DYMO: Dynamic MANET On-Demand

1. DYMO: Dynamic MANET On-Demand • IETF Draft submitted by MANET WG • Work in progress • Descendant of DSR and AODV • A rewrite of AODV, using different terminology and packet format, but having the same basic functionality • Table driven routing • Significantly smaller amount of routing information than DSR • Path accumulation (cf. DSR) is optional • No precursor list in routing table entries • Makes use of the generalized MANET packet format • Extensible through TLVs • Basic Internet connectivity • AODV and DSR are not consider Internet access • DYMO maintains routing tables with gateway and prefix information • DYMOcast • Packet transmission to all MANET routers within reception range • Broadcast in IPv4 or all node multicast in IPv6 • Maintaining Local Connectivity may use any mechanisms • Link layer feedback • difficulty of obtaining IEEE 802.11 feedback in real networks • Hello messages • periodic one-hop L3 message • many ad hoc networks utilize hello messages • depends on many factors such as loss settings, message size, rate, ... • Neighbor discovery • relay highly on broadcast/multicast capabilities of the underlying link layer • need optimization • Route timeout • difficulty of determining the proper timeout because of dynamic mobility

2. DYMO – Route Discovery • Similar to the route discovery of the AODV • DYMO uses only RE although AODV and DSR use RREQ, RREP • DYMOcast RE with A flag: Route Request • Unicast RE: Route Reply • RE packet format

3. DYMO – Route discovery Comparison

4. Flooding • Advantages • Simplicity • May be more efficient than other protocols when rate of information transmission is low enough • Potentially higher reliability of data delivery • Multiple path • Disadvantages • Potentially, very high overhead • Potentially lower reliability of data delivery • Flooding uses broadcasting -- hard to implement reliable broadcast delivery without significantly increasing overhead • Broadcasting in IEEE 802.11 MAC is unreliable • nodes J and K may transmit to node D simultaneously, resulting in loss of the packet

5. Flooding of Control Packets • Used for route discovery • How to reduce the scope of the route request flood ? • LAR • Query localization • How to reduce redundant broadcasts ? • The Broadcast Storm Problem Collision!

6. TORA: Temporally-Ordered Routing Algorithm [7-12] • A source-initiated on-demand routing protocol which use a link reversal algorithm • Provides loop-free multi-path routes to a destination node • Route establishment function is performed only when a source does not have any directed link • Query/Update • Height of node from the destination

7. TORA Route Maintenance • When a partition is detected, all nodes in the partition are informed, and link reversals in that partition cease

8. LAR: Location-Aided Routing [7-13] • Utilizes the location information (form GPS) to reduce the control packets overhead • Flooding is restricted to a small RequestZone • LAR1 algorithm • LAR2 algorithm • RREQ packet includes the distance S between source and destination • When an intermediate node i receives RREQ, computed the distance DISTi to the destination • If DISTi < S + δ, forward RREQ • Otherwise, discard

9. DREAM : Distance Routing Effect Algorithm for Mobility

10. ABR: Associativity-Based Routing [7-14] • A beacon-based on-demand routing protocol • Selects routes based on the stability of the wireless link • Only links that have been stable for some minimum duration are utilized • motivation: If a link has been stable beyond some minimum threshold, it is likely to be stable for a longer interval. If it has not been stable longer than the threshold, then it may soon break (could be a transient link) • Association stability determined for each link • measures duration for which the link has been stable • Prefer paths with high aggregate association stability

11. SSA: Signal Stability Based Adaptive Routing [7-15] • Similar to DSR • Signal strength is measure for determining signal stability • Strong/stable link • Weak/unstable link • A node X re-broadcasts a Route Request received from Y only if the (X,Y) link is deemed to have a strong signal stability • Signal stability is evaluated as a moving average of the signal strength of packets received on the link in recent past • An alternative approach would be to assign a cost as a function of signal stability

12. Hybrid Routing Protocols

13. ZRP: Zone Routing Protocol [7-18] • Routing zone of a given node: a subset of the network, within which all nodes are reachable within less than or equal to zone radius hops • Intra-zone routing (IARP): employs proactive routing • Inter-zone routing (IERP): uses reactive routing • Source S checks whether destination D is within its zone • Source • If D is within S’s zone, deliver the packet directly • Otherwise, bordercast the RREQ to its peripheral nodes • Peripheral nodes • If any peripheral node finds D to be its routing zone, it sends RREP back to S • Otherwise, re-bordercast RREQ

14. ZHLS: Zone-Based Hierachical Link State Routing Protocol [7-19] • A hybrid routing protocol • Intra-zone routing: • Proactive routing • link state algorithm (SPF) • A hierarchical routing protocol • Reactive routing • Forms non-overlapping zones, using the geographical location information of the nodes • Hierarchical address: (zone ID, node ID) • Zone-level connectivity • Zone LSP are propagatedby the gateway nodes

15. Hierarchical Routing Protocols

16. HSR: Hierarchical State Routing [7-23] • A distributed multi-level hierarchical routing protocol • Employs clustering at different levels • Clustering enhances resource allocation and mgmt • e.g) allocation of different frequency or spreading codes to different clusters • Physical clustering, logical clustering • Link state information is broadcast within the cluster at regular intervals • Cluster leader exchanges the topology and link state routing information with neighbor clusters

17. FSR: Fisheye State Routing [7-23] • To reduce information to represent graphical data for reducing routing overhead • Keep accurate information about near nodes, but not-so-accurate information about far-away nodes • Hybrid approach • Link-level information exchange: use distance vector protocol • Network topology information : link state protocol • Frequency of exchange decreases with an increase in scope

18. Power-Aware Routing Protocols

19. Power-Aware Routing Metrics • Minimal energy consumption per packet • Maximize network connectivity • Minimum variance in node power levels • Distribute the load among all bodes • Minimum cost per packet • Remaining battery charge  cost factor for routing • Minimize maximum node cost • Minimize the max cost per node for a packet after routing a number of packets or after a specific period • This delays the failure of a node

20. Power-Aware Routing • [Singh98Mobicom,Chang00Infocom] • Define optimization criteria as a function of energy consumption. Examples: • Minimize energy consumed per packet • Minimize time to network partition due to energy depletion • Maximize duration before a node fails due to energy depletion • Assign a weigh to each link • Weight of a link may be a function of energy consumed when transmitting a packet on that link, as well as the residual energy level • low residual energy level may correspond to a high cost • Prefer a route with the smallest aggregate weight • Possible modification to DSR to make it power aware (for simplicity, assume no route caching): • Route Requests aggregate the weights of all traversed links • Destination responds with a Route Reply to a Route Request if • it is the first RREQ with a given (“current”) sequence number, or • its weight is smaller than all other RREQs received with the current sequence number