Xiuzhen Cheng [e-mail]

1
Xiuzhen Cheng
cheng_at_gwu.edu
Csci388 Wireless and Mobile Security A Survey
on Ad Hoc Routing Protocols
2
Outline

• Introduction
• Topology-based routing
• Proactive Hybrid Protocols
• DSDV/WRP/GSR/FSR/LAR
• ZRP
• Reactive Protocols
• DSR/AODV/TORA/ABR/ASR
• Location-based routing

3
Mobile Ad-Hoc Network

• Collection of mobile nodes forming a temporary
  network
• No centralized administration or standard support
  services
• Each Host is an independent router
• Hosts use wireless RF transceivers as network
  interface

• Conferences/Meetings
• Search and Rescue
• Disaster Recovery
• Automated Battlefields

4
MaNet Issues

• Lack of a centralized entity
• Network topology changes frequently and
  unpredictably
• Channel access/Bandwidth availability
• Hidden/Exposed station problem
• Lack of symmetrical links
• Power limitation
• Multipath Fading
• Doppler Effect

5
MaNet Protocols Topology Based

• Proactive Protocols
• Table driven
• Continuously evaluate routes
• No latency in route discovery
• Large network capacity to keep info. current
• Most routing info. may never be used!

• Reactive Protocols
• On Demand
• Route discovery by some global search
• Bottleneck due to latency of route discovery
• Link breakage may not affect on-going traffic not
  in its vicinity

6
Conventional Routing Protocols

• DBF (DV) shows a degradation in performance
• Knows the distance to its neighbors and a
  distance vector.
• Broadcasts its distance vector to all of its
  neighbors periodically
• When receiving the distance vector from its
  neighbors, the router computes the estimated
  distance to all other routers
• Slow convergence due to Count to Infinity
  Problem
• Creates loops during node failure, network
  partition or congestion
• Link State create excessive traffic and control
  overhead
• Learn the neighbors network address Measure the
  cost to each neighbor Construct a packet telling
  all that just learnt Flood this packet to all
  other routers Compute the shortest path to every
  other router

7
MaNet Protocol Considerations

• Simple, Distributed, Reliable and Efficient
• Quickly adapt to changes in topology and traffic
  pattern
• Protocol reaction to topology changes should
  result in minimal control overhead
• Bandwidth efficient
• Mobility Management involving user location
  management and Hand-off management
• Security

8
DSDV Perkins et al 1994

• Improved Classical Bellman-Ford (DV) Routing
  Algorithm
• Routing Table
• Dest id of Hops Dest Seq. Next Hop
• Update messages broadcasted to neighbors
• Full dump packets (time-driven) complete routing
  table
• Incremental packets (event-driven) modified
  entries
• Each packet routing table broadcast seq.
• In a relatively stable network, full dump is
  infrequent compared to a fast-changing network
• Timer settling time of routes or weighted
  average time
• -- delay the broadcast of the routing updates

9
DSDV Cont.

• Responding to topology changes
• Broken links indicated by ?
• Any route through a hop with a broken link is
  also assigned ?
• ? routes are immediately broadcasted
• Sequence number of Destination with ? hops is
  incremented by 1
• Nodes with same or higher sequence number and
  finite metric broadcast their route information
• Route Selection Criteria
• Loop-free most recent seq. , best metric - of
  hops
• Route broadcast are asynchronous events
  Fluctuations are caused due to possibility of
  receiving routes with worse metric first
• Solution is to maintain two routing tables, one
  for routing and one for incremental broadcast

10
Clusterhead Gateway Switch RoutingProtocol
(CGSR) Chiang 97

• Cluster-head election
• Least Cluster Change (LCC)
• Two tables
• Cluster member table mapping from each node to
  its CH
• Routing table next hop to reach the destination
  CH
• Broadcast update message for both tables
  periodically using DSDV algorithm
• Packet routing (example)

Routing from node 1 to node 8
11
Wireless Routing Protocol (WRP)

• A path-finding algorithm
• Utilizes information regarding the length and the
  predecessor-to-dest in the shortest path to each
  destination
• Eliminates the Count to Infinity Problem and
  converges faster
• An Update message is sent after processing
  updates from neighbors or a change in link to a
  neighbor is detected
• Each route update from neighbor k causes route
  entries of other neighbors that use k to be
  re-computed

12
The Algorithm

• Each node i maintains a Distance table (iDjk),
  Routing table (Destination Identifier, Distance
  iDj , Predecessor Pj ,the successor Sj), link
  cost table (Cost, Update Period), Message
  Retransmission List (MRL)
• Update message ltsender id, seq, update list or
  ACK, response listgt
• Processing Updates and creating Route Table based
  on new information
• Update from k causes i to re-compute the
  distances of all paths with k as the predecessor
• For a destination j, a neighbor p is selected as
  the successor if p-gtj does not include i, and is
  the shortest path to j

13
WRP Example
14
Global State Routing (GSR) Chen et al 98

• Combination of DV and LS
• Global Network Topology stored in a Table
• Topology Table broadcast to immediate neighbors
  only
• Each node maintains
• A neighbor list A topology table ltlink-state
  information its timestamp per destinationgt A
  next hop table ltnext hop per destinationgt A
  distance table ltshortest distance to each destgt.
• Update message
• Link State/Changes updates are time triggered
• Updates topology table, reconstructs routing
  tables, broadcasts new information.

15
Advantages/Disadvantages of GSR

• Advantages
• Avoids Flooding for disconnects/reconnects
• Updates are time triggered than event triggered
• Greatly reduces control overhead
• Disadvantages
• Hogs bandwidth since entire topology table is
  broadcast with each update
• Link state latency depends on update interval
• Can GSR be modified to rectify its drawbacks ?

16
Fisheye State Routing (FSR) Iwata et at 99

• Improvement over GSR.
• The network is logically divided into Fisheye
  circles with respect to each node. The scope of
  the circle may be defined in terms of number of
  hops
• Smaller update message size thus less bandwidth
  usage
• Each node gets accurate information about its
  neighbors the accuracy decreases as the distance
  increases
• Packets are routed correctly
• The closer the packet to the dest., the more
  accurate the route information

The scope of fisheye for the center red node
17
Hierarchical State Routing (HSR) Iwata et al
99

• featured by
• multilevel clustering and logical partitioning of
  mobile nodes
• Hierarchical clustering
• Physical level link state exchange inside each
  cluster Clusters information exchange via
  gateways
• Each node has hierarchical topology information
• Routing information flows from higher-level to
  lower-level
• Hierarchical address
• lthierarchical cluster gt

2
7
C-21
C-11
4
C-12
2
7
5
C-02
lt1,1,1gt
4
lt2,3,8gt
1
3
6
8
C-01
2
7
C-03
Gateway
Cluster head
Node
18
Zone-based Hierarchical Link State Routing
Protocol (ZHLS) Joa-Ng et al 99

• Non-overlapping zones
• Two topology levels zone level and node level
• Node address ltzone id, node idgt
• Two types of link state packets (LSP)
• Node LSP contains neighborhood information,
  propagates within the zone
• Zone LSP contains zone information, propagates
  globally
• Each node knows full intra-zone node connectivity
  and inter-zone connectivity information
• How a package is routed?
• Based on its zone id and node id

19
Zone Routing Protocol

• A Hybrid Routing Protocol
• A Zone is defined for each node
• Proactive maintenance of topology within a zone
  (IARP)Distance Vector or Link State
• Reactive query/reply mechanism between zones
  (IERP) With Route Caching Reactive Distance
  Vector W/O Route Caching Source Routing
• Uses Bordercast instead of neighbor broadcast
• Neighbor Discovery/Maintenance (NMD) and Border
  Resolution Protocol (BRP) used for query control,
  route accumulation etc.

20
ZRP Example
1 Hop
2 Hops
Multi Hops
B
F
A
C
D
E
G
H
21
Zone Routing Protocol cont.

• Routing Zone and IntrAzone Routing Protocol
• Zone Radius may be based on hop count
• Identity and distance of each Node within the
  Zone is proactively maintained
• The Interzone Routing Protocol
• Check if destination is within the routing zone
• Bordercast a route query to all peripheral nodes
• Peripheral nodes execute the same algorithm

22
Zone Routing Protocol cont.

• Route Accumulation
• Provide reverse path from discovery node to
  source node
• May employ global caching to reduce query packet
  length
• Query Detection/Control
• Terminate Query thread in previously queried
  regions
• Intermediate nodes update a Detected Queries
  TableQuery Source, ID
• Route Maintenance may be reactive or proactive

23
Ad-Hoc On-Demand Distance Vector Routing

• Protocol overview and objectives
• Path Discovery
• Reverse Path Setup
• Forward Path Setup
• Route Table Management
• Path Maintenance
• Local Connectivity Management

24
Protocol Overview and Objectives

• Pure on-demand protocol
• Node does not need to maintain knowledge of
  another node unless it communicates with it
• Routes are discovered on an as-needed basis and
  are maintained only as long as they are necessary
• Broadcast discovery packets only when necessary
• Distinguish between local connectivity and
  general topology maintenance
• To disseminate Information about changes in local
  connectivity to those neighboring nodes that are
  likely to need it

25
Route Establishment

• Initiated whenever nodes want to communicate
• Route discovery
• RREQ lt source addr, source seq , broadcast id,
  dest addr, dest seq, hop cnt gt
• RREP ltsource addr, dest addr, dest seq,
  lifetimegt
• Route tableltdest addr, dest seq, next hop,
  precursors, lifetimegt

7
7
2
2
5
5
s
s
1
3
1
3
d
d
8
8
4
6
4
6
Path taken by RREP
Propagation of RREQ
26
Route Discovery

• Reverse Path Setup when process up-to-date RREQ
• Reverse route entry in the route table ltsource
  addr, source seq, hops to source, addr of node
  from which RREQ is received, lifetimegt
• Source sequence number is used to maintain
  freshness about reverse route to source
• Forward Path Setup when process valid RREP
• Forward path entry in the route table ltdest
  addr, addr of node from which RREP is received,
  hops to dest, lifetimegt
• Destination sequence number specified for
  freshness of route before accepted by source

27
Route Maintenance

• Route Table Management
• Route Request Expiration Timer for purging
  reverse paths which do not lie on
  source-destination route
• Route Caching Timeout after which the route is
  considered invalid
• Active_timeout Period used to determine if
  neighboring node is active
• Active Path Maintenance
• If source move causes path breakage, source
  re-establish route discovery by RREQ
• If intermediate or destination move causes path
  breakage, RERR is initiated by the node upstream
  of the break and sent to all affected sources.
  How?

28
Dynamic Source Routing

• Overview
• Constructs a source route in packet header
  listing source route
• Each host maintains a route cache
• Route discovery used for routes not in cache
• Route discovery build route record
• Route request initiator, target, route record,
  unique id
• Intermediate node appends its address
• Destination/intermediate node sends route reply
  with route record

7
7
2
2
lt1gt
lt1,2gt
lt1,3,5gt
5
5
lt1,3,5,7gt
s
s
1
3
1
3
lt1,3gt
lt1gt
lt1,4,6gt
lt1,4,6gt
d
d
8
8
lt1gt
lt1,4gt
lt1,4,6gt
4
6
4
6
lt1,4,6gt
Route reply with route record
Building route record
29
Route Maintenance and Route Cache

• Route Maintenance
• Route error packet sent on detection of break
  containing addresses on both sides of error, the
  host that detected the error and the host to
  which it was trying to send the packet
• All upstream node then deletes routes with that
  particular hop
• Route Cache
• Each forwarding host can add route information to
  cache
• Nodes can operate in promiscuous mode and add
  information to cache from any packets that they
  hear
• Each intermediate node having a route can send a
  route reply packet

30
Performance Comparison of AODV and DSR

• DSR has access to significantly greater amount of
  routing information than AODV by virtue of source
  routing and promiscuous listening
• DSR replies to all requests reaching a
  destination from a single request cycle whereas
  AODV only replies once thereby learning only one
  route
• In DSR no particular mechanism to delete stale
  routes, unlike AODV
• In AODV the route deletion causes all the nodes
  using that link to delete it, but in DSR only
  the nodes on that particular part are deleted

31
Temporally Ordered Routing Algorithm (TORA) Park
et al 97

• Based on the concept of link reversal
• Highly adaptive, efficient, scalable, distributed
  algorithm
• Multiple routes from source to destination
• For highly dynamic mobile, multi-hop wireless
  network
• Routing Mechanism
• Unique node ID and unique reference ID
• Route creation QRY (dest id) and UPD (dest id,
  Hi) packets
• Route maintenance
• Route erasure Clear packet (CLR) is broadcasted

32
TORA Cont.
(-,-)
(0,1)
(-,-)
(0,3)
7
7
2
2
5
5
(0,2)
s
s
(-,-)
1
3
1
3
(-,-)
(0,3)
(0,3)
(-,-)
d
d
8
8
(0,0)
(0,0)
4
6
4
6
(-,-)
(-,-)
(0,2)
(0,1)
Propogation of QRY (reference level, height)
Height of each node updated by UPD
Route Creation in TORA
33
TORA Cont.
(0,1)
(1,-1)
7
2
5
(1,0)
s
1
3
(0,3)
(1,-1)
d
8
(0,0)
4
6
(0,2)
(0,1)
Re-establishing route in link failure
34
Associativity Based Routing (ABR) Toh 96 99

• New metric degree of association stability
• Beacons periodically sent to its neighbors
• Updates the associativity table
• Association stability means connection stability
• Associativity ticks reset
• Route is long-lived and free from loops,
  deadlock, and packet duplicates
• The protocol contains 3 phases
• Route discovery BQ-REPLY cycle
• Route reconstruction (RRC)
• Route deletion (RD) Source-initiated

35
ABR (cont.)
36
Signal Stability Routing (SSR) Dube et al 97

• New metric signal strength between nodes and a
  nodes location stability
• SSR consists of 2 cooperative protocols Dynamic
  Routing (DRP) Static Routing (SRP)
• DRP is responsible for Signal stability table
  (SST) and Routing table (RT) maintenance Packets
  go through DRP, then SRP SRP forwards packets
  using RT
• Route discovery and route maintenance
• By default, only route request packets from
  strong channels are forwarded
• When link breakage, intermediate nodes send error
  message to source, which then initiates a new
  route-search process and sends erase message to
  erase the old route

37
Comparison
Parameter Table-driven On-demand
Availability Always When needed
Route update periodic N/A
Message load higher lower
Power higher lower
Storage higher lower
Bandwidth higher lower
Scalability Better
Mobility support Better
QoS support ??? ???
38
Challenges in Ad-hoc Design

• Protocols still in Nascent Stage, analysis for
  which protocol does well in which scenario
• QOS issues in Ad-hoc
• TCP performance over Ad-hoc
• Security in ad hoc routing
• Integration of Ad-Hoc Networks in Internet
• Multicasting in Ad-hoc Networks

39
Position-based routing protocols - Characteristics

• Uses additional information physical location of
  nodes.
• Position of oneself determined by GPS or the
  like.
• Position of destination node by a location
  service
• Routing decision based on
• Position of destination node
• Position of neighboring nodes
• No need to store routing tables.
• Geocasting is possible.
• Location Services
• Centralized location service like cellular
  networks impossible!
• How to position a server? Chicken-and-egg
  problem.
• Dynamic topology no server nearby

40
Position-based routing

• To find the position of the destination
• Location service some-for-some some-for-all
  all-for-some all-for-all
• Each node knows the position of its neighbors and
  itself through periodic beacon broadcast
• Packet forwarding strategy
• Greedy forwarding and Restricted directional
  flooding (next hop selection and recovery
  strategy)
• These two try to send a packet to a closer node
• Recovery strategies for reaching local maximum
• hierarchical approaches
• Greedy forwarding local non-position-based
  routing
• Good scalability

41
DREAM

• Distance Routing Effect Algorithm for Mobility
  framework (DREAM)
• Decentralized All-for-all approach
• All nodes hold positions of all nodes
• Each entry contains ones information about
  direction, distance, and timestamp
• Each node controls accuracy
• Temporal resolution frequency
• Spatial resolution of hops update packets leap
• Not accurate at the long distance
• Because of distance effect, this is reasonable
  (see next slide)

42
Distance Effect

• The greater the distance between two nodes,
• The slower the ratio of changes in position
• In the picture, A which is fixed sees B and C
  which is moving

43
Quorum-based Location Service

• Concept from quorum systems in databases and
  distributed computing.
• Quorum-Based Location Service
• Virtual backbone contains a small subset of
  nodes
• A quorum is a small subset of the backbone nodes
• The intersection of any two quorums is non-empty
• Location update in one quorum, location query in
  another quorum
• Some-for-some approach
• Most recent-timestamped one
• Tradeoff between
• The size of a quorum
• Resilience of reachability.

44
Grid Location Services (GLS)

• The area is divided into hierarchical squares,
  forming a quadtree
• Near node (ID) the least greater than its own
  ID
• Floods to all nodes in the first-order square,
  nearest node in nearby 3-squares
• Again, floods near node in the nearby 3
  next-order squares until the highest level.
• Density of information decreases logarithmically
  as distance increases (see next slide for an
  example)

45
Grid Location Services (GLS) - Example
46
Homezone

• Similar to the cellular phone network
• Phone moves to another region it sends
  periodically position info. to the home agent
• Home agent forwards call to the new agent to the
  phone
• Each virtual zone for each node
• Defined by Hash(nodeID) no contact to the
  destination node
• All nodes within a circle centered at a node
  must maintain position information for the node
• All-for-some approach

47
Greedy Packet Forwarding

• Most Forward Within R (MFR) nearest to dest.
  Node C
• Nearest with Forward Progress (NFP) nearest to
  src. Node A
• Minimize ?pf(a,b)
• p prob. of succ.trans.
• f(a,b) progress from a to b.
• Compass routing closest to the straight line S
  to D. Node B
• Minimize spatial travel dist.
• Randomly choosing anything closer to dest.
• Less accurate position info.
• Less computation.

S Source D Destination Circle indicates
neighborhood
48
Greedy Packet Forwarding (cont.)

• Failure case local maximum
• Selecting least backward progress can lead to a
  loop
• Simply, dont forward
• Face-2 algorithm and the perimeter routing
  strategy of the Greedy Perimeter Stateless
  Routing Protocol (GPSR)
• Per packet basis (more info in it)
• Enters into recovery mode
• Returns into greedy mode when the packet reaches
  a node closer to the destination than the node
  when it enters into recovery mode.
• Guarantees find path to destination if there is
  one.

• Planar graphs
• No edges crossing each other
• Right hand rule for a traversing a graph

49
Planar graph

• Planar sckeme uses
• Right-hand rule
• No crossing heuristic
• Parameter Probing

50
Perimeter Forwarding
51
Restricted Directional Flooding (RDF)

• Distance Routing Effect Algorithm for Mobility
  framework (DREAM)
• Send to all nodes within direction
• Radius of (t1-t2)vmax
• If no one-hop neighbor in the direction,
  recovery procedure starts
• Location Aided Routing
• An aid to route discovery of a reactive routing
• Put rectangle points into the packet
• Route request is proceeded at a node when it is
  in the area

52
Location Aided Routing (LAR)

• A Modified Flooding Algorithm
• Utilizes location information of mobile hosts
  using a GPS for route discovery
• Flooding is restricted to a request zone,
  defined by an expected zone
• A node forwards a route request only if it
  belongs to the request zone
• Tradeoff between latency of route determination
  and message overhead
• Resorts to flooding when prior information of
  destination is not available

53
LAR Schemes
D(xd,yd)
D(xd,yd)
R v(t-t0)
N
I
N
I
J
J
S (xs,ys)
S (xs,ys)
Scheme 1
Scheme 2
54
LAR cont.

• Scheme 1.
• Source calculates the expected zone, defines a
  request zone in the request packet and initiates
  route discovery
• Node I receiving the route request forwards the
  request if it falls inside the request zone,
  otherwise discards it
• When destination receives the request, replies
  with a route reply including current location,
  time and average speed
• Size of request zone is large at low and high
  node speeds because it is proportional to
  elapsed time and speed

55
LAR cont.

• Scheme 2.
• Source calculates the distance Dists to
  destination (xd, yd) and initiates route
  discovery with both parameters
• Node I calculates its distance Disti from (xd,
  yd) and forwards the request only if Distilt
  Dists d, otherwise discards the request
• Node I replaces Dists with Disti before
  forwarding the request
• None zero d increases probability of route
  discovery

56
Hierarchical routing

• Terminodes routing proactive greedy
  position-based
• Put positions on the way into the packet.
• Get positions by contact others
• Has reactive ad hoc routing property
• Grid Routing position-aware node (acts like
  proxy) with position-unaware nodes
• Intermediate Node Forwarding (INF) repair for
  greedy long-distance routing
• If local maximum, discard packet, send
  notification.
• Sender select a position within a circle centered
  at the middle of the SD line
• If fail again, enlarge the circle until
  pre-specified number of repeatings

57
Comparison
58
Comparison (cont.)
59
Future Research on Position-Based Routing

• Quantitative analysis and comparison of all these
  strategies/techniques
• Harsh in GLS and HomeZone may not applicable in
  high dynamic environment. Probabilistic method?
• Location privacy in location service
• Refine greedy packet forwarding
• Hierarchical routing to connect to internet

60
Homework

• To be Presented by Michael Clifford Michael
  Clifford, Networking in the Solar Trust Model
  determining optimal trust paths in a
  decentralized trust network, 18th Annual Computer
  Security Applications Confrence, December 9-13,
  2002, Las Vegas, Nevada,
• To be Presented by Fang Liu Yih-Chun Hu, Adrian
  Perrig, and David B. Johnson, Rushing Attacks and
  Defense in Wireless Ad Hoc Network Routing
  Protocols, Proceedings of the 2003 ACM Workshop
  on Wireless Security (WiSe 2003), pp. 30-40, ACM,
  San Diego, CA, September 2003.
• Submit Report Yih-Chun Hu, Adrian Perrig, David
  B. Johnson, Ariadne A Secure On-Demand Routing
  Protocol for Ad Hoc Networks, MobiCom 2002.