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 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 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 T10Mbps THIN/THICK COAX ETHERNET –10 BASE T10Mbps ORIGINAL TWISTED PAIR ETHERNET –100 BASE T100Mbps FAST ETHERNET –1000 BASE T1000Mbps GIGABIT ETHERNET Ethernet Types

–10Mbps THICK & THIN ETHERNET 802.3u1995 –100Mbps FAST ETHERNET 802.3z1998 –1000Mbps GIGABIT ETHERNET (FIBRE) 802.3ab1999 –1000Mbps GIGABIT ETHERNET (COPPER) Ethernet History

PROTOCOL –CSMA/CD PHYSICAL MEDIUM –COAX –TWISTED PAIR –MULTIMODE FIBRE –SINGLEMODE FIBRE Ethernet

CSMA/CD START TRANSMITTING LISTEN FOR COLLISION CONTINUE TRANSMITTING BACK OF FOR RANDOM PERIOD COLLISION NO YES CARRIER SENSE MULTIPLE ACCESS WITH COLLISION DETECT

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