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Telecommunications Concepts

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The voice networks & the data networks. The electronics ... With central switchboard. Links = n. 09-07-K.Steenhaut & J.Tiberghien - VUB. 13. Automatic Exchange ... – PowerPoint PPT presentation

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Title: Telecommunications Concepts


1
Telecommunications Concepts
  • Chapter 1.1
  • Evolution of
  • Telecommunications

2
Contents
  • The 19th century telecommunications
  • Telegraph - Telephone
  • Digital vs. analog communications
  • The voice networks the data networks
  • The electronics revolution (1960-1980)
  • Digital sound
  • Mainframe computers with remote access
  • The first unification ISDN
  • Local area networks
  • Wide area and local area networks integration
  • The Internet
  • The research project
  • The universal computer communications medium
  • The successful unification ?

3
Contents
  • The 19th century telecommunications
  • Telegraph - Telephone
  • Digital vs. analog communications
  • The voice networks the data networks
  • The electronics revolution (1960-1980)
  • Digital sound
  • Mainframe computers with remote access
  • The first unification ISDN
  • Local area networks
  • Wide area and local area networks integration
  • The Internet
  • The research project
  • The universal computer communications medium
  • The successful unification ?

4
The Chappe Telegraph (Claude Chappe, 1763-1805)
92 out of 256 ( 488) positions represented
characters. Integrity of message could be
restored at each relay station In 1844, 534
relays linked Paris with 29 cities, covering in
total 5000 Km.
5
The Morse Telegraph Samuel Morse, 1791-1872
First electrical telegraph demonstrated in 1837
6
The Morse Telegraph
Signal strength can be restored by means of
electromechanical relays connecting separate
telegraphic circuits. On land lines, unlimited
distances can be covered, without increasing
significantly the error rate.
7
The Telephone Graham Bell, 1876.
8
Analog vs. Digital Transmission
Analog
Digital
  • Almost infinite number of states
  • External perturbations can not be distinguished
    from original signal (superposed noise)
  • Information degrades along the lines
  • Finite, small, number of states
  • Most external perturbations can be distinguished
    from original signal
  • Information can be restored in relays

9
Digital Techniques
  • How are numbers represented in electronic devices
    ?
  • Binary numbers (base 2) are used.
  • A binary digit (bit) can be represented by a
    switch
  • Value 0 switch open
  • Value 1 switch closed
  • A number with n bits can take 2 n different
    values
  • 2 bits 4 combinations
  • 00 01 10 11
  • 3 bits 8 combinations
  • 000 001 010 011 100 101 110 111
  • 8 bits ( 1 byte) 256
    combinations
  • 16 bits 65 536 combinations
  • 24 bits 16 777 216 combinations
  • 32 bits 4 294 967 296 combinations

10
Contents
  • The 19th century telecommunications
  • Telegraph - Telephone
  • Digital vs. analog communications
  • The voice networks the data networks
  • The electronics revolution (1960-1980)
  • Digital sound
  • Mainframe computers with remote access
  • The first unification ISDN
  • Local area networks
  • Wide area and local area networks integration
  • The Internet
  • The research project
  • The universal computer communications medium
  • The successful unification ?

11
The Telephone Full mesh network
Links n(n-1)/2
12
The Telephone With central switchboard
Links n
13
Automatic Exchange (1900)
Conversation with switch operator replaced by
signaling protocol - Voice analog - Signaling
digital
14
The Telephone Network
SW
Trunk lines
SW
SW
SW
SW
SW
SW
15
Telex Networks (1930-1990)
Morse code replaced by Baudot or ASCII code
16
Alphabetical Codes
Morse
ASCII
Baudot
A
a
B
C
D
E
3
9
17
Extended ASCII Character Set (8 bit)
18
Unicode (16 bit)
FFFF
19
The Dual Networks
Voice Network AnalogDigital
Data Network Digital
20
Contents
  • The 19th century telecommunications
  • Telegraph - Telephone
  • Digital vs. analog communications
  • The voice networks the data networks
  • The electronics revolution (1960-1980)
  • Digital sound
  • Mainframe computers with remote access
  • The first unification ISDN
  • Local area networks
  • Wide area and local area networks integration
  • The Internet
  • The research project
  • The universal computer communications medium
  • The successful unification ?

21
The Electronics Revolution (1970-1980)
  • Integrated circuits (chips) make electronics
    affordable.
  • Mainframe computers become very powerful
  • Mini microcomputers become very popular
  • Digital techniques offer better price/performance
    for sound applications

22
Music Records
-096 057 164 210 219 216 165 -003 -117 -183
-138 -067
Digital (CD) (44100 measurements/s)
Analog
23
Records with a scratch
-096 057 164 210 XXXX XXXX XXXX XXXX -117 -183
-138 -067
210 145 079 014 -052 -117
Analog
Digital (CD)
24
Remote Access to Computers (1970)
Star Network
Dumb Terminals
25
Integrated Services Digital Network The first
attempt to integrate voice and data
  • Voice digitized at 64 Kb/s (8000 samples/s, 8
    bit)
  • Truly digital signaling
  • A telephone connection a 64 Kb/s digital link
  • A 64 Kb/s digital link is excellent for
    connecting a terminal to a mainframe computer
  • Connection time billing inadequate for data
  • ISDN widely used for telephony
  • ISDN marginal for data applications

26
Local Area Networks (1970)
  • LANs initially introduced for
  • Printer sharing
  • File sharing
  • ...

27
The Dual Screen Desk (1980)
LAN
WAN
LAN
28
LAN-WAN Integration (1990)
WAN
LAN
LAN
29
Client - Server Systems
Interconnection Network (LANsWAN)
30
Client - Server Systems Benefits
  • Sharing of storage
  • Access to common data
  • Professional back-up facilities
  • Centralized software ( data) maintenance
  • Sharing of processing power
  • Unloading of central servers
  • Supporting local clients for exceptional needs
  • Sharing of expensive peripherals

31
Terminal Emulation sub-minimal Client-server
system
  • The personal workstations are used
  • as stand alone computers
  • as terminals connected to other computers
  • The user has to mentally switch between widely
    different user interfaces and operating systems.
  • Transferring data between local and remote
    applications is far from trivial
  • Terminal emulation is very user unfriendly !!!

32
Virtual Mainframe true Client-Server system
  • The users interface of all applications runs on
    the personal workstations.
  • For some applications, the workstation requests
    help from specialized servers. The user remains
    unaware of such requests.
  • Servers can be optimized for specific tasks
  • Virtual Mainframes can be
  • Very user friendly
  • cost effective

33
Three Tier Virtual Mainframes
High-performance Local Area Network
Corporate intranet or Internet
34
Contents
  • The 19th century telecommunications
  • Telegraph - Telephone
  • Digital vs. analog communications
  • The voice networks the data networks
  • The electronics revolution (1960-1980)
  • Digital sound
  • Mainframe computers with remote access
  • The first unification ISDN
  • Local area networks
  • Wide area and local area networks integration
  • The Internet
  • The research project
  • The universal computer communications medium
  • The successful unification ?

35
70s Need for Open Networks
  • CCITT/ISO start standardization work for
  • Open Systems Interconnection
  • ARPA finances Research on open Network
    Technology
  • a Research WAN, ARPANET
  • research on LAN interconnections
  • Combination of the two ARPA efforts resulted in
    the INTERNET

36
The Early ARPANET (1976)
London
Vince Cerf
Hawaii
56 Kbps terrestrial link
Satellite link
37
The Results
  • TCP/IP Set of Application Protocols
  • Set of communication standards allowing
    interoperability of almost all brands of
    computers.
  • Applicable to
  • Local Area Networks
  • Wide Area Networks
  • Interconnection of LANs through WANs
  • The INTERNET
  • Communication facility for the Research Community
  • Financed by US government

38
The success story of TCP/IP
  • To connect a computer to the ARPANET, TCP/IP is
    required !
  • Many different computers in use in Universities
    and research centers.
  • TCP/IP becomes THE networking software available
    on ALL machines.
  • Many stand-alone networks using TCP/IP appear due
    to the wide availability of TCP/IP and the many
    applications available for it.

39
The success story of ARPANET
  • Universities where TCP/IP was developed start
    using the ARPANET backbone as a general purpose
    communication network.
  • Other universities and research centers also want
    to get connected with the help of the NSF,
    ARPANET becomes the North American Research
    Network.
  • FREE access but Acceptable Use Policy imposed
    by ARPA on all users.
  • Exponential growth of number of users
  • Enormous help for US researchers.

40
Major Internet Changes 1989-1992
  • DARPA is no longer the major funds provider.
  • Apparition of the .COM domain
  • Backbone operated by private companies and paid
    by the US-NSF and the connected networks.
  • Acceptable Use Policy no longer required on
    the backbone, even if many of the connected
    networks still have one.
  • Commercial Internet Service Providers build
    private networks to connect their subscribers to
    the Internet.
  • The Internet has become a set of independently
    financed, cooperating regional networks.

41
Internet Cost Structure
GIANT
USA
Surfnet
NL
BE
Planet
Planet
Skynet
Uunet
Uunet
- Backbone infrastructure and neutral
interconnects paid by interconnected networks,
proportional to their access bandwidth. - Cost
of direct interconnects shared by partners.
- Not ACTUAL but POTENTIAL traffic is charged.
42
Firewalls
Firewall
Secure Intranet
Intranet
43
The Internet At last a successful integration of
voice data services ???
  • Internet has become almost as ubiquitous as the
    traditional telephone network.
  • Internet cost structure based upon potential
    usage capabilities rather than actual usage.
  • Larger and larger parts of the Internet have
    multi-media capabilities.
  • Talking over the Internet becomes a realistic
    low-cost alternative to the traditional telephone
    service.
  • Can the present Internet survive a victory over
    the traditional telephone operators ???
  • Will telephone operators themselves move their
    traffic to the Internet ???

44
The Multi-media challenge
Conclusion Data and multi-media traffic
have totally different requirements Mixing them
on a single network is technically and
economically challenging
45
Introduced concepts
  • Digital vs. Analog communications
  • Analog signals degraded by noise
  • Digital signals can be restored to their original
    shape
  • Different requirements for data and multi-media
  • Data transmission and Signaling
  • Signaling management of the data transmission
  • Client-server systems
  • The Internet
  • A set of protocols
  • A set of interconnected networks
  • Intranet
  • Part of the Internet behind a firewall.

46
Bibliography To know More about network modeling
  • Andrew Tanenbaum
  • Computer Networks
  • and Open Systems
  • Fourth Edition,
  • Prentice Hall, 2003.
  • ISBN 0-13-066102-3

47
Bibliography Om meer te leren of computer
netwerken (in dutch)
  • Andrew Tanenbaum
  • Computernetwerken
  • Vertaling Fourth Edition
  • Pearson Education Benelux 2003.
  • ISBN 90-430-0698-X

48
Bibliography Pour en apprendre d'avantage sur les
réseaux (in french)
  • Andrew Tanenbaum
  • Réseaux, 4e édition
  • Pearson, 2003
  • ISBN 2-7440-7001-7
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