Logsv2
- 1. NETWORKS • Covering – High speed switching fabrics – Twisted pair – Mediums – Fiber optics – Radio – Ethernet Coax
- 2. NETWORKS – Logarithms – Channel capacity – Hartley-Shannon Law – Review of the Layers – Things you need to get started on a LAN
- 3. High Speed Switching Fabrics • Aside from the Bus topologies, there are many others, with higher throughput, like • ring • Transputer Topology • Torus Topology • Cray T3D
- 4. The Transputer Topology 4 way connectivity
- 5. The Torus Topology 4 way connectivity
- 6. Torus Topology 5 way connectivity
- 7. Cray T3D, Torus Topology 6 way connectivity
- 8. Diagram of a typical packet radio setup TNC Mac ASYNC SYNC Modem Radio Serial Serial CPU Memory We left out the redundant curcuitry in the gray box to make poor mans packet
- 9. Twisted Pair • Typically a balanced digital line • 2 conductor insulated wire • Twisting the wire minimizes the electromagnetic interference • A primary medium for voice traffic • used as serial cable to hookup networks
- 10. Twisted Pair • The repeat coil (transformer) or Op-Amp can be used S+I S + S+I-(-S+I)=2S - -S -S+I I
- 11. Twisted Pair • In telephone modem terms this is known as a DAA (Data Access Arrangement).
- 12. Mediums • UTP (unshielded twisted pair) – typical voice line – Generally good for star LAN short haul 10 Mbps • STP (shielded twisted pair) – level 5 data grade (100 Mbps) • RS-422 – balanced serial data communications • RS-232 – unbalanced serial data communications
- 13. Mediums • Coax – CATV (community antenna TV) – telephone long line via FDM carries 10,000 voices – LAN-WAN – cable TV
- 14. Mediums • Fiber Optics – use total internal reflection – This occurs in a transparent medium whose index of refraction is higher that surrounding medium – optic fiber is a wave guide in the 10 raised 14 to 10 raised 15 hz range
- 15. Fiber Optics • multimode – different rays have different path lengths, loss occurs • multimode-graded index – variable core index, focuses rays more efficiently that multimode • single mode – only the axial ray passes, most efficient.
- 16. Fiber Optics • LED (light emmiting diode) – inexpensive • ILD (injection laser diode ) – more expensive (more efficient and higher bandwidth that LED). • Detectors – Photo Diodes
- 17. Fiber Optics • light propagates best at 850, 1300 and 1500 nm • 640 nm = wavelength of HE-NE red = .64 micro meters • ultra pure fused silica is best, plastic is cheapest and worst
- 18. Fiber Optics – bandwidth - 2 Gbps (typical) – smaller size and weight than copper – lower attenuation than coax – electromagnetically isolated – greater repeater spacing, 5 Gbs over 111 km w/o repeater – phasing out cable. core, one or more strands cladding, one for each fiber Jacket
- 19. Radio • Microwave – line-of-sight – parabolic dish d = 7.14 kh = distance to horizon d in meters h = height of antenna in meters k = adjustment factor, microwaves bend with the curature of the earth
- 20. Ethernet Coax • For Ethernet coax – ASIC’s which give a digital interface to a bus topology LAN – For example, the Crystal Semiconductor Corporation CS83C92 is a Coaxial Transceiver Interface on a chip
- 21. Ethernet Coax CS83C92 TX- GND TX+ TXO CD- CDS CD+ RXI RX- RX+ Shi el d
- 22. Ethernet Coax • CS83C92 – Balanced serial inputs – Uses Manchester codes – All operations with IEEE 802.3 of the 10Base5 (Ethernet) and 10Base2 (Cheapernet) standard
- 23. Ethernet Coax • CS83C92 have – equalizers – amplifiers – idle detectors, receiver squelch circuits – collision testers – oscillators – differential line drivers – (with other stuff too!!!) • A manchester code convert chip is also needed
- 24. Logarithms • Log Review if x = a y then y = log a x so if x = 210 then 10 = log 2 x
- 25. Logarithms • For example find log 2 4096 4096 = 2 y ln 4096 = y ln 2 ln 4096 = y = 12 ln 2
- 26. Logarithms so ln x log 2 x = ln 2 if base = B then ln x log10 x log B x = = ln B log10 B
- 27. Logarithms • Laws of Logarithms log a (xy) = log a x + log a y log a (x / y) = log a x − log a y log a x n = n log a x
- 28. • Intermodulation noise – results when signals at different frequencies share the same transmission medium
- 29. • the effect is to create harmonic interface at f 1 + f 2 and / or f 1 − f 2 f 1 = frequency of signal 1 f 2 = frequency of signal 2
- 30. • cause – transmitter, receiver of intervening transmission system nonlinearity
- 31. • Crosstalk – an unwanted coupling between signal paths. i.e hearing another conversation on the phone • Cause – electrical coupling
- 32. • Impluse noise – spikes, irregular pulses • Cause – lightning can severely alter data
- 33. Channel Capacity • Channel Capacity – transmission data rate of a channel (bps) • Bandwidth – bandwidth of the transmitted signal (Hz) • Noise – average noise over the channel • Error rate – symbol alteration rate. i.e. 1-> 0
- 34. Channel Capacity • if channel is noise free and of bandwidth W, then maximum rate of signal transmission is 2W • This is due to intersymbol interface
- 35. Channel Capacity • Example w=3100 Hz C=capacity of the channel c=2W=6200 bps (for binary transmission) C = 2Wlog 2 m m = # of discrete symbols
- 36. Channel Capacity • doubling bandwidth doubles the data rate if m=8 c = 2(3100 hz)log 2 8 = 18, 600 bps
- 37. Channel Capacity • doubling the number of bits per symbol also doubles the data rate (assuming an error free channel) (S/N):-signal to noise ratio signal power (S / N)dB = 10log noise power
- 38. Hartley-Shannon Law • Due to information theory developed by C.E. Shannon (1948) C:- max channel capacity in bits/second S C = w log2 (1 + ) N w:= channel bandwidth in Hz
- 39. Hartley-Shannon Law • Example W=3,100 Hz for voice grade telco lines S/N = 30 dB (typically) Ps 30 dB = 10 log Pn
- 40. Hartley-Shannon Law Ps 3 = log Pn Ps log10 =3 Pn Ps 10 3 = = 1000 Pn C = 3100 log 2 (1 + 1000) = 30,898 bps
- 41. Hartley-Shannon Law • Represents the theoretical maximum that can be achieved • They assume that we have AWGN on a channel
- 42. Hartley-Shannon Law C/W = efficiency of channel utilization bps/Hz Let R= bit rate of transmission 1 watt = 1 J / sec Eb =enengy per bit in a signal
- 43. Hartley-Shannon Law S = signal power (watts) T b = the time required to send a bit 1 R= Tb Eb = ST b Eb = energy per noise power density per hertz N0
- 44. Hartley-Shannon Law Eb S / R S = = N0 N0 kTR k=boltzman’s constant by Eb = ST b Eb S= ∴S / R = Eb Tb N0 = kTR
- 45. Hartley-Shannon Law assuming R=W=bandwidth in Hz In Decibel Notation: Eb = S −10 log R + 228. 6dbW − 10 logT N0
- 46. Hartley-Shannon Law S=signal power R= transmission rate and -10logk=228.6 So, bit rate error (BER) for digital data Eb is a decreasing function of N0 Eb For a given N0 , S must increase if R increases
- 47. Hartley-Shannon Law • Example For binary phase-shift keying Eb =8.4 dB is needed for a bit error rate N0 of 10 −4 let T= k = noise temperature = C, R=2400 bps & Pe = 10 −4 = BER
- 48. Hartley-Shannon Law • Find S Eb −S = − −10 log R + 228. 6dbW − 10log T N0 −S = −8. 4 − 10 log2400 + 228.6dbW −10 log 290 S=-161.8 dbw
- 49. ADC’s • typically are related at a convention rate, the number of bits (n) and an accuracy (+- flsb) • for example – an 8 bit adc may be related to +- 1/2 lsb • In general an n bit ADC is related to +- 1/2 lsb
- 50. ADC’s • The SNR in (dB) is therefore S SNRdB = 10 log10 N where S = 2n 1 −n −n −1 N = 2 =2 2 2n+1 SNRdB = 10 log10 2 = (20n +10)log10 2 about SNRdB = 6n + 3
- 51. Review of the Layers • Physical Layer (bits) • The Link Layer (frames) • The Network Layer (packets) • The Transport Layer • Session Layer • The Presentation Layer • The Application Layer
- 52. Physical Layer • The function is to send & receive bits (marks & spaces) • deals with – Physical connections (duplex or half duplex) – Physical service data units (PSDU’s) one bit in serial xmission, nbits in parallel xmission
- 53. Physical Layer – circuit identification – bit sequencing – notification of false conditions – deriving quality of service parameters – modulation and demodulation – signaling speed
- 54. Physical Layer – transmission of data and handshaking signals – characterization of communication media – maintains an actual electrical connection with its peers. Other layers uses virtual connections
- 55. The Link Layer • The Link Layer of data link control arranges the bits into frames • Most common protocol is ISO high-level Data Link Control Procedures (ISO 3309)
- 56. The Link Layer • This layer – Establishes and releases one or more link connections – exchanges data-link service data units (DLSDUs)-frames – identifies end-points – keeps DLSDUs / frames in proper sequence
- 57. The Link Layer – notifies the network layer when errors are detected – controls data flow – selects optional qualityof service parameters
- 58. The Network Layer • Arranges data into packets – Adds the network information to the frames to form packets • SLIP – Serial Line Internet Protocol is network layer protocol – uses the EIA-232 Physical layer – Internet protocol is a network layer protocol
- 59. The Network Layer – keep track of the network node address while routing outgoing packets and recognizing packets that are intended for the local node
- 60. The Network Layer • ARP – Address Resolution Protocol provides addresses form required by IP – User may specify the datagram route – APR will stay aware of manually generated routing tables for the datagram routing function
- 61. The Network Layer •in CCITT x.25 protocol the network layer is called the packet layer.
- 62. The Network Layer • The function provided by the network layer are – network addressing and identifiers – network connections and release – transmission of network service data units NSDU’s (packets) – quality of service parameters
- 63. The Network Layer – notifies the transport layer of errors – flow control – expedited service network – may provide sequenced delivery
- 64. The Network Layer • Two types of network layer protocols – connection oriented – connectionless
- 65. Connection Protocol • set up a virtual circuit (VC) between two end points • Advantage is that since each packet does not contain complete addressing information, the overhead is lower
- 66. Connectionless Protocol • Uses a datagram (DG) which contains complete addressing information in each packet so that it can use any variable route through the network
- 67. Connectionless Protocol • The advantage is that packets may freely choose the best available routes for the transfer rather than being stuck on a VC with variable quality
- 68. The Transport Layer • uses transport protocol data units (TPDU) • TPDU = packets + transport layer data • TCP = transmission control protocol
- 69. The Transport Layer • This layer ensures that – all data send is received completely – is sequenced – transmission of TPDU messages – multiplexing and demultiplexing to share a net connection between two or more Xport connections
- 70. The Transport Layer – error detection – error recovery – connection establishment – data xfer – release of connections
- 71. The Transport Layer • CCITT transport protocol in X.224 says there are 5 classes of transport classes – 0. simple class – 1. error recovery – 2. multiplexing – 3. error recovery and multiplexing – 4. error detection and recovery class
- 72. The Transport Layer • The amount of work done is dependent on the protocol (VC or datagram) used at the network layer
- 73. The Transport Layer • Datagrams may arrive out of sequence, in a connectionless net, and buffers may be needed to resequence • connection nets allow a leaner transport layer
- 74. Session Layer • Organizes data into SPDU (session protocol data units)
- 75. Session Layer • This layer does – dialog management – Data flow control – mapping address with name (domain name service) – graceful or abrupt disconnection – buffering data until delivery time
- 76. Session Layer • has phases of service – connection establishment – data xfer – connection release
- 77. Presentation Layer • responsible for the terminal management • Performs – transfer of syntax for character sets, text strings data display format, graphics file organization and data types
- 78. Presentation Layer – data encoding, decoding and compacting – interpret character sets ( i.e. ASCII) – code conversion
- 79. Application Layer • The only layer which does not interface with a higher one • It does – log in identification of communication partners – password checking and authority to communicate
- 80. Application Layer – determine adequacy of resources – determine acceptable quality of service – synchronization of application programs – selecting the dialog procedures – agreement on error-recovery responsibility – procedures for control of data integrity – identifying data syntax constraints
- 81. Application Layer • has 5 groups – 1. System management protocols – 2. Application management protocols – 3. System protocols – 4. Industry specific protocols – 5. Enterprise protocols
- 82. Things you need to get started on a LAN • IP ADDRESS – this a 32 bit number issued by your local IP coordinator – it is expressed as 4 numbers separated by periods – looks like 44.112.0.200.
- 83. Things you need to get started on a LAN • HOST TABLE – A file that list all the folks around you that also have IP addresses – It must have your IP address and hostname (call sign) at least
- 84. Things you need to get started on a LAN • HOST TABLE – you can get this from your coordinator – It looks like this 44.112.0.1 unix.n3cv1 44.112.0.2 w3vc 44.112.0.3 darth.wa3yoa