Proposed ad hoc Routing Approaches

1. Proposed ad hoc Routing Approaches • Conventional wired-type schemes (global routing, proactive): • Distance Vector; Link State • Proactive ad hoc routing: • OLSR, TBRPF • On- Demand, reactive routing: • DSR (Source routing), MSR, BSR • AODV (Backward learning) • Scalable routing : • Hierarchical routing: HSR, Fisheye • OLSR + Fisheye • LANMAR (for teams/swarms) • Geo-routing: GPSR, GeRaF, etc • Motion assisted routing • Direction Forwarding

2. On-Demand Routing Protocols • Routes are established “on demand” as requested by the source • Only the active routes are maintained by each node • Channel/Memory overhead is minimized • Two leading methods for route discovery: source routing and backward learning (similar to LAN interconnection routing)

3. Existing On-Demand Protocols • Dynamic Source Routing (DSR) -- CMU • Multipath Source Routing (MSR) – TJU • Backup Source Routing (BSR) – UofO+TJU • Ad-hoc On-demand Distance Vector (AODV) • Associativity-Based Routing (ABR) • Temporarily Ordered Routing Algorithm (TORA) • Zone Routing Protocol (ZRP) • Location assisted routing (LAR, DREAM) • Signal Stability Based Adaptive Routing (SSA) • On Demand Multicast Routing Protocol (ODMRP) – UCLA

4. Dynamic Source Routing (DSR) • RFC 4728 – February 2007 • Forwarding: source route driven instead of hop-by-hop route table driven • Mobility ? • On-demand: No periodic routing update message is sent • Control traffic is minimized • The first path discovered is selected as the route • Two main phases (On-demand) • Route Discovery • Route Maintenance

5. DSR - Route Discovery • To establish a route, the source floods a Route Request message with a unique request ID • The Route Request packet “picks up” the node ID numbers • Route Reply message containing path information is sent back to the source either by • the destination, or • intermediate nodes that have a route to the destination • Each node maintains a Route Cache which records routes it has learned and overheard over time

6. DSR - Route Maintenance • Route maintenance performed only while route is in use • Monitors the validity of existing routes by passively listening to acknowledgments of data packets transmitted to neighboring nodes • acknowledgments of packets -- > contention ? (adaptive ack) • When problem detected, send Route Error packet to original sender to perform new route discovery

7. MSR - Multipath Source Routing • Direct Descendant of DSR • On-demand + Source Routing + Multipath • Probing-based adaptive load balancing among multiple paths • Motivation of MSR • Efficiently using the network resource • Alleviate the oscillation in adaptive single path routing • Fast re-routing • Reducing computing & storage requirement • Exploiting computing power of host instead of link capacity

8. MSR Implementation • To make multipath network viable • appropriate paths calculation • efficient packet forwarding on calculated paths • effective end-host usage of multiple paths • In MSR • Path Finding • Packet forwarding • Load balancing

9. Distributing Traffic among Multiple Paths • Quantities: A heuristic equation • Probing-based adaptive control • Decoupling between transport layer and network layer: SRPing • Cost effective • Scheduling: Packet Weighted Round Robin • TCP out-of-order (re-sequencing) problem

10. Distributing Traffic among Multiple Paths • Heuristic equation • Rationale: Autonomous system, homogeneous assumption, bandwidth-delay product constant where , is the delay of route with index i, is the maximum delay of all the routes to the same destination, R is a factor to control the switching frequency between routes. Uis a bound value to insure that should not to be too large.

11. Simulation Methodology • ns – Wireless extensions by CMU • Adopt methods used in [Broch98, Johnson99] • Two major files: • Movement pattern file • Communication pattern file • 50 mobile hosts placed randomly within a 1500m×300m area • Two set of simulations: Max speed 20m/s & 1m/s • Different traffic types: CBR & FTP

12. Performance Evaluation • MSR vs. DSR • Performance Metrics • Packet delivery ratio • Data throughput • End-to-end delay • Packet drop probability • Queue size

13. Simulation Results – CBR • Packet delivery ratio of every connection

14. Simulation Results – CBR • Packet delivery ratio

15. Simulation Results – CBR • End-to-end throughput

16. Simulation Results – TCP • End-to-end throughput

17. Simulation Results – CBR • End-to-end delay

18. Simulation Results – CBR • End-to-end delay

19. Simulation Results – TCP • End-to-end delay

20. Simulation Results - CBR • Packets dropped at each node

21. Simulation Results – CBR • IFQ queue size at each node

22. MSR Summary • Reduce network congestion • Improve throughput, delay, mobility, fault tolerance (CBR–more & FTP-less?) • Acceptable routing overhead? • Little more than that of DSR • Route discovery • Route maintenance • Probing (unicast) add little O/H • Good candidate for QoS support • QoS-MSR, reliable-MSR • Acceptable packet out-of-order level ? TCP

23. Backup Source Routing (BSR) • Establish and maintain backup routes that can be utilized after the primary path breaks • Define a new routing metric - backup route reliability E [T,’] (analysis) • T,’ -- the lifetime of backup route (, ') • the basis for the backup path selection • The lifetime for each link L in the network can be represented by an independent and identical (iid) exponential random variable XL Backup Route (1,2),1= (s, b, c, e, g, i, j, t) and 2=(s, a, b, c, d, f, h, i, k, t)

24. Backup Source Routing (BSR) • Reduce the frequency of route discovery flooding, which is a major overhead in on-demand protocols • Can improve the performance significantly in more challenging situations of high mobility • Testbed (QoS) at TJU • Multipath TCP with packetreplicas(UCLA) • In a lossy ad hoc wireless network

25. Ad hoc On-Demand Distance Vector Routing (AODV) RFC3561 • Primary Objectives • Provide unicast, broadcast, and multicastcapability • Initiate forward route discovery only on demand • Disseminate changes in local connectivity to those neighboring nodes likely to need the information • Characteristics • On-demand route creation • Effect of topology changes is localized • Control traffic is minimized • Distance vector routing • Two dimensional routing metric: <Seq#, HopCount> • Seq# -- to determine the freshness of the info • Storage of routes in Route Table

26. Precursor Nodes Next Hop A Destination Source Source Route Table • Fields: • Destination IP Address • Destination Sequence Number • to guarantee the loop-freedom of all routes towards that node • HopCount • Next Hop IP Address • Precursor Nodes • Expiration Time • Each time a route entry is used to transmit data, the expiration time is updated to • current_time + active_route_timeout

27. Unicast Route Discovery • Source broadcasts Route Request (RREQ) • <Flags, Bcast_ID, HopCnt, • Src_Addr, Src_Seq#, • Dst_Addr, Dst_Seq#> • Node can reply to RREQ if • It is the destination, or • It has a “fresh enough” • route to the destination • Otherwise it rebroadcasts • the request • Nodes create reverse route entry • Record Src IP Addr / Broadcast ID to prevent multiple rebroadcasts Source Destination Route Request Propagation

28. Source Destination Forward Path Setup • Destination, or intermediate node with current route to destination, unicasts Route Reply (RREP) to source • <Flags, HopCnt, Dst_Addr, Dst_Seq#, Src_Addr, Lifetime> • Nodes along path createforward route • Source begins sending data when it receives first RREP Forward Path Formation

29. 3’ 3’ 3 1 1 Destination Destination 2 2 4 Source Source 4 Path Maintenance • Movement of nodes not along active path does not trigger protocol action • If source node moves, it can reinitiate route discovery • When destination or intermediate node moves, upstream node of break broadcasts Route Error (RERR) message • RERR contains list of all destinations no longer reachable due to link break • RERR propagated until node with no precursors for destination is reached

30. Performance Evaluation Environment • Simulation environment (QualNet) • 100 nodes • 1000mx1000m square area • transmission range: 100m • channel data rate: 2 Mbps • random mobility model • UDP traffic between randomly selected node pairs • cluster-token MAC layer protocol • HSR • 2 level physical partition • 1 level logical groupings, number of logical subnets varies with network size • FSR • 2 level fisheye scoping • fisheye radius is 2 hops

31. Control O/H vs. number of nodes

32. Control O/H vs. Traffic Pairs

33. Control O/H vs. Mobility (100 pairs)

34. Average Delay (ms)

35. Location-Aided Routing (LAR) • Ko and Vaidya (Texas A & M) • Location assisted (requires GPS) • On-demand • No periodic messages • LAR works like DSR except it limits the flooded area of Route Requests using location information

36. What have we discovered so far? • Conventional (wired net) routing schemes (proactive routing) suffer of O/H, mobility & scalability limitations. • On Demand routing eliminates background routing control O/H. It introduces latency; it does not well suited for QoS routing. • Key observation: • Packet forwarding is done by routing tables (proactive and AODV) • Packet forwarding is done using the source route in header (DSR) • Thus, storage O/H; also route maintenance O/H • Question: Can we eliminate table storage and maintenance O/H? • Hierarchicalrouting reduces O/H and improves scalability (at the expense of accuracy).