AD HOC NETWORKS

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Ad Hoc Networks

• Infrastructure-less wireless networks dynamically
  formed using only mobile hosts (no routers)
• Network topology dynamic as all hosts are mobile!
• Mobile hosts themselves double up as routers!!
• Multi-hop paths
• Highly resource constrained
• Extreme case of network mobility

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Topologies-Ad Hoc Networking

• An ad hoc network is a peer-to-peer network (no
  centralized server) set up temporarily to meet
  some immediate need.
• For example, a group of employees, each with a
  laptop or palmtop computer may convene in a
  conference room for a business or classroom
  meeting.
• The employees link their computers in a temporary
  network just for the duration of the meeting.

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Topologies-Ad Hoc Networking
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Topologies-Ad Hoc Networking

• Differences between
• Ad-Hoc wireless LAN and a CLASSICAL wireless LAN
• The classical wireless LAN forms a stationary
  infrastructure consisting of one or more cells
  with a control module for each cell.
• Within a cell, there may be a number of
  stationary end systems.
• Nomadic stations can move from one cell to
  another.
• In contrast, there is no infrastructure for an
  ad-hoc network.
• Rather, a peer collection of stations within
  range of each other may dynamically configure
  themselves into a temporary network.

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Illustration
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Wireless Ad Hoc Networks

• Disaster recovery
• Battlefield
• Smart office
• Gaps in cellular infrastructure
• Virtual Navigation (cities, buildings, areas,
  etc..)
• Telemedicine (e.g., accident sites)
• Tele-Geoprocessing Applications
• Education via Internet

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Classes of Wireless Ad Hoc Networks

• Three distinct classes
• Mobile Ad Hoc Networks (MANET)
• possibly highly mobile nodes
• power constrained
• Wireless Ad Hoc Sensor/Device Networks
• relatively immobile
• severely power constrained nodes
• large scale
• Wireless Ad Hoc Backbone Networks
• rapidly deployable wireless infrastructure
• largely immobile nodes
• Common attributes
• Ad hoc deployment, no infrastructure
• Routes between S-D nodes may contain multiple hops

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Multihop Routing

• Traverse multiple links to reach a destination

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MANET

• Mobility causes route changes

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Variations

• Fully symmetric vs. asymmetries in
• Transmission ranges
• Battery life
• Processing capability
• Speed, patterns, and predictability of movement
• Ability to act as multihop relay
• Ability to act as leaders of a cluster of nodes
• Coexistence with an infrastructure
• Variations in traffic characteristics
• Bit rate, timeliness
• Unicast/multicast/geocast
• Addressing (host, content, capability)

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Unicast Routing in MANET

• Host mobility
• link failure/repair due to mobility may have
  different characteristics than those due to other
  causes
• Rate of link failure/repair may be high when
  nodes move fast
• New performance criteria may be used
• route stability despite mobility
• energy consumption
• Many protocols have been proposed
• Some have been invented specifically for MANET
• Others are adapted from older protocols for wired
  networks
• No single protocol works well in all environments
• some attempts made to develop adaptive protocols

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Types of Protocols

• Proactive Protocols
• Determine routes independent of traffic pattern
• Traditional (link-state, distance-vector) routing
  protocols are proactive
• Reactive Protocols
• Maintain routes only if needed
• Hybrid Protocols

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Traditional Routing Algorithms

• Distance Vector
• periodic exchange of messages with all physical
  neighbors that contain information about who can
  be reached at what distance
• selection of the shortest path if several paths
  available
• Link State
• periodic notification of all routers about the
  current state of all physical links
• router gets a complete picture of the network
• Example
• ARPA packet radio network (1973), DV-Routing
• every 7.5s exchange of routing tables including
  link quality
• updating of tables also by reception of packets
• routing problems solved with limited flooding

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Problems of Traditional Routing Algorithms

• Dynamic of the topology
• frequent changes of connections, connection
  quality, participants
• Limited performance of mobile systems
• periodic updates of routing tables need energy
  without contributing to the transmission of user
  data, sleep modes difficult to realize
• limited bandwidth of the system is reduced even
  more due to the exchange of routing information
• links can be asymmetric, i.e., they can have a
  direction dependent transmission quality
• Problem
• protocols have been designed for fixed networks
  with infrequent changes and typically assume
  symmetric links

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Routing Protocols for Ad Hoc Networks

• Proactive Routing Protocols
• DSDV (Destination Sequenced Distance Vector)
• LSR (Link State Routing)
• Reactive Routing Protocols
• DSR (Dynamic Source Routing)
• AODV (Ad-Hoc on-Demand Distance Vector)
• Hybrid Routing Protocols
• ZRP (Zone Routing Protocol)
• TORA
• CEDAR (Core Extraction Distributed Ad-hoc Routing)

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Proactive Routing Protocols

• Unsuitable for such a dynamic network
• For example, consider link-state routing that
  sends out network-wide floods for every
  link-state change
• Even in the absence of any existing connections,
  considerable overhead spent in maintaining
  network state

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Goals

• Low overhead route computation
• Ability to recover from frequent failures at
  low-cost
• Scalable (with respect to mobility and number of
  hosts)
• Robust

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Reactive (On-Demand) Protocols

• Compute routes only when needed
• Even if network state changes, any re-computation
  done only when any existing connections are
  affected

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Dynamic Source Routing (DSR)

• Based on source routing
• On-demand
• Route computation performed on a per-connection
  basis
• Source, after route computation, appends each
  packet with a source-route
• Intermediate hosts forward packet based on source
  route
• TWO PHASES ROUTE DISCOVERY
• ROUTE MAINTENANCE

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Dynamic Source Routing (DSR)

• When node S wants to send a packet to node D, but
  does not know a route to D, node S initiates a
  route discovery
• Source node S floods (bradcasts) Route Request
  (RREQ) packet.
• RREQ packet contains DESTINATION ADDRESS, SOURCE
  NODE ADDRESS and A UNIQUE IDENTIFICATION NUMBER.
• Each node receiving the packet checks whether it
  knows of a route to destination.
• If it does not, it appends/adds its own
  identifier (address) to the route record and
  forwards the RREQ
• packet.

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Dynamic Source Routing (DSR)

• REMARK
• To limit the number of route requests, a node
  only forwards the RREQ packet if the request has
  not yet been seen by the node and if the nodes
  address does not already appear in the route
  record.

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Dynamic Source Routing I

• Split routing into discovering a path and
• maintaining a path
• Discover a path
• only if a path for sending packets to a certain
• destination is needed and no path is currently
• available
• Maintaining a path
• only while the path is in use one has to make
  sure
• that it can be used continuously
• No periodic updates needed!

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Dynamic Source Routing II

• Path discovery
• broadcast a packet with destination address and
  unique ID
• if a station receives a broadcast packet
• if the station is the receiver (i.e., has the
  correct destination address) then return the
  packet to the sender (path was collected in the
  packet)
• if the packet has already been received earlier
  (identified via ID) then discard the packet
• otherwise, append own address and broadcast
  packet
• sender receives packet with the current path
  (address list)
• Optimizations
• limit broadcasting if maximum diameter of the
  network is known
• caching of address lists (i.e. paths) with help
  of passing packets
• stations can use the cached information for path
  discovery (own paths or paths for other hosts)

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Dynamic Source Routing III

• Maintaining paths
• after sending a packet
• wait for a layer 2 acknowledgement (if
  applicable)
• listen into the medium to detect if other
  stations forward the packet (if possible)
• request an explicit acknowledgement
• if a station encounters problems it can inform
  the sender of a packet or look-up a new path
  locally

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Route Discovery in DSR
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Represents a node that has received RREQ for D
from S
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Route Discovery in DSR
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Broadcast transmission
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Represents transmission of RREQ
X,Y Represents list of identifiers appended
to RREQ
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Route Discovery in DSR
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S,C
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• Node H receives packet RREQ from two neighbors
• potential for collision

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Route Discovery in DSR
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S,C,G
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• Node C receives RREQ from G and H, but does not
  forward
• it again, because node C has already forwarded
  RREQ once

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Route Discovery in DSR
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S,E,F,J
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S,C,G,K

• Nodes J and K both broadcast RREQ to node D
• Since nodes J and K are hidden from each other,
  their
• transmissions may collide

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Route Discovery in DSR
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S,E,F,J,M
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• Node D does not forward RREQ, because node D
• is the intended target of the route discovery

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Route Discovery in DSR

• Destination D on receiving the first RREQ, sends
  a Route Reply (RREP)
• RREP is sent on a route obtained by reversing the
  route appended to received RREQ
• RREP includes the route from S to D on which RREQ
  was received by node D

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Route Reply in DSR
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RREP S,E,F,J,D
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Represents RREP control message
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Route Reply in DSR

• Route Reply can be sent by reversing the route in
  Route Request (RREQ) only if links are guaranteed
  to be bi-directional (SYMMETRICAL)
• To ensure this, RREQ should be forwarded only if
  it received on a link that is known to be
  bi-directional
• If unidirectional (asymmetric) links are allowed,
  then RREP may need a route discovery for S from
  node D
• Unless node D already knows a route to node S
• If a route discovery is initiated by D for a
  route to S, then the Route Reply is piggybacked
  on the Route Request from D.
• If IEEE 802.11 MAC is used to send data, then
  links have to be bi-directional (since ACK is
  used)

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Dynamic Source Routing (DSR)

• Node S on receiving RREP, caches the route
  included in the RREP
• When node S sends a data packet to D, the entire
  route is included in the packet header
• hence the name source routing
• Intermediate nodes use the source route included
  in a packet to determine to whom a packet should
  be forwarded

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Data Delivery in DSR
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DATA S,E,F,J,D
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Packet header size grows with route length
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DSR Optimization Route Caching

• Each node caches a new route it learns by any
  means
• When node S finds route S,E,F,J,D to node D,
  node S also learns route S,E,F to node F
• When node K receives Route Request S,C,G
  destined for node, node K learns route K,G,C,S
  to node S
• When node F forwards Route Reply RREP
  S,E,F,J,D, node F learns route F,J,D to node
  D
• When node E forwards Data S,E,F,J,D it learns
  route E,F,J,D to node D
• A node may also learn a route when it overhears
  Data packets

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Use of Route Caching

• When node S learns that a route to node D is
  broken, it uses another route from its local
  cache, if such a route to D exists in its cache.
• Otherwise, node S initiates route discovery by
  sending a route request
• Node X on receiving a Route Request for some node
  D can send a Route Reply if node X knows a route
  to node D
• Use of route cache
• can speed up route discovery
• can reduce propagation of route requests

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Use of Route Caching
S,E,F,J,D
E,F,J,D
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F,J,D,F,E,S
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P,Q,R Represents cached route at a node
(DSR maintains the cached routes in a
tree format)
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Use of Route CachingCan Speed up Route Discovery
S,E,F,J,D
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RREP
RREQ
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When node Z sends a route request for node C,
node K sends back a route reply Z,K,G,C to node
Z using a locally cached route
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Use of Route CachingCan Reduce Propagation of
Route Requests
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S,E,F,J,D
E,F,J,D
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RREP
RREQ
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Route Reply (RREP) from node K limits flooding
of RREQ. In general, the reduction may be less
dramatic.
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Route Error (RERR)
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RERR J-D
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J sends a route error to S along route J-F-E-S
when its attempt to forward the data packet S
(with route SEFJD) on J-D fails Nodes hearing
RERR update their route cache to remove link J-D
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Route Caching Beware!

• Stale (obsolete) caches can adversely affect
  performance
• With passage of time and host mobility, cached
  routes may become invalid
• A sender host may try several stale routes
  (obtained from local cache, or replied from cache
  by other nodes), before finding a good route

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Dynamic Source Routing Advantages

• Routes maintained only between nodes who need to
  communicate
• reduces overhead of route maintenance
• Route caching can further reduce route discovery
  overhead
• A single route discovery may yield many routes to
  the destination, due to intermediate nodes
  replying from local caches

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Dynamic Source Routing Disadvantages

• Packet header size grows with route length
• Flood of route requests may potentially reach all
  nodes
• Care must be taken to avoid collisions between
  route requests propagated by neighboring nodes
• insertion of random delays before forwarding RREQ
• Increased contention if too many route replies
  come back due to nodes replying using their local
  cache
• Route Reply Storm problem
• Reply Storm may be eased by preventing a node
  from sending RREP if it hears another RREP with a
  shorter route
• An intermediate node may send Route Reply using a
  stale cached route, thus polluting other caches
• This problem can be eased if some mechanism to
  purge (potentially) invalid cached routes is
  incorporated.

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Ad Hoc On-Demand Distance Vector Routing (AODV)

• DSR includes source routes in packet headers
• Resulting large headers can sometimes degrade
  performance
• particularly when data contents of a packet are
  small
• AODV attempts to improve on DSR by maintaining
  routing tables at the nodes, so that data packets
  do not have to contain routes
• AODV retains the desirable feature of DSR that
  routes are maintained only between nodes which
  need to communicate

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AODV

• Route Requests (RREQ) are forwarded in a manner
  similar to DSR
• When a node re-broadcasts a Route Request, it
  sets up a reverse path pointing towards the
  source
• AODV assumes symmetric (bi-directional) links
• When the intended destination receives a Route
  Request, it replies by sending a Route Reply
• Route Reply travels along the reverse path set-up
  when Route Request is forwarded

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AODVAd Hoc On-demand Distance Vector Routing

• Hop-by-hop routing as opposed to source routing
• On-demand
• When a source node wants to send a message to
  some destination node and does not already have a
  valid route to that destination, it initiates a
  path discovery process to locate the destination
  (as in DSR case)
• It broadcasts the RREQ packet to its neighbors
• They then send it to their neighbors until the
  destination or a node with fresh enough cash
  information to the destination is located.

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AODVAd Hoc On-demand Distance Vector Routing

• When RREQ propagates, routing tables are updated
  at intermediate nodes (for route to source of
  RREQ)
• When RREP is sent by destination, routing tables
  updated at intermediate nodes (for route to
  destination), and propagated back to source

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AODVAd Hoc On-demand Distance Vector Routing

• Each node maintains its own sequence number and a
  broadcast ID.
• The broadcast ID is incremented for every RREQ
  the node initiates and together with the nodes
  IP address, uniquely identifies an RREQ.
• Along with its own sequence number and broadcast
  ID, the source node includes in the RREQ the most
  recent sequence number it has for the
  destination.
• Intermediate nodes can reply to the RREQ only if
  they have a route to the destination whose
  corresponding destination sequence number is
  greater than or equal to that contained in the
  RREQ.

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AODVAd Hoc On-demand Distance Vector Routing

• During the process of forwarding the RREQ,
  intermediate nodes recording their route tables
  the address of the neighbor from which the first
  copy of the broadcast packet is received?
  establishing a reverse path.
• If more same RREQs are received later, they are
  discarded.
• RREP packet is sent back to the neighbors and the
  routing tables are accordingly updated.

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Route Requests in AODV
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Represents a node that has received RREQ for D
from S
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Route Requests in AODV
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Broadcast transmission
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S
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C
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Represents transmission of RREQ
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Route Requests in AODV
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Represents links on Reverse Path
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Reverse Path Setup in AODV
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• Node C receives RREQ from G and H, but does not
  forward
• it again, because node C has already forwarded
  RREQ once

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Reverse Path Setup in AODV
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Reverse Path Setup in AODV
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• Node D does not forward RREQ, because node D
• is the intended target of the RREQ

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Route Reply in AODV
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Represents links on path taken by RREP
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Route Reply in AODV

• An intermediate node (not the destination) may
  also send a Route Reply (RREP) provided that it
  knows a more recent path than the one previously
  known to sender S
• To determine whether the path known to an
  intermediate node is more recent, destination
  sequence numbers are used
• The likelihood that an intermediate node will
  send a Route Reply when using AODV not as high as
  DSR
• A new Route Request by node S for a destination
  is assigned a higher destination sequence number.
  An intermediate node which knows a route, but
  with a smaller sequence number, cannot send Route
  Reply

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Forward Path Setup in AODV
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Forward links are setup when RREP travels
along the reverse path Represents a link on the
forward path
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Data Delivery in AODV
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DATA
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Routing table entries used to forward data
packet. NOTE Route is not included in packet
header as in DSR.
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Timeouts

• A routing table entry maintaining a reverse path
  is purged after a timeout interval
• timeout should be long enough to allow RREP to
  come back
• A routing table entry maintaining a forward path
  is purged if not used for a active_route_timeout
  interval
• if no data is being sent using a particular
  routing table entry, that entry will be deleted
  from the routing table (even if the route may
  actually still be valid)

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Link Failure Reporting

• A neighbor of node X is considered active for a
  routing table entry if the neighbor sent a packet
  within active_route_timeout interval which was
  forwarded using that entry
• When the next hop link in a routing table entry
  breaks, all active neighbors are informed
• Link failures are propagated by means of Route
  Error messages, which also update destination
  sequence numbers

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Route Error

• When node X is unable to forward packet P (from
  node S to node D) on link (X,Y), it generates a
  RERR message
• Node X increments the destination sequence number
  for D cached at node X
• The incremented sequence number N is included in
  the RERR
• When node S receives the RERR, it initiates a new
  route discovery for D using destination sequence
  number at least as large as N
• When node D receives the route request with
  destination sequence number N, node D will set
  its sequence number to N, unless it is already
  larger than N

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Link Failure Detection

• Hello messages Neighboring nodes periodically
  exchange hello message
• Absence of hello message is used as an indication
  of link failure
• Alternatively, failure to receive several
  MAC-level acknowledgement may be used as an
  indication of link failure

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Why Sequence Numbers in AODV

• To avoid using old/broken routes
• To determine which route is newer
• To prevent formation of loops
• Assume that A does not know about failure of link
  C-D because RERR sent by C is lost
• Now C performs a route discovery for D. Node A
  receives the RREQ (say, via path C-E-A)
• Node A will reply since A knows a route to D via
  node B
• Results in a loop (for instance, C-E-A-B-C )

A
B
C
D
E
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Optimization Expanding Ring Search

• Route Requests are initially sent with small
  Time-to-Live (TTL) field, to limit their
  propagation
• DSR also includes a similar optimization
• If no Route Reply is received, then larger TTL
  tried

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Summary AODV

• Routes need not be included in packet headers
• Nodes maintain routing tables containing entries
  only for routes that are in active use
• At most one next-hop per destination maintained
  at each node
• DSR may maintain several routes for a single
  destination
• Unused routes expire even if topology does not
  change

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Proactive Protocols

• Most of the schemes discussed so far are reactive
• Proactive schemes based on distance-vector and
  link-state mechanisms have also been proposed

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Link State Routing

• Each node periodically floods status of its links
• Each node re-broadcasts link state information
  received from its neighbor
• Each node keeps track of link state information
  received from other nodes
• Each node uses above information to determine
  next hop to each destination

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Destination-Sequenced Distance-Vector (DSDV)

• Each node maintains a routing table which stores
• next hop towards each destination
• a cost metric for the path to each destination
• a destination sequence number that is created by
  the destination itself
• Sequence numbers used to avoid formation of loops
• Each node periodically forwards the routing table
  to its neighbors
• Each node increments and appends its sequence
  number when sending its local routing table
• This sequence number will be attached to route
  entries created for this node

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Destination-Sequenced Distance-Vector (DSDV)

• Assume that node X receives routing information
  from Y about a route to node Z
• Let S(X) and S(Y) denote the destination sequence
  number for node Z as stored at node X, and as
  sent by node Y with its routing table to node X,
  respectively

Z
X
Y
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Destination-Sequenced Distance-Vector (DSDV)

• Node X takes the following steps
• If S(X) gt S(Y), then X ignores the routing
  information received from Y
• If S(X) S(Y), and cost of going through Y is
  smaller than the route known to X, then X sets Y
  as the next hop to Z
• If S(X) lt S(Y), then X sets Y as the next hop to
  Z, and S(X) is updated to equal S(Y)

Z
X
Y
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Comparison
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Hybrid Protocols Zone Routing Protocol (ZRP)

• Zone routing protocol combines
• Proactive protocol which pro-actively updates
  network state and maintains route regardless of
  whether any data traffic exists or not
• Reactive protocol which only determines route to
  a destination if there is some data to be sent to
  the destination
• All nodes within hop distance at most d from a
  node X are said to be in the routing zone of node
  X
• All nodes at hop distance exactly d are said to
  be peripheral nodes of node Xs routing zone

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ZRP

• Intra-zone routing Pro-actively maintain state
  information for links within a short distance
  from any given node
• Routes to nodes within short distance are thus
  maintained proactively (using, say, link state or
  distance vector protocol)
• Inter-zone routing Use a route discovery
  protocol for determining routes too far away
  nodes. Route discovery is similar to DSR with the
  exception that route requests are propagated via
  peripheral nodes.

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Temporally-Ordered Routing Algorithm (TORA)

• On demand routing.
• Designed for a dynamic environment.
• Each node keeps routing information about
  adjacent nodes.
• A DAG (Directed Acyclic Graph) describes all
  discovered paths to a node.
• When one link fails, its neighbors reverse
  direction in the DAG, and utilize another path.
• Timing of failures is important, so TORA requires
  synchronized clocks (i.e. GPS)

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Temporally-Ordered Routing Algorithm (TORA)

• Water flowing downhill toward to a destination
  node through a network of tubes/pipes that models
  the routing state of the real network.
• Tubes/pipes represent links between nodes in the
  network, junctions of tubes represent the nodes,
  and the water in the tubes represents the packets
  flowing toward the destination.
• Each node has a height with respect to the
  destination that is computed by the routing
  protocol.

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Temporally-Ordered Routing Algorithm (TORA)

• If a tube between nodes A and B becomes blocked
  such that water can no longer flow through it,
  the height of A is set to a height greater than
  that of any of is remaining neighbors, such that
  water fill now flow back out of A (and toward the
  other nodes that had been routing packet to the
  destination via A).

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Temporally-Ordered Routing Algorithm (TORA)

• TORA performs 3 basic functions
• ROUTE CREATION
• ROUTE MAINTENANCE
• ROUTE ERASURE

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TORA ROUTE CREATION MAINTENANCE

• For each node in the network a separate directed
  acyclic graph (DAG) is maintained for each
  destination.
• When a node needs a route to a destination, it
  broadcasts a QUERY packet containing the
  destination address.
• This packet travels through the network until it
  reaches either the destination or an intermediate
  node which already has a path to that
  destination.
• The recipient of the QUERY packet then broadcasts
  an UPDATE packet listing its height with respect
  to the destination.
• Each node receiving this UPDATE packet sets is
  height to a value greater than the height of the
  neighbor from which the UPDATE packet has been
  received.
• When a node detects a network partition, it
  generates a CLEAR packet that resets routing
  state and removes invalid routes from the
  network.

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TORA ROUTE CREATION MAINTENANCE

• During the route creation and maintenance phases,
  nodes use the height metric to establish a DAG
  rooted at the destination.
• Links are assigned a direction (upstream or
  downstream) based on the relative height metric
  of neighboring nodes.
• (See Figure)

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TORA ROUTE CREATION MAINTENANCE

• For node mobility when the DAG route is broken,
  and route maintenance is necessary to
  re-establish a DAG rooted at the same
  destination.
• See Figure? upon failure of the last downstream
  link, a node generates a new reference level.
• Links are reversed to reflect the change.

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TORA
85
TORA
86
TORA
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TORA
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TORA
89
TORA

• TORA is partially proactive and partially
  reactive
• Reactive ? route creation is initiated on
  demand.
• Proactive ? Route maintenance is done proactively
  such that multiple routing options are available
  in case of link failures.

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So far ...

• All nodes had identical responsibilities
• Some schemes propose giving special
  responsibilities to a subset of nodes
• Even if all nodes are physically identical
• Core-based schemes are examples of such schemes

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Core-Extraction Distributed Ad Hoc Routing
(CEDAR)

• A subset of nodes in the network is identified as
  the core
• Each node in the network must be adjacent to at
  least one node in the core
• Each node picks one core node as its dominator
  (or leader)
• Core is determined by periodic message exchanges
  between each node and its neighbors
• attempt made to keep the number of nodes in the
  core small
• Each core node determines paths to nearby core
  nodes by means of a localized broadcast
• Each core node guaranteed to have a core node at
  lt3 hops

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CEDAR Core Nodes
A
G
D
B
C
E
H
F
J
S
K
Node E is the dominator for nodes D, F and K
A core node
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CEDAR

• Advantages
• Route discovery/maintenance duties limited to a
  small number of core nodes
• Link state propagation a function of link
  stability/quality
• Disadvantages
• Core nodes have to handle additional traffic,
  associated with route discovery and maintenance

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SUMMARYCharacteristics of DSDV
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SUMMARYCharacteristics of On-Demand Routing
Protocols
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SUMMARYCharacteristics of On-Demand Routing
Protocols
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SUMMARYCharacteristics of On-Demand Routing
Protocols
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SUMMARYCharacteristics of On-Demand Routing
Protocols
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Implementation Issues

• Several implementations apparently exist (see
  IETF)
• only a few available publicly
• Where to implement ad hoc routing?
• Link layer, Network layer, Application layer
• Address assignment
• Restrict all nodes to be on the same subnet
• Nodes may be given random addresses
• How to assign addresses? DHCP for ad hoc network?
• Security
• How can I trust you to forward my packets without
  tampering?
• How do I know you are what you claim to be ?
• Performance
• Can we make any guarantees on performance?

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References

• 1 D. B. Johnson, D. A. Maltz, Y.-C. Hu, The
  Dynamic Source Routing Protocol for Mobile Ad Hoc
  Networks (DSR), IETF Draft, April 2003.
• 2 C. E. Perkins, E. M. Belding-Royer, Ian D.
  Chakeres, Ad hoc On-Demand Distance Vector
  (AODV) Routing, IETF Draft, January 2004.
• 3 Z. J. Haas, M. R. Pearlman, P. Samar, P.,
  The Zone Routing Protocol (ZRP) for Ad Hoc
  Networks IETF Internet Draft, draft-ietf-manet-zo
  ne-zrp-04.txt, July 2002.
• 4 V. Park, S. Corson,Temporally-Ordered
  Routing Algorithm (TORA), IETF Draft,
  draft-ietf-manet-tora-spec-03.txt, work in
  progress, June 2001.
• 5 P. Sinha, R. Sivakumar, and V. Bharghavan,
  "CEDAR A CoreExtraction Distributed Ad
  HocroutingAlgorithm," Proc. IEEE INFOCOM '99,
  Mar. 1999.