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COMP2322 Networks in Organisations

COMP2322 Networks in Organisations. Richard Henson March 2016. Week 6: Windows Networks: Availability, Inegrity & Security. Objectives: Explain why user and system settings need to be controlled on networked machines

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COMP2322 Networks in Organisations

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  1. COMP2322Networks in Organisations Richard Henson March2016

  2. Week 6: Windows Networks: Availability, Inegrity & Security • Objectives: • Explain why user and system settings need to be controlled on networked machines • Explain the role of the registry in Windows desktop and network configuration, user settings, and security • Select appropriate software tools for backup and fault tolerance

  3. Platforms for Operating Systems • Continuing from last week… • With Windows 2000 Server… • Intel platform survived threats from RISC architecture… • 64-bit alpha platform never that popular • rights to DEC’s alpha chip finally bought by Intel!

  4. Platforms at Client-end and Server-end • Soon afterwards…Windows became 64-bit on an Intel platform: • on server motherboards • running Windows 2003 onwards • on workstations (Vista) • Due to Microsoft’s disastrous (mis)launch of Vista… • Apple client platform had a chance to emerge and develop a good range of apps • ensured success of i-player & i-phone

  5. Windows 2003 Server • Main difference at kernel level: • 64-bit option • 32-bit kernel unchanged… • Noteworthy extra functional enhancements: • GDI+ interface • Enhanced active directory • Group Policy management console

  6. BIOS Developments • Earlier motherboards had a single chip containing the BIOS on ROM and a writeable CMOS area • the command line interface invoked was 16-bit • More recent motherboards use EFI (Extensible Firmware Interface) • uses a 32-bit command line • only really exploited with Windows 7, and 2008 Server…

  7. More about booting to an Intel platform • BIOS should “point” to selected medium that contains a “boot loader” program • contains “master boot record” (MBR) • points to the boot partition • containing the operating system • Different media prepared in different ways • hard disk still the conventional boot medium • number of partitions so potential choice of bootable media • CDs & USBs only have one partition

  8. Partitions, Hard Disks and Multiple Operating Systems • MBR must be on the first (C:) partition • possible to have different operating systems on the same hard disk… • varieties of Windows • varieties of Unix… • BUT… • MBR systems different on Unix and Windows • still possible to have ONE Unix partition…

  9. Logon • Once the operating system has been loaded… • user logon screen presented • Rapid local boot is fine… • but most organisational computers are on networks… • why? • why does network logon take so long?

  10. Rapid Boot-up with Windows 7 (1) • Huge improvements in time to logon screen… • 32-bit colour animation appears at an early stage • driven by the CPU (& using EFI) • graphics card not yet initiated… • meanwhile, operating system's kernel and critical device drivers are loading into memory in the background…

  11. Rapid Boot-up with Windows 7 (2) • Early stage of boot process is i/o bound: • loading the kernel • device driver files • other system component files • Dimensions of the boot animation limited to a small region of the screen • avoid i/o delay loading animation images during the early stage of boot…

  12. Rapid Boot-up with Windows 7 (3) • Changes to the boot “architecture” • Windows 7 animation happens as the process moves along • contrast with Vista, where the pear animation comes only after the boot sequence is complete… • fewer transitions in graphics mode during initialisation of the graphics subsystem and Windows shell • again, c.f. Vista, where screen flashes black a few times.. • Sound plays BEFORE user login starts…

  13. BUT… • The user in an organisation then needs to log on… • endless loading of policy files… • subsequent configuration to accommodate settings into the local registry…

  14. Backing up Active Directory • Goes without saying that the loss of Active Directory will be bad for the network • people won’t even be able to log on! • Should be backed up… regularly! • Best way to do this is on another computer…

  15. Fault Tolerance • General engineering principle… • if it can go wrong… it will! • To maintain availability for users, the whole domain controller should be backed up! • active directory designed as a distributed database that backs up to a reserve domain controller • Backup domain controller software set up using same active directory wizard

  16. Fault Tolerance (hardware fault) • E.g. Hard disks • can crash or become corrupt • System needed for a backup to take over “seamlessly” • i.e. without the user noticing… • Achieved by disk mirroring/duplexing • exact copy available to take over at a moment’s notice

  17. Domain Trust • This allows users on one domain to log onto resources on another domain • Trusts can be one or two-way Domain A Domain B

  18. Enterprise Structure of Active Directory • A hierarchical system of organisational data objects • i.e. domains, • A Tree can be • a single domain • group of domains

  19. Domain Trees & Forests • Active Directory provides “trust” between the databases of domains that are linked in this way • A “Tree” is the domains and links between them • A “Forest” contains data needed to connect all objects in the tree: • domain objects in the tree are logically linked together in the forest and their users can “trust” each other

  20. Active Directory and Users • Active directory allows set up and management of domain users • Can also define domain groups, and allow domain users to become part of domain groups • aids administration • policy file can be set up • interacts with user machines registry during login • controls user desktop

  21. Organisations, Organisational Units, and Domains • An organisation may: • have several locations • have several functions in same location • Alternative to multiple domains… • organisational units • group policy can be applied selectively

  22. WINS (Windows Internet Names Service) • Used on earlier Windows TCP/IP networks to enable computer devices to communicate using IP • manages a dynamic database of IP addresses and local network (NetBIOS) names • clients request IP addresses for particular NetBIOS names • WINS server provides that information

  23. Active Directory and DNS • In Active directory, each domain in the tree has a unique DNS identity • therefore a unique IP address… • can cause confusion when setting up domain structure!! • Also, each device within a domain can also made use of DNS, via its IP address… • no need for WINS…

  24. Microsoft TCP/IP stack • Differs from UNIX TCP/IP (e.g. no FTP, SMTP or Telnet) • DNS is available as a network service • Application layer components: • Windows sockets - to interface with sockets-based applications • NetBT - to interface with NetBIOS applications • SNMP, TCP, UDP, IP as with Unix protocol stack

  25. Configuring TCP/IP on Windows • Requires local administrator access!! • Locate and double-click TCP/IP • If DHCP (dynamic host configuration protocol) is running, IP addressing is dealt with automatically by the DHCP server

  26. TCP/IP Configuration (2) • Otherwise, three IP addresses can be manually added: • Local static machine IP address • Subnet mask • Default gateway

  27. TCP/IP Configuration (3) • Local machine IP address • DHCP protocol can automatically assign IP addresses from a Windows 2000 server machine running DHCP server • Alternatively, a static IP address can be keyed in manually • Subnet mask: • normally 255.255.255.0 for small networks • 255.255.x.0 for larger networks • x -> 0 as the network gets larger • Default gateway is the IP address of the LAN-Internet interface computer…

  28. Windows TCP/IP utilities • Located in the system32 directory • Not available from the GUI • Only accessible via the NT prompt (Ping (packet internet groper): • FTP • Telnet • Finger (retrieval of system information from a computer running TCP/IP & finger • ARP (displays local IP addresses according to equivalent MAC or “physical” addresses) • ipconfig (displays local IP configuration) • tracert (checks route to a remote IP address)

  29. Terminal Services • Allows any PC running a version of Windows to remotely run an NT series server • uses a copy of the server’s desktop on the client machine • Client tools must be installed first, but the link can run with very little bandwidth • possible to remotely manage a server thousands of miles away using a phone connection…

  30. Remote Access Service • RAS also allows access to an NT network through routes such as: • PSTN • X25 • ISDN • Uses Point to Point protocol (PPP) • remember that? • Also supports use of PPP Multilink protocol, which allows a combination of communications links and multiple links to be used

  31. Remote Access Service • Also provides capability for VPNs (Virtual Private Networks) using secure Internet access • using PPTP (point-point tunnelling protocol) • Standard username/password authentication still required for all remote logins • Can be used as a Gateway for NetBIOS names or (using IPX) to remotely gain access to Novell Netware services

  32. RAS & Secure Remote Login • To login remotely, user must have a valid username/password and RAS dial-in permission • RAS can use “call back” security: • Server receives a remote request for access • Server makes a note of the telephone number • Server calls the remote client back, guaranteeing that the connection is made from a trusted site • Login information is encrypted by default • All remote connections can be audited

  33. Internet Information Server (IIS) • Microsoft’s Web Server • can also provide ftp or smtp publishing service • Purpose: • make html pages available: • as a local www service • across the network as an Intranet • across trusted external users/domains as an Extranet • run server-scripts in communication with client browsers

  34. Internet Information Server (2) • Sets up its own directory structure for developing Intranets, Extranets, etc. • Access to any IIS service can be restricted using username/password security

  35. Internet Information Server (3) • Can allow anonymous remote login: • Uses a “guest” account – access only to files that make up the Intranet • Anonymous login prevents trying to hack in through guessing passwords of existing users • Provides the software connectivity for a server-side interface that can connect client-server Internet applications

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