NETWORKS Covering High speed switching fabrics Twisted pair
NETWORKS • Covering – High speed switching fabrics – Twisted pair – Mediums – Fiber optics – Radio – Ethernet Coax
NETWORKS – Logarithms – Channel capacity – Hartley-Shannon Law – Review of the Layers – Things you need to get started on a LAN
High Speed Switching Fabrics • Aside from the Bus topologies, there are many others, with higher throughput, like • ring • Transputer Topology • Torus Topology • Cray T 3 D
The Transputer Topology 4 way connectivity
The Torus Topology 4 way connectivity
Torus Topology 5 way connectivity
Cray T 3 D, Torus Topology 6 way connectivity
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
Twisted Pair • The repeat coil (transformer) or Op -Amp can be used
Twisted Pair • In telephone modem terms this is known as a DAA (Data Access Arrangement).
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
Mediums • Coax – CATV (community antenna TV) – telephone long line via FDM carries 10, 000 voices – LAN-WAN – cable TV
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
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.
Fiber Optics • LED (light emmiting diode) – inexpensive • ILD (injection laser diode ) – more expensive (more efficient and higher bandwidth that LED). • Detectors – Photo Diodes
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
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.
Radio • Microwave – line-of-sight – parabolic dish
Ethernet Coax • For Ethernet coax – ASIC’s which give a digital interface to a bus topology LAN – For example, the Crystal Semiconductor Corporation CS 83 C 92 is a Coaxial Transceiver Interface on a chip
Ethernet Coax
Ethernet Coax • CS 83 C 92 – Balanced serial inputs – Uses Manchester codes – All operations with IEEE 802. 3 of the 10 Base 5 (Ethernet) and 10 Base 2 (Cheapernet) standard
Ethernet Coax • CS 83 C 92 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
Logarithms • Log Review
Logarithms • For example
Logarithms
Logarithms • Laws of Logarithms
• Intermodulation noise – results when signals at different frequencies share the same transmission medium
• the effect is to create harmonic interface at
• cause – transmitter, receiver of intervening transmission system nonlinearity
• Crosstalk – an unwanted coupling between signal paths. i. e hearing another conversation on the phone • Cause – electrical coupling
• Impluse noise – spikes, irregular pulses • Cause – lightning can severely alter data
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
Channel Capacity • if channel is noise free and of bandwidth W, then maximum rate of signal transmission is 2 W • This is due to intersymbol interface
Channel Capacity • Example w=3100 Hz C=capacity of the channel c=2 W=6200 bps (for binary transmission) m = # of discrete symbols
Channel Capacity • doubling bandwidth doubles the data rate if m=8
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
Hartley-Shannon Law • Due to information theory developed by C. E. Shannon (1948) C: - max channel capacity in bits/second w: = channel bandwidth in Hz
Hartley-Shannon Law • Example W=3, 100 Hz for voice grade telco lines S/N = 30 d. B (typically) 30 d. B =
Hartley-Shannon Law
Hartley-Shannon Law • Represents theoretical maximum that can be achieved • They assume that we have AWGN on a channel
Hartley-Shannon Law C/W = efficiency of channel utilization bps/Hz Let R= bit rate of transmission 1 watt = 1 J / sec =enengy per bit in a signal
Hartley-Shannon Law S = signal power (watts)
Hartley-Shannon Law k=boltzman’s constant
Hartley-Shannon Law assuming R=W=bandwidth in Hz In Decibel Notation:
Hartley-Shannon Law S=signal power R= transmission rate and -10 logk=228. 6 So, bit rate error (BER) for digital data is a decreasing function of For a given if R increases , S must increase
Hartley-Shannon Law • Example For binary phase-shift keying =8. 4 d. B is needed for a bit error rate of let T= k = noise temperature = C, R=2400 bps &
Hartley-Shannon Law • Find S S=-161. 8 dbw
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
ADC’s • The SNR in (d. B) is therefore where about
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
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
Physical Layer – circuit identification – bit sequencing – notification of false conditions – deriving quality of service parameters – modulation and demodulation – signaling speed
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
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)
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
The Link Layer – notifies the network layer when errors are detected – controls data flow – selects optional qualityof service parameters
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
The Network Layer – keep track of the network node address while routing outgoing packets and recognizing packets that are intended for the local node
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
The Network Layer • in CCITT x. 25 protocol the network layer is called the packet layer.
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
The Network Layer – notifies the transport layer of errors – flow control – expedited service network – may provide sequenced delivery
The Network Layer • Two types of network layer protocols – connection oriented – connectionless
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
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
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
The Transport Layer • uses transport protocol data units (TPDU) • TPDU = packets + transport layer data • TCP = transmission control protocol
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
The Transport Layer – error detection – error recovery – connection establishment – data xfer – release of connections
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
The Transport Layer • The amount of work done is dependent on the protocol (VC or datagram) used at the network layer
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
Session Layer • Organizes data into SPDU (session protocol data units)
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
Session Layer • has phases of service – connection establishment – data xfer – connection release
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
Presentation Layer – data encoding, decoding and compacting – interpret character sets ( i. e. ASCII) – code conversion
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
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
Application Layer • has 5 groups – 1. System management protocols – 2. Application management protocols – 3. System protocols – 4. Industry specific protocols – 5. Enterprise protocols
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.
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
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. n 3 cv 1 44. 112. 0. 2 w 3 vc 44. 112. 0. 3 darth. wa 3 yoa
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