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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