Mul$media Networking #10 QoS Semester Ganjil 2012 PTIIK Universitas Brawijaya
Schedule of Class Mee$ng 1. Introduc$on 2. Applica$ons of MN 3. Requirements of MN 4. Coding and Compression 5. RTP 6. IP Mul$cast 7. IP Mul$cast (cont d) 8. Overlay Mul$cast 9. CDN: Solu$ons 10. CDN: Case Studies 11. QoS on the Internet: Constraints 12. QoS on the Internet: Solu5ons 13. Discussion 14. Summary Multmedia Networking 2
Today s Outline Network support for mul$media General QoS Differen$ated QoS Per- Connec$on Flow QoS Multmedia Networking 3
Network support for mul$media Approach Granularity Guarantee Mechanism Complex? Deployed? Making best- effort service all traffic treated equally none, or so` applica$on- layer support (CDNs & overlays) minimal everywhere Differen$ated service per class of traffic none, or so` packet marking, policing, scheduling medium some Per- connec$on QoS per source- des$na$on flow so` or hard, once is admiced packet marking, policing, scheduling; call admission high licle Multmedia Networking 4
Dimensioning best effort networks approach: deploy enough link capacity so that conges$on doesn t occur, mul$media traffic flows without delay or loss low complexity of network mechanisms (use current best effort network) high bandwidth costs challenges: network dimensioning: how much bandwidth is enough? es3ma3ng network traffic demand: needed to determine how much bandwidth is enough (for that much traffic) Multmedia Networking 5
Providing mul$ple classes of service thus far: making the best of best effort service one- size fits all service model alterna$ve: mul$ple classes of service par$$on traffic into classes network treats different classes of traffic differently (analogy: VIP service versus regular service) granularity: differen$al service among mul$ple classes, not among individual connec$ons history: ToS bits 0111 Multmedia Networking 6
Mul$ple classes of service: scenario H1 R1 R2 H3 H2 R1 output interface queue 1.5 Mbps link H4 Multmedia Networking 7
Scenario 1: mixed HTTP and VoIP example: 1Mbps VoIP, HTTP share 1.5 Mbps link. HTTP bursts can congest router, cause audio loss want to give priority to audio over HTTP R1 R2 Principle 1 packet marking needed for router to distinguish between different classes; and new router policy to treat packets accordingly Multmedia Networking 8
Principles for QOS guarantees (more) what if applica$ons misbehave (VoIP sends higher than declared rate) policing: force source adherence to bandwidth alloca$ons marking, policing at network edge 1 Mbps phone R1 R2 1.5 Mbps link packet marking and policing Principle 2 provide protec$on (isola$on) for one class from others Multmedia Networking 9
Principles for QOS guarantees (more) alloca$ng fixed (non- sharable) bandwidth to flow: inefficient use of bandwidth if flows doesn t use its alloca$on 1 Mbps phone R1 1 Mbps logical link R2 1.5 Mbps link 0.5 Mbps logical link Principle 3 while providing isola$on, it is desirable to use resources as efficiently as possible Multmedia Networking 10
Scheduling and policing mechanisms scheduling: choose next packet to send on link FIFO (first in first out) scheduling: send in order of arrival to queue real- world example? discard policy: if packet arrives to full queue: who to discard? tail drop: drop arriving packet priority: drop/remove on priority basis random: drop/remove randomly packet arrivals queue (waiting area) link (server) packet departures Multmedia Networking 11
Scheduling policies: priority priority scheduling: send highest priority queued packet mul$ple classes, with different priori$es class may depend on marking or other header info, e.g. IP source/dest, port numbers, etc. real world example? arrivals arrivals packet in service classify departures high priority queue (waiting area) 2 1 3 low priority queue (waiting area) link (server) 5 1 3 2 4 5 1 4 3 2 4 departures 5 Multmedia Networking 12
Scheduling policies: s$ll more Round Robin (RR) scheduling: mul$ple classes cyclically scan class queues, sending one complete packet from each class (if available) real world example? arrivals 2 1 3 4 5 packet in service 1 3 2 4 5 departures 1 3 3 4 5 Multmedia Networking 13
Scheduling policies: s$ll more Weighted Fair Queuing (WFQ): generalized Round Robin each class gets weighted amount of service in each cycle real- world example? Multmedia Networking 14
Policing mechanisms goal: limit traffic to not exceed declared parameters Three common- used criteria: (long term) average rate: how many pkts can be sent per unit $me (in the long run) crucial ques$on: what is the interval length: 100 packets per sec or 6000 packets per min have same average! peak rate: e.g., 6000 pkts per min (ppm) avg.; 1500 ppm peak rate (max.) burst size: max number of pkts sent consecu$vely (with no intervening idle) Multmedia Networking 15
Policing mechanisms: implementa$on token bucket: limit input to specified burst size and average rate bucket can hold b tokens tokens generated at rate r token/sec unless bucket full over interval of length t: number of packets admihed less than or equal to (r t + b) Multmedia Networking 16
Policing and QoS guarantees token bucket, WFQ combine to provide guaranteed upper bound on delay, i.e., QoS guarantee! arriving traffic token rate, r bucket size, b WFQ per-flow rate, R arriving traffic D = b/r max Multmedia Networking 17
Differen$ated services want qualita$ve service classes behaves like a wire rela$ve service dis$nc$on: Pla$num, Gold, Silver scalability: simple func$ons in network core, rela$vely complex func$ons at edge routers (or hosts) signaling, maintaining per- flow router state difficult with large number of flows don t define define service classes, provide func$onal components to build service classes Multmedia Networking 18
DiffServ architecture edge router: per-flow traffic management marks packets as in-profile and out-profile core router: per class traffic management buffering and scheduling based on marking at edge preference given to in-profile packets over out-of-profile packets Multmedia Networking 19
edge router: per-flow traffic management DiffServ architecture marks packets as in-profile and out-profile marking b r core router: per class traffic management buffering and scheduling based on marking at edge preference given to in-profile packets over out-of-profile packets Multmedia Networking 20
DiffServ architecture edge router: per-flow traffic management marks packets as in-profile and out-profile scheduling. core router: per class traffic management buffering and scheduling based on marking at edge preference given to in-profile packets over out-of-profile packets Multmedia Networking 21
Edge- router packet marking profile: pre- nego$ated rate r, bucket size b packet marking at edge based on per- flow profile rate r b user packets possible use of marking: class- based marking: packets of different classes marked differently intra- class marking: conforming por$on of flow marked differently than non- conforming one Multmedia Networking 22
Diffserv packet marking: details packet is marked in the Type of Service (TOS) in IPv4, and Traffic Class in IPv6 6 bits used for Differen$ated Service Code Point (DSCP) determine PHB that the packet will receive 2 bits currently unused DSCP unused Multmedia Networking 23
Classifica$on, condi$oning may be desirable to limit traffic injec$on rate of some class: user declares traffic profile (e.g., rate, burst size) traffic metered, shaped if non- conforming Multmedia Networking 24
Forwarding Per- hop Behavior (PHB) PHB result in a different observable (measurable) forwarding performance behavior PHB does not specify what mechanisms to use to ensure required PHB performance behavior examples: class A gets x% of outgoing link bandwidth over $me intervals of a specified length class A packets leave first before packets from class B Multmedia Networking 25
Forwarding PHB PHBs proposed: expedited forwarding: pkt departure rate of a class equals or exceeds specified rate logical link with a minimum guaranteed rate assured forwarding: 4 classes of traffic each guaranteed minimum amount of bandwidth each with three drop preference par$$ons Multmedia Networking 26
Per- connec$on QOS guarantees basic fact of life: can not support traffic demands beyond link capacity 1 Mbps phone R1 R2 1 Mbps phone 1.5 Mbps link Principle 4 call admission: flow declares its needs, network may block call (e.g., busy signal) if it cannot meet needs Multmedia Networking 27
QoS guarantee scenario resource reserva3on call setup, signaling (RSVP) traffic, QoS declara$on per- element admission control Multmedia Networking 28
QoS guarantee scenario resource reserva3on call setup, signaling (RSVP) traffic, QoS declara$on per- element admission control QoS-sensitive scheduling (e.g., WFQ) Multmedia Networking 29
QoS guarantee scenario resource reserva3on call setup, signaling (RSVP) traffic, QoS declara$on per- element admission control QoS-sensitive scheduling (e.g., WFQ) request/ reply Multmedia Networking 30