1. COMP2221 Networks in Organisations Richard Henson March 2014

2. Week 6: Client-Server, Peer-Peer and Services across the network… n Objectives:  Explain the role of the registry in desktop configuration, usability, and security  Explain the client-server mechanisms of typical TCP/IP-based network services and reasons why peer-peer networking is not used in most businesses  Use appropriate software tools for network services, system/network monitoring and troubleshooting

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

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

5. Rapid Boot-up with Windows n Even better with Windows 8…. n or 8.1? n

6. BUT… n In an organisation, the user then needs to log on…  endless loading of policy files…  subsequent configuration to accommodate settings into the local registry…

7. Why use a network anyway? n All organisations need to control users to some extent  provide a useable common desktop  provide other services »network printers »applications across the network »web services »email services

8. The Lure of The Cloud n Can offer:  Storage »e.g. dropbox  Platform-as-a-Service (PaaS) »e.g. Google AppEngine »incl. operating system, programming language execution environment, database, and web server  Applications Software-as-a-Service (SaaS) »salesforce information »shopping cart system

9. Groups & Group Policy in Domains n Convenient for users to be put into groups  Settings for group provides particular access to data & services n Problems…  user in wrong group(s)  group has wrong settings

10. Peer-Peer Sharing n No Active Directory! n Resources shared through (e.g.):  File shares  Printer shares n Responsibility rests with the administrator of the local machine

11. Why not Peer-Peer Networks? (formerly known as “workgroups”) n Over to you?

12. For v Against Peer-Peer n Logon locally only, so…  no group policies to download!  much faster boot up!  run client-server apps n Disadvantages…  no central accountability!  users & computers both difficult to manage  more untested software…

13. Generally agreed that… n Peer-peer networks only possible in very small organisations, where all users are IT-literate and self-reliant  e.g. group of architects n If network gets larger than 6-10 users  use a domain… (expensive!)  consider doing it all in someone else’s domain? (The Cloud… not as cheap as at first glance…)

14. Controlling User and System Settings… n Arguably the most important part of a network manager’s job  get it right: happy users, happy managers  get it wrong: »frustrated users… »angry managers…

15. Local user control and Local Policy Settings  Users and groups – exactly the same principle as domain users and domain groups »can set their own policies »applied using local logon  System settings for computer may need to be changed for particular users »e.g. on CRT monitors, lower screen refresh rate for epileptics

16. What is a Policy File anyway? n Collection of registry settings in a text file  appropriate settings for each group  can overwrite one another n Can overwrite:  local machine registry settings  current user registry settings n Group policy files should therefore only be created and used by those who know what they are doing!!!

17. Trustworthy Software and Client-Server apps n Single machine apps often go wrong..  Why? n What about applications run partly on client, partly on server, with parameter passing (i.e. data transfer) across:  local network?  Internet?  Cloud?

18. Specifying a new Client-Server Application? n First of all:  What about stating requirements for software residing on a single machine n Standalone software has often been developed and “missed something”…  Generally OK with overtly specified requirements  problem with implicit requirements…

19. Implicit and Explicit Requirements n Typically, customers only really understand/care about Explicit (Functional) Requirements  e.g. a Local Authority may want a Bridge [TSI/2012/183] © Copyright 2003-2012 19 The expressed Functional Requirement may only be: Direction & Length Capacity (number of lanes) New Bridge

20. Implicit Requirements (NFRs) n In most industries…  supplier gives due weight to all relevant guidance »{c.f. Ethical Principles} »including Non-Functional Requirements (NFRs) n NFRs for the Bridge: Strength (of components & overall)Strength (of components & overall) Clearance required over riverClearance required over river known failure modes - - - - - - - - - - >known failure modes - - - - - - - - - - > n NFRs & software industry?  overlooked?!#!  not a good track record for Trustworthiness… [TSI/2012/295] © Copyright 2003-2012 20 1 st Tacoma Narrows Bridge 1940-11-07

21. Trustworthy Software Requirements (1) Explicit (Functional) Requirement for TrustworthinessExplicit (Functional) Requirement for Trustworthiness list, accurately statedlist, accurately stated Implicit (Non Functional) Requirement (NFR) for TrustworthinessImplicit (Non Functional) Requirement (NFR) for Trustworthiness direct NFR for software under considerationdirect NFR for software under consideration as collateral NFR from other software in environmentas collateral NFR from other software in environment [TSI/2012/183] © Copyright 2003-2012 21

22. Trustworthy Software Requirement (2) Requirements coverRequirements cover whole of ICT (including ICS)whole of ICT (including ICS) development activities to create the software (Specification, Realisation and Use)development activities to create the software (Specification, Realisation and Use) Assurance requirements range Assurance requirements range Due Diligence (all software)Due Diligence (all software) … to “Comprehensive”to “Comprehensive”

23. Typical NFRs (PAGICC) PAGICC PAGICC n Performance n ARM (Availability (incl. Resilience), Reliability (incl. Robustness) & Maintainability (incl. Documentation)) n Governance (Legal (incl. IPR), Regulatory, Policy) n ILS (Integrated Logistic Support incl. Escrow) n Compatibility (Operating Environment, Interfaces, Platforms and Dependencies) n Cultural Fit (including Reputation, Brand) [TSI/2012/183] © Copyright 2003-2012 23

24. Typical NFRs (QUESTESS) n Quality (e.g. Faults Delivered, Fault Removal Efficacy) n Usability / human factors and Accessibility n Evolution (incl. Extensibility / Scalability, PDS (Post Design Services)) n Standards n TEA (Training, Education and Awareness) n Environmental Impact n Security (incl. IA, Audit/control and DPA) n Safety

25. Typical NFRs (PAGICC) n Performance n ARM (Availability [incl. Resilience], Reliability [incl. Robustness] & Maintainability [incl. Documentation]) n Governance (Legal [incl. IPR], Regulatory, Policy) n ILS (Integrated Logistic Support incl. Escrow) n Compatibility (Operating Environment, Interfaces, Platforms and Dependencies) n Cultural Fit (including Reputation, Brand) [TSI/2012/183] © Copyright 2003-2012 25

26. Platforms and Software Trustworthiness n Only through extensive testing….  over many years…