Transcript PPT - Webcast

Telecommunications for the
future
Rob Parker
CERN IT Division
Email: [email protected]
Telecommunications
•
•
•
•
Past
Present technology
New technical developments
A personal view of:
– Which of these technologies will become
widely adopted, and in what way
– The possible effect of these new technologies
on our everyday life
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Timetable
Day 1:
Day 2:
Day 3:
Day 4:
Day 5:
History & background
Fixed (cabled) systems – present
& future
Mobile (wireless) systems –
present & future
Applications – present & future
Personal view of where will we
be in 10 years
Debate
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Early telecommunications
Physical Delivery
•
•
•
•
Runners
Horses
Carrier pigeons
Stage coaches
– Postal service
• Trains
• Motor vehicles
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Early telecommunications
Message Transmission
• “Transmission” = “to send across”
• Using:
– Noise
• Megaphones (Egyptians)
• Church bells and cannon booms (Renaissance times)
– Optical effects
• flashing light heliographs (Greeks)
• Watch towers and smoke signals (Middle Ages)
• Flashing lights and semaphores (18th. And 19th. Centuries)
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The first big breakthrough
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The Telegraph
• 1838: the invention of the telegraph
• 1844: first “long distance” telegraph
connection (between Baltimore &
Washington)
• characteristics:
– Morse code
– approximately 100 bits/sec
– very fast delivery
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Some important parameters in
a communications system
• Bandwidth
– On a point-to point link
– Global bandwidth
• End-to-end transmission delay
• Intrinsic error rate
• Maximum link (point-to-point) distance
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Parameters used to compare
early systems
• Data rate
– the rate at which the data is sent
• Message speed
– physical rate at which the message moves
• Distance between repeaters
• Bandwidth-distance product
– (units: bits*metres/sec)
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Comparison of early systems
Carrier pigeon
Megaphone
Train
Telegraph
Data rate
Message speed
Distance
between
“repeaters”
10 kbit/pigeon
70 km/h
700 km
150 kbit-m/sec
100 bits/sec
1000km/h
(but many
repeaters)
2 km
30 bit-km/sec
Very high/train
70 km/h
Virtually zero
Very high
100 bits/sec
Almost infinite
20 km
1 kbit-km/sec
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Bandwidthdistance
product
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Advantages of the telegraph
• almost infinite transmission speed
– the message could arrive before the train!
• low error rate
– re-transmission possible because of high
transmission speed
• relatively cheap
• not man-power intensive
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Next telecommunications
systems
• from the telegraph onwards:
– All telecommunications systems are virtually
instantaneous
• so will do the comparison only on:
bandwidth-distance product for longest system link,
even with repeaters
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1858: the first transatlantic
telephone cable
• the first official message (90 words) took
67 minutes
• the cable insulation failed after three
weeks (the next cable was laid in 1866)
• by 1905, there were many telegraph
cables
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Telegraph cables in 1905
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Early telephony
• 1876: the first telephone message
– 7 words from one room to the next
• by 1890, many cities had primitive
telephone systems
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1901: the first transatlantic
wireless transmission
• The letter “S” in Morse code across
the Atlantic
• It took another 10 years to establish
worldwide wireless telegraph links
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1920’s: worldwide radio links
for telephony
• each major country had a small number
of High Frequency radio stations for
long-distance telephony
• an estimated 100 such stations worldwide
• calls had to be booked long in advance
• the quality was very poor
• the cost was very high
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1956: the first transatlantic
telephone cable
• 36 simultaneous telephone channels between
Europe & North America
• this was such an increase on the existing
number of radio links (six) that it was
estimated to be sufficient for the next 15 years,
to the radio stations were closed
• a few months later, availability had triggered
demand to such an extent that they had to be
re-opened!
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1965: the first commercial
geostationary communications
satellite
• Intelsat I (Early Bird): 240 telephone
circuits
• some subsequent satellites
– 1980: Intelsat V: 12,500 telephone circuits
– 1989: Intelsat VI: 33,000 telephone circuits
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1988: the first transatlantic
fibre optic cable
• TAT-8: 40,000 telephone circuits
• some subsequent fibre optic cables
– 1992: TAT-9: 80,000 telephone circuits
– 1996: TAT-12: 300,000 telephone circuits
• there are now about 10 cables in service,
and another 10 under construction or
planned
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Data networking
• 1970’s:
– limited long distance (wide area networking)
• 1980’s:
– emergence of local area networks (LANs)
with standards
• 1990’s
– integration of these
– data networks become ubiquitous
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Telecommunications & Data
Networking
• TELECOMMUNICATIONS
• DATA NETWORKING
• Refers to voice (telephony)
and video transmission, but
with some data
• Refers to data transmission
(but with some voice & video)
• Uses circuit switching
• Uses packet switching
• Industry is conservative
• Industry is dynamic
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Trends
• There is a strong – and accelerating – trend for the
traditional telecommunications services to be provided
using data networking technology
• There is a strong – and accelerating – trend for the data
networking services to provide the same quality of
service as the traditional telecommunications services
• The two industries are consolidating
PREDICTION 1: by the year 2010, this consolidation
will be complete and the industries indistinguishable
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How are the standards
defined?
There are two categories of
Standardization Organization:
• “Government” driven
• “Industry” driven
Until fairly recently, de facto industry standards would be
submitted to a standards organization for “rubber stamping”.
Now, they are often devised by consensus, in committees.
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Standardization Organizations
“Government” driven
ISO
International Standards Organization
National
Most countries have national standards groups who are
members of ISO
ITU
International Telecommunications Union
ETSI
European Telecommunications Standards
Institute
Others
EIA, CEN, CENELEC….
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Standardization Organizations
“Industry” driven
General
IEEE (Institute of Electrical and Electronic Engineers)
Internet related
IAB (Internet Activities/Architecture Board
IRTF (Internet Research Task Force)
IETF (Internet Engineering Task Force)
Speciality related
ATMF (ATM Forum)
WAPF (WAP Forum)
DAVIC (Digital Audio-Video Council)
…….and MANY more
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“Models” and “Protocols”
• The subjects of Telecommunications and
networking are so complex that “Models” and
“Protocols” have been devised to simplify(!)
understanding
• A “Model” is like a language
– it defines terminology so people can understand
each other
• A “Protocol” is like an instruction manual
– It explains in great detail how to do a job
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Well-known Reference Models
and Protocols
• ISO (International Standardization Organisation)
– Open System Interconnection (OSI)
• TCP/IP
– TCP/IP
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OSI Reference Model (7 layer)
1.
Physical Layer (lowest)
2.
Data Link Layer
3.
Network Layer
4.
Transport Layer
5.
Session Layer
6.
Presentation Layer
7.
Application layer (highest)
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OSI Model – Physical Layer (1)
• Interfaces to the physical transmission medium
(cable/fibre/radio)
• Defines physical connection (connector)
• Transmits data as an un-structured bit stream
• BITS are exchanged
DOES NOT GUARANTEE CORRECT DELIVERY, OR
EVEN, DELIVERY
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OSI Model – Data Link Layer
(2)
• Reliable point-to-point connections between
adjacent nodes in a network
• “Framing” of data
• Detection of faulty transmission (error
detection)
• Correction of errors (typically by
retransmission)
• FRAMES are exchanged
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OSI Model – Network Layer
(3)
• Selects a route to the intended
destination, based on:
– availability
– transmission time
– cost
• PACKETS are exchanged
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OSI Model – Transport Layer
(4)
• Reliable delivery of individual messages
• Reliable delivery of continuous byte streams
• Handles multiple connections to the same
computer
• Implements “flow control”
– to avoid buffers overflowing
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OSI Model – Session &
Presentation Layers (5,6)
In many network systems the session and
presentation layers are very “thin” or
even non-existent, and so will not be
considered further
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OSI Model – Application Layer
(7)
• Handles application-specific communication
tasks
– Representation of graphics
– Transmission of information relating to cursors
• In practice, often also does the work of the
Session and Presentation layers
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TCP/IP Layers vs. OSI Layers
OSI
Application
Presentation
Session
Transport
Network
Data link
Physical
TCP/IP
Application
not used
not used
Transport
Internet
not used
not used
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Some specific terms defined
(but there will be more later!)
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Circuit switching
(Connection oriented service)
• Establishes connection
• Transfers information
• Releases connection
• Like the telephone service
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Packet switching
• (Connection-less service)
• Transmits stand-alone packets
• Packets may arrive out of order and by different routes
• Packets must be reconstructed at destination
• Packets must contain complete addressing and
sequencing information
• Like the postal service
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Quality of Service
Parameters such as:
• Guaranteed bandwidth
– for different types of information transfer
– bandwidth on demand
• Guaranteed error-free end-to-end data transfer
• Guaranteed maximum transmission delays
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Present technology & new
developments
• Fixed systems (cabled)
– Distribution
– Transmission
• Mobile systems (wireless)
– Wide area
– Local area
– Short distance
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Distribution & Transmission
• Distribution
– the transport of this information between the
delivery points and the end users
• Transmission
– the transport of information over (relatively) long
distances between delivery points near the end users
– Messages for different users are often combined
together for transmission
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Distribution & Transmission
Transmission
network
“long” distance
users
users
Distribution network
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“short” distance
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Example 1: Postal Service
• Distribution
– the transport of a letter from the post box to
the nearest post office
– the delivery of the letter by the postman
from the destination post office
• Transmission
– the transport of the letter between these two
post offices
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Example 2: Telephone Service
• Distribution
– the connection of a call from the calling
party to the nearest telephone exchange
– the connection of the call from the
destination telephone exchange to the called
party
• Transmission
– the connection of the call between these two
telephone exchanges
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Why distinguish between
Distribution and Transmission?
Because they often use different technologies
• Postal service
– Distribution: postman
– Transmission: trains & boats & planes
• Telephone service
– Distribution: individual cables to the telephone
exchange
– Transmission: multichannel connection between
exchanges
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