Tema 5.- Redes inalámbricas Ad Hoc. Quality of Service (QoS)

1. Tema 5.- Redes inalámbricas Ad Hoc. Quality of Service (QoS) Introducción QoS in IP based Networks QoS in MANETs Propuestas del Grupo GRC Arquitectura DACME

2. Introduction • The evolution of the Multimedia Technology and the Commercial Interest of Companies to reach civilian applications have made QoS in MANETs an unavoidable task. • QoS and Overhead are synonyms !. The idea of providing QoS in MANETs is not to extinct Overhead but to keep it as low as possible. • MANETs : 3 new problems! • Dynamic Topology. • Bandwidth Constrains. • Limited Processing & Storing capabilities of Devices. • What happens with QoS in Wire-based Networks?. Can we port ideas / protocols to MANETs? A Glance At QoS in Mobile Ad-Hoc Networks:http:/www.cs.ucr.edu/~csyiazti/cs260.html

3. The QoS Metrics How do we measure the QoS ? • Some mostly used QoS attributes • Available Bandwidth • Probability of packet loss • Delay variance (jitter, unpredictable delay) • end-to-end delay (Accumulation of jitter along the path) • Power consumption or battery charge • Service coverage area • QoS Metrics can be defined in terms of one of the parameters or a set of parameters in varied proportions

4. QoS Definition • QoS definition • “The collective effect of service performance which determines the degree of satisfaction of a user of a service”. • The United Nations Consultative Committee for International Telephony and Telegraph (CCITT) Recommendation E.800 Video frame without QoS Support Video frame with QoS Support

5. Principles for QOS Guarantees (I) • Consider a phone application at 1Mbps and an FTP application sharing a 1.5 Mbps link. • Bursts of FTP can congest the router and cause audio packets to be dropped. • Want to give priority to audio over FTP. • PRINCIPLE 1: Marking of packets is needed for router to distinguish between different classes; and new router policy to treat packets accordingly.

6. Principles for QOS Guarantees (II) • PRINCIPLE 2: provide protection (isolation) for one class from other classes. • Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed above). • Require Policing Mechanisms to ensure sources adhere to bandwidth requirements; Marking and Policing need to be done at the edges:

7. Principles for QOS Guarantees (III) • PRINCIPLE 3: While providing isolation, it is desirable to use resources as efficiently as possible. • Alternative to Marking and Policing: allocate a set portion of bandwidth to each application flow; can lead to inefficient use of bandwidth if one of the flows does not use its allocation.

8. Principles for QOS Guarantees (IV) • PRINCIPLE 4: Need a Call Admission Process; application flow declares its needs, network may block call if it cannot satisfy the needs . • Remember:Cannot support traffic beyond link capacity

9. QoS in IP Based Networks • How is QoS achieved? • “Over Provisioning”. Add plentiful capacity to the network. • Easy! (e.g. upgrade from 10Mb to 100Mb) • Can be done gradually. • But we remain at 1 service class (best effort) again. • “Network Traffic Engineering”. Make the Network more sophisticated! (e.g. Traffic Classes, Connection Admission Control, Policy Managers,…) • Reservation-based Engineering. (e.g. RSVP/IntServ, ATM) • Reservation-less Engineering. (e.g. DiffServ) • Used in today’s Differentiated Services • IPv4 TOS octect • IPv6 traffic Class octect

10. Integrated Services • Attempt to modify Internet service model to support diverse application requirements • Any data flow that desires better than best-effort delivery requests and reserves resources at routers along the path • RSVP is the recommended reservation protocol • If insufficient resources are available, the flow is denied admission into the network • Each router • Maintains reservation state for each flow • Classifies every packet and decides forwarding behavior • Monitors the flow to ensure that it does not consume more than the reserved resources • Advantages • Enables fine-grained QoS and resource guarantees • Disadvantages • Not scalable, harder to administer

11. Service Interface & Call Admission • Session must first declare its QoS requirement and characterize the traffic it will send through the network • R-spec: defines the QoS being requested by receiver (e.g., rate r) • T-spec: defines the traffic characteristics of sender (e.g., leaky bucket with rate r and buffer size b). • A signaling protocol is needed to carry the R-spec and T-spec to the routers where reservation is required; RSVP is a leading candidate for such signaling protocol. • Call Admission: routers will admit calls based on their R-spec and T-spec and base on the current resource allocated at the routers to other calls.

12. Differentiated Services • Moves admission control and flow monitoring to the edge of the network • Edge nodes classify and mark packets to receive a particular type of service • Diff Serv Code Point (DSCP) • Packet is marked in the Type of Service (TOS) in IPv4, and Traffic Class in IPv6. • Finite set of DSCPs defined • Interior nodes determine the type of service for forwarded packets based on their DSCP values • Advantages • More scalable • No per-flow state • Easier to administer • BIG ADVANTAGE: • No state info to be maintained by routers! • Disadvantages • Cannot provide the same per-flow guarantees as IntServ

13. Edge Router/Host Functions • Classification: marks packets according to classification rules to be specified. • Metering: checks whether the traffic falls within the negotiated profile. • Marking: marks traffic that falls within profile. • Conditioning: delays and then forwards, discards, or remarks other traffic.

14. QoS in MANETs • A lot of work has been done in supporting QoS in the Internet, but unfortunately none of them can be directly used in MANETs because of the bandwidth constraints and dynamic network topology of MANETs. • To support QoS, the link state information such as delay, bandwidth, cost, loss rate, and error rate in the network should be available and manageable. • However, getting and managing the link state information in MANETs is very difficult because the quality of a wireless link is apt to change with the surrounding circumstances. • The resource limitations and the mobility of hosts make things more complicated. • Hard QoS guarantee is not possible in MANETs • Adaptive QoS • Service Differentiation

15. Why QoS is Hard in Mobile Ad Hoc Network? • Dynamic Network Topology • Flow stop receiving QoS provisions due to path disconnections • New paths must be established, causing data loss and delays • Imprecise state information • Link state changes continuously • Flow states change over time • No central control for coordination • Error-Probe shared medium • Hidden terminal problem • Limited resources availability • Bandwidth, battery Life, Storage, processing capabilities • Insecure medium

16. Effects of congestion and mobility: PSNR degradation due to mobility • Bursty losses • Several consecutive frames lost (video freezed) degradation due to congestion • Random losses • More uniform distortion decay Video at 10Hz  200 seconds interval PSNR: The phrase peak signal-to-noise ratio, often abbreviated PSNR, is an engineering term for the ratio between the maximum possible power of a signal and the power of corrupting noise that affects the fidelity of its representation. The PSNR is most commonly used as a measure of quality of reconstruction in image compression

17. Effects of congestion and mobility: jitter Congestion jitter: • relatively small • frequent variations Mobility jitter: • very large peaks • occasional occurrences on route change jitter is an abrupt and unwanted variation of one or more signal characteristics

18. Main issues • The main issues to consider to achieve good quality are: • MAC level QoS: IEEE 802.11e required to differentiate from bandwidth greedy best-effort traffic • Admission control: to avoid more connections than the MANET can handle • Increase routing effectiveness: even by using layer-2 aware routing protocols such as AODV or DSR, video transmission gaps are still too large to be handled by a video codec • For video streaming • Also  H.264 codec tuning:

19. QoS in MANETs • The first QoS Model proposed in 2000 for MANETs • FQMM (Flexible QoS Model for Manet QoS Signalling) • QoS Signalling • INSIGNIA (in-band signalling) • dRSVP(dynamic RSVP) • QoS Routing • QoS enabled routing (AODV/OLSR) • CEDAR(Core-Extraction Distributed Ad-hoc Routing) • Ticket based Probing (distributed QoS routing) • QoS MAC • IEEE 802.11e • MACA/PR • (Multiple Access Collision Avoidance with Piggyback Reservation) • prioritised binary countdown (PBC) • ... and • SWAN: integrated proposal QoS in MANETs Mona Ghassemian, King’s College, September 2003

20. FQMM • FQMM is the first QoS Model proposed in 2000 for MANETs by Xiao et al. • The model can be characterized as a “hybrid” IntServ/DiffServ Model as • the highest priority is assigned per-flow provisioning. • the rest is assigned per-class provisioning. • Three types of nodes: • Ingress (transmit) • Core (forward) • Egress (receive) • The role of each nodechange according to thenode mobility • Only works with TCP traffic Mona Ghassemian, King’s College, September 2003

21. QoS Signalling Terminology • Signaling is used to reserve and release resources. • Prerequisites of QoS Signalling • Reliable transfer of signals between routers • Correct Interpretation and activation of the appropriate mechanisms to handle the signal. • It means that signaling must be understandable and implemented by the rest of the nodes • Signaling can be divided into “In-band” and “Out-of-band” • In-band: integrated in data packets • Out-of-band: explicit use of control packets. Performance? • This packets should have higher priority • RSVP is an example of out-of-band signaling • Is the facto signaling protocol for IntServ • Most papers support that “In-band” Signaling is more appropriate for MANETs.

22. In-band VS Out-of Band Signaling • In-band Signaling, network control information is encapsulated in data packets • Lightweight • Not Flexible for defining new Service Classes. • Out-of-band Signaling, network control information is carried in separate packets using explicit control packets. • Heavyweight • signaling packets must have higher priority to achieve on time notification => can lead to complex systems. + Scalability. Signal packets don’t rely on data packets + We can have rich set of services, since we don’t need to “steal“ bits from data packets

23. INSIGNIA • INSIGNIA is the first signaling protocol designed solely for MANETs by Ahn et al. 1998. • Lee, S.B., Ahn, G.S., Campbell, A.T., "Improving UDP and TCP Performance in Mobile Ad Hoc Networks with INSIGNIA", June 2001, IEEE Communication Magazine. • Can be characterized as an “In-band RSVP” protocol. • It encapsulates control info in the IP Option field (called now INSIGNIA Option field). (IN-BAND) • It keeps flow state for the real time (RT) flows. (RSVP) • It is “Soft State”. The argument is that assurance that resources are released is more important than overhead that anyway exists. (RSVP) • INSIGNA tries to provide something better than best effort service for some flows, e.g., video, voice. • QoS insensitive flows can be serviced in best effort manner: e-mail • QoS sensitive flows should be treated in better than best effort manner Mona Ghassemian, King’s College, September 2003

24. INSIGNIA is just the signaling protocol of a complete QoS Architecture. To realize a complete QoS Architecture we also need many other components A Routing Protocol (e.g. DSR, AODV, TORA) to track changes of routes An Admission Control Module to allocate requests according to the requested resources A Packet Scheduling Module A Medium Access Controller Module INSIGNIA Drawbacks. Only 2 classes of services (RT) and (BE). Flow state information must be kept in mobile hosts. Georgiadis, Jacquet, and Mans proved that bandwidth reservation on ad-hoc networks is an np-hard problem [1] INSIGNIA Review [1]“Bandwidth Reservation in Multihop Wireless Networks: Complexity and Mechanisms”. ICDCSW'04, Hachioji - Tokyo, Japan, March 2004.

25. QoS in MANETs, an Integrated Vision • QoS Routing • QoS enabled routing (AODV/OLSR) • CEDAR(Core-Extraction Distributed Ad-hoc Routing) • Ticket based Probing (distributed QoS routing) • Predictive Location-Based QoS Routing Protocol • Bandwidth Routing Protocol • Trigger-Based Distributed QoS Routing Protocol • On-Demand QoS Routing Protocol • QoS-Enabled Ad Hoc On-Demand Distance Vector Routing Protocol • On-Demand Link-state Multipath QoS Routing Protocol • Asynchronous Slot Allocation Strategies • …

26. QoS Routing • Routing is an essential component for QoS. It can inform a source node of the bandwidth and QoS availability of a destination node • We know that AODV is a successful an on-demand routing protocol based on the ideas of both DSDV and DSR. • We also know that when a node in AODV desires to send a message to some destination node it initiates a Route Discovery Process (RREQ). Mona Ghassemian, King’s College, September 2003

27. QoS for AODV • QoS for AODV was proposed in 2000 by C. Perkins and E. Royer. • The main idea of making AODV QoS enabled is to add extensions to the route messages (RREQ, RREP). • A node that receives a RREQ + QoS Extension must be able to meet the service requirement in order to rebroadcast the RREQ (if not in cache). • In order to handle the QoS extensions some changes need to be on the routing tables • AODV current fields. • Destination Sequence Number, Interface, Hop Count, Next Hop, List of Precursors • AODV new fields. (4 new fields) • Maximum Delay, • Minimum Available Bandwidth, • List of Sources Requesting Delay Guarantees and • List of Sources Requesting Bandwidth Guarantees

28. QoS-Extensions of AODV: Basic Idea • QoS information is added to the RREQ packet • Intermediate nodes forward the RREQ only if they have sufficient resources to meet the QoS requirement • Resource information is updated in the RREQ by intermediate nodes • Destination sends resource information back to source in the RREP message D S RREQ RREP

29. QoS for AODV - Delay • Handling Delay with the Maximum Delay extension and the List of Sources Requesting Delay Guarantees. • RREQ includes delay • Each node has its NODE_TRANSVERSAL_TIME • Example shows how the with the Maximum Delay extension and the List of Sources Requesting Delay Guarantees are utilized during route discovery process.

30. QoS for AODV - Bandwidth • Handling Bandwidth is similar to handling Delay requests. • Actually a RREQ can include both types. • Example shows how the with the Minimum Available Bandwidth extension and the List of Sources Requesting Bandwidth Guarantees are utilized during route discovery process.

31. QoS for AODV - Loosing QoS • Loosing Quality of Service Parameters if after establishment a node detects that the QoS can’t be maintained any more it originates a ICMP QOS_LOST message, to all depending nodes. == > Reason why we keep a List of Sources Requesting Delay/Bandwidth Guarantees. • Reasons for loosing QoS Parameters. • Increased Load of a node. • Why would a node take over more jobs that it can handle?

32. QoS in MANETs, an Integrated Vision • QoS MAC • IEEE 802.11e • Cluster TDMA • MACA/PR. (Multiple Access Collision Avoidance with Piggyback Reservation) • Prioritised binary countdown (PBC) • …

33. ... andSWAN: integrated proposal • Stateless Wireless Ad-hoc Networks • intermediate nodes don’t keep per-flow or aggregate state information • differentiate real-time and best-effort traffic • QoS-capable MAC not needed • AIMD algorithm (+ *  - like TCP window) • Uses feedback information (ECN – explicit congestion notification) • Principles: • Rate control: per-hop MAC delay measurements • Source-based admission control • implemented in ns-2 and Linux/AODV http://comet.ctr.columbia.edu/swan/

34. Propuestas del Grupo GRC: Arquitectura DACME • Previous proposals have strong requirements: • All terminals must be equipped with the same software and similar hardware • All terminals must perform QoS related tasks • If some of the terminals do not offer QoS support, the whole QoS framework fails or there is severe malfunctioning • None of the previous proposals has taken into consideration that: • The bandwidth reservation process is NP-hard • QoS at the MAC layer is fundamental • Multipath routing algorithms can offer important benefits • The MANET paradigm is based on user cooperation, but in most cases we can not force users to cooperate

35. Propuestas del Grupo GRC: Arquitectura DACME • Propuestas del Grupo GRC • Arquitectura DACME

36. DACME - Requirements • Only two: • All stations that have IEEE 802.11e interfaces should map the IP packet's TOS to a MAC-level Access Category (basic requirement to achieve good performance) • Sources and destinations of QoS traffic should implement DACME (Distributed Admission Control for MANET Environments)

37. DACME - Admission control • DACME makes periodic end-to-end network measurements using probes • Intermediate stations are not aware of DACME's tasks • DACME uses UDP/IP • Decisions on whether to admit, maintain or drop a QoS flow are based on DACME's periodic measurements and the QoS requirements of each specific flow

38. DACME architecture • 1. The application registers with DACME,indicating the source and destination port, the destination's IP address and the QoS requirements • 2. DACME periodically sends probes to assess available bandwidth on the path • 3. The port state is set to up or down according to current network conditions • 4. The packet filter module is responsible for enforcing accept/reject decisions, and also for changing the packet's TOS field if accepted

39. End-to-end bandwidth estimation • Is based on measurements made every 3 seconds (±0.5 s of jitter) • each probe consists of 10 back-to-back packets with the same TOS/AC as the application's packets to avoid the stolen bandwidth problem (Breslau et al., SIGCOMM 2000)

40. Performance evaluation • General simulation setup: • ns-2 discrete event simulator • Radio interfaces are IEEE 802.11g/e enabled • Scenarios are sized 1900x400 m2 and composed by 50 nodes • Radio range is of 250 meters (4 hops between nodes on average) • Nodes move according to the random way-point model at a constant speed of 5 m/s • Comparison between DSR & MDSR routing protocols • Simulation time is of 300 seconds for each experiment • DACME source/destination pairs have a DACME agent attached

41. Traffic • 4 Video sources and 3 Voice sources regulated by DACME • Video sources generate CBR traffic at 1 Mbit/s in the Video AC • Voice sources: • VoIP streams simulated using a Pareto On/Off distribution • both burst and idle time set to 500 ms • shaping factor used is 1.5, average data rate is of 100 kbit/s • Sources are turned off in the same order they were turned on • 4 background traffic sources • Traffic is negative-exponentially distributed • Variable traffic loads; load share per AC is: 50% to the Video AC, 25% to Best-effort AC, 25% to Background AC • These sources are active all the time

42. Performance in terms of throughput/losses • On average the throughput of DACME-regulated sources is much more stable (always close to the source data rate of 1 Mbit/s) • Voice sources do not generate constant data-rate traffic • In terms of packet losses we achieve very significant improvements

43. Performance in terms of end-to-end delay • In terms of average end-to-end delay, DACME allows achieving much lower values than its non-DACME counterpart

44. Routing overhead and traffic acceptance rate • In terms of routing overhead, DACME reduces it by avoiding routing collapse situations • In terms of traffic acceptance rate: • high data-rate sources (video) are more penalized

45. Conclusions and future work • We introduced a new paradigm of QoS architecture for MANETs based on distributed admission control that is able to adapt to the different constrains of MANET environments • Simulation results show that DACME: • Improves the support of multimedia applications by achieving more stable throughput, fewer packet losses and reduced end-to-end delay • Does not misbehave when combined with a multipath routing protocol (MDSR) • Promotes routing stability and efficient usage of the radio channel • In the future we plan to develop a version of DACME for the Linux operating system to deploy an IEEE 802.11e-based real-life testbed • In linux system DACME can be implemented using Iptables