La Trobe University Network Design Exercise Dragan Stancic ELE5NDE - semester 1, 2017 Week 12 : Network Design 1Scope • Network Planing • Network Analysis • Network Topology • Network Traffic La Trobe University ELE5NDE - semester 1/2017 Network Design - p 2 . Outline week 12: Network Design • Network Elements, Traffic • Network Topology • Network Performance • Network Simulation and Optimization • Network Planing • Network Analysis La Trobe University ELE5NDE - semester 1/2017 Network Design - p 3 . Network Systems • telephone network • computer networks • internet La Trobe University ELE5NDE - semester 1/2017 Network Design - p 4 .Network Systems Communications • POTS : Plain Ordinary Telephone Service • PSTN : Public Switched Telephone Network Basic channel : 64kbit/s • TDM : Time Division Multiplexing time domain divided into time slots of fixed length (sub-channels) La Trobe University ELE5NDE - semester 1/2017 Network Design - p 5 . Network Systems Computer Networks • intranet • extranet • internetwork • internet La Trobe University ELE5NDE - semester 1/2017 Network Design - p 6 . Network Topology • Point-to-point • Bus • Star • Ring • Mesh • Tree • Hybrid • Daisy chain La Trobe University ELE5NDE - semester 1/2017 Network Design - p 7 .Backbone Network • Distributed backbone • Collapsed backbone • Parallel backbone • Serial backbone La Trobe University ELE5NDE - semester 1/2017 Network Design - p 8 . Network Elements • nodes • links • interfaces La Trobe University ELE5NDE - semester 1/2017 Network Design - p 9 . Network Elements - hub and switches • hub : acts as repeater • layer 2 switch : build routing table • layer 3 switch : may distribute traffic based on load or application content • layer 4 switch : stateful firewall • layer 7 switch : application-level transactions La Trobe University ELE5NDE - semester 1/2017 Network Design - p 10 .Network Elements - nodes • gateway : interconnects networks • router : forward packets between networks • firewall : controls network security • proxy : provides data caching and filtering • NAT : protects the private address range La Trobe University ELE5NDE - semester 1/2017 Network Design - p 11 . Network Elements - links • twisted pair • coax cable • optical fiber • wireless transmission • dry loop La Trobe University ELE5NDE - semester 1/2017 Network Design - p 12 . Network Protocols Protocol • set of formal rules and standards Protocol Stack • networking protocol suite La Trobe University ELE5NDE - semester 1/2017 Network Design - p 13 .Network Protocols SDU - Service Data Unit • data passed across OSI layers • data encapsulation to a lower layer PDU PDU - Protocol Data Unit • data passed between network entities over the same OSI layer • data encapsulation to a lower layer PDU La Trobe University ELE5NDE - semester 1/2017 Network Design - p 14 . OSI layer name function 7 application high-level API 6 presentation data translation between the service and application 5 session manage transmissions between nodes 4 transport data segment transmission 3 network network addressing, routing and traffic control 2 data link LLC - Logical Link Control: multiplexing MAC - Media Access Control: framing 1 physical raw bit streams transmission La Trobe University ELE5NDE - semester 1/2017 Network Design - p 15 . IP - Internet Protocol • select the next-hop host for outgoing packets • transmit packet through a link layer • pass incoming packets to a transport layer protocol • error detection and diagnostic IP Variants • IPv4, IPv6 - Internet Protocol version 4/6 • ICMP - Internet Control Message Protocol • IPsec - Internet Protocol Security La Trobe University ELE5NDE - semester 1/2017 Network Design - p 16 .IP - Internet Protocol IP Datagram • application layer : data • transport layer : UDP = UDP header + UDP data UDP data = application layer data • internet layer : IP = IP header + IP data IP data = UDP • link layer : frame = frame header + frame data + frame footer frame data = IP La Trobe University ELE5NDE - semester 1/2017 Network Design - p 17 . UDP - User Data Protocol • minimal message-oriented transport protocol • UDP header: four 16-bit fields source port number destination port number length checksum • checksum: 16-bit one’s complement of the one’s complement sum calculated over the header, data and pseudo IP header data may be zero-padded to make a multiple of 2 octets La Trobe University ELE5NDE - semester 1/2017 Network Design - p 18 . TCP - Transmission Control Protocol • reliable transport protocol • error checked • detects lost, duplicated and out-of order packets • re-arranges data • requests packet re-transmission La Trobe University ELE5NDE - semester 1/2017 Network Design - p 19 .TCP - Transmission Control Protocol oct 0 1 2 3 0 src port dest port 4 seq# 8 ack# 12 offset flags wind size 16 csum urg 20 options La Trobe University ELE5NDE - semester 1/2017 Network Design - p 20 . Network Traffic Random distribution • Normal Distribution : occurs in nature (Gaussian, "bell curve") • Uniform Distribution : constant probability density over a range • Binomial Distribution : successes in successive draws • Exponential distribution, Poisson distribution: inter-arrival of independent process events La Trobe University ELE5NDE - semester 1/2017 Network Design - p 21 . Queueing Theory • queue: waiting line • study of queueing systems • prediction of queue lengths and waiting times La Trobe University ELE5NDE - semester 1/2017 Network Design - p 22 .Queueing Theory Kendall’s Notation • basic queueing model using 3 factors: A/S/n – A : inter-arrival times distribution – S : service time distribution – n : number of servers at the node • extended queueing model using 6 factors: A/S/n/K/C/D – K : queue capacity (default: ∞) – C : calling population size (default: ∞) – D : queueing discipline (default: FIFO) La Trobe University ELE5NDE - semester 1/2017 Network Design - p 23 . Queueing Theory M/M/1 queue • inter-arrival times determined by a Poisson process arrivals occur at rate λ • service times have an exponential distribution the mean service rate is 1/µ • there is only one server, queueing discipline: FIFO • unlimited queue capacity, unlimited calling population size • system is stable only if λ < µ • the system utilization is ρ = λ/µ La Trobe University ELE5NDE - semester 1/2017 Network Design - p 24 . Queueing Theory M/D/1 queue • inter-arrival times determined by a Poisson process arrivals occur at rate λ • fixed service times (D) the service rate is µ = 1/D • there is only one server, queueing discipline: FIFO • the system utilization is ρ = λ/µ La Trobe University ELE5NDE - semester 1/2017 Network Design - p 25 .Queueing Theory Little’s law L = λW L: long-term average number of customers in a stable system λ : long-term average effective arrival rate W : average time a customer spends in the system La Trobe University ELE5NDE - semester 1/2017 Network Design - p 26 . Network Traffic Traffic Flow • sequence of packets from source to destination – unicast: from single source to single destination – multicast: from single source to multiple destinations – broadcast: from single source to any destination La Trobe University ELE5NDE - semester 1/2017 Network Design - p 27 . Network Traffic Traffic Flow • sequence of packets from source to destination – simplex: unidirectional from source to destination – duplex: bidirectional between source and destination La Trobe University ELE5NDE - semester 1/2017 Network Design - p 28 .Network Traffic Flow Control • rate of transmission management • control flow to avoid congestion • open-loop flow control simple control has no feedback from the destination • closed-loop flow control rely on information from the network about pending network congestion La Trobe University ELE5NDE - semester 1/2017 Network Design - p 29 . Network Topology • physical topology: – physical location of nodes – cabling • logical topology: – data path between nodes – can be dynamically reconfigured La Trobe University ELE5NDE - semester 1/2017 Network Design - p 30 . Backbone Network • interconnect separate parts of a network • closed structure may offer limited/controlled access to the public network may offer limited/controlled access to the sub-networks • limits the capacity of the whole network La Trobe University ELE5NDE - semester 1/2017 Network Design - p 31 .Backbone Network Backbone Network Types • Distributed backbone • Collapsed backbone • Parallel backbone • Serial backbone La Trobe University ELE5NDE - semester 1/2017 Network Design - p 32 . Network Performance • measures of service quality – bandwidth – throughput – error rates – latency – jitter La Trobe University ELE5NDE - semester 1/2017 Network Design - p 33 . Network Performance Congestion Control • congestive collapse: incoming traffic exceeds outgoing traffic capacity on a node • congestion control algorithms aim to prevent congestive collapse La Trobe University ELE5NDE - semester 1/2017 Network Design - p 34 .Network Performance Congestion Control Metrics • efficiency: average flow throughput in equilibrium • fairness: fair distribution of resources between flows • convergence speed: time passed until the equilibrium state is established • smoothness: magnitude of oscillations • responsiveness: number of steps to reach equilibrium La Trobe University ELE5NDE - semester 1/2017 Network Design - p 35 . QoS Network Supporting QoS • agree on a traffic contract • reserve capacity on network nodes Best-effort Delivery Network Service • no guaranteed QoS or data delivery • must rely on application or TCP to provide guaranteed data delivery La Trobe University ELE5NDE - semester 1/2017 Network Design - p 36 . Asynchronous Transfer Mode (ATM) • asynchronous time-division multiplexing • connection oriented • channel based transport: Virtual Paths (VP) and Virtual Channels (VC) • ATM cells: fixed size packets 5-byte header, 48-byte payload • multiple adaptation layers La Trobe University ELE5NDE - semester 1/2017 Network Design - p 37 .Asynchronous Transfer Mode (ATM) Service Categories • CBR: constant bit rate (PCR) • rt-VBR: real-time variable bit rate (PCR, SCR, MBS) • nrt-VBR: non-real-time variable bit rate (PCR, SCR, MBS, CLR) • UBR: unspecified bit rate (best effort service) • ABR: available bit rate (PCR, MCR) La Trobe University ELE5NDE - semester 1/2017 Network Design - p 38 . WLAN Elements • STA : Wireless Station basic addressable unit • WM : Wireless Medium physical medium which transfers PDUs between STAs on a WLAN implemented on radio frequency physical layers • AP : Access Point provides bridging services between WLAN and DS • DS : Distribution System backbone network connecting APs La Trobe University ELE5NDE - semester 1/2017 Network Design - p 39 . WLAN Elements • BSS : Basic Service Set set of stations that have synchronized using some primitives to form a membership • BSA : Basic Service Area area containing BSS members • IBSS : Independent Basic Service Set BSS that forms a self contained network without access to DS commonly known as AD-HOC Networks • ESS : Extended Service Set use of multiple APs to extend the service area beyond the limitations of the physical layer ESS operates in OSI layer 2 La Trobe University ELE5NDE - semester 1/2017 Network Design - p 40 .WLAN Configurations • Ad Hoc Networking peer-to-peer network no base, no AP La Trobe University ELE5NDE - semester 1/2017 Network Design - p 41 . Wireless Transmission Frequencies • 30 - 1000 MHz omni-directional broadcast radio/TV • 2 - 40 GHz highly directional point to point, microwave, satellite • 1011 - 1014 Hz infrared local La Trobe University ELE5NDE - semester 1/2017 Network Design - p 42 . Wireless Transmission Frequencies Industrial Scientific and Medical Bands - ISM • Unlicensed no need to obtain a license from the regulating authorities allowed ranges vary between states/countries • ISM use – microwave oven (2.45 GHz) • non-ISM use – Wireless LAN (2.4 - 2.4835 GHz) – Cordless Devices wireless microphones, cordless phones, mouse, keyboard, . . . La Trobe University ELE5NDE - semester 1/2017 Network Design - p 43 .Wireless Transmission Frequencies Spread Spectrum Types • FHSS : Frequency Hopping Spread Spectrum • DSSS : Direct Sequence Spread Spectrum • OFDM : Orthogonal Frequency Division Multiplexing La Trobe University ELE5NDE - semester 1/2017 Network Design - p 44 . Wireless Transmission Frequencies Direct Sequence Spread Spectrum DSSS • multiply the data stream by a high frequency pseudo-random sequence • occupy wide frequency spectrum • share channel among multiple users • immune to interference • difficult to intercept • same technology used in GPS satellite navigation systems La Trobe University ELE5NDE - semester 1/2017 Network Design - p 45 . Wireless Transmission Frequencies Frequency Hopping Spread Spectrum FHSS • switch carrier frequency among frequency channels • frequency hopping pattern predetermined and known by both transmitter and receiver • resistant to narrow-band interference • difficult to intercept • the transmitter use all channels over time the receiver locks a random channel and listens to data La Trobe University ELE5NDE - semester 1/2017 Network Design - p 46 .Wireless Transmission Frequencies Orthogonal Frequency Division Multiplexing OFDM • FDM : total bandwidth divided into non-overlapping sub-bands • OFDM : all carrier signals are orthogonal to each other cross-talk is eliminated, guard bands not required, simple • high spectral efficiency • not sensitive to interference and time synchronization errors • can be combined with multiple access using time, frequency or coding to separate users • high peak to average power ratio La Trobe University ELE5NDE - semester 1/2017 Network Design - p 47 . Physical Layer, Wireless Networks Free space path loss calculation: L p = (4πD λ )2 La Trobe University ELE5NDE - semester 1/2017 Network Design - p 48 . Physical Layer, Wired Networks Wire Types • Twisted Pair • Coaxial Cable La Trobe University ELE5NDE - semester 1/2017 Network Design - p 49 .Physical Layer, Wired Networks • Twisted Pair – Resistance R = ρ L S – Capacitance C0 = π arcosh( d rc ) • Coaxial Cable – Resistance R0 = ρ πrc – Capacitance C0 = 2π ln(rout rin ) La Trobe University ELE5NDE - semester 1/2017 Network Design - p 50 . Physical Layer, Wired Networks Optical Fiber vs Wire • increased capacity up to hundreds of Gbit/s • smaller size • lower attenuation • electromagnetic isolation La Trobe University ELE5NDE - semester 1/2017 Network Design - p 51 . Network Performance Metrics TL = TxO + ToF + TxT + RxO where: • TL : total latency • TxO : sender overhead • ToF : time of flight • TxT : transmission time • RxO : receiver overhead La Trobe University ELE5NDE - semester 1/2017 Network Design - p 52 .Network Performance Metrics Physical Layer Measurements • Time Domain Reflectometer (TDR) • Vector Network Analyzer (VNA) • detect impedance mismatch • detect cabling faults La Trobe University ELE5NDE - semester 1/2017 Network Design - p 53 . Network Performance Metrics Time Domain Reflectometer (TDR) • measurements in the time domain • pulse wave generators access all ports • measure impedances La Trobe University ELE5NDE - semester 1/2017 Network Design - p 54 . Network Performance Metrics Vector Network Analyzer (VNA) • measurements in the frequency domain • sine wave generators access all ports • measure delay and loss La Trobe University ELE5NDE - semester 1/2017 Network Design - p 55 .Network Simulation The simulation process • imitation of the operation of a real network system over time • uses abstract models to describe unit behaviour • uses unit inter-connections to describe unit inter-actions • use mathematical models to generate data stimulus or uses captured data from real systems • evaluates system behaviour for specific scenarios La Trobe University ELE5NDE - semester 1/2017 Network Design - p 56 . Network Simulation Simulation Accuracy • depends on units and interaction models accuracy • depends on data stimulus accuracy • depends on the simulation engine La Trobe University ELE5NDE - semester 1/2017 Network Design - p 57 . Network Simulation What is simulated • nodes settings • links characteristics • network topology • communications protocols • data transfer • applications and server services • interference, noise, background traffic La Trobe University ELE5NDE - semester 1/2017 Network Design - p 58 .Network Simulation What is analyzed - simulation results • data throughput • network availability • network congestion • fault tolerance • error rates La Trobe University ELE5NDE - semester 1/2017 Network Design - p 59 . Network Simulation Why simulate • to detect issues early, before implementation • to identify bottlenecks • to estimate costs • to compare alternative designs and select the optimal system La Trobe University ELE5NDE - semester 1/2017 Network Design - p 60 . Network Simulation Simulation vs Emulation • Emulation uses real hardware to interact with real systems • Simulation is software executed on a computer • Simulation time is different from real time La Trobe University ELE5NDE - semester 1/2017 Network Design - p 61 .Network Simulation Model development process 1. requirements analysis 2. requirements specification 3. model design 4. model testing and verification 5. model validation against known data La Trobe University ELE5NDE - semester 1/2017 Network Design - p 62 . Network Optimization • network auditing and benchmarking • bottleneck identification • modeling and network planning • analysis and optimization La Trobe University ELE5NDE - semester 1/2017 Network Design - p 63 . Network Optimization Optimization Process Steps • collect data • identify elements and relations • analyse system operation • verify assumptions • identify metrics, set goals • modify parameters and re-iterate La Trobe University ELE5NDE - semester 1/2017 Network Design - p 64 .Network Performance • measure of service quality as seen by the network users • grade of service (circuit-switched networks) • quality of service (ATM networks) La Trobe University ELE5NDE - semester 1/2017 Network Design - p 65 . Network Planning • Topological design locate network component placement minimize the cost of switching and transmission • Network-synthesis select network components to meet traffic requirements • Network realization create a physical implementation plan La Trobe University ELE5NDE - semester 1/2017 Network Design - p 66 . Network Analysis Purpose • Locate faults • Locate bottlenecks • Identify vulnerabilities • Security auditing • Network Compliance Test La Trobe University ELE5NDE - semester 1/2017 Network Design - p 67 .Network Analysis Port Mirroring • provide a monitoring port on a switch • send a copy of traffic from selected ports to a monitoring port La Trobe University ELE5NDE - semester 1/2017 Network Design - p 68 . Network Security • Intrusion Detection • Intrusion Prevention La Trobe University ELE5NDE - semester 1/2017 Network Design - p 69 . Network Service • application running at the network application layer • client-server or peer-to-peer architecture • push and pull services La Trobe University ELE5NDE - semester 1/2017 Network Design - p 70 .Virtualisation • creating a simulated version • creating one or more virtual machines on a computer • mimic real-world systems use in testing • separate logical and physical structures La Trobe University ELE5NDE - semester 1/2017 Network Design - p 71 . Access Network Types • Symmetric same bandwidth upstream and downstream • Asymmetric high downstream bandwidth, low upstream bandwidth La Trobe University ELE5NDE - semester 1/2017 Network Design - p 72 .