a macro mobility scheme using post handover techniques for optimization of handover and roaming

8/3/2019 A Macro Mobility Scheme using Post Handover Techniques for optimization of Handover and Roaming

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A Macro Mobility Scheme using PostHandover Techniques for optimization of

Handover and RoamingDebabala Swain, Siba Prasada Panigrahi and Prasanta Kumar Patra

AbstractEven though the PMIP provides mobility solutions, there are many issues of user identity, mobility context of users

from a home network to the visiting network, the assignment of home address to a user terminal in a visiting network,

identification of the user terminals mobility, and identification of MPA and HA. In this paper, we propose a new mechanism with

proxy mobile IPv4, as a mobility solution in networks. In this mechanism during mobile node access authentication, MPA

exchanges registration messages with the HA (Home Agent) to set up a suitable routing and tunnelling for packets from/to the

MN. In this method, the authentication request of the mobile node is passed through the NAS or AP of visiting network, this is

then passed to the AAA (Authentication Authorization and Accounting) server, and the authentication server checks the realm

and does start authentication procedure at the time of initialling authorizing module of the mobile terminal. It also initiates the

mobility extension module, where the AAA server initiates MPA of the access network, which also informs the AAA server of the

home network with information on the mobility extensions and request of the mobility parameters of the user terminal. The home

AAA server interacts with the HA and collects mobile node parameters, as well as sending back details as a reply request to the

visiting AAA server. After the mobility context transfer, the MPA conducts a mobility registration to the HA for that particularmobile node. Later in this paper, we will provide sequence of message exchanges during a mobility session of a user mobile

node during handover.

Index TermsHandover, Roaming, Mobility Management.

1 INTRODUCTION

HE mobility management in the access networks isprovidedbythemobileIPfortheseamlesscontinuityof the services during handover and roaming. The

demands for accessing services at high data rates whileon the move, anyplace and anytime, resulted in numerous research efforts to integrate heterogeneous wirelessandmobilenetworks.However,whenthehandoverhappens, the contentionbased medium access mechanismwhichismainlyusedinWLANisinvokedandintroduces unbounded transmission delay due to idle time periods and retransmissionbecause of collision during thehandover.Ifthistechniqueisexpandedtouseinamicrocellular network such as connected WLAN microcells,contentionbased mechanism, therefore, should not beusedtohandle theMTshandover,especially forvehicularuserswhochangeaccesspointeveryfewseconds[1].IP Mobility management protocols are divided into twokindsofcategory:hostbasedandnetworkbasedmobility

protocol. Issues and challenges in mobility managementidentifiedanddiscussedin[2].Recently,aunifiedIPMultimediaSubsystem (IMS)authenticationarchitecture thatextendsthescopeofIMSbyallowingittoofferusersdif

ferentIMSbasedservicesevenbeyondtheirowndomainhasbeenproposedin[3].But,alltheseresearchactivitiesresultedinvariousheterogeneousarchitectureswheretheinterworking was performed at different levels in thenetwork.Also,integrationattheUMTSradioaccesslevelforseamlesssessioncontinuityproposedin[4].But,proposed integration isatechnologyspecificsolution.However,inthisarticle,weevaluatemacromobility.

The Proxy Mobile IP (PMIP) [5] solution based onMobileIPapproach;handlesmobilitymanagementinsideaccess networks. Therefore network entities will requiremorecapability than in thestandardMobile IP.TheForeign Agent is no longer capable to handle the mobilitymanagementinthisnewscenario,soweneedtoenhanceits capabilitieswith theMobilityProxy mechanism.Thisnew entity called Mobile Proxy Agent replaces ForeignAgent in the visiting network. It also handles mobilityregistration with the Home Agent. This change is most

significant since the Mobile Node now lies outside themobility registration procedure. In fact, Mobile Node isnotawareofitsmovement,accessnetworksdeceivesthehosttobelieve that it isstationary in itsHomeNetwork.Since the Mobile Node does not need either movementdetection or agent registration, the agent advertisementsarenolongernecessary.

This paper addresses some of the requirements andfeaturestobesatisfiedforPMIPtoprovidemobilitymanagement:

Debabala Swain is with the centurion University of Technology & Man-agement, Bhubaneswar, India.

Siba Prasada Panigrahi is with the Department of EEE, GITA, Bhubanes-war, India.

Prasanta Kumar Patra is with the CSE Department, CET, BPUT, Bhuba-neswar, Orissa, India

T

JOURNAL OF COMPUTING, VOLUME 3, ISSUE 12, DECEMBER 2011, ISSN 2151-9617

https://sites.google.com/site/journalofcomputing

WW.JOURNALOFCOMPUTING.ORG 146


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SupportUnmodifiedHosts:Asnotedabove, theprotocolsupportsmobilitytonodesthatdoesnothavecapabilityofmobility.

Airlinkconsumption:Mobilityrelatedsignallingover the airlink is eliminated. Considering thatNetwork Address Translation (NAT) is ubiquitous in IPv4 networks, a mobile node needs tosend keep alive at short intervals to properlymaintain NAT states. This canbe doneby theMPA in the network which does not consumeany airlinkbandwidth. The Agent dictation isalsoeliminatedintheprotocol.

Supporting the Heterogeneous Wireless LinkNetwork:Oneaspectishowtoadopttheschemetoan access technology.Since the ProxyMobileIPv4isbasedonaheterogeneousmobilityprotocol,itcanbeusedforanytypeofaccessnetwork.

Another aspect is how to support mobilityacross different access technologies. So long asthe MPA can use the same NAI to identify theMN for various access networks, roaming betweenthemispossible.

Support the IPv4and IPv6:As IPv6 increases inpopularity,thehostwilllikelybedualstack.

2 PROPOSED SOLUTION FOR PMIP WITHINTEGRATED AAA ARCHITECTURE OF THE 3GPPAND WIRELESS NETWORKS

In this new mechanism, mobility registration of a userterminal is performedby visiting access networks and ahomeaccessnetwork.Theuserterminaldoesgeneralauthenticationbyvisitingaccessnetworkswith thehelpofan EAP (Extensive Authentication Protocol) mechanism.The visiting access networks receive the authenticationrequest from a user terminal through the NAS orAP ofthe network. The AAA server of visiting network and

homenetworks

are

modified

so

that

they

can

communi

catewith theHAandMPAof their respectivenetworks.NewmobilityextensionsaredevelopedinAAAservertosupportmobilitymanagement,whichaddsto itspresentservices.Theseextensionsprovidemobilitycontexttransfer from home access networks, registering the user terminalformobilityatthetimeofauthentication.Thevisitingnetwork initiatesauthenticationand themobilityextension method whenever it receives a request from theNAS or AP of the access network. During initiation ofmobilityextensions, theAAAmobilityextensionprocesscollects data when NAS/AP requestsauthentication.TheAAAmobilityprocesssendsmobilityuserdetailsrequest

tothehomenetworkandtheAAAserveroftheterminal,with newly specified attributes of proxy mobile IP. TheHomeAAAserverdoesreceivearequestforthemobilityuser details request as well as the authentication. ThehomeAAAserverdistinguishesaproxymobileIPpacketfromothercodesandattributesofthereceivedpacket.IfthepacketsneedtobeaproxyfromanintermediateAAAserver, then that server adds the proxy attribute to thereceivedpacketandsendsittothedestinationAAAserver. If ever the user terminalbelongs to the current network, then theAAAserversendsamobility registrationrequesttoHA.

After receiving the request for mobility user detailspacketfromthevisitingAAAserver,thehomeAAAserver investigates any information available in the packetand collects user identity from the request packet.Afterprocessing the request, the mobility extension methodprepares user detail request packet to the HA of theaccess network. This packet contains details of user idand parameters. The HA receives a request, and with auser ID of request it extract the information of its SID,

keys, home address and home agent address from thedatabase of the HA. The HA then sendsback a reply totheAAAofhomenetworkwiththeabovementioneddata. The AAA server receives a reply and processes theinformation,andsendsbackareplymessagetothevisitingAAAserver.ThevisitingAAAserverreceivesareplyfromhomeserverandprocessesit,storingthedataoftheuser ina temporarydatabase.Afterprocessing thereplymessage, the AAA server sends a mobility registrationrequesttotheMPAassociatedwiththatparticularNASorAP. This request contains the details about user ID, SPI,keys, home address and home agent address. When theMPAreceivesthepacketitstartsthemobilityregistration

ofauser

with

details

from

the

AAA

server.

MPAinitiatesamobilityregistrationrequestofauserterminalwithHAusingdetailsprovidedbyvisitingAAAserver.Registration involves theuserSPIand thesharedkey mechanisms with the key available from the AAAserver to the MPA. After successful registration of theuserwiththeHA,theMPAwillmodifytheDHCPserverconfigurationwiththeuserterminalsdetails.Thesemodifications contain details of MAC address and home addressoftheuserintheDHCPserver.Aftersuccessfulauthentication of the user terminal it initiates a DHCP request foran IPaddress.TheAP/NASof thevisitingnetworkforwards therequest totheDHCPserver.With the

MAC

address

of

the

user

terminal

modified,

the

DHCP

serversendsareplytousersterminalwith itshomeaddress.TheuserterminalreceivesthereplyandconfigurestheIPaddresstothehomeaddress.Necessarymodificationhastobedonebythevisitingnetworktoaccommodate the terminal with theARP, etc. When the user terminalisinithomedomain,theHAregisterstheterminalandsendsthemodifiedDHCPrequesttotheDHCPserverandacknowledgesthehomeAAAserverofsuccessfulregistrationofauserterminal.TheProxyMobileIPwiththeAAAservermobilityarchitecture isshown inFigure1.

Fig.1. Proxy Mobile IP Architecture.





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2.1 AAA mobility extensions for PMIP integratedarchitecture

In this section we describe the detailed architecture ofAAAwithmobility extensions toprovide mobilitymanagement during user mobility in different access net

worksand

technology.

In

this

process,

the

existing

AAA

architectureismodifiedtoaccommodateproxymobileIP.In general, authentication information of users is passedthrough the authenticator, and then this information ispassedthroughtheNASorAPoftheaccessnetworks.AnAAAserverauthenticatestheaccessnetworksfortheAPorNAS initially,and thenprocesses theuserauthentication request depending on the realm of the user. In thisnew method, the mobility management of a user canbeinitiated during the authentication process. In thisprocess, due to parallel operation of authentication andmobilitymanagement,theoveralllatencyofauserduringthehandoverandinitialaccesscanbereduced.

When there is an authentication request for a userterminalfromanNASorAP,theAAAserverinitiateauthenticationmoduleandmobilitymodules,andprocessesthe users detailsby identifying the NAIof the user terminalrequest.FromtheNASorAPrequest information,such as MAC address of user terminal, NAS details areprocessed for further procedures. TheAAA is modified,with new attributes and codesbeing added for supporting the PMIP modules. As mentioned previously in theproposedsolutionsectionwithnewextensions,theAAAof the home network can communicate with a visitingnetwork,andcanprovidemobilitycontextmanagement.With these mobility extensions, the AAA server cancommunicate with the MPA and HA of the access net

works.On theotherside, thevisitingAAAservercommuni

cateswiththehomenetworkAAAserver,afterreceivingan authentication request using the mobility extensions,withuser informationbeingavailable from theauthenticationrequestfromtheusersterminal.ThevisitingserversendsamobilityuserdetailsrequestusingIDandNAIof the authentication request to the home AAA server.When the home network receives a request packet, theAAA server processes the information of the user fromrequest. It then sendsa request to theHAwith thenewmobility extension, requesting details of the user. Afterreceiving the request packet and processing user details

from its internal database, the HA sends back a replypacketwithhomeaddress,key,SPIandhomeagentaddress to the home AAA server. The home AAA serversendsback a reply to the visitingAAA server with userdetails as the reply. After receiving this reply from thehomeAAAserver, thevisitingAAAserverprocessestheinformationof theuserandsendsa request formobilityregistrationrequestwithnewattributestotheMPA.TheMPAreceivestheuserterminaldata,sentby thevisitingAAAserver,andtemporarilystoresitinalocaldatabase.TheMPA,withavailableuserinformation,startsregistering with the HA. After registration request and replymessageexchangewithHA,theMPAsendsreplyofsuccessorthefailureofmobilityregistrationofusertovisitingAAAserver.Figure2describestheAAAmobilityarchitecture.

2.2 PMIP operation with new mobility extensions inMPA and HA

MPAexchangesregistrationmessageswiththeHAtosetupaproperroutingandtunnellingpacketsfrom/toMN.

The MNbroadcasts messages containing an MNs Network Access Identifier (NAI) to request authentication/authorization,andtheAPtransferstherequesttothelocal AAA server (visiting AAA). If the MN is awayhome,itisclearthattheMNisoutofthelocalauthenticationdatabase.However,thelocalAAAservercanusetheNAI to identify the MNs Home Network, and then theauthentication/authorization, along with mobility userdetails, will request a message tobe transferredby thevisiting AAA to the home AAA Server (AAAH) in theHomeNetwork.

Along with the authenticating validation, theAAAHsearchesforinformationoftheMNstoredintheHA,con

tainingMNs

HA,

NAI,

and

SPI.

If

the

MN

is

back

to

its

HomeNetwork, then the localAAAserversendsamessagetotheHAtoderegistertheMNinsteadofsearchingforthedata.TheMNs informationwillbetransferredtothe visitingAAA, which will deliver it to the MPA withtheAPs MAC address included. Triggeredby the AAAserver, theMPAexchangesmessageswith theHA todemandMobilityRegistrationandTunnelling.

Aftersuccessfulregistration,theMPAsendsamessagetoinformtheDHCPserverabouttheMNsarrival.Itforces the DHCP server to update the configuration filewith the Mobile Node information. Finally, the MPA informstheAAAvisitingabout thesuccessfulregistration.The Authentication Accept message is sent to the NAS,grantingnetworkaccess to theMN.Afterauthenticationsuccess, the MN sends a Binding DHCPDISCOVER torequest the IPaddress.Thismessage is formattedasdescribedbytheDHCPprotocol(theCIADDRfieldisfilledwith the MNs IP). By searching for information of theMobileNode,intheconfiguration,theDHCPserverreplieswithaDHCPOFFERmessage inwhich theYIADDRfield is filled with the MNs HomeAddress and the default gateway address,being the MPAs. Next, the MNand DHCP server exchange the DHCPREQUEST andDHCPREPLYtocompletethisprocedure.TheMNisthenreadytoconnecttothenetworkwithitsHomeAddress.

Fig.2. AAA architecture with new mobility extensions and PMIP.





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3.MACRO MOBILITY

In thisscenariotheusermobiledoesmove fromoneadministrative domain to different administrative domains(one operator to another operator) and from technology

to another technology (WLANWIMAX3GWLAN).

3.1. PMIP operation with new mobility extensionsin MPA and HA

In thisscenariomobilenodemaintainsmultiplenetworkinterfacesforconnectingtoaccessnetworks.TheselectionofbestsuitednetworkisperformedaccordingtotheSLA,desiredQoSandotherfactorswhichisoutofthischaptercontext. In this process mobile node initiates access network initially and establishes a session with the accessnetwork.During initialauthenticationprocedures,accessnetworksalsocreatemobilitycontextofuserandregisters

userin

HA

of

access

network.

When

user

terminal

detects

availability of access networks on other interface it initiatesnewinterfaceandstartsperformingauthentication.After listening to the NAS request for authentication ofuser,visitingaccessAAAservercollectsuserdetailsfromNASrequestsandsendsauthenticationandmobilityuserdetailsrequestinparallel.HomeAAAserverafterlistening to mobility user details request does reply with requireddetailsofuserwithSPI,HAdetailsandhomeaddressof theuser tovisitingAAAserverasareply.Aftercollectingdetails,visitingAAAsendsregistrationrequesttoMPAofnetworkwhereNASorAPresided.TheMPAstartstheregistrationofuserterminalwithHAandcaches route in DB of MPA. Once the tunnel is establishedbetweenHAandMPA,HAupdatesnewroutefortoandfrocommunicationwithuserterminal.Figure3providesdetailmessagesequenceinvolvedduringtheprocedure.3.2. User terminal roaming from one operator net-work to another

Inthisprocedureuserterminalconnectstoanaccessnetwork and performs authentication to the access network.AccessnetworkdoesregisterterminaltoaHAandprovides the IP address to theuser terminal. Whenuserterminaldoes identifydifferentoperatornetwork it triestoconnectthatnetworkbyinitiatingtheauthenticationorreauthentication procedures. When NAS or AP receives

the request for authentication, it forwards the details toAAA server. Visiting AAA server does initiate mobilityuser details request to home network AAA server byidentifying the NAI of the user ID for authentication.Upon receiving request home AAA server collects dataassociated touser ID from requestandreplymessage toHAandsendsbackreplytovisitingAAAserver.VisitingAAAserversendsmobilityregistrationrequesttoMPAofnetwork associated to the NAS orAP with collected detailsfromhomeAAAserver.MPAdoesregistrationwithHA using details fromAAA server, and sends acknowledgement to AAA server. After authenticating user terminal and upon receiving the reply from MPA, visitingAAAserversendsuccesswiththeIPaddressoftheuserterminal sentby the home AAA server to NAS/AP. ThemessageexchangeisshowninFigure4.

4 NEW PMIP AND AAA MOBILITY EXTENSIONDEVELOPMENT AND TEST-BED SETUP

4.1.PMIP and AAA software architectureTo implementproposedarchitecturewedevelopedAAAserver and PMIP in house using existing open sourcesoftware. We have developed software architecture toimplement mobility extensions for AAA server. In thisarchitectureAAAservercanreceivearequest fromNASor from another AAA server. From NAS it can receiveauthenticationrequestandfromAAAserveritcanreceivemobilityuserdetailrequest.Uponreceivingmobilityregistration request, extensions model respond with the reply of user details. Software architecture of AAA asshowninFigure5,theAAAservercansendrequestsandreplyaccordinglytoincomingrequestswiththedifferent

components.

For

implementing

the

PMIP

we

used

dy

namics mobile IP architecture and modified to our requirements. We converted FA to an MPA, modified HAand MPA to accept any requests from AAA server andsending reply accordingly. In this architecture MPA canperform registration requests to HA upon request fromAAA server and sends acknowledgement as success orfailure.NewpacketformatsandcodesareaddedinMPAandHAtoimplementtheproposedarchitecture.4.2. AAA Mobility extension and PMIP packet for-matsWe have developed new AAA mobility extensions andnew codes and packet formats for developing and de

monstrating

the

capabilities

of

new

mechanisms

pro

posedinthisarchitecture.TheAAAserverbuildsMobility User Detail Request message fromAccess Request orEAPRequestfrom theNASorAP.Remarkthat intermediate AAA servers just pass through this step, addingProxyAttributeandforwardingtheRequest.AAAMobilityUserdetailRequestformat:Note: the codes and the attributes in this document aretakenasreferencethesecanbechangedaccordingtotheIANAconsideration;inthiscaseweusedavailablevaluesfordevelopingtheprototype,wecanchangethesevaluesifthereareanyissues.

Fig.3. Message exchange between components of architectureduring multi technology scenario.





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Code:(1byte)Mobility_User_Detail_Request=60.

Identifier: (1 byte) number to match the Re

quest/Reply.

Length: (2bytes) length of the message, including

Code,Identifier,Length,Authenticator,Attributes.Inthe

casethatthereisonlymobilityattribute,length=350

Authenticator: The Authenticator field is 16bytes.

Themostsignificantoctet is transmitted first.Thisvalue

isusedtoauthenticatethereplyfromtheRADIUSserver,

andisusedinthepasswordhidingalgorithm.

Attributes: Mobility Attribute:

Type=(1byte)Mobility_Request_Attribute=193.

Length(2bytes)=Lengthofthemessage=332.

UsersID:(256bytes)extractedfromthenameofthe

user(ex:userID@realm).

HA address: (4 bytes) Home Agents IP address,

filledwithZeros.

HomeAddress: (4bytes)MobileNodesHomeAd

dress,filledwithZeros.

SPI:1byte,filledwithZeros.

Key: (64bytes) public key of the HA, filled with

Zeros.

TheAAAHwillreplywithaMobilityResponse.

HA/MPAconsultationIfAAA home server receives Mobility user detail re





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questfromavisitingserver,theAAAHsendsmessageto

HA to fill the information required in the Mobility Re

questAttribute(fieldsthatarefilledwithZeros).Remark

thattheAAAHsendstheHAConsultationmessageonly

bybeing triggeredby the Mobility user detail Request;

the Access Request forces the AAAH to deregister the

MN.

H1:CreateamessagefromAAAHtotheHAdemanding

forthenecessaryinformation:

Code(1byte)=HA_Consultation_Request=63.

Identifier: (1 byte) number to match Re

quest/Response.

Length(2bytes)=totallengthofthemessage=343

APandMNsMACaddress:Thesefieldsarepracti

callyusedinthemessagefromAAAtoMPA.Inthemes

sagefromAAAtoHA,thesefieldsarefilledwithZeros,

andtheHAjust ignoresit.ButthesefieldsSHOULDap

pear intheHAConsultationMessageto identifythefor

matofmessagesAAAHAandAAAMPA.Itisveryuse

fulsincetheHAandMPAinthesamenetworkareusual

ly installed inthesameserver.This identificationsimpli

fiesthetreatmentofmessageintheHA/MPAserver.

Other fields are copied from the MobilityAttribute

oftheauthenticationrequest.

H2: HA looks for the required information in its

database,savetheAPandMACaddressfields.Ifthe in

formationcantbefound(thismaybeduetothemodifi

cation of the administrator), HA will pass this phase, so

thatthemessagewillbeleftZeros.ThatallowstheAAAH

todetectthefailure.

H3:HAsendsbackthereplytotheAAAafterfilling

the requests required fields and setting Code =

HA_Consultation_Response=64.

H4: The AAAH replies the visiting AAA with a

MobilityuserdetailResponse,which iseitheranAccept

or Reject message. The format of these messages is as

sameastherequest,withdifferentcodeandattributes:

IfthemessagefromHAisnotfilledwithZeros(suc

cessful verification), theAAAH reply to theAAAF with





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MobilityAcceptmessagewhichiscopiedfromtheMobil

ity Request whose the Attributes filledby the data re

trievedfromHA.TheCodefieldforthismessageis:Code

=Mobility_Accept=61.

If the data from HA is filled with Zeros, the AAAH

MUSTreplythevisitingAAAwithaMobilityuserdetail

Reject message, with Code = Mobility user Reject = 62.

The Mobility Reject message doesnt contain the Mobili

ty_Attribute, and may include ReplyMassage Attribute

whichcontainstheerrormessageshowntotheuser[6]:

Type:18forReplyMessage.

Length: lengthof theattribute, includingTypeand

Lengthfield.

Text: The Text field is one or more octets, and its

contentsare implementationdependent.It is intendedto

be human readable, and MUST NOT affect operation of

the protocol. If the registration failed, this field is filled

withthemessageextractedfromtheMPAMobilityRegis

trationReply.

MobilityRegistration

AfterreceivingtheMobilityAcceptmessage,thevisit

ing AAA makes MPA handle the Mobility Registration

procedure. The MPA exchanges messages with HA and

DHCPserver,theninformsvisitingAAAabouttheresult

(successorfailure).TheMobilityregistrationRejectcaus

estheAAAFtosendtheRejectmessagetotheNASand

terminatethewholeprocedure.

MR1:VisitingAAAsendsaMPAMobilityRegistra

tion Request message to MPA: the format is as same as

HAConsultationmessage:





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Type (1 byte) =

MPA_Mobility_Registration_Request=65.

Identifier: (1 byte) number to match Re

quest/Response.

Length(2bytes)=totallengthofthemessage=343.

Other fields save AP and MNs MAC address are

copied from the Mobility Attributes of the Registration

Response.

MR6:MPAMobilityRegistrationReplytovisiting

AAA:

TheMPAsendsbackthereplytotheAAAaftersuc

cessfulcommunicationwiththeDHCPserver,orifitde

tects any error (registration unsuccessful, DHCP server

refusal to register the Mobile Node, or requests cannot

reachthedestination).InthislattertheMPAsendsareject

messagetotheAAAserver(replywithresponse=1or2).

Type=MPA_Mobility_Registration_Reply=66

Response = 0 ifsuccessful, =1 if unsuccessfulwith

message,=2ifunsuccessfulwithoutmessage.

In the unsuccessful case (Response != 0),AAA will

sendsanAccess_RejectmessagetotheNAS.Otherwise,if

theResponseCode=1, the text in theMessage fieldcan

be

used

in

the

Reply

Message

Attribute

in

the

Mobility

RegistrationRejectmessage.

MR2:Registration

FortheconvenienceofuseofClientMobile(MobileIPv4)

and Proxy Mobile IP simultaneously, the MPA and HA

shouldusetheMobilityRegistrationRequestasspecified

asinRFC3344.

HAreplywithMobilityRegistrationReply, format

ted

as

specified

in

RFC3344.

MR4: MPA sends DHCP Mobility Registration Re

questtoDHCPserver:





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Type=DHCP_Mobility_Registration=67

Identifier:matchRequest/Response

Length = 21: length of the message, including the

TypeandIdentifierfields

MACaddress:MNsMACaddress

HomeAddress=MNsHomeAddress.

Action: (1byte) = 0 binding update: the DHCP

server updates its configuration file with the MNs new

entry:

MNsMACaddress MNsIPaddress DefaultGate

way=MPAsMACaddress

IfAction=1 removeentry:causetheDHCPserver

to remove the MNs entry in its configuration file. This

action is used in the Registration Revocation Procedure.

AsreceivingthemessagefromtheMPA,theDHCPserv

er updates its configuration with the information sup

pliedbytheMPA.Sincethen,assoonastheDHCPserver

receives the (Binding) DHCPDSICOVER message from

the MN, it will exchange the messages with the MN

granting the MN keep its HomeAddress; also indicates

theMPAasMNsdefaultgateway.

MR5:DHCPMobilityRegistrationReplytoMPA

Themessage is formattedassameas thereply from

MPAtoAAA

Type=DHCP_Mobility_Registration_Reply=68

Length= lengthof themessage including theType

andIdentifierfields

Response Code = 0: accept, = 1 reject with message, = 2

rejectwithoutmessage.

If theresponseCode isother than0, theMPAMUSTre

sponse with the AAA with MPA Mobility Registration

Reply whose Response and Message fields copied from

DHCPMobilityRegistrationReplymessage.

Message:thismessagewillbeused intheresponsefrom

MPAtoAAA.

Fig. 4: Message exchange between components of architectureduring roaming scenario.





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4.3. Test bed SetupThis section describes testbed setup for implementingsolutions proposed in this architecture. As mentionedearlier we have developed mobility extensions for AAAserverusingFreeradius[7],andPMIPusingpartsofDynamics mobile IP [8]withour implementation.The proposed testbed composed of 3GPP, WLAN and WIMAXNetworks.Weused Infinets preWIMAX equipment,operatingatthefrequencyof5.4GHZforWIMAXnetwork,WLANaccessconsistsofLinksysWRT54andCiscoAironetAP350.The3GPPnetworkusedinthiscaseisEDGEnetwork operated by the French network operatorBouygesTelecomcourtesyofMVNOTransatel.Theuserterminal used in the testbed is DELL Latitude410 usingCentrinoforwirelesswithoptionGT7.2readyMAXdatacard for 3GPP access. Most of our testing for differentscenariowehaveusedWIMAXandWLANduetocom

plexity of EDGE network as we have limited control oftheproductionnetworkprovidedbyMVNOTransatelforus.Tovalidatethesolutionweusedbasictestinglikeverticalhandoverwheretheclientisequippedwithmultipleinterfacestovalidatethesolutionformultihomingscenarios. As we mentioned earlier horizontal handover is limitedforEDGE inourcasebecauseofthecontroloftheaccessnetwork.

The implemented scenario is shown in Figure 6. Wehave deployed a VPN with cellular network where authentication and data is routed through the cellular network to local testbed. The user terminal is configuredwithATcommandsusing PAP forauthentication.Whenuser terminal dials for connection, authentication information of user terminal is routed through GGSN to thelocal authentication in the testbed, the modified AAAserver does the authentication and assigns the addressusingIPpoolmechanism,andinparallelmobilitycontextiscreatedforMPAandHAusingAAAserver.

WehavedeployedEAPauthenticationmechanismforauthentication in WLAN and WIMAX networks. A userterminal tries to connect access networks using WPAsupplicant[9],itisconfiguredwithuseridwithNAIandsecuritymechanismsessential forEAPTLSmechanisms.Once the authentication is initiated in access networks,APsandBSsendsauthenticationrequesttoAAAservers,andAAAinitiatesauthenticationandmobilitycontextforuser terminal.A GUI is developed on terminal to maintain interfacesandcontrolaccessmanagementalongdif

ferentaccessnetworks.

5 RESULTS

As mentioned in architecture the AAA server does authentication and mobility in parallel when there is a request from theuser terminal in testbed.Using this testbedwehave achievedmobilityofuserwith low latencyand seamless mobility in some scenarios.Multi homing,horizontalhandoverandroamingisperformedefficientlyusingthismechanism.Variousscenariosofmobilityhavebeen testedusing this testbed.Deploymentandextendingtothenewaccessnetworksandoperator isveryeffi

cientas

the

modifications

are

made

at

network

side

with

out any client conscious. The modifications on the networksidecanbemadewithadditionalpatcheswithexisting deployments. For testing purposes we have usedexperimentalcodesandattributevaluepairsthesecanbeextendedtothevendorspecificorusingIANAstatuscanbestandardized.Wehaveobservedanoveralllatencyoftheuserterminalinvolvedduringroamingfromonenetworktoanotheronthe same technology is around 2.4 sec for WLAN, 3.6seconds for WIMAX, and 16 seconds for 3G networks,duetoreauthenticationandmobilitymanagement.In3Gnetworkswehaveobservedhigh latencyduetodelayofrouting messages frombouyges telecom network to ourtestbed.Formultihomingscenarioweobserved latencyof 18 milliseconds as we have implemented multiple interfacescenarios,whereauserterminalconnectstomultiple networks and the management of the mobility isperformedby triggering routeupdatemessage inHAoftheuserterminal.Inthenextparagraphwehaveattachedalogofourradiusserversinhomeandvisitingnetworkswhere thewholeprocedure isdepicted.Formoredetailsaboutlogs,etherealresultsreferto[10].5.1. Comparison with existing mobility modelsIn thissectiondifferentmobilityprotocolsarecomparedwiththeavailableresultsandsupportforaccessnetworks

Fig. 5: AAA server software architecture with new mobility exten-sion module.

Fig. 6: Test-bed setup using WLAN, WIMAX and 3G networks





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with experimental results and simulation results.As wementioned in last section we havebuilt testbed to performmobility indifferent interworkingscenariosofmobilityusingmobilityprotocols.WetakethefollowingresultofCMIP,HMIPandPMIPfromthetestbedand theresultofHAWAIIandCellularIPfromothersources[11].The Table 1 shows the different performance results formobilityprotocols.

InthetestforCMIPandHMIP,wetaketheresultfrommobility registration procedure only. Macromobilityhandoff time iscounted frommoment thatMNstarts totheendof thehandoff;andmicromobilityhandoff timeiscountedfromthemomentthatweswitchnetworkconnection (changing access point). In fact, using manualswitch is little different from real time test in which theMNstartshandoffifitmovesoutofthefirstaccesspointscover,sinceinthelatercaseshandofftimedependslargelyonnetworkscanningandselectingsoftwareusedintheMN.WecanobservethattheCMIPhasveryhighmacromobility latency, which dues to Agent Discovery phase.Weadmitthatthetestbedissosimpleascomparedtothe

architecture implemented HAWAII and Cellular IP thatthedifferentnetworksareadjacent,andthereforecannothave a proper comparison among these protocols. Thetest ispurelyon latency issue,wedontcountonpacketloss and robustness. However, the result is persuadingenoughtoprovetheadvantageofPMIP.

Proxy Mobile IP isadvantageous over other mobilityprotocols over security, since the information is exchanged among the network entities with authenticatedmechanism.Moreprecisely, the advantageofPMIP overother protocolscomes from the fact that the informationexchangedinregistrationprocedurecanbegeneratedforeachsession, i.e.,HAcangeneratenecessary information

usedfor

each

registration

session.

Hence, outside AAA authentication, no key is actuallystoredformobilityregistration.The proposed mechanism for mobility management inthispaperiscompatibleandinteroperablewiththeexisting converging networks. We have studied different interworkingmethods to implementoursolution for completing the seamless converging puzzle at the mobilitymanagement layer. We interrogated different interworkingmechanismssuchasSeamlessConvergedCommunications Across Networks (SCCAN), Unlicensed MobileAccess (UMA), Interworking Wireless LAN (IWLAN),Media Independent Handover (MIH) IEEE 802.21. The

proposed

solution

can

be

adapted

in

these

mechanisms

to

provideseamlessservicesatthemobilitylayer.5.2. Issues of IPv6 migrationsDuetolowIPaddressspaceavailableforeverincreasingterminalsthereisaneedofIPv6inthenearfuturetodeliver the services. NETLMM is an IETF working groupworking in PMIPv6 [12, 13], Specification of PMIPv6 isstill in the infancy stage, there are several issues whichhastobeaddressedtoobtainthemobilitysolution.IssuesofMobileIPv6andPMIPv6interactions,AAAsupportforPMIP, MPA discovery in the access networks, handoverand route optimizations, Path Management and FailureDetection,Interaccesshandoversupportandmultihom

ing scenario handover are still open in the WG. UsingAAA mobility extensions and PMIPv6 supporting AAAextensions as proposed in the architecture, issues mentioned above are solved.As part of our future work wearedevelopingdualstackPMIPv4andPMIPv6formobilitysupportinheterogeneousnetworks.

6 CONCLUSIONPosthandover techniquesare intendedtoreduce latencyduring roaming and handover in heterogeneous networks. As a part of this we have proposed security authentication and mobility management to optimize handover and roaming. Extending existing infrastructuresuchasAAAinthiscaseismoreefficientthanproposingnewprotocolsand infrastructure.Asapartof itsecurityandmobilityextensionsareproposed.Usingthesecuritymechanisms we estimated the latency obtained in thismethodisfarlessthananyconventionalmethodsavailable in the literature. The authentication keying materialcreateddynamically,by thiswaythetheftpresentational

andsecurityvulnerabilitiesarereduced.ThemechanismspresentedareapplicabletoWLAN,WIMAXandcellularnetworksandutilizingwithRIIarchitecture thesolutionprovides the flexibility to operate in any interworkingscenariosofroamingandhandover.

ProxyMobileIPisadevelopmentofMobileIP,wherethe registration is processed by the network entities.Hence, the Mobile Node does not require a Mobile IPstack to roamover thenetworkwithout losing its IPaddress,sothiscanbeappliedtounchangeddevices.Usingthis proposed mechanism, authentication and mobilitymanagement of users during the access is performed inparallel; in this way, latency during the authentication

andre

authentication

is

reduced.

In

this

mechanism,

us

ingcontextmanagementthecontrolofuserscanbemaintained according to the access networks. Fast and seamlesshandoverisachievedinvariousdeploymentandmobility scenarios using these mechanisms. Extending andupgradingexistingnetworkscanbeperformedefficiently,asnonewhardwareisaddedtotheexistingarchitectures.Multi homing scenarios, different interworking architecturesofWLAN,WIMAXand3Gareaddressedusingtheproposedmechanisms.

REFERENCES

[1] ThanhHoaPhan,GauteLambertsen,TakahikoYamada,Seam

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[2] IbrahimAlSurmi,MohamedOthman,BorhanuddinMohdAli,

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295315.

[3] SalekulIslam,JeanCharlesGrgoire,Multidomainauthentica

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[6] Adoba.B, IANAConsiderationsforRADIUS, IETFRFC2869,

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[Online].

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[Online].http://193.54.225.196/pmip

[11] Vollero.LandCacace.F, Managingmobilityandadaptationin

upcoming802.21enableddevices, in4thinternationalworkshop

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Debabala Swain, B. E. and M.Tech from Berhampur University andpresently a research scholar in Utkal University while working withCenturion University of Technology & Management..

Siba Prasada Panigrahi, B.Tech-1995, M.E-2002 and Ph.D-2009.Presntly, Dr. panigrahi working with GITA, Bhubaneswar as profes-sor..

Prasanta Kumar Patra, presently working with CET, BPUT as Pro-fessor & Head of Computer Science & Engineering.

Table 1. Comparisons of mobility protocols with PMIPProtocols Support

for Macro

mobility

Handover

latency Ma-

cro mobility

Access Net-

works Support

Securi-

ty

CMIP ++ 700ms* WLAN/ WI-MAX

+

HMIP - No WLAN/ WI-

MAX

-

HAWAII - No WLAN/ WI-

MAX

-

Cellular

IP

- No WLAN/ WI-

MAX/ Cellular

Mobile Net-

work

+

PMIP ++ 133ms* WLAN/WIMA

X/ Cellular

Mobile Net-

work

++




a macro mobility scheme using post handover techniques for optimization of handover and roaming

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