Muhammad Mateen Yaqoob Department of Computer Science COMSATS Institute of Information Technology, Abbottabad 1

 As broadband networking technology has dramatically increased the capacity of packet-switched networks  Every applications have diverse QoS requirements  QoS depends on the statistical nature of traffic  An appropriate service model should be defined  QoS control methods should be engineered to meet a range of QoS performance requirements 2

 Two main traffic types  delay-sensitive traffic (characterized by rate and duration and may need real-time transmission)  loss-sensitive traffic (characterized by the amount of information transmitted)  Other traffic types  Such as playback traffic, multicast traffic, and traffic aggregation 3

 Network has been evolving to provide QoS guarantees  ATM can reserve the bandwidth and buffer for each virtual connection  Intserv can also provide QoS for each flow in IP network  Diffserv provides different treatment for packets of different classes, instead of on a flow basis, so that it has better scalability than Intserv  MPLS allows the network providers to have better control and provision of QoS through traffic engineering policies 4

 Key QoS design and deployment best practices that can simplify and expedite QoS implementations includes;  Classification and marking principles  Policing and markdown principles  Queuing and dropping principles  DoS and worm mitigation principles  Deployment principles 5

 A number of QoS parameters can be measured and monitored to determine whether a service level offered or received is being achieved  Network availability  Bandwidth  Delay  Jitter  Loss 6

 There are also QoS performance-affecting parameters that cannot be measured but provide the traffic management mechanisms for the network routers and switches  Emission priority  Discard priority  Each of these QoS parameters affects the application’s performance or end-user’s experience 7

 If the network is unavailable then the user or application may achieve unpredictable or undesirable performance  Network availability is the collection of the availability of many items that are used to create a network  The greatest challenge for network operators today is to provide highly available IP networks 8

 It is sub-divided into two types:  Available bandwidth; amount of bandwidth (in bps) available for allocation  Subscriber competes for allocation of available bandwidth  Guaranteed bandwidth; minimum amount of bandwidth (in bps) guaranteed by network operator to be allocated for the subscriber  The service price is high 9

 Network delay is the transit time an application experiences from the access point to the exit point of the network  Delay can cause significant QoS issues with applications such as voice and video  Some applications can compensate for small amounts of delay but once a certain amount is exceeded, the QoS becomes compromised  Delay can be fixed or variable 10

 Jitter is the measure of delay variation between consecutive packets for a given traffic flow  Jitter has a pronounced effect on real-time, delay-sensitive applications such as voice and video  As arrival rate varies, jitter impacts application’s performance  A minimal amount of jitter may be acceptable but as jitter increases, the application may become unusable 11

 Loss can occur due to errors introduced by the physical transmission medium  Loss can also occur when congested network nodes drop packets  If congestion continues, network performance will significantly decrease because much of bandwidth is being used to retransmit dropped packets 12

 Emission priorities determine order in which traffic is forwarded as it exits a network node  Traffic with a higher emission priority is forwarded ahead of traffic with a lower emission priority  Emission priorities also determine amount of latency introduced to the traffic by the network node’s queuing mechanism 13

 Discard priorities are used to determine order in which traffic gets discarded  Traffic may get dropped due to network node congestion or when traffic is out-of-profile  Traffic with similar QoS performance requirements can be subdivided using discard priorities  This allows the traffic to receive the same performance when the network node is not congested 14

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