ap ipv6.pdf

8/11/2019 AP IPv6.pdf

1/12

Published in IET Networks

Received on 15th July 2012

Revised on 13th March 2013

Accepted on 17th March 2013

doi: 10.1049/iet-net.2012.0141

ISSN 2047-4954

Adaptive quality of service aware multi-mobilityanchor point registration in hierarchical mobile IPv6wireless access networksAna Mirsayar Barkoosaraei, A. Hamid Aghvami, Paul Pangalos

Institute of Telecommunication Research, Kings College London, London WC2R 2LS3, UK

E-mail: [email protected]

Abstract:In hierarchical mobile IPv6 (HMIPv6), mobility anchor points (MAPs) are introduced to reduce the signalling cost bylocalising the signalling trafc of mobile nodes (MNs). However, the presence of MAPs introduces areas of bottleneck within thenetwork. This study evaluates the impact of overlapped domains of consecutive MAPs in HMIPv6 access networks. In this novelnetwork architecture, an MAP registration algorithm is also proposed to enable MNs to register with more than one MAPsimultaneously. For each ow, the proposed algorithm determines a primary and a secondary MAP according to the qualityof service (QoS) requirements of the trafc ow. Load balancing is also introduced to provide an even distribution of loadamong MAPs. In addition, an extended router advertisement is proposed to enable multiple MAP registration of MNs. Theimpact of the proposed algorithm in the new HMIPv6 network architectures is compared with a non-QoS aware multi-MAPregistration algorithm in access network with no overlapped MAP domains. The simulation-based comparison study illustratesa maximum of 71 and 74% improvements in total amount of rejected bandwidth and the mean satised ow requests innetwork, respectively.

1 Introduction

The growth in the number of mobile wireless devicesaccessing IP-based networks has introduced the need forefcient mobility support. It is notable that many of thenetwork control points and devices operate on IPv4 protocols.

Proxy mobile IPv6 (PMIPv6) is a network-based IPprotocol, as opposed to the host-based mobile IPv6(MIPv6) [1] protocol. PMIPv6 provides mobilitymanagement support for the mobile nodes (MNs). Thedrawbacks of PMIPv6 have been documented in theliterature. In [2], a multihoming extension to PMIPv6

protocol is proposed to enable mobile devices to connect tomultiple networks simultaneously. Also in [3], an improvedmulticast handover procedure is introduced to optimisemulticastgroup management in PMIPv6. The proposedmanagement minimises the service interruption time and

prevents the multicast packet loss during handovers.The aim of this paper is to shed more light on the

performance improvement of the hierarchical mobile IPv6(HMIPv6)-based access networks by proposing a novelnetwork architecture. Primarily, MIPv6 was proposed to

provide IP connectivity to MNs that change their wirelessIP point of attachment. In MIPv6 binding update (BU)messages are sent to the corresponding nodes (CNs) and the

home agent (HA), at every change in MNs point ofattachment. Consequently, large handover signallingoverhead is generated. The drawbacks of MIPv6 have beenwell documented in the literature [4]. Mobility agent

(MA)-based family protocols were proposed to minimisesuch delay [5].

In the MA-based micro mobility solutions, each accessrouter (AR) has one MA. When an MN enters into thisaccess network, it registers itself with the MA. The CNsand HA have the MA registered address of the MN andsend all packets to the MA. The MA in turn tunnels packetsto the MN. In [6], it is shown that the presence of MAs inaccess network increases congestion, and reduces thenetwork throughput. Also in [7], it is proved that the

presence of MAs reduces the capacity of the accessnetwork, since both uplink and downlink trafcs are forcedto ow through a small number of MAs.

1.1 Related works

In large-scale wireless mobile IP networks, more than oneMA may be deployed in the same hierarchy level, in orderto provide more scalable and robust mobile services [8]. Inthe HMIPv6 networks, MAs are referred to as the mobilityanchor points (MAPs). In order to support registration of anMN with multiple MAPs, a multiple MAP registrationmechanism is required. In addition, prior to the MAPregistration process an intelligent MAP selectionmechanism is essential, so the MNs can select the most

suitable MAPs to reduce the total cost (i.e. packet delay andhandover delay costs) among the available MAPs in thenetwork. Here, the term available means the MAPs that areadvertised by MNs current AR.

www.ietdl.org

176 IET Netw., 2014, Vol. 3, Iss. 3, pp. 176186

& The Institution of Engineering and Technology 2014 doi: 10.1049/iet-net.2012.0141

8/11/2019 AP IPv6.pdf

2/12

Selecting an optimal MAP is a well-researched area andmany MAP selection mechanisms have been proposed in[79] and several other documents. However, each of theseschemes considers only certain specic characteristics and

possesses its own advantages and disadvantages [10].

1.2 Novelty and contributions

Overlapping MAP domains enable each AR to be managedby more than one MAP, which has an impact on the trafcload distribution in the network [11]. Consequently, the

performance of the entire network is inuenced. Intuitively,by allowing ows of a populated AR to ow through morethan one MAP, the bottleneck effect of MAPs on wirelessaccess networks can be reduced or avoided. Furthermore,less congestion translates to less packet delay at the MAPs

because of queuing. In [12], three heuristic, KernighanLin-based partitioning algorithms are proposed to assignARs to MAPs and create overlapping MAP domains. Theaim was to minimise the total inter-area handover rate and

bottleneck effect of MAPs in HMIPv6 access networks.In [13], a robust hierarchical mobile IPv6 (RH-MIPv6) was

proposed to enable MNs to register with more than one MAP.However, the MAP selection is carried out randomly andMNs register with MAPs regardless of quality of service(QoS) requirements of trafc ows. Nevertheless, an MNneeds to consider several factors when selecting an optimalMAP that minimises the total cost among various MAPsavailable in a foreign network.

In this paper, an adaptive QoS aware multi-MAPregistration algorithm is proposed. Taking the ow-basedapproach to micro mobility management; the proposedMAP selection algorithm takes into consideration the loadstatus of MAPs along with the QoS requirements of ows.

The proposed algorithm separates the MAP selectionprocess for the high priority (HP) (i.e. ows with high QoSrequirement) and low priority (LP) ows (i.e. ows withlow QoS requirement). That is, for each HP ow, MNselects an optimal MAP with respect to ows QoSrequirement, and for each LP ow, an MAP selectionmechanism is introduced to enable a more efcient use ofnetwork resources with the purpose of load balancing in thenetwork. Moreover, an extended router advertisement(ex-RA) is proposed to operate in conjunction with the

proposed algorithm.The remainder of this paper is organised as follows. In

Section 2, the overlapping MAP domain scheme isintroduced. In Section 3, the non-QoS aware MAP selectionalgorithm in multi-MAP domain environment is outlined.The proposed QoS aware MAP selection algorithm in amulti-MAP domain HMIPv6 access network is outlined inSection 4. In Section 5, the denitions and notations usedin mathematical modelling of the proposed MAP selectionalgorithm are dened. Mathematical formulation of usermobility model is provided in Section 6. Section 7mathematically models a packet delay cost in network. InSection 8, the mathematical formulation for selecting theleast utilised MAP is provided. Section 9 provides aload-balancing model. In Section 10, the implementationsteps of the proposed algorithm are presented. In Section 11,the performance of the proposed algorithm is evaluated as a

function of degree of load balance and total amount ofbandwidth rejection in HMIPv6 access network withoverlapped MAP domains. Finally, Section 12 concludesthe paper.

2 HMIPv6 and MAP domain overlap

HMIPv6 [7] is an MA based micro mobility protocolproposed by internet engineering task force to mitigate thesignalling cost and handover delay in an MIPv6, whenMNs perform frequent handovers. In HMIPv6 networks,MAPs handle BU procedures locally because of handoverswithin an MAP domain.

In HMIPv6, when an MN enters a new MAP domain, itreceives RA messages. The MN congures twocare-of-addresses (CoAs) and sends a local binding update(LBU) message, to bind its local-care-of-address (LCoA)with MAPs regional-care-of-addressed (RCoA). The MAPstores the binding in the binding cache (BC) and forwardsthe BU to the MNs HA and CNs. HA and the CNs areonly aware of the RCoA of the MN. All the trafcoriginated from or terminated at the MN ow through theMAP. When the MN moves within an MAP domain (by

performing an intra-domain handover), it only needs toregister the new LCoA with the MAP, by sending an LBU.The RCoA does not change as long as the MN moveswithin the same MAP domain; hence mobility signallingdoes not leave the access network. If the MN migrates

between different MAP domains (by performing aninter-domain handover), it has to inform the HA and CNsof the change by sending global binding updates (GBUs).In such architecture, an MAP is a single point of failure. Ifit fails, its BC content will be lost. It is important forcommunication networks to eliminate single points offailures to provide high QoS. Thus, a network structureshould have some redundancy to avoid it.

An MAP domains boundary is dened by ARs advertisingthe MAP information (MAP option) through RA, to the MNsconnected to them. Fig. 1 depicts a basic HMIPv6-basedarchitecture, where domains of MAPs are partially

overlapped. As an HMIPv6-aware MN (e.g. MN 1) entersthe access network, it receives MAP options, included inex-RA (introduced in Section 4.4.2) from its correspondingAR (AR 3), regarding available MAPs (e.g. MAP 1 andMAP 2). For each incoming ow, the MN selects the mostsuitable MAP to satisfy the QoS requirements of that ow(i.e. throughput and reliability). The MAP selection takes

Fig. 1 Handover siganlling in an overlapped MAP domain

topology in HMIPv6 network environment

www.ietdl.org

IET Netw., 2014, Vol. 3, Iss. 3, pp. 176186 177

doi: 10.1049/iet-net.2012.0141 & The Institution of Engineering and Technology 2014

8/11/2019 AP IPv6.pdf

3/12

place by implementing the proposed algorithm, according tothe information provided in MAP options.

ARs located in overlapped areas of MAP domains (AR 3)are enabled to distribute the load associated with them overmore than one MAP. Therefore when the current MAP (e.g.MAP 1) is overloaded, the MNs connecting to AR 3 can bemanaged by other available MAPs (e.g. MAP 2). Thereforenetwork is capable of managing more number of MNs by

means of balancing the trafc load among MAPs.

3 Robust hierarchical mobile IPv6

RH-MIPv6 provides fault tolerance and robustness innetworks. In such architecture, the MN congures twoRCoAs. One is the primary RCoA and the other is thesecondary RCoA (S-RCoA). MN registers both of theRCoAs to the corresponding MAPs. The multiple RCoAsare congured in advance and are dynamically changedafter failure detection by MNs or CNs.

In this scheme, each MN registers with two MAPsregardless of the QoS requirements of trafc ows (e.g.

throughput, delay sensitivity and reliability) or MAP

s loadstatus.

4 Adaptive QoS aware multi-MAP selectionalgorithm

4.1 Overview

Selecting an appropriate MAP plays an important role inproviding sufcient mobile services. The non-optimal MAPregistration, proposed in [13], leads to service interruptionof HP ows, such as Voice over IP. This is because ofinefcient use of resources in the network, and an unevendistribution of network load. Therefore some MAPs become

bottlenecks in network, whereas others are underutilised.Also in [13], the dynamic change of registered RCoAs isonly triggered by MAP failure detection. This interprets tothe deciency of this mechanism to recover from MAPoverload and to avoid MAPs from becoming congested.This forms the motivational basis of proposal of theadaptive QoS aware multi-MAP selection algorithm.

The proposed algorithm separates the selection scheme forthe HP and LP ows, and considers several parameters in theMAP selection process to minimise the total cost amongvarious available MAPs.

Sections 4.2 and 4.3 give details about how the MAPrelated information is obtained, so as to the most

appropriate MAP is selected, by employing the proposedalgorithm, explained in Section 4.4.

4.2 Initialisation

Every time an MN enters an access network, it receives anex-RA (introduced in Section 4.4.2) from its current point

of attachment (or AR) and stores the received MAP option(s) of the available MAPs in its MAP list. Storing theoptions is essential, as they will be compared with otheroptions received later.

This MAP list consists of the hop-distances to each MAP,which is obtained from the dist eld of MAP options.Section 6 explains how the handover delay cost iscomputed in the access network. The list also consists of

the current load status of MAPs, obtained from the MAPutilisation eld of MAP options. The restriction imposedon MAP bandwidth availability because of the capacityconstraint, makes bandwidth availability an essential inputto the proposed algorithm. The proposed algorithm makesuse of the information conveyed in these elds to determinethe packet delay cost imposed by each available MAP,depending on the hop-distance and the load status valuesincluded in the MAP options. The MAP utilisation eldinformation can also be used to enforce load-balancing

policies or mechanisms in the network.

4.3 QoS estimation

Trafc classes differ in their QoS requirements as displayed inTable1.

4.4 QoS aware MAP selection

In our proposed MAP registration algorithm, the salientassumption is that the MAP selection process takes place ona per-ow basis. It is also assumed that the differentiatedservices (DiffServ) [14] are used as the QoS forwardingarchitecture in the HMIPv6 access network. Diffserv usesthe six-bit differentiated service code point (DSCP) in theDifferentiated Service (DS) eld in the header of IP packetsfor packet classication purposes.

4.4.1 QoS mapping to the DSCP values of the IPpacket: Eight bits are allocated to type of service (ToS)eld in the IP header [14]. It denes a mechanism forassigning a priority to each IP packet and a mechanism torequest specic treatment such as high throughput, highreliability or low latency. The upper six bits contain DSCP,and the remaining two bits are reserved.

MNs associate these delivery priority values to differentiatebetween the packets generated by them.

The rst six bits of DSCP are dened as follows

service T = b0

, b1

, b2

, b3

, b4

, b5

The three precedence bits from 0 to 2 are used to indicate thepriority of a packet. The higher the value of the IP precedenceeld, the higher the priority of the IP packet. For example

precedence 1 [0 0 1] indicates priority. The fourth bitindicates whether low delay is preferred, the fth bit

Table 1 Various traffic types and their characteristics

Traffic type Application Class Delay tolerance Bandwidth request

conventional voice (phone) 1 extremely low 150 KBpsvoice(teleconference) 2 low 500 KBps

streaming real-time 3 low 250 KBpsnon-real-time 4 low 250 KBps

interactive web browsing 5 high 100 KBpsbackground email, data transfer 6 high 200 KBps

www.ietdl.org



8/11/2019 AP IPv6.pdf

4/12

indicates whether high throughput is preferred and the sixthbit indicates whether reliability is preferred.

We dene a Boolean decision variable for each of thesethree bits as follows

D =1, packet requests low delay

0, otherwise

(1)

T=1, packet requests high throughput

0, otherwise

(2)

R =1, packet requests high reliability

0, otherwise

(3)

The endpoint is the most knowledgeable component in thenetwork as it understands applications. Therefore MNsidentify the trafc type and estimate the QoS requirements(e.g. delay and bandwidth guarantee) of the incoming ow.Various methods maybe used for this purpose, such asemployment of packet inspection [15], however, this lies

beyond the scope of this paper.For each incoming rst marked packet of a ow at ARm,

MN checks the DS eld bits, and then selects an MAP amongthe available MAPs, which meets the ow QoS requirements.

Note only the delay sensitive ows are considered as HPows and the rest are considered as LP ows. The three

possible QoS requirements are

if [D T R] = [10 0], low delay is requested. if [D T R] = [1 10], high throughput is requested. if [D T R] = [10 1], high reliability is requested.

By knowing the D, T and R bits, the proposed MAPselection mechanism (described in Table 2) is executed.

For the best-effort trafc, considered as LP class of trafc, aload-balancing mechanism (described in Section 8) isdeployed, which works towards distributing the load evenlyamong MAPs.

4.4.2 Extended router advertisement: Routersolicitations (RSs) and RAs help the MN to identify that ithas changed its subnet and to provide the MN with thenecessary information to congure a new CoA. A novel RA

protocol as an extension to the standard RA is introduced,to include the network measurement information. It utilisesthe bits in the reserved eld to disseminate MAPs currentload status. This eld is renamed as MAP utilisation eld,

and the protocol is referred to as the ex-RA. Fig. 2 depictsthe modied MAP option format.

Similar to MIPv6, ARs send ex-RA messages both on aregular basis and in response to MNs requesting for themthrough RS messages [7]. There is a tradeoff betweenaccurateness of MAP selection and the sorting cost of MAPoptions by MNs. If the number of ex-RA is WRA, then thesorting cost is regarded as WRAlogWRA [16]. The moreoften the ex-RA is sent, the more accurate the MAPselection; however, the more sorting cost and powerconsumption.

4.4.3 Signalling procedure for multi-MAP

registration: Fig. 3 shows how an MN registers withmore than one MAP simultaneously in a multi-MAPdomain HMIPv6 network.

When an MN connects to a new AR, it obtains an ex-RAmessage, containing information on locally available MAPs(e.g. load information, hop-distance, RCoA, Life time etc).Then, BUs are invoked by the MN. BU in the multi-MAP

per domain environment is similar to that of the HMIPv6.However, other than MAPs keeping binding informationabout MNs LCoA, and RCoA in their BC, MNs and CNskeep binding information of MNs RCoAs. HA and CNsidentify an MN with only one RCoA at any instant of time,which is related to the MNs current supporting MAP [orthe primary MAP (P-MAP)]. The P-MAP is selected

through implementation of procedures explained in Sections4.2, 4.3 and 4.4.

After the MAP selection stage, MN sends an LBU messageto the MAP, which binds its LCoA, with MAPs RCoA asMNs P-MAP. The RCoA is registered with the HA and theCN of the MN. The MN must not use one RCoA (e.g.RCoA 1) derived from an MAPs prex (e.g. MAP 1) as aCoA in its BU to another MAP (e.g. MAP 2). This wouldforce packets to be encapsulated several times (twice in thisexample) on their path to the MN. Subsequently, the MNalso registers its LCoA with a secondary MAP (S-MAP)and registers its S-RCoA with the HA and the CNs. A newag is added to the BU message to differentiate between

the primary and secondary RCoA [17]. The secondaryRCoA is used by the MN in the following cases:

change in capability of the P-MAP (e.g. when P-MAPbecomes overloaded); MAP failure.

Fig. 2 MAP option format in proposed ex-RA

Table 2 Algorithm-i

1 If flownarrives at AR mM2 IfD= 13 FindMAPs4 where for each k

5 LTlikn, Han

6 DTn , Dan

7 m[

Mk

n

Bn

mk

.xnm

.zmk

+ hk

zk8 IfR= 1

9 ndMAP k10 (14)(18)11 IfT= 112 ndMAP k13 (32)(35)14 IfT= 0 and

R= 015 ndMAP k16 (28)(31)17 End18 End19 End20 Else if D= 021 Findan

MAP

22 (35)

(38)23

End

End

www.ietdl.org



8/11/2019 AP IPv6.pdf

5/12

When either of the above scenarios arises in an accessnetwork, MN selects the S-MAP from its BC and sendsdata through the S-RCoA to CNs. The CNs consider theP-MAP has failed when they receive packets from S-RCoA.Consequently, CNs update their BCs. The MN sends a BUwith the S-CoA to HA as soon as possible.

CN acts in a similar manner to the MNs procedure in thementioned scenarios. In such conditions, CN searchesthrough its BC and sends the data through the S-MAP (i.e.the S-RCoA of the MAP was congured in advance andstored in the CNs BC). If an MN receives packets from theS-MAP, the MN considers that P-MAP is no longer used.

Then, the MN sends GBU to HA and to the CN to updatetheir BCs.

This mechanism steers IP ows from one MAP to another,while providing uninterrupted services to MNs. Note thatonly the non-real-time IP ows are redirected. As a result,MNs do not generate long BU registration delays as theirLCoAs are registered with the S-RCoAs prior to the needfor use of the S-MAP.

5 Network model

An access network is dened as a given undirected graph G(V, E), where V is the set of nodes andE is the set of links

interconnecting nodes. Let K V be the set of routers thatserve as MAPs, and R be the number of MAPs in theaccess network. LetM Vbe the set of ARs in the networkand N V be the set of MNs. For a given AR m M, let

KmKbe the set of MAPs that are advertised by ARm. LetMmMbe a set of ARs adjacent to ARm, andkKm be agiven MAP. Letkrepresent the capacity of each MAP k.

6 Analytic user mobility model

In this section, taking into account several parameters, a costfunction for total handover signalling delay cost is developed.

Handover latency is dened by many factors such asmovement detection delay (MDD), address congurationdelay (ACD), and the location update delay. A number ofsolutions exist to minimise the MDD and ACD delays, tonegligible amounts [18]. This paper focuses on the costattributed to the location update signalling delay.

The cost is built assuming a single MAP hierarchy.

6.1 Location update cost

Based on the location update model derived in [19], locationupdate costs because of intra-domain and inter-domainhandovers are developed in this section.

6.1.1 Unit intra-domain handover location updatecost: The cost of sending a BU message and receiving a

binding acknowledgement from MAP k, during anintra-domain handover, is directly proportional to thehop-distance between the AR m and MAP represented byhARmMAPk. Let and be the unit costs when a locationupdate procedure is performed in wireless and a wired link,respectively. The unit intra-domain handover locationupdate cost between AR i and AR m located in an MAPdomain is dened as follows [19]

Hinimk= h+ hARmMAPk v

2 (4)

6.1.2 Unit inter-domain handover location updatecost: Inter-domain handover is dened as the cost ofsending the GBU from an AR m to the GW, whiletraversing MAP k, plus the hop-distance from the GW toHA and CNs. The unit inter-domain handover locationupdate cost because of an inter-domain handover betweentwo ARs (AR i and AR m), allocated in different MAPdomains, is expressed as follows [19]

Houtimk= v. lARmMAPk + C

2 (5)

We deneCas a xed number of hops between the GW andHA, and the CN, which is dened as

C= hGWCN + hGWHA (6)

In addition, lARmMAPk, is dened as follows

lARmMAPk = hARmMAPk + hMAPkGW (7)

Similarly, hMAPkGW represents the hop-distance betweenMAPkand GW.

6.2 Probability of MNs performing handover and

MNs movement direction

Trafc is modelled as ow requests. Incoming ows areassumed to arrive independently following Poisson

Fig. 3 Flowchart of MNs operation

www.ietdl.org



8/11/2019 AP IPv6.pdf

6/12

distribution with an average value . The ow holding timeand residence time are assumed to be exponential randomvariables with mean andn minutes, respectively.

Fig. 4 illustrates the handover probability for a variety ofow holding times and residence times. The smaller theresidence time, the higher the mobility speed. Also theaverage handover probability of ows decreases bydecreasing the mean rate of incoming ows to the access

network. One of the MAP selection criteria is the handoverdelay cost. Therefore the mobility pattern has a great impacton performance of the proposed algorithm.

Similar to [11], the probability of an MN performinghandover and the MN movement direction, and theinternal and external costs of ARs are taken into accountto model the expected handover signalling overhead in thenetwork. Let im be the handover probability of an MNfrom AR i to AR m, (referred to as the direction

probability of AR m), and let i be the probability of anMN being attached to AR i (referred to as the demand

probability).

6.3 Handover signalling delay cost

In order to be able to express the handover signalling delaycost in a mathematical programming setting, we dene thefollowing Boolean decision variables:

xnm = 1, flow n is connected to ARm

0, otherwise

(8)

yimk =

1, if AR i and ARjare assigned

to MAPk

0, otherwise

(9)

zmk = 1, AR m is assigned to MAPk

0, otherwise

(10)

For each ow n attached to AR m, the total expectedintra-domain and inter-domain handover signalling costs

between two adjacent ARs i and m are the probability ofhandover occurrence multiplied by the handover cost,

which is given as (4) and (5), respectively

Linim =

k[km

j[Mi

Hinimkyimk xni ri aim

i [ M, n [ N

(11)

Loutim = k[km

m[Mi

Houtimk 1 yimk xni ri aimi [ M, n [ N

(12)

In RH-MIPv6, when an MN attaches to an AR (ARc) that canaccess more than one MAP, the probability of any of theaccessible MAPs to be selected follows a uniformdistribution. Then, MN registers with an MAP (MAPc). TheMN migrates to a new AR (ARn) coverage area accordingto the direction probability of its ARc. If ARn can accessMAPc, then the handover is classied as an intra-domainhandover, otherwise an inter-domain handover. However,

by an intelligent selection of MAP, the handover delay canbe reduced considerably. In view of that, an MAP selection

algorithm is proposed in Table2.LetN

rNrepresents a subset ofows with high reliability

requirements. For each n Nrattached to ARi, the handover

signalling cost imposed by each MAPkaccessible by ARi iscomputed. The cost is sum cost of expected intra-domain andinter-domain handover signalling costs, formulated in (11)and (12), respectively

LTikn = Linim +L

outim, k[ Ki,

n [ Nri [ M, m [ Mi(13)

For each ownNr, the objective is to select an MAP, where

the handover signalling delay cost is minimised.

L = mink[Ki

LTikn

(14)

Subject to

2yimk zmk+zik, m, i [ M, k[ K (15)kzmk 1, m [ V (16)

m[M

xnm = 1, n [ Nr (17)

xnm, zmk, yimk[ 0, 1{ }, n [ Nr

i, m [ M, k[ K (18)

Constraint (15) ensures thatyimkcan only take the value 1 ifboth nodes i and m are assigned to MAP k, constraint (16)ensures each AR is assigned to at least one MAP, whereasconstraint (17) ensures each ow is attached to one AR andconstraints (18) ensure that xnm, zmk and yimk are binaryvalues (e.g. either 0 or 1).

7 Packet delay cost

7.1 Average packet delay model in the accessnetwork

The average packet delay cost consists of the delay costs ofthe propagation, processing and queuing [6]. The queuingdelay can be deemed negligible, when the trafc load isFig. 4 Hanover probability against residence time

www.ietdl.org



8/11/2019 AP IPv6.pdf

7/12

well below the capacity of the network (unloaded network).When MAPs are deployed in the network topology,creating bottlenecks, queuing needs to be explicitly taken inconsideration. The processing delay incurred by a networkentity, depends on its load status. We assume thetransmission delay cost is proportional to the distance

between the source and destination. The longer the distanceis, the larger is the round trip time experienced by MN.

7.2 Queuing delay cost

Using Kleinrocks independence approximation [20], eachlink/edge can be modelled as an M/M/1 queue. It isassumed that bottlenecks are at MAPs in the network.

LetBnmkbe the bandwidth request associating with ow n,attached to ARm and traversing MAP k. We dene the total

bandwidth utilisation of MAP k, as follows

hk=

m[M

n[N

Bnmkxnm zmk

, k[ Km (19)

By Littles law, the packet queuing delay cost in MAP k is

modelled as follows

PAPQk =

1

6k hk(20)

Hence, the packet queuing delay cost at MAP kexperiencedby own, connected to ARm, is as follows

PAPQnk =

1

6k hkxnm zmk

i [ V, k[ Km

(21)

7.3 Transmission and the processing delay costs

In this section, the transmission and the processing delaycosts at each network entity such as HA and MAP aredeveloped, based on the model derived in [21]. The sumtransmission and the processing delay cost (referred to asthe packet delivery cost) incurred from the CN to an MAPis presented as follows

DCNMAP

= l b hCNHA + hHAMAP

+ l E(S) 1 b hCNMAP+ lPHA

(22)

wherehijrepresents the distance between the two entities ofiandjin the network andE(S) is the averageow size (in theunit packet). In addition, is the unit transmission cost in awired link andPHAdenotes the processing cost at the HA.

Similarly, the packet delivery cost from an MAP to ARDMAPAR is as follows

DMAPAR= lE(S) PMAP b hARMAP

(23)

where PMAP is the processing cost of the MAP, including alookup and a packet encapsulation/decapsulation costs. The

lookup cost of an MAP is assumed to be proportional to thelogarithm of the number of ows managed by that MAP[21] and the packet encapsulation/decapsulation cost is aconstant value. Hence, the processing cost of MAP k is as

follows

PMAPk = d logn

m[Mk

xnm

+O (24)

is a weighing factor and O is the encapsulation anddecapsulation cost.

The last component is the packet delivery cost in thewireless link between AR and MN, denoted by D

ARMN.

DARMN = lE(S) j (25)

where is the unit transmission cost in wireless link.Let NdN represents a subset of ows with low delay

tolerability. Hence, the average packet delivery cost ofMAP k experienced by ow n, connected to ARm, is asfollows

Dtotalnk = DCNMAPk +DMAPARm +D

ARmMNn

xnm zmk,k[ Km

(26)

Using (26) and (21), the packet delay cost at MAPkforown, connected to ARm, is given as

DTn = Dtotalnk +D

APQnk , i [ V, k[ Km, n [ Nd

(27)

For each ow nNd, the objective is to select an MAP, wherethe packet delay cost is minimised

D =n[Nd, k[Km DTn

(28)

subject to

k

zmk 1, m [ V (29)

m[M

xnm = 1, n [ Nd (30)

xnm, zmk, yimk[ {0, 1}, n [ Nd

i, m [ M, k[ K(31)

Constraint (29) ensures each AR is assigned to at least oneMAP, constraint (30) ensures each ow is attached to oneAR, and constraints, whereas constraint (31) ensures thatxnm, zmkandyimkare binary values (e.g. either 0 or 1).

8 Flows with high-throughput requirement

In this section, a linear problem formulation of selecting theleast utilised MAP for a ow with high-throughputrequirement is provided. LetNtN represents a subset ofows with high-throughput requirements and B

nmk be the

bandwidth request associated with ow n, attached to AR

m. The least utilised MAP based on (19), is given as follows:

h = mink[Km

hk

(32)

www.ietdl.org



8/11/2019 AP IPv6.pdf

8/12

subject to

m[Mk

n

Bn

mk xnm zmk

+ hk 6k (33)

Bn

mk 0, n [ N, m [ V, k[ K (34)

xnm

, zmk

, [ 0, 1{ }, n [ Nt, m [ M, k[ K (35)

Constraint (33) ensures MAP capacity is satised for allMAPs, constraint (34) ensures bandwidth requirement ofows are non-zero and constraint (35) ensures that xnm andzmkare binary values (e.g. either 0 or 1).

9 Load balancing model

An MAP is congested when its total bandwidth utilisationexceeds the bandwidth utilisation threshold. The thresholdis dened as 80% of the MAPs total capacity. Assumingthat 80% is the expected trafc percentage.

In the proposed algorithm, for HP ows, MAPs areselected to satisfy the ows QoS requirements, whereas anew MAP selection mechanism is proposed for LP trafcows. The objective is for each LP ow, an MAP isselected to provide better load balance within network.

Based on the load balance model derived in [22], wedevelop a balance criterion as follows:

An MAP domain kis balanced if all MAP domains satisfythe balance criterion

hlow

hk

hup (36)

where

hlow

= htotal

/R 1 w (37)

hup

= htotal

/R

1 + w

(38)

Also total is dened as follows

htotal

=

k

hk, k[ K (39)

total

represents the total bandwidth request in the network.low and up represent the lower and upper bandwidth

utilisation thresholds for each MAP domain, respectivelyand is a parameter satisfying 0 < < 1. Constraints (37)and (38) specify a range for MAP k, within which the MAP

is accepted as balanced. The smaller the value, the tighterthe constraint is. The value 0.1 is used for in ourimplementation as in the similar work [22]. Therefore foreach LP ow, MN selects an MAP, which provides the bestload balance in the network.

10 Proposed algorithm

Every time an MN enters an access network, it receives anex-RA (introduced in Section 4.4.2) from its current pointof attachment and stores the received MAP option(s) of theavailable MAPs in its MAP list. The MAP list consists ofthe dist eld, MAP utilisation eld (introduced in

Section 4.4.3).MNs extract the necessary information received in MAP

options for available MAPs (e.g. hop-distance and the MAPtrafc load status) and determine the handover delay cost

(formulated by (13) in Section 6.3) and the packet delaycost (dened in (26) in Section 7.3) imposed by eachavailable MAP.

MNs identify the trafc type and estimate the QoSrequirements of the incoming ow and use delivery priorityvalues to differentiate between the packets generated bythem (explained in Section 4.4.1). By knowing the D, Tand R bits (the fourth, fth and sixth bits of the DSCP in

the IP header), the proposed MAP selection mechanism(described in Table 2) is executed. There are three possibleQoS requirements, (i) low-delay requirement, (ii) highthroughput requirement and (iii) high reliabilityrequirement. Line 1: in the proposed algorithm, for HPows, MAPs are selected to satisfy the ows QoSrequirements. Lines 2, 3, 4, 5, 6 and 7: let Dan and Hanrepresent the minimum acceptable bound for requiredhandover delay and packet delay for ow n, respectively.Using this information, for each ow n, if ow is delaysensitive, the algorithm selects a serving MAP to satisfy theows QoS. Therefore MAPs that meet the acceptablehandover delay (line 5), packet delay (line 6) requirementsof the ow and also meet the MAP capacity constraint (line7) are selected. The MAP capacity constraints ensure thatthe total amount of trafc load going through each MAP isnot greater than the capacity of that MAP. Then

lines 8, 9 and 10: ifow requires high reliability, the MAPwith minimum handover delay cost is selected; lines 11, 12 and 13: ifow requires high throughput, theleast utilised MAP is selected; and lines 14, 15 and 16: if ow requires high reliability, theMAP with minimum packet delay cost is selected.

Lines 20, 21 and 22: for the best-effort trafc, consideredas LP class of trafc, a load-balancing mechanism is

deployed, which selects an MAP to meet the balancecriteria dened in (36) and works towards distributing theload evenly among MAPs.

Table2 shows how the most suitable MAP is selected.

11 Simulation setup and evaluation

A simulation-based study is developed using MATLAB,which supports hierarchical mobile IP architecture. Fig. 5outlines the network simulation topology. Dashed linesshow possible user movements between ARs, and solidlines present wired links between routers. The ARs areconnected to MAPs through intermediate routers, having

point to point wired links, with 10 ms delay allocated toeach link. The MAPs are connected to HA and CN viawired network. The choice of having a one layer MAPhierarchy is to focus the research on the overlapping MAPdomains in a single hierarchy level.

By expanding the size of the MAP domain overlappingregions, the trafc ows are more evenly distributed in thenetwork. This is achieved by making the residual capacityof the lightly loaded MAPs available to ARs located in theoverlapped regions of MAP domains. Implementationsnetwork partitioning in real-time requires the size ofoverlapping regions between MAP coverage areas todynamically shrink or expand depending on MNs mobility

parameters, addressed in details in [11]. However, this liesbeyond the scope of this paper. Over expanding the MAPdomains over the neighbouring domains increases theintra-domain handover rate considerably. Hence, the total

www.ietdl.org



8/11/2019 AP IPv6.pdf

9/12

handover signalling overhead in the network increases as aresult of overlap formation instead of being decreased. Inaddition, as the number of ARs located in the overlappingregion expands; the residual capacities of the MAPs to

which ARs are assigned to is shared by the new AR(s).Hence, reductions in load concentration on the congestedMAPs are achieved with the cost of an increase in trafcload on the new MAP. However, once MAPs reach theirmaximum capacity usage, further expansion of overlappedregions between MAP domains has no longer an impact oncongestion reduction of bottlenecks. Owing to theseremarks in a single MAP hierarchy, in our simulation a

xed 50% overlap size between MAP domains is permitted.Consequently, the focus is to evaluate the performance ofthe proposed intelligent multi-MAP registration algorithm(in network with overlapping MAP domains) in this paperand the algorithm proposed in [13], which does notconsider QoS ofows in process of MAP registration.

The capacity of each MAP is set to 3 Mbps. The owbandwidth requests are uniformly distributed within the

interval of (100

500 KBps), representing from web to videoapplications. The ows are classied into six differenttrafc class types. Then, three different bits of D, R and Tare assigned to each ow indicating their correspondingclass types. Table 3 shows the used parameters for packetdelay cost measurements.

The average rate of Poisson distributed incoming ows isset as = 10. The means of exponentially distributed owsholding time and residence time are set as = 20 min andn = 5 min, respectively.

Figs. 6a and b present the percentage of bandwidthconsumption of MAPs over a certain period of time. InFig. 6a, the ow requests enter the access network, and

become distributed across MAPs according to the non-QoSaware multi-MAP registration scheme proposed in [13].Fig.6b illustrates the distribution ofow requests across thenetwork MAPs according to the proposed algorithmillustrated in Table 2. The simulations begin at t= 0s.Fig. 6a shows that MAP 1 and MAP 2 are constantlyselected and reach the 80% utilisation threshold, at t= 25sand t= 45s, respectively. Therefore the non-optimalselection of MAPs leads to rapid increase in bandwidthutilisation of these two MAPs, and makes them points of

bandwidth aggregation in the network, whereas MAP 3 andMAP 4 stay underutilised.

It is evident in Fig. 6b that the maximum utilisation ofMAPs in the network remains at 65% of the total MAP

capacity and does not reach their maximum capacities. Thisis because of accessibility of trafc ows to more MAPresources (capacity) for ARs located in the overlappedregion of MAP domains. In addition, severe bottleneckcongestion around MAPs is mitigated, hence enhancing thenetwork performance in terms of increasing networkthroughput. Fig. 6b also illustrates that the trafc load ismore uniformly distributed among MAPs as a result of the

Table 3 System parameters

O E(S) PHA

1.0 2.0 0.5 2.0 10 40

Fig. 5 Simulation network topology

Fig. 6

aMAP bandwidth utilisation in RH-MIPv6bBandwidth utilisation, with the proposed algorithm in use

www.ietdl.org



8/11/2019 AP IPv6.pdf

10/12

proposed algorithm implementation in the network, than byimplementation of the proposed algorithm in [13] (Fig.6a).

Fig. 7 shows as the trafc demand increases in theoverlapping MAP domain environment, more number ofows are admitted to the network and network throughputincreases in turn. Therefore it is clearly evident that the

proposed algorithm performs more efciently by aconsiderable margin, than the one proposed in [13] byincreasing the mean satised bandwidth demands of ows

by maximum of 74%.In order to evaluate the impact of proposed load-balancing

algorithm in terms of users perceived performance of thenetwork, the amount of bandwidth rejection is measured

against time. Fig. 8 illustrated the total bandwidth rejectionin the network within a specic duration of time.

Fig. 8 illustrates that the total bandwidth rejected is thenetwork increases as more ows arrive to the network. Italso shows the total bandwidth rejected in the network isconsiderably higher in [13], than that of caused by theemployment of proposed algorithm. The weak performanceof RH-MIPv6 is a result of a random MAP selection;

hence, an uneven distribution of trafc between MAPs(which is evident in Fig. 6a). Additionally, with nooverlapping regions between MAP domains, the trafc loadinitiated from ARs located in an MAP domain is restrictedto ow through only that MAP. Consequently, the MAP

becomes congested and no more ows are accommodatedby that MAP, and the new ows are rejected. The reductionin average bandwidth rejection achieved by the proposed

algorithm is because of the shift of LP ows from thehighly utilised MAPs to the lightly loaded MAPs. The

proposed scheme selects alternative MAPs for LP owsrather than forcing all trafc ows through the same MAP(i.e. as proposed in [13]) to ensure a uniform loaddistribution between MAPs. Thus, employing the proposedalgorithm in the network yields 71% reduction in total

bandwidth rejection in the network.

12 Conclusions

In this paper, the effect of overlapping domain regions ofconsecutive MAPs on the trafc distribution and the

degree of load balance between MAPs is studied.Introduction of overlapping MAP domains in the samehierarchy level of HMIPv6-based network architectureenforces the need for multiple registrations of MAPs forMNs. This paper proposes an adaptive QoS awaremultiple MAP registration algorithm, which separates theselection scheme for the HP and LP ows. For each HPow, the proposed algorithm selects the most suitableMAP based on QoS requirements of the ow, whereas foreach LP ow an explicit MAP selection is employed,which provides the best balance, in terms of bandwidthutilisation among MAPs. The simulation results illustratethat implementing the proposed algorithm in the novel

network architecture, provides more available resources forHP ows, in comparisons with the multi-MAP registrationproposed in [13], in non-overlapping MAP domain accessnetworks. Accordingly, a maximum of 71% drop intotal ow bandwidth rejection is obtained. In addition, themean satised ow bandwidth demand is increased by amaximum of 74%. This improvement is because of shiftof LP ows from the heavily loaded MAPs to morelightly loaded ones. The trafc shift also has aload-balancing impact among MAPs. Consequently,congestion in the network decreases, whereas QoS of HPows are satised.

13 Acknowledgment

The authors thank Alexandre Jaron for his helpfulsuggestions.

14 References

1 Johnson, D., Perkins, C., Arkko, J.: Mobility support in IPV6, IETFRFC3775, June 2004

2 Yan, Z.-W., Zhou, H.-C., Zhang, H.-K., Zhang, S., Chao, H.-C.: Designand implementation of PMIPv6 based multi homing formake-before-break handover, J. Internet Technol., 2010, 11, (1),pp. 110

3 Lee, J.-H., Ernst, T., Deng, D.-J., Chao, H.-C.: Improved PMIPv6

handover procedure for consumer multicast traf

c, IET Commun.,2011, 5, (15), pp. 21492156

4 Han, Y.-H., Min, S.-G.: Performance analysis of hierarchical mobileIPv6: does it improve mobile IPv6 in terms of handover speed, Wirel.Pers. Commun., 2009, 48, (4), pp. 463483

Fig. 7 Mean MAP bandwidth utilisation against time

Fig. 8 Bandwidth rejection against time

www.ietdl.org



8/11/2019 AP IPv6.pdf

11/12

5 Leung, G.K.: Proxy mobile ipv6, RFC 5213, August 2008], [SolimanH., Castelluccia C., Malk K.E., Bellier L.: Hierarchical mobile IPv6mobility management (HMIPv6). IETF RFC 414, August 2005

6 Dev Pragad, A., Friderikos, V., Pangalos, P., Aghvami, H.:The impactof mobility agent based micro mobility on the capacity of wireless accessnetworks(IEEE GLOBCOM, 2007)

7 Soliman, H., Castelluccia, C., Malk, K.E., Bellier, L.: Hierarchical mobileIPv6 mobility management (HMIPv6).IETF RFC 414, August 2005

8 Pack, S., Nam, M., Kwon, T., Choi, Y.: An adaptive mobility anchorpoint selection scheme in hierarchical Mobile IPv6 networks,

Comput. Commun., 2006, 29, (16), pp. 306630789 Natalizio, E., Scicchitano, A., Marano, S.: Mobility anchor point

selection based on user mobility in HMIPv6 integrated with fasthandover mechanism. Proc. IEEE WCNC 2005, March 2005, Vol. 3

10 Wang, L., Gaabab, B., Binet, D., Kofman, D.: Novel MAP selectionscheme using location history in hierarchical MIPv6 networks (IEEEWCNC, 2008)

11 Mirsayar, A., Barkoosaraei, A., Aghvami, H.: Intelligent overlappingMAP domain forming for mobility management in HMIPv6 accessnetworks(IEEE WCNC, 2012)

12 Mirsayar, A., Barkoosaraei, A., Aghvami, H.: Dynamic partitioning ofIP-based wireless access networks. Elsevier Computer Networks, 2012.Available at http://dx.doi.org/10.1016/j.comnet.2012.09.005

13 You, T., Pack, S., Choi, Y.: Robust hierarchical mobile IPv6(RH-MIPv6) an enhancement for survivability & fault-tolerance inmobile IP systems(VTC, 2003)

14 Nichols, K., Blake, S., Baler F., Black, D.: Denition of thedifferentiated serviceseld. IETF RFC2474, December 1998

15 Allot Communications, Allot Resource Center: Digging deeper intodeep packet inspection (DPI). December, 2007. Available at www.dpacket.org/articles/digging-deeper-deep-packet-inspection-dpi

16 Kim, C.: Convergence in broadband and mobile networking:international conference. ICOIN 2005, Proc.: Google eBook, JejuIsland, Korea, January 31February 2, 2005

17 Thing, V., Lee, H., Xu, Y.: Designs and analysis of local mobilityagents discovery, selection and failure detection for mobile IPv6.

Proc. IEEE MWCN, September 200218 Jeong, C.S., Song, Y.M., Jo, S.U.: Dynamic iterative method for fast

network partitioning. Proc.: Eighth Int. Conf., HPCN Europe, 2000,pp. 8188

19 Pragad Audsin, D., Friderikos, V., Hamid Aghvami, A.: Optimalconguration of mobility agents in broadband wireless accessnetworks. IEEE GLOBCOM Workshop on BWA, 2008

20 Kleinrock, L.:Communication nets: stochastic message ow and delay(Dover Publications, 1964) ISBN: 0486611051

21 Pack, S., Nam, M., Choi, Y.: A study on optimal hierarchy inmulti-level hierarchical mobile IPv6 networks (IEEE GLOBCOM,2004)

22 Apostolopoulos, G., Gudrin, R., Kamat, S., Tripathi, S.K.: Quality ofservice based routing: a performance perspective. Conf. the ACMSpecial Interest Group on Data Communication (SIGCOMM),Vancouver, B.C., 1998

www.ietdl.org



8/11/2019 AP IPv6.pdf

12/12

C o p y r i g h t o f I E T N e t w o r k s i s t h e p r o p e r t y o f I n s t i t u t i o n o f E n g i n e e r i n g & T e c h n o l o g y a n d i t s

c o n t e n t m a y n o t b e c o p i e d o r e m a i l e d t o m u l t i p l e s i t e s o r p o s t e d t o a l i s t s e r v w i t h o u t t h e

c o p y r i g h t h o l d e r ' s e x p r e s s w r i t t e n p e r m i s s i o n . H o w e v e r , u s e r s m a y p r i n t , d o w n l o a d , o r e m a i l

a r t i c l e s f o r i n d i v i d u a l u s e .

ap ipv6.pdf

Documents