CSE 581 Internet Technology Ad-hoc Routing Schemes Presented by Jason Liu

Agenda  A highly adaptive distributed routing algorithm for mobile wireless networks by Vincent D. Park and M.Scott Corson  Dynamic Source Routing in Ad Hoc Wireless Networks by David B. Johnson and David A. Maltz  Performance Comparison of Two On- demand Routing Protocols for Ad Hoc Networks by Das, Perkins and Royer  A Performance Comparison of Multi-Hop Wireless Ad Hoc Network Routing Protocols by Broch, Maltz, Johnson, Hu, and Jetcheva

Definition  An ad hoc network -- a collection of wireless mobile nodes dynamically forming a temporary network without the use of any existing network infrastructure or centralized administration

A Highly Adaptive Distributed Routing Algorithm for Mobile Wireless Networks Introduction  Problems of routing in a mobile wireless  Nodes move about arbitrarily  Potentially rapid and unpredictable changing topology  Wireless links inherently have significantly lower capacity than hardwired links  More prone to congestion

TORA -- Overview  Minimizes reaction to topological changes  Decouples the generation of control message propagation from the rate of topological changes  Source initiated

TORA  The protocol can be separated into three functions:  Creating routes establishment of a sequence of directed links leading from node to dest.  Maintaining routes re-establish routes  Erasing routes upon detection of network partition, all links must be undirected to erase invalid routes

TORA  It accomplishes three functions through use of control packets:  Query (QRY) – used for creating routes  Update (UPD) – for both creating and maintaining routes  Clear (CLR) – for erasing routes

TORA Basic Operations  Creating Routes  Requires use of the QRY and UPD packets  QRY packet – dest-ID (did)  UPD – did and height of node I broadcasting the packet  Each node maintains a route-required (RR) flag, initially un-set  Node with no directed links and an un- set RR flag requires route to dest, it broadcasts a QRY packet, set RR flag

TORA – Creating Routing Route-required flag set

TORA – Maintaining routes  Maintaining Routes performed only for nodes height > 0

TORA – Erasing Routing  Following detection of a partition, node I sets its height and the height of neighbor to NULL  Update all entries in link-state array  Broadcast a CLR packet

TORA – Erasing Routing Link (D,H) marked as failing

Performance  TORA is able to localize its reaction to topological changes  Best suited for relatively dense networks, only several nearby nodes involved in a reaction  Effect of localization – increased of scalability

Conclusions  Proposed a highly adaptive distributed routing algorithm that well-suited in mobile wireless networks  Decouple the generation of far-reaching control message propagation from the dynamics of the network topology  Possible enhancement would be to periodically propagate refresh packets outwards from the dest.  The refresh process permits intro of far- reaching control message propagation into the protocol independent of the network topology

Dynamic Source Routing Introduction  Oftentimes, mobile users want to communicate  No fixed infrastructure available  Not econo practical or physically possible  Expediency of the situation not permit installation

Introduction – cont  This paper describes the design and performance of DSR for ad hoc networks between hosts that want to communicate  Source Routing – the sender of a packet determines the complete sequence of nodes to forward the packet  Designed for use in wireless ad hoc networks  No periodic router admnts  Dynamically determines route based on cached info and on the results of a route discovery

Benefits of DSR over conven routing protocol  No periodic routing adtsment msg, reducing network bandwidth overhead  Conserve mobile host battery power  Not sending the ad and not receiving them  Not require transmissions between hosts to work bidiectionally  Able to adapt quickly to dynamic topology changes, no protocol overhead

Assumptions (1)  All hosts within ad hoc network are willing to participate fully  Each host participating be willing to forward packets for other hosts  Diameter of ad hoc network be small but often greater than one  Hosts do not continuously move so rapidly  Hosts enable a promiscuous receive mode

Assumptions (2) A B C Diameter of the ad hoc depicted in Figure 1 is two

DSR Operation Overview  To send a packet to another host, the sender constructs a source route in the packets header  Each mobile host participating in the ad hoc network maintains a route cache in which it caches source routes  If no route found, the sender may attempt to discover one using the route discovery protocol.  Host monitors the correct operation of a route in use, we call route maintenance

DSR -- Route Discovery  Allows any host to dynamically discover a route to any other host in the ad hoc network.  A host initiating a route discovery broadcasts a route request packet  If successful, initiating host receives a route reply packet  Each route request packet contains a route record, request id

DSR -- Route Maintenance  Conven routing protocol integrate rd with rm by continuously sending periodic routing updates  Using rd, no periodic msg  Rm monitors the opr of the route and informs the sender of any routing error  Utilize a hop-by-hop ack to provide early detection and retransmission of lost or corrupted packets

DSR -- Route Optimizations A number of optimizations are possible to basic opr of route discovery and route maintenance

DSR -- Route Optimizations  Full use of the Route Cache A B C D F E Figure 2 An example of ad hoc network illustrating use of the route cache

DSR -- Route Optimizations  Piggybacking on Route Discoveries  Sender doesn’t have a route caches to the dest host, initiate a separate route discover  The delay for rd and total # of packets transmitted reduced by allowing data to be piggybacked on route req pack  Use piggyback when sending route reply or route error pack

DSR -- Route Optimizations  Reflecting Shorter Routes  Two hosts comm using cached routes  Desirable to use shorter routes if hosts move suffi closer together  Basic route maint accomplish this  Improvemnt – hosts opr in promiscuous receive mode B C D Figure 3 Mobile host D notices that the route can be shortened

Performance Evaluation Optimal number of transmissions is the number of hops for the data packet needed to get from the sender to intended receiver

Conclusion  Presented a protocol for routing packets in an ad hoc network  Use dynamic source routing  Adapts to routing changes quickly  Requires little or no overhead during hosts move less frequently  Performs well over host density, and movement rates  Overhead 1% of total packets transmitted of 24 mobile hosts  Route length within a factor 1.02 of optimal

Performance comparison of two on- demand routing protocols  Goal  Carry out a systematic performance study of two dynamic routing protocol

Common characteristics  DSR and AODV  Both initiate routing activities on an “on-demand” basis  Both reactive vs traditional proactive  Reduce routing load

Differences  DSR  Uses source routing  Doesn’t rely on timer-based activities  AODV  Uses table-driven routing framework and dest sequence number  rely on timer-based activities

DSR  Uses source routing  Sender knows complete hop-by-hop route to dest  Routes stores in route cache, carried in packet header  Uses route discovery Flooding network with route req pack(RREQ) and reply with (RREP) Flooding network with route req pack(RREQ) and reply with (RREP)  Link broken notified using route error (RERR) packet  Source removes link from cache  New route discovery initiated

AODV  Uses routing table to propagate a RREP back to source  Uses sequence number to determine freshness of routing info and prevent routing loop  Timer-based states in each node regarding routing table entries  Nodes notified (RERR) when next hop link broken

Critique of DSR and AODV (1) 1. DSR has access to a greater amount of routing info than AODV  DSR uses single req-reply cycle  Promiscuous listening give access to great amount of info  In absence of above two, AODV gather only limited amount of routing info  AODV reply on route discovery flood more often

Critique of DSR and AODV (2) 2. DSR replies to all requests reaching dest from a single req cycle.  Could save route discovery flood AODV – dest replies only once to req arriving first and ignore the rest  The routing table maintain at most one entry per dest

Critique of DSR and AODV (3) 3. Current spec of DSR not expire stale routes in the cache faced multi choices  Stale entries are deleted by route error packets AODV more conservative  When faced with two choices, the fresher route is always chosen (dest sequence #)  If routing table entry not used recently, this entry expired

Critique of DSR and AODV (4) 4. Route deletion using RERR is conser in AODV In DSR, route error backtracks the data pack meets a failed link

Performance Evaluation  50 nodes experiments with 10, 40 traffic sources  Packet rate – 4 pack/sec for 10 sources  Packet rate – 3 pack/sec for 40 sources  DSR and AODV – similar pack frac for 10 or 20 source AODV outperform DSR with 30 and 40 sources

Performance Evaluation

Packet delivery fractions for 50 node model

Performance with increasing offered load with 100 nodes and 10 sources DSR

Conclusions  DSR outperforms AODV in less “stressful” situations  Smaller # of nodes, lower load/mobility  AODV outperforms DSR in more stressful situations  DSR generates less routing load than AODV

Performance comparison of Multi-hop Wireless ad hoc network Routing protocol  Provide a realistic quantitative analysis comparing the performance of a variety of multi- hop wireless ad hoc network routing protocol  Present results showing the relative performance of four ad hoc routing protocols: DSDV [18], TORA [14,15], DSR [9,10,2], and AODV [17]

Ad hoc routing protocols review (1)  Destination-Sequenced Distance Vector (DSDV)  A hop-by-hop distance vector routing protocol  requires each node to periodically broadcast routing updates  Guarantees loop-freedom over traditional protocols  Each node maintains a routing table listing the “next hop”  DSDV tags each route with a sequence number

Ad hoc routing protocols review (2)  Temporally-ordered routing algorithm (TORA)  A distributed protocol based on “link-reversal”  Discover routes on-demand, provide multi-route to dest, minimize comm overhead by localizing reaction to topological changes  Dynamic Source Routing (DSR)  Uses source routing rather than hop-by-hop routing  Packet header carries ordered list of nodes to pass  Intermediate nodes don’t need to maintain up-to-date routing info  Eliminates need for periodic route advertisement and neighbor detection packets

Ad hoc routing protocols review (3)  Ad hoc on-demand distance vector (AODV)  A combination of both DSR and DSDV  Borrows on-demand mechanism of Route Discovery and Route Maintenance from DSR  Plus use of hop-by-hop routing, sequence number, and periodic beacons from DSDV

Performance Comparison Summary (1) Node mobility

Performance Comparison Summary (2) DSR has least overhead, TORA has most

Performance Comparison Summary (3) Packet Delivery Ratio

Performance Comparison Summary (4) Routing Overhead

Conclusions  These protocols, DSDV, TORA, DSR, and AODV covers range of design  including periodic advertisements vs. on demand routing discovery  Hop-by-hop routing vs. source routing  DSDV performs predictably  Node mobility rate, movement speed are low  TORA performs worst of routing overhead  DSR performs very good at all mobility rates and movement speeds  Use of source routing increase # of routing bytes req  AODV performs almost as well as DSR at  Mobility rates, and movement speeds  Accomplishes goal of eliminating source routing overhead