Associativity-Based Routing protocol

1. Computer Science and Engineering Department University of Minnesota Wireless Networking Seminar Associativity-Based Routing protocol Mihaela Cardei mihaela@cs.umn.edu July 12, 2002

2. Chai-Keong Toh, “Associativity-Based Routing For Ad-Hoc Mobile Networks”, Wireless Personal Communication Journal, vol 4, no2, March 1997. C-K Toh, “Ad-Hoc Mobile Wireless Networks, Protocols and Systems”, Prentice Hall PTR, 2002. References

3. Goal: routing protocol suitable for mobility in ad-hoc wireless networks. Conventional routing metrics: Fast adaptability to link changes Min hop path to destination Propagation delay Loop avoidance Link capacity New routing metrics: Route longevity Relaying load of INs supporting existing routes Knowledge of link capacities of the selected route ABR

4. Associativity is related to the spatial, temporal and connection stability of a MH. Rule: the MH association with its neighbors changes as it migrates; the transition period is identified by the associativity ticks. Period of stability: a node is constantly associated with certain neighbors over time without losing connectivity with them. During migration, unstable and stable periods alternate. Each MH periodically transmits short beacons identifying itself and updates its associativity ticks in accordance with MHs sighted. Associativity ticks are updated by the data link layer. Rule and Property of Associativity

5. Athreshold – defines where associativity transitions take place. Rule and Property of Associativity

6. Scenario: cell size d = 10m MH min migration speed v = 2m/s Beacon transmission interval p = 1s Athreshold = d/(vp) = 5 Association stability results when no. of beacons recorded is > Athreshold Low associativity ticks  high state of mobility High associativity ticks  stable state Stability is also determined by signal strength and power life. Rule and Property of Associativity

7. Si – set of possible routes SRCDEST, i=1,2,3… RLji – relaying load in each node j of a route Si RLmax – max route relaying load allowed per MH ATthreshold – min associativity ticks required for association stability ATji – associativity ticks in each node j of a route Si Hi – aggregate degree of association stability of route Si Li - aggregate degree of association instability of route Si Hiave - average degree of association stability of route Si Liave - average degree of association instability of route Si Yi – number of nodes of a route Si with acceptable route relaying load Ui – number of nodes of a route Si with unacceptable route relaying load Yiave – average acceptable route relaying load factor Uiave - average unacceptable route relaying load factor Route Selection Algorithm

8. Begin for each route Si Begin a0 for each node j in route Si Begin if (ATji ATthreshold) Hi++; else Li ++; if (RLji  RLmax) Ui++; else Yi++; a++; End Hiave = Hi/a; Liave = Li/a; Uiave = Ui/a; Yiave = Yi/a; End Best Route Computation Let the set of acceptable routes with Uiave= 0 and Hiave0 be Pl, where PlSi Begin Find route with highest degree of association stability compute route k with Hkave > Hlave ,  l  k. or if a set of routes Kn exists s.t. Hk1ave = Hk2ave= … = Hkpave, where n={1,…,p} Begin Compute min hop route without violating relaying load compute a route Kk with Min{Kk}<Min{Km},  m  k. or if a set of routes Ko exists s.t. Min{k1}=…=Min{kq}, where o={1,2,…,q} Begin Multiple same associativity & min hop routes exists arbitrarily select a min hop route Kk from Ko End End End End.

9. 1. Route Discovery Phase Consists of a broadcast query BQ and await reply REPLY cycle BQ Control Packet: < Type | SRC ID | DEST ID | LIVE | IN ID | Route Quality| … | IN ID| Route Quality | Seq. No. | CRC > Route Quality: < Neighbor’s adress | Associativity ticks, route relaying load, signal strenght, forward delay, remaining power life, etc. > REPLY Control Packet: < Type | SRC ID | DEST ID | IN ID|…|IN ID| Summary of Selected Route Qualities > Summary of Selected Route Qualities: < Aggregate Degree of Association Stability | Route Length | Aggregate Route Relaying Load | Cumulative Forwarding Delay > ABR Protocol Description – Route Discovery Phase

10. ABR Protocol Description – Route Discovery Phase

11. Case when SRC never receives REPLY ABR Protocol Description – Route Discovery Phase • If SRC BQ_TIMEOUT, will send another BQ. • Case 1: • Downstream neighbor realizes the associativity changes, sends RN[1] • downstream, deleting all invalid routing table entries for downstream nodes. • Case 2: • Upstream node performs LQ[H] to discover new partial route • Downstream node sends RN[1] towards the DEST • REPLY packet continue to propagate towards SRC

12. Operations performed: Partial route discovery Invalid route erasure Valid route update New route discovery (worst case) RN Control Packet: < Type | ORG ID | SRC ID | DEST ID | SEQ ID | STEP | DIR | CRC > ORG ID – pivoting node ID ; SRC, DEST ID – identify the route STEP = 0  backtracking, one hop, upstream STEP = 1 DIR = 1, RN packet sent to SRC to invoke BQ-REPLY cycle DIR =0, packet sent to DEST to erase invalid routes LQ Control Packet: < Type | SRC ID | DEST ID | LIVE | IN ID | Route Quality| … | IN ID| Route Quality | Seq. No. | CRC > Route Quality: < Neighbor’s adress | Associativity ticks, route relaying load, signal strenght, forward delay, remaining power life, etc. > ABR Protocol Description – Route Reconstruction Phase

13. ABR Protocol Description – Route Reconstruction Phase

14. When SRC moves Invoke BQ_REPLY process When DEST moves DEST’s upstream neighbor erase its route and sends LQ[H] If DEST receives LQs, selects best partial route & sends REPLY Otherwise, LQ_TIMEOUT and backtrack to pivoting node’s next upstream node Backtrack can continue while d(pivoting node, DEST)  0.5hopsSRC-DEST If no partial route is found, pivoting node sends RN[1] to SRC, to invoke BQ process. When IN moves Upstream node sends LQ[H] Downstream node sends a route erase msg toward DEST, RN[STEP=1, DIR=0]. + the same steps as the previous case ABR Protocol Description – Route Reconstruction Phase

15. RD Control Packet: < Type | SRC ID | DEST ID | Seq. No. | STEP | CRC > Hard State approach: When route is no longer desired, RD is broadcasted by the SRC, so that all INs will update their routing table Soft State Approach: Performed by each node in the route when route entries are invalidated upon time out. ABR Protocol Description – Route Deletion Phase

16. No attempt is made to retain alternate routes Each data packet header contains only neighboring node routing info (not all nodes in the route)  channel utilization efficiency ABR Protocol Description

17. Data flow acknowledgement Passive ack: when a node relays the packet to its neighbors via radio transmission, previous node hear this transmission and uses it as an ack. Active ack: sent by DEST (no neighbor to relay the packet to). Packet retransmission When ack doesn’t reach the intended receiver ( exp. radio interference ) ABR Protocol Description

18. Routing Table ( RT ) ABR Protocol Description - tables • Neighboring Table ( NT ) • usually updated by the data link layer protocol, which interprets beacons • from neighbors and pass this info. to upper layers • Control Packets ‘Seen’ Tables • used to avoid processing/relaying the same BQ or LQ packet twice • check route identifier and sequence number

19. ABR – implemented as a sublayer between IP and MAC This architecture can handle both non-ABR traffic and ABR traffic Control packets originate and terminate at ABR layer ABR beacons are implemented at ABR sublayer SRC IN DEST TCP TCP TCP UDP UDP UDP IP IP IP ABR ABR ABR WIRELESS ETHERNET (MAC) WIRELESS ETHERNET (MAC) WIRELESS ETHERNET (MAC) ABR software architecture

20. New protocol based on a new concept of associativity was proposed Exploit the spatial and temporal relationship of ad-hoc MHs New route selection criteria: long-lived routes , route relaying load. Localize route repair only to the affected region Conclusion