Copyright 2013-15 1 COMP 2410 – Networked Information Systems IC1 – The Architectures of Networked Applications Roger Clarke Xamax Consultancy, Canberra

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COMP 2410 – Networked Information Systems

IC1 – The Architecturesof Networked Applications

Roger ClarkeXamax Consultancy, Canberra

Visiting Professor, A.N.U. and U.N.S.W.

http://www.rogerclarke.com/II/NIS2410.html#L1http://www.rogerclarke.com/II/NIS2410-1 {.ppt, .pdf}

ANU RSCS, 18 March 2015

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Application Architectures

Agenda

1. The Notion of 'Architecture'2. Alternative Architectures:

.1 Master-Slave Architecture

.2 Client-Server Architecture• Cloud Computing

.3 Peer-to-Peer (P2P) Architecture

3. Networks without People

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Architecture

Elements and their Inter-Relationships

The way components fit together

The term applies to any complex systeme.g. buildings, logistical networks, human

organisations, computer networks, software

Encompasses static components

May encompass processes as well

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QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

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Elements of Internet Architecture

• Computers, incl. hosts and workstations

• Communications Links between computers:

• Physical Media (e.g. cables, telephone lines)

• Wireless Media (e.g. microwave, cellular phone)

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• Protocols defining the rules of engagement between the elements

• Software running on computers

• Human Processes to create and amend protocols

• Governance Mechanisms

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• Protocols defining the rules of engagement between the elements

• Software running on computers:

• Clients (which aredirectly used, e.g. by people)

• Servers (which provideservices to Clients)

• Intermediating Nodes, e.g. gateways and proxy-servers(which pass traffic onwards)

• Human Processes to create and amend protocols

• Governance Mechanisms

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1. Master-Slave ArchitectureStar Topology

HubDumb

Terminal

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The 'PC’ Era – Mid-Late 1970s Onwards

SmallPC

BBSin

SmallPC

SmallPCs

SmallPC

SmallPC

- to -

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2. Client-Server ArchitectureMid-1980s Onwards

ServerSoftware

inLarge

CentralHost

ClientSoftware

inSmall

RemotePC

PCsin

LocalArea

Network

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Client-Server Architecture – Internet-Mediated

Mid-1990s Onwards

Serverin

Host

Clientin

Workstation

Clientin

Workstation

Clientin

Workstation

Clientin

Workstation

Clientin

Workstation

Clientin

Workstation

Serverin

Host

Serverin

Host

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Client-Server – 'The Cloud'

• 'Server Virtualisation'• Cloudsourcing• Outsourcing

• of Applications (SaaS)• of Platform incl. OS, dev tools

(PaaS)• of Infrastructure incl. air-con

(IaaS)

http://www.rogerclarke.com/II/CCBR.html

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Business ComputingFrom Insourcing to Outsourcing

'Off-Site Hosting'

'Outsourced Facility'

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From Insourcing to Cloudsourcing

CloudSourced Facilities

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Business CloudsourcingHow is it different from Outsourcing

generally?

• Scalability ('there when it's needed')• Flexible Contractual Arrangements ('pay per

use')• Opaqueness ('let someone else worry about

details')• which means less user control:

• of the Application, through commoditisation• of Service Levels, through SLA dependence

(assuming there's an SLA, and it's negotiable)• of Host Location, through resource-virtualisation

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Levels of Cloudsourcing• Software as a Service (SAAS)

Google Gmail, Google Drive/Docs/AppsMS Office 365DropboxSalesforceMYOB LiveAccounts, Intuit Online

• Platform as a Service (PaaS)MS Azure, Sware Dev Environments, ...

• Infrastructure as a Service (IaaS) Amazon EC2, Rackspace, ...

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SaaS, incl. Consumer Computing

Email clients, usingsmtp/pop/imap

Personal Web-Sites

Dedicated Devices

Office on the Desktop

FTP-server and -client

Webmail, usinghttp / https

Flickr, Picasa

iTunes

Zoho, Google Docs

Dropbox

Functions Applications ==>> Services 1975-2000 2000-

Email

Personal Galleries

Personal Music

Doc Prep

File-Sharing

http://www.rogerclarke.com/EC/CCC.html#CAS

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Consumer Requirements and Risks – 1 of 3

The Basic Needs• Does it do what I want it to do? [Fit]• Will it be there when I want it? [Availability, Reliability]

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The Basic Protections• How do I keep going if it stays fallen over for a long time?

[Service Interruptions]• Will you respond helpfully and quickly enough when I ask for help?

[Customer Service]• Will you lose my data, or muck it up? [Data Integrity]• Do I get my data back if you fall over or withdraw the service? [Survival]• Can I move my data to another supplier? [Lateral Compatibility]• Who can I complain to if I get dudded, and will they actually help me?

[Consumer Protection]

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The Basic Protections• How do I keep going if it stays fallen over for a long time?

[Service Interruptions]• Will you respond helpfully and quickly enough when I ask for help? [Customer

Service]• Will you lose my data, or muck it up? [Data Integrity]• Do I get my data back if you fall over or withdraw the service? [Survival]• Can I move my data to another supplier? [Lateral Compatibility]• Who can I complain to if I get dudded, and will they actually help me?

[Consumer Protection]

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More Advanced Needs• Will it keep doing what it does now? [Service Integrity]• Will it stay up-to-date? [Future Fit]• Will it fall over too often? [Robustness]• Will it come back quickly after it falls over? [Resilience]• Is my service protected against you, them and the gods?

[Service Security]• If bits of it are broken, will you fix it without breaking it some more?

[Maintainability]• Can I fiddle with it a bit if I need to? [Flexibility]• Can I move my data to an upgraded version? [Forward Compatibility]• How long will old versions keep working for me?

[Backward Compatibility]• Am I breaking the law if I use the service? [Legal Compliance]

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More Advanced Protections• Am I going to get gouged? [Cost]• Can only appropriate people get in and do things?

[Authentication and Authorisation]• Can I get access to all data that you hold about me?

[Subject Access]• Is my data protected against you, them and the gods?

[Data Security]• Is my privacy protected against you, them and the gods?

[Privacy Controls]• If I terminate our relationship, will my data be irretrievably

deleted? [Fully Effective Withdrawal]• What happens to my data if I die? [Archival / Memorialisation]

http://www.rogerclarke.com/EC/CCC.html#CRR

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Key Developments Since the Mid-1990s

• Workstation Capacity (now rivals Hosts)• Workstation Diversity (vast, expanding)

desktops, laptops, handhelds, smartcards, ...phones ==> smartphones, PDAs ==> tablets, ... carburettors, fridges, ... RFID tags, ... 'things' / IoT

• Broadband Connectivity (widespread)This enables dispersion and replicationof devices capable of providing services

• Wireless Connectivity (increasingly widespread)This enables Mobilitywhich means Devices change networkswhich means their IP-addresses change

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Computing Power ‘at the Edge’

Mobiles

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3. Peer-to-Peer (P2P) ArchitectureThe Cooperative Use of Resources at

the Edge

Server & Client

inWorkstation

Server & Client

inWorkstation

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P2P – The Motivation

• Take advantage of resources that are available at the edges of the Internet

• Make each participating programboth a Client and a Server

• Each Workstation is also a Host, e.g.• a music playstation can be a mixer too• a PC can host part of a music repository• a tablet could host part of a music

catalogue

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The P2P Server-Component’s Multiple Functions

Server & Client

inWorkstation

Server & Client

inWorkstation

Network ManagementDirectory Management

Object ManagementProcess Management

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P2P – Towards a Technical Definition

P2P is a network architecture in which each node

is capable of performing each of the functions

necessary to support the network

and in practice many nodes do perform many of the functions

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Important Characteristics of P2P

• Collaboration is inherent• Clients can find Servers• Enough Devices with Enough Resources act as

Servers for discovery, and as Servers for services• ‘Single Points-of-Failure’ / Bottlenecks / Chokepoints

are avoided by means of networking dynamics • 'Free-Riding' / 'Over-Grazing' of the 'Commons'

is restrained through software and psych. features

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P2P Applications for Access to Digital Objects

• Entertainment Materials, in various formats

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P2P Applications for Access to Digital Objects

• Software:• Fixes/Patches• Releases

• Virus Signatures• Announcements, e.g. of

technical info, business info, entertainment ‘info’, sports results, promotional messages, advertisements

• News Reports, by news organisations, and by members of the public

• Emergency Services Data• Backup and Recovery

Data• Games Data, e.g. scenes

and battle configurations• Archived Messages, for

conferencing/chat/IM, and cooperative publishing

• Learning Materials, in various formats

• Entertainment Materials, in various formats

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Networks for 'Things'Artefacts / appliances / 'everyday objects' that

haveembedded computing and communications

capabilities

• TelemetryRemote data acquisition and reporting

• SCADA (Supervisory Control And Data Acquisition)Telemetry plus control messages sent back

• RFID and NFC TagsAttachments to provide short-distance wireless comms

• The Internet of Things (IoT)A vague term for inter-linking comms-capable artefacts

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Application Architectures

Agenda

1. The Notion of 'Architecture'2. Alternative Architectures:

.1 Master-Slave Architecture

.2 Client-Server Architecture• Cloud Computing

.3 Peer-to-Peer (P2P) Architecture

3. Networks without People

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COMP 2410 – Networked Information Systems

IC1 – The Architecturesof Networked Applications

Roger ClarkeXamax Consultancy, Canberra

Visiting Professor, A.N.U. and U.N.S.W.

http://www.rogerclarke.com/II/NIS2410.html#L1http://www.rogerclarke.com/II/NIS2410-1 {.ppt, .pdf}

ANU RSCS, 18 March 2015

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A Few Drill-Down Slides

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Levels of Cloudsourcingand What is and isn't Outsourced

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Cloud Reliability – The First Few YearsInferences from Media Reports

(1) Outages are not Uncommon(2) Outages Arise from Multiple Causes(3) Providers' Safeguards are Sometimes Ineffective(4) Failure Cascades are Prevalent(5) Providers have had to be Forced to be Responsive(6) Providers have often been Uninformative(7) Outages may Affect Important Ancillary Services(8) The Direct Impacts have sometimes been Significant(9) Indirect Impacts have often been Even More

Significant(10) Few Customers are Recompensed

http://www.rogerclarke.com/EC/CCEF-CO.html

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Why P2P Is Attractive• Much-Reduced Dependence on individual devices

and sub-networks (no central servers)• Robustness not Fragility (no single point-of-failure)• Resilience / Quick Recovery (inbuilt redundancy)• Resistance to Denial of Service (D)DOS Attacks

(no central servers)

• Much-Improved Scalability (proportionality)• Improved Servicing of Highly-Peaked Demand

(more devices on the demand-side implies there are also more server-resources)

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Technical Concerns about P2P

• Address Volatility: old addresses may not work(hence trust based on repetitive dealings is difficult)

• Absence of Central Control (hence risk of anarchy)

• Inadequate Server Participation (over-grazing)• Security Challenges:

• Malware, embedded or infiltrated• Surreptitious Enlistment (at least potential)• Vulnerability to Masquerade• Vulnerability to Pollution Attacks (decoys)

Documents

Copyright 2013-15 1 COMP 2410 – Networked Information Systems IC1 – The Architectures of Networked Applications Roger Clarke Xamax Consultancy, Canberra