Introduction to Wireless Ad-Hoc Networks Routing

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Introduction to Wireless Ad-Hoc Networks Routing

• Michalis Faloutsos
• Some slides borrowed
• From Guor-Huar Lu

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Outline

• Challenges
• Design Goals Specified by MANET (for now)
• Types of Routing
• Protocols in Detail
• Conclusion

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Challenges

• Dynamic Topologies
• Bandwidth-constrained, variable capacity links
• Energy-constrained
• Limited Physical security
• Scalability

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Types of routing

• Flat Proactive Routing
• Link state Fish-Eye Routing, GSR, OLSR.
• Table driven Destination-Sequenced Distance
  Vector (DSDV), WRP)
• On-Demand or Reactive Routing
• Ad hoc On-demand Distant Vector (AODV)
• Dynamic Source Routing (DSR)
• Hybrid Schemes
• Zone Routing ZRP, SHARP (proactive near, reactive
  long distance)
• Safari (reactive near, proactive long distance)
• Geographical Routing
• Hierarchical One or many levels of hierarchy
• Routing with dynamic address
• Dynamic Address RouTing (DART), L

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Proactive Protocols

• Proactive maintain routing information
  independently of need for communication
• Update messages send throughout the network
  periodically or when network topology changes.
• Low latency, suitable for real-time traffic
• Bandwidth might get wasted due to periodic
  updates
• They maintain O(N) state per node, N nodes

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On-Demand or Reactive Routing

• Reactive discover route only when you need it
• Saves energy and bandwidth during inactivity
• Can be bursty -gt congestion during high activity
• Significant delay might occur as a result of
  route discovery
• Good for light loads, collapse in large loads

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Hybrid Routing

• Proactive for neighborhood, Reactive for far away
  (Zone Routing Protocol)
• Proactive for long distance, Reactive for
  neighborhood (Safari)
• Attempts to strike balance between the two

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Hierarchical Routing

• Nodes are organized in clusters
• Cluster head controls cluster
• Trade off
• Overhead and confusion for leader election
• Scalability intra-cluster vs intercluster
• One or Multiple levels of hierarchy

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The effect of hierarchy

• Consider a protocol of f(N) complexity
• If we apply it in a two level hierarchy with C
  clusters
• Complexity within clusters f(Nc)
• Complexity between clusters f(N/Nc)
• How should we pick cluster sizes?
• Does a two-level hierarchy work?

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Geographical Routing

• Nodes know their geo coordinates (GPS)
• Route to move packet closer to end point
• Protocols DREAM, GPSR, LAR
• Propagate geo info by flooding (decrease
  frequency for long distances)

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Geographical Routing

• Knowing GPS coordinates
• Pick next hope based on angle of deviation
• Consider other params
• Distance of next hop
• Congestion
• Reliability
• Q How do you know location of destination?

destination
source
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Dynamic Routing a new approach

• DART Ericsson et al., L Morris et al
• Goal can we enforce address aggregation
• But nodes are moving
• Then address should change

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Dynamic Routing general idea

• Separation of identity and address
• Identity is who you are
• Address is where you are
• Rule for enforcing structure in addresses
• near by nodes should have nearby addresses
• Using the Rule, we can aggregate information

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DART in more detail

• Basic idea permanent nodeID / transient
  address
• The address reflects network location
• It is a proactive routing scheme, distance vector
• Consequences
• Routing is simplified address tell me where you
  are
• Nodes with similar addresses are near each
  other
• Challenges
• Address allocation When I move, change my
  address
• ID to Address mapping Given an ID, find the
  address

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Some more theoretical issues
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Network Capacity

• The optimal capacity of a wireless
• network is
• Where N nodes, and C channel
• capacity
• Gupta Kumar paper The capacity of wireless
  networks
• What other assumptions do I need?

• Transmission range as small as I need to
• Who talks to whom? Random selection

Non optimal traffic patterns and fixed
transmissions then throughput is O(C/ sqrt(N
log N))
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Intuitive Explanation

• Explanation N nodes in the field
• Destinations are random
• On average N0.5 hops per path
• Each node has N0.5 paths go through

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Mobility increases capacity

• Grossglausser and Tse (infocom 2001)
• Statement if nodes move they will eventually
  carry the info where you want
• Protocol
• sender send one copy to receiver or one neighbor
• Sender and relay will at some run into
  destination and send the packet
• All paths are at most two hops
• They show that the capacity of the network does
  not go to zero
• Tradeoff?

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Hierarchical routing bounds

• Cluster nodes, and route between and within
  clusters
• Location management finding where is the node
• Routing finding how to get there
• Multiple levels log(N) levels
• Location Mgm Each nodes stores O(N) locations
• Routing overhead O(log3N)
• Dominating factor location management and not
  the routing
• Location mgmt handoff O(log2N)
• See Susec Marsic, infocom 02

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Types of routing

• Flat Proactive Routing
• Link state Fish-Eye Routing, GSR, OLSR.
• Table driven Destination-Sequenced Distance
  Vector (DSDV), WRP)
• On-Demand or Reactive Routing
• Ad hoc On-demand Distant Vector (AODV)
• Dynamic Source Routing (DSR)
• Hybrid Schemes
• Zone Routing ZRP, SHARP (proactive near, reactive
  long distance)
• Safari (reactive near, proactive long distance)
• Geographical Routing
• Hierarchical One or many levels of hierarchy
• Routing with dynamic address
• Dynamic Address RouTing (DART)

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Proactive DSDV - Destination-Sequenced Distance
Vector Algorithm

• By Perkins and Bhagvat
• Based on Bellman Ford algorithm
• Exchange of routing tables
• Routing table the way to the destination, cost
• Every node knows where everybody else is
• Thus routing table O(N)
• Each node advertises its position
• Sequence number to avoid loops
• Maintain fresh routes

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DSDV details

• Routes are broadcasted from the receiver
• Nodes announce their presence advertisements
• Each broadcast has
• Destination address originator
• No of hops
• Sequence number of broadcast
• The route with the most recent sequence is used

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Reactive Ad-Hoc On-demand Distance Vector
Routing (AODV)

• By Perkins and Royer
• Sender tries to find destination
• broadcasts a Route Request Packet (RREQ).
• Nodes maintain route cache and use destination
  sequence number for each route entry
• State is installed at nodes per destination
• Does nothing when connection between end points
  is still valid
• When route fails
• Local recovery
• Sender repeats a Route Discovery

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Route Discovery in AODV 1
Propagation of Route Request (RREQ) packet
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Route Discovery in AODV 2
Path taken by Route Reply (RREP) packet
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In case of broken links

• Node monitors the link status of next hop in
  active routes
• Route Error packets (RERR) is used to notify
  other nodes if link is broken
• Nodes remove corresponding route entry after
  hearing RERR

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Dynamic Source Routing (DSR)

• Two mechanisms Route Maintenance and Route
  Discovery
• Route Discovery mechanism is similar to the one
  in AODV but with source routing instead
• Nodes maintain route caches
• Entries in route caches are updated as nodes
  learn new routes.
• Packet send carries complete, ordered list of
  nodes through which packet will pass

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When Sending Packets

• Sender checks its route cache, if route exists,
  sender constructs a source route in the packets
  header
• If route expires or does not exist, sender
  initiates the Route Discovery Mechanism

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Route Discovery 1 (DSR)
Building Record Route during Route Discovery
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Route Discovery 2 (DSR)
Propagation of Route Reply with the Route Record
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Route Maintenance

• Two types of packets used Route Error Packet and
  Acknowledgement
• If transmission error is detected at data link
  layer, Route Error Packet is generated and send
  to the original sender of the packet.
• The node removes the hop is error from its route
  cache when a Route Error packet is received
• ACKs are used to verify the correction of the
  route links
• Nodes use caching to reduce overhead.

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The Zone Routing Protocol (ZRP)

• Hybrid Scheme
• Proactively maintains routes within a local
  region (routing zone)
• Also a globally reactive route query/reply
  mechanism available
• Consists of 3 separate protocols
• Protocols patented by Cornell University!

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Intrazone Routing Protocol

• Intrazone Routing Protocol (IARP) used to
  proactively maintain routes in the zone.
• Each node maintains its own routing zone
• Neighbors are discovered by either MAC protocols
  or Neighbor Discovery Protocol (NDP)
• When global search is needed, route queries are
  guided by IARP via bordercasting

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Interzone Routing Protocol

• Adapts existing reactive routing protocols
• Route Query packet uniquely identified by
  sources address and request number.
• Query relayed to a subset of neighbors by the
  bordercast algorithm

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Comparisons 1

• Things in common
• IP based operation
• Distributed operation
• Loop-free routing
• Very little or no support for sleep period
  operation and security

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Comparisons 2
DSDV
FSR AODV DSR ZPR
Source Routing No No Yes No
Periodic message Yes No No Yes (Locally)
Functioning Proactively Yes No No Yes (Locally)
Functioning Reactively No Yes Yes Yes (Globally)
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Performance?

• End-to-end data throughput and delay
• Route acquisition time
• Percentage of out-of-order delivery
• Efficiency
• Average number of data bits transmitted/data bits
  delivered
• Average number of control bits transmitted/data
  bits delivered
• Average number of control and data packets
  transmitted/data packet delivered

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Parameters

• Network Size
• Channel properties
• Connectivity (average degree of a node)
• Topology rate of change
• Link capacity (bps)
• Directionality Fraction of unidirectional links
• Traffic patterns who talks to whom
• Mobility
• Fraction/frequency of sleeping nodes

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References

• Mobile Ad hoc Networking (MANET) Routing
  Protocol Performance Issues and Evalution
  Considerations (RFC 2501)
• P. Misra., Routing Protocols for Ad Hoc Mobile
  Wireless Networks, http//www.cis.ohio-state.edu/
  jain/cis788-99/adhoc_routing/
• The Zone Routing Protocol (ZRP) for Ad Hoc
  Networks ltdraft-ietf-manet-zone-zrp-04.txtgt
• Fisheye State Routing Protocol (FSR) for Ad Hoc
  Networks ltdraft-ietf-manet-fsr-03.txtgt
• Ad hoc On-demand Distance Vector (AODV) Routing
  ltdraft-ietf-manet-aodv-11.txtgt
• The Dynamic Source Routing Protocol for Mobile Ad
  Hoc Networks (DSR) ltdraft-ietf-manet-dsr-07.txtgt

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Conclusion

• On-demand routing protocols (AODV and DSR) are
  well established.
• More analysis and features are needed
  (Performance comparison between protocols, QoS
  extension and analysis, multicast, security
  issues etc)
• Good paper (though old)
• A review of current routing protocols for ad-hoc
  mobile wireless networks, E. Royer, C.K. Toh
• Routing Scalability in MANETs, Eriksson et al.
  Book chapter,
• http//www.cs.ucr.edu/michalis/COURSES/240-08/lec
  tures/bookchapter.pdf

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Fisheye State Routing (FSR)

• Node stores the Link State for every destination
  in the network
• Node periodically broadcast update messages to
  its neighbors
• Updates correspond to closer nodes propagate more
  frequently

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Multi-Level Scope (FSR)

• Central node (red dot) has the most accurate
  information about nodes in white area and so on.
• Parameters Scope level/radius size

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ZPR architecture
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Design Goals

• Peer-to-peer mobile routing capability in mobile,
  wireless domain.
• Intra-domain unicast routing protocol
• Effective operation over a wide range of mobile
  networking scenarios and environments
• Supports traditional, connectionless IP services
• Efficiently manages topologies changes and
  traffic demands

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Desired properties

• Distributed operation
• Loop freedom
• Demand-based operation
• Proactive operation
• Security
• Sleep period operation
• Unidirectional link support