domains

14 .14

15 .15

16 .Windows 2000 (I) Updated version of Windows NT network operating system Specific versions of 2000 designed to support wide variety of system types: Windows 2000 Professional - replaces NT Workstation Windows 2000 Server - replaces Windows NT Server Windows 2000 Advanced Server – supports up to 8 procs / 8GB RAM Windows 2000 Datacenter Server - supports up to 32 processors and 64GB RAM

17 .Windows 2000 (II) Biggest change from NT: Active Directory AD is central repository for all objects that make up the enterprise: Domains, organizational units, users, groups, computers, printers, etc. Roughly based on X.500 spec, creates a hierarchical tree At top of hierarchical model Ú single forest of one or more trees Must contain: At least one (root) domain, which must contain at least one organizational unit (OU) Several other containers (see next slide) Recommended size limitation of 1 million objects per domain However, lab tests have hit 10 million objects without failure

18 .18

19 .Windows 2000 (III) The domain has basically remained the same, but now you can have parent and child domains Parent and all child domains are defined as single domain tree, with multiple trees in the same AD and forest Domains are named in accordance with the Internet’s DNS standard RFCs 1034 and 1035 Example, the root domain in a tree could be called bigcompany.com The marketing child domain could be mktg.bigcompany.com The production child domain could be prod.bigcompany.com As in NT, you can create Trusts between parent and child domains Only with 2000 the trust can be transitive Many still agree that Windows 2000 has a way to go to catch up to NetWare with regards to simplicity of administration Nonetheless, NetWare has dropped below 20% of the market while Windows continues to climb (>50%)

20 .Windows 2003 Improvements to Active Directory, including new management tools Capability to interconnect up to 8 Windows servers New and improved file and print support services Support for IPv6 Security improvements

21 .Windows 2008 The newest version of Windows network OS Continued improvements to Active Directory, including new management tools New server core (including a virtual server) Self-healing server that can fix corrupted files and/or folders Increased processing speed Advancements in network security

22 .Unix Older but very popular multitasking operating system capable of supporting network operations First operating system written in the language C Very stable system capable of supporting very large operations Numerous versions available from different vendors

23 .Linux Operating system based on the principles of Unix Many versions available for free or very small price Very stable multitasking operating system When incorporated with other free software products, such as the Apache Web Server and Atipa’s BlueBird network management software, this system becomes extremely cost effective and powerful

24 .Novell Linux Novell, seeing that its market share of NetWare was eroding, moved into the Linux market in the early 21st century Novell currently offers a number of versions of Linux, including high-power servers and desktop OSs

25 .Mac OS X Server Apple Computer finally joined the NOS market with its Mac OS Server Version X is based on Linux code Very stable and quite powerful While installed primarily in Apple networks, Mac OS X Server is also capable of supporting non-Apple networks

26 .26

27 .Network Servers (I) In order to support a network OS, you need one or more network servers Network servers are high-power workstations often with multiple processors, RAID, SCSI, and lots of memory and disk space New forms of servers include server appliances, and server blades

28 .Network Servers (II) To protect the server from catastrophic disk failure, disk drives on most network servers support one of the redundant array of independent disks (RAID) techniques RAID is a collection of techniques for interfacing multiple hard disk drives to a computer RAID-0 Data is broken into pieces, and each piece is stored on different disk drives This technique is known as striping. RAID-1 Data is stored on at least two disk drives, in duplicate, to provide a level of redundancy (or fault tolerance), should one disk become corrupted This technique is known also as disk mirroring RAID-3 Data is redundantly stored across multiple disk drives (striping), and error-checking information concerning the stored data is kept on a separate disk RAID-5 Data is broken into pieces (stripes) and stored across three or more disks Parity information (error-checking code) is stored along with the striped data, not on a separate disk RAID-5 is the most popular of the RAID techniques

29 .Client/Server vs. Peer-to-Peer A clear majority of local area networks are client/server networks: Client/server network has one or more network servers supporting the operations of one or more clients, or user workstations Peer-to-peer networks also exist: May have servers, but the network relies less on servers and more on communications between workstations