COMP3122 COMP3122 Network ManagementNetwork Management

Richard HensonRichard HensonApril 2012April 2012

Week 9 – Connectivity and IP Week 9 – Connectivity and IP addressing Issuesaddressing Issues

Learning Objectives:Learning Objectives:– Explain the meaning of class A, B, C, IPv4 Explain the meaning of class A, B, C, IPv4

addressesaddresses– Apply principles of IPv4 addressing and Apply principles of IPv4 addressing and

subnet masks to the matter of optimising subnet masks to the matter of optimising packet size in a LANpacket size in a LAN

– Explain the advantages of terminal emulation Explain the advantages of terminal emulation and other ways of doing the processing and other ways of doing the processing elsewhere…elsewhere…

What is connectivity?What is connectivity?

The sum total of how well hardware & software The sum total of how well hardware & software integrate to provide smooth passage of data integrate to provide smooth passage of data between programs on different machinesbetween programs on different machines– includes mobile platformsincludes mobile platforms

Now taken completely for granted; not always Now taken completely for granted; not always the casethe case– HUGE thank you to OSI (open Systems Interconnect)HUGE thank you to OSI (open Systems Interconnect)

Evolution of “connectivity”Evolution of “connectivity” ProprietaryProprietary Systems  & “lock in” Systems  & “lock in”

– poor connectivity not necessarily poor connectivity not necessarily considered to be a problem by companies considered to be a problem by companies such as IBM and ICL…such as IBM and ICL…

» ““locked” customers into their productslocked” customers into their products– nnot popular with customersot popular with customers

» wanted to be able to buy freelywanted to be able to buy freely– also a barrier to communicationalso a barrier to communication::

» between companiesbetween companies» sometimes sometimes different parts of the same company!different parts of the same company!

using incompatible systems!using incompatible systems!

Principles of Connectivity - 1Principles of Connectivity - 1 For a client to connect to another computer…For a client to connect to another computer…

– the two devices need a common protocol covering all 7 OSI the two devices need a common protocol covering all 7 OSI layerslayers

For a network, client needs to be able to run the default For a network, client needs to be able to run the default protocol for that networkprotocol for that network

Example:Example:– For a Windows Server machine to connect to a For a Windows Server machine to connect to a

Netware server it needs to run IPX/SPXNetware server it needs to run IPX/SPX» can easily be added to the client machine’s protocol stackcan easily be added to the client machine’s protocol stack» connection to Netware servers then possible via hub/router and connection to Netware servers then possible via hub/router and

the Novell loginthe Novell login

Principles of Connectivity - 2Principles of Connectivity - 2 Client machines on one network should also Client machines on one network should also

be able to connect to resources on another be able to connect to resources on another network:network:– follow principle 1follow principle 1– install additional software on each client machine install additional software on each client machine

that will allow connection to resources using that will allow connection to resources using names from the other network’s resource names from the other network’s resource databasedatabase

Example: use a Netware printer from an XP Example: use a Netware printer from an XP clientclient– set up NWLinkset up NWLink– set up client service for Netware (CSNW)set up client service for Netware (CSNW)

Principles of Connectivity - 3Principles of Connectivity - 3 Client machines on one network should Client machines on one network should

be able to connect to shared folders on be able to connect to shared folders on servers on another network:servers on another network:– follow principle 1follow principle 1– install software on the local server that will install software on the local server that will

connect to the relevant remote server(s)connect to the relevant remote server(s)– clients connect to the remote share via the clients connect to the remote share via the

local serverlocal server

Principles of Connectivity - 4Principles of Connectivity - 4 Example: use a Netware shared Example: use a Netware shared

directory from an XP clientdirectory from an XP client– install NWLInk on Windows XP clients and serverinstall NWLInk on Windows XP clients and server– install Gateway Services for Netware (GSNW) on install Gateway Services for Netware (GSNW) on

the relevant Windows 2003 Serverthe relevant Windows 2003 Server– the Netware share becomes available as a the Netware share becomes available as a

Windows 2003 Server shareWindows 2003 Server share– local clients can link to the share use the “map“ local clients can link to the share use the “map“

commandcommand

Further (Deeper) aspects of Further (Deeper) aspects of IP addressingIP addressing

An IP address is made up of four fieldsAn IP address is made up of four fields Each field is represented by a single Each field is represented by a single

bytebyte Divided into two sections:Divided into two sections:

– host address (first field/s)host address (first field/s)– network address (remaining field/snetwork address (remaining field/s

IPv4 Address ClassesIPv4 Address Classes

IPv4 = 4 sets of numbersIPv4 = 4 sets of numbers Depending on the dividing position Depending on the dividing position

between “host” and “network”, IP between “host” and “network”, IP addresses are categorised as different addresses are categorised as different types (classes)types (classes)

w x y z

IPv4 Address ClassesIPv4 Address Classes Several address classes:Several address classes:

– Class A (w then x.y.z)Class A (w then x.y.z)» For networks with many hostsFor networks with many hosts» High order bit in first field set to 0High order bit in first field set to 0

– Class B (w.x then y.z)Class B (w.x then y.z)» For medium sized networksFor medium sized networks» High order bits in fields 1 and 2 set to 1-0High order bits in fields 1 and 2 set to 1-0

– Class C (w.x.y then z)Class C (w.x.y then z)» For small LANsFor small LANs» High order bits in fields 1,2,3,4 set to 1-1-0-1High order bits in fields 1,2,3,4 set to 1-1-0-1

Subnet MasksSubnet Masks Purpose is to inform the hosts which bits in Purpose is to inform the hosts which bits in

the full 32-bit IP address correspond to the the full 32-bit IP address correspond to the network address and which bits correspond to network address and which bits correspond to the host addressthe host address

Value depends on whether it is a class A, Value depends on whether it is a class A, class B, or class C network:class B, or class C network:– Class C: 255.255.255.0Class C: 255.255.255.0– Class B: 255.255.0.0Class B: 255.255.0.0– Class A: 255.0.0.0Class A: 255.0.0.0

Subnet Mask interaction with Subnet Mask interaction with IPv4 addressesIPv4 addresses

A binary “mask” works by using logical A binary “mask” works by using logical AND with itself and a data value to set AND with itself and a data value to set that value to zero (i.e. it is “masked”)that value to zero (i.e. it is “masked”)

If one or more of the IPv4 numbers can If one or more of the IPv4 numbers can be “masked”, it/they need not be be “masked”, it/they need not be included in packet headers (zero value included in packet headers (zero value assumed)assumed)

Subnet Masks and Network Subnet Masks and Network Packet OptimisationPacket Optimisation

Value of subnet mark therefore relates Value of subnet mark therefore relates directly to efficiency of management of directly to efficiency of management of network trafficnetwork traffic– determines packet header sizedetermines packet header size

» should be a small as possible should be a small as possible Various formulae available for Various formulae available for

calculating subnet mask e.g. logical ANDcalculating subnet mask e.g. logical AND

Logical AND in PracticeLogical AND in Practice The result of the AND operation is 1 only The result of the AND operation is 1 only

when both bits being ANDed are 1when both bits being ANDed are 1– otherwise, the result is 0otherwise, the result is 0

IPv4 performs a logical AND comparison IPv4 performs a logical AND comparison with the 32-bit IPv4 address and the 32-with the 32-bit IPv4 address and the 32-bit subnet maskbit subnet mask– known as a bit-wise logical ANDknown as a bit-wise logical AND– result of is the subnet prefixresult of is the subnet prefix

Example (1)Example (1)

To determine the subnet prefix of the To determine the subnet prefix of the IPv4 address configuration IPv4 address configuration 131.107.189.41 with a subnet mask of 131.107.189.41 with a subnet mask of 255.255.240.0…255.255.240.0…– turn both numbers into their binary turn both numbers into their binary

equivalents, and line them upequivalents, and line them up– perform the AND operation on each bitperform the AND operation on each bit– write down the resultwrite down the result

Example (2)Example (2)

IPv4 Address:    IPv4 Address:    – 10000011 01101011 10111101 0010100110000011 01101011 10111101 00101001

Subnet Mask:  Subnet Mask:  – 11111111 11111111 11110000 0000000011111111 11111111 11110000 00000000

Subnet Prefix:  Subnet Prefix:  – 10000011 01101011 10110000 0000000010000011 01101011 10110000 00000000

Subnet Masking Subnet Masking a small (class C) network a small (class C) network

witthout doing the Maths…witthout doing the Maths… Only a single subnet is involved:Only a single subnet is involved:

– e.g. 193.134.23.1 to 193.134.23.254 e.g. 193.134.23.1 to 193.134.23.254 » (0 and 255 normally not used on last number)(0 and 255 normally not used on last number)

– up to 254 devices can be supportedup to 254 devices can be supported Subnet mask will mask the first three Subnet mask will mask the first three

numbers…numbers…– hence 255.255.255.0hence 255.255.255.0

Subnetting a Class B networkSubnetting a Class B network Two IPv4 numbers involved after maskingTwo IPv4 numbers involved after masking e.g. 129.123.1.1 to 129.123.254.254e.g. 129.123.1.1 to 129.123.254.254 Supports up to 255 x 254 devices (about Supports up to 255 x 254 devices (about

64K)64K) Optimium subnet mask depends on Optimium subnet mask depends on

whether devices nearer to 254 or 64Kwhether devices nearer to 254 or 64K– e.g. 5000 user network: e.g. 5000 user network: 255.255.128.0255.255.128.0– 500 user network: 255.255.254.0500 user network: 255.255.254.0

Subnetting a Class A networkSubnetting a Class A network Three IPv4 numbers involved after Three IPv4 numbers involved after

maskingmasking e.g. 75.0.0.0 to 75.255.255.254e.g. 75.0.0.0 to 75.255.255.254 Supports network size up to 255 x 255 x Supports network size up to 255 x 255 x

254 (about 16 million)254 (about 16 million)– rarely used in practice as a single networkrarely used in practice as a single network– 255.128.0.0 would mask optimally a 10000 255.128.0.0 would mask optimally a 10000

user networkuser network

Reserved IP addressesReserved IP addresses

127.0.0.1 to 127.255.255.255.255127.0.0.1 to 127.255.255.255.255– used for loopback testingused for loopback testing

Private addresses for Internal networks:Private addresses for Internal networks:– Class A 10.0.0.0 to 10.255.255.255Class A 10.0.0.0 to 10.255.255.255– Class B 172.16.0.0 to 172.31.255.255Class B 172.16.0.0 to 172.31.255.255– Class C 192.168.0.0 to 192.168.255.255Class C 192.168.0.0 to 192.168.255.255

Terminal EmulationTerminal Emulation All about making a PC or other device behave All about making a PC or other device behave

as if it was a dumb terminal (!)as if it was a dumb terminal (!)(thin client becomes 2D?)(thin client becomes 2D?)– achieved through software running on client that achieved through software running on client that

effectively bypasses the CPU for many processes effectively bypasses the CPU for many processes and sends them to the serverand sends them to the server

Historically, terminal emulation has produced Historically, terminal emulation has produced a text-based screen displaya text-based screen display– low usage of bandwidthlow usage of bandwidth

Windows-based terminal emulation products Windows-based terminal emulation products available for some timeavailable for some time– but.. higher usage of bandwidth to support GUIbut.. higher usage of bandwidth to support GUI

Why Use Terminal Why Use Terminal Emulation?Emulation?

Advantages:Advantages:– lower TCOlower TCO

» makes use of old PCs (even old Pentium I, II)makes use of old PCs (even old Pentium I, II)» saves money having to upgrade existing machinessaves money having to upgrade existing machines

– screen response very fastscreen response very fast– enhanced security (no use of local memory or h/d)enhanced security (no use of local memory or h/d)– remote server access for administratorsremote server access for administrators– remote client supportremote client support

DisadvantagesDisadvantages– extra CPU and memory demands on the serverextra CPU and memory demands on the server– still use some bandwidthstill use some bandwidth

» clients running applications locally would use zero bandwidthclients running applications locally would use zero bandwidth

Terminal Emulation OptionsTerminal Emulation Options Citrix MetaframeCitrix Metaframe

– very popular before Windows released very popular before Windows released Terminal ServerTerminal Server

– still an important player…still an important player… Windows Terminal ServerWindows Terminal Server

– why bother with something else if the why bother with something else if the product is already supplied… and works?product is already supplied… and works?

Windows Servers & Windows Servers & Terminal Server (1)Terminal Server (1)

Like Citrix, allows multiuser access to a Like Citrix, allows multiuser access to a Server at low bandwidth (e.g. using a Server at low bandwidth (e.g. using a standard telephone link)standard telephone link)

Windows-based applications can run on the Windows-based applications can run on the server and utilise just a user interface at the server and utilise just a user interface at the client endclient end– low bandwidth because just keystrokes, mouse low bandwidth because just keystrokes, mouse

clicks and mouse movements are communicatedclicks and mouse movements are communicated Standard interface: users may have different Standard interface: users may have different

hardware, but the screen display will be the hardware, but the screen display will be the same, no matter what the platformsame, no matter what the platform

Windows Servers & Windows Servers & Terminal Server (2)Terminal Server (2)

Terminal ServerTerminal Server– Manages resources at the server end for each client sessionManages resources at the server end for each client session– Gives each user their unique desktopGives each user their unique desktop– Receives and processes all keystrokes and mouse actionsReceives and processes all keystrokes and mouse actions– Directs all display output to the appropriate clientDirects all display output to the appropriate client

Terminal Client:Terminal Client:– Just displays the desktop and GUIJust displays the desktop and GUI

Windows Servers & Windows Servers & Terminal Server (3)Terminal Server (3)

A Terminal Services client “session”A Terminal Services client “session”– opens on the client as a window within the existing opens on the client as a window within the existing

local desktoplocal desktop– remote desktop runs within that windowremote desktop runs within that window– only uses CPU power to connect with the server only uses CPU power to connect with the server

and display the user interfaceand display the user interface– strictly speaking a “thin” client, but uses very few strictly speaking a “thin” client, but uses very few

local CPU cycles beyond those needed to run the local CPU cycles beyond those needed to run the operating systemoperating system

Windows Servers & Windows Servers & Terminal Server (4)Terminal Server (4)

Communications ProtocolCommunications Protocol– RDP (Remote Desktop Protocol)RDP (Remote Desktop Protocol)– optimised to display graphical elements to optimised to display graphical elements to

the clientsthe clients– application layerapplication layer– runs on top of TCP/IPruns on top of TCP/IP– like Microsoft NetMeeting, based on ITU like Microsoft NetMeeting, based on ITU

T120 standardT120 standard» http://www.imtc.org

Low Hardware & OS Requirements Low Hardware & OS Requirements of Terminal Services…of Terminal Services… Windows 2000/XP:Windows 2000/XP:

– 32Mb RAM, Pentium processor32Mb RAM, Pentium processor Windows 98:Windows 98:

– 16Mb RAM, 48616Mb RAM, 486 Windows 95 (or even 3.1!!)Windows 95 (or even 3.1!!)

– 16Mb RAM, 38616Mb RAM, 386 Windows CEWindows CE

– depends on the vendordepends on the vendor If non-windows platformIf non-windows platform

– use Citrix metaframeuse Citrix metaframe

Client-end Terminal Client-end Terminal Services SoftwareServices Software

Versions:Versions:– 16-bit for Windows-based computers running very 16-bit for Windows-based computers running very

old Windows for Workgroups with the 32-bit old Windows for Workgroups with the 32-bit TCP/IP stackTCP/IP stack

– 32-bit Windows-based computers32-bit Windows-based computers– 64-bit with recent Windows (e.g. w2k3 r2)…64-bit with recent Windows (e.g. w2k3 r2)…

Client support for:Client support for:– Windows CE Handheld PCWindows CE Handheld PC– Windows-based terminalsWindows-based terminals

Applications and Applications and Terminal ServicesTerminal Services

32-bit applications run more 32-bit applications run more efficientlyefficiently– using legacy 16-bit apps:using legacy 16-bit apps:

» reduced number of users can be connectedreduced number of users can be connected» increased memory overheadincreased memory overhead

64-bit systems even more efficient..64-bit systems even more efficient..

Terminal Services Terminal Services (Windows 2003 Enhancements)(Windows 2003 Enhancements)

More users supported per high-end serverMore users supported per high-end server Windows Management Instrumentation (WMI) Windows Management Instrumentation (WMI)

provider enhances remote management capabilitiesprovider enhances remote management capabilities "Terminal Services Client“ -> Remote Desktop "Terminal Services Client“ -> Remote Desktop

ConnectionConnection– RDP 5.1 client features a much improved user interfaceRDP 5.1 client features a much improved user interface

Remote desktop users can:Remote desktop users can:– save connection settingssave connection settings– easily switch between windowed and full screen modeeasily switch between windowed and full screen mode– dynamically alter their remote experience to match the dynamically alter their remote experience to match the

available bandwidthavailable bandwidth

Terminal Services Terminal Services & Windows 2003 - & Windows 2003 - continuedcontinued

Many local resources now available within the remote Many local resources now available within the remote session, including:session, including:– client file system, smart cards, audio (output), serial ports, client file system, smart cards, audio (output), serial ports,

printers (including network), and the clipboardprinters (including network), and the clipboard Allows users to easily take advantage of the Allows users to easily take advantage of the

capabilities of their client device from within the capabilities of their client device from within the remote sessionremote session– e.g. files can be opened, saved and printed to the users e.g. files can be opened, saved and printed to the users

local PC, regardless of whether the application is running local PC, regardless of whether the application is running locally or remotely locally or remotely

– improved software restriction policies, roaming profile improved software restriction policies, roaming profile enhancements, and new application compatibility modes.enhancements, and new application compatibility modes.

– colour depth can be selected from 256 colors (8-bit) to True 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 Color (24-bit), and resolution can be set from 640 x 480 up to 1600 x 120to 1600 x 120

Terminal ServersTerminal Servers Preferably member servers, not domain Preferably member servers, not domain

controllerscontrollers– need plenty of RAM (4-10 Mb required for need plenty of RAM (4-10 Mb required for

each user)each user)– recommended installed on an NTFS recommended installed on an NTFS

partition (multisession security for each partition (multisession security for each users “live” data) & use fast, reliable hard users “live” data) & use fast, reliable hard disks (pref SCSI, SCSI-2 and RAID)disks (pref SCSI, SCSI-2 and RAID)

– need a high performance network adapter need a high performance network adapter cardcard

Unix Unix Terminal EmulationTerminal Emulation

Microsoft favours FAT clientMicrosoft favours FAT client Unix favours Thin client or terminal Unix favours Thin client or terminal

emulationemulation– Packages like UWIN:Packages like UWIN:

» runs via a PCruns via a PC» emulates terminal servicesemulates terminal services» give features of a traditional Unix operating system give features of a traditional Unix operating system

on a Windows platform desktopon a Windows platform desktop

Virtualisation (Windows 2008 Virtualisation (Windows 2008 Server, Citrix, VMware, etc.)Server, Citrix, VMware, etc.)

The use of software to allow a The use of software to allow a piece of hardware to run multiple piece of hardware to run multiple operating system images at the operating system images at the same timesame time– Possible to run Windows OS Possible to run Windows OS

under Mac OSunder Mac OS– run multiple versions of Windows run multiple versions of Windows

OS on the same PCOS on the same PC Slightly different from terminal Slightly different from terminal

services but getting popular…services but getting popular… Enables the creation of a “virtual” Enables the creation of a “virtual”

(rather than actual) version of any (rather than actual) version of any software environment on the software environment on the desktop, e.g. Operating Systems, desktop, e.g. Operating Systems, a server, a storage device or a server, a storage device or networks, an applicationnetworks, an application

““The Cloud”The Cloud” Outsourcing on a grand scale…Outsourcing on a grand scale…

– With connectivity via world wide webWith connectivity via world wide web ““Back to the Future”Back to the Future”

– Quote from IBM in 1950s:Quote from IBM in 1950s:» ““I think there is a world market for about five computers.” I think there is a world market for about five computers.”

attributed to J. Watsonattributed to J. Watson– ““The cloud” will behave like just one massive The cloud” will behave like just one massive

mainframe computer providing all user servicesmainframe computer providing all user services– no FAT clients needed… just enough processing at no FAT clients needed… just enough processing at

the client end to run a browserthe client end to run a browser» could be a very small devicecould be a very small device» could use wireless protocols to connect…could use wireless protocols to connect…

Web Services and The CloudWeb Services and The Cloud Companies like Amazon, Google Companies like Amazon, Google

(apps), and salesforce.com have (apps), and salesforce.com have created web services (XML/http) and created web services (XML/http) and made them available to a wider public made them available to a wider public for storing their datafor storing their data– this approach benefits companies most this approach benefits companies most

that are experience relatively quick growththat are experience relatively quick growth– instead of getting new storage resources instead of getting new storage resources

every year, organisations can quickly and every year, organisations can quickly and easily purchase more "cloud space" easily purchase more "cloud space"

Cloud Services, the future, Cloud Services, the future, and Securityand Security

Cloud computing can offer applications as-a-Cloud computing can offer applications as-a-service as well…service as well…– a future is predicted where everything is a future is predicted where everything is

outsourced and no kind of local CPU is even outsourced and no kind of local CPU is even neededneeded

– employees will simply have a monitor, keyboard, employees will simply have a monitor, keyboard, and mouse that will allow them to connect to the and mouse that will allow them to connect to the cloud for all of their resources (!)cloud for all of their resources (!)

– but will this be secure? And what comeback will but will this be secure? And what comeback will organisations have if something goes wrong?organisations have if something goes wrong?

What (physically) is The CloudWhat (physically) is The Cloud Lots of servers connected together in Lots of servers connected together in

clusters to provide different services via clusters to provide different services via the wwwthe www– Attractive and powerful, but… Attractive and powerful, but… – disadvantagesdisadvantages of outsourcing in terms of of outsourcing in terms of

controlcontrol» and with the extra challenge that the user doesn’t know and with the extra challenge that the user doesn’t know

where there data physically is at a particular time… where there data physically is at a particular time… SCARY?SCARY?

Server location also a matter of some Server location also a matter of some concern for legal reasons…concern for legal reasons…

Thanks for listeningThanks for listening