Intr to Communication Networks
Intr to Communication Networks EECS 563
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Date Created: 09/07/15
Communications Network Simulation 8 Victor S Frost Dan F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas 23351rving Hill Dr Lawrence Kansas 66045 Phone 785 8644833 FAX785 8647789 email frosteecs kuedu httpWwwittc kuedu With modi cation from Dr David Petr Simulation Outline I Define network simulation I Discuss attributes and application of simulation I Present implementation of simulation systems I Discuss analysis of simulation results I Discuss selection of simulation tools I Provide an overview of Extend the simulation tool using here Simulation A Definition of Communication Network Simulation Communication network simulation involves generating yseudorundom seguences of message lengths and interarrival times or other input processes eg time varying link quality then using these sequences to exercise an algorithmic description of the network oyerution Simulation Attributes of Simulation I Simulation Is a Very Flexible Evaluation Tool gt General Network Characteristics Sources Topology Protocols Etc gt Minute Detail Simulation Models Can Be Expensive to Construct gt Human Effort Simulation Models Can Be Expensive to Run gt Computer Effort Statistical Analysis of the Results Can Be Difficult gt Requires Careful Interpretation Difficult to Gain Insight Into System Behavior gt Simulate Only a Set of Speci c Scenarios Simulation When to Use Simulation I Whenever Mathematical Analysis Is Difficult or Impossible gt For Studying Transient Behavior of Networks gt For Systems With Adaptive Routing gt For Systems With Adaptive Flow Control gt For Systems With Blocking Finite Buffers gt For Systems With General Message Interarrival Statistics Simulation When to Use Simulation I For Validating Analytic Models and Approximations gt How Accurate Is the Model gt Do Approximations Distort the Results I For Experimentation Without Disturbing an Operational System gt Test Possible Modifications and Adjustments Simulation Modeling Elements for Communication Networks I Traffic and Input Processes gt Message Arrival Process 7 Often Interarrival Times gt Message Lengths gt Other Message Attributes 7 Service Class 7 Error models I Algorithmic Descriptions of Network Processing gt Protocols gt Links and Queues gt Routing Simulation Sample Realization of an Input Process Table Message number 1 2 3 4 5 6 7 8 9 10 11 12 lnterarrival time 2 1 3 1 l 4 2 5 1 4 2 between i1 and i message seconds Length of it1 message 1 3 6 2 1 1 4 2 5 1 1 3 seconds Simulation Sample Realization of an Input Process Graph Measured Video Traffic 30 Arrival 95 Events amp 7 129 Lengths g was was E 2 i275 Simulatt n Discrete Event Simulation Terminology I Entities gt Objects Upon Which Action Is Performed gt In Network Simulation Entities Are Messages Packets I Attributes gt Characteristics Which Describe Entities eg Message Length I Events gt Occurrences That Trigger Activities eg Message Arrival Departure Simulatt n Discrete Event Simulation Terminology I Activities gt Operations That Change the State of the Network gt Example Increment Number of Messages WaitJng in a Buffer I Files gt Groupings of Entities Which Share a Common 39 ute gt Example All Messages Waiting in Buffer Smuhmn 11 Discrete Event Simulation Dynamics Time Smuhmn 12 Time Step Approach to Network Simulation I Approaches to Discrete Event Simulation gt Time Step Approach Fixed Increment Time Advance gt EventScheduling Approach I Fixed Increment Time Advance gt Choice of Increment Important gt Too Large Multiple Events Happen In Single Step gt Too Small Wasted Processing Time gt Update System States at End of Each Fixed Time Interval 13 Simulahan Time Step History of Simple gatistical Multiplexer System s 59 0 a o i a a 3 cg 1 0 3 lt3 4 a CD lt22 lt22 2o 30 E 8 g m n V is 71 6 999 QGQ 690 egg 99 ee 7 213 7 ea 9 a 7amp3 Simulahan Number in System Nt vs Time Number in system 47553333 4 166667 3775 3 333333 2916657 7 2 083333 7 1666567 Ej 125 0 6333333 1 3 U 4166867 0 0 3146124 06292249 09438373 1 25845 1573052 1 387675 Time 15 Simulation Event Scheduling Approach to Network Simulation I Variable Time Advance gt Advance Time To Next Occurring Event I Update System State Only When Events Occur gt For Example Arrivals or Departures 16 Simulation Event Scheduling Approach to Network Simulation I Event Calendar gt Events Instantaneous Occurrences That Change the State of the System gt An Event is Described by The Time the Event is to Occur The Activity to Take Place at the Event Tilne gt The Event Calendar is a Time Ordered List of Events Simulation Event Scheduling Approach Simplified Flow Control gt Use Event List An Executive to determine next 0139 Majnljne event to process Controls the Selection Of Next Advance simulation Event clock to event time Update system state using event routines Update event list using event routines Simulation Event Scheduling for Simple Statistical Multiplexer Arrival 19 simman Event Scheduling for Simple Statistical Multiplexer Depanure End of Transmissio 1 Change Read 8 remav status of ham we transmissior ules faculty m idle Snapshot of Simple Statistical Multiplexer Simulation Ms ya a 31 numbei alu oi Numbev Tiansuussmn m I 1 acme Guile System Clock 2 Number at Total Delay 0 Packuls Lumplulud processed messages Area Under Nu Simulation Relative Merits of Time Step and Event Scheduling Approach Advantages Disadvantages Time Step Efficient for system with very frequently occurring events Efficient for regularly spaced even 5 Must process at each time step Error induced by fixed finite time increment Must establish rules to order events that occur in same time increment Event Scheduling Only process at event times No time increment to select Flexible Significant programming e fort required Simulation Verification and Validation of Simulation Models I Model gt Mathematical Algorithmic Description of Behaviour of Real Thing I Verification gt Determining Whether the Simulation Model Performs As Intended gt In Programing Terminology Debugging gt Example Is VIW1 Model Producing Exponential Message Lengths I Validation gt Determining Whether the Simulation Model Itself Is an Accurate Representation of the Communication Network Under Study the Real Thing gt Example Is the Assumption of Exponential Message Lengths Accurate Simulation Verification Methods I Modular Development and Verification gt Break Large System Into Smaller Components gt Verify Component by Component I Structured WalkThrough gt Step by Step Analysis of Behavior for Simple Case Simulation Verification Methods I Event Trace gt Detailed Analysis of Model Behavior gt Compare to Walk Through Analysis I Model Simplification and Comparison to Analytic Results I Graphical Display of Network Status As the Model Progresses gt To See What Is Happening As It Happens Simulation Some Comments on Validation I Silnulation Models Are Always Approximations I A Simulation Model Developed for One Application May Not Be Valid for Others Model Development and Validation Should Be Done Silnultaneously Specific Modeling Assumptions Should Be Tested Sensitivity Analysis Should Be Performed Attempt to Establish That the Model Results Resemble the Expected Performance of the Actual System Generally Validation Is More Difficult Than Verification Simulation Analysis of Results Statistical Considerations I Starting Rules gt Overcoming Initial Transients gt An Initial Transient Period Is Present Which Can Bias the Results gt Achieving Steady State Use a Runin Period I Determine Tb Such That the LongRun Distribution Adequately Describes the System fort gt Tb Use a Typical Starting Condition State to Initialize the Model I Quality of Performance Estimates gt Variance of Estimated Performance Measures Simulation Quality of Performance Estimates I Performance Estimates Should Be Unbiased I Performance Estimates Should Have Acceptable Variance I Confidence Intervals Are the Usual Approach for Assessing the Accuracy of the Estimators I The Desired Confidence Interval Width Determines the Length of the Simulation Run I Observations Tend to Be Correlated gt Cannot Directly Apply Standard Statistical Approaches Based on iid Independent ldentically Distributed Observations Simulation Dealing with Lack of Independence I Simple Replication Multiple Simulation Runs gt Assume Results for Each Replication Are Independent gt Inefficient Because of Multiple Startup Periods I Batching Divide Single Simulation Run Into EqualTime Batches gt Assume Results From Each Batch Are Independent gt Batches Can Be Correlated Unless Dead Periods Between Batches Are Employed 29 Simulation Simple Replication Approach amwbm Nt FHJ UIH IIUULl Replication l 0 PH Tb Mt b 5 4 3 2 39I o o Em ni lw H L jl39l l IJ Ln I l M lb 30 Simulation divulth Batching Approach Nt Nt S 4 3 2 n L d Batch 1 D gt lquot39 Balcl1 M l T T 2T MT b 1 1 1 31 simulation Evolution of Network Simulation Tools quotZerothquot Generation 7 General Purpose Languages gt Fortran C c pascal Basic quotFirstquot Generation 7 General Purpose Queueing Systern Sirnulations gt GPSS SLAM SIMSCRIPT quotSecondquot Generation 7 Application Specific Cornputer Systems and WiderArea Communication Networks gt RESQ PAWS Ns721attp www 15 edunsnarnns quotThirdquot Generation 7 Integration of Second Generation Languages With a Graphicerriented Analysis and Modeling Envir gt Extend wwwm1 g gt SEEWorkbench Scienti c and Englneenng Software Inc Austin TX gt OI N39ETI1113 Inc Washington DC onm out a inethatinacom 32 simulation Relative Merits of General Purpose Languages model may the language more efficient ability to reuse models are difficult Sunulnuon Relative Merits of Special 39 Advankages Provide bullein simulation services in rvduuv prugrarnming offurt urpose Languages Disadvantages Must adhere to n particular quotworld Viewquot ei ilie language Provide errorrchccking techniques superior to those prl ided in general purpose languages Provide a b Ief dir cf le1 rcsslng the contopk in sing in a klnlulatinn Stu y gt3 I I vliik1liill7 to cons C wnv smlulaliun rnutine Contain set if subruulines lul COH H HDII random nui nhvrs V l mel gtlernutinelt requier as a part of Availability and wppert C Nt Increased compuxer running tilne iqu required to learn llie language and modeling paradigm Faullmte enlleeiiun and ellsplay ur data produced F1d ltd lL quot10d 039 reuse Sunulnuon Relative Merits of ComputerAided Analysis and Design Environments Advantages Disadvantages Provide a complete integrated performance analysis environment Tailored to a specific modeling paradigm Graphically based May be tied to a specific hardware platform Typically integrate language database prior knowledge and statistical analysis packages Increased execution time Support management of models and input output data Cost Facilitate model reuse and group model development Simulation Criteria for Selecting a Network Simulation Tool Availability Cost Usage Documentation Ease of Learning Computation Efficiency Flexibility Portability User Interface Extendibility Memory Requirements Simulation Guidelines to Network Modeling and Simulation I Things to Know gt Know the Customer gt Know the Network gt Know the Important Performance Metrics I Things to Do gt Establish a Credible Model gt Expect the Model to Evolve gt Apply Good Software Management Techniques 37 Simulation Conclusions I Simulation Can Be an Important Tool for Communication Network Design and Analysis I Care and Thought Must Go Into Construction of Communication Network Models I Care and Thought Must Go Into Interpretation of Model Output 38 Simulation Extend Overview I Allows Graphical Description of Networks gt Sources Links Nodes Etc I Data Flow Block Diagrams I Hierarchical Structure to Control Complexity I Be sure and create libraries when creating complex models Simulation 39 Extend Simple Statistical Multiplexer Model Simulation Clock Executive FIFO Queue Exit Required Simulation 40 Extend Better Statistical Multiplexer Model Packetsuume Meaasge Length in bll m Arrival Rate PacketsSE Simulation Message Length bits Extend Better Statistical Multiplexer Model Gettirne in System Meaasge Length in bits 39 ear QueueiLength II M III m I II Simulation Extend Data Structures R h Orulte mm A ermnua mum Extend Block Diagram Hierarch mm m mum 44 Extend Packet Switching System Packet Switching System Packet Source 46 Simulation Packet Switching System Packet Switching System Output Port Link Capacity bs 48 Simulation Simulation Case Study Simulation ofATM WAN s I Determine the level of model fidelity required to accurately predict ATM WAN performance I Determine the feasibility of measurement based validation of TCP IP over ATM WAN simulation models I Identify factors in uencing TCPIP over ATM WAN performance 49 Simulation Simulation Case Study Simulation ATM WAN s Simulation Case Study Simulation ofATM WAN 5 Network an mlmrinn um I um m A mum mm x ma ISS IM nu quotmum um mm AM Comparison of Experimental and ATM and Frame Relay 14 Vlctor S Fro st an F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas Lawrence Kansas 66045 Phone 785 8644833 FAX785 8647789 email frosteecskuedu httpwwwittckuedu Section 7 6 and Chapter 9 ATM ATM I ATM is a high speed low delay switching technology using short fixed size packets called cells I It combines the benefits of both circuit switching low and constant delayL guaranteed capacity and packet switching flexibili efficienc for burs traffic by using the cell switching technique to support the transmission of multimedia traffic such as voice Video image and data ATM Key Attributes I Fixed length frames I Virtual circuit operation I 208 I Support dynamic bandwidth allocation I Same technology for ATM LANs and WANs Billing ATM cell format 5 octets 48 octets Header Information lt 53 octets ATM I Bandwidth on Demand I Payload I VC1 I Payload I VC1 I Payload I VC2 I I Scalable Networking gt Add capacity by adding ATM switches Switch Switch ATM CutThrough Switching Store and Forward Packet Switching ATM CutThrough Switching ATM CutThrough Switching CutThrough Switching Segmenting large PDU s into ATM cells and using cell switching provides cutthrough like performance Multiplexing at the cell level can guarantee Q08 requirements Why ATM I Suitable of multiple types of traffic each with different QoS requirements High speed low delay networks for real tirne computing and command and control environments Consolidate gt networks and minimize the variety of network elements gt network management systems High speed network to interconnect LANs over wide area High speed high capacity LANs and or backbone networ s HOW Does ATM Work 1 of 3 I All traffic whether voice video image or data is divided into 53octet cells and routed in sequence across the ATM network I Routing information is carried in the header of each cell I Routing decisions and switching are performed by hardware in the ATM switches How Does ATM Work 2 of 3 I ATM is connectionoriented an endtoend connection must be established and routing tables set up prior to cell transmission l Cells are reassembled into voice Video image or data at the destination How Does ATM Work3 of 3 Voice Video Data Voice Video Data BISDN BISDN Services Services gt Segmentation Reassembly ATM Protocol Reference Model Under Control User controlled 0f HEtWOFk PFOVideE Ondemand Managxment Plane low fast Control Plane User Plane Higher Layers I Higher Layers ATM Adaptation Layer ATM Layer Physical Layer Information flow very fast ATM 1 3 ATM Protocol Reference Model A Class B Signaling Constant Bit amp Control Rate Circuit Emulation AAL1 ATM Layer Service independent Cell Formatting Physical Layer ATM Information Transport Protocol User Network User Error Recovery amp Flow Control EndoEnd EdgeoEdge Functions of the ATM Layers Higher layers High layerfunctions ATM 53333quot Convergence Adaptation Layer Segmentation and Reassembly Segmentation and reassembly Sublayer neral now control Ge Cell Header generationextraction ATM Layer Cell VPINCI translation Cell multiplexing Cell rate decoupling Transmission HEC sequence generationverification Convergence Cell delineation Sublayer Transmission rrame adaptation Transmissionrramegenerationreco my Physical Layer Physical Medium ing Sublayer Physical medium ATM Layer Cell Header Structure 8 7 6 5 4 3 2 1 I I I I I I I Generic Flow Control GFC I Virtual Path Identifier VPI VPI I Virtual Channel Identi er VCI VCI VCI I Payload Type PT CLP Header Error Control HEC At the NNI the GFC eld becomes part of the VPI field CLP Cell Loss Priority ATM Layer I Virtual Paths Virtural Circuits Transmission Path VP ampVC s PCllLJJ PC Pmmml Dallnec on sdcnu u um 19 VP ampVC s SWItches VPsw nnh VCI VCJ vczquotquot V VCA VC VC5 VC VPZ VPZ vc vcm VP VG VClvy1 V VC g n mm m VFZ VG VG VCI vct V VCl VCI V vcz vc2quotquot ATM Layer T Indicator Interpretation OAM Operations Adminstration and Mainteance SDU Service Data Unit SDUtype 01 gt End of AAL 5 PDU Forward Explicit Congestion Notification FECN I Switches de ne a congested state I Cells encountering switches in a congested state set congestion experienced bit I Destination informs the source about congestion I Sources reacts to congestion Layer ATM Switch Architecture Input Controllers Input Ports Control Processor Maybe external witch Vivi processor Output Controllers ATM 23 AAL Serv1ces l Service Class A I Class B Class C Class D Timing sgifrtcleezrri39d Related Not Related Destination Bit Rate Constant Variable Connection 5 Mode quotquot quot quot meme Connectionless Circuit 5 f Emulation Low bit rate onnec Ion Exa39gg39es networks Oriented Connectionless Services Constant Bit Data Data Rate Video Evolving Transfer Transfer u l0 AAL AAL 34 AAL 34 TYPE AAL1 AAL 2 AAL 5 AAL 5 ATM Adaptation Layer AALl I Supports constant bit rate data with specific requirements for delay delay jitter and timing eg PCM voice CBR video and emulation of T carrier circuits DS l DS 3 I Receives constant bit rate stream with a well defined clock from source and delivers the same to the destination I Provides for timing recovery synchronization and indication of lost information ATM Adaptation Layer AALl I Consists of 1 octet header PCI and 47 octets of payload I Sequence Number SN A 1bit Convergence Sublayer Indication and 3bit sequence count to detect deletion or incorrect insertion of cells ATM Adaptation Layer AALl I Sequence Number Protection SNP 3bit CRC with even parity for detecting and correcting SN error 4 bits 4 bits 47 octets SN SNP I SARPDU Payload ATM ATM Adaptation Layer AAL2 I New evolving standards will enable multiplexing within a ATM VC I ATM efficiently carries heterogeneous traffic in high speed networks ATM Adaptation Layer AAL2 Applying ATM in lowbit rate Mobile networks I Problem gt Communications between base station controller BSC and mobile switching center MSC gt Low bit rate links eg 2 Mb s gt Voice applications gt delay constraint gt Wait to fill ATM cell induces undesirable packetization delay 29 ATM Adaptation Layer AAL2 Applying ATM in lowbit rate Mobile networks I Solution gt Layered cell structure gt Makes better use of bandwidth gt Improves control over packetization delay I Layered cell structure permits the multiplexing of multiple channels on one ATM VC 30 ATM Adaptation Layer AAL2 Properties of AAL Channels l Channels have fixed length PDU I 8 bit channel identifier CID I 3 byte packet header PH per channel I 1 byte start field SF per Channel ATM ATM Adaptation Layer AAL2 Applying ATM in lowbit rate Mobile networks lt 53ATM gt T l Cell Hair l I III N ll Hall l3l Left over form previous cell D 1 Byte Start Field STF D Data D 3 Byte PaCket Header PH Channel continued between cells ATM ATM 32 ATM Adaptation Layer AAL2 Features I Channel can ow across ATM Cell boundaries STF points to beginning of first channel in the ATM Cell I Each channel has a fixed maximum length negotiated at call set up I A fixed timer TimerCU is started per channel I Upon timer interrupt the cell is padded out and transmitted I The timer guarantees predictable delay ATM 33 ATM Adaptation Layer AAL2 PH and STF Formats PH STF Sbits 6bits 5bits 5bits 6bits 1bit 1bit CID L1UU1HEC IOSFISNP OSF Offset field CID Channel identifier SN Sequence number Ll Length indicator UUl User to user information P Determines cell loss Parity check Reserved for use by upper layers Detects erron is STF HEC Header error control ATM ATM Adaptation Layer AAL2 Common Part Sublayer on Transmit I Constructs the 3 byte header I Adds user data and header into ATM cell I Manages AALZ timer I Updates start field I Manages buffering data for transmission gt Waiting for more user data gt Padding and transmitting if tuner fires ATM ATM Adaptation Layer AAL2 Common Part Sublayer on Receive I Appends offset bytes from previous cell I Processes PH gt Discards if HEC error gt Discards if invalid CIR or L1 I Note tracking user data across multiple cells is a complex function ATM 3 6 ATM Adaptation Layer AALS I AALS is a siInple and efficient AAL SEAL to perform a subset of the functions of AAL 4 I AALS is designed to support only message mode nonassured operation I The PTI field of the cell header identifies the beginning or end of the CPCS PDU gt PTT 0X1 EndofMessage EOM gt PTT 0X0 BeginningofMessage BUM or Continuation ofMessage COM 047 1 1 2 4 CPCSPDU Payload PAD Ic s CPI ILength ICRC32l ATM Bearer ClassesService Categories the service you buy Guaranteed Classes I CBR Constant Bit Rate 39 rt39VBR Real Tune Variable Bit Rate 39 nrt39VBR Non Real Tune Variable Bit Rate 39 AER Available Bit Rate 39 GFR Guaranteed Frame Rate Best Effort Classes I UBR Unspecified Bit Rate ATM 38 Some ATM Traffic Descriptors I Peak Cell Rate PCR I Sustainable Cell Rate SCR I Maximum Burst Size MBS I Minimum Cell Rate MCR I Cell Delay Variation Tolerance CDVT ATM ATM QoS Descriptors I PeaktoPeak cell delay variation I Maximum cell transfer delay I Cell Loss ratio I ATM 208 Contract gt Traffic gt Shaping gt Services gt 208 gt Compliance gt Policing gt Generic Cell Rate Algorithm GCRA like a leaky bucket algorithm is used for shaping and policing ATM Bearer Class Attributes Attribute ATM Bearer Classes Cell Loss Ratio and Jitter Spec Peak Rate Spec Sustainable Rate NA Minimum Rate NA Feedback ATM Bearer Class Guarantees ATM Layer Bearer Classes CBR rt VBR nrtVBR ABR UBR Network Network Cell Loss Ratlo um am Guaranteed Objectives Obiemves Network Network Network Obiectives Obiectives Objectives Attribute Delay and Jitter um am Peak Rate Gum None None None None Sustainable Rate None Guaranteed None None Minimum Rate None None None None ATM Mapping Applications to Service Classes ATM Applications Delay Reliability etc ATM Signaling I Used for dynamically establishing maintaining and clearing ATM connections at the User Network Interface I Based on ITU T CCITT Q2931 protocol I A specific VPCIVCI value VPCI 0 VCI 5 is used for the connection call control signaling out of band signaling I Signaling AAL SAAL is AALS SAAL provides reliable delivery ATM Frame Relay I Key enablers gt High Speeds gt Low Error Rates gt Predates ATM gt Provides access to ATM backbone services gt ISDN Standards Development ATM Frame Relay Provides Data Networking ServiceInterfaceProtocol I Frame Delimiting Alignment Transparency I Variable Length Frames I Frame Multiplexing via Link Level Connection Address IVirtual circuit oriented ATM Frame Relay Provides Data Networking SeniceInterfaceProtocol I Detection of Transmission Format and Operational Errors I Transparent IneOrder Transport of Frames I No Frame Acknowledgment Within the Network I Congestion Control Functions Private Line Service Network Coud Service Frame Relax Packet Format DLCI USER Data ch Frame Relay Packet Format I DLCI Data link connection ID I C R Control Response I EA Extended Address I FC Forward Congestion Indicator I BC Backward Congestion Indicator I DE Discard Eligibility Indicator I FCS Frame Check Sequence ATM Frame Relay Layers 1 Higher Higher Layers Layers 37 37 Layer 2 Upper 777777777 W Layer 2 Upper Layer 2 Core I Layer 2 Core I Layer 2 Core Layer 1 Layer 1 Layer 1 l l User Frame Relay User Equipment Servrce Equipment Frame Relay Layers I L2 Core Responsibilities gt Routing DLCI Translations gt Error Checking Discard Errored Frames gt Congestion Management Later in Talk I L2 Core Not Responsible For gt Error Correction e g Retransmission gt Flow Control e g Windows Signaling in Frame Relay Networks I Initial Networks Need No Signaling gt Small Number of Logical Connections per Endpoint gt Use Permanent Virtual Circuits PVCs gt Manage PVCs with Local Management Interface LMI On DLCI1023 I Common Channel Signaling For Switched Virtual Circuits SVCs gt DLCI0 on Each Physical Link gt Level 3 Network Control Via Q931 Extended gt Common Signaling Protocol for Integrated Services Frame Relay Switching Traf c and Congestion Control in Frame ela Negotiated Txa ic Paxametexs Pex DLCI Committed Infoma on Rate in bs ClR Committed Ems Size in bits 13c Excess BuxstSize in bits Be Measmementlutervalin sec T 13c c11lt Traffic and Congestion Control in Frame Relay Access Traffic Control I Accept and quotGuaranteequot Delivery of Up To Bc in Any T CIR I High Loss Priority DE0 I Accept Up To Bc Be More In Any T I Low Loss Priority Network May Discard If Congested DE1 I Excess Over Bc Be in T Discarded At Access Point in Frame Relay msx nsmwm minim m an mesemzn n mummy x mm 58 um may p m n W Traffic and Congestion Control in Frame Relay I Users can prioritize and shape at their EDGE to keep with CIR pick DLCl s set DE s I Some edge routers can rate limit in the presence of BECN indications I ACCESS Network can police set DE s I CORE will discard in the presence of congestion first DE s then others as necessary 59 Traffic and Congestion Control in Frame Relay I Network Congestion Functions I Notify Users gtFECN BECN CLLM LMI I Discard Frames With DE1 I Discard Frames With DE0 I Clear Connections etc 60 Traffic and Congestion Control in Frame Relay I Congestion Indications To User I Implicit gt Frame Discard Via Upper Protocol Levels I Explicit Congestion Notification From Network gt Forward Toward Destination FECN gt Backward Toward Source BECN CLLM LMI gt FECN functionality is used in ATM Traffic and Congestion Control in Frame Relay User Reaction To Congestion Indications I Optional User Can Ignore I Rate Based Control gt Reduce Rate Upon Indication Implicit Explicit gt Gradually Increase When Cleared gt Implement With Buffered quotShapingquot or quotMeteringquot Function I Window Size Control gt Frame Losses Imply Insufficient Buffers gt Buffer Requirements Depend On VC Window Sizes gt Throughput Rate Also Affected By Window Size Traffic and Congestion Control in Frame Relay User Reaction To Congestion Indications lSo Reduce Window Size During Congestion lSlowly Increase When Congestion Passes lExplicit Notification or N Correct Receptions Traffic and Congestion Control in Frame Relay User Reaction To Congestion Indications Example lOver Time interval 2time to Tx W Frames I Measure gt frames with FECN set Nset gt Frames with FECN cleared N cleared Traffic and Congestion Control in Frame Relay User Reaction To Congestion Indications Example I If Nset Ndeared gt 0 then reduce window to max1 7 SW I If Nset Ndeared lt 0 then increase window to Inin W1 W max The Evolution of the Communications Network 3 V1ctor S Fro st Dan F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas 2335 Irving Hill Dr Lawrence Kansas 66045 Phone 785 8644833 FAX785 8647789 email frosteecskuedu httpwwwittckuedu Evolution 1 The Evolution of the Communications Network I What makes communication systems work I How the network evolved I How network provided more services for less cost I Predict where technology is going and the impact of future services Evolution 2 Elements of Communications Time Of Iwan Talk to Joe Central Office Page 220 Evolution 3 Elements of Communications Time Central Office Ihave 1096 permission 0a Evolution 4 page 220 Elements of Communications Time NumbEr I need to Central give the net Office the address Page 220 Evolution 5 Elements of Communications Time Check path to Ice Check if Busy Central Office ng39back Ioe Answers Evolution 6 page 220 Elements of Communications Time Central Office We Answers v1 I Talk to jampe0 page 220 Evolution 7 Elements of Communications Time Central Office 0 8118 ik a 1 up Ihang uP Joe Hangs up 1 Evolution 8 page 220 Voice over IP VoIP I One signaling protocol for VoIP is SIP I Session Initiation Protocol Caller listen on port 5060 ob19364210 89 S INVITE b g C INIP4167180112 24 5 maud1038060RTPAVP 0 200 Ok C IN IP41 193 64210 89 Por138060 Talk Talk me ComputerNetWorklng Kumse and 120534Yd edition Addison Wesley 2004 listen on port 5060 Port 48753 Evolution 9 Elements of a I Transmission l Switching I Signaling Communications System Evolution 10 Transmission W mmmm m E if Coppeer TiJne Evolution 11 Standard rates for PSTN Sample Rate 80005 8bitssample lJTHOUGHquotml gallon lmlao mo un lInna III II II II Illlllll II I ll 7 64 Kbs 39 Evolution 12 Section 3 1 Tune visim Mxl plexing A A a TDM E c E 2 C 7 D 3 D E Tum lesmn Multiplexed 51ng Circuit Switching FDMA and TDMA Example FDMA Frequency Division Multiple Access 4 users DEED equency me TDMA Time Division Time Multiple Access Frame 510 t frequency time Modi ed from cmmmmmmimg ATongviAWmachFentnmigthelntmet Evoluuon 14 m Ni V i v lyzooz Switching I Manual I Stepbyistep I Crossbar with stored program control I Digital Switching I Packet Switching I Optical Switching Emmy 15 Stored Program Control System mm m W7 E In mmwu o 7 mammm Anvvwlrm ommmm Crossbar Switch Switching cunt Digital Switching Packet Switching I Existing switching methods allow connections at discrete information transfer rates eg 64 Kbs or 1544 Mbs I Customers quotwill demandquot dynamic allocation of bandwidth I Packet switching will provide dynamic allocation of bandwidth I One infrastructure for voice data Video I VolP and Video over IP Evolution 20 Packet Switching I Internet Protocol IP gt Longer variable length packets gt Deployed to the desktop I Asynchronous Transfer Mode ATM gt Short fixed length packets called cells gt Deployed in Backbone Networks I Packet switching leads to the potential integration of all services on one infrastructure Evolution 21 Integration 9Architecture of the Global Information Infrastructure Healtheare Government Services Applications Business Environmental Monitoring Education LifeLong Learning 39 Voice Data Video Multimedia age Electronic Transactions Resource Discovery 39 High Speed Networks Switching Systems Advanced Signaling Systems Services Bitways Fiber Transmission Systems wireless Networks Cable Systems Satellite Systems Twiste Pair CopperLoopsBroadcastCe ar 22 What s the Internet nuts and bolts View how do packet ow over the internet l millions of connected rower computing devices hosts quotYorksmhon endsystems server Qmobile gt PCs Workstations servers r gt PDAs phones toasters running network apps I communication links gt ber copper radio satellite gt transmission rate bits sec Some times called bandwidth I routers forward packets chunks of data Indedman v Architecture of the Internet mgmar rs 39 uncknoue e g Sprrnt or ATT e g Sprmtor ATT W Peering point VTccphanc mm urcabre system Voice Image Data Video Mariamquot CWWWM s Tmbm mmmm mus women 24 TIer1 ISP e 8 mt Sprint us backbone networkFiber map pm Cow man A my W Mm mm mam M mmxmaamwta ym m Internet stru oture39 network of networks 39 72 ISPs smaller often regional ISPs gt Connect to one 01 mole erl ISPs possibly oLhex tie SPs 9 TwerVZISP pays new ISP fur 39 mtercurme v cusmmeruf men pruwder Brahman 26 pm Wynn1n Wm mxm mnm Internet structure network of networks l Tier 3quot ISPs and local ISPs gt last hop access network closest to end systems Local and tier 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet r Evolution 27 2nd edition Iim Kumse Keith RossAddisoanesley Iuly 2002 Internet structure network of networks Evolution 28 39r r 2nd edition TimKiim K ith rWesley IulyZOOZ Optical Switching I All current switches are electronic I Current switches require photon to electron conversions optical to electronic E 0 interfaces I Optical switching will eliminate these interfaces gt Faster gt Cheaper Evolution 29 Signaling I Pulses gt In the same transmission path as voice signal Tones gt In the same transmission path as voice signal Computer Messages gt Outside of the transmission path gt Common Channel interoffice signaling CCIS gt Signaling System 7 SS7 gt SIP gt H323 gt Others Evolution 30 Signaling cum Gammon Channel Signaling Enhanced rvcs fmm Dgxtel Swmhmg and CCIS Evolution 31 Signalinghnm MEWVEL SLNEtW QLk ISBN ng nkaummiaamn Swmh I Luterhcs y 1 anunm by 2 hDKJSzWLYvzfm swung Cuntml sonnanhysnnmp Switch lmm ce Digtal Svm tch 515mm Computer Evolution 32 Survivability FIBER CUT gt Ian 4 1991 New York metro area 6 million homes without longdistance service New York Mercantile Exchange and New York Commodity Exchange shut down Fiber cuts are common Survivability SS7 FAILURE gt June 10 1991 California 2 million homes without phone serV1ce gt June 26 1991 Baltimore10 million homes in 4 states without service amp US government phones affected I SurvivabilitySVVITCH and POWER FAILURE gt September 17 1991 New York metro area 2 million homes without longdistance service 3 major New York airports close for 6 hours Evolution 33 Network Traffic 6 Vlctor S Fro st Dan F Servey Distinguished Professor Electrical Engineering and Computer Science U 39 ersity ofKansas 2335 Irving Hill Dr Phone 785 864 4833 FAX785 8647789 email frosteecskuedu httpwwwittckuedu Section 471 572 1 Traffic Traffic Characterization I Goals to gt Understand the nature of what is transported over communications networks gt Use understanding to improve network design I Traffic Characterization describes the user demands for network resources gt How often a customer Requests a Web page Down loads an MP3 Makes a phone call gt Size length Web page Son Phone call Traffic 2 Voice Traffic Aggregate Traffic I Requests for network resources from a large population of users Traffic 3 Voice Traffic Aggregate Traffic I Arrival Rate gt Number of requests time unit Calls sec I Arrival rate A I Holdmg Trrne length of tune the request will use the network resources gt Min call gt secpacket Average Holdm g sze T h Traffic 4 Voice Traffic Aggregate Traffic I Traffic Intensity load gt Product of the average holding tilne and the arrival rate Traf c Intensity p itle I Units of Traffic Intensity gt Erlangs gt CCS 1 CCS is 100 call sechr gt 1 Erlang 36 CCS I Traffic intensity is specified for the 39Busy Hour39 Traffic Voice Traffic Aggregate Traffic I A telephone line busy 100 of the time 1 Erlang I A telephone busy 6 min hour is how much traffic gt 01 Erlang gt 100 telephones busy 10 of the time is how much traffic gt 10 Erlangs Traffic Voice Traffic Aggregate Traffic I A telephone busy 100 seC Centi call Seconds CCS per hour 1 CCS I Arrival rate 1 call hour I Average holding time 100 seC I 80 gt 100 sec call 1 hour 36005ec1call hour 136 Erlangs 1 CCS I 36 CCS 1 Erlang Traffic 7 Voice Traffic Aggregate Traffic I Traffic is Random gt Holding time gt lnterarrival time time between calls I Common assumptions for probability density function pdf for gt Holding time N exponential gt lnterarrival time N exponential Sec on471 and A1 1 Traffic 8 Voice Traffic Aggregate Traffic Interarrival Histogram Peroentllems items39 Dlslrlbutxon 12 05417 8 766667 7 670833 65575 5479167 4383333 3 2875 quotLa 2191657 Midi 1 095833 00007591758 1318353 2535945 1953539 5271133 6588726 7 90632 inieranival Time Traffic 9 Voice Traffic Aggregate Traffic PThltt 1 239Mf0rt gt0Lmd 0f0rt lt0 1 PT1ltt 13 tf07 t gt0Lmd 0f0rt lt0 T I Interurrivultime Traffic Voice Traf c Aggregate Traf c 1 iq li i I Time i P ihh i II TrafficDiurnal Variation Voice Traffic Individual voice source I Speech inactivity factor Talkspun Takspurt Talkspurt Silence Silence mm mm 13 Voice Traffic Individual voice source I Talkspurt duration gt Random gt Average duration gt 0350 s to 13 s gt Exponentially distributed I Silence period gt Random gt Average duration gt 585 to 165 gt Exponentially distributed I Speech activity factor 035 to 436 Section 5 5 2 mm 14 Voice Traffic Individual voice source I Digital Speech Interpolation D81 6mm gt Uses quotsilence detection gt Multiplex at the talkspurt level gt View as call set up at talkspurt level gt NDoubles the capacity gt Analog version called quotTime Assignment and Speech Interpolation TASI gt Packet Voice with silence detection effectively does DSI Traffic 15 Voice Traffic Individual voice source I Signal redundancies gtVoice coding I Pulse code modulation 3711 PCM 8bits sample 8000 samples sec 64kbs I Adaptive Differential PCM 32kb s I Linear Predictive 24 to 16 kb 5 I For Voice over IP rate lt 8kb s gt G7231 is emerging as a popular coding choice G723 is an algorithm for compressed digital audio over telephone lines Traffic 16 Comparison of popular CODECs Compression Compressed rate Required CPU Resultant voice Added delay scheme resources uality 6711 PCM 64 no compression Not required Excellent NA 6723 M PMLQ 6453 Moderate Good 64 High Fair 53 6726 ADPCM 403224 Low 600d 40 Very low Fair 24 6728 LDCELP 16 Very high 600d Low 6729 CSACELP 8 High 600d Low There is no quotright CODECquot The choice of what compression scheme to use depends on what parameters are more important for a specific installation In practice G723 and G729 are more popular that G726 and G728 For details of other VoIP Codecs see Tram httpwwwzylraxcomtechprotocolsvoipirateshlIn Voice Traffic Individual voice source I Example How many calls can be supported on a system with the following parameters gt TDM gt Coding rate voice Channel ADPCM 32 Kbs gt DSI gt Line rate 1536 Mbs note aTlDSl line is 1544 Mbs I Number of ADPCM Channels 1563 Mbs32 Kbs 48 I With DSI you get 2 calls Channel 96 Traffic 18 Voice Traffic Packet Voice I Example Parameters for a packet voice system gt 1 source gt Sample rate 8000 samples sec ITU 3711 gt 8 bits sample 1 byte sample gt 8 mspacket Critical parameter gt Link rate 10 Mbs gt bytes packet 8ms packet8000 bytes sec 64 Bytes assuming no overhead bytes gt Holding time packet 64 bytes packet8bits byte 10 Mb s 512us Traffic 19 Voice Traffic Packet Voice I 512 us Transmit at a Constant Bit Rate CBR I I I I I I lt 8ms 8ms gt I time gt I 512 us Receive with variable interpacket arrival times I I I I I I I X ms 39 tilne X not equal 8ms because of network delays If X is too big packet may arrive too late for play out Traffic 20 Voice Traffic Packet Voice Perfect Multiplexing of N VolP sources I 512 us lfllz Il Ioo o l Nllfl I 8 ms I tune Traf c 21 Voice Traffic Packet Voice I Packet voice looks like a steady ow or Constant Bit Rate CBR traffic I However voice can be Variable Bit Rate or VBR gt quotsilence detection gt Variable rate coding I Problem After going through the network the packets will not arrive equally spaced in time Thus playback of packet voice must deal with variable network delays Traffic 22 Voice Traffic Packet Voice I Assume network dela is uniformly distributed between 5 ms 75 ms gt Same as having a fixed propagation dela of 25 ms with a random network delay un39 ormly distributed between 0 ms 50 ms I Note receiver will run out of bytes to play back after 8 ms I Solution gt Buffer 50 ms or 8 packets or 28 Kbits gt Worst case receiver will run out of data just as a new packet arrives Traffic 23 Voice Traffic Packet Voice I New problem networks delays are unknown and maybe unbounded I A voice packet may arrive at 85 ms and be too late to be played back gt Late packets are dropped gt Last packet may be played out in dead tilne I Packet voice video schemes must be able to deal with variable delay and packet loss Traffic 24 Voice Traffic Packet Voice G7251 is avoice coding 3292334 SAWS standard linear predic on compression algorithm w Payload V g esm 171kb5 12 Compressed 24 mm Pexfamm e Ewlunananhe Ammanquot mmmm Qumran pmmg Tvamc 25 Katsnyushxhd w w h m w a mac 1 Mn Vol P Quality mu 132 9n V V V Em gasnssn WW39 51 E Will 5 5 n mm mm M 25 6 40 Sun I uojm nu lamp ea 5 y Tvamc 26 lTUrT 39 G11470nw 39 39 39 Tum onm VoIP Factors in End to End Delay lAssumption maximum delay from earto ear needs to be on the order of 200 300 ms ITU 6114 lt 150 ms acceptable for most appllcatlons e 150ms 400 ms acceptable for lnternatlonal gt 400 ms unacceptable quot Sender Nelwmx39 mm 1 5mm l l E M WWW pumm umm 39Recewer quot Tvanc From hm 27 VoIP Factors in End to End Delay I Example Delay Budget depends on assumptions gt Formation of VoIP packet at TX N 30 ms 20ms of voice packet is default for Cisco 7960 router gt Other VoIP packet processing 70 ms see httpwwwmavaraucbrpdfvoippdf gt Propagation 20 ms gt Extraction of VoIP packet at Rec 30 ms gt Jitter Buffer N 100 ms C ensates for Variable network delay gt Total 250 ms m http www llghtmadmg Comdocument asp7ateltghtreadmgadoela5sseazzpagemmbele 28 Data Traffic General Characteristics I Highly variable I Not well known lLikely to change as new services and applications evolve Data Traffic General Characteristics I Highly bursty where one definition of burstyness is Peak rate Burstyness Average rate Traffic 30 Data Traffic General Characteristics Example During a typical remote login connection over a 192kb s modem a user types at a rate of 1 symbol sec or 8 bits sec and then transfers a 100 kbyte file Assume the total holding time of the connection is 10 min What is the burstyness of this data session Traffic 31 Data Traffic General Characteristics The tilne to transfer the file is 800000 bits 19200 b s 41 sec 80 for 600 4lsec 559 sec the data rate is 8 bits sec or 4472 bits were transferred in 559 sec Thus in 600 sec 4472 800000 bits were transferred yielding a average rate of 804472 bits 600 sec 1340 bitssec The peak rate was 192 Kb s so the burstyness for this data session was 192001340 143 Traffic 32 Data Traffic General Characteristics Call Val I I I I Session Interarrivals Call Dma on ill ELD Session Duration Voll I Packet Al Packet Interarrivals Auivals Voll Packet 39 Leug39hs Packet Lengths Tra fi 33 Data Traffic General Characteristics Asymmetric Nature of Interactive Traffic Think Time User Burst User Burst Idle Timk Idle Time Computer Burst Computer Burst This Asymmetric property has lead to asymmetric services Tra fi 34 Data Traffic General Characteristics I In Time Division Multiplexing TDM user must wait for turn to use link I Statistical Multiplexing Stat Mux gt Note high burstness leads to quotlongquot idle times gt By transmitting the bursts39 on demand the link can be efficiently shared gt To help insure fairness break the burst39 into packets and transmit on a packet basis Traffic 35 TDM vs Stat Mux Userl m Dwell time one time slot o o o IIID Server Server Traffic 36 Data Traffic General Characteristics I Element length gt Message gt Packet gt Cell I Arrival rate gt Message sec gt Packets sec gt Cells sec Traffic 37 Data Traffic General Characteristics I Traffic intensity lt 1 with one server p 17h where Average Packet Length in Bits f h Link Capacity in Bits sec C Average Packet Length in Bits L Link Capacity in Bits Sec C Traffic 38 Data Traffic General Characteristics I Smndard Assumptions gt Message length has an exponential pdf gt Interan39ival time has an exponential pdf Data was taken from speclal tmces m httpl lwwwnlanrnet Data was captured at thelntemet Upllnk of the Unlverslty of Auckland by the Wand Reseamh group m the year 2000 The tap was lnstalled on an oce llnk Tram 39 Figure 2 Complementary Cumulative Distribution Function 0 packet interarrival times over two backbone networks For 0048 link traces on a January 2003 backbone 1 and b January 2004 istrib ions 0 0048 traces with an exponential distribution straight line in loglinear scale but the BCpAu989 data set clearly I deviates from the exponential distribution 2 In me LongRange Depend nce Ten Vears oflntemet Traf c Modeling EEEtnthPt nmmmnn am at mm m t t n m t m quotWM Sprmt Owest swam D83 m iiilzli l KU ITTC has collected aggregate traffic data from Sun ower Datavision Note Came System15 a DOCS1S System 115mg C sco MC16 Cards T1115 a110W5f0r1 downstream Channe1and 6 upstream Channe15 Traf c 4 1 From the Internet into Datavision From Datavision out to the Intemet Mean 8876 Mbs Mean 5133 Mbs Maximum 18952 Mbs Maximum 12093 Mbs Traf c Mbs Man Feb 10 000000 2000 days 0 am 11 000000 2000 Man Feb 10 000000 2000 days 0 Rpr 11 000000 2000 From the Internet into DataVision From DataVision out to the Internet Mean 8555 Mbs Mean 4343 Mbs Maximum 21597 Mbs Maximum 12093 Mbs Traf c 43 Data Traffic Conclusions I Very bursty I Problems with traffic modeling gt Rapidly evolving applications gt Complex network interactions I Issues gt Do models match quotrealquot traffic flows gt Are the performance models based on specific traffic assumption robust Traf c 44 Video Analog video I Bandwidth 4 Mhz I Uncompressed rate 64 Mb s I Components of the signal gt Luminance gt Chrominance gt Audio gt Synchronization Traffic 45 Digital Video JPEG I quotJoint Photographic Expert Groupquot Voted as international standard in 1992 I Suitable for color and grayscale images eg satellite medical applications I Targeted for still images I Capable of reducing continuous true color or gray scale images to less than 5 of their original size I JPEG GIF and MPEG define the compression as well as the Video data format Section 123 Traf c 46 Digital Video MPEG I Moving Pictures Experts Group I Compresses moving pictures taking advantage of frametoframe redundancies I MPEG Initial Target VHS quality on a CDROM 320 x 240 CD audio 15 Mbits sec Traffic 47 Digital Video MPEG I Converts a sequence of frames into a compressed format of three frame types I I Frames intrapicture I P frames predicted picture I B frames bidirectional predicted picture Traffic 48 Digital Video MPEG Exploits frame to frame redundancies Traffic A 1000000 V F 5 800000 siZZanZV 93 600000 3 actzon a 400000 video E 200000 L o 0 200 400 600 800 100C Frame number 1000000 3 3 Frame sizes Each frame would 5 800 000 f 1k be transported V or ta 39ng i I 500000 head Video B frame using multiple E 400000 UJWVevwvrrWek packets s 200000 Wmmw 0 LL 0 MPEG2 Video Streams 0 200 400 600 overATM Steven Gnngeri Frame number 1 et ai iEEE Muitimedia 1998 50 Traffic MP3 MPEG Layer 3 Audio MPEG specifies a family of three audio coding schemes Layer1 2 3 Each Layer has and increasing encoder complexity and performance sound quality per bitrate The three codecs are compatible in a hierarchical way ie a LayerN decoder is able to decode bit stream data encoded in LayerN and all Layers below N The MP3 compression algorithm is based on a complicated psycho acoustic model The majority of the files available on the Internet are encoded in 128 kbitss stereo A high quality file is 12 times smaller than the original CDs can be created that contain over 160 songs and can play for over 14 hours on a PC Music can be efficiently stored on a hard disk and then directly played from there 51 Traffic Digital Video MPEG I Compression ranges gt 30 t01 gt 50 t0 1 I MPEG is evolving gt MPEG 1 gt MPEG 2 gt MPEG 4 gt MPEG 7 52 Traffic Digital Video MPEG4 I Audio Video coding for quotlow bit rate channels gt Internet gt Mobile applications I MPEG 4 is a significant change from MPEG 2 I Scalability is a key feature of MPEG 4 I MPEG 4 contains a Intellectual Property rights IPR management infrastructure Traffic 53 Digital Video MPEG4 Object based AudioVisual objects AVO AVO are described mathematically and given a position in 2D or 3D space I Viewer can change vantage point and update calculations done locally No distinction between mzturul and synthetic AVOs treats two in an integrated fashion Each AVO is represented separately and becomes the basis for an independent stream I Each AVO is reusable with the capability to incorporate onthe y elements under application control Content transport with QoS for each component Traffic 54 Conclusions I Network traffic defines the demands for network resources I Network traffic is dynamic gt Changes with the deployment of new application gt Time of day I Models for network traffic are continuing to evolve Traffic 55 Network Attributes and Technologies 5 Victor S Frost Dan F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas email frosteecskuedu http WWW ittc ku edu AttributesandTerhnalagies 1 Network Characterization I Network impairments gt The ph sical environment impacts networ protocols I Network performance criteria I Basic networking technologies gt Circuit Switching gt Packet Switching gt Virtual Circuit Switching AttributesandTerhnalagies 2 Network Impairments I Propagation Delay gt The Speed of Light Limitation Propagation delay Distance mSpeed of Light ms gt Example 3000 km ber link Speed of light in fiber 0663x10Bms Propagation delay 3000x103m 0663x103ms 15ms Speed of light in free space 103x103m 5 Speed of light in coax 0883x103m s I Clocking time Example Distance 3000km Data rate 1 Mbs Packet size 1000 bits Source Packet Clocking time LC 1 ms Destination Propagation time 10 ms AttributesandTerhnalagxes 3 Section 312 Network Impairments Propagation Delay I Satellite Networks gt 500ms I Terrestrial Networks gt 3 In or 10115 I DAN Desk Area Networks gt 3 m or lOns I LAN Local Area Networks gt 3 Km or lOus I PAN Personal Area Networks BAN Body Area Network AttributesandTerhnalagxes 4 Network Impairments Propagation Delay I MAN Metropolitan Area Networks gt 300 Km or lms I NAN National Area Networks gt 3000 Km or 101ns I GAN Global Area Networks gt 10000 Km or 301ns gt N ANs and GANs are typically called WANs Wide Area Networks I Interplanetary Networks AttributesandTethnalagies 5 Network Impairments I Error environment gt Wired Fiber Cable gt Wireless AttributesandTethnalagies 6 Network Impairments Error Environment I Random bit errors are independent I Bursty bit errors are correlated and come in groups AttributesandTethnangxes 7 Network Impairments Error Environment I Random bit errors are independent I Bursty bit errors are correlated and come in groups AttributesandTethnalagxes 8 Network Impairments I Example Impact of delay and errors gt Link rate 600 Mb s gt Free Space gt Link distance 3000 km gt10ms gt Packet size Payload 48 bytes Overhead 5 bytes Total 53 bytes 424 bits Armbueesandrechnaragxes 9 Network Impairments 14285 1 424 bits 600Mb s 7us packet lOms 07us packet 14285 packets in ight Question How do you cope with packets in error Attributes and Tethnalagxes 1 0 Network Impairments lExample gtLine rate 600 Mbs gtBit error rate BER 10399 I What is the time between errors gt On average see one error in 109 bits gt 109 bits 600 Mbs 166 sec between errors Attributes and Technalagxes 1 1 Network Impairments and Application Types l Real time interactive applications gt Require fixed or bounded delays gt Large delay variance can degrade performance gt Some realtime applications can tolerate some errors eg Voice Video Attributes and Technalagxes 1 2 Network Impairments and Application Types I Non Real time elastic applications gt Can tolerate delay variance gt Can not tolerate errors Email Telnet FTP WWW gt Require accurate delivery of information gt Does not require timely delivery of data Ambuees and Technalagies Network Performance Criteria Response time TR The time to correctly transmit a packet from Source to destination correctly implies Response time includes acknowledgments 8 Network Network ource Interface Interface Host Card Card Destination Examine key components of delay Host Ambuees and Technalagies Network Performance Criteria Response Time Time from source applications to N lC Waiting time in N lC to enter the network buffering time Time to transmit the packet clock the packet into the network Time for the network to deliver the packet to the destination s NIC I Time for destination s NIC to generate an acknowledgment Time for the acknowledgment to reach the source host repeating the above steps Attributes and Technalagxes 1 5 Network Performance Criteria Response Time Dependencies State of the network gt Current topology gt Active nodes gt Active links State of the other users gt Congestion Errors State of source destination host Link speeds Message sizes Message priorities Attributes and Technalagxes 1 6 Network Performance Criteria Response Time Statistics I Response time TR is a random variable I Probability density function characterizes TR I packets observed with delays greater than T I Variance I Mean Attributes and Tethnalagxes 1 7 Network Performance Criteria I Network designers focus on the components of response time that are a function of the network I Find the one way delay as a function of gt traffic load gt packet length gt topology I Focus on average response time or delay Attributes and Tethnalagxes 1 8 Network Performance Criteria I Throughput in b 5 packets sec cells sec I Normalized throughput B where C R Average errorfree rate Zrs passing a reference point in the network C Link Capacity Zrs S time the network is carrying error free packetsgooapat Attributes and Tethnalagies 1 9 Network Performance Criteria I Channel or link utilization gt The time the Channel or link is busy I Channel Efficiency gt The time the Channel is carrying user information impact of overhead Let D aser data bitspacket H network overhead bits packet then Ch I I S D anne ef ctency DH Ambuesandrechnaiagies Network Performance Criteria I Channel Capacity Smax is the maximum obtainable throughput over the entire range of input traffic intensities ie offered load Throughput Id eal Case 1 S max 1 Offered Load AttributesandTethnalagxes Network Performance Criteria Other Throughput Metrics l Maximum lossless throughput I Peak throughput I Full load throughput Transfer from local to remote host memory as fast as possible AttributesandTethnalagxes Network Performance Criteria Case Stud The ACTS ATM lntemetwork AAI r nKi39i A tagEgg in 39quot we Data Center wt Smux ran so g g x on mmanmmmgm 24 Network Performance Criteria Y Case Stu Wigwam mm m with D53 Maximum lossie PEEK Access E 25 Lines 20 E m pating E m g gazing m 5 2a 25 an 35 Aggregate paung bandwidth Mb5 Wandmdwa 25 Network Performance Criteria I Blocking Probability gt Packet gt Call W111 derive 5 apply blankingannulus later I Fairness I Security I Reliability Wm Maw 26 Network Performance Criteria I Reliability The reliability of a network can be defined as the probability that the functioning nodes are connected to working links Reliability 1 Network Failure I Here lets assume all nodes are working and analyze simple ring and tree networks AttributesandTerhnalagxes Network Performance Criteria 5 links every node has two paths Tree Network Ring Network Topology Topology NENetwork Element AttributesandTerhnalagxes Other Network Topologies Full Mesh Network Bus Network Topology Topology AttributesandTechnalagies Network Performance Criteria I Reliability for a 5 node tree network I Any of the 4 links fail the network is down I Let p probability of link failure and failures are statistically independent I Then Prob no link failure 1p4 I Probnetwork failure 1 1p4 AttributesandTethnalagies Network Performance Criteria I But 114 1 4P 6192 4193 P4 I Probnetwork failure 4p 6132 4193 p4 I Assuming p is small then for 5 node tree network the Probnetwork failure z 4p AttributesandTeChnalagies Network Performance Criteria I Reliability for a 5 node ring network I Ring network has 5 links I Ring network can have one link failure and still be working note one more link can fail I Let q 1 ppr0bability of link good I Probnetwork goodPr0ball good or one failed and 4 good q5 5p 14 ZProbUink Jfailed and all other links good Spq I So Probnetwork failure 1 lt15 510 lt14 AttributesandTeChnalagies Network Performance Criteria I Expanding Probnetwork failure 10pzq3 101gt3q2 5p4q 195 I The dominant term assuming p small is 1 Opzq3 AtkibufesandTechnalagies Network Performance Criteria Network Failure Probabilities Tree Ring P 4P 10pzq3 001 004 000097 0001 0004 10395 10395 4XlO395 10399 10397 4XlO397 103913 AtkibufesandTechnalagies Network Performance Criteria Example Traf c Network Typical QoS SOS Data Type Service Message Size Battle IP Unicast 100500 gt95 0 5sec Comman Bytes Data Mulitcast Situation IP 0 5 9c Awareness Broadcast lt100 Bytes gt95 A QoS Quality of Service IP packets successfully delivered for this RFP SoS Speed of Service Average time to deliver error free packets From DoD Proposal RFP October 1997 AllnbufesandTechnalagxes Network Performance Criteria Example Generrc servrce Vrrtual Tolerable error Acceptable Tolerable delay bandwidth rate 39 ariation delay Real time video gt 4Mbs lt 106 100 ms lt5 ms Web browsing gt250 Kbs lt 1 05 100 ms lt10 ms Multiparty gt 100 Kbs lt 1 05 50 ms lt5 ms network games Te e gt1 Mbs lt 104 quot 1 sec lt500 ms commuting From IEEE Network Maginze JanFeb 1997 pp 59 AllnbufesandTechnalagxes Network Performance Perspective UserOriented I Minimum application response time Delay guarantee I Maximum application throughput Throughput b s guarantee I Low loss Maximum packet loss guarantee I Highly reliable Availability guarantee I Very exible I Secure I Low cost AttributesandTethnalagxes Network Performance Perspective Network Manager Provider I Maximum throughput for all users I Effective congestion control I Power Throughput Delay I Easy of management I Highly reliable I Fairness I Ease of billing I Low cost AttributesandTethnalagxes Network Performance Perspective Network Designer Developer Vendor I Simple design I Robust I Scales gt Number of users gt Geographical distribution gt Speed I Efficient use of resources CPU links and memory I Evolvable AttributesandTechnalagies Network Performance What Can the Network Guarantee I Quality of Service Q08 Absolute Contractual performance guarantees Examples gt Sustainable rate gt Peak rate gt Packet delay average and standard deviation gt Packet Cell loss rate I Network must reserve resources to provide QoS I ATM is designed to provide QoS AttributesandTechnalagies Network Performance What Can the Network Guarantee Class of Service CoSRelative performance guarantees Examples gt Best Effort lowest priority Current Internet is Best Effort 7 email ftp gt Gold medium priority 7 Point of sales transaction gt Platinum highest priority 7 oice 7 Video Network performs packet labeling and priority queueing to provide COS Differential Services lPDiffServ provides C08 in the Internet AttributesandTechnalagies Network Performance What Can the Network Guarantee I Network engineering issues gt Q08 Reserving resources implies per connection processing and saving flow st ate information for eac ow Reserving resources implies call setu Reserving resource thus implies complex per flow processing in each switch gt COS Relative services implies simplified router processing only look at a label and queue appropriately Relative services implies no unique per flow processing gt Hybrids Q08 in the enterprise and CoS in the core network Q08 in the core network and COS in the enterprise AttributesandTechnalagies Network Switching Technologies I Circuit Switching I Message Switching I Packet Switching gtDatagrarn gt Virtual Circuit Switching gt Cell Switching h 1325 Section 71 r 73 Network Switching Technologies Switch Lines Input port 2 Line Card B Line Card C Line Card Interface Control h lgxes Network Switching Technologies I Switching transfers information from input ports to output ports Input port 2 Output port 3 Line Card B 3939gt Line Card C I Elements of Switches gt Line cards multiple interfaces card gt Switch fabric gt Control mappings gt Management gt Billing AttributesandTechnalagxes Network Switching Technologies Circuit Switching M o End Office Trunks Local loop End Office Longrdjstance Longrdjstance Of ce Of ce I On demand call set up I Dedicated path I Fixed network resources held for call duration AttributesandTechnalagxes Network Switching Technologies Circuit Switching I Phases of a call gt Call establishment gt Information transfer gt Call disconnect I If no network resources are available the call blocks fast busy signal I Network resources can be easily defined e g Voice line AttributesandTechnalagxes Network Switching Technologies Circuit Switching I The Public Switched Telephone Network PSTN I DWDM Optical Networks I Dialup modems I Customers can not use idle channels that is unused capacity is wasted AttributesandTechnalagxes Network Switching Technologies Message Switching Store store Store amp amp amp Forward Forward Forward I No Dedicated path I Address information is added to the message I Store if output port is busy I Trade off delay for blocking I If message is corrupted then retransmit entire message Attributes and Technologies 49 Network Switching Technologies Message Switching I If message arrives to empty system then it is transmitted at the FULL LINE RATE I Transmission at the FULL LINE RATE is shared among the all the users I If a message arrives to a busy system it waits Server Message Buffer This is called a Statistical Multiplexer Attributes and Technologies 50 Network Switching Technologies Message Switching Forwarding O O o gt gt 0 EO Store 3 amp 0 Forward p Node Attributes and Tethnalagies 51 Network Switching Technologies Packet Switching I Break up messages into smaller units Packets 11 II I The process of breaking up larger information units into smaller parts is called Segmentation or Fragmentation II I The process of gutting together smaller parts into larger information units is called Reassembly I Segmentation and Reassembly SAR can happen multiple times to the same information stream or flow Attributes and Tethnalagies Network Switching Technologies Packet Switching Methods I Datagrarn Packet Switching gtConectionless IVirtual Circuit Packet Switching gtConnection oriented Attributes and Technalagxes 53 Network Switching Technologies Packet Switching gt Datagrams I Each packet is treated independently I Packets with same destination may take different routes through the network I Each nodes makes independent routing decisions I No call set up is required I Nodes keep no state information I No Q08 is guaranteed Attributes and Technalagxes 54 Network Switching Technologies Packet Switching gtDatagrams User Data inside envelope From Jane Doe Address To John Smith Address Attributes and Technologies Network Switching Technologies Packet Switching gt Datagrams l Store Store Store amp amp amp J Forward Forward Forward Data Destination Address Source Address Attributes and Technologies How do Packets find there way Routing and Forwarding routing algorithm local forwarding table header Value out ut link 0100 3 01m 2 em 2 1001 1 Value in arriving packet s header om 1 3 Value related to destination Madx ed mm Comm Networking A 117 Dawn Approach Fmtmmg m Mme 4nd edmanlxmKumsEKexthRass Addxsaanesley Capyngm WNW andTEthmlasmsu 19962002 I F Kurase and KW Russ All Rxghts Reserved Network Switching Technologies Packet Switching gt Datagrams lDatagram is an example of a connectionless service lInternet Protocol IP provides a connectionless service AttnbutesandTechnalagxes Network Switching Technologies Virtual Circuit Packet Switching I Virtual circuit packet switch is connection oriented I Connection oriented does not imply Virtual circuits I A quotlogical connection is established between the source and destination I All packets ow over the same route through the network I Packets still quotstatistically share link Attributes and Technalagxes 59 Network Switching Technologies Virtual Circuit Packet Switching I Forwarding decisions are made based on a virtual Circuit identi er not on the full address I Packet share transmission facilities I Switches save state connection I State is saved for duration of the connection I 208 can be guaranteed AttributesandTechnalagxes Virtual circuits signaling protocols used to setup maintain teardown vc usedin ATM framerrelzy X25 These are Fa ketwathS amflaw hegms all canneclzd m an l Network Technologies quotNote Do not need the same VG emrtoremi Network Switching Technologies Virtual CircuitDatagram Tradeoffs Example Find the time to transmit a 1 Kbyte message coast to Coast is the USA 3000Km on a 600 Mbs link a Using Datagrams 18000 600Mbs 10 ms 10ms 13 us Call Set up b Using Virtual Circuits A 30ms I Data Transmission AttributesandTethnalagxes Network Switching Technologies Virtual CircuitDatagram Tradeoffs Example Find the time to transmit a 375 Mbyte message coast to Coast is the USA 3000Km on a 600 Mbs link a Using Datagrams 510ms b Using Virtual Circuits can set u 530ms Data Transmission Key issue is holding time relative to call set up time AttributesandTethnalagxes Comparison Virtual Circuit Circuitswikhmg Message Switching Datagram I Packeliwitchmg PaCkEtiwitchmg 1 WW i Attribute m mth 65 m a d Prentice H an 2cm Network Switching Technologies I Permanent Virtual Circuits PVC gtVC numbers assigned by management usually manual I Permanent Virtual Circuits are always up mm m mm 66 Network Switching Technologies I Switched Virtual Circuits SVC I Automatic user initiated call setups I Call set up is ondernand AttributesandTechnalagxes Network Switching Technologies Switch State I Circuit switched networks gt Switches have hard state they save knowledge of the connection throughout the duration of the call I Pure datagram networks gt Routers switches have no state of each connection or ow gt Can use a label39 inside the packet for priority queuing AttributesandTechnalagxes Network Switching Technologies Soft state I Often multiple related ows pass through a network element I Implicit identification of what datagrams constitute a ow can be done based on source destination addresses I The states can be used for resource management RSVP Resource Reservation Protocol I State of ows are temporarily saved I Unused soft state is cleared by time outs AttributesandTechnalagxes Network Switching Technologies Attributes of datagram transmission I Decentralized control I Simple hosts and switches I No call processing I Difficult to provide 208 I Difficult to bill for services I Difficult to manage resources to control congestion note if no congestion then not an issue AttributesandTechnalagxes Network Switching Technologies Attributes of Virtual Circuit Connection Oriented Networks l Provides Q08 I Accommodates billing I Centralized control I Follows well known model of the PSTN I Simpler switching I Complex control I Soft state is trying to give connectionless systems attributes of an connection oriented network Attributes and Technalagtes 71 Datagram and VC networks I Networks that only provide VC services at the network layer are typically called VC networks I Networks that only provide connectionless services at the network layer are typically called datagram networks AtktbufesandTechnalagtes Network Switching Technologies Cell Switching I Packets tend to be variable size I Variable size packets increase hardware complexity I Variable size packets increase difficulty of providing integrated services with Q08 I Solution Small fixed length packets called Cells I ATM is based on cell switching with gt 5 byte headers gt 48 byte payloads AthbufesandTechnangxes Data Link Control 10 Vlctor S Fro st Dan F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas 2335 Irving Hill Dr Lawrence Kansas 66045 Phone 785 8644833 FAX7 5 8647789 email frosteecs ku edu httpwwwittckuedu Chapter 5 Outline I Common protocol functions I DLC functions gt DLC Framing gt Error and ow control gt Performance of DLC gt Example of a standard DLC protocol gtHDLC gt Open loop ow control Protocol functions I Encapsulation I Fragmentation and reassembly I Connection control I Ordered delivery I Flow control I Error control I Addressing I Multiplexing I Transmission services DLC 3 Protocol functions I Encap sulation adding control information gt Address gt Error detection correction bits gt Protocol control I Fragmentation and reassembly gt Max packet size DLC 4 Protocol functions I Connection control gt Connection oriented gt Signaling gt Graceful set up and tear down I Ordered delivery gt Deal with reordering gt Lost packets DLC 5 Protocol functions I Flow control gt Match transmit and receiving rates gt Prevent over running buffers I Error control gt Error detection gt Error correction gt Adds bits to packets gt Sometimes causes retransmissions DLC 6 Protocol functions I Addressing gt Different la ers contain different addressed e g MAC lP a dresses and socket I Multiplexing gt Enables multiple customers to use one pipe MAC address allows sharing on LAN In TDM address is the time slot In the internet host id is the IP address I Transmission services eg priority and security gt Priority gt Security gt Other layer speci c services eg framing Data Link Layer Introduction I Data Link layer provides a error free pointtopoint bit pipe for transmission of network layer PDU s gt Framing gt Error Control gt Flow Control gt Error Detection Framing I Character Count gt Insert PDU length as first character in the frame One characler lSl1l2l345l6l7l8l98l0l1l2l345l6l8l7l l9l0l1l2l3 m ame 2 5 characters 5 characters 8 characters 8 characters Error l5l1l2l34l7l6l7l898l0l1l234l5l6l8l7819l0l1l2l3 n V Frame 1 Frame 2 Now a Wrong character count Pram CamputerNetwarks3xd EdmanAS Tanenbaum Du 9 P renhce H 5111996 Framing I Flags gt Insert special bit patterns called flags at start and end of the frame 7 01111110 011011111111111111110010 O11011111011111011y39010010 Stuffed bits 0110111111111111111110010 Pram CamputerNetwarks 3rd Edman A s Tanenbaum PrenhreHall1996 Du 10 Error and Flow Control Network and data link layers only Network Layer communicate via 1 messages with Data Link Layer specific data structures Physical Layer The data link layer processes those Packets structures with a set of pro 0 6 dm es Data L1nk Layer Frames DLC 1 1 Error and Flow Control Required procedures I FromNetworkLayer gt Fetch information from the network layer I ToNetworkLayer gt Deliver information to the network layer I FromPhysicalLayer gt Fetch information from the physical layer I ToPhysicalLayer gt Deliver information to the physical layer DLC 1 2 Error and Flow Control Required procedures I Timers gt StartTiIner gt StopTiIner gt StartAckTiIner gt StopAckTiIner I EnableNetworkLayer gt Turn on ow of information from the network layer I DisableNetworkLayer gt Turn off ow of information from the network layer DLC Error and Flow Control Events I Networks are Asynchronous gt Arrival tiIne of packet and acknowledgments are unknown I Arrival of packet and acknowledgments triggers some action by the protocol gt Action is a function of the type of arrival gt State of the protocol I Examples gt FrameArrival gt CksumErr DLC 1 4 Error and Flow Control Protocol 1 The Unrestricted Simplex Protocol I Assumptions gt One directional information ow gt Infinite buffers gt No errors gt Network Layer always has a packet to send Network Data Link Data Link Network La er La er La er La er DLC 1 5 Error and Flow Control Protocol 2 The Simplex Stop amp Wait Protocol Assumtions I One directional information flow I No errors I Network Layer always has a packet to send I Finite receive buffers gt Finite buffer means that there must be some way to stop the transmitter from sending when the buffer is full DLC 1 6 Error and Flow Control Protocol 2 The Mlex Stop amp Wait Protocol Assume Network Layer always has data to send Channel DLC 1 7 Error and Flow Control Protocol 2 The Simlex Stop amp Wait Protocol Assume Network Layer always has data to send Network Data Link Data Link Network Layer Layer Layer Layer DLC 1 8 Error and Flow Control Protocol 2 The Mlex Stop amp Wait Protocol Assume Network Layer always has data to send Channel DLC 1 9 Error and Flow Control Protocol 3 The Simlex Protocol for a Noisy Channel I Assumptions gt One directional information ow gt Network Layer always has a packet to send gt Finite receive buffers gt Allow errors I Data link protocols must address gt When to retransmit gt What to retransmit DLC Error and Flow Control Protocol 3 The Simplex Protocol for a Noisy Channel I Timeout to determine when to retransmitt I Example gt Assume a 1 ms propagation time gt Assume a 1 ms receiver packet processing time gt Timeout interval gt21 ms If no acknowledgment received in 21 ms then I Packet in error I Acknowledgment lost DLC Error and Flow Control Protocol 3 The Simlex Protocol for a Noisy Channel gtTirneout interval too short Dup1icate packets gtTirneout interval too long Reduced throughput DLC Error and Flow Control Protocol 3 The Simplex Protocol for a Noisy Channel I Sequence numbers are used to determine what to retransmitt gt Transmitter assigns a number to each frame gt Receiver keeps track of the expected frame number gt How to deal with out of sequence frames ie if the received sequence number does not match what is expected The frame is dumped for some DLC protocols Frame stored DLC Error and Flow Control Protocol 3 One Simlex Protocol for a Noisy Channel DLC Error and Flow Control ng Window Protocols Assumtions I Two directional information ow I Network Layer always has a packet to send I Finite receive buffers I Finite number of bits sequence number I Bit errors I Piggybacking gt Put Acknowledgments in reverse traffic ow gt Increases protocol efficiency gt Reduces interrupts DLC 25 Error and Flow Control Sliding Window Protocols I Advantage pipeline I Why called sliding window gt Assume 2 bits Sequence number gt Possible frame numbers 0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3 0 1 2 3 0 1 23 Receive ack and advance window DLC 26 Error and Flow Control Sliding V ndow Protocols A to B Data Traffic B to A Ack Traffic IE El B to A Data Traffic A to B Ack Traffic DLC Error and Flow Control Sliding Window Protocols I Transmitter keeps a list of sequence s it can use gtSending window I Receiver keeps a list of sequence s it will accept gtReceiving window I n bits sequence number DLC Error and Flow Control Sliding Window Protocols I Sequence numbers in range 02n1 I This allows N2n1 packets to be sent before getting and acknowledgment l Requires N2n1 packets buffers gt Why not use all 2 seq s for n 3 then have 0 7 8 seq s DLC Error and Flow Control Sliding V ndow Protocols How many frames can be pipelined Problem if max frames in pipeline 2n Assume that frames in pipeline S 2 Assume n 3 Node A sends 07 8 frames Node B receives 07 0k and sends Ack Now B expects next unique packet to have seq 0 First Ack gets lost Packet 0 of Node A tilnes out Node B receives another packet 0 expects a packet 0 but this is a duplicate I Thus frames in pipline lt Znl DLC Error and Flow Control Sliding Window Protocols How many frames can be elined 1 I Now with frames in pipline N 2n1 gt 06 7 frames I Node A sends 06 I Node B receives 06 ok I Node B sends Acllt I Acllt gets lost DLC Error and Flow Control Sliding Window Protocols How many frames can be pipelined 2 I Node A times out I Node A retransmitts 06 I But Node B is expecting frame 7 I Node ignores 06 often will send a RR frame explicitly telling Node A it is expecting Frame 7 DLC Error and Flow Control GoBackN Protocol I Types of sliding window protocols gt Go Back N gt Selective Reject I Focus on which frames to retransmit I Pipeline send up to N frames before receiving an acknowledgment I Delete correctly received out of sequence frames DLC Error and Flow Control GoBackN Protocol EX ple I Distance between nodes 6600 km I Frame length 1000 bits I Rate 12Gbs I Large delaybandwidth product network DLC Error and Flow Control GoBackN Protocol Example l Case 1 Stop and Wait N1 gt Frame transmission time 083us gt Propagation time 22 ms gt Transmit frame at t0 gt At 083us 22 ms frame received gt At 083us 44ms the acknowledgment is received therefore transmitted 1000 bits in 083us 44ms gt Effective transmission rate is 100044ms 227kbs gt Efficiency 227Kbs 12Gbs 0002 efficient DLC Error and Flow Control GoBackN Protocol EX ple lCase 2 Pipeline 53000 frames gtNote with N53000 the rst acknowledgment arrives at the transmitter just in time for the next frame to be transmitted The transmitter is never blocked The protocol is 100 efficient DLC Error and Flow Control GoBackN Protocol 083usl 22ms Frame 53000 Ack for Frame 1 DLC Error and Flow Control Example I Distance between nodes 1 km I Frame length 1000 bits I Capacity 150 Mb 5 I No errors I Delaybandwidth product gt Assume free space gt 139 1000m C 333 us 9 Access Network gt 2 tR 1000 bits DLC Error and Flow Control Example I Case 1 Stop and Wait N1 gt Frame transmission tilne 666us gt Propagation time 333us gt Transmit frame at t0 gt At 666 us 333us frame received gt At 666us 666us the acknowled ment is received therefore transmitted 10 0 bits in 666us 6 66us gt Effective transmission rate is 1000133us 75Mbs gt Efficienc 75Mb 150Mb s 500 efficient DLC Error and Flow Control Example I Case 2 Stop and Wait N1 Reduce capacity to 15 Mbs Frame transmission time 666us Propagation time 333us Transmit frame at t0 At 666 us 333us frame received At 666us 666us the acknowledgment is received therefore transmitted 1000 bits in 666us 666us Effective transmission rate is 1000672us 1488 Mbs VVVVVV V ciency 1488Mbs150Mbs 992 ef cient DLC Error and Flow Control Example I Case 3 Stop and Wait N1 Capacity to 150 Mbs Frame transmission time 666us WAN D1000km Propagation time 3333us Transmit frame at t0 At 666 us 3333us frame received At 666us 6666us the acknowledgment is received therefore transmitted 1000 bits in 666us 6666us Effective transmission rate is 10006672us 149Mbs Efficiency 149Mbs150Mbs 01 ef cient VVVVVV V 41 DLC Error and Flow Control Example I Case 4 Sliding window N1023 gt Capacity to 150 Mbs gt Frame transmission time 666us gt WAN D1000km Propagation tilne 3333us gt Transmit frame at t0 gt Note 2 TR 999900 bits or in frames 9999 frames gt Since time to transmit 1023 frames gt 9999 Always have a sequence number to use Never have to wait for ACK gt Efficiency 100 42 DLC Error and Flow Control Example lm 3333us Frame 1000 Ack for Frame 1 DLC Error and Flow Control GoBackN Protocol 1 I Problem If there is an error or lost frame then what rules are used to determine the frames to retransmit I Go baCk N gt Retransmit all frames transmitted after the erred frame gt The receiver ignores all out 0f sequence frames DLC Error and Flow Control Go BackN Protocol 2 Example Transmit 12345 and frame 2 is in error then 3 4 and 5 are received out of sequence and retransmit 2345 mc 45 Sliding Window Movie SLIDING UJINDUUJ HNIMHTIUN UNIUEBSITY 0F KHNSHS mc 46 Error and Flow Control Selective Repeat I Receiver accepts out of sequence frames I Requires buffers in receiver and transmitter I Requires extra processing to deliver packets in order to the Network Layer DLC Error and Flow Control Other Enhancements I Negative Acknowledgment gt When an out of sequence frame is received the receiver sends a NAK frame to the transmitter the NAK frame contains the sequence number of the expected data frame gt NAK enables faster error recovery without a NAK time out must be used to learn about errors DLC Error and Flow Control Sliding Window Protocols Piggyback ACKS Reverse traffic is used to Piggyback ACKS A to B Data Traffic B to A Ack Traffic IE El B to A Data Traffic A to B Ack Traffic DLC Error and Flow Control Other Enhancements Acknowledgment timer I If there is light or no reverse traffic then CKS may not be sent I An acknowledgment timer is used to insure ACKS are sent I Upon receipt of a frame an AckTimer is started If reverse traf c arrives before the AckTimer fires then pig back the ACK If the AckTimer res then sen a supervisory ACK frame DLC Error and Flow Control Performance t I Definition for effective rate R Bits Delivered e Time to transfer Bits given the protocol DLC Error and Flow Control Performance m I Length of data packet bits D I Number of overhead bits packet nO I Link Rate bs R I Length of Ack Packet bits na I Frame size nf D n0 I Oneway propagation delay E I Processing time in receiver and transmitter tpm DLC Error and Flow Control PerformanceStop amp Wait I Effective rate and ef ciency for simplex stopandwait protocol gt tuck na R gt tf nf R gt Time to transmit one frame to t0 2 r tf tuck 2 15W 2rt n nR proc a f DLC Error and Flow Control PerformanceStop amp Wait I Ref Hfnot0 Dto I E iciency RefR 7 Z f a n 2RT l mc 1 1 p quotf quotf DLC Error and Flow Control PerformanceStop amp Wait Limiting Case Assuming 1 1 1 1 gt0 na ltlt nf SO nf De ne 21R 2 lt1 so T g T DelayBandwidth Product pm pm 71 3 quotM 71f 50 U gt0 For fixed DLL parameters 71 f As DelayBandwidth Product T then Eff1c1ency L 1 770 1 M E frames in RTT quotf quotf DLC Error and Flow Control PerformanceStop amp Wait I Example gt Frame size 1024 bytes gt Overhead ACk 8 bytes gt E 50 ms Case 1 R30 Kb s gtEfficiency 73 Case 2 R15 Mbs gtEfficiency 5 DLC Error and Flow Control PerformanceSliding Window Protocol I Case 1 Large window gt Window Size N gt Transmit N packet and wait for ACk gt Making the same assumption as before gt First ACk arrives at sender at n 2239 f DLC Error and Flow Control PerformanceSliding Window Protocol I Case 1 Large window gt If time to transmit N packets gt time to get first aCk OanfR gt21 nfR Then Channel is always busy sending packets Efficiency nf nu nf DLC Error and Flow Control PerformanceSliding Window Protocol I Case 2 Small Window gt If time to transmit N packets lt time to get first ack Or anR lt 21 71 Then channel is M always busy sending packets Time is wasted waiting for an Ack DLC Error and Flow Control PerformanceSliding Window Protocol I Time to send one window an R I Number of bits sent an I Time to send an bits 21 11 R I Effective rate anZ C 11 R I Ef ciency anZ CR 11f NZIR nf 1 DLC Error and Flow Control PerformanceSliding Window Protocol I Example gt Frame size 1024 bytes gt Overhead Ack 0 bytes gt E 1 ms gt Rate 40 Mbs Case 1 N 12 gt Efficiency 100 gt 40 Mbs Case 2 N 8 gt Efficiency 75 gt 30 Mbs Case 3 N 4 gt Efficiency 37 gt15 Mbs Note you can control the rate by changing N DLC Error and Flow Control PerformanceStop amp Wait with Errors I Let p Probability of a bit error I Assume bits errors are random I Let Pf Probability of a frame error Pf 1 1p quotf I If p ltlt 1 then Pf pnf I For stop amp wait Re with mm 1 Pf Re DLC Data Link Control Standards I HDLC gt High level data link control I LAPB gt Link Access ProtocolBalanced I LAPD gt Link Access Protocol D gt Used in ISDN and based on LAPB DLC HDLC Frame types I Information Frames lframes gt Carry user data I Supervisory Frames Sframes gt Carry control information Acks ow control I Unnumbered Frames Uframes gt Used for line initialization DLC Data Link Control Standards I Flag I Address Control Data I CRCI Flag I 8 bits 8 bits 8 bits 16 bits 8 bits Address 39gt Provide capability for multidrop lines DLC Data Link Control Standards I Control gt Sequence Numbers gt ACk gt Frame type I Data gt Network layer PDU gt Variable length I CRC DLC Data Link Control Standard I Control structure Ifrarne gt Bit 1 0 indicate I frame gt Bits 2 4 are the sequence number gt Bit 5 is the P011 Final P F bit gt Bits 6 8 are the Next bits ie sequence number for the piggyback ack Final DLC Data Link Control Standard I Control structure Sframes gt Type 1 Receive Ready RR Used to ack when no piggyback used gt Type 2 ReceivernotReady RNR Used to tell transmitter to stop sending gt Type 3 Selective Reject Not used in LAPB and LABD DLC Data Link Control Standard I Data link control protocol modes gtNormal response mode NRM Master slave gtAsynchronous balanced mode ABM Equal partners DLC PPP The Internet PointtoPoint Protocol I PPP is a variation of HDLC originally designed to encapsulate IP and other datagrams on dial up or leased carrier circuits PPP is used in Packet over SONET for high speed Internet connections Address Flag Control 01111110 1111111 00000011 l Protocol Information CRC ag 01111110 1 I 139quot l quot i All stations are to Unnurnbered Speci es What kind of packet is contained in the accept the frame frame payload eg 1P IPX PPP Frame Format DLC 70 PPP The Internet PointtoPoint Protocol MIG Bah sldes agree Mmentlcitlon deemed an opllons Sucessl39u m m Filled 35 m T tamer Dona MP ar g atinn NCP Network Control Protocol From Computer Networks 3rd Edition AS Tanenbaum DLC Prentice Hall 1996 Open Loop Control I Concept gt Establish an expectation on the nature of the traffic generated by a source Average rate Maximum burst size eg number of consecutive bits transmitte gt If traffic exceed the expectation traffic contract then Tag packet as discard eligible DE Discard or loss probability Possible actions I Drop immediately prevent packet from entering the network I Allow into the network but drop if congestion DLC Open Loop Control Frame Relay Networks I Negotiated Traffic Parameters I Committed Information Rate in b s CIR I Committed Burst Size in bits Bc I Excess Burst Size in bits Be I Measurement Interval in sec T Bc CIR DLC Qpen Loop Control Frame Relay Networks I Accept and quotGuaranteequot Delivery of Up To Bc in Any T CIR I High Loss Priority DE0 I Accept Up To Bc Be More In Any T I Low Loss Priority Network May Discard If Congested DE1 I Excess Over Bc Be in T Discarded At Access Point m 74 l 5 mm W m WWW mm M m nanny m 75 m m m Open Loop Control Token Bucket Algorithm open 100p maximum of the 110mm the netwoxk Txa ic shaping andoxpoljcing hammer mm To Network Input Packets Tmmmkmm A packet must have a a w K transmit to en to k leave the controller I 1quot quotmmquot tokens See section 781 T k ns 3quot a a constant mu Rate Control Token Bucket Algorithm I Modes of operation gt Packets arriving to an empty token buffer are discarded when N0 Or Packets arriving to an empty token buffer are marked when Ngt0 I Scheme controls gt Average rate into the system gt Maximum burst size into the system DLC Rate Control Token Bucket Algorithm I Example gt Suppose the system had no arrivals for a long time then the packet buffer would be empty and the token buffer would be full ie have K tokens gt A large burst of packets arrive gt K consecutive packets would be transmitted and then packets would be leaked into the systems at the token arrival rate I K controls the maximum burst size I The token arrival rate controls the average transmission rate DLC Rate Control Token Bucket Algorithm Example I Parameters gt R OC 12c 622 Mbs gt Packet size 53 bytes gt Token buffer holds 100 tokens gt Intertoken time 85 us I What is the average ow into the network in b s gt 85ustoken gt 85uscell 1176 x103 cellssec 950 Mbs I What is the maximum burst size into the network gt 100 packets DLC Rate Control Leaky Bucket Algorithm I Leaky bucket algorithm is a special case of the token bucket I K 1 leaky bucket algorithm I Maximum burst size 1 I Both token and leaky bucket algorithms can work at byte or cell levels I Violating cell can be either dropped or tagged DLC Communications Networks Landscape and Issues 2 Victor S Frost Dan F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas 2291 Irving Hill Dr awrence Kansas 66045 Phone 785 8644833 FAX785 8647789 email frosteecs kuedu httpwwwittc kuedu Landscape 1 Outline I Drivers Customer expectations I Drivers Technology lThe Issues in Networking Landscape 2 Communications Landscape I Voice I Data E mail Web Network based applications image I Video Broadcast Video on Demand Video Over the Web I Wired amp wireless I Today gt Separate networks I Rapidly emerging gt An integrated packet network I Triple Play Voice Internet Video Landscape 3 Drivers Customer Expectations I Sense of always connected I Instant response high bandwidth I Ubiquitous connectivity I Multimedia support I Conferencing simultaneous communications with multiple users Landscape 4 Drivers Customer expectations I Mobility support I Personalized information services I Context sensitive information services I Absolutely secure I Cheap Landscape 5 The Value of the Net I Metcalf s Law The value of a network increases as the square of the number of connected users some say nlogn I The value of a network increases as the square of the access bandwidth I The value of a network increases as the square of PC power I Number of connected users bandwidth user and host capabilities are increasing gt Value of the Net T Landscape 6 Drivers Technology Traffic Growth I Sidgemore s Law Internet traffic doubles every three months original over hype Myth I However Internet still growing I Access rates gt Modem 50kbs gt CableDSL 1 10 Mbs FTTH 100Mbs gt Seeh or satisticshtml Snume mm M Lunar Internet Sn wzre Cnnsnnlum ltwww v217 11gt Landscape 7 Drivers Technology I Moore s Law gt Processing power doubles every 18 months gt Moore s Law has been true for the past 20 years I Gilder s Law The Law of Telecoms gt Total telecommunications system capacity b s triples every three years Landscape 8 Hul mn to MD mu Mb 2 94 MM Emma E szme Emarne E JNE EDZHg b W IGhs I E g C lhemu E M Yhnu EDZMb j E f amp senmm E mm T Mm AMI omm I mums mnmm We mm 55 quot g Wham ll ELKhs R CLGhevradmnm GSM Flfs mum 289m A m mum WIreIessMobe drnrea 39 39 3 mm P Nomadic DIaIup 44 3 p 2508 Date of first use Landscape 9 Pram Ttltcnm Edhnlm39s Lm 0f BandwidthEEE Sptclnll39n July 2mm Issues in Networking Campus Example Telephone PSTN 1 Campus 15900 Ellsworth N ATampT Telephones Ha Landscape 10 Issues in Networking I How many lines do you buy from ATampT I To guarantee every campus phone can always get an outside line N15000 I Too expensive lines cost per month Landscape 11 Issues in Networking I Solution Gamble I Assume gt During the busy hour of the day 10 of the phones makes 2 calls gt The call duration is about 3 min gt The customers will tolerate a 1 in 100 chance of getting a busy signal because all the lines to ATampT are busy Landscape 12 Issues in Networking I Apply basic traffic engineering I Erlang s Blocking Equation l N is about 160 ltlt15000 Printer Link Speed C bs puter Center Youngberg Hall Landscape 14 Issues in Networking I Assume each customer and printer is connected using Ethernet ie at 1 Gbs I How fast does the link between Youngberg and the computer center have to be to guarantee all the customers can use the 1Gbs I C55Gbs I Too expensive Landscape 15 Issues in Networking I Solution Gamble I Assume gt Each host computer breaks up messages into smallish units called packets gt Packets from each customer are sent to a waiting line buffer to wait their turn to use the link gt Packets arriving to a full buffer are discarded gt Discarded packets are retransmitted later I Customer information now experiences gt Delay waiting in line gt Loss Landscape 16 Issues in Networking I Customer performance requirements gt Delay lt 100ms gt Loss lt 10 I Assume customer traffic gt Average packet length 9000 bytes gt Packets are generated at a rate of 2 per second I Using basic queueing theory gt C 86 Mbs ltlt 55 Gbs gt System size gt 7 packets Landscape1 7 Issues in Networking Ping Packet Delay and Loss What happens when you lose your gamble See httpaveragemiqnet for current Internet performance data Average Ping Delay Miniseconds 8 m uamadsso1 axoed Buid BBEABAV Average Delay Average Loss From The Dark Fiber 0 0 Pradigmquot mmmmmmwwmmgmm GilderTechnologyRepori E c3 3 E T3 95 a 32 VoN02Feb1997 0823slt2 202 Landscape18 Issues in Networking Managed Distributed Resource Sharing With Quality of Service Constraints aaaaaaa pe 19 Issues in Networking Sharing Implies Resource Discovery Management and Control I Routing I Call admission controls CAC I Congestion controls I Flow controls I Management systems aaaaaaa pe 20 Issues in Networking Sharing Implies Resource Control and Management I Network provider time scale management Plane gt ent gt Provisioning Call time scale control plane gt Refer back to signaling examples Customer data time scale userdata plane gt Process information ow at rates I Control network resources at time scales ranging from 106 sec to months A full set of protocols often with components in u 1 common define a plane Landscape 21 umm Mnmgcmrnrl lannmg rumximA mu 39rmstdlu mum mm mm mm ohm mum mmmam H 01 39unnuw mm me mm m andEivacmDeswnmEammumcahamandcamvutev mm M mm mm Mmmmm m Landscape 22 Issues in Networking Protocols I Protocols are the rules algorithms that govern the interactions between network elements The process of making a telephone call is governed by a protocol refer to signaling example Modems execute this protocol automatically I Protocols must be standardized Landscape 23 Issues in Networking Protocols I Protocols are al orithms ie software sometimes ii39nplemente in hardware I Protocols must run in real time I Peer protocols must be executed at both ends of the connection ie run on geographically distributed network elements I Protocol must work with inaccurate or imperfect knowledge gt Packets are lost due to link error or traffic congestions gt Instantaneous traffic demands are unknown Landscape 24 Issues in Networking Protocols are real time distributed systems that must meet Constraints eg Quality of Service given imperfect knowledge Landscape 25 Research Networking Facilities at the University of nsas Information and Telecommunications Technology Center I 7 Fiber Terminal 25 Mbs Wireless System Syste m Network Organization and Standards 4 Victor S Frost Dan F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas email frosteecskuedu http WWW ittc ku edu Organization and Standards 1 Network Standards and Open Systems I Standards Organization Objectives I Standards Organizations I Open System Network Requirements I Layered Architecture I Goal Understand how networks are described Organization and Standards 2 Network Standards and Open Systems Need for Standards I Enable interoperability of equipment from different vendors I Facilitate the building of a large market to reduce prices Organization and Standards Network Standards and Open Systems Problems with Standards I Freezes technology I Multiple standards evolve for same system I Standards take a long time to be established I Difficult to evolve to meet rapidly changing needs I Often standards are complex I De facto standards often emerge Organization and Standards 4 Network Standards and Open Systems Obiectives for Standards I Fulfill need for standards thru gt Development gt Establishment gt Promulgation I Coordinate activity I Assure consensus I Information focal point I Mechanism for management Organization and Standards 5 Network Standards and Open Systems Standards Orqanizations I American National Standards Institute gtManufacturers gtOrganizations gtGovernment gtUsers Organization and Standards 6 Network Standards and Open Systems International Standards Organizations Internet Engineering Task Force IETF gt Request for Comment RFC Electronic Industries Association EIA gt Electronic manufacturers International Telecommunications Union ITU Formerlyz Consultative Committee International Telegraph Telephone CCITT gt National PTT s gt Scienti c organizations I IEEE I Forums eg Frame Relay and ATM gt Vendors gt Users Organizationandstandards 7 Open Systems I Standards lead to Open Systems I With open systems customers are not locked into one vendor s solution I Open systems lead to a llseamless user environment eg www Chapterz Organization and Standards 8 Network architectures and the Reference Models I Open systems are build upon a Layered Architecture of the network I Layered Architecture is the structuring of network functions I Note that a network protocols are one example of realtime distributed processing Organization and Standards 9 Network architectures and the Reference Models I Reference models provide gt A conceptual framework to characterize networks gt A mechanism to control describe the complexity of networks gt Required for open systems Organization and Standards 10 Network architectures and the Reference Models I Layered Architectures must have gt Structure gt Symmetry gt Peer protocols I Structure is the collection of related processing functions into layers Organization and Standards 11 Network architectures and the Reference Models I Symmetry requires compatible functions exist is source destination systems I Peer Protocols are the set of rules that govern the processing between peer entities ie the source destination Organization and Standards 12 Network architectures Underlying Principles I Minimize the number of layers thus simplifying the tasks of describing and integrating different layers I Establish boundaries at points where the description of services is small and the number of interactions is minimum I Create layers that include different functions Organization and Standards 13 Network architectures Underlying Principles I Establish boundaries where history demonstrates that the implementation can be partitioned I Engineer layers so that they can could be redesigned to take advantage of new technology without changing the services and interfaces of adjacent layers I Allow for the bypassing of sublayers I Each layer should add value Organization and Standards 14 Layered Architecture Source Destination Message Flow Message Flow 15 Organization and Standards 39Protocol Data Units PDU packets between Peer entities 39Service Data Units SDU packets between layers 16 Organization and Standards Layered Architecture internationai Organization for Standardization i Open Systems interconnection Modei DSi I Q S Da k ngnlmzmlimlnk 17 Physical Layer I DTE DCE interface gt Data Terminal Equipment PC gt Data Communications Equipment Modem I Electrical optics radio connections I Mechanical connections I Functional Requirements I Proceduralprotocol I Bittransmission ngnlmzmlimlnk 18 Data Link Layer I Manage the link connection I Supervise data interchange I Synchronize and delimit I Frame block sequencing I Link flow control I Link Error Control I Abnormal condition recovery I Identification and parameter exchange Organization and Standards 19 Network Layer I Routing and switching I Network connections I Logical channel control I Segmenting and blocking I Error recovery I Sequencing and ow control Organization and Standards 20 Network Layer I Guaranteed Delivery eventually I Guaranteed Delivery with delay bound I For packet ows if defined gt ln order delivery gt Guaranteed minimal data rate eg in b s gt Guaranteed minimal jitter 1 gt Security Packet Arrival jitter at dest Organization and Standards 21 Transport Layer I Mapping I Multiplexing gt Multiple sessions on one transport P1199 I Endtoend error control I Flow regulation I Manage concatenated networks Organization and Standards 22 Session Layer I Administrative services gt Binding connections gt Unbinding connections I Dialog Services gt Control data exchange gt Interaction and synchronization gt Exception reporting Organization and Standards 23 Presentation Layer I Interpretation of data I Data transformation I Data formatting I Syntax selection I Structuring of data Organization and Standards 24 Application Layer I Highest layer I Serves as window to 081 I Functions to provide all services I Comprehensible to the user e g gt Identi cation gt Availability of resources gt Authority gt Authentication gt Agreement on syntax I Layer management function egmtmmsmm 25 Layered Architecture EndtoEnd Perspective THE 051 LAY FRED ARCHITECI URE mm gt1 mm w a nu m rwmx r m r M Wm M mum ummwrtmmmuwm 26 Layered Architecture Application Presentation Sessi on Transport Network Data Link Physical Network Il Application Presentation Session Network Transport Network Data Link rm ximi Physical Organization and Standards 27 Layering logical communication Eg transport a ica rion trans art I take data from app quot8 r I add addressing link reliability check h sical info to form network quotdatagramquot aEElica rion 0 link I send datagram to M O 5 all network Peer link I wait for eer to ack l I receipt P phys39cal a 1110quot lica on SJOf T tron art I analogy post of ce work Q nefwor n lt link 5 col h sical 28 A T l r 2nd edition Iim Kurose Keith Ross Addisoanesley luly 2002 Organization and Standards Layering thsical communication data 39 Cl aEElica rion transEort O networ ink physical 39r r 2nd edition Iim Kumse Keith Ross Addisoanesley Iuly 2002 Protocol layerinq and data Each layer takes data from above I adds header information to create new data unit I passes new data unit to layer below source destination message segment datag r am frame r T Organization and Standards 30 2nd edmon Tim Km K an re Addisoanesley Iuly 2002 outer Network El Physical layer eritit39 393 Network layer entity Network la er entit Data link layer entity y y Transport layer entity 31 Mudi ed rmm Leuanarna amp Wldjaja Commumcmlon Narwoyk Organization and Standards Encapsulation TCP Header contains source amp destination HTTP Request port numbers lP Header contains 3 source and destination TCP IP addresses header HTTP ReqUBSt transport protocol type Ethernet Header contains 3 source amp destination MAC 3 TCP addresses39 HTTP RequeSt network protocol type 3 Ethernet IP TCP l header header header HTTP ReqUBSt l o Organization and Standards Example of Encapsulation IP over SONET over WDMPaoket over SONET HTTP Request Header Contains source and desunauon port numbers Header contains source and destination IP addresses Heade transportprotocol type HZDLC framing l HDLCI l HDLC l r t A datagams SONET OH Organization and Standards 33 Layered Architecture I Presentation What does the peer look like I Sessions Who is the Peer I Transport Where is the Peer I Network What is the route to the peer I Link How is each step along the rout taken I Physical How is the transmission medium used Organization and Standards 34 Layered Architecture TCPIP 39Cl ll Orgamzahan and Standards 35 Layered Architecture TCPIP I Physical layer is same as in 081 I Network Layer gt Interaction between endesysterns and network gt Source provides destination address through network layer gt Makes higher layer software independent of underlying networking technology Orgamzahan and Standards 36 Layered Architecture TCPIP I Internet Layer gtRouting between networks gtIrnplernented in end systems gtIrnplernented in routers gtInternet Protocol IP Orgamzanon and Standards 37 Layered Architecture TCPIP I Transport Layer gtReliable endto end transport Transport Control Protocol TCP gtUser datagram protocol UDP gtOthers eg Real Time Protocol RTP Orgamzanon and Standards 38 Layered Architecture TCPIP I Application Layer gtftp gtte1net gtMa1391 gtWWW OWN mm 39 Example Protocol Stack Universal Mobile Telecommunications System UMTS Protocol Architecture User Plane I I I I I I I l I I I I l I I I I I I I I IIIIII Irma um mus nun FF Framing Prulucul GTPVUGPR5 Tunneling PqucuiUser PDCP Pack2tbamcunv2rgence Pramch OWN mm 40 Example Protocol Stack High Speed Data Packet Access HSDPA w Nclwork or mg 3 1w 46mm 1 saw emu Hml ember 39 r 39 H39 used 39 4 within the GPkS core network and between the Radio Access Network and the core network Frum Mohamed Assaad Zegh ache DJamcH TCP Performance Over UMTSVHSDPA S rems CRC Press 2007 05 an mums 41 Layered Architecture OSI and TQPIP Applicalion Application l lutlon Um Space Session Suflware Transport Transport hostlahosl Internet Network rmware Nclwur DaluLink Acme Hardware quotPm39mk smem Husreal Physical From HtghrSpeed Networks Orgmuahan mdstandards 42 W 1 Network and Transport Protocols 11 Victor 8 Frost Dan F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas 2335 Irving Hill Dr Lawrence Kansas 66045 Phone 785 864 4833 FAgtlt785 864 7789 ernail frosteecs u e u httpwwwittckuedu Chapter 8 Network Layer 1 Outline I Principles behind Internet protocols I IP gt Addressing gt Forwarding gt Routing I Examples of Transport Protocols gt TCP gt UDP I MPLS Section 105 Network Layer 2 Internetworking TCPIP I Born out of the ARPA net in the late 1960 s I 1P 9 Internet Protocol I Transport Protocols gt TCP 9 Transmission Control Protocol gt UDP 9 User Datagram Protocol I Open standard runs on PDA s Cell Phones PCs to supercomputers and others 3 Network Layer Internetworking TCPIP Internet Architecture I Application eg FTP Telnet email Simple Mail Transfer Protocol SMTP I Service Provider endtoend communications TCP UDP or other I Internetwork functions to connect networks and gateways into a total system IP I Subnetwork eg ARPANET Ethernet ATM Frame Relay Wireless others 4 Network Layer Internetworking TCPHP Host A Host B Application GatewayRouter Application Transport TCP NetWOTkUP Transport TCP Network 1P PathPhysical Network 113 PathPhysical PathPhysical Network Layer 5 Internetworking TCPIP I Application 1 Application 2 I I Application 3 TCP UDP Host Network Layer Internet Design Principles I Make sure it works gt Do prototypes gt Do not wait until standard documents are completed Keep it Simple Make clear choices avoid multiple ways of accomplishing the same thing Exploit Modularity 9 protocol layers Expect Heterogeneity gt Hardware gt OSs gt Transmission facilities gt Applications From Computer Networks 4rd Edition A S nn Tanenbaum T venh T T u Network Layer 7 Internet Design Principles I Avoid static o tions and parameters best to negotiate or a apt I Look for good design not optimum I Be strict when sending and tolerant when rece1V1ng I Scalability gt users gt Geographic scope gt Transmission speeds I Consider performance and cost Network Layer 8 IP Hourglass Architecture Host Access From Steve Deering 9 h www L 4 t pdf NetworkLayer IP Hourglass Architecture I Why an internet layer gt make a bigger network gt global addressing gt Virtualize network to isolate endtoend protocols from network details changes I Why a single internet protocol gt maximize interoperability gt minimize number of service interfaces I Why a narrow internet protocol gt assumes least common network functionality to maximize number of usable networks From Steve Deering hw www L 4 t pdf NetworkLayer Attributes of the IP Hourglass Architecture I dynamic routing I unique addresses I stable addresses I connectionless service I alwayson service I peertopeer communication model I application independence core does not know about specific applications From Steve Deering httpwww39 L Amieum Network Layer Problems with IP architecture End host assumptions gt Not mobile gt Address Binding 9 Coupling between IP address and end host Security gt Assumed friendly environment but adversarial Economic model gt Original architecture did not have an economic mode 9 Causes intercarrier problems with providing QoS Narrow hourglass model prevents applications awareness new applications placing demands for core functionality I These are currently addressed Via point solutions 12 Network Layer Internetworking IP IP is connectionless I No call set up I PDU s may be lost I Hides the subnet technology from the application to allow the use of many different subnet technologies 13 Network Layer Internetworking IPv4 IP packet header a cw Version IHL Type of service Totallength D M F F Time to hve Protocol Header checksum Identification Fragment offset Source address Destination address T Options 0 or more words T If no options then routers use fast pathquot through hardware From ComputamprN2tworks 3rd Edition AS Ngtwork Lay 14 Tamnbaum man Hall1996 Internetworking IP IP packet headerIPv4 I Version enable transition between different versions of IP datagrams I IHL Number of 32 bit words in the header I ToS Type of Service enables the use of priority queuing basis for IP DiffServ I Maximum length of IP datagram including header 65535 bytes I TIL field decremented at each hop if 0 then drop packet I Header Checksum verifies header only 15 Network Layer Header Checksum I 1P header uses check bits to detect errors in the header I A checksum is calculated for header contents I Checksum recalculated at every router so algorithm selected for ease of implementation in software I Let header consist of L 16bit words b0 b1 b2 bL1 I The algorithm appends a 16bit checksum bL 16 Network Layer Checksum Calculation The checlltsum bL is calculated as follows I Treating each 16bit word as an integer find x b0 b1 b2 erl modulo 2151 I The checlltsum is then given by bL x modulo 2151 I This is the 16bit 1 s complement sum of the Us I If checlltsum is 0 use all 1 s representation all zeros reserved to indicate checlltsum was not calculated I Thus the headers must sutis thefollowing pattern 0 b0 b1 b2 bL71 bL modulo 2151 Frum Cummumcauun Netwurks 1 7 Fundamentals Cuntepts and Key Amhitecmres Network Layer mm ipnnram amt Wtdjaja Differentiated Services Concept IP DiffServ I Provide scalable service discrimination in the Internet I No need to maintain per flow state or doing per hop signaling I Employs a small set of building blocks from which a variety of services can be built I These services can be either endtoend or intra domain 18 Network Layer Differentiated Services Concept I Differentiated Services provide a wide range of services through gt Setting bits in the ToS at network edges and administrative boundaries gt Using those bits to determine how packets are treated Queued by the routers inside the network and gt Conditioning the marked packets at network boundaries in accordance with the requirements of each service 19 Network Layer Internetworking IP Services I Fragmentation and reassembly gtIf PDU size gt MTUMaximum Transfer Unit for subnet the IP must fragment the PDU and reassemble at the destination ATM AAL 5 64 K PDU39s Ethernet 1500 byte PDU39s 20 Network Layer Internetworking IP Addressing Every M and router interface has an IP address 32 bitsaddress 4295x109 addresses IPv4 128 bitsaddress 34x1034 addresses IPv6 Addresses contains gt Host ID 7 Identi es a unique host on a network gt Networ r Identi es the network that the host is connected to gt Initially five formats for IP addresses Classfull IP Addressing NeLid Netid Hostid 21 NetwarkLayer Internetworking Classfull IP Addressing itHiHiiHMiHitHM i i i i inangeofhos 0235 A 0 Network Host 29222555255 B i 10 Network Host 13255222255 c i 110 Network Host lgg39o 39oqti a D i 1110 Mullicasl address Egg0amp0 a E 1111B Reserved lorfuture use 24325052205255 mm CamputerNetwarks 3m Edman A s NEkaLayE 22 T anenbaum Prentite H 5111996 Internetworking Classfull IP Addressing I Class A addresses gt 127 Class A addresses gt 224 hosts1677 MillionClass A addresses I Class B networks gt 16383 Class B addresses address 0 is reserved gt 216 65K hostsaddresses KU has a class B address I Class C addresses gt 2097152 Class C addresses 0 and 2907151 reserved 256 hosts network I Class D is used for multicasting 23 Network Layer Internetworking IP Addressing Notation I 32 bits 4 bytes I Represent each byte by a decimal I Example 11553184 gt 00001011 00110111 00011111 1010100 gt 11 55 31 84 gt This is a Class A address 0001011 is the network address 00110111 000111111010100 is the host address 24 Network Layer Network Address Host Address bit I 31 I IUIU1UUEI1 UEIEIEHEIHJ J EIIII1IIJ31EI UEIEIEIEIEIH 145 a H 34 H Hh ff 14510343 Class B Address From UnderstandingIP Addressing Eva39yt hing Yo Internetworking Classfull IP Addressing Notation Network Layer 25 By chuck Sanena http www Ev er Wanted To Know Internetworking Classfull IP Addressing Notation I D cttedD ecim 3 Notation Fish gas 1 ttr39nugh 12Emmxolt Address Class AHB prefix es B HE pre xes 1280mmxthrnugh 151255gtooltmlt C 24 pre xes 1520 mtrruugh 223255255300 The quotXXXquot represents the hostnumber field of the address which is assigned by the local network administrator From Understanding 1 Addressing Ev aything You Network Layer 26 Ever Wanted To Know By Chuck Sanena http www Internetworking Classfull IP Addressing I Identification of Class gt Class A 1 126 Network Uh L to 0 and a severbit network number followed by a 24bit host number gt Class B 128 191 e 16 Pre xes ee Each Class B network address has a RAM networkpr 39 wi e two highest order bits set to 10 and a 11quot I flluabya11391 gt Class C 192 223 e 24 e Pre xes Each Class 3 network address has a 24bit networkpre x with the three highest order his set to 110 and a 01 r r r r Network Layer 27 First Octet Rule Class A g 1 1 27 Class B a 128191 Class c 192223 Class D 224239 Class E 240255 28 Network Layer Internetworking Subnetting Subnetting divides the standard Classful host number into Subnet number Host number TunI nal Chasm limb I NetworkPre x I HurstN Lm her i Tnmm auhnet Himhr A k l NetwwkPre x l SubmitNumber l HustNunherl Enables routing 0n subnet number for more efficient routing Provides an additional level of addressing hierarchy From Understanding 1P Addressmg Ev aythmg You Network Layer 29 Ever Wanted To Know By Chuck Semena http www Internetworking Subnetting Netid Subnetid Hostid Special addresses Netid All 1 s 9 broadcast address send to all on netid Netid All 0 s 9 network address 30 Network Layer Internetworking Subnetting To identify the Subnet the muter uses a subnet mask Subnet mask has a 1 in each bit position of the address except the host I39D quotWWW 3 m 3 525 22 2222555 m 5 5 25 mm mm mm mum 555555 552 255 255 255 n nnnn nnnn nnnn 55mm 2225 2 2 7 dex m 5 5 25 mmmo nnmm nannmm nnannm Log ca AND 255 255 255 u nmxn nnnn nmm mama network pre x m 5 5 25m monnmn nnnnmm amman nnnnnm 24 21 Extended nexmkprenx 31 quot2522525 Internetworklng Subnettlng 19311124 Z7 32 quot2522525 Internetworking CIDR I Classless Interdomian Routing CIDR I Removes the classful address restriction I Extends the concept of subnetting to routers inside the Internet I Partially relieves address exhaustion allows more efficient use of IPv4 address space I Supports deployment of arbitrarily sized networks I Aggregation allows reduction in the size of routing tables 33 Possible Subnet Mask Values 1212612512412312212120 0 0 0 0 0 0 0 123 1 0 0 0 0 0 0 192 1 1 0 0 0 0 0 224 1 1 1 0 0 0 0 240 1 1 1 1 0 0 0 24a 1 1 1 1 1 o 0 252 1 1 1 1 1 1 0 254 1 1 1 1 1 1 1 255 Technuluu Easmsvzt udf NetworkLayer 34 Internetworkin CIDR 1 meme Anamm cm WNW DnlledDemmal n 3 xx hosts 255 5n C 25 of 125 255255 255 92 4 subnets 127 255255 25522 Internetworking IP Addressmg Domam Name Semee DNS 7 Names gt IF translauon I NonenumeIjc 01m for IP addresses host amin n gt hastd pmmenunshmhan damam I Names are long and human understandable gt Wastesspacetucarrythemm packetlwe a gt Hardtu parse I Numenc addresses are shorter and maclune understandable gt I xed me easytu carry m headers and parse 36
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