QualityofService Foreleser Carsten Griwodz Email griffifi uio no

Quality-of-Service Foreleser: Carsten Griwodz Email: griff@ifi. uio. no 10. Mai 2006 1 INF-3190: Multimedia Protocols

Quality–of–Service (Qo. S) n Quality of Service n n “Qo. S represents the set of those quantitative and qualitative characteristics of a distributed multimedia system that are necessary to achieve the required functionality of an application” Quality of Service n Characterizes the well defined, controllable behavior of a system with regard to quantitatively measurable parameters 10. Mai 2006 2 INF-3190: Multimedia Protocols

Quality–of–Service (Qo. S) n Quality of Service n n “Qo. S represents the set of those quantitative and qualitative characteristics of a distributed multimedia system that are necessary to achieve the required functionality of an application” Characterizes the well defined, controllable behavior of a system with regard to quantitatively measurable parameters Indirect definition of Qo. S n n n n Qo. S Qo. S 10. Mai 2006 requirements parameter specification mapping negotiation contract guarantee 3 INF-3190: Multimedia Protocols

Qo. S Requirements n Different applications have different requirements concerning n n n Bandwidth Delay Jitter (delay variation) Reliability (packet loss and bit error rate) … Examples n n n File transfer (ftp, email, web): high reliability Speech: bandwidth, low delay, synchronity Video: bandwidth 10. Mai 2006 4 INF-3190: Multimedia Protocols

Qo. S Requirements of Continuous Media Applications n Acceptable delay n n n Acceptable jitter n n Milliseconds at the application level Tolerable buffer size for jitter compensation Delay and jitter include retransmission, error-correction, . . . Acceptable (lack of) continuity n n n Seconds in asynchronous on-demand applications Milliseconds in synchronous interpersonal communication Streams must be displayed in sequence Streams must be displayed at acceptable, consistent quality Acceptable (lack of) synchronity n n Inter-media: different media played out at matching times Intra-media: time between successive packets must be conveyed to receiver 10. Mai 2006 5 INF-3190: Multimedia Protocols

Qo. S Requirements: Service Classification service elastic inelastic loss tolerant nonadaptive delay adaptive video conferencing videoondemand 10. Mai 2006 loss intolerant rate adaptive interactive nonadaptive v. c. with scalable video interaktive bulk ssh, telnet rate adaptive asynchronous ftp, web email original telephony, hard real-time IP telephony 7 INF-3190: Multimedia Protocols

Qo. S Parameters n n Measurable value to express one or more requirements Examples n n Error probability at connection set-up phase Throughput Transfer delay Remaining error rate n n Duration of time to disconnect n n i. e. at disconnect phase Failure probability of disconnect Security n n Error probability at data transfer With regard to “listening in” Priority Resilience n n 10. Mai 2006 Ability to work in spite of errors Against errors within the transport layer itself 8 INF-3190: Multimedia Protocols

Qo. S Mapping Qo. S requirement: 25 video frames/sec, no loss Application transport service access point network service access point 10. Mai 2006 Application Qo. S requirement: 225 kbyte/sec, lossless Qo. S requirement: 150 packets/sec, lossless 9 INF-3190: Multimedia Protocols

Qo. S Mapping n Not only one possible mapping 1 video frame/sec max delay 1 sec success prob. 8 kbyte/sec max delay 1 sec no loss 8 kbyte/sec max delay 0. 33 sec 1 retransmission 8 kbyte/sec max delay 0. 2 sec 2 retransmissions Þ Qo. S negotation § Service user and service provider negotiate a mapping 10. Mai 2006 10 INF-3190: Multimedia Protocols

Qo. S Negotiation and Guarantee n Qo. S negotation § Service user and service provider negotiate a mapping § Service user states § Qo. S requirements § Service provider proposes § Qo. S contract between § Application (on all hosts) § Network § Contract may specify conditions § A price § A traffic specification § Service user accepts contract § Service provider guarantees compliance § Service user has received a Qo. S Guarantee 10. Mai 2006 11 INF-3190: Multimedia Protocols

Qo. S Negotiation n Negotiation procedure n n n How to set up Qo. S Peer-to-peer case – all components or resources must agree Different types n Triangular n n Bilateral n n both service users allowed to change Qo. S Unilateral n 10. Mai 2006 all components (service user and service provider) allowed to change Qo. S “take it or leave it” from initiating service user 12 INF-3190: Multimedia Protocols

Qo. S Classes n Different semantics or classes of Qo. S: n max resources n determines reliability of offered service utilization of resources reserved C unused reserved B available resources reserved A time 10. Mai 2006 13 INF-3190: Multimedia Protocols

Qo. S Classes n Best effort Qo. S n system tries its best to give a good performance no Qo. S calculation (could be called no effort Qo. S) J simple – do nothing L Qo. S may be violated unreliable service n n Deterministic guaranteed Qo. S n hard bounds Qo. S calculation based on upper bounds (worst case) J Qo. S is satisfied even in the worst case high reliability n L L over-reservation of resources poor utilization and unnecessary service rejects Qo. S values may be less than calculated hard upper bound 10. Mai 2006 14 INF-3190: Multimedia Protocols

Qo. S Classes n Statistical guaranteed Qo. S n Qo. S values are statistical expressions (served with some probability) Qo. S calculation based on average (or some other statistic or stochastic value) J resource capabilities can be statistically multiplexed more granted requests L Qo. S may be temporarily violated service not always 100 % reliable n n Predictive Qo. S n n J J L L weak bounds Qo. S calculation based previous behavior of imposed workload resource capabilities can be statistically multiplexed more granted requests possibly more exact workload description (if past and actual behavior matches) Qo. S may be temporarily violated service not 100 % reliable Qo. S values may be less than calculated hard upper bound 10. Mai 2006 15 INF-3190: Multimedia Protocols

Resource Reservation n Reservations is fundamental for reliable enforcement of Qo. S guarantees n n n Per-resource data structure (information about all usage) Qo. S calculations and resource scheduling may be done based on the resource usage pattern Reservation protocols n n Negotiate desired Qo. S by transferring information about resource requirements and resource usage between the end-systems and the intermediate systems participating in the data transfer Reservation operation n calculate necessary amount of resources based on the Qo. S specifications reserve resources according to the calculation (or reject request) Resource scheduling n 10. Mai 2006 Enforce resource usage with respect to resource administration decisions 16 INF-3190: Multimedia Protocols

time Resource Management Phases Phase 1: user’s Qo. S requirements specification rejection or renegotiation admission test and calculation of Qo. S guarantees resource reservation negotiation confirmation Qo. S guarantees to user renegotiation Phase 2: data transmission Qo. S enforcement by proper scheduling monitoring and adaptation “notification” Phase 3: 10. Mai 2006 stream termination resource deallocation 17 reflection renegotiation termination INF-3190: Multimedia Protocols