Download 9. telecommunications

PROTOCOL
RULES & PROCEDURES
TO GOVERN TRANSMISSION
BETWEEN COMPONENTS
IN A NETWORK
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7.1
Telecommunications, Networks
ANALOG SIGNAL
• CONTINUOUS WAVEFORM
• PASSES THRU SYSTEM
• VOICE COMMUNICATIONS
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7.2
DIGITAL SIGNAL
• DISCRETE WAVEFORM
• TWO DISCRETE STATES:
– 1-BIT & 0-BIT
– ON / OFF PULSE
• DATA COMMUNICATION
• USES MODEM TO TRANSLATE
ANALOG TO DIGITAL, DIGITAL TO
ANALOG
001011101001110100101010111011110010001000010111101011010
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7.3
TELECOMMUNICATION
SYSTEM COMPONENTS
•
•
•
•
COMPUTERS
TERMINALS (Input / output devices)
COMMUNICATIONS CHANNELS
PROCESSORS (Modems; multiplexers;
front-end processors)
• COMMUNICATIONS
SOFTWARE
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7.4
COMMUNICATION
CHANNELS
MEANS BY WHICH DATA ARE
TRANSMITTED:
• TWISTED WIRES (Copper Wires) – phone
lines
• COAXIAL CABLE: (Insulated Copper
Wires) – Cable television
• FIBER-OPTIC CABLE – high speed backbone,
thousands of strands of clear glass fiber (hair),
• MICROWAVE – Terrestrial or Satellite
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7.5
FIBER OPTICS
• SUPER CLEAR GLASS STRANDS
• FAST, LIGHT, DURABLE
• BILLIONS OF BITS PER SECOND, FULL
DUPLEX (10Gbps)
• EXPENSIVE, HARDER TO INSTALL
• OFTEN USED AS BACKBONE OF
NETWORKS
PHOTO
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SIGNAL
LASER
CABLE
SIGNAL
DETECTOR
7.6
COMMUNICATIONS
CHANNELS
• TRANSMISSION SPEED: Bits per
Second (BPS) or Baud
• BANDWIDTH: Capacity of Channel;
Difference between Highest & Lowest Frequencies
BROADBAND – High speed
1.5Mbps connection
1.5MB file
8 seconds to transmit
7.7
BPS: BITS PER SECOND
KBPS: KILOBITS PER SECOND
MBPS: MEGABITS PER SECOND
GBPS: GIGABITS PER SECOND
7.8
Internet Connection Choices
Device
Upstream
Speed
Downstream
Speed
Cost per month
Modem
56Kbps
56Kbps
$20
Cable
(Coax)
100Kbps to
500Kbps
1.5Mbps to
5Mbps
$40
DSL
(Twisted pair)
90Kbps to
640Kbps
144Kbps to
2.2Mbps
$40-$100
T1 leased line
24 channels
1.544 Mbps
1.544Mbps
$1,100
T3 leased line
672 channels
44.7Mbps
44.7Mbps
$8,000
Satellite
150Kbps
300Kbps to
900Kbps
$70
7.9
OTHER SERVICES:
• DIGITAL SUBSCRIBER LINE (DSL):
enhancing capacity over copper telephone
lines
• CABLE MODEM: modem for cable TV for
high-speed access to Internet
• T1 LINE: dedicated telephone connection,
24 channels @ 1.544 megabits per second
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7.10
Internet Infrastructure
7.11
Internet backbone – made up of many
large networks (NSP’s) which
interconnect
Network Service Providers – own
internet backbone.
Examples are UUNet, CerfNet,
SprintNet, IBM, WCOM
NAP (Network Access Point) – Where
NSP’s connect.
ISP’s (Internet Service Providers) –
Local and regional delivery
subnetworks
Internet Network
Architecture
ISP
ISP
ISP
Local
ISP
Regional
ISP
ISP
NAP
NAP
ISP
ISP
NAP
NAP
ISP
ISP
ISP
ISP
Backbone
7.12
Circuit-Switched Networks
• Local and long distance telephone
companies were early models in the
1950s
• Single paths were created to connect
two parties together, called circuit
switching
7.13
Packet-Switched Networks
• The Internet uses Packet switching
– Files and messages are broken down into
packets, which are electronically labeled with
their origin and destination
– The destination computer collects the packets
and reassembles the data from the pieces in
each packet
– Each computer the packet encounters decides
the best route towards its destination
7.14
Packet-Switched Network
and Message Packets
7.15
The TCP/IP Internet Protocol
• Set of protocols developed by Vincent
Cerf and Robert Kahn
– Transmission Control Protocol (TCP)
• Controls the assembly of a message into smaller
packets before transmission, and reassembles them
once received
– Internet Protocol (IP)
• Assigns sending and destination IP
address to each packet
• Rules for routing packets from their source to their
destination
7.16
Routers – are packet switches.
• A router is connected between
networks to route packets between them.
• Have updateable maps of the networks
on the internet
• Determines the path for the packets
7.17
Open Architecture
(Internet is based on this design Philosophy)
• Independent networks should not require
any internal changes in order to be
connected to the network
• Packets that do not arrive at their
destination must be retransmitted
• Router computers do not retain
information about the packets
• No global control exists over the network
7.18
WAN – (Wide Area Network) Telecommunications
network covering a large geographic area
LAN – (Local Area Network) Connect computers
(and devices) within a limited physical area (office,
building, etc.)
7.19