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COMP2221 Networks in Organisations Richard Henson March 2014 Week 6: Client-Server, Peer-Peer and Services across the network… 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 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 Intel EFI) graphics card not yet initiated… meanwhile, operating system's kernel and critical device drivers are loading into memory in the background… Rapid Boot-up with Windows 7 (2) Early stage of boot process bound to i/o: loading the kernel device driver files other system component files 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… Rapid Boot-up with Windows Even better with Windows 8…. or 8.1? BUT… In an organisation, the user then needs to log on… endless loading of policy files… subsequent configuration to accommodate settings into the local registry… Why use a network anyway? 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 The Lure of The Cloud 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 Groups & Group Policy in Domains Convenient for users to be put into groups Settings for group provides particular access to data & services Problems… user in wrong group(s) group has wrong settings Peer-Peer Sharing No Active Directory! Resources shared through (e.g.): File shares Printer shares Responsibility rests with the administrator of the local machine Why not Peer-Peer Networks? (formerly known as “workgroups”) Over to you? For v Against Peer-Peer Logon locally only, so… no group policies to download! much faster boot up! run client-server apps Disadvantages… no central accountability! users & computers both difficult to manage more untested software… Generally agreed that… Peer-peer networks only possible in very small organisations, where all users are IT-literate and self-reliant e.g. group of architects 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…) Controlling User and System Settings… 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… 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 What is a Policy File anyway? Collection of registry settings in a text file appropriate settings for each group can overwrite one another Can overwrite: local machine registry settings current user registry settings Group policy files should therefore only be created and used by those who know what they are doing!!! Trustworthy Software and Client-Server apps Single machine apps often go wrong.. Why? What about applications run partly on client, partly on server, with parameter passing (i.e. data transfer) across: local network? Internet? Cloud? Specifying a new Client-Server Application? First of all: What about stating requirements for software residing on a single machine Standalone software has often been developed and “missed something”… Generally OK with overtly specified requirements problem with implicit requirements… Implicit and Explicit Requirements Typically, customers only really understand/care about Explicit (Functional) Requirements e.g. a Local Authority may want a Bridge New Bridge • The expressed Functional Requirement may only be: • Direction & Length • Capacity (number of lanes) 19 [TSI/2012/183] © Copyright 2003-2012 Implicit Requirements (NFRs) In most industries… supplier gives due weight to all relevant guidance » {c.f. Ethical Principles} » including Non-Functional Requirements (NFRs) NFRs for the Bridge: • Strength (of components & overall) • Clearance required over river • known failure modes - - - - - - - - - - > NFRs & software industry? 1st Tacoma Narrows Bridge 1940-11-07 overlooked?!#! not a good track record for Trustworthiness… 20 [TSI/2012/295] © Copyright 2003-2012 Trustworthy Software Requirements (1) • Explicit (Functional) Requirement for Trustworthiness • list, accurately stated • Implicit (Non Functional) Requirement (NFR) for Trustworthiness • direct NFR for software under consideration • as collateral NFR from other software in environment 21 [TSI/2012/183] © Copyright 2003-2012 Trustworthy Software Requirement (2) • Requirements cover • whole of ICT (including ICS) • development activities to create the software (Specification, Realisation and Use) • Assurance requirements range • Due Diligence (all software) • … • to “Comprehensive” Typical NFRs (PAGICC) PAGICC Performance ARM (Availability (incl. Resilience), Reliability (incl. Robustness) & Maintainability (incl. Documentation)) Governance (Legal (incl. IPR), Regulatory, Policy) ILS (Integrated Logistic Support incl. Escrow) Compatibility (Operating Environment, Interfaces, Platforms and Dependencies) Cultural Fit (including Reputation, Brand) 23 [TSI/2012/183] © Copyright 2003-2012 Typical NFRs (QUESTESS) Quality (e.g. Faults Delivered, Fault Removal Efficacy) Usability / human factors and Accessibility Evolution (incl. Extensibility / Scalability, PDS (Post Design Services)) Standards TEA (Training, Education and Awareness) Environmental Impact Security (incl. IA, Audit/control and DPA) Safety Typical NFRs (PAGICC) Performance ARM (Availability [incl. Resilience], Reliability [incl. Robustness] & Maintainability [incl. Documentation]) Governance (Legal [incl. IPR], Regulatory, Policy) ILS (Integrated Logistic Support incl. Escrow) Compatibility (Operating Environment, Interfaces, Platforms and Dependencies) Cultural Fit (including Reputation, Brand) 25 [TSI/2012/183] © Copyright 2003-2012 Platforms and Software Trustworthiness Only through extensive testing…. over many years…