Routing, Resource Discovery and Hierarchical Architecture in Wireless Networks

1. Routing, Resource Discovery and Hierarchical Architecture in Wireless Networks Ahmed Helmy Lecture 4 - A Spring 08

2. Methodology & Tools Architecture & Protocol Design Test Synthesis (STRESS) Robust Geographic Wireless Services (Geo-Routing, Geocast, Rendezvous) Protocol Block Analysis (BRICS) Query Resolution in Wireless Networks (ACQUIRE & Contacts) Gradient Routing (RUGGED) Multicast-based Mobility (M&M) Mobility Modeling (IMPORTANT) Worms, Traceback in Mobile Networks Mobility-Assisted Protocols (MAID) Behavioral Analysis in Wireless Networks (MobiLib & IMPACT) Context-Aware Networks Birds-Eye View: Research in Wireless Networks @ UFL

3. Road Map • Unicast Routing with caching • Resource Discovery issues • Contact based architectures • CARD, TRANSFER • Geographic routing issues

4. Related Reading list • From book (C. Perkins): (one order of reading) • ch 3 DSDV, ch 5 DSR, ch 6 AODV, ch 8 TORA, ch 4 cluster-based, ch 7 ZRP • From the paper reading lists • unicast routing list in syllabus (all papers, most overlap with book, read the book or papers) • broadcast: - broadcsat storm, - min dominating sets • Resource discovery: • book chapter (on-line) • TRANSFER, CARD, MARQ

5. Related Reading list (contd.) • Mobility Modeling • IMPORTANT, PATHS, BRICS, Bk Chptr (posted) • Partial reading list for geographic routing aspects • GPSR, - LAR, - Geocast, • From my web site • Perfect Geocast • Inaccuracy/inconsistency , • Face routing with inaccuracy • Mobility prediction • Black listing • Book chapter (posted)

6. Routing and Resource Discovery in Wireless Networks

7. Conventional Approaches • Flooding: • Simple • Overhead: N-1 transmissions, g.(N-1) receptions (where g is average node degree)… expensive! • Expanding Ring Search: • Repeated floods with expanding TTL • Terminates when target found • Initial TTL & increment have significant impact

8. Conventional Approaches (contd.) • Reduced Broadcast heuristics (bcast storm ppr): • Probabilistic rebroadcast with p • Counter-based: suppress bcast if cnt rx > cnt thresh • Distance-based: suppress if min(d) < D thresh, where min(d) is min dist to nbr bcast • Location-based: supp if added coverage > Area thresh • Attempts delivery to all nodes • Does not guarantee delivery • Works well when density/redundant bcast is high

9. Cluster-based and Min. Dominating Set Example connected dominating set, black nodes belong to the backbone constituting a dominating set. - Guarantees delivery - Optimum Dist Algo NP hard - Approximations reduce amount of redundant bcasts to cover all the nodes - re-configuration may be major with dynamics/mobility

10. On-demand routing with caching

11. DSR-like routing model: • a querier node Qissues a request for a target resource T. • The request process progresses as follows: • 1. Q performs local lookup, • 2. If a cached route to Tis not found then request a lookup from 1-hop neighbors (within transmission range), • 3. If a cached route is not found (or is invalid) then flood a request throughout the network, • 4.a. Intermediate nodes with cached route to T reply to Q, • 4.b. The target T replies to requests returning multiple paths to Q.

12. p:hit ratio q: validity ratio qr: obtained by flooding State diagram for on-demand routing in DSR-like mechanisms. Overhead (number of transmitted messages) 1 - local cache lookup: no overhead 2 - Nbr Cache lookup: NC=1+.g, where g av deg, and fraction of nbrs responding 3 - Cost of Flood: CF~(N-1)+g.L+.N..L, where L is av. path length from Q to T, .N is fraction of intermediate nodes responding, and .L is av. path length for such responses • Ov=(1-p1).NC+(1-(p1q1+(1-p1)p2q2)).CF/qr

13. Define cache efficacy as p.q (hit a valid local or nbr cache) [Recall: Overhead  p.q ]

14. For small transfers, in mobile, large-scale, wireless networks, cache efficacy is very low, - need new paradigms: - hierarchy, - hybrid/loose hier. Arch.s