COMP 2322 Networks in Organisations Richard Henson February
COMP 2322 Networks in Organisations Richard Henson February 2016
Week 1: Computers and Computer Networks n Objectives – list advantages & disadvantages of networking computers – explain why the world is now said to be “hyperconnected” – outline requirements for a network to be “trustworthy”
Learning Outcomes (LOs) n Systematically compare client-server and peer-peer networks n Relate the various topologies, cabling, and networking technologies (including wireless technologies) to function and real world situations n Use a layered model to explain how protocols work together to deliver reliable networking functionality n Explain the roles of a network operating system in controlling communication across a network n Configure a network operating system to coordinate and control users and peripherals
Coverage of Outcomes n Historical look at evolution of networks to explain why todays networks are as they are… n Practical investigation of contemporary network architectures (i. e. cabling & wireless hardware) n Theory behind network functions & protocols – how to exploit network weakness – and ensure that software is secure (i. e. not easily hacked…)
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)
Standards n The basis of technological advancement (and human enterprise to support new technology…) n Some say standards stifle creativity (? !) – in fact, essential for developing stuff that fits together with other stuff… – especially important for communications….
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 country » National standards… – became International » International standards – initially along wires – then as radio waves
Telephone n Initially National, like Telegraph network n 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… (1) n Roman Empire, 2000 years ago – streets in cities open sewers
A Tale of Standards… (2) – Romans needed crossing places » stone paths across the street – Chariots also used street » needed spaces in stones for chariot wheels – Problem: how wide?
What width would you choose? n Suggestions… n How did the Romans Decide?
Ways to agree a Standard 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
Roman “Wheelbase” n Standard “wheelbase” width agreed (4’ 8½’’) – used for chariots throughout Roman Empire n And much later for “horse and stagecoach”
New Technology, new standard? n Continued in UK as “standard gauge” when railway tracks started (1830 s) n Was it still a good standard?
Breaking a standard? n The Great Western Railway tried to change the standard to 6’ 0’’ – “Broad Gauge”… all their tracks – wider carriages, more passenger comfort… n Other railways kept 4’ 8½’’ !!!
What happened? n GWR eventually gave up and converted all their tracks back to the standard gauge…
What happen then? n If the Great western Railway couldn’t change a standard – …. no-one could! Most railways around the world still use 4’ 8½ n Modern space rockets transported on 4’ 8½’’ track n
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 Great Western Railway have their own way? n Maybe… if an International committee agreed with them (de jure) n IETF… best ever standards body?
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… Often market-driven? n Would a modern-day GWR have their own way? n
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 All prior CCITT etc. standards were – analogue… – centrally controlled Information sent along computer networks is…. digital (!) n Internet created a new paradigm…. n – control doesn’t have to be centralised – potential range of uses of networked devices much more flexible
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 (but market-driven…) – therefore often based on specific products (usually the market leader at the time!)
What is a Standard? 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 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 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 for management systems: – ISO 9001 – ISO 14001 – ISO 27001
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 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 Big computer manufacturers in the 1960 s and 1970 s worked independently to produce their own software n Teams of researchers to develop their own systems for communicating between devices n Different research teams, different company aims, so products incompatible
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 ISO: – aware that the basic infrastructure for global digital communications was rapidly emerging in the form of the Internet – decided that the existing proprietary isolationist stance was not condusive to the growth of effective digital data communications on a worldwide basis – agreed that was needed was open systems
Open Systems n Definition: – “a computer system that is ‘open’ for the purpose of information exchange” n Open systems… – therefore not restricted to one particular manufacturers own system of communicating – 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 (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 Open
Break….
Practical Download CISCO Packet Tracer… n http: //getintopc. com/softwares/network/cisc o-packet-tracer-6 -1 -free-download/ n
Joining PCs together… n An alternative to the telephone for organisational communications! n No 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 Each group - 3 reasons for… and against n Ten minutes n
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 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 & 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 in or centralised control n Came into sharp focus with “Live Aid” concert in 1985
- Slides: 45