introduction. information is moved from tx & rx the speed at which the information is moved...
TRANSCRIPT
Introduction
• 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
Tx Rx CHANNEL
TRANSMITTER RECEIVER
• CHANNELS ARE PHYSICAL AND CAN EITHER BE
(BUT NOT LIMITED TO)– COPPER
– FIBRE
– WIRELESS
• ALSO KNOWN AS THE “TRANSMISSION MEDIUM”
Channels II
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)
• SECTION OF TEXT: “THIS IS A TEST ”– TEXT CONTAINS 14 CHARACTERS
– ASSUME 8 BITS PER CHARACTER
– TOTAL 112 BITS OF INFORMATION
Bit Rate 2
TransmissionSystem
Bit Rate Time Taken
Telex50 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
COMPARISON OF BIT RATE AND TRANSMISSION TIME
• 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
Bit Rate 3
TransmissionSystem
Bit Rate Time Taken
Telex50 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
COMPARISON OF BIT RATE AND TRANSMISSION TIME
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 special-
purpose 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 consumer-
acceptable "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
• THERE ARE LIMITS ON BIT RATE
• ALL CHANNELS HAVE AN UPPER LIMIT ON BIT RATE
• THE LIMIT IS SET BY THE SO CALLED CHANNEL
BANDWIDTH
• BANDWIDTH IS MEASURED IN MHz & GHz
– MEGAHERTZ & GIGAHERTZ (MILLIONS & BILLIONS OF
HERTZ)
• IN GENERAL THE LARGER THE BANDWIDTH THE GREATER
THE INFORMATION CARRYING CAPACITY IN Bits/sec
Bandwidth
• 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 a Network?
• 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)
What is Topology?
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 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
Ethernet
• 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
To Slow
• 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 Types
• 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 History
• PROTOCOL– CSMA/CD
• PHYSICAL MEDIUM– COAX
– TWISTED PAIR
– MULTIMODE FIBRE
– SINGLEMODE FIBRE
Ethernet
CSMA/CD
START TRANSMITTING
LISTEN FORCOLLISION
CONTINUE TRANSMITTING
BACK OF FORRANDOM PERIOD
COLLISIONNO
YES
CARRIER SENSEMULTIPLE ACCESSWITH COLLISIONDETECT
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