Introduction to Wireless Ad-Hoc Networks Routing

1. Introduction to Wireless Ad-Hoc Networks Routing Michalis Faloutsos Some slides borrowed From Guor-Huar Lu

2. Outline • Challenges • Design Goals Specified by MANET (for now…) • Types of Routing • Protocols in Detail • Conclusion

3. Challenges • Dynamic Topologies • Bandwidth-constrained, variable capacity links • Energy-constrained • Limited Physical security • Scalability

4. Types of routing • Flat Proactive Routing • Link state: Fish-Eye Routing, GSR, OLSR. • Table driven: Destination-Sequenced Distance Vector (DSDV), WRP) • On-Demand or Reactive Routing • Ad hoc On-demand Distant Vector (AODV) • Dynamic Source Routing (DSR) • Hybrid Schemes • Zone Routing ZRP, SHARP (proactive near, reactive long distance) • Safari (reactive near, proactive long distance) • Geographical Routing • Hierarchical: One or many levels of hierarchy • Routing with dynamic address • Dynamic Address RouTing (DART), L+

5. Proactive Protocols • Proactive: maintain routing information independently of need for communication • Update messages send throughout the network periodically or when network topology changes. • Low latency, suitable for real-time traffic • Bandwidth might get wasted due to periodic updates • They maintain O(N) state per node, N = #nodes

6. On-Demand or Reactive Routing • Reactive: discover route only when you need it • Saves energy and bandwidth during inactivity • Can be bursty -> congestion during high activity • Significant delay might occur as a result of route discovery • Good for light loads, collapse in large loads

7. Hybrid Routing • Proactive for neighborhood, Reactive for far away (Zone Routing Protocol) • Proactive for long distance, Reactive for neighborhood (Safari) • Attempts to strike balance between the two

8. Hierarchical Routing • Nodes are organized in clusters • Cluster head “controls” cluster • Trade off • Overhead and confusion for leader election • Scalability: intra-cluster vs intercluster • One or Multiple levels of hierarchy

9. The effect of hierarchy • Consider a protocol of f(N) complexity • If we apply it in a two level hierarchy with C clusters • Complexity within clusters f(Nc) • Complexity between clusters f(N/Nc) • How should we pick cluster sizes? • Does a two-level hierarchy work?

10. Geographical Routing • Nodes know their geo coordinates (GPS) • Route to move packet closer to end point • Protocols DREAM, GPSR, LAR • Propagate geo info by flooding (decrease frequency for long distances)

11. Geographical Routing • Knowing GPS coordinates • Pick next hope based on angle of deviation • Consider other params • Distance of next hop • Congestion • Reliability • Q: How do you know location of destination? destination source

12. Dynamic Routing: a new approach • DART Ericsson et al., L+ Morris et al • Goal: can we enforce address aggregation • But: nodes are moving • Then: address should change

13. Dynamic Routing: general idea • Separation of identity and address • Identity is who you are • Address is where you are • Rule for enforcing “structure” in addresses: • near by nodes should have nearby addresses • Using the Rule, we can “aggregate” information

14. DART: in more detail • Basic idea: permanent nodeID =/= transient address • The address reflects network location • It is a proactive routing scheme, distance vector • Consequences: • Routing is simplified: address tell me where you are • Nodes with similar addresses are “near” each other • Challenges: • Address allocation: When I move, change my address • ID to Address mapping: Given an ID, find the address

15. Some more theoretical issues

16. Network Capacity • The optimal capacity of a wireless network is • Where N nodes, and C channel capacity • Gupta Kumar paper “The capacity of wireless networks” • What other assumptions do I need? • Transmission range: as small as I need to • Who talks to whom? Random selection Non optimal traffic patterns and fixed transmissions then throughput is : O(C/ sqrt(N log N))

17. Intuitive Explanation • Explanation: N nodes in the field • Destinations are random • On average N^0.5 hops per path • Each node has N^0.5 paths go through

18. Mobility increases capacity • Grossglausser and Tse (infocom 2001) • Statement: if nodes move they will eventually carry the info where you want • Protocol: • sender send one copy to receiver or one neighbor • Sender and relay will at some run into destination and send the packet • All paths are at most two hops • They show that the capacity of the network does not go to zero • Tradeoff?

19. Hierarchical routing: bounds • Cluster nodes, and route between and within clusters • Location management: finding where is the node • Routing finding how to get there • Multiple levels: log(N) levels • Location Mgm: Each nodes stores O(N) locations • Routing overhead: O(log^3N) • Dominating factor: location management and not the routing • Location mgmt handoff: O(log^2N) • See Susec Marsic, infocom 02

21. Types of routing • Flat Proactive Routing • Link state Fish-Eye Routing, GSR, OLSR. • Table driven: Destination-Sequenced Distance Vector (DSDV), WRP) • On-Demand or Reactive Routing • Ad hoc On-demand Distant Vector (AODV) • Dynamic Source Routing (DSR) • Hybrid Schemes • Zone Routing ZRP, SHARP (proactive near, reactive long distance) • Safari (reactive near, proactive long distance) • Geographical Routing • Hierarchical: One or many levels of hierarchy • Routing with dynamic address • Dynamic Address RouTing (DART)

22. Proactive: DSDV - Destination-Sequenced Distance Vector Algorithm • By Perkins and Bhagvat • Based on Bellman Ford algorithm • Exchange of routing tables • Routing table: the way to the destination, cost • Every node knows “where” everybody else is • Thus routing table O(N) • Each node advertises its position • Sequence number to avoid loops • Maintain fresh routes

23. DSDV details • Routes are broadcasted from the “receiver” • Nodes announce their presence: advertisements • Each broadcast has • Destination address: originator • No of hops • Sequence number of broadcast • The route with the most recent sequence is used

24. Reactive: Ad-Hoc On-demand Distance Vector Routing (AODV) • By Perkins and Royer • Sender tries to find destination: • broadcasts a Route Request Packet (RREQ). • Nodes maintain route cache and use destination sequence number for each route entry • State is installed at nodes per destination • Does nothing when connection between end points is still valid • When route fails • Local recovery • Sender repeats a Route Discovery

25. Route Discovery in AODV 1 Propagation of Route Request (RREQ) packet

26. Route Discovery in AODV 2 Path taken by Route Reply (RREP) packet

27. In case of broken links… • Node monitors the link status of next hop in active routes • Route Error packets (RERR) is used to notify other nodes if link is broken • Nodes remove corresponding route entry after hearing RERR

28. Dynamic Source Routing (DSR) • Two mechanisms: Route Maintenance and Route Discovery • Route Discovery mechanism is similar to the one in AODV but with source routing instead • Nodes maintain route caches • Entries in route caches are updated as nodes learn new routes. • Packet send carries complete, ordered list of nodes through which packet will pass

29. When Sending Packets • Sender checks its route cache, if route exists, sender constructs a source route in the packet’s header • If route expires or does not exist, sender initiates the Route Discovery Mechanism

30. Route Discovery 1 (DSR) Building Record Route during Route Discovery

31. Route Discovery 2 (DSR) Propagation of Route Reply with the Route Record

32. Route Maintenance • Two types of packets used: Route Error Packet and Acknowledgement • If transmission error is detected at data link layer, Route Error Packet is generated and send to the original sender of the packet. • The node removes the hop is error from its route cache when a Route Error packet is received • ACKs are used to verify the correction of the route links • Nodes use caching: to reduce overhead.

33. The Zone Routing Protocol (ZRP) • Hybrid Scheme • Proactively maintains routes within a local region (routing zone) • Also a globally reactive route query/reply mechanism available • Consists of 3 separate protocols • Protocols patented by Cornell University!

34. Intrazone Routing Protocol • Intrazone Routing Protocol (IARP) used to proactively maintain routes in the zone. • Each node maintains its own routing zone • Neighbors are discovered by either MAC protocols or Neighbor Discovery Protocol (NDP) • When global search is needed, route queries are guided by IARP via bordercasting

35. Interzone Routing Protocol • Adapts existing reactive routing protocols • Route Query packet uniquely identified by source’s address and request number. • Query relayed to a subset of neighbors by the bordercast algorithm

36. Comparisons 1 • Things in common: • IP based operation • Distributed operation • Loop-free routing • Very little or no support for sleep period operation and security

37. Comparisons 2 DSDV

38. Performance? • End-to-end data throughput and delay • Route acquisition time • Percentage of out-of-order delivery • Efficiency: • Average number of data bits transmitted/data bits delivered • Average number of control bits transmitted/data bits delivered • Average number of control and data packets transmitted/data packet delivered

39. Parameters • Network Size • Channel properties • Connectivity (average degree of a node) • Topology rate of change • Link capacity (bps) • Directionality: Fraction of unidirectional links • Traffic patterns: who talks to whom • Mobility • Fraction/frequency of sleeping nodes

40. References • Mobile Ad hoc Networking (MANET): Routing Protocol Performance Issues and Evalution Considerations (RFC 2501) • P. Misra., “Routing Protocols for Ad Hoc Mobile Wireless Networks”, http://www.cis.ohio-state.edu/~jain/cis788-99/adhoc_routing/ • The Zone Routing Protocol (ZRP) for Ad Hoc Networks <draft-ietf-manet-zone-zrp-04.txt> • Fisheye State Routing Protocol (FSR) for Ad Hoc Networks <draft-ietf-manet-fsr-03.txt> • Ad hoc On-demand Distance Vector (AODV) Routing <draft-ietf-manet-aodv-11.txt> • The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks (DSR) <draft-ietf-manet-dsr-07.txt>

41. Conclusion • On-demand routing protocols (AODV and DSR) are well established. • More analysis and features are needed (Performance comparison between protocols, QoS extension and analysis, multicast, security issues etc…) • Good paper (though old): A review of current routing protocols for ad-hoc mobile wireless networks, E. Royer, C.K. Toh Routing Scalability in MANETs, Eriksson et al. Book chapter, http://www.cs.ucr.edu/~michalis/COURSES/240-08/lectures/bookchapter.pdf

43. Fisheye State Routing (FSR) • Node stores the Link State for every destination in the network • Node periodically broadcast update messages to its neighbors • Updates correspond to closer nodes propagate more frequently

44. Multi-Level Scope (FSR) • Central node (red dot) has the most accurate information about nodes in white area and so on. • Parameters: Scope level/radius size

45. ZPR architecture

46. Design Goals • Peer-to-peer mobile routing capability in mobile, wireless domain. • Intra-domain unicast routing protocol: • Effective operation over a wide range of mobile networking scenarios and environments • Supports traditional, connectionless IP services • Efficiently manages topologies changes and traffic demands

47. Desired properties • Distributed operation • Loop freedom • Demand-based operation • Proactive operation • Security • “Sleep” period operation • Unidirectional link support