Download Unit 1 Introduction

Introduction
Channels
TRANSMITTER
RECEIVER
Tx
Rx
CHANNEL
• INFORMATION IS MOVED FROM Tx & Rx
• THE SPEED AT WHICH THE INFORMATION IS MOVED
BETWEEN Tx & Rx IS SET BY ITS “BIT RATE” ON THE
CHANNEL
Channels II
• CHANNELS ARE PHYSICAL AND CAN EITHER BE
(BUT NOT LIMITED TO)
– COPPER
– FIBRE
– WIRELESS
• ALSO KNOWN AS THE “TRANSMISSION MEDIUM”
Bit Rate 1
• 1,000 bit/s = 1 kbit/s (one kilobit or one
thousand bits per second)
• 1,000,000 bit/s = 1 Mbit/s (one megabit or one
million bits per second)
• 1,000,000,000 bit/s = 1 Gbit/s (one gigabit or
one billion bits per second)
Bit Rate 2
•
SECTION OF TEXT: “THIS IS A TEST ”
–
–
–
TEXT CONTAINS 14 CHARACTERS
ASSUME 8 BITS PER CHARACTER
TOTAL 112 BITS OF INFORMATION
Transmission
System
Telex
COMPARISON OF BIT
RATE AND
TRANSMISSION TIME
Bit Rate
Time Taken
50 bits/sec
2.3 seconds
56k Modem
56 kbits/sec
2 milliseconds
Primary rate ISDN
2 Mbits/sec
57 microseconds
FDDI
100 Mbits/sec
1.1 microseconds
Gigabit network
1 Gbits/sec
114 nanoseconds
Bit Rate 3
•
IMAGE FROM NASA:
SURFACE OF MARS
–
PICTURE CONTAINS 1080 x 602
PIXELS, AT 8 BITS PER PIXEL THERE
IS 5.2 Mbits OF INFORMATION IN THE
PICTURE
Transmission
System
Telex
COMPARISON OF BIT
RATE AND
TRANSMISSION TIME
Bit Rate
Time Taken
50 bits/sec
104,025 seconds
(about 29 hours)
56k Modem
56 kbits/sec
92.8 seconds
Primary rate ISDN
2 Mbits/sec
2.6 seconds
FDDI
100 Mbits/sec
52 milliseconds
Gigabit network
1 Gbits/sec
5.2 milliseconds
Bit Rate 4
•
Audio (MP3)
– 32 kbit/s — MW (AM) quality
– 96 kbit/s — FM quality
– 128–160 kbit/s — Standard Bitrate quality; difference can sometimes be
obvious (e.g. bass quality)
– 192 kbit/s — DAB (Digital Audio Broadcasting) quality. Quickly becoming the
new 'standard' bitrate for MP3 music; difference can be heard by few people.
– 224–320 kbit/s — Near CD Quality. Sound is near indistinguishable from
most CDs.
•
Other audio
– 800 bit/s — minimum necessary for recognizable speech (using specialpurpose FS-1015 speech codecs)
– 8 kbit/s — telephone quality (using speech codecs)
– 500 kbit/s–1 Mbit/s — lossless audio as used in formats such as FLAC,
WavPack or Monkey's Audio
– 1411 kbit/s — PCM sound format of Compact Disc Digital Audio
Bit Rate 5
• Video (MPEG2)
– 16 kbit/s — videophone quality (minimum necessary for a consumeracceptable "talking head" picture)
– 128 – 384 kbit/s — business-oriented videoconferencing system
quality
– 1 Mbit/s — VHS quality
– 5 Mbit/s — DVD quality
– 15 Mbit/s — HDTV quality
– 36 Mbit/s — HD DVD quality
– 54 Mbit/s — Blu-ray Disc quality
Bandwidth
•
•
•
THERE ARE LIMITS ON BIT RATE
•
BANDWIDTH IS MEASURED IN MHz & GHz
ALL CHANNELS HAVE AN UPPER LIMIT ON BIT RATE
THE LIMIT IS SET BY THE SO CALLED CHANNEL
BANDWIDTH
– MEGAHERTZ & GIGAHERTZ (MILLIONS & BILLIONS OF
HERTZ)
•
IN GENERAL THE LARGER THE BANDWIDTH THE GREATER
THE INFORMATION CARRYING CAPACITY IN Bits/sec
What is a Network?
•
•
A NETWORK CONSISTS OF A COLLECTION OF NODES
AND CHANNELS
A NODE CAN CAN BE ANY NUMBER OF THINGS, FOR
EXAMPLE
– COMPUTER
– PRINTER
– SCANNER
– BACKUP DRIVE
– SECURITY CAMERA
– SENSORS
What is Topology?
•
TOPOLOGY DETERMINES THE WAY IN WHICH NODES AND
CHANNELS ARE INTERCONNECTED
•
•
AN ANALOGY WOULD BE THAT OF A RAIL NETWORK
STATIONS (NODES) ARE CONNECTED TOGETHER BY RAIL
TRACK (CHANNEL)
Network Topologies
Point to Point
Network Topologies
Bus
Network Topologies
Ring
Network Topologies
Star
HUB
Network Topologies
• PHYSICAL STAR
– RING CONFIGURATION
– STAR TOPOLOGY
Network Topologies
•
COLLAPSED BACKBONE
– SIMILAR TO STAR
Network Topologies
Shared Bandwidth network
Network Topologies
Switched Bandwidth network
Network Topologies
ETHERNET
Ethernet
•
Ethernet is the most popular LAN standard in the world with
over 1 Billion installed nodes (1Billion nodes - IET Computing &
Control Engineering | February/March 2007)
•
•
The original Ethernet came out around 1979 at 10 Mbps,
and that’s where it stayed for more than 10 years
Ethernet runs over co-axial cable or twisted pair copper
wires and provides a 10 Mbps to share between all users
To Slow
•
Users were finding the 10 Mbps performance of Ethernet
too slow. This bandwidth crunch is the result of three
technological changes:
– the increased speed of computer processors
– the increased number of users on networks
– new bandwidth-intensive applications on networks
Ethernet Types
• ETHERNET
– 2/5 BASE T
10Mbps
• THIN/THICK COAX ETHERNET
– 10 BASE T
10Mbps
• ORIGINAL TWISTED PAIR ETHERNET
– 100 BASE T
100Mbps
• FAST ETHERNET
– 1000 BASE T
1000Mbps
• GIGABIT ETHERNET
Ethernet History
• 802.3
1985
– 10Mbps THICK & THIN ETHERNET
• 802.3u
1995
– 100Mbps FAST ETHERNET
• 802.3z
1998
– 1000Mbps GIGABIT ETHERNET (FIBRE)
• 802.3ab
1999
– 1000Mbps GIGABIT ETHERNET (COPPER)
Ethernet
• PROTOCOL
– CSMA/CD
• PHYSICAL MEDIUM
– COAX
– TWISTED PAIR
– MULTIMODE FIBRE
– SINGLEMODE FIBRE
CSMA/CD
START
TRANSMITTING
CARRIER SENSE
MULTIPLE ACCESS
WITH COLLISION
DETECT
BACK OF FOR
RANDOM
PERIOD
LISTEN FOR
COLLISION
YES
COLLISION
NO
CONTINUE
TRANSMITTING
Ethernet Over Copper
•
•
•
•
THIN/THICK COAX
– OBSOLETE 2/5BASET
CAT 3
– OLD INSTALLATIONS 10BASET
CAT 4
– CAT5 MADE CAT4 OBSOLETE
CAT 5
– IN MAJORITY OF INSTALLATIONS