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

Amrinder SinghDept. of Computer Science

Virginia Tech.

Agenda

Introduction OM-HMIPv6 Analytical Modeling Numerical Results Simulation Validation Conclusion

Introduction

Mobility management is essential for keeping track of user’s 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

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 MAP’s subnet

Communication of MN MAP receives all packets on behalf of MN

Encapsulates and forwards directly to MN’s 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

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

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

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

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

Configuration of OM-HMIPv6 RMAP broadcasts RA with DIST=0

IMAP receives RA and re-broadcasts RA after increasing DIST field and compares DIST with optimal depth D*

If DIST<D*, MAP appends its IP address to MAP hierarchy list

Otherwise, forward RA as it is

Can employ some kind of loop elimination

Adaptation Scheme

Parameters defined change from time to time

Need to redefine optimal hierarchy

Recalculate optimal hierarchy and perform reconfiguration

Not done very often

Analytical Modeling

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

Rectangular cell configuration

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

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

ρ is the density of MNs

v is the average velocity of MNs

Location Update Cost

Update Cost to HA caused by MN moving to foreign network

Sum of location update incurred by crossing k-level MAP domain area

Location cost incurred by crossing from one cell to another

Unit Location update cost

ω and η are unit update cost over wired and wireless link respectively

where H is distance between RMAP and AR

and di-1,i =1

Packet Delivery Cost Need to consider transmission cost and processing

cost at each entity Packet delivery from CN to RMAP is given by

α is the unit transmission cost over a wired link

PHA is processing cost at HA

Packet Delivery Cost Packet delivery cost from RMAP to AR

Packet Delivery cost from AR to MN

where β is unit transmission cost over wireless link

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))

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

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

Numerical Results System Parameters used

Numerical Results

Optimal Hierarchy increases with number of ARs. More importantly an optimal hierarchy level exists

Session Arrival rate is normalized to 1

As SMR , mobility and location cost

As ARs , more levels and location cost

Numerical Results

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

Varying the communication costs does change optimal hierarchy by determining which cost dominates.

Simulation Validation 5 types of MAP hierarchy evaluated. Use random walk mobility model

Routing probability for each direction is the same

Simulation Validation The MN stays in a given

cell area for time tR

This follows Gamma distribution with b=kλm

The session arrival process follows Poisson distribution

The session length is modeled by Pareto distribution with mean =ak/(a-1)

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

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

Simulation ResultTotal 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

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.