Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Ad-Hoc Routing in Wireless Mobile Networks DSR AODV OLSR TBRPF

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Introduction to Wireless Networking Mobility, Power and Bandwidth –Signal Propagation Distance Hidden terminals –Very Limited Power –Limited Bandwidth Medium Access Control –Principally Different from Wired Nets –More routing overhead

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Introduction (2) Two main classes of Ad-Hoc Routing protocols –Reactive Creates routes on-demand Does not maintain routes to all nodes in the network – Pro-active Table driven, stores routes to all nodes in the network

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Introduction (3) Four Routing protocols considered by MANET Working Group: –Reactive Dynamic Source Routing (DSR) Ad-hoc On-Demand Distance Vector Routing (AODV) –Pro-active Optimized Link State Routing Protocol (OLSR) Topology Broadcast based on Reverse Path Forwarding (TBRPF)

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Dynamic Source Routing (DSR) Overview Source Initiated Routing Route discovery and maintenance –RREQ, broadcasted by source in the event of an unknown destination –RREP, unicast from destination or node with route by means of reverse route traversal (reverse of RREQ) –RERR, unicast from neighboring node by means of cached route Neighbor sensing mechanism

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS DSR Overview (2) Multiple routes possible –Spawning of several RREQs for the same destination due to broadcasting –Each RREQ is replied with a RREP Intermediate caching –Routes can be learnt by intermediate nodes by caching RREQs and RREPs that it forwards Promiscuous listening –Nodes in promiscuous mode will not be notified of RERRs and must take measures if a RERR is missed

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Ad-hoc On demand Distance Vector (AODV) Overview Similar to DSR, but does not use source routing Uses –RREQ - broadcast route discovery message –RREP - unicast message to validate a path –RERR - Error message to inform nodes of link failure

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS AODV Overview (2) Routing information stored at the nodes Routing table stores only active routes, unused routes are removed Timers and sequence number are used to avoid stale routes

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS AODV Overview (3) Reverse Path formation –A node receiving a RREQ sets a back-pointer to the sending node –Creates a reverse path towards the source When destination is reached a RREP is sent along the path, validating links Links that are not validated time out and are torn down

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Optimized Link State Routing (OLSR) Overview An optimization of the link-state protocol Introduces serial numbers to handle stale routes The Goal is to –Reduce the flooding of topology control messages –Reduce size of topology control messages

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS OLSR Overview (2) Uses Multipoint relays (MPRs), that relays all traffic from a node Each node advertises the nodes that have selected it as an MPR From this information other nodes can build a "last hop" table and calculate the routing table from this

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS OLSR Overview (3) A subset of 1- hop neighbors are selected as MPRs The set of MPRs must cover all 2- hop neighbors

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Topology Broadcast based on Reverse Path Forwarding (TBRPF) Overview Two modes of operation –Full Topology, (FT) Suited for small networks with few nodes –Partial Topology, (PT) Suited for dense networks Node only reports changes to its source tree Each node can compute min-hop distance to every other node Neighbor discovery –By sending out differentiated HELLO’s New and recently lost neighbors

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS TBRPF Overview (2) Routing function –By means of a reportable subtree Links to all neighbors Branch of the source tree rooted at node j if node i determines that i is the next hop of some neighbor k to reach j ’s reportable subtree 6’s reportable subtree 10’ reportable subtree j i k

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS TBRPF Overview (3) Link failure and rerouting Reorganisation of 2’s and 6’s reportable subtree ’s reportable subtree 6’s reportable subtree 10’ reportable subtree

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Comparison Reactive –Suitable for networks with small subset of nodes communicating –High latency when etablishing new routes –Low storage and message overhead –Difficult to implement QoS Pro-active –Suitable for networks with large subset of nodes communicating –Low latency when establishing connections –Overhead to maintain routes to all destinations –Relatively easy to implement QoS

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Reactive Protocols DSR –Hop-by-hop route to destination stored in cache –Multiple routes possible –Route cache is only updated in terms of RREPs and RERRs. –Generally low routing load –Better performance in small netoworks AODV –Next-hop routing towards destination –One route to each destination –Timers and sequence numbers to avoid stale routes –High routing load for small numbers of nodes –Better performance in larger network

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Pro-Active Routing OLSR –Suitable for dense networks –Use of MPRs reduce the set of active nodes –Small packet size –Dependent on special HELLO messages TBRPF –More topology information is available to nodes –No need for special HELLO messages if network supports link sensing –Very good results in simulations

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Conclusion As more and more devices becomes network aware, good ad-hoc routing algorithms will become increasingly important The choice of what ad-hoc routing algorithm to use is highly dependent on network layout and traffic characteristics Ad-hoc routing is still a hot research topic

Intro DSR AODV OLSR TRBPF Comp Concl 4/12/03 Jon KolstadAndreas Lundin CS Conclusion (2) The standardization process –AODV is generating the most interest in the research community and is furthest along in the standardization process –Not much current research on DSR –TBRPF seems to be a relatively closed project, very few independent articles on TBRPF are published –OLSR is not generating many articles either –More independent performance comparisons are needed, especially for TBRPF and OLSR