HANDOVER PERFORMANCE ANALYSIS IN MOBILE IPv6

A Contribution to Fast Detection Movement

Javier Carmona-Murillo, José-Luis González-Sánchez

Department of Computing and Telematics System Engineering, University of Extremadura, Cáceres, Spain

Isaac Guerrero-Robledo

Department of Telecom Advances Services, Next Generation Intelligent Networks Group, Atos Origin, Madrid, Spain

Keywords: Mobile communications, movement detection, FDML3, handover, Mobile IPv6, OMNeT++.

Abstract: Nowadays, mobile communications face new challenges in its evolution: The convergence of wireless

cellular networking and TCP/IP architecture. In addition, Internet protocols do not support mobility, so

different mechanisms to offer seamless mobility have been proposed. The fourth generation (4G) IP-based

wireless networks have lead IP level the ideal candidate where mobility should be implemented. Mobile IP

is the protocol proposed for mobility management at the IP layer. Handover management is one of the most

critical phases of this protocol. The high delay of this phase is a limitation to seamless mobility. In this work

a detailed analysis about handover process is presented. Moreover, movement detection is a very costly

stage in handover mechanism so a new fast movement detection algorithm to improve this detection has

been developed. It is called FDML3 (Fast Detection Movement Layer 3). As the handover analysis as the

algorithm proposed has been carried out thanks to OMNeT++ simulator.

1 INTRODUCTION

In recent years mobile communications have

changed the traditional way of Internet access.

Convergence between TCP/IP and wireless networks

is a challenge to achieve seamless mobility in

heterogeneous networks (Makaya, 2007). In this

sense, mobility management must be implemented

in a common level. IP is the best candidate to offer

this capacity (Abduljalil, 2007). However, IP

operation does not allow a node to move between

different networks without a connection disruption.

To solve this situation, IETF (Internet Engineering

Task Force) has designed Mobile IPv6 (hereafter

MIPv6) (Johnson, 2004). One of the most critical

phases in MIPv6 is the handover or handoff,

produced when a node moves to a new IPv6 subnet

while connection is still alive (Koodly, 2007).

In this work, we analyze the handover process

and a new L3 detection movement algorithm has

been developed (FDML3) to decrease the handover

delay. This work belongs to a research project called

Campus Ubicuo (Carmona-Murillo, 2007).

This article is organized as follows: Section 2

presents mobility problem in IP networks; section 3

is focused on handover analysis; the proposed

FMDL3 algorithm is explained in section 4; next,

simulation results are shown in section 5; finally,

conclusions are presented in section 6.

2 MOBILITY IN IP NETWORKS

In general, a host in the Internet changes data with

other nodes thanks to TCP/IP architecture. These

protocols were designed for fixed hosts, which are

identified by an IP address.

Convergence towards “All-IP” architectures next

generation wireless networks has made Mobile IP

(Figure 1) the main solution to offer seamless

mobility in the Internet (Le, 2006). Some approaches

to reduce movement detection latency are based on

layer 2 information. These solutions are faster than

L3 ones but have an important drawback because

they restrict the movement among heterogeneous

networks due to L2 access technology dependence.

Carmona-Murillo J., González-Sánchez J. and Guerrero-Robledo I. (2008).

HANDOVER PERFORMANCE ANALYSIS IN MOBILE IPv6 - A Contribution to Fast Detection Movement.

In Proceedings of the International Conference on Wireless Information Networks and Systems, pages 78-81

DOI: 10.5220/0002023100780081

 SciTePress

Figure 1: Mobile IPv6 entities.

3 PERFORMANCE EVALUATION

OF MIPV6 HANDOVER

Mobility protocols are designed to solve overhead,

packet loss and path recovery during handover.

Handover latency is defined as the interval starting

when the mobile node (MN) leaves the old access

medium until the communication is resumed

(Figure2). In this work a handover analysis has been

carried out, contrasting it with similar research in

this area (Cabellos-Aparicio, 2005).

Figure 2 shows handover latency components.

T1 is the L2 handover and represents 12% of the

total handover latency. T2 is the time spent by IPv6

to realize that it is attached to a new subnet and to

obtain a new IP (87%). Finally, MIPv6 operation is

carried out in T3 and is composed of the time that

the MN needs to announce its new location (1%).

Accordingly, the handover delay is given by (1):

handove

= T

L2handove

+ T

L3handove

(1)

In this work, we focus our attention in L3

handover delay (2). In detail, this time results:

L3handove

= T

IPv6

+ T

MIPv6

(2)

where T

IPv6

(3) and T

MIPv6

(4) are:

IPv6

= T

+ T

CoA

(3)

MIPv6

= T

HARe

istration

+ T

CNRe

istration

(4)

As Table 1 shows, T2 is the main responsible of

the high latency in handover process, so most of the

time (87%) is devoted to IPv6 tasks.

Table 1: Phases in MIPv6 handover.

Handover phases Time

T1 = T

L2Handover

12%

T2 = T

IPv6

87%

T3 = T

MIPv6

Figure 2: Handover latency components.

4 FDML3: A FAST DETECTION

MOVEMENT PROPOSAL

Movement detection (MD) is a crucial task in

MIPv6 handover and is based on IPv6 Neighbour

Discovery (ND) (Narten, 1998). MD in MIPv6 is too

costly in spite of modifications performed by MIPv6

in ND process. The most important modification is

to allow sending Router Advertisements (RA) more

frequently than the 3 second established in standard.

MinRtrAdvInterval and MaxRtrAdvInterval can be

set up till 0,03 and 0,07 seconds. Some studies have

provided a mathematical analysis of MD in MIPv6

(Young-Hee, 2006), (Lee, 2004). In this work, we

propose a L3 fast detection movement mechanism

called FDML3. This algorithm starts from the

research developed in (Blefari-Melazzi, 2005). The

algorithm flowchart (Figure 3) is explained next.

1. A MN detects that an unsolicited RA has been

lost. This situation is known because of the

absence of a new unsolicited RA in an interval

equal to the interval option configured.

2. MN sends a Router Solicitation to the access

router to check the bidirectional reachability.

3. If a RS is not received in an interval between 0

and MAX_RTR_SOLICITATION_DELAY (1

second), is possible to suppose that the lost has

been caused due to a mobile node movement.

4. The MN tries to connect to a new access router

to complete the handover, listening RA

messages sent by routers periodically. The

HANDOVER PERFORMANCE ANALYSIS IN MOBILE IPv6 - A Contribution to Fast Detection Movement

network prefix obtained in a RA is used to

configure the new CoA. This new IP address is

registered in the Home Agent (HA) and CN.

5 RESULTS

OMNET++ simulation scene (Figure 4) is composed

of nine routers, one of them is the Home Agent; nine

wireless access points; a MN (client1); and a CN.

The node moves in a circular path across the nine

access points (generating eight L3 handovers).

The three tests that appear in this section are:

1. L2 vs. L3 handovers in MIPv6

2. Influence of unsolicited RA interval, given by

MaxRtrAdvInterval and MinRtrAdvInterval.

3. Comparison of MIPv6 handover depending on

MD algorithm used (FMDL3 evaluation).

For each test, the following information is presented:

• Overall MIPv6 handover time (sec.).

• Data lost percentage in transmission (%).

Figure 3: FDML3 flow chart.

5.1 Link-layer Triggers

Although our proposal consider network-layer the

place where implement mobility, is important to

compare the behaviour when link-layer information

is used. As we can see in Figure 5 and in Table 2,

the difference between both times is very large.

Nowadays, handovers use L2 information to achieve

a high performance. In this test, L2 handover time is

75% less than the L3 one. This test proves the

necessity of L3 handover delay improvement to

achieve mobility in heterogeneous networks.

Figure 4: Simulation scene.

5.2 Interval between Unsolicited RAs

Routers send unsolicited RAs to advertise its

presence to other nodes in an interval defined by

MaxRtrAdvInterval and MinRtrAdvInterval. MIPv6

modify the default values of these parameters to

allow fast movement detection in network layer.

Figure 6 shows L3 handover delay in four

configurations, where these two parameters change

its values. Obtained data are also shown in Table 3.

If routers send unsolicited RAs fast, the time needed

to detect the movement is shorter. However, a low

configuration of these parameters causes an extra

overload in the network. As in test before, packet

loss is lower according to the time of the process.

Table 2: Simulation data. L2 triggers.

L2 handover L3 handover

Hand. Time 0,58 2,3

Packet loss 1,71 2,77

Table 3: Simulation data. Unsolicited RA interval.

0,5–1,5 0,3-0,1 0,25-0,75 0,1-0,3 0,03-0,07

Hand. time 2,30 1,32 0,96 0,18 0,15

Packet loss 2,76 2,20 1,87 1,47 1,21

Figure 5: Handover delay with and without L2 triggers.

WINSYS 2008 - International Conference on Wireless Information Networks and Systems

Figure 6: Handover delay. Unsolicited RA interval.

5.3 FMDL3 Evaluation

This proof checks the behaviour of the proposed

FMDL3 algorithm comparing it versus the defined

in (Johnson, 2004). Figure 7 and Table 4 shows the

simulation results. When FDML3 is used, handover

delay is reduced in an average of 25,6 %.

With this new mechanism, if unsolicited RA

interval established is low, the handover delay

improvement is not so high; however a configuration

like this provokes a high amount of signalling traffic

in the network, so this configuration will not be

chosen usually. This means that FDML3 algorithm

will improve the delay of the overall handover

process in MIPv6 protocol, minimizing connection

disruption while the mobile node moves among

heterogeneous networks.

Table 4: Simulation data. FDML3 algorithm.

With FDML3 Without FDML3

Hand. time 1,63 2,19

Packet loss 3,62 4,04

Figure 7: Handover delay improvement with FDML3.

6 CONCLUSIONS

In this work a MIPv6 handover evaluation is

presented, checking each phase of the process. This

analysis has been carried out using OMNeT++

simulator. Obtained data shows that there is a phase

very costly in time terms (87% of the process). In

this stage movement detection is performed, so it is

a critical part of the process. Due to this limitation, a

new fast movement detection algorithm has been

developed: FDML3. With this algorithm, the overall

delay is improved up to 25%.

Although this research work reduces the

handover delay, there are other important sources of

delay in MIPv6 handover: Router advertisement,

duplicated address detection (DAD) and Binding

Update RTT. The study and improvement of these

topics is presented as future work.

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HANDOVER PERFORMANCE ANALYSIS IN MOBILE IPv6 - A Contribution to Fast Detection Movement