Quality of Service Outline Realtime Applications Integrated Services Differentiated Services 1 Realtime Applications Require deliver on time assurances must come from inside the network Microphone Sampler A D converter Buffer D A Speaker Example application audio sample voice once every 125us each sample has a playback time packets experience variable delay in network add constant factor to playback time playback point 2 Playback Buffer Sequence number Packet arrival Packet generation Playback Network delay Buffer Time 3 Example Distribution of Delays 90 97 98 Packets 3 99 2 1 50 100 150 200 Delay milliseconds 4 Taxonomy Applications Real time Tolerant Adaptive Delayadaptive Nonadaptive Elastic Intolerant Rate adaptive Interactive Interactive Asynchronous bulk Nonadaptive Rateadaptive 5 Integrated Services Service Classes guaranteed controlled load Mechanisms signalling protocol admission control policing packet scheduling 6 Flowspec Rspec describes service requested from network controlled load none guaranteed delay target Tspec describes flow s traffic characteristics average bandwidth burstiness token bucket filter token rate r bucket depth B must have a token to send a byte must have n tokens to send n bytes start with no tokens accumulate tokens at rate of r per second can accumulate no more than B tokens 7 Per Router Mechanisms Admission Control decide if a new flow can be supported answer depends on service class not the same as policing Packet Processing classification associate each packet with the appropriate reservation scheduling manage queues so each packet receives the requested service 8 Reservation Protocol Called signaling in ATM Proposed Internet standard RSVP Consistent with robustness of today s connectionless model Uses soft state refresh periodically Designed to support multicast Receiver oriented Two messages PATH and RESV Source transmits PATH messages every 30 seconds Destination responds with RESV message Merge requirements in case of multicast Can specify number of speakers 9 RSVP Example Sender 1 PATH R Sender 2 R PATH RESV merged R RESV R R Receiver A RESV Receiver B 10 RSVP versus ATM Q 2931 RSVP receiver generates reservation soft state refresh timeout separate from route establishment QoS can change dynamically receiver heterogeneity ATM sender generates connection request hard state explicit delete concurrent with route establishment QoS is static for life of connection uniform QoS to all receivers 11 Differentiated Services Problem with IntServ scalability Idea support two classes of packets premium best effort Mechanisms packets in and out bit edge routers tag packets core routers RIO RED with In and Out P drop 1 0 MaxP AvgLen Min out Min in Max out Maxin 12