Design and Analysis of Optimal MultiLevel Hierarchical Mobile IPv6 Networks

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Design and Analysis of Optimal Multi-Level
Hierarchical Mobile IPv6 Networks

• Amrinder Singh
• Dept. of Computer Science
• Virginia Tech.

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Agenda

• Introduction
• OM-HMIPv6
• Analytical Modeling
• Numerical Results
• Simulation Validation
• Conclusion

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Introduction

• Mobility management is essential for keeping
  track of users current location
• Many schemes proposed for cellular networks
• Next-generation wireless/mobile network will be
  unified networks based on IP technology
• Design of IP-based mobility management schemes
  has become necessary

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Introduction

• HMIPv6 is enhanced version of Mobile IPv6
• Minimizes signaling cost using a local agent
  called mobility anchor point (MAP)
• MN entering MAP domain receives Router
  Advertisement (RA) from one or more local MAPs
• MN can bind current CoA with an address on MAPs
  subnet

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Communication of MN

• MAP receives all packets on behalf of MN
• Encapsulates and forwards directly to MNs
  current address
• Movement of MN within local MAP domain requires
  registration of new CoA with MAP reducing
  location update
• To reduce location update further, the case of
  multi-level hierarchical MAPs

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Background

• One of the earlier schemes focused on
  determination of optimal size of regional network
• Did not focus on determining optimal hierarchy
• Other schemes proposed to optimize HMIPv6 did not
  consider the case of multi-level hierarchical
  structure

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Optimal Multi-Level HMIPv6

• Multiple MAPs organized in a tree structure
• Root MAP
• Intermediate MAP
• Leaf MAP
• Better fault tolerance, failure of MAP affects
  only the sub-tree under the MAP
• Reduction in location update cost by localization
  of binding update procedure
• Increase in packet delivery cost due to
  encapsulation and decapsulation

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Binding Update

• MN sends Binding Update (BU) message to RMAP
• At LMAP, check if MN is already registered with
  it
• If it is, registration completed
• Otherwise register and forward the BU
• At each IMAP, check for registration as with LMAP
• Process stops at IMAP where MN is already
  registered

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Parameters for determining optimal level

• The number of MNs
• Calculate the average number of MNs in network
  and divide by total area to determine density
• MN mobility
• Determine average MN velocity during time
  interval T
• MN activity
• Determine session arrival rate and average
  session size during T

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Configuration of OM-HMIPv6

• RMAP broadcasts RA with DIST0
• IMAP receives RA and re-broadcasts RA after
  increasing DIST field and compares DIST with
  optimal depth D
• If DISTltD, MAP appends its IP address to MAP
  hierarchy list
• Otherwise, forward RA as it is
• Can employ some kind of loop elimination

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Adaptation Scheme

• Parameters defined change from time to time
• Need to redefine optimal hierarchy
• Recalculate optimal hierarchy and perform
  reconfiguration
• Not done very often

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Analytical Modeling
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Assumptions

• Access Routers (AR) are uniformly distributed in
  each LMAP
• The tree formed is a binary tree
• Fluid-Flow mobility model with rectangular cell
  configuration

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Rectangular cell configuration
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Location update cost

• Number of cells in network N, i.e. ARs
• Number of ARs located in k-level MAP domain
• Lc is the perimeter if cell
• Lk is perimeter of k-level MAP domain

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Location Update Cost

• Crossing rate for fluid flow model is given by
• Total location update cost takes into account all
  possible crossings in the network
• MNs moving in from foreign networks
• MNs moving across k-level MAP domains
• MNs moving across AR cell boundaries

? is the density of MNs v is the average velocity
of MNs
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Location Update Cost
Update Cost to HA caused by MN moving to foreign
network
Location cost incurred by crossing from one cell
to another
Sum of location update incurred by crossing
k-level MAP domain area
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Unit Location update cost
? and ? are unit update cost over wired and
wireless link respectively where H is distance
between RMAP and AR and di-1,i 1
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Packet Delivery Cost

• Need to consider transmission cost and processing
  cost at each entity
• Packet delivery from CN to RMAP is given by

a is the unit transmission cost over a wired
link PHA is processing cost at HA
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Packet Delivery Cost

• Packet delivery cost from RMAP to AR

• Packet Delivery cost from AR to MN
• where ß is unit transmission cost over wireless
  link

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Calculation of Processing cost

• PMAP(k) is processing cost at k-level MAP domain
• Includes lookup cost and packet
  encapsulation/decapsulation cost
• PMAP(k) is assumed to be proportional to
  log(NU(k))

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Calculating optimal hierarchy

• Formulate total cost as a function of hierarchy
  and SMR
• SMR is session arrival rate divided by mobility
  rate
• Then define the difference function

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Calculating optimal hierarchy

• If is larger than 0, the optimal hierarchy is 0
• Otherwise optimal hierarchy is given by
• Optimization can also application based
• Calculate total costs independently for each
  application
• Calculate weighted total cost

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Numerical Results

• System Parameters used

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Numerical Results
Session Arrival rate is normalized to 1 As SMR ?,
mobility ? and location cost ? As ARs ?, more
levels and location cost ?
Optimal Hierarchy increases with number of ARs.
More importantly an optimal hierarchy level exists
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Numerical Results
Varying the communication costs does change
optimal hierarchy by determining which cost
dominates.
Higher SMR means that packet delivery cost
dominates the total cost and a lower hierarchy
will reduce the total cost. Adaptive scheme will
be effective
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Simulation Validation

• 5 types of MAP hierarchy evaluated.
• Use random walk mobility model
• Routing probability for each direction is the same

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Simulation Validation

• The MN stays in a given cell area for time tR
• This follows Gamma distribution with bk?m
• The session arrival process follows Poisson
  distribution
• The session length is modeled by Pareto
  distribution with mean ak/(a-1)

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Simulation Result
Mean session length is set to 10. Session arrival
rate is normalized to 1. As SMR ?, mobility ?,
hence frequency of binding updates ? Higher
hierarchy implies lower binding cost as more
number of LMAPs and IMAPs means binding update
does not reach RMAP often
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Simulation Result
Mobility rate is fixed at 0.001 We need to count
how many MAP processings occur when packets are
delivered As SMR ?, session arrival rate ? More
packets to deliver Also cost greater for higher
hierarchy
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Simulation Result
Total cost is the sum of binding update and
packet delivery costs Validates the analytical
result that lower SMR means more hierarchical
levels while a higher SMR means lower
hierarchical levels
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Conclusions

• Authors provide extensive analysis on multi-level
  HMIPv6 which can support scalable services
• Showed that optimal hierarchical level exists for
  the network
• Investigated the effect of SMR on hierarchy
• However, did not talk about how often
  reconfiguration would be needed and did not
  indicate the cost that would incur.