lecture 3: introduction to net-centric computing csci102 - introduction to information technology b...
TRANSCRIPT
Lecture 3: Introduction to Net-centric Computing
CSCI102 - Introduction to Information Technology B
ITCS905 - Fundamentals of Information Technology
Overview
This Week Background and history of networking and the
Internet Network architectures The range of specializations within net-centric
computing Networks and protocols Networked multimedia systems Distributed computing Mobile and wireless computing
Background Discussion Topics
Definitions
Describing a telecommunications system
Requirements for voice and data communications
History of telecommunications
Forces for change
Definitions
Communication “A process which allows information to
pass from a sender to one or more receivers”
“The science of transmitting information, especially symbols”
TeleAt a distance
Definitions
Circuit: " A path over which two-way communications in
any media occurs"
Line: " A communications circuit which invariably uses a
physical wire connection"
Link: "A communications circuit is subdivided into
segments known as links ”
Definitions
Channel:A general definition would be "the part of a
communications system that connects a message source with the message sink"
In this context a channel is "a one-way communications path“
Sound
If a tree falls in a forest far from any sound detector (such as a human ear or a microphone), does the tree's crash make any noise?
Sound
Sound depends on three thingsThere must be a vibrating source to set up
sound wavesA medium (such as air) to carry the wavesA receiver to detect them
Sound
If a tree falls in a forest far from any sound detector (such as a human ear or a microphone), does the tree's crash make any noise?
Sound
If it is thought of as the waves that are carried by the air, the answer is yes Wherever there are sound waves there is sound
However, if sound is defined subjectively, as a sensation in the ear, for example, the answer must be no In that case sound does not exist unless there is a
receiver present to detect it
The two definitions are equally correct
Transmission Types
Analog:" An analog signal is represented in the
form of continuously varying physical quantities"
Transmission Types
Characteristics of analog signals:Frequency (constant or varying over time)Frequency range or bandwidth ( difference
between the upper and lower frequencies)Amplitude (varying over time)
Transmission Types
Analog signals are affected by a number of different types of noise and interferenceThese affect the signal clarity and include
White noise Impulse noiseSignal to noise ratioDistortionCrosstalk
Transmission Types
Amplification of analog signals is necessary to counter signal distortion and attenuation Transmission cables are likely to act as antennas
and pick up background noise This background noise is amplified as well as the
signal This noise is cumulative so the further an analog
signal travels the more amplifiers it travels through increased noise
Transmission Types
Digital:"A signal whose states are discrete
intervals apart“
Characteristics of digital signals:Discrete and discontinuousUnipolar or bipolar
1 0 1 1 1 0 0 0 1 1 0 1 1 1 0 0 0 1
Transmission Types
Any distortion that occurs while transmitting digital signals is recovered by regeneration using repeaters
Advantages of digital transmission: Lower signal error Lower noise levels Increases line capacity Less complexity Integration of voice, data and images
Describing a Telecommunications
SystemA telecommunications system can be described by its key componentsTransmitterMediumReceiverCommunication network
Requirements for Voice and Data Communications
Voice communicationsFast< 200ms delayTelco’s <70ms round-trip-delaySpeed more important than integrity
Data communicationsData integrity vs real-time
History of Telecommunications
1837 – Wheatstone and Cooke five needle telegraph
1838 - Govt declines use of telegraph1843 - First demonstration of Telegraph and
FAX in US1845 - Morse forms company1851 - 50 telegraph companies operating1856 - Western union telegraph (WUT)
established
History of Telecommunications
1876 - WUT becomes the largest communications company - Alexander graham bell - patent on telephone
1876 - WUT decline to pay $100,000 for telephone1877 - Bell company formed1878 - Worlds first telephone exchange - Bell sues WUT and takes it over1885 - AT&T established interconnections between
regional telephone companies1889 – First automatic telephone system
History of Telecommunications
1893/94 - Bell’s patent expires
- Independent telephone companies enter the market
1911 - Bell associated companies formed
1913 - Vacuum tube patent
History of Telecommunications
1943 - Amplifiers and repeaters
1947 - Transistors
1956 - First trans-Atlantic cable laid
1957 - Launch of first satellite
1977 - Internet services provided by public carriers
History of Telecommunications
1984 - Divestiture in the US1988 - Internet provides multimedia
services - Global digital interconnectivity
standards converge1993 - Formation of global consortium for
the development of global satellite and optical digital networks
What Caused the Internet ?
Sputnik I US government felt vulnerable Creation of Advanced Research Projects Agency
The Early Years
1961 - First paper on packet-switching (PS) theory1962 - J.C.R. Licklider & W. Clark, MIT: "On-Line Man Computer Communication“ (August)1962 ARPA opened a computer research program and appointed to its head John Licklider to lead it1964 - Packet-switching networks;no single outage point
The Early Years
1966/67 - plan for computer network system called ARPANET publishedIndependent teams at MIT, the National Physics Laboratory (UK) and RAND Corporation had all been working on the feasibility of wide area networksTheir best ideas were incorporated into the ARPANET design
The Early Years
Final requirement was to design a protocol to allow the computers to send and receive messages and data, known as an interface message processor (IMPs – see RFC 1)Work on this was completed in 1968In October 1969, IMPs installed in computers at both UCLA and Stanford.
The Early Years
UCLA students would 'login' to Stanford's computer, access its databases and try to send data
The experiment was successful and the fledgling network had come into being
From Arpanet to Internet
1972, direct person-to-person communication that we now refer to as e-mail
host-to-host protocols (Telnet)
In October 1972 ARPANET went 'public'
TCP/IP design concepts
Crucial concept was that the system should have an 'open architecture‘
Each network should be able to work on its own, developing its own applications without restraint and requiring no modification to participate in the Internet
Within each network there would be a 'gateway', which would link it to the 'outside world'
TCP/IP design concepts
The gateway software would retain no information about the traffic passing through
Packages would be routed through the fastest available route
TCP/IP design concepts
The gateways between the networks would always be open route the traffic without discrimination
Operating principles would be freely available to all the networks
Going Global - 1973
First international connections to the ARPANET: university college of London (England) via NORSAR (Norway)
Ethernet
RFC 454: file transfer specification
Christmas day lockup
The Rest of the Seventies
1974 - transmission control protocol/internet protocol (TCP/IP)
1975 Operational management of Internet transferred to
DCA (now DISA) First ARPANET mailing list is created by Steve
Walker
1978 - TCP split into TCP and IP (March)
The Rest of the Seventies
1979 Computer science department research computer
network Usenet First MUD, MUD1 Internet configuration control board (ICCB) Packet radio network (PRNET) experiment starts
with DARPA funding April 12 emoticons
1980’s Expansion
The 1980’s saw a period of expansion in the internetworking community
1981BITNET, the "because it's time network"CSNET (computer science network)True names by Vernor VingeRFC 801: NCP/TCP transition plan
1980’s Expansion
1982DCA and ARPA establish the transmission
control protocol (TCP) and internet protocol (IP), as the protocol suite for ARPANET
DoD declares TCP/IP suite to be standard for DoD
1980’s Expansion
1983Cutover from Network Control Protocol
(NCP) to TCP/IP (1 January)
1984 - Domain Name System (DNS) introduced
1980’s Expansion
1986 NSFNET created (backbone speed of
56Kbps) Internet Engineering Task Force (IETF) Internet Research Task Force (IRTF)
1987Number of hosts breaks 10,000
1980’s Expansion
1988 2 November - Internet worm CERT (Computer Emergency Response
Team)DoD chooses to adopt OSI and sees use of
TCP/IP as an interim
1980’s Expansion
1989 Number of hosts breaks 100,000AARNET - Australian Academic Research
NetworkARPANET's 20th anniversary
The ‘Information Age’ Explodes
1990 ARPANET ceases to exist First remotely operated machine to be
hooked up to the Internet
The ‘Information Age’ Explodes
1991 NSF lifts restrictions on the commercial use
of the Net (March)Wide Area Information Servers (WAIS)Gopher releasedWorld-Wide Web (WWW) releasedPGP (Pretty Good Privacy) released
The ‘Information Age’ Explodes
1992 Internet Society (ISOC) is chartered
(January) IAB reconstituted as the Internet
Architecture Board and becomes part of the Internet Society
Number of hosts breaks 1,000,000
The ‘Information Age’ Explodes
1993Mosaic takes the Internet by storm
WWW proliferates at a 341,634% annual growth rate of service traffic
Gopher's growth is 997%
The ‘Information Age’ Explodes
1994 – The World discovers ‘the net’ Shopping Mall Internet Radio Spamming Governments Banking
1995 Registration of domain names is no longer free
The ‘Information Age’ Explodes
1996 A malicious cancelbot is released on USENET
wiping out more than 25,000 messages Restrictions on Internet use around the world:
China: requires users and ISPs to register with the police Germany: cuts off access to some newsgroups carried on
Compuserve Saudi Arabia: confines Internet access to universities and
hospitals Singapore: requires political and religious content providers
to register with the state New Zealand: classifies computer disks as "publications"
that can be censored and seized
The ‘Information Age’ Explodes
1997101,803 Name Servers in whois database
1998Network Solutions registers its 2 millionth
domain on 4 MayElectronic postal stamps
The ‘Information Age’ Explodes
1999Technologies of the Year: E-Trade, Online
Banking, MP3 Emerging Technologies: Net-Cell Phones,
Thin Computing, Embedded Computing Viruses of the Year: Melissa (March),
ExploreZip (June)
The ‘Information Age’ Explodes
2000RFC 2795: The Infinite Monkey Protocol Suite Hacks of the Year: RSA Security (Feb),
Apache (May), Western Union (Sep), Microsoft (Oct)
Technologies of the Year: ASP, Napster Emerging Technologies: Wireless devices,
IPv6 Viruses of the Year: Love Letter (May) Lawsuits of the Year: Napster, DeCSS
The ‘Information Age’ Explodes
2001Viruses of the Year: Code Red (Jul), Nimda
(Sep), SirCam (Jul), BadTrans (Apr, Nov) Emerging Technologies: Grid Computing,
P2P
The ‘Information Age’ Explodes
2002 New Top level Domains
.name (15 Jan), .coop (30 Jan), .aero (18 March) 2 September Abilene (Internet2) backbone deploys native IPv6 (5 Aug)
Internet2 now has 200 university, 60 corporate, and 40 affiliate members (2 Sep)
A distributed denial of service (DDoS) attack struck the 13 DNS root servers knocking out all but 5 (21-23 Oct). Amidst national security concerns, VeriSign hastens a planned relocation of one of its two DNS root servers
A new US law creates a kids-safe "dot-kids" domain (kids.us) to be implemented in 2003 (3 Dec)
RFC 3251: Electricity over IP
The ‘Information Age’ Explodes
2003 Public Interest Registry (PIR) takes over as .org registry
operator on 1 Jan By giving up .org, VeriSign is able to retain control over .com
domains The first official Swiss online election takes place in Anières
(7 Jan) The SQL Slammer worm causes one of the largest and
fastest spreading DDoS attacks ever. Taking roughly 10 minutes to spread worldwide, the worm took
down 5 of the 13 DNS root servers along with tens of thousands of other servers, and impacted a multitude of systems ranging from (bank) ATM systems to air traffic control to emergency (911) systems (25 Jan)
RFC 3514: The Security Flag in the IPv4 Header (The Evil Bit)
Definitions
Architecture From Merriam Webster’s dictionary
“A unifying or coherent form or structure” “A set of rules or outlines needed to perform
functions according to user needs” A design
The term architecture can refer to either hardware or software, or to a combination of hardware and software
The architecture of a system always defines its broad outlines, and may define precise mechanisms as well
Definitions
Communications network architecture: “A set of design principles on the basis of
which a communications network is designed and implemented to satisfy end-user needs over a period of time”
“A set of layers and protocols”
Telecommunication Network Architectures
A telecommunications network architecture is a set of design principles used as a basis for the designing and implementation of a network
It simply describes ‘what’ will be built - it does not say ‘how’
Telecommunication Network Architectures
An architecture can be A reference model such as the open systems
interconnection (OSI) reference model Intended as a model for specific product architectures
A specific product architecture, such as that for an Intel Pentium microprocessor or for IBM's OS/390 operating system
A vocabulary for describing a protocol
An example of a network architecture is RFC 2271: an architecture for describing SNMP management frameworks
Internetworking
Internetworking is the ability to communicate across networks, with connection between networks provided at the network layer [next week] by routers or, at the data link layer, by bridges and by switches An internet is a collection of internetworked
networks The Internet is the name for the global, public
internet connecting most networks and using the TCP/IP family of protocols
Classification of Network Architecture
Open vs Closed
Extent
Ownership
Service
Quality of Service(QoS)
Classification of Network Architecture
Open architectureAn open architecture allows the system to
be connected easily to devices and programs made by other manufacturers
Open architectures use off-the-shelf components and conform to approved standards
Closed architectureA closed architecture network is one
whose design is proprietary
Classification of Network Architecture
ExtentThe physical space covered by the network
Pan, LAN, man, wan Internet, intranet, extranet
Classification of Network Architecture
Service:Connection-oriented Connectionless
Quality of service(QoS)DelayReliabilityJitterThroughput
Network Basics
Networks Encompass a variety of technologiesAre created and maintained by large
number of ever changing industriesMust satisfy a significant number of often
conflicting requirements
Network Basics
"No single networking technology is best for all needs“ - Comer
Universal Service to allow any two computer to communicate Regardless of
technologies they use specific networks they are directly connected to,
as long as there exists a communication path between them