Mobile and Wireless Networking Lecture 19 Dr. Xinbing Wang

AODV: Summary Routes need not be included in packet headers Nodes maintain routing tables containing entries only for routes that are in active use At most one next-hop per destination maintained at each node DSR may maintain several routes for a single destination Sequence numbers are used to avoid old/broken routes Sequence numbers prevent formation of routing loops Unused routes expire even if topology does not change Dr. Xinbing Wang

Part 4: Other Wireless Networks Ad hoc networks Mobility and routing Flooding routing algorithm Dynamic source routing (DSR) Ad hoc On-Demand Distance Vector Routing (AODV) Location-Aided routing (LAR) Quality of Service (QoS) in ad hoc networks Sensor networks Wireless PANs Dr. Xinbing Wang

Location-Aided Routing (LAR) [Ko98Mobicom] Exploits location information to limit scope of route request flood Location information may be obtained using GPS Expected Zone is determined as a region that is expected to hold the current location of the destination Expected region determined based on potentially old location information, and knowledge of the destination’s speed Route requests limited to a Request Zone that contains the Expected Zone and location of the sender node Dr. Xinbing Wang

Expected Zone in LAR X = last known location of node D, at time t0 Y = location of node D at current time t1, unknown to node S r = (t1 - t0) * estimate of D’s speed X r Y Expected Zone Dr. Xinbing Wang

Request Zone in LAR Network Space Request Zone X r B A Y S Dr. Xinbing Wang

LAR: Route Request Only nodes within the request zone forward route requests Node A does not forward RREQ, but node B does (see previous slide) Request zone explicitly specified in the route request Each node must know its physical location to determine whether it is within the request zone Dr. Xinbing Wang

LAR: Route Discovery Only nodes within the request zone forward route requests If route discovery using the smaller request zone fails to find a route, the sender initiates another route discovery (after a timeout) using a larger request zone the larger request zone may be the entire network Rest of route discovery protocol similar to DSR Dr. Xinbing Wang

LAR Variations: Adaptive Request Zone Each node may modify the request zone included in the forwarded request Modified request zone may be determined using more recent/accurate information, and may be smaller than the original request zone B S Request zone adapted by B Request zone defined by sender S Dr. Xinbing Wang

LAR Variations: Implicit Request Zone In the previous scheme, a route request explicitly specified a request zone Alternative approach: A node X forwards a route request received from Y if node X is deemed to be closer to the expected zone as compared to Y The motivation is to attempt to bring the route request physically closer to the destination node after each forwarding Dr. Xinbing Wang

Part 4: Other Wireless Networks Ad hoc networks Mobility and routing Flooding routing algorithm Dynamic source routing (DSR) Ad hoc On-Demand Distance Vector Routing (AODV) Location-Aided routing (LAR) Quality of Service (QoS) in ad hoc networks Sensor networks Wireless PANs Dr. Xinbing Wang

Motivation Mobile ad hoc networks & QoS: Limited wireless resources: low-capacity Mobility: time-varying topology Lack of infrastructure: fully-distributed Low-capacity time-varying resources with a fully mobile infrastructure Dr. Xinbing Wang

QoS Definition in MANETs Has to be redefined ! To provide a set of parameters in order to adapt application to the quality of network while routing through the network e.g. Adaptive application, and soft QoS Parameters should represent: available resources: low-capacity stability of resources: time-varying topology Protocols should be: Adaptive: fully mobile infrastructure & low-capacity time-varying topology and resources Dr. Xinbing Wang

A Cross-Layer QoS Model A cross-layer model to deploy QoS: ALMs-- Application Layer Metrics NLMs-- Network Layer Metrics MLMs-- MAC Layer Metrics MLMs & NLMs determine the quality of links to generate paths with good quality ALMs select one path which is more likely to meet application requirements Adapt to the network quality if needed Dr. Xinbing Wang

Parameters class I, delay class II, throughput class III, B-E power level buffer level stability level link SINR At application layer At network layer At MAC layer Dr. Xinbing Wang

Architecture Application Layer Metrics Network Layer Metrics MAC App. Requirement QoS Class D T B-E Application Layer Metrics Network Quality: Stability/ Power/buffer Network Layer Metrics Link Quality: Link SINRs MAC Layer Metrics Protocol Stack QoS Extension Dr. Xinbing Wang

Example: SWAN SWAN: Service Differentiation in Stateless Wireless Ad Hoc Networks General Idea: Probe for bandwidth Admit (or not) traffic as real time at source Best Effort traffic rate controlled Violation signaled via ECN (explicit congestion notification) Design Philosophy Stateless Use existing best-effort MAC (in worst case) Distributed control Dr. Xinbing Wang

SWAN Architecture Source: [2] Dr. Xinbing Wang

Differentiated Services & ECN Fields in IP 0 1 2 3 4 5 6 7 +-----+-----+-----+-----+-----+-----+-----+-----+ | DS FIELD, DSCP | ECN FIELD | DSCP: Differentiated Services Codepoint ECN: Explicit Congestion Notification Codepoint for the best effort packets is '000000‘ Codepoint for real time MUST be assigned. Source: [1] Dr. Xinbing Wang

Bandwidth Probe Message 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- | Type | PROBE ID | Bottleneck Bandwidth | Source IP Address | Destination IP Address +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Source: [1] Type 0 (Bandwidth Probe Request) 1 (Bandwidth Probe Reply) 2 (Regulate Message with Source based Algorithm) 3 (Regulate Message with Network based Algorithm) PROBE ID Sequence number for probe Bottleneck Bandwidth Bandwidth (Kbps) along path. Updated by node if bandwidth at that node is < existing value Hop-by-hop – uses existing MANET route or initiates on-demand routing Dr. Xinbing Wang

Admission Control Solely at source nodes For Real Time flows (UDP) Uses Bandwidth Probe Each node knows real-time traffic bandwidth by eavesdropping Bavailable < Bthresh – Bcurrent Dr. Xinbing Wang

Rate Control of Best Effort Traffic Best Effort traffic is rate controlled to ensure bandwidth available for Real Time traffic and keep total below threshold Independently done at each node AIMD (Additive Increase and Multiplicative Decrease): Increase best-effort rate by C every T until Delay > D is detected (MAC Feedback) Then reduce rate R% See more parameter info in: G.-S. Ahn, A. T. Campbell, Andras Veres and Li-Hsiang Sun, "Supporting Service Differentiation for Real-Time and Best Effort Traffic in Stateless Wireless Ad Hoc Networks (SWAN)", IEEE Transactions on Mobile Computing, September 2002. Dr. Xinbing Wang

ECN Regulation of Real Time Traffic Each node monitors rt utilization When overload noted, mark ECN in real-time traffic before sending to destination Destination sends regulate message Control message causes real-time traffic to re-probe and re-admit… …Or NOT!!!! Dr. Xinbing Wang

Problem 1 – False Admission Reply1 bb=10 Probe1 10 Reply1 bb=10 Probe1 bb=10 Probe1 bb=10 Reply1 bb=10 10 10 A Reply2 bb=10 Probe2 bb=10 Probe2 bb=10 Reply2 bb=10 10 Reply2 bb=10 Probe2 R Bavailable =10 Bavailable =10 B Bavailable =0 Bavailable =0 Dr. Xinbing Wang

Problem 1 – False Admission Regulate 1 10 ECN 10 ECN 10 1 10 Regulate1, Regulate 2 Regulate1, Regulate 2 Regulate 2 D 2 Dr. Xinbing Wang

Problem 2 – How to mark ECN WHEN a violation occurs IF all flows packets marked ECN THEN all re-probe at about the same time Potential for massive, synchronized false admissions Dr. Xinbing Wang

Solutions Source-Based Regulation Algorithm All real-time packets marked ECN Source waits random time before re-probing Network-Based Regulation Algorithm DON’T mark all packets Mark a random “congested set” of sessions Mark sessions for T seconds, then pick another set Dr. Xinbing Wang

Simulation Results (ns-2) 1500m x 300m AODV 50 Nodes 2-5 hops / flow Traffic: 5x (+/-) FTP – infinite 5x (+/-) Web – pareto 4x VoIP – 32KBps CBR 4x Video – 200KBps CBR Random Waypoint (up to 72km/h) Real-time delay TCP “Goodput” Source: [3] Dr. Xinbing Wang

Questions How a MANET node connects to the Internet? How to find an Internet Gateway? What issues to concern for interworking security? QoS support for MANET and the Internet convergence. Dr. Xinbing Wang

References [1] G-S. Ahn, A. T. Campbell, A. Veres, L. Sun, "SWAN", Internet Draft, draft-ahn-swan-manet-00.txt, MANET Working Group Internet Draft, October 2002. [2] G-S. Ahn, A. T. Campbell, A. Veres, L. Sun, "Supporting Service Differentiation for Real-Time and Best Effort Traffic in Stateless Wireless Ad Hoc Networks (SWAN)," IEEE Transactions on Mobile Computing, September 2002. [3] G-S. Ahn, A. T. Campbell, A. Veres, L. Sun, "SWAN: Service Differentiation in Stateless Wireless Ad Hoc Networks," Precedings of IEEE INFOCOM '02, 2002. Dr. Xinbing Wang