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COMP3122 Network Management

COMP3122 Network Management. Richard Henson April 2012. Week 9 – Connectivity and IP addressing Issues. Learning Objectives: Explain the meaning of class A, B, C, IPv4 addresses Apply principles of IPv4 addressing and subnet masks to the matter of optimising packet size in a LAN

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COMP3122 Network Management

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  1. COMP3122 Network Management Richard Henson April 2012

  2. Week 9 – Connectivity and IP addressing Issues • Learning Objectives: • Explain the meaning of class A, B, C, IPv4 addresses • Apply principles of IPv4 addressing and subnet masks to the matter of optimising packet size in a LAN • Explain the advantages of terminal emulation and other ways of doing the processing elsewhere…

  3. What is connectivity? • The sum total of how well hardware & software integrate to provide smooth passage of data between programs on different machines • includes mobile platforms • Now taken completely for granted; not always the case • HUGE thank you to OSI (open Systems Interconnect)

  4. Evolution of “connectivity” • Proprietary Systems  & “lock in” • poor connectivity not necessarily considered to be a problem by companies such as IBM and ICL… • “locked” customers into their products • not popular with customers • wanted to be able to buy freely • also a barrier to communication: • between companies • sometimes different parts of the same company! • using incompatible systems!

  5. Principles of Connectivity - 1 • For a client to connect to another computer… • the two devices need a common protocol covering all 7 OSI layers • For a network, client needs to be able to run the default protocol for that network • Example: • For a Windows Server machine to connect to a Netware server it needs to run IPX/SPX • can easily be added to the client machine’s protocol stack • connection to Netware servers then possible via hub/router and the Novell login

  6. Principles of Connectivity - 2 • Client machines on one network should also be able to connect to resources on another network: • follow principle 1 • install additional software on each client machine that will allow connection to resources using names from the other network’s resource database • Example: use a Netware printer from an XP client • set up NWLink • set up client service for Netware (CSNW)

  7. Principles of Connectivity - 3 • Client machines on one network should be able to connect to shared folders on servers on another network: • follow principle 1 • install software on the local server that will connect to the relevant remote server(s) • clients connect to the remote share via the local server

  8. Principles of Connectivity - 4 • Example: use a Netware shared directory from an XP client • install NWLInk on Windows XP clients and server • install Gateway Services for Netware (GSNW) on the relevant Windows 2003 Server • the Netware share becomes available as a Windows 2003 Server share • local clients can link to the share use the “map“ command

  9. Further (Deeper) aspects of IP addressing • An IP address is made up of four fields • Each field is represented by a single byte • Divided into two sections: • host address (first field/s) • network address (remaining field/s

  10. IPv4 Address Classes • IPv4 = 4 sets of numbers • Depending on the dividing position between “host” and “network”, IP addresses are categorised as different types (classes) w x y z

  11. IPv4 Address Classes • Several address classes: • Class A (w then x.y.z) • For networks with many hosts • High order bit in first field set to 0 • Class B (w.x then y.z) • For medium sized networks • High order bits in fields 1 and 2 set to 1-0 • Class C (w.x.y then z) • For small LANs • High order bits in fields 1,2,3,4 set to 1-1-0-1

  12. Subnet Masks • Purpose is to inform the hosts which bits in the full 32-bit IP address correspond to the network address and which bits correspond to the host address • Value depends on whether it is a class A, class B, or class C network: • Class C: 255.255.255.0 • Class B: 255.255.0.0 • Class A: 255.0.0.0

  13. Subnet Mask interaction with IPv4 addresses • A binary “mask” works by using logical AND with itself and a data value to set that value to zero (i.e. it is “masked”) • If one or more of the IPv4 numbers can be “masked”, it/they need not be included in packet headers (zero value assumed)

  14. Subnet Masks and Network Packet Optimisation • Value of subnet mark therefore relates directly to efficiency of management of network traffic • determines packet header size • should be a small as possible • Various formulae available for calculating subnet mask e.g. logical AND

  15. Logical AND in Practice • The result of the AND operation is 1 only when both bits being ANDed are 1 • otherwise, the result is 0 • IPv4 performs a logical AND comparison with the 32-bit IPv4 address and the 32-bit subnet mask • known as a bit-wise logical AND • result of is the subnet prefix

  16. Example (1) • To determine the subnet prefix of the IPv4 address configuration 131.107.189.41 with a subnet mask of 255.255.240.0… • turn both numbers into their binary equivalents, and line them up • perform the AND operation on each bit • write down the result

  17. Example (2) • IPv4 Address:     • 10000011 01101011 10111101 00101001 • Subnet Mask:   • 11111111 11111111 11110000 00000000 • Subnet Prefix:   • 10000011 01101011 10110000 00000000

  18. Subnet Masking a small (class C) network witthout doing the Maths… • Only a single subnet is involved: • e.g. 193.134.23.1 to 193.134.23.254 • (0 and 255 normally not used on last number) • up to 254 devices can be supported • Subnet mask will mask the first three numbers… • hence 255.255.255.0

  19. Subnetting a Class B network • Two IPv4 numbers involved after masking • e.g. 129.123.1.1 to 129.123.254.254 • Supports up to 255 x 254 devices (about 64K) • Optimium subnet mask depends on whether devices nearer to 254 or 64K • e.g. 5000 user network: 255.255.128.0 • 500 user network: 255.255.254.0

  20. Subnetting a Class A network • Three IPv4 numbers involved after masking • e.g. 75.0.0.0 to 75.255.255.254 • Supports network size up to 255 x 255 x 254 (about 16 million) • rarely used in practice as a single network • 255.128.0.0 would mask optimally a 10000 user network

  21. Reserved IP addresses • 127.0.0.1 to 127.255.255.255.255 • used for loopback testing • Private addresses for Internal networks: • Class A 10.0.0.0 to 10.255.255.255 • Class B 172.16.0.0 to 172.31.255.255 • Class C 192.168.0.0 to 192.168.255.255

  22. Terminal Emulation • All about making a PC or other device behave as if it was a dumb terminal (!) (thin client becomes 2D?) • achieved through software running on client that effectively bypasses the CPU for many processes and sends them to the server • Historically, terminal emulation has produced a text-based screen display • low usage of bandwidth • Windows-based terminal emulation products available for some time • but.. higher usage of bandwidth to support GUI

  23. Why Use Terminal Emulation? • Advantages: • lower TCO • makes use of old PCs (even old Pentium I, II) • saves money having to upgrade existing machines • screen response very fast • enhanced security (no use of local memory or h/d) • remote server access for administrators • remote client support • Disadvantages • extra CPU and memory demands on the server • still use some bandwidth • clients running applications locally would use zero bandwidth

  24. Terminal Emulation Options • Citrix Metaframe • very popular before Windows released Terminal Server • still an important player… • Windows Terminal Server • why bother with something else if the product is already supplied… and works?

  25. Windows Servers & Terminal Server (1) • Like Citrix, allows multiuser access to a Server at low bandwidth (e.g. using a standard telephone link) • Windows-based applications can run on the server and utilise just a user interface at the client end • low bandwidth because just keystrokes, mouse clicks and mouse movements are communicated • Standard interface: users may have different hardware, but the screen display will be the same, no matter what the platform

  26. Windows Servers & Terminal Server (2) • Terminal Server • Manages resources at the server end for each client session • Gives each user their unique desktop • Receives and processes all keystrokes and mouse actions • Directs all display output to the appropriate client • Terminal Client: • Just displays the desktop and GUI

  27. Windows Servers & Terminal Server (3) • A Terminal Services client “session” • opens on the client as a window within the existing local desktop • remote desktop runs within that window • only uses CPU power to connect with the server and display the user interface • strictly speaking a “thin” client, but uses very few local CPU cycles beyond those needed to run the operating system

  28. Windows Servers & Terminal Server (4) • Communications Protocol • RDP (Remote Desktop Protocol) • optimised to display graphical elements to the clients • application layer • runs on top of TCP/IP • like Microsoft NetMeeting, based on ITU T120 standard • http://www.imtc.org

  29. Low Hardware & OS Requirements of Terminal Services… • Windows 2000/XP: • 32Mb RAM, Pentium processor • Windows 98: • 16Mb RAM, 486 • Windows 95 (or even 3.1!!) • 16Mb RAM, 386 • Windows CE • depends on the vendor • If non-windows platform • use Citrix metaframe

  30. Client-end Terminal Services Software • Versions: • 16-bit for Windows-based computers running very old Windows for Workgroups with the 32-bit TCP/IP stack • 32-bit Windows-based computers • 64-bit with recent Windows (e.g. w2k3 r2)… • Client support for: • Windows CE Handheld PC • Windows-based terminals

  31. Applications and Terminal Services • 32-bit applications run more efficiently • using legacy 16-bit apps: • reduced number of users can be connected • increased memory overhead • 64-bit systems even more efficient..

  32. Terminal Services (Windows 2003 Enhancements) • More users supported per high-end server • Windows Management Instrumentation (WMI) provider enhances remote management capabilities • "Terminal Services Client“ -> Remote Desktop Connection • RDP 5.1 client features a much improved user interface • Remote desktop users can: • save connection settings • easily switch between windowed and full screen mode • dynamically alter their remote experience to match the available bandwidth

  33. Terminal Services & Windows 2003 - continued • Many local resources now available within the remote session, including: • client file system, smart cards, audio (output), serial ports, printers (including network), and the clipboard • Allows users to easily take advantage of the capabilities of their client device from within the remote session • e.g. files can be opened, saved and printed to the users local PC, regardless of whether the application is running locally or remotely • improved software restriction policies, roaming profile enhancements, and new application compatibility modes. • colour depth can be selected from 256 colors (8-bit) to True Color (24-bit), and resolution can be set from 640 x 480 up to 1600 x 120

  34. Terminal Servers • Preferably member servers, not domain controllers • need plenty of RAM (4-10 Mb required for each user) • recommended installed on an NTFS partition (multisession security for each users “live” data) & use fast, reliable hard disks (pref SCSI, SCSI-2 and RAID) • need a high performance network adapter card

  35. Unix Terminal Emulation • Microsoft favours FAT client • Unix favours Thin client or terminal emulation • Packages like UWIN: • runs via a PC • emulates terminal services • give features of a traditional Unix operating system on a Windows platform desktop

  36. Virtualisation (Windows 2008 Server, Citrix, VMware, etc.) • The use of software to allow a piece of hardware to run multiple operating system images at the same time • Possible to run Windows OS under Mac OS • run multiple versions of Windows OS on the same PC • Slightly different from terminal services but getting popular… • Enables the creation of a “virtual” (rather than actual) version of any software environment on the desktop, e.g. Operating Systems, a server, a storage device or networks, an application

  37. “The Cloud” • Outsourcing on a grand scale… • With connectivity via world wide web • “Back to the Future” • Quote from IBM in 1950s: • “I think there is a world market for about five computers.” attributed to J. Watson • “The cloud” will behave like just one massive mainframe computer providing all user services • no FAT clients needed… just enough processing at the client end to run a browser • could be a very small device • could use wireless protocols to connect…

  38. Web Services and The Cloud • Companies like Amazon, Google (apps), and salesforce.com have created web services (XML/http) and made them available to a wider public for storing their data • this approach benefits companies most that are experience relatively quick growth • instead of getting new storage resources every year, organisations can quickly and easily purchase more "cloud space"

  39. Cloud Services, the future, and Security • Cloud computing can offer applications as-a-service as well… • a future is predicted where everything is outsourced and no kind of local CPU is even needed • employees will simply have a monitor, keyboard, and mouse that will allow them to connect to the cloud for all of their resources (!) • but will this be secure? And what comeback will organisations have if something goes wrong?

  40. What (physically) is The Cloud • Lots of servers connected together in clusters to provide different services via the www • Attractive and powerful, but… • disadvantages of outsourcing in terms of control • and with the extra challenge that the user doesn’t know where there data physically is at a particular time… SCARY? • Server location also a matter of some concern for legal reasons…

  41. Thanks for listening

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