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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?


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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)
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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…
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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
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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

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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)
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Typical NFRs (QUESTESS)

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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)

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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)
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Platforms and Software
Trustworthiness

Only through
extensive testing….
 over many years…