ADVANCE DUPLICATE ADDRESS DETECTION (DAD) AND

BUFFERING-BASED PROVISION OF SEAMLESS HANDOVER

IN MOBILE IPV6

Shobhan Adhikari, Teerapat Sanguankotchakorn

Telecommunications Field of Study, School of Advanced Technologies, Asian Institute of Technology, P.O. Box 4, Klong

Luang, Pathumthani 12120, Thailand

Keywords: Seamless Handover, Mobile IPv6, Buffering, Simulation, NS-2, Smooth Handover, Fast Handover,

Performance Analysis.

Abstract: Due to the concerns about the imminent crunch in available addresses in the previous version of Internet

Protocol, IPv4, and to offer additional functionalities for new devices, IPv6 was proposed. Mobile IPv6

(MIPv6), an extension to IPv6, manages Mobile Nodes’ movements between wireless IPv6 networks. One

of the most important considerations for Mobile IPv6 is handover management. It is desired that handover

be fast and lossless. Seamless handovers are such that they incur minimum packet loss and delay. Various

proposals have been made for seamless handover in MIPv6. By forwarding the packets destined to the

Mobile Node towards the new point of attachment and storing the packets there until the Mobile Node has

attached there, packet loss can be significantly decreased, and the delay associated with the forwarding is

also less compared to forwarding from the previous point. In this paper, we study the performance of one

such scheme which has optimized fast handover over hierarchical structure with buffering and simulation

using NS-2 to evaluate packet loss and delay for UDP streams. It was observed that with the buffering

scheme used, the handover was seamless. There was a difference in latencies with and without handover, as

expected. It was observed that most of the performance factors studied depended on the data rate of the

traffic. The factors were found to be more dependent on the data rate than on the speed of the Mobile Node.

1 INTRODUCTION

With the increasing use of Internet capable and

handheld wireless devices, the requirement of

seamless handover has driven various proposals

towards decreasing the delay and loss associated

with handover.

In Mobile IPv6, each time Mobile Node (MN)

moves from one subnet to another, it gets a new

Care-of Address (CoA). After obtaining a CoA, it

registers Binding, consisting of its new Care-of

Address, the home address and the registration

lifetime, with the Home Agent (HA) and the

Correspondent Node(s) (CN(s)) it is communicating

with. In case of CN without MN binding, packets

reach HA and from there are tunneled to CoA,

whereas CN with knowledge of the Binding can

send the packets directly to MN’s CoA. As the

number of MNs increases and cell sizes start to

shrink to increase the capacity, number of Binding

Updates increases proportionately, causing a

significant signaling overhead. For solving this

problem, Hierarchical Mobile IPv6 (HMIPv6) was

proposed (Castelluccia, 1998). In HMIPv6, Mobility

Anchor Point (MAP), router highest in the hierarchy

in the visited network, acts like a local HA for the

visiting MN. It also limits the amount of signaling

required outside MAP's domain. The hierarchical

scheme separates local mobility (micro-mobility)

from regional mobility (macro-mobility). MN

changes only the Local Care-of Address (LCoA)

inside a local domain and not the Regional Care-of

Address (RCoA). Packets addressed to MN’s RCoA

are routed to the subnet, intercepted by MAP, and

tunneled to MN’s LCoA. This scheme improves

handover performance and reduces signaling load.

With fast handover (Koodli, 2003), the delay

involved with handover is reduced, the latency being

comparable to L2 handover latency. It reduces

packet loss by providing fast IP connectivity as soon

as MN changes to a new point of attachment. Fast

Handover may either be Tunnel-based or

Anticipated Handovers. In case of Tunnel-based

Adhikari S. (2005).

ADVANCE DUPLICATE ADDRESS DETECTION (DAD) AND BUFFERING-BASED PROVISION OF SEAMLESS HANDOVER IN MOBILE IPV6.

In Proceedings of the Second International Conference on e-Business and Telecommunication Networks, pages 44-52

DOI: 10.5220/0001418500440052

 SciTePress

Handover, routing is fixed during link configuration

and binding update, so that packets delivered to the

Old CoA (OCoA) are forwarded to the New CoA

(NCoA) by setting up a bidirectional tunnel between

old access point and new access point. In

Anticipated Handover, FMIPv6 provides support for

pre-configuration of link information (such as the

subnet prefix) in the new subnet while MN is still

attached to the old subnet, by the use of L2 triggers.

This reduces the amount of pre-configuration time in

the new subnet. Fast Handover scheme is analyzed

in (Pack and Choi, 2003). For better results,

Hierarchical structure and Fast Handover can be

used together (Jung et al., 2004). According to

(Perez-Costa et al., 2003), performance of

combination of HMIPv6 and FMIPv6 is better than

either of them acting alone.

But even with fast handover, there still is a

probability of packet loss. Bi-casting is a viable

scheme wherein MAP performs bi-casting to both

Previous Access Router (PAR) and New Access

Router (NAR), so that they both initiate sending of

packets to MN’s OCoA and NCoA in response to

handover indication. But bi-casting is not very

efficient because of the overhead involved with

sending packets to both addresses, causing

redundancy. To decrease redundancy, coordinated

bi-casting could be performed. In such a scheme,

NAR and PAR agree on a switching point, which

defines the exact moment for switching service from

PAR to NAR.

The various factors contributing to handover

delays are: IP address assignment when DHCP

server is far from MN (in case of Stateful (Bound et

al., 2001) Auto-Configuration), Duplicate Address

Detection (DAD) and Neighbor Discovery (ND) are

the main contributors to the latency. The other

contributors are the various signaling. Handover

latency can be decreased if the delays due to the

factors mentioned can be decreased. After forming a

new CoA, with either Stateless (Thomas and Narten,

1998) or Stateful Auto-configuration, MN may

perform DAD on it. For DAD, MN sends one or

more Neighbor Solicitations to its new address and

waits for a response for at least one second, hence

contributing a significant portion to the total

handover delay (Montavont and Noel, 2003). Hence,

with some scheme to reduce this delay, the overall

handover delay could be reduced significantly. (Lee

et al., 2001) has a scheme where MN performs DAD

while using OCoA and packets are buffered at PAR

during handover. With this, packets have to travel

the distance PAR-MAP-NAR while they are

forwarded to MN. To improve performance further,

buffering could be done at NAR so that buffered

packets can avoid the additional distance of PAR-

MAP.

Advance DAD (Han et al., 2003) can be used to

reduce the delay contributed by DAD to the overall

handover delay. Advance DAD scheme

automatically allocates a globally routable IPv6 CoA

for the use of MNs that participate in fast handover.

Buffering reduces packet loss by storing packets

destined for MN during the time MN is handing over

and forwarding the same to MN after it has

established link connectivity.

2 RELATED WORKS

In this section, some related works for fast and

lossless handover are described. Related works for

mainly fast and lossless handovers for Mobile IPv6

are discussed.

(Perez-Costa et al., 2003) study the performance

of Mobile IPv6, Hierarchical Mobile IPv6, Fast

Handover for Mobile IPv6 and their combination.

From their study, they show that the performance of

combination of HMIPv6 and FMIPv6 (H+F MIPv6)

is better than either HMIPv6 or FMIPv6. It has been

shown that it has better packet losses than FMIPv6

acting alone; but a larger bandwidth is obtained with

FMIPv6 acting alone. In case of H+F MIPv6, MAP

encapsulates all the data packets addressed to MNs,

and this overhead reduces the available bandwidth in

the channel. But for overall performance, H+F

MIPv6 has been found to be better.

(Lee et al., 2001) propose a scheme for fast and

lossless handover method considering DAD in IPv6-

based mobile/wireless networks. They have

considered the fact that latency comes mainly from

ND and DAD in stateless Auto-Configuration

scheme. MN obtains NCoA before handover and

PAR uses buffer management, making the proposed

scheme fast and lossless. In the proposed scheme,

MN receives several beacon signals containing the

network prefix and decides whether it needs to

change its AR by calculating the Received Signal

Strength (RSS) from neighboring ARs. Handover

initiates if another AR has higher signal strength

than the current AR. PAR starts buffering the

packets destined for MN. NAR, in the meantime,

acts as a proxy so that it can respond to any potential

DAD conflicts on its link for NCoA. NAR performs

a valid check for NCoA by comparing ND cache

entry with NCoA. PAR forwards the buffered

packets to NAR after receiving signal for the same

from NAR.

A scheme in which buffering of packets is done

at PAR while MN transitions to a new network is

proposed in (Park and Lim, 2002). Once MN

completes registration and obtains a valid NCoA,

PAR forwards the packets to MN at the new address.

ADVANCE DUPLICATE ADDRESS DETECTION (DAD) AND BUFFERING-BASED PROVISION OF SEAMLESS

HANDOVER IN MOBILE IPV6

Buffer management has been proposed with two

traffic classes, namely high-priority class as real-

time traffic with strict delay requirement such as

voice; and low-priority class with tolerable delay

and strict packet loss requirements such as pure data.

They propose an extension to the IPv6 Router

Advertisement which allows a router to advertise its

ability to support Simple Buffering (SB), where SB

is based on the general smooth handoff framework

as specified in (Krishnamurthi et al., 2001).

Different sub-options are also used; namely, Buffer

Initialize (BI), Buffer Forward (BF) and Buffer

Acknowledgement (BA). Incoming packets destined

for OCoA are buffered in addition to being

forwarded normally. When MN completes handover,

it sends BF sub-option asking the buffered packets

to be forwarded to NCoA.

A novel seamless handover architecture, S-MIP

is proposed in (Hsieh et al., 2003). The proposal

builds on top of hierarchical and fast-handover

mechanism of MIPv6, in conjunction with a

handover algorithm based on software-based

movement tracking techniques. They argue that with

such a combination, the performance is better,

providing a lossless handover with low latency. Two

distinct buffers are maintained at NAR in S-MIP

architecture, one for packets forwarded from PAR

(f-buffer) and one for the packets simulcast to the

current network MN is in and potential access

network MN will get attached to (s-buffer). NAR

will start delivering buffered packets to MN after it

receives Fast Neighbor Advertisement, signifying

that MN has arrived at its network. NAR will

attempt to transmit the packets in f-buffer and empty

it before beginning to transmit from s-buffer. At

PAR, it will only forward those packets which are

not simulcast to NAR. In case that MN does not

switch network immediately, it will therefore still be

able to receive packets from PAR.

A scheme called Mobile IPv6 Cache is proposed

in (Chung and Nelson, 2004). In the scheme, cache

at HA stores packets during handover. When HA

detects completion of handover, it will flush the

appropriate part of its cache immediately. Hence,

MN will receive a positive Binding

Acknowledgement followed by a burst of packets to

recover communications quickly. They argue that

Mobile IPv6 Cache can be implemented in existing

networks to improve communication performance

across handovers.

3 PROBLEM FORMULATION

From different handover schemes discussed, it

can be established that a combination of HMIPv6

and FMIPv6 has the advantage of reduction of

signaling delay and message overhead (as in

HMIPv6), and also support of fast handover by L2

triggers and minimal service disruption by tunneling

(as in FMIPv6). But a straight forward integration of

FMIPv6 with HMIPv6 would not be an efficient

option. Such integration would induce unnecessary

overhead for re-tunneling at the PARs and also

inefficient usage of network bandwidth as FMIPv6

uses the tunneling between the previous and new

ARs for fast handover. Hence, FHMIPv6, where

tunneling is between NAR and MAP rather than

between PAR and NAR, should perform better. MN

exchanges signaling messages for handover such as

RtSolPr, PrRtAdv, FBU, and FBAck with MAP. For

buffering, larger buffer at AR can tolerate less

frequent RAs and longer period of contact, but with

added latency. On the other hand, more frequent

RAs take up more wireless bandwidth and denser

coverage requires more ARs (hence, more

equipment). Balancing these factors is important for

achieving optimal handover.

The latency involved with Anticipated Fast

Handover protocol is mainly due to lack of

knowledge about NCoA, time taken for DAD,

signaling latency and L2 handover delay. The first

requires some time for discovery of new AR and for

BU. The second requires some time for the checking

of uniqueness of NCoA acquired by MN. The third

requires some time due to the signaling between

MN, ARs and HA / CN(s). The delays are usually

appreciable and can lead to packet loss. Effect of the

first case can be reduced to some extent by using

anticipation. Optimistic DAD (Moore, 2004), which

is a modification of existing IPv6 ND and Stateless

Address Auto-Configuration, could be one option to

reduce the effect of the second. Alternatively,

Address Pool based Stateful NCoA configuration for

FMIPv6 (Proactive and reactive stateful schemes)

could also be used (Jung et al., 2003). The scheme of

Advance DAD (Han et al., 2003) is another option.

Advance DAD scheme automatically allocates a

globally routable IPv6 CoA for the use of MNs that

participate in fast handover. Advance DAD is

considered in this work.

Buffering eliminates packet loss; they can reside

in ARs and store packets addressed to MN during

handover period temporarily. When handover is

complete and MN is attached to NAR, the stored

packets are forwarded to MN. Buffering could be

performed at NAR, in case of pre-registration, where

MN acquires NCoA before it moves to the new point

of attachment. Buffering could be performed at PAR

in case of post-registration. Tunnel Buffering (TB)

considers the situation where MN anticipates that it

is about to move, but does not know where it is

about to move to. In this case, MN can send a

ICETE 2005 - WIRELESS COMMUNICATION SYSTEMS AND NETWORKS

special L-BU requesting that its traffic be buffered at

MAP until it has determined its new link CoA

(Moore et al., 2004). Once it has completed

movement and gets attached to the new point of

attachment, MAP forwards the buffered packets to

MN and also starts tunneling the new packets

destined for MN.

In this work, buffering is performed at NAR for

FHMIPv6 protocol (Jung et al., 2004). MAP will

start forwarding packets destined to MN towards

NAR after tunnel is established during HI/HAck.

Hence, the packets are stored in the buffer at NAR

till MN establishes link with NAR, after which,

buffered packets are forwarded to MN.

3.1 Operational Detail

During normal operation, MN is connected to the

current AR, called PAR. Packets destined to MN are

routed from MAP via PAR in the wired link. In the

wireless link, the packets are sent on the air to MN

from PAR. A case of pre-registration handover is

considered. MAP manages a 'Passive Proxy Cache'

associated with its domain. The number of addresses

kept in the cache depends on the value of the address

pool.

The generation of globally routable addresses is

performed in the background and DAD is performed

on them. When DAD is complete, the addresses are

stored in the cache and are reserved. But when MAP

detects the use of any of the addresses present in the

cache, through RD messages, it deletes the address

from the cache. The address pool is continuously

updated by generating new addresses, so that the

addresses in the pool approach the pool size.

(PAR)

MAP

PrRtAdv

Disconnec

NAR

HAc

(NAR)

BAc

Buffering

BAc

Deliver Packets

Normal HM IPv 6

Operation

Connec

NAc

No rmal

HMIPv6

Operation

PAR

Tu n n e

RtSolPr

Forward

Packets

Figure 1: Signalling and Operations during and after

Handover

To initiate fast handover, as a consequence of L2

handover anticipation trigger (Yegin et al., 2002),

MN sends Router Solicitation for Proxy (RtSolPr) to

MAP indicating that it desires to implement fast

handover to a new point of attachment. RtSolPr

contains an identifier for the new attachment point.

MAP will then send the Proxy Router

Advertisement (PrRtAdv) containing the duplication

free address from its cache and the address is

removed from the cache. Meanwhile, MAP sends

Handover Initiate (HI) message to NAR. In response

to the HI message from the MAP, NAR sends

handover acknowledgement (HAck) message and

setup of the tunnel between MAP and NAR is

complete. NAR starts buffering any packets tunneled

to it by MAP. After receiving PrRtAdv from PAR,

MN sends F-BU to MAP via PAR and disconnects

from PAR. MAP in response to F-BU associates

NCoA with OCoA and sends out acknowledgement

F-BAck, which MN receives from NAR. NAR

continues buffering the packets from MAP until it

receives Fast Neighbor Advertisement (F-NA)

message from the newly incoming MN after it has

established link connectivity. In response to F-NA

from MN, NAR sends out F-NAck to MN and starts

delivering the packets which have been buffered.

MN then follows the normal HMIPv6 operations by

sending Local Binding Update (L-BU) to MAP.

When MAP receives the new L-BU from MN, it will

clear the tunnel established for fast handover after

forwarding of the buffered packets is complete. In

response to L-BU, MAP will send Local Binding

Acknowledgement (L-BAck) to MN and the normal

operation of HMIPv6 will follow. The signaling and

operations are shown in figure 1 for the periods

during and after handover.

In (Hsieh et al., 2002), forwarding of packets by

PAR towards the NAR starts only after receiving

BU (F-BU) and in (Jung et al., 2004), forwarding

starts only after FBAck. But with these options,

some packets tend to go towards PAR and reach

PAR after MN has already left PAR. With such a

provision, it was seen that packets are lost. This will

be discussed a little later in the section on

Simulation. If the packets are tunneled towards NAR

right after HI/HAck, then this probability of loss is

decreased. The increase in latency with this is also

not very significant.

4 SIMULATION

Simulation was performed using Network

Simulator-2 (ns-2) (The Vint Project). The version

of NS-2 used was ns-2.1b7a, and the extension

developed by Jorg Widmer (Widmer) was added. In

ADVANCE DUPLICATE ADDRESS DETECTION (DAD) AND BUFFERING-BASED PROVISION OF SEAMLESS

HANDOVER IN MOBILE IPV6

addition, the extension for FHMIPv6 (Hsieh) was

also added on top of ns-2.1b7a and the NOAH

extension. The resulting product was modified as

required, the details of which are given in the

following.

The modifications consisted of changing the

point of sending different fast handover signals to

MAP instead of PAR. In the extension for FHMIPv6

developed by Hsieh, the handover signal RtSolPr

was sent to PAR by MN, HI and HAck were

communicated between PAR and NAR, and PAR

sent PrRtAdv to MN. Our case required sending

RtSolPr to MAP, HI and HAck to be exchanged

between MAP and NAR and PrRtAdv to be sent to

MN by MAP. Separate provisions for FBU and

FBAck were also added. MN sends FBU to MAP

from PAR and receives FBAck from NAR.

Tunneling process starting after HI/HAck was

also implemented, by which MAP tunnels packets

destined to MN towards NAR instead of PAR. In

addition, buffering option was also added. Buffering

was implemented in the ARs, where packets are

buffered until MN attaches itself to NAR. Classifiers

had to be modified for this. Classifiers sit inside a

node and they use the computed routing table to

perform packet forwarding. The buffer used is

limited by size, number of packets it can store, and

by the time limit for which the buffered packets are

acceptable. The time limit is the time period after

which, the packet loses its significance and hence is

discarded.

4.1 Simulation Parameters

The simulation model that was used is shown in

figure 2. The model used composed of HA, CN,

MAP, ARs and other routers.

CN and HA were connected via the Internet to

MAP. Router1 was included to simulate the

connection of MAP to HA and CN via the Internet

and a delay of 50ms from MAP and a bandwidth of

100Mbps was used. Since hierarchical structure was

assumed, the routers for different subnets were

connected to MAP.

All nodes below the MAP were members of the

same domain, hence the constant delay of 2 ms was

assumed for their links. The access routers, PAR and

NAR, representing different subnets were connected

via two different Intermediate Routers (Router2 and

Router3) to MAP. The wired links were modeled as

10Mbps duplex link with 2 ms delay and 1000Kbps

duplex link with 2 ms delay, from MAP to IRs and

from IRs to ARs respectively. For the wireless

medium, the LAN 802.11 access provided by ns-2

was used.

100Mbps

50ms

Router1

100Mbps

2ms

100Mbps

2ms

(

)

(

)

2Mbps IEEE 802.11 LAN 802.11 2Mbps IEEE 802.11 LAN 802.11

1000Kbps

2ms

1000Kbps

2ms

10 Mbps

2ms

10 Mbps

2ms

Router3 Router2

MAP

(1)

(3)

(

)

PAR

(7)

NAR

(8)

IR (2)

Mobile Node

Figure 2: The Simulation Scenario

The traffic source considered was CBR, with

UDP as the transport protocol with source at CN and

Null Agent at MN. The data packet was taken to be

of 512 bytes. The Cell sizes covered by the Access

Routers were taken to be of 100 meters diameter

with some area overlapping between them. Distance

between the Access Routers was taken to be 70

meters. In each simulation run, MN starts moving

towards NAR from PAR in a straight line at 10

seconds into the simulation. The values of speed and

source data rate were varied for different scenarios.

Three speeds were considered; 1m/s (approx.

4km/h), 15m/s (approx. 55km/h) and 25m/s

(90km/h) as the pedestrian, normal vehicle and high

vehicle speeds respectively. The performance during

handover for change in the source data rate and MN

speed was studied.

4.2 Simulation Scenarios

Various scenarios were considered for simulation;

variations of packet loss, end-to-end packet delay

and handover latency with CBR rate and speed of

MN were studied. Each simulation run lasted for 60

seconds for MN speed of 1m/s and 40 seconds for

other cases.

ICETE 2005 - WIRELESS COMMUNICATION SYSTEMS AND NETWORKS

4.3 Results and Discussions

Time (sec)

Packet Unique ID

12.3 12.35 12.4 12.45 12.5 12.55 12.6 12.65 12.7 12.75 12.

590

595

600

605

610

615

620

625

630

635

Basic MIP

FHMIP

Proposed with buffer

Figure 3: Packet Arrival for the Different Schemes

Figure 3 shows the packet arrival time for three

different schemes, base MIPv6, F-HMIPv6 studied

in (Hsieh et al., 2002), and the proposed scheme.

From the figure, it can be said that the proposed

scheme performs slightly better than that in (Hsieh

et al., 2002). In addition, the packets that are lost for

the scheme in (Hsieh et al., 2002) are not lost.

From simulation results, it is seen that a packet

(packet ID 608) reaches MAP at 12.484secs. In case

of the FHMIPv6 from (Hsieh et al., 2002), the

packet gets forwarded to PAR, and hence gets lost

because MN has already left the Previous Access

Network. In the proposed scheme, however, the

packet gets forwarded towards NAR and is buffered

till MN attaches itself to NAR. Similarly another

packet (packet 609) gets lost in the former case

because it gets forwarded towards NAR but MN has

not yet established link connectivity with NAR.

CBR Rate (Kbps)

No. of Packets Lost

100 200 300 400 500 600 700 800 9

MN Speed 1m/s

MN Speed 15m/s

MN Speed 25m/s

Figure 4: Number of Packets lost for Different Cases

CBR Rate (Kbps)

Delay (msec)

0 100 200 300 400 500 600 700 800 9

No Buffering, speed of MN 25m/s

Buffering Size 6, T imelimit 35 msecs, speed of M N 25m/s

Figure 5: Handover Latency with and without Buffering

The difference in handover latencies with and

without buffering widens with increasing data rate.

The highest difference between the two latencies is

for the highest data rate under consideration, for

which more number of packets need to be stored.

The difference is shown in figure 5.

But in the latter, it gets buffered and is sent

towards MN when it establishes link connectivity

with NAR. In case of Basic Mobile IPv6, a total of

14 packets get lost (packets 735-748) in the process

of handover, without the fast handover provision.

From simulation, it was also observed that the

number of packets lost in absence of buffering is

proportional to the data rate and almost independent

of MN speed, as the lost packet number is the same

for all the speeds, except for a few cases for lower

data rates, as seen from figure 4. After the initial

transient, the packet loss shows constant linear

relationship with the data rate for the three speeds

under consideration.

Figure 6 shows the handover latency variation

with data rate. Again, it also depends more on data

rate than on MN speed. But compared to end-to-end

delay, the dependence on speed is slightly more. The

trend of handover latency with data rate is on the

increment.

CBR Rate (Kbps)

Delay (msec)

0 100 200 300 400 500 600 700 800 9

Buffer Size 8, Timelimit 35 msecs, speed of MN 1 m/s

Buffering size 6, Timelimit 35 msecs, speed of MN 15 m/s

Buffering Size 6, Timelimit 35 msecs, speed of MN 25 m/s

Figure 6: Handover Latency Variation with Data Rate

ADVANCE DUPLICATE ADDRESS DETECTION (DAD) AND BUFFERING-BASED PROVISION OF SEAMLESS

HANDOVER IN MOBILE IPV6

CBR Rate (kbps)

Avg Packet Delay (ms)

100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 90

67.565

67.57

67.575

67.58

67.585

67.59

67.595

67.6

67.605

67.61

Figure 7: End-to-end Packet Delay with Buffering

End-to-end packet delay, from CN to MN, also

has a direct relationship with data rate. However, it

is also less dependent on MN speed when compared

to data rate. The variation in the delay is almost

linear with the data rate, as evident from figure 7.

When a specific data rate was considered and the

variations of the different performance factors with

MN speed were studied, the earlier conclusion that

the factors were independent of MN speed was

verified. The variations are shown in figures 8 and 9.

Handover latency variation with MN speed is not

very significant, though some variations can be seen.

The independence of packet loss variation with MN

speed is more apparent than handover latency.

The end-to-end packet delay can also said to be

not too much dependent on MN speed, again

compared to the data rate. The variation does not

change significantly with MN speed. From figure 9,

it can be seen that initially the delay decreases with

increasing speed, but is almost constant when

saturation is reached for MN speed.

All of the performance parameters considered in

this work have been rounded off to the nearest three

digits in case of delays. Hence, these are of the order

of microseconds.

MN Speed (m/s)

Delay (ms)

1234567891011121314151617181920212223242

Figure 8: Handover Latency Variation with MN Speed

Speed of MN (m/s)

Avg Packet Delay (ms)

2 4 6 8 10 12 14 16 18 20 22 24 2

67.567

67.568

Figure 9: End-to-end Delay Variation with MN Speed

5 CONCLUSION

It can be concluded that if packets destined to MN

are forwarded towards NAR after HI/HAck, slightly

earlier than FBAck, the probability of loss of packets

is decreased, without increasing the delay

significantly.

The handover delay, end-to-end delay and loss of

packets are quite independent of MN speed

compared to data rate. In case of variable data rate,

these are more dependent on data rate than MN

speed. In case of a particular data rate also, there are

some variations, but the variations are not very

significant.

From the variations seen with MN speed and

data rate, the conclusion could be drawn that the

performance with VoIP applications, with voice

considered CBR traffic, is better than for multimedia

applications, with multimedia traffic being Variable

Bit Rate traffic.

From the simulations, it was also observed that

fast handover fails in some cases when the RtSolPr

sent by MN is not received by PAR. Hence, the cell

size, the transmission powers of Access Routers and

MN also play a significant role in the overall

performance. But these should be as small as

possible for obvious reasons. As an extension to this

work, performance with the variation in these

parameters and also with the ping-pong effect

considered could be studied.

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ADVANCE DUPLICATE ADDRESS DETECTION (DAD) AND BUFFERING-BASED PROVISION OF SEAMLESS

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