OGPR Or Improved Geographic Routing in 4(+1) messages

1. OGPROrImproved Geographic Routing in 4(+1) messages ORIGIONAL AUTHORS: Venkata C. Giruka, Mukesh Singhal PRESENTED BY: Brandon Hetman

2. Outline • Previous work in the field • OGPR • Adaptive HELLO beacons • Grid based position encoding • Protocol • PREQ • PREP • PUPD & Path Healing • PERR • Performance Comparisons • Questions

3. Previous Work in the Field

4. Topology Based Protocols • Actively maintains routes to the Destination • May be done through a pro-active, reactive, or combination method • Establishing and maintaining these routes increases protocol overhead • Impacts performance • Limits scalability • Especially in networks with rapidly changing topology or fast moving nodes

5. Position Based Protocols • Don't rely on topology information • Use localized algorithms • Don't establish or maintain routes • Are more scalable • Require a location service • Require a means to recover from dead ends • Greedy forwarding and dead end recovery may lead to sub-optimal and circular paths

7. Enter ogpr On-Demand Geographic Path Routing Protocol • A hybrid of position based and topology based protocols • A position protocol that: • Is loop free and can reliably route to the destination • Handles unreachable routes like topology protocols • Does not depend on a location service • Has low control overhead • Has average path length similar to topology protocols • Scalable and can deal with unidirectional links

8. Enter OGPR Continued • Nodes establish geographic paths on-demand • Uses greedy forwarding along geographic paths • Location services are implicit and on-demand • Geographic paths avoid dead ends on sufficiently populated paths • Employs source routing and a path healing mechanism to mitigate path breaks • An adaptive hello protocol and grid based position encoding minimize control overhead • Extensible to networks with unidirectional links

9. Adaptive hello beacons

10. Adaptive hello beacons • Enable nodes to maintain one-hop neighbor tables • Nodes send HELLO beacons x meters • Or at Minimum Beacon Interval (MINBI) • Fast nodes can send no more frequently than the rate of MINBI • Or at Maximum Beacon Interval (MAXBI) • Slow nodes send at least as often as the rate of MAXBI • Faster nodes ⇒ More HELLO beacons • Slower nodes ⇒ Fewer HELLO beacons

11. Adaptive Hello Beacon Continued • ID • Velocity (Speed & Direction) • This information is inserted directly into the one-hop neighbor table • Nodes can use the velocity information from the beacon and their own velocity to add timeout information to the one-hop neighbor table

12. Grid Based Position encoding

14. Grid based position encoding • Nodes are assigned grid (logical quadratic tree) based addresses • Network area is divided into unit square regions with length d. This is called an order-1 grid • Four adjacent order-1 grids make an order 2 grid. • And so on...

15. Grid based position encoding • Within an order, each order-i grid is assigned a number from 0 to 3 in a counter clockwise manner • Addresses are a k-bit number • each pair of bits represent an order-N grid • 2(N-1) bits are needed to address a grid • Grid covers an area of (2^(N-1))*d^2

17. OGPR Protocol

18. Path request (PREQ) Used to find a path to the destination • Flooded throughout the network • initiated on-demand • Intermediate nodes insert their grid address into the request to form a path Contents: • Source ID • Destination ID • Sequence number (monotonically increasing) • TTL (in hops) • Geographic path (initialized to source address

19. path reply (Prep) • Destination response to PREQContains the geographic path from the PREQ • intermediate nodes greedy forward along this path in reverse • Contains:Source ID • Destination ID • Geographic path Note that the geograpic path here does not contain node IDs. Any node along the path can forward the PREP

20. Path update (PUPD) & path healing • Path healing helps mitigate path breaks in sparse networksEach data packet contains the geographic path it followed • This may differ from the PREQ/PERP path • So... When the destination receives a packet along a new path it uses a PUPD to inform the source of this new path. • Reduces the need for path re-establishment • Greatly improves performance Contains: • The contents of the last PREP • New path

22. Path error (PERR) • If an intermediate node detects a path break it sends a PERR to the source • The source then restarts the PREQ process.

23. Performance comparisons

24. Packet Delivery rato vs. speed

25. Control Overhead vs. speed

26. Hop count vs. speed

27. Packet delivery ratio vs. network density

28. Control overhead vs network density

29. hop count vs. network density

30. Packet Delivery Ratio vs. network size

31. Control overhead vs. network size

32. hop count cs. network size

33. Ogpr pseudocode

34. When source wants to send • If dest is in one-hop table • packet is unicast to dest • else if src knows route to dest • route to dest using geographic path • else • buffer data and initiate PREQ • start PREP_WAIT timeout if PREP_WAIT expires PREQ is re-initiated for up to MAX-RETRY times

35. When an intermediate node receives a preq • if PREQ is not in the PREQSeen cache • insert PREQ into PREQSeen cache • append grid address to the PREQ path • decrement the PREQ TTL • if PREQ TTL > 0 • broadcast packet • else • drop packet • else • drop packet

36. When destination receives preq • append address to PREQ path • insert path into OGPRGeoPath • route PREP to source using greedy forwarding along the reverse path

37. When The source receives prep • insert PREP path into OGPRGeoPath cache • remove packets from buffer and add path to the packets • forward packet

38. When a node forwards packets • if a node closest to the path can be found • unicast packet to the node • else • drop packet • generate PERR • send PERR along the reverse path to the source

39. When source receives perr • buffer packets • remove path from OGPRGeoPath cache • initiate PREQ

40. when destination receives data • append grid address to NewGeoPath • if NewGeoPath != SrcGeoPath • send PUPD along reverse NewGeoPath

41. When source receives pupd • remove destination path from OGPRGeoPath cache • insert NewGeoPath for destination into the cache

42. limitations • 3D • Initial position discovery • Efficiency • Security

43. Questions?