COMP 2221 Networks in Organisations Richard Henson February

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COMP 2221 Networks in Organisations Richard Henson February 2014

COMP 2221 Networks in Organisations Richard Henson February 2014

Week 1: Module Intro, Computers and Computer Networks n Objectives – list advantages &

Week 1: Module Intro, Computers and Computer Networks n Objectives – list advantages & disadvantages of networking computers – explain why the world is now called “hyperconnected” – outline requirements for a network to be trustworthy

Learning Outcomes (LOs) n n n Systematically compare client-server and peer-peer networks Relate the

Learning Outcomes (LOs) n n n Systematically compare client-server and peer-peer networks Relate the various topologies, cabling, and networking technologies (including wireless technologies) to function and real world situations Use a layered model to explain how protocols work together to deliver reliable networking functionality Explain the roles of a network operating system in controlling communication across a network Configure a network operating system to coordinate and control users and peripherals

Coverage of Outcomes n n n Historical look at evolution of networks to explain

Coverage of Outcomes n n n Historical look at evolution of networks to explain why todays networks have become the way they are… Practical investigation of contemporary network architectures (i. e. cabling & wireless hardware) Theory behind network functions & protocols – how to exploit network weakness – and ensure that software is secure (i. e. not easily hacked…) n Practicals installing and configuring network operating systems, setting up mini-networks, setting up network services, meeting user needs

History of Electricity-based Communication Networks n Used for centuries before computers… n Chronologically: –

History of Electricity-based Communication Networks n Used for centuries before computers… n Chronologically: – Telegraph (1840 s) – Telephone (1910 s) – Telex (1930 s) – Internet & digital networks (1970 s on)

Why have Standards? n The basis of technological advancement (and human enterprise to support

Why have Standards? n The basis of technological advancement (and human enterprise to support this…) Some say standards stifle creativity but essential for developing stuff that fits together… n Important for communications…. n

Each network type developed its own standards for… n n n Creation of data

Each network type developed its own standards for… n n n Creation of data Format of transmitted data Voltage Error-checking Receiving, storing, presentation of transmitted data

Standards for National and International Networks n Telegraph: – data transmitted within a particular

Standards for National and International Networks n Telegraph: – data transmitted within a particular country – National standards… becoming International n Telephone: – initially National, like Telegraph – International calling possible… required a standard » French-based standards became the Internationally recognised ones (CCITT) » Comité Consultatif International Téléphonique et Télégraphique

A Tale of Standards… n Roman Empire, AD 0 – urban streets were open

A Tale of Standards… n Roman Empire, AD 0 – urban streets were open sewers n Created Passing places created – stone paths across the street n Needed to leave spaces for chariot wheels – how wide?

What width to choose? n n Standard “wheelbase” width agreed (4’ 8½’’) Used for

What width to choose? n n Standard “wheelbase” width agreed (4’ 8½’’) Used for chariots throughout Roman Empire Revived in UK as “standard gauge” when railway tracks started (1830 s) Was it still a good standard?

Breaking a standard? n Most powerful railway company in the UK (GWR: The Great

Breaking a standard? n Most powerful railway company in the UK (GWR: The Great Western Railway) tried to change the standard width of a track to 6’ 0’’ – used the 6’ “Broad Gauge” for all their tracks – wider carriages, more passenger comfort… n Other railways maintained 4’ 8½’’ !!! n GWR eventually gave up and converted all their tracks to the standard gauge

What happen then? Well, if the Great western Railway couldn’t change a standard, no-one

What happen then? Well, if the Great western Railway couldn’t change a standard, no-one could! n most railways around the world still use the 4’ 8½ standard to this day (!) n Even the Space Shuttle was transported on 4’ 8½’’ tracks (!) n

 Lessons from this story n Large, powerful organisations try to make their own

Lessons from this story n Large, powerful organisations try to make their own standards universal n Existing standards difficult to change n Once established, standards may well be adopted world-wide – therefore need to be right!

Standards Today… n Would a modern-day GWR have their own way?

Standards Today… n Would a modern-day GWR have their own way?

CCITT, Communication Standards, and Computers n n In the early days, CCITT laid down

CCITT, Communication Standards, and Computers n n In the early days, CCITT laid down the standard… (like the Romans…) More recently, CCITT became ITU: – International Telecommunication Union n Through ITU, many CCITT standards applied to computer networks evolving in the 1980 s: – Group 3: protocol for sending fax documents across (analogue) telephone lines – Group 4: protocol for sending fax documents over ISDN (early digital) networks – “V” modem standards

Comparison of Computer & Telecoms Networks n Information sent along computer networks is digital

Comparison of Computer & Telecoms Networks n Information sent along computer networks is digital (!) – all prior CCITT etc. standards were analogue… centrally controlled n Internet changed everything…. – control doesn’t have to be centralised – potential range of uses of devices are much more flexible

Standards in Computing n Characterised by rapid change n Early emerging standard may be

Standards in Computing n Characterised by rapid change n Early emerging standard may be eclipsed by new technology n Standards usually follow many years after the products themselves have been on the market – therefore often based on specific products (usually the market leader at the time!)

Standards n Definition: – “A standard is an established or accepted model” n Communication

Standards n Definition: – “A standard is an established or accepted model” n Communication protocols… – “Elements of a communication system that are defined by an agreed set of rules, conditions, parameters or methods”

Type of Standards n De Facto – A product or service that is a

Type of Standards n De Facto – A product or service that is a standard by virtue of its widespread use by interested users n De Jure – The standard devised by a committee of the organisation or, a working group of a subcommittee of a committee of the organisation

Standards and IT Professionals n Standards: – ensure that products can communicate – identify

Standards and IT Professionals n Standards: – ensure that products can communicate – identify incompatibilities between products – provide a check that customers are buying the correct product – ensure that customers are not buying a manufacturer dependent product

ISO (International Standards Organisation) n n Been providing International standards for many areas Even

ISO (International Standards Organisation) n n Been providing International standards for many areas Even for management systems: – ISO 9001 – ISO 14001 – ISO 27001

ISO Standards Development Process n Panel of experts convened: 1. decide the contents of

ISO Standards Development Process n Panel of experts convened: 1. decide the contents of the definition of draft standard 2. proposal passed to the parent committee for ratification before publication as, first, a draft for discussion (DD)

ISO Development Process n Once ratified, proposal becomes a draft international standard – draft

ISO Development Process n Once ratified, proposal becomes a draft international standard – draft made available for a certain amount of time… – allows full scrutiny… n Once any issues have been resolved… – becomes a full ISO Standard

Proprietary Systems n n n Big computer manufacturers in the 1960 s and 1970

Proprietary Systems n n n Big computer manufacturers in the 1960 s and 1970 s worked independently to produce their own software Teams of researchers to develop their own systems for communicating between devices Different research teams, different company aims, so products incompatible

Proprietary Systems n n n Considered to be a good thing by companies such

Proprietary Systems n n n Considered to be a good thing by companies such as IBM and ICL, because it “locked” customers into their products Not popular with customers, who wanted to be able to buy more freely Also using incompatible systems was a barrier to communication: – between companies – sometimes between different parts of the same company

Open Systems n n n ISO aware that the basic infrastructure for global digital

Open Systems n n n ISO aware that the basic infrastructure for global digital communications was rapidly emerging in the form of the Internet ISO decided that the existing proprietary isolationist stance was not condusive to the growth of effective digital data communications on a world-wide basis ISO agreed that was needed was open systems

Open Systems n Definition: – “a computer system that is ‘open’ for the purpose

Open Systems n Definition: – “a computer system that is ‘open’ for the purpose of information exchange” n n Open systems are therefore not restricted to one particular manufacturers own system of communicating Open systems should provide the ability to: – interchange applications and data – between systems with different underlying hardware and software

Open Systems Interconnect (OSI) n n n Historic meetings in Geneva coordinated by ISO

Open Systems Interconnect (OSI) n n n Historic meetings in Geneva coordinated by ISO (back in 1977, 1978) Involved proprietary systems manufacturers, telecomms companies, govt representatives, researchers Agreed to produce a software model for open systems (known as OSI) – accepted that this would take DECADES to achieve – the industry could, however, at least aspire to this in new developments…

Battle Lines Drawn (old v new? ) n CCITT v ISO n Proprietary v

Battle Lines Drawn (old v new? ) n CCITT v ISO n Proprietary v Open

Break….

Break….

Another Technological advance: the PC

Another Technological advance: the PC

Joining PCs together… n Provided an alternative to the telephone for organisational communications n

Joining PCs together… n Provided an alternative to the telephone for organisational communications n Organisations longer so dependent on (expensive) Telecoms companies… or (expensive) centralised computer manufacturers

Why link PCs together anyway? (not just to annoy telecoms companies!) Small groups n

Why link PCs together anyway? (not just to annoy telecoms companies!) Small groups n Each group - 3 reasons for… and against n Ten minutes n

LANs, WANs, Standards n The PC network changed everything… – didn’t happen overnight… –

LANs, WANs, Standards n The PC network changed everything… – didn’t happen overnight… – new sets of protocols and technologies had to be developed n New classification emerged (LAN) – standards provided by engineers (IEEE) – LAN: PC/Unix networks within institutions n Existing networks known as WANs » existing standards CCITT; emerging standards ISO

OSI Model & WAN standards n People liked open systems – OSI caught on

OSI Model & WAN standards n People liked open systems – OSI caught on quicker than expected – challenge to CCITT – teamed up with IEEE (802. x standards) n In 1984, OSI became an International Standard (!) – open systems now had credibility!!! – proprietary systems had competition…

How did technology succeed in changing a world standard in the 1980 s &

How did technology succeed in changing a world standard in the 1980 s & 1990 s? n Money, money… n Cheaper to use PCs than mainframes n Cheaper to use the Internet than expensive telecom companies

Change also requires Vision! n OSI model: the world could communicate without proprietary lock

Change also requires Vision! n OSI model: the world could communicate without proprietary lock in or centralised control n Came into sharp focus with “Live Aid” concert in 1985

What makes up a LAN (1)? n Hardware: – computers and other network devices

What makes up a LAN (1)? n Hardware: – computers and other network devices » e. g. printers, web cameras – transmission media, e. g. cable, radio waves – network cards, which link the network devices to the transmission media

What makes up a LAN (2)? n Software to (just a sample…) – –

What makes up a LAN (2)? n Software to (just a sample…) – – – send/receive data provide an even flow of data between devices make sure sent data goes to the right place provide a path for data through the network make sure data is checked for corruption as it passes through the network – anything else that may need to be done to the data e. g. formatting, compression, encryption

Transfer of data through LANs (1) All done through electrical signals n Medium/media transport(s)

Transfer of data through LANs (1) All done through electrical signals n Medium/media transport(s) the signals n – insulated copper wire (cheap but effective) – fibre optic cable (expensive, high volume) – wireless (microwaves that are sent out a specific frequency)

Transfer of data through LANs (2) n Cables designed from the start to transmit

Transfer of data through LANs (2) n Cables designed from the start to transmit high volumes of digital data n Network cards provide the computermedium interface: – control flow rate and error checking of data – send/receive data at high, and even higher… speeds

Digital Mobile Phone Networks (WANs) n Couldn’t happen without – OSI model becoming an

Digital Mobile Phone Networks (WANs) n Couldn’t happen without – OSI model becoming an International Standard – evolution of microcomputer networking technology n Technology moved so fast that years later major organisations still struggling to catch up. . .

Characteristics of WANs Large geographical area n Data transfer often quite slow n Nodes

Characteristics of WANs Large geographical area n Data transfer often quite slow n Nodes can be any size as long as they can process data n – e. g. mobile cell phones; mainframes n Network infrastructure: – senders & receivers of data (network adaptors) – “boosters” of data travelling long distances – routers of data between different nodes

Network Media n Includes: – – – n standardised copper cabling standardised optical fibre

Network Media n Includes: – – – n standardised copper cabling standardised optical fibre cabling “wifi” (wireless: e/m radiation of a standardised frequency) If a cabled LAN connection exceeds: – – – 100 metres (twisted pair cabling) 185 metres (coaxial cabling – rarely used now) then a repeater (booster) is needed

Network Adaptors n Generally fit inside the computer: – either as a separate card

Network Adaptors n Generally fit inside the computer: – either as a separate card – or on the motherboard… – have their own unique “MAC address” – use own software » work with other connectivity software to control the sending and receiving of data

Network Software n Connectivity software available as “firmware” on network card – on a

Network Software n Connectivity software available as “firmware” on network card – on a peer-peer network, connectivity software is all that is needed… n If network is client-server… – complex “server” software is needed at the server end – “client” software at the client end

More Network Hardware – Nodes: computers and other intelligent devices on the network with

More Network Hardware – Nodes: computers and other intelligent devices on the network with MAC addresses – Repeaters: boost weak digital signals – Hubs: link devices & direct data round a cabling or wireless system more efficiently » most hubs are also repeaters – Switches: powerful routers that can process and filter the data in various ways, whilst hubs just send it on

Networks need management… n Two types emerged – Client-Server Networks » networked computers either

Networks need management… n Two types emerged – Client-Server Networks » networked computers either clients or servers – Peer-Peer Networks » networked computers all of equal status

Client-Server Networks n A client requests services from a server Client-server interprocess communication (IPC)

Client-Server Networks n A client requests services from a server Client-server interprocess communication (IPC) fast and reliable n Types of clients: n – computer workstation (“fat” client) – computer with limited local storage and processing (“thin” client) – printer with processing ability

Workstations n Designed to work with other computers on a peer-peer network – include

Workstations n Designed to work with other computers on a peer-peer network – include the basic networking software required: » to allow connection to the network structure » to communicate effectively with other network nodes n All computers in a peer-peer network are workstations

Servers n High-powered computers – high storage capacity – a lot of memory n

Servers n High-powered computers – high storage capacity – a lot of memory n Provide network services which are access by users through clients – requires highly specialized software collectively called a Network Operating System (NOS)

Servers in small networks n n Scenario: a single server is the central controlling

Servers in small networks n n Scenario: a single server is the central controlling point The server also looks after security on the network: – – only allows valid users to log on only allows access to resources for users that have logged on – stores appropriate “user rights” for access to its files and directories