Mobile and Wireless Networking

1. Mobile and Wireless Networking Lecture 19Dr. Xinbing Wang

2. 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

3. 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

4. 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 Zonethat contains the Expected Zone and location of the sender node Dr. Xinbing Wang

5. 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

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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. Architecture Application Layer Network Layer MAC Layer 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

17. 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

18. SWAN Architecture Source: [2] Dr. Xinbing Wang

19. 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

20. 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

21. 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

22. 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

23. 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

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

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

26. 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

27. 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

28. 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

29. 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

30. 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