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WUSTL CSE 574S - Quality of Service (QoS) in Data Networks

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Quality of Service (QoS) in Data NetworksOverviewQuality of ServiceQoS ComponentsQoS ComponentsTraffic ShapingToken Bucket ShaperTraffic PolicingPeak Rate Policing with Leaky BucketQueuing and Scheduling for QoSATM NetworksATM Service CategoriesService Class and QoS ParametersATM QoS: IssuesIntegrated ServicesRSVPRSVP MessagesRSVP and Integrated Services: IssuesIssues (Cont)Differentiated ServicesPer-hop Behaviors (PHBs)Expedited ForwardingAssured ForwardingAssured Forwarding (Cont)Problems with DiffServDiffServ Problems (Cont)DiffServ Problems (Cont)DiffServ Problems (Cont)Multiprotocol Label Switching (MPLS)Label Switching ExampleTraffic Engineering Using MPLSIEEE 802.1D ModelEnd-to-end QoSQoS DebateComparison of QoS ApproachesRadio Spectrum ManagementCAC: Blocking vs DroppingMean Opinion Score (MOS)Voice CodecsVOIP Quality FactorsTransmission ImpairmentsTransmission Impairments (Cont)VOIP over 802.11Selective Packet MarkingSummaryReading Assignment9-1©2006 Raj JainCSE574sWashington University in St. LouisQuality of Service (QoS) Quality of Service (QoS) in Data Networksin Data NetworksRaj Jain Washington University in Saint LouisSaint Louis, MO [email protected] slides are available on-line at:http://www.cse.wustl.edu/~jain/cse574-06/9-2©2006 Raj JainCSE574sWashington University in St. LouisOverviewOverview! QoS Mechanisms! ATM QoS! Integrated services/RSVP! Differentiated Services! Multiprotocol Label Switching (MPLS)! Comparison of different QoS approaches! QoS over Wireless9-3©2006 Raj JainCSE574sWashington University in St. LouisQuality of ServiceQuality of Service! Service: Movie, Song, Telephone Call, FTP! Quality of Service: Picture quality, Color quality, sound quality, ! For network based services, service quality may depend upon:" Throughput – Min, max, average rate" Delay – Max delay, delay variation (Jitter)" Packet Loss Rate" Reliability – Links going up/down! Each layer – PHY, MAC, IP, TCP, and application - has to have mechanisms to guarantee QoS9-4©2006 Raj JainCSE574sWashington University in St. Louis14326Signaling Admission controlPolicingRoutingShapingSchedulingTraffic Monitoring and feedback97Buffer MgmtDrop PoliciesQoS ComponentsQoS Components5Classification89-5©2006 Raj JainCSE574sWashington University in St. LouisQoS ComponentsQoS Components1. Signaling: Users need to tell/negotiate their QoS requirements with the network2. Admission Control: Network can deny requests that it can not meet3. Shaping: Traffic is smoothed out so that it is easier to handle4. Policing: Ensuring that the users are sending at the rate they agreed to5. Marking/Classification: Packets are classified based on the source, destination, TCP ports (application) 6. Scheduling: Different flows get appropriate treatment7. Drop Policies: Low priority packets are dropped.8. Routing: Packets are sent over paths that can meet the QoS9. Traffic Management: Sources may be asked to reduce their rates to meet the loss rate and delay guarantees9-6©2006 Raj JainCSE574sWashington University in St. LouisTraffic ShapingTraffic Shaping! Altering the traffic characteristics of a given flow is called traffic shaping ! The source must shape its traffic prior to sending it to network so it does not violate traffic contractShaperArriving traffic with undesired characteristicsLeaving traffic with desired characteristics9-7©2006 Raj JainCSE574sWashington University in St. LouisToken Bucket ShaperToken Bucket ShaperServerShaped TrafficBucket Size KTokens arrive periodically at Average RateIncoming TrafficToken9-8©2006 Raj JainCSE574sWashington University in St. LouisTraffic PolicingTraffic Policing! Users violating the traffic contract can jeopardise theQoS of other connections! The network must protect well behaving users against such traffic violations! Policing functions are deployed at the edge (entry) of the networkPolicerArriving trafficConforming traffic admitted into networkNon-conforming traffic (dropped)9-9©2006 Raj JainCSE574sWashington University in St. LouisPeak Rate Policing with Leaky BucketPeak Rate Policing with Leaky Bucket! Enforces sustained rate and maximum burst size! Requires only one counter " counter is decremented, to a minimum of zero, at the avg rate" counter is incremented by one, to a maximum of a limiting value, for each packet arrival ! An arriving packet is non-conforming if counter is at its limitRejectedAcceptedIncomingPackets9-10©2006 Raj JainCSE574sWashington University in St. LouisQueuing and Scheduling forQueuing and Scheduling forQoSQoS! Packets from multiple flows are queued at a given transmission link! To give different QoS, multiple queues may be used. Buffer allocation, scheduling, and drop policies for each queue are set to provide different QoS…Buffer AllocationSchedulingDropPolicyClassificationIncomingPackets9-11©2006 Raj JainCSE574sWashington University in St. LouisATM NetworksATM Networks! ATM cells are fixed size: 48-byte payload + 5-byte header! IP packets can be segmented into ATM cells at entry to ATM connection and reassembled at the end! Each cell has a circuit number: Virtual Circuit Id (VCI)! Circuit number determines the cell’s queuing and forwarding! Circuits have be set up before use! Circuits are called Virtual Circuits (VCs)! Multiple VCs can be grouped in to a “virtual path” (VP)PBXPBXPBXPBX1 3 5 2 39-12©2006 Raj JainCSE574sWashington University in St. LouisATM Service CategoriesATM Service Categories! Constant Bit Rate (CBR): Throughput, delay, delay variation guaranteed! Real-Time Variable Bit Rate (rt-VBR): Average Throughput, delay, delay variation guaranteed! Non-Real-Time Variable Bit Rate (nrt-VBR): Throughput guaranteed.! Unspecified Bit Rate (UBR): No Guarantees. Best Effort.! Available Bit Rate (ABR): Minimum Throughput. Very low loss. Feedback.! Guaranteed Frame Rate (GFR): Minimum Throughput. Frame based guarantee.! ATM also has Rate shaping, Connection-Admission control (CAC), Policing, and QoS-based routing (PNNI).9-13©2006 Raj JainCSE574sWashington University in St. LouisService Class andService Class andQoSQoSParametersParametersCDV = Cell delay variationCLR = Cell Loss RateCTD = Cell Transfer DelayService Class Traffic Parameter QoS ParameterCBR PCR maxCTD, CDV, CLRrt-VBR PCR, SCR, MBS maxCTD, CDV, CLRnrt-VBR PCR, SCR, MBS CLRABR PCR, MCR CLR (network specific)UBR PCR No QoSPCR = Peak Cell RateSCR = Sustained (avg) Cell RateMCR = Minimum Cell RateMBS = Maximum Burst Size9-14©2006 Raj


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WUSTL CSE 574S - Quality of Service (QoS) in Data Networks

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