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					Prophet Address Allocation Protocol for
         Large Scale MANETs



   Hongbo Zhou, Lionel M. Ni, Matt W. Mutka
                INFOCOM 2003



                     NPRG
                      3/18

       Sehoon Kim (kimsh@cnlab.kaist.ac.kr)
                                        KAIS
        (Dept of Computer Science, KAIST)


                                         T
Contents
Introduction
Related work
Prophet address allocation
   Prophet allocation
   Mechanism for partition and merge
   Protocol
   Design of f(n)
Performance analysis
Simulation
Conclusion




                    Prophet Address Allocation for Large Scale MANETs   2 / 22
Introduction [1/2]
Mobile Ad hoc NETworks (MANET)
   A multi-hop wireless network capable of autonomous operation
   Without any infrastructure or centralized administration


Dynamic address allocation is important for autonomous
operation of MANET


Difficulties of autoconfiguration in MANET
   Mobility, instability, low bandwidth and power resources
   MANET partitioning and merging
   Absence of central administration
   Protocols for wired networks are not suitable
      DHCP[RFC 2131] assumes central server


                   Prophet Address Allocation for Large Scale MANETs   3 / 22
Introduction [2/2]
Possible scenarios



           MANET
                                                                MANET A         MANET B
                                                 Partition

 (a) A node joins and                        (b) MANET partitions
        leaves




      MANET A               MANET B                   MANET A               MANET B


                                  (c) Merger of two MANETs


                        Prophet Address Allocation for Large Scale MANETs             18
                                                                                  4 / 22
Related Work [1/2]
Conflict detection       [Perkins et al, Internet draft, 2000]                                D
                                                                                 B
    Multiple rounds of MANET-wide flooding
    Trial and error policy
                                                                           A   Available 7?
    Disadvantages
         No consideration about network partitioning and merging
                                                                                C             E
         No consideration about concurrent address request


Best-effort [Nesargi et al, INFOCOM’02]
    Based on distributed mutual exclusion algorithm                                           D
    Assignment of a new address requires approvals                               B

    from all other known nodes in the network
                                                                           A    Yes or No
                                                                               Available 7?
    Disadvantage
         Global state is maintained, which requires much
         memory and communication overhead for                                  C             E
         synchronization


                       Prophet Address Allocation for Large Scale MANETs                 22
                                                                                     5 / 18
Related Work [2/2]
Conflict free [Misra et al, 2001]                                                A(1, 2-
                                                                                   8)
    Binary splitting adopted in allocation
                                                                       A(1, 2-              B(5, 6-
    Disjoint address pools                                               4)                   8)


    Disadvantages                                          A(1, 2-2)
                                                                                 C(3, 4-
                                                                                   4)
        No consideration about network
        partitioning and merging
        Address reclamation is difficult




                     Prophet Address Allocation for Large Scale MANETs                     6 / 22
Prophet Allocation [1/3]
Goal
   Assignment of different numbers to different mobile nodes


Based on a stateful partition function: f(n)
   The initial state is called the seed
   Different seeds leads to different sequences
   The interval between two occurrences of the same number in one
   sequence is very long
   The possibility of more than one occurrences of the same number in
   limited number of different sequences is very low


The sequences can be computed locally



                   Prophet Address Allocation for Large Scale MANETs   7 / 22
Prophet Allocation [2/3]
(1) The first node (node A) chooses a random number as its IP
address and uses a random state value (or default state value)
as the seed for f(n)


(2) When a new node (node B) approaches node A, A uses f(n)
to compute another integer and a state value and provides
them to B


(3) Node B uses these values as its IP address and the seed
for its f(n)


(4) Node A and node B are able to assign IP addresses to
others

               Prophet Address Allocation for Large Scale MANETs   8 / 22
Prophet Allocation [3/3]
Example
  f(n) = (address * state * 11) mod 7




                                 A (3, 3)



                  A (3, 1)                        B (1, 1)




       A (3, 5)          C (5, 5)         B (1, 4)         D (4, 4)



                    Prophet Address Allocation for Large Scale MANETs   9 / 22
Mechanism for partition and merge [1/2]
Scenario b: the same as the scenario a


Scenario c
   A network ID (NID) is generated by the first node and propagated
   throughout the MANET
   NID is piggybacked in periodic HELLO messages




                 Prophet Address Allocation for Large Scale MANETs   10 / 22
Mechanism for partition and merge [2/2]
The node detecting merger initiates local conflict detection
and resolution
   The seed value for the whole MANET is also piggybacked in HELLO
   messages
   f(n) is applied to both seed values and obtain possible conflicting
   addresses
   The conflicting addresses are broadcast throughout the MANET
   A new NID is generated for the new larger MANET


Nodes in one MANET discard their current IP addresses and
acquire new addresses in the other MANET




                  Prophet Address Allocation for Large Scale MANETs   11 / 22
Protocol



                                            Un-initialized   Switch to ad-hoc mode
                  Switch from ad-hoc mode
                                                             Broadcast state request

                                         Received response
 Received state request Configured
                                             Configure                           Retries ≤ k
                                             Retries > k           Waiting
Send reply, update state                                                        Repeat broadcast
                                           Self-configure
                                   Received different NID

                              Finished

                                            Local conflict
                                             detection &
                                              resolution




                         Prophet Address Allocation for Large Scale MANETs                         12 / 22
Design of f(n) [1/2]
Related to IP address range

   192.168.0/24 (class C) is not large enough due to “birthday paradox”
   10/8 (class A) and 172.16/12 (class B) are good candidates
   No concern for IPv6 address range


Based on the fundamental theory in arithmetic
   n = ∏piei, (primes pi satisfy p1 < p2 < … < pk,i = 1, 2, …, k)


We want to generate different k-tuples (e1, e2, …, ek)




                   Prophet Address Allocation for Large Scale MANETs   13 / 22
  An example of f(n) [2/2]
  A node is represented by (address, (e1, e2, e3, e4))
  address = (a + 2e13e25e37e4) mod range + 1



                                  A(a, (0, 0, 0, 0))


             A(a, (1, 0, 0, 0))                            B(a+3, (1, 0, 0, 0))




A(a, (2, 0, 0, 0))   C(a+5, (2, 0, 0, 0))       B(a+3, (1, 1, 0, 0)) D(a+7, (1, 1, 0, 0))



                       Prophet Address Allocation for Large Scale MANETs          14 / 22
    Performance Analysis [1/2]

                    Conflict detection      Conflict free         Best effort    Prophet



    Network             Flat /                                     Flat /
                                                Flat                              Flat
  organization       Hierarchical                               Hierarchical



State maintenance      Stateless         Partially stateful        Stateful     Stateful




 Address conflict         Yes                   No                   Yes           No



     Address
                       Unneeded              Needed                Needed       Unneeded
   reclamation



                          Prophet Address Allocation for Large Scale MANETs       15 / 22
Performance Analysis [2/2]

                      Conflict
                                       Conflict free       Best effort   Prophet
                     detection

    Complexity         Low                 High               High        Low

  Communication
                    O((n+l)k)            O(2l/n)           O((n+l)k)     O(2l/n)
    overhead

   Evenness of                           Possibly
                       Even                                   Even        Even
   distribution                          uneven

     Latency         O(2tdk)              O(2t)             O(2tdk)       O(2t)

                                        Medium /
    Scalability        Small                                 Small        High
                                         Small


n(node number) l(link number) k(retry time) t(xmit time) d(net diameter)

                   Prophet Address Allocation for Large Scale MANETs         16 / 22
Simulation [1/5]
Simulation of Conflict-detection allocation and Prophet
allocation were done on ns-2 (ver 2.1b8a)


Simulated of 50, 80, 100, 120 and 150 nodes within different
area sizes for performance comparison




               Prophet Address Allocation for Large Scale MANETs   17 / 22
Simulation [2/5]




           Communication overhead for 50 nodes

           Prophet Address Allocation for Large Scale MANETs   18 / 22
Simulation [3/5]




        Ratio of communication overhead of CDA to PA

            Prophet Address Allocation for Large Scale MANETs   19 / 22
Simulation [4/5]




                     Latency for 50 nodes

           Prophet Address Allocation for Large Scale MANETs   20 / 22
Simulation [5/5]




            Latency for different node numbers

           Prophet Address Allocation for Large Scale MANETs   21 / 22
Conclusion

Prophet allocation achieves
  Low complexity
  Low communication overhead
  Even distribution
  Low latency
  High scalability


Future work
  Simulation of more than 200 nodes
  Specification details on mechanism for network merger




                 Prophet Address Allocation for Large Scale MANETs   22 / 22

				
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