Security within Ad hoc Networks

1
Security within Ad hoc Networks
2
References

• Security within Ad hoc Networks Position Paper,
  PAMPAS Workshop, Sept. 16/17 2002, London,Author
  Preetida Vinayakray-Janipreetida.vinayakray-jani_at_n
  okia.com,Nokia Research Center, Helsinki, Finland
• Securing Ad Hoc Routing Protocols, Isameldin
  Suliman, isam_at_ee.oulu.fi, Centre for Wireless
  Communications, University of Oulu, Finland
• Routing Mechanisms in Ad-Hoc Networks, Giwon
  Park, TeNet
• Introduction to Ad Hoc Networking, Yu-Chee Tseng
• Jean-Pierre Hubaux, Levente Buttyan and Srdan
  Capkun, The Quest for Security in Mobile Ad hoc
  Networks, Proceedings of the ACM Symposium on
  Mobile Ad hoc Networking and Computing, MobiHOC
  2001
• L. Zhou and Z.J. Haas, Securing Ad hoc
  Networks, IEEE Networks, 13(6) 24-30, Nov/Dec
  1999
• 3GPP, 3G Security Security Architecture, 3GPP
  TS 33.102, V3.6.0, Oct. 2000
• Scalable Routing Protocols for Mobile Ad Hoc
  Networks, Xiaoyan Hong, Kaixin Xu, and Mario
  Gerla at UCLA

3
Network Architecture

• No Infrastructure (ad hoc networks)
• no base stations no fixed network infrastructure

4
Model of Operations
5
MANET

• MANET Mobile Ad Hoc Networks
• multi-hop communication
• needs support of dynamic routing protocols

6
Ad Hoc Network

• Every node must be self-organized and autonomous
• Autonomously establish a route to different
  destination node and dynamically maintain the
  route by itself
• Every node may act as both a host and a router
• A multi-hop network
• Nodes communicate with each other within radio
  range through direct wireless links or multi-hop
  routing

7
Application

• Military battlefield
• Ad hoc Conference
• Home networking
• Emergency services
• Personal Area Network (PAN)

8
Application

• Intelligent Transportation System
• may be integrated with cars, positioning devices,
  etc.
• Sensor Dust
• a large collection of tiny sensor devices
• once situated, the sensors remain stationary
• largely homogeneous
• power is likely to be a scarce resource, which
  determines the lifetime of the network
• can offer detailed information about terrain or
  environmental dangerous conditions.

9
Ad Hoc Network - Characteristics

• Dynamic topologies
• Bandwidth constrained, variable capacity links
• Energy constrained operation
• Limited physical security
• Scalability

10
Ad Hoc Network - Characteristics

• Protocol deployment and incompatible standards
• Unless a miracle happens (e.g., the IETF manet
  working group is able to promulgate a widely
  deployed ad hoc networking protocol), ad hoc
  networks will gain momentum only gradually
  because users will have to load software or take
  additional steps to ensure interoperability.
• Wireless data rate
• e.g., TCP over multi-hop wireless links
• Security issues

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IETF MANET Working Group

• Goal
• Standardize IP routing Protocol functionality
  suitable for wireless routing application within
  both static and dynamic topologies with increased
  dynamics due to node motion or other factors.
• A dozen candidate routing protocols have been
  proposed.

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Examples of Ad Hoc Network
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(No Transcript)
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Nokia Rooftop Product
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Nokia RoofTop

• RoofTop solution (Nokia, Finland)
• Wireless router
• a radio frequency (RF) modem
• a digital Internet protocol (IP) router

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FHP

• FHP Wireless, USA
• ad hoc network in a campus

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FHP Wireless
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FHP Wireless
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MeshNetworks

• MeshNetworks, USA

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System MeshNetworks

• Architecture

21
Networking Scenario To Internet
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SkyPilot NeighborNet

• SkyPilot Network, USA

23
Security Goals

• Availability Ensures the survivability of
  network services despite denial-of-service
  attacks
• Confidentiality
• Integrity
• Authentication Enables a node to ensure the
  identity of the peer node with which it is
  communicating
• Non-repudiation

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SECURITY Challenge

• Dynamic Topologies and Membership
• solutions should be dynamic
• Vulnerable wireless link
• Passive/Active link attacks like eavesdropping,
  spoofing, denial of service, masquerading,
  impersonation are possible
• Roaming in dangerous environment
• Any malicious node or misbehaving node can create
  hostile attack or deprive all other nodes from
  providing any service

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KEY ISSUES AND CHALLENGES

• Link Level Security
• An eavesdropper can easily spoof the on going
  communication.
• Any node can become vulnerable to attacks coming
  from any direction or from any node.
• The results of such attacks include
• spoofing of the nodes identity,
• tampering with nodes credentials,
• leaking of confidential information
• impersonating node.
• These types of attacks can easily compromise the
  confidentiality, integrity, and availability and
  privacy of the node.

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KEY ISSUES AND CHALLENGES

• Privacy
• To establish a secure communication link a node
  needs to provide his/her identity as well as
  associated credentials to another node.
• Spoofing of identity or any confidential
  information leads to privacy threat.
• This can be engineered to create DoS attacks.
• Identification problem simultaneously leads to
  privacy problem
• Thus privacy is one of the key issues within ad
  hoc networking.
• Current mobile standards do not provide any
  location privacy.
• In many cases revealing identity is inevitable to
  generate communication link.

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KEY ISSUES AND CHALLENGES

• Key Management
• In centralized key management scheme, the trusted
  Certificate Authority (CA) provides public key
  certificate to mobile nodes.
• Any tampering with CA can easily compromise the
  security of the entire network.
• The proposed mechanisms used for identification
  such as shared secret, public key cryptography,
  third party authentication provide partial
  solution, as they are vulnerable or unable to
  scale.
• All proposed solutions require that the mobile
  users make proper usage of cryptographic keys.
• However goal of proper management and safekeeping
  of small number of cryptographic keys is
  difficult due to random mobility of nodes.

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KEY ISSUES AND CHALLENGES

• Secure Routing
• The routing protocols are more vulnerable to
  attacks as each device acts as a relay5.
• Any tampering with routing information can
  compromise whole network.
• An attacker can insert rogue information within
  routing information or
• Introduce denial of service type attack by
  replaying old logged or stored information.
• Also compromised node can route malicious
  information to other nodes, which can cause
  serious damage.
• The proposed routing solutions are capable to
  operate with dynamic topology but in terms of
  security measure they provide partial or no
  solution 6.
• Thus implementation of secure routing protocol is
  one of the challenges within ad hoc network.

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Key Management Frameworks

• Importance
• Cryptography is powerful tool for security
  service
• Authentication, confidentiality, integrity,
  non-repudiation,
• Goal
• Support the use of public key cryptography.
• Task
• Key generation, distribution, updating.
• Digital certificate issuing, storing, revocation.

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Key Management Frameworks

• Challenges
• Vulnerable mobile nodes
• More exposed to physical attacks.
• Implication must be resilient to node
  compromise.
• Mobility-induced unstable network topology
• Rapid change in connectivity.
• Potential network partition.
• Implication Must be robust to unstable network
  topology.
• Popular Approaches
• (Distributed) PKI.
• Certificate chaining.

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Public Key Infrastructure

• Basic Operation
• Centralized key management.
• Certificate authority (CA) acts as the Trusted
  Third Party.
• Strength
• High assurance because of the existence of trust
  anchor(s).
• Weakness
• CA is a security bottleneck.
• CA is a single point of failure.
• Cost of maintaining the CA infrastructure.

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Certificate Chaining

• Basic Operation
• Peer-to-peer trust model.
• Each node voluntarily issues certificates for
  others.
• Each node collects sufficient certificates and
  maintains a fresh certificate repository.
• Strength
• Fully distributed design, easy to deploy.
• Weakness
• Low security assurance due to lack of trust
  anchors.
• Probabilistic authentication depending on the
  contents of repository.

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Distributed PKI

• Basic Operation
• A distributed quorum/voting system
• Based on threshold cryptography
• CAs private key is split and distributed to m (m
  ? n) nodes.
• Any k (k ? mltn) system key holders can function
  as a virtual CA.
• Strength
• High assurance due to availability of trust
  anchor.
• No single failure point or security bottleneck.
• Challenge
• k Balance of security assurance and success
  ratio.
• Efficient Communications among shareholders.

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Summary Certificate Graph of PKI, Certificate
Chaining and Distributed PKI.
Dan
Fay
CA view
CA2
CA1
CA3
David
Bill
Vin

• All certificates are issued by CA
• Authentication is determined by 1-hop chain.

• No CA in the graph
• May be partition to subgraph
• Authenticate by chain of certificate

• Threshold CAs create CA view
• .Authentication is the same as PKI

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Routing Protocols

• Overview
• Proactive Ad Hoc Routing Protocol
• Reactive Ad Hoc Routing Protocol
• Conclusion

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Routing Protocols Security Requirements

• Import autohrization Only authorize route
  information if it concerns the node that is
  sending the information
• Source authentication Verify that the node is
  the one it claims to be
• Integrity routing information that is being sent
  has arrived unaltered
• The source authentication and integrity combined
  build data authentication

37
Securing Ad Hoc Routing Protocols

• There are two kinds of messages in ad hoc
  networks
• Routing Messages Used for protocol signaling and
  sent to immediate neighbors, processed, possibly
  modified, and resent.
• Data Messages Point-to-point and can be
  protected with any point-to-point security
  mechanism (like IPSec).
• Intermediate nodes need to be able to
  authenticate routing messages.
• Routing messages can be distinguished in two
  types
• Mutable
• Non-mutable

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Overview of Ad Hoc Network Routing Protocol
Ad Hoc routing protocols
Table-driven(Proactive)
DSDV
TBRPF
OLSR
CGSR
Figure 1. Ad Hoc routing protocol
39
Proactive vs. Reactive Routing

• Proactive Routing Protocol
• continuously evaluate the routes
• attempt to maintain consistent, up-to-date
  routing information
• when a route is needed, one may be ready
  immediately
• when the network topology changes
• the protocol responds by propagating updates
  throughout the network to maintain a consistent
  view
• Reactive Routing Protocol
• on-demand
• Ex DSR, AODV

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Proactive vs. Reactive Routing
? 1. Proactive versus Reactive
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Proactive Routing Protocol - DSDV

• Destination Sequenced Distance Vector
• Based on the distributed Bellman-Ford routing
  algorithm
• Each node maintains a routing table
• Periodical update
• Routing hops to each destination
• Sequence number originated by the destination
  node
• To avoid loops

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DSDV Operation 1/3
MH4 advertised table
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DSDV routing updates

• Each node periodically transmits updates
• Includes its own sequences number, routing table
  updates
• Nodes also send routing table updates for
  important link changes
• When two routes to a destination received from
  two different neighbors
• Choose the one with greatest destination sequence
  number
• If equal, choose the smaller metric (hop count)

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DSDV Operation - 2/3

• MH1? ?? update? ???? MH7? MH8? ??????
• Broken link? ??? ??
• MH2? ?? ?? seq num? ??? metric? ?? incremental
  update ??
• Update ? network? propagate

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DSDV --- link additions

• When A joins network
• Node A transmits routing table ltA, 101, 0gt
• Node B receives transmission, inserts ltA, 101, A,
  1gt
• Node B propagates new route to neighbors ltA, 101,
  1gt
• Neighbors update their routing tables ltA, 101,
  B, 2gt and continue propagation of information

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DSDV --- link breaks

• Link between B and D breaks
• Node B notices break
• Update hop count for D and E to be infinity
• Increments sequence number for D and E
• Node B sends updates with new route information
• ltD, 203, infinitegt
• ltE, 156, infinitegt

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DSDV Operation - 3/3
MH3
MH4
MH5
MH2
MH8
MH6
MH7
MH1
MH4 advertised table (updated)
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DSDV --- too much traffic

• Problem
• A lot of control traffic in the network
• Solution
• two types of route update packets
• Full Dumps
• Carry all routing table information
• Transmitted relatively infrequently
• Incremental updates
• Carry only information changed since last full
  dump
• Fits within one network protocol data unit
• If cant, send full dump

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DSDV --- Summary

• Routes maintained through periodic and event
  triggered routing table exchanges
• Incremental dumps and settling time used to
  reduce control overhead
• Lower route request latency, but higher overhead
• Perform best in network with low to moderate
  mobility, few nodes and many data sessions
• Problems
• Not efficient for large ad-hoc networks
• Nodes need to maintain a complete list of routes.

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Proactive Routing Protocol - OLSR

• Use the MPRs (Multipoint relays)
• To reduce the number of broadcast packet
• Sources build routes proactively by MPR link
  advertisements
• OLSR differs from pure LS protocols
• Only the MPR nodes of A need to forward the
  link state updates issued by A

51
Proactive Routing Protocol - OLSR
4 retransmission to diffuse a message up to 2 hops
Figure 2. Diffusion of a broadcast message
using multipoint relays
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Proactive Routing Protocol - OLSR

• OLSR computes the shortest path to a destination
  using the topology table

• Topology table

• Neighbor table

Two-hop neighbors
One-hop neighbors

• Routing Tables are calculated based on the
  information contained in the neighbor table and
  Topology tables
• Routing table entry (Destination address, Next
  hop address, distance to destination)

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OLSR Routing Protocol Details

• Node N broadcasts HELLO messages every HELLO
  interval to its one hop neighbors for neighbor
  sensing
• Determine the link status (symmetric, asymmetric,
  or MPR) of each of its one hop neighbors
• HELLO message contains list of known one-hop
  neighbors
• Node N builds neighbor table that includes all
  its 1-hop and 2-hop neighbors
• Node N selects its multipoint relay (MPR) nodes
  among its one hop neighbors such that it can
  reach all the nodes that are 2 hops away.
• MPR selection requires symmetric link to node N
• MPR node broadcasts Topology Control (TC)
  messages every TC interval to advertise link
  states
• TC message contains list of one hop neighbors who
  have selected this MPR
• Only MPR nodes can forward TC messages -gt more
  efficient flooding
• TC messages are used for routing table
  calculation
• Node with non-MANET interfaces broadcasts HNA
  messages every HNA interval ( TC interval)

54
DSDV vs. OLSR
? 2. Comparison between DSDV and OLSR
55
Clustering Protocol

• Cluster Gateway Switch Routing (CGSR)
• Table-driven for inter-cluster routing
• Uses DSDV for intra-cluster routing
• Partition the whole network into clusters
• A clusterhead is elected in each cluster
• A node belonging to two clusters is a called a
  gateway

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CGSR
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CGSR

• It uses the distance vector routing algorithm
• At each node two tables are maintained a cluster
  member table and a DV routing table
• The cluster member table records the clusterhead
  for each node and is broadcast periodically
• The routing table only maintains one entry for
  each cluster recording the path to its cluster
  head.
• CGSR can significantly reduce the routing table
  size compared to DV protocols

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Reactive Routing Protocol - DSR

• On-demand driven
• ??? ??? ??? ?? Route discovery ???? ??
• Dynamic Source Routing
• ?? ??? ?? ????? ??? ???? ??
• ??? ?? ??? ?? ??? ??? ?? ??? ??
• Should maintain route caches

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Reactive Routing Protocol - DSR

• Two major phases
• Route Discovery
• Route Request (RREQ)
• Route Reply (RREP)
• Use cache
• Route Maintenance
• Route Error (RERR)

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DSR - Route Discovery (1/3)
N1-N2
N1-N2-N5
N1
N1-N3-N4
N1-N3-N4
N1-N3-N4-N7
N1-N3
N1
N1-N3-N4
N1-N3-N4-N6
Figure 4. Propagation of the RREQ
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DSR - Route Discovery (2/3)

• N8? N1? ?? path? ??? route cache? ??? ?? ????.
• Cache? path? ?? ??
• Symmetric link? ?? -gt reverse route?? (route
  record)
• Not symmetric link? ?? -gt N8? N1??? route? ?? ??
  Route Request? Route Reply? ?? ???.
  (Piggybacking)

Figure 5. Propagation of the route reply with the
route record
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DSR - Route Discovery (3/3)
Figure 6. N1 Send the data to N8
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Reactive Routing Protocol - AODV

• Ad hoc On-demand Distance Vector
• AODV Hop-by-hop Reactive
• AODV design purpose
• Low network utilization (less broadcast)
• Loop-free property (using destination sequence )
• Scalable to large network
• Assumptions
• Uses symmetric links

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Reactive Routing Protocol - AODV

• On-demand driven
• Nodes that are not on the selected path do not
  maintain routing information

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AODV Route Discovery

• A source node S wishes to communicate with
  destination node D broadcast a Route Request
  (RREQ) to its neighbors
• Intermediate nodes forward the
• RREQ to their neighbors
• The destination node sends a Route Reply
• Message (RREP) back to the source node
• An intermediate node may send a RREP provided
• that it knows a fresh enough route to the
  destination
• Nodes maintain routing table entries only for
  active routes, unused routes are removed from the
  routing table after active_route_timeout interval

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Route Discovery - 1/5
B
RREQ
S
A
D
C

• Node A receives RREQ
• Makes reverse route entry for Sdest S, next
  hop S, hop cnt 1
• It has no route to D, so it rebroadcasts RREQ
• Node C receives RREQ
• Makes reverse route entry for Sdest S, next
  hop A, hop cnt 2
• It has a route to D, and the seq for route for
  D is gtDs seq in RREQ

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Route Discovery - 2/5
B
S
A
RREP
D
C

• Node C sends RREP
• C creates a Route Reply (RREP)Enters Ds IP
  addr, seq Ss IP addr, hop count to D
  (1)Lifetime
• Unicasts RREP towards A

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Route Discovery - 3/5
B
S
A
RREP
D
C

• Node A receives RREP
• Makes forward route entry to Ddest D, next hop
  C, hop count 2, Lifetime
• Unicasts RREP to S

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Route Discovery - 4/5
B
RREP
S
A
D
C

• Node S receives RREP
• Makes forward route entry to Ddest D, next hop
  C, hop count 3, Lifetime

70
Route Discovery - 5/5
B
S
A
D
C

• Node S sends data packets on route to D

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Reactive Routing Protocol AODV DSR
Intermediate node i-1
Destination node D
Intermediate node i
Intermediate node i1
Source node s
Route Request
Route Request
Route Request
Route Request
Route discovery 1
Route Reply
Route Reply
Route Reply
Route Reply
Data forwarding
Data forwarding
Route maintenance
Route Error
Route Error
Route Request
Route Request
Route discovery 2
Route Reply
Route Reply
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AODV vs. DSR
? 3. Comparison between AODV and DSR
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Comparison of flat routing protocols
? 4. Characteristics of flat routing protocols
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Reactive Routing Protocol - AODV

• Problem
• When a node along the route moves
• Solution
• Upstream neighbor notices the move
• Propagates a link failure notification message to
  each of its active upstream neighbors
• The source node receives the message and
  re-initiate route discovery

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Security Flaws of AODV

• Vulnerable to the following attacks by a
  malicious node M
• Impersonate a node S by forging a RREQ with its
  address as the originator address
• Reduce the hop count field when forwarding RREQ
  generated by S
• Impersonate a node D by forging a RREP with its
  address as a destination address
• Selectively, not forward certain RREQs and RREPs,
  not reply certain RREPs, and not forward certain
  data messages
• Forge a RERR messages pretending it is the node S
  and send it to its neighbor D
• Set the sequence number of a node to a much
  bigger number.

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Securing AODV Protocol (SAODV)

• It is assumed that there is a key management
  sub-system that makes it possible for each ad hoc
  node to obtain public keys from the other nodes
  of the network.
• Two mechanisms are used to secure the AODV
  routing messages
• Digital signatures To authenticate non-mutable
  fields of the messages (Solves attacks 1 3)
• Hash chain To secure the hop count field in
  mutable messages
• The information related to the hash chains and
  the signature is transmitted as Signature
  Extension with the AODV messages.

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SAODV Hash Chains

• SAODV uses hash chains to authenticate the hop
  count field of RREQ and RREP messages
• This solves the attack 2
• A hash chain is formed by applying an one-way
  hash function (e.g. MD5) repeatedly to a seed
• Every time a node wants to send a RREQ or a RREP
  it generates a random number (seed). Sets
  Max_Hop_Count to the TimeToLive value in the IP
  header, and Hash to the seed value.
• Then, it calculates Top_Hash by hashing seed
  Max_Hop_Count times.
• Hash seed
• Top_Hash hMax_Hop_Count(seed)

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SAODV Hash Chains

• Every time a node receives a RREQ or a RREP it
  verifies the hop count of the message by
  verifying the Top Hash value.
• Before rebroadcasting a RREQ or forwarding a
  RREP, a node hashes one time the Hash value in
  the Signature Extension.
• Top_Hash hMax_Hop_Count Hop_Count(seed)
  Hash h(Hash)

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SAODV Digital Signature (1)

• Digital signatures (DS) are used to protect the
  integrity of non-mutable data in RREQ and RREP
  messages
• They sign every thing but the hop count of the
  AODV message and the hash from SAODV extension
• The main problem in applying DS is that AODV
  allows intermediate nodes to reply RREQ messages
  if they have a route to the destination (i.e.
  intermediate nodes should be able to sign the
  RREP on behalf of the final destination)

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SAODV Digital Signature (2)

• To solve this problem, the paper offers two
  alternatives
• The first solution is that if an intermediate
  node cannot reply to a RREQ (because it cannot
  properly signs its RREP), it just behave as if it
  didnt have the route and forwards the RREQ
  message
• The second one is that, a node generating a RREQ
  message, includes the RREP flags, the prefix
  size, and the signature that can be used to
  create RREP
• When an intermediate node generates a RREP, the
  route life time will change from the original one
• The intermediate node should include both life
  times and sign the new lifetime

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SAODV Digital Signature (3)

• Original information of the route is signed by
  the final destination and the lifetime is signed
  by the intermediate node
• This leads to two different
• SAODV extensions single and
• double signature extensions
• When a node receives a RREP/
• RREQ, it first verify the signature
• before creating or updating a
• route/ reverse route to the host

82
SAODV Error Messages

• Route Error (RERR) messages are generated by a
  neighbor node to other nodes informing that it is
  not able to route messages to certain destination
  anymore
• Every node (generating or forwarding a RERR
  message) uses digital signature to sign the whole
  message
• Any neighbors that receives the RERR verifies the
  signature
• Verify that the sender of the RERR message is
  really the one that it claims to be

83
Other Routing Protocols

• In principle SAODV could be used to create
  secure version of other routing protocols
• If the routing protocol has some other mutable
  information, intermediate nodes that mutate part
  of the messages also have to sign it.
• Dynamic Source Routing (DSR) has been used as an
  example for other routing protocols
• DSR includes in its routing message the IP
  addresses of all intermediate nodes
• Signing the message by each intermediate nodes
  reduces the routing pereformance (due to
  additional cryptographic computations)

84
Key Management

• It is assumed that each node has a trustworthy
  means of checking the association between the
  addresses and signatures of other nodes
• This association (binding) is typically achieved
  by using public key certificates issued by a
  certification authority (CA)
• This can work if ad hoc nodes could have
  permanent addresses
• One secure and potentially expensive solution
  would be to pick a key pair, and map the public
  key to a tentative address . If there is a
  collision, pick a new key pair and try again

85
Discussion (1)

• The paper relies on public key management. It is
  not realistic to assume that nodes in ad hoc
  networks will have access to public key
  infrastructure
• Distribution of certificates by CA implies huge
  overhead, and it is not effective in the presence
  of partitions and high mobility
• An effective mechanism is needed to address the
  problem of key certificates distribution
• The hash chain algorithm only addresses single
  mutable information (hop count), it would be more
  complex if more mutable information is to be
  addressed

86
Discussion (2)

• The use of asymmetric cryptography adds more
  overhead to the processing power requirements of
  the SAODV
• The proposed algorithms do not require
  modification to the AODV protocol, they are added
  as an extension to the existing AODV message
  formats
• The algorithms provide a general mechanism that
  could be applied to different routing protocols.
• However, it would be more effectient to extend
  the algorimths and define separate meachanisms
  for different ad hoc routing protocols

87
Discussion (3)

• The authors reported that SAODV cannot detect
  tunneling attacks
• Hop count authentication by using hash chains is
  not perfect A malign node might forward a
  message without increase the hop count.
• More secure approaches are too expensive, and
  they don't solve tunneling attacks.

88
ZRP

• Zone Routing Protocol
• Hybrid protocol
• On-demand
• Proactive
• ZRP has three sub-protocols
• Intrazone Routing Protocol (IARP)
• Interzone Routing Protocol (IERP)
• Bordercast Resolution Protocol (BRP)

89
(No Transcript)
90
LAR

• Location-Aided Routing
• Location information via GPS
• Shortcoming
• GPS availability is not yet worldwide
• Position information come with deviation

91
LAR
92
DREAM

• Distance Routing effect Algorithm for mobility
• Position-based
• Each node
• maintains a position database
• Regularly floods packets to update the position
• Temporal resolution
• Spatial resolution

93
Power-Aware Routing criteria

• Examples
• Minimize energy consumed per packet
• Minimize time to network partition due to energy
  depletion
• Maximize duration before a node fails due to
  energy depletion

94
Power-Aware Routing approach

• Assign a weight to each link
• Weight of a link may be a function of
• energy consumed when transmitting a packet on
  that link
• residual energy level
• Prefer a route with the smallest aggregate weight

95
Power-Aware Routing
96
Conclusions

• These protocols are continuously modified and
  improved to keep their advantage and weaken their
  drawbacks
• Security is big challenges or key problems in ad
  hoc network