An Efficient Handover Mechanism Using the General Switch Management Protocol on a Multi-Protocol Label Switching Network

Transcription

1 An Efficient andove Mechanism Using the Geneal Switch Management Potocol on a Multi-Potocol abel Switching Netwok Seong Gon hoi, yun Joo Kang, and Jun Kyun hoi Using the geneal switch management potocol on a multi-potocol label switching netwok, we pesent an efficient method fo handling handoves. The poposed method diectly changes an established path into a new path fo suppoting a handove. Ou investigation eveals the effects of the poposed scheme and demonstates that this method significantly educes signaling costs and delays. Keywods: andove,, MPS. Manuscipt eceived June 9, ; evised June,. Seong Gon hoi (phone: , sgchoi@icu.ac.k) and Jun Kyun hoi ( ) ae with Boadband Netwok aboatoy, School of Engineeing, IU, Daejeon, Koea. yun Joo Kang ( hjkang@eti.e.k) is with Netwok Technology aboatoy, ETI, Daejeon, Koea. I. Intoduction Due to the inceased populaity of potable computes and wieless communications devices, mobile netwoking applications have become moe and moe popula. In the mobile envionment, the demand to povide wieless Intenet access is gowing apidly. Since mobile uses change thei locations, seveal equiements, such as lossless data tansmission, simple signaling, shot latency time, efficient handove handling, and clea location management, must be fulfilled to achieve efficient mobility. To meet these challenges, the Intenet Engineeing Task Foce (IETF) has ceated a woking goup to study the mobile IP [], and specifically, eseaches have poposed seveal multi-potocol label switching (MPS)-based mobility schemes to suppot mobility on IP netwoks. In addition, thee is a geneal switch management potocol (), which can contol MPS-based IP switches. The IETF has cuently standadized mobile IP [], and seveal ideas including mico-mobility schemes have been poposed []-[6]. Although many of those poposals ty to povide global mobility, seamless handove, fast handove, and eduction of signaling taffic, they still lack sufficient mobility suppot, especially in handove latency time. ecently, vaious eseaches have poposed MPS-based mobility schemes [7]-[]. Othe studies have aimed at impoving netwok eliability [], []. oweve, these schemes have not poved sufficient fo use in the mobile envionment because a new MPS path must be established wheneve a mobile host (M) changes its location, o multi- ETI Jounal, Volume 5, Numbe 5, Octobe Seong Gon hoi et al. 69

2 MPS paths need to be eseved fo handoves. The fome condition can cause a long latency time, and the latte can esult in a waste of esouces. plays the ole of connection management fo the geneal switching system []. is a maste/slave potocol, whee an MPS-based oute can be the slave, and it allows the maste (o contolle) to establish and elease connections and to manage a pot. In addition, the potocol allows the slave to infom the contolle if something inteesting, such as a link attachment, happens on the slave. In this way, if a handove occus, the slave (an MPSbased oute) can infom the contolle of an attachment o detachment of an M. Thus, if the is used fo mobility suppot, the mobility can be efficiently handled, and the handove latency time can be educed. In this pape, we popose a method to educe handove latency time by using the on an MPS netwok. The geneal method of ou poposal is that if an M moves fom one cell to anothe, the contolle eceives event messages coesponding to the attachment message fom the new slave and the detachment message fom the old slave. The contolle then diectly changes the MPS path at the cossove label switched oute (S) by using the outing table in the contolle. This esults in the advantage of a low handove latency time. This pape is oganized as follows. Section II descibes elated wok. In section III, we intoduce a -based mobility management pocedue on the MPS netwok fo suppoting mobility. Pefomance analysis and its esults ae pesented in section IV. Section V consists of the conclusion and poposed futhe study. II. elated Wok In this section, we look into seveal existing elated studies. These consist of oveviews of the basic Mobile IP achitectues followed by thei extensions. In addition, we also simply intoduce the.. Mobile IP Mobile IP [] is a well known appoach fo mobility suppot in IP netwoks and an accepted standad in the IETF community. The objective of mobile IP is to suppot mobility in a pue netwok laye. Especially, it aims at maintaining connections even when handoves cause IP addess changes. The fundamental assumption in mobile IP is that an M has an IP home addess and gets a tempoay cae-of-addess (oa) in a foeign netwok. A coespondent node (N) addesses the M via its IP home addess. Mobile IP has two instances, a home agent (A) and a foeign agent (FA). outing is pefomed by addess tanslation and tunneling. When the N ties to send packets to the mobile host, it sends them to its A fist. In tun, the A intecepts and tunnels the packets to the oa of the M. To tunnel a packet, the packets ae encapsulated by the A. The FA decapsulates the packets and fowads them via local mechanisms to the mobile host. Fo the evese diection fom the M to the N, the M is allowed to send packets diectly. This is efeed to as tiangula outing. The mobile IP standad [] specifies a geneal handove potocol fo the Intenet. It equies that the home netwok of the M be notified of evey change of location. These location updates incu a latency in taveling to distant home netwoks and communicating hosts. They also add taffic to the wide aea potion of the intenetwok. As cuently defined, theefoe, mobile IP does not extend well to lage numbes of potable devices moving fequently between small cells.. Mico-Mobility Existing poposals fo mico-mobility can be boadly classified into two types: tunnel-based and outing-based schemes, and they ae summaized well in []. Tunnel-based mico-mobility schemes include mobile IP egional egistation. It uses the idea of a gateway foeign agent (GFA). The M egistes the GFA as the FA. In this way, mobility within the subnet of the GFA does not equie a eegistation with the emote A and is achieved by a local egistation with the GFA, thus esulting in deceased signaling ovehead and latency. A fowading enty fo the mobile host is necessay at the GFA(s), and the est of the nodes in the netwok ae oblivious to the mobility management. AWAII [5] and cellula IP (IP) [6], which ae outingbased schemes, maintain egula IP fowading pocesses to povide obustness within a domain and also eliminate the tunnel ovehead. A domain has one oot node poviding the outable addess and acting as an FA fo all Ms in its scope. In this case, changing outing table enties in all coesponding nodes can suppot the mobility between two access outes. The limitation of these schemes is that a lage numbe of nodes in the domain need to maintain fowading enties fo all Ms. This means that all nodes need to maintain a flat addess lookup table that contains enties fo all Ms in the domain, so evey node in the domain has to implement the potocol, peventing gadual deployment.. MPS-Based Schemes Seveal studies have pesented MPS-based mobility schemes [7]-[]. In one fom o anothe, MPS-based 7 Seong Gon hoi et al. ETI Jounal, Volume 5, Numbe 5, Octobe

3 AP A S B S D S F S I M N S A S E S J S S FA AP Fig.. MPS-based mobile netwok. schemes use the idea of a label switched path (SP). Guo et al. [7] pesented an IP tanspot scheme fo thid geneation adio access netwoks based on an MPS. Its basic idea was to establish and manage SP(s) fo inteconnecting APs and adio netwok contolles. This poposal also explained tanspot beas to suppot bandwidth povisioning and a vaiety of quality of sevice (QoS) equiements in the adio access netwok well. oweve, thei study failed to explain mobility, such as handoves. The integation scheme of mobile IP and MPS [8] uses a typical mobile IP concept fo mobility. As Fig. shows, if an M changes its S by a handove, then the FA (S J) and the A (S I) of the M must give and take the egistation equest and egistation eply messages as shown in Fig.. The A will then send a label equest using the label distibution potocol (DP) to the FA with a oa as a fowading equivalent class (FE). The FA eplies with an DP label mapping message to the A. When this label mapping message aives at the A, the SP is established. Afte that, the A updates its label table and sends a egistation eply message to the FA along the SP fom the A to the FA. onsequently, the egistation pocess by handove may equie a long latency time at the egistation pocess by a handove. If the A is in a diffeent netwok, which is connected to the FA with moe hops, it takes a longe handove latency time. Kim et al. poposed a mobility-awae MPS scheme [9] to impove the deficiencies in the mobile IP. This poposal povided an efficient mico-mobility with continuous QoS suppot by combining the advantages of the MPS, such as IP QoS suppot, with the advantages of host-based mico-mobility schemes, such as low-latency handoves. Fo those capabilities, this scheme used a domain-based appoach to addess micomobility management. Each access MPS domain has one gateway node. Within a wieless access MPS domain, multiple SPs ae fomed between each AP and a gateway to M egistation equest egistation eply FA S J Modify outing table egistation equest egistation eply A S I SP setup Modify label table Fig.. egistation pocedue in a foeign netwok. suppot multiple FEs, and the gateway maintains the packet fowading table. This scheme can esult in waste of esouces. The label edge mobility agent (EMA)-based MPS poposal [] had some advantages, such as a distibuted and scalable natue, the ability to povide fo QoS though taffic engineeing, ease of gadual deployment, and efficient design and handove pefomance. One of the key diffeentiating factos of this scheme is that the mobile has the flexibility to ceate its own hieachy of agents based on its mobility patten, the bandwidth availability in the netwok, and othe factos. Although this scheme has moe advantages than othe hieachical mobility schemes, it also has moe signaling taffic fo suppoting handoves by using the EMA concept. This means that even though an M changes its EMA within the same administative domain by handove, seveal signaling messages, such as ediect equest, ediect confim, and binding update towad the A, occu if it is an uppe level EMA. ETI Jounal, Volume 5, Numbe 5, Octobe Seong Gon hoi et al. 7

4 . ee we povide an intoduction to the. It is impotant to ealize that IP switching is essentially independent of the, and vice vesa. The is used solely to contol a switch (e.g., an MPS-based oute) []. The consists of a contolle and a slave. The contolle could be any geneal-pupose compute. The potocol allows the contolle to Public Netwok Administative Domain BG BG S AS AS S G S AS AP Establish and elease connections, Add and delete leaves, Pefom pot management, equest data (configuation infomation, statistics). In addition, the potocol allows the slave to infom the contolle if something inteesting happens on the switch. The contains some messages fo statistics gatheing, e.g., geneal pot and switch management. Thee ae six classes of equest/esponse messages: connection management, pot management, state and statistics, configuation, esevation management, and QoS. The slave can infom the contolle of an attachement o detachment of an M by using the messages if a handove occus, so when the is used fo mobility suppot, we can efficiently handle the mobility, and the handove latency time can be educed. In addition, if an M changes its AP within the same administative domain, it does not need to infom its A of the handove. In this way, the contolle can change the MPS path by diectly modifying the label infomation at the cossove S on the MPS netwok. BG: Bode Gateway AP: Access Point S : abel Switched oute AS: Access abel Switched oute G: ontolle Fig.. Mobile netwok model in an MPS domain. III. -Based Mobility Management Pocedue fo Suppoting Mobility We appoach mobility management on an MPS netwok using the and mainly deal with the handove pocess. We conside the netwok achitectue of Fig., whee the administative domain unde consideation uses MPS and the. Each access MPS domain has one contolle node. The contolle is connected with all outes, which ae logically slaves. An M communicates with one o moe access points (APs) that ae connected to access Ss (ASs). We apply ou scheme in an MPS domain fo a micomobility solution. Within an MPS domain, SPs ae fomed between each AP and a bode gateway (BG). Multiple SPs ontolle ontolle - VS VS M N S A S B S D S E S F S I S J S S SP SP VS : Vitual Switch ontol (ex, inteface) - :ontolle to ontolle Inteface Fig.. An achitectue using on an MPS netwok. 7 Seong Gon hoi et al. ETI Jounal, Volume 5, Numbe 5, Octobe

5 ae ceated between an AP and a BG to suppot multiple FEs that can be mapped to signaling taffic and diffeent classes, and SPs ae newly established between the BGs and the APs. If the public netwok is an MPS netwok, the BGs ae edge Ss. Fom now, we assume that a public netwok is also an MPS netwok. The contolle is connected to each slave (Fig. ), so all infomation about the SPs can be sent to the contolle. Seveal key diffeentiating factos of this scheme, as opposed to othe hieachical and MPS-based mobility schemes, ae as follows: all infomation about SPs can be sent to the contolle and stoed using the. An M s handove can be detected at the contolle via a slave. If a handove occus, contolle can easily announce the SP elease to the old S I and also establish a new path towad S J at the cossove oute () using stoed SPs infomation in the contolle (Fig. ). Thus, no update message within the same domain is sent to the A at a handove pocess. Fo the situation in Fig., in ode to maintain othe domains, we should define the contolle-to-contolle inteface. A contolle in a diffeent domain epots events though this inteface. The events may be simila to typical messages, but we leave this as a futhe study.. SP onfiguation At fist, multiple SPs between each AP and a BG ae povisioned statically. A netwok opeato ceates them based on netwok povisioning policies. We efe to this SP setup scheme as a static SP configuation scheme. The static SP configuation is good fo use with diffeentiated sevice models fo suppoting IP QoS sevices, and has been poposed by the IETF [9]. When one S in an ongoing MPS path has a poblem and cannot be used, the contolle detects an altenative path using its esouce table. Afte that, the contolle makes the coesponding Ss update each label table. We call this a dynamic SP configuation scheme. The dynamic SP configuation scheme is used to suppot the integated sevice model and to impove netwok eliability. In this pape, we conside that the static SP configuation is used fist, and the dynamic SP configuation can be used when a handove occus.. egistation Pocedue ) An M sends a egistation message afte it eceives agent advetisement messages boadcasted by an AP. ) The AP fowads the egistation message using the peestablished signaling SP between itself and a BG. ) When the BG eceives the egistation message, it updates its fowading table by associating the MN s IP addess with the inteface fom which the egistation message was eceived. If the wieless access MPS domain is not the MN s home domain, the BG sends a egistation message to the MN s A so that packets destined fo the MN can be tunneled fom the A to the FA. ) At the same time, each S coesponding to the SP infoms the contolle of its state with egad to the SP.. andove Pocedue Figue 5 shows the handove management pocedue in which is the cossove oute, and S I and S J ae the old FA and the new FA, espectively. outing table (state and esouce infomation each node) slave ontolle slave S I esouce state & statistics table (SP connection infomation) Fig. 5. The path e-establishing pocedue. slave S J If an M moves into the S J, and it sends a egistation equest message, then the S J infoms the contolle of the attachment of the M (step ). Immediately on eceiving the message, the contolle examines the esouce table about the SP (step ). Afte this pocess, it can detect an altenative path fom the outing table (step ). Afte choosing the altenative path with the link and node state, the contolle odes slave to modify the label table (step ). Figue 6 shows an update pocedue of the SP configuation efeence table in the contolle at handove time, whee it is assumed that is connected to S I with pot numbe, and S is connected with pot numbe 5. is also connected to S I with out label value 6 at pot numbe, and it is connected to S with out label value 8 at pot numbe 5. ETI Jounal, Volume 5, Numbe 5, Octobe Seong Gon hoi et al. 7

6 esv ID in Fig. 6 indicates the esouce state of the system. If the esv ID of S F in SP of the configuation efeence table is, S F is being used fo SP. If the esv ID is o any othe numbe, then the pot of the system may be eseved as one fo the SP. S F # : abel SP SP Table SPID Node S F S F Node S I 6 Node S I S M SP onfiguation efeence Table S esv ID In Pot Out Pot S F S I SP onfiguation efeence Table S esv ID In Pot Out Pot S F S 5 S J Node S J 8 Node5 In abel 6 In abel S... Out abel 6 Out abel 8 8 Fig. 6. Fowading table in the contolle. S J SP Figue 6 shows that an M is in the S I egion at fist and uses SP. If the M moves into S J fom S I, the M is seved by SP, so the contolle odes to change its out label value to 8 and its out pot numbe to 5 fo in label value. It also makes S establish out label value at the out pot numbe fo in label value 8. On the othe hand, packet loss duing handove should be taken into consideation. In geneal, thee ae some ideas, such as buffeing and fowading concepts, fo solving it in a packet netwok using signaling. The buffeing concept is that the cossove S stats to buffe data packets if it detects a handove using the o any othe method. Afte an M finishes the handove pocess, the cossove S sends the buffeed packets to the M in good ode. oweve, it is difficult to detemine the optimized buffe size. Especially in ealtime sevice, a delay poblem may esult fom the queuing delay accoding to the buffeing. The fowading concept is that an old S fist eceives data packets and then fowads them towad the new S. Fo this scheme, the contolle needs to establish a new SP between the old S and the new S. This scheme can also cause tansmission delay because the data packets go to the new S via the old S. Theefoe, in this pape, we conside a diect path change at a cossove S without buffeing data packets. Since all adjacent wieless cells by APs may be ovelapped fo a smooth handove and the contolle easily finds a cossove S ove the data path, a handove can be pefomed at the cossove S without packet loss if the ovelapped egion is well deployed. In othe wods, while an M esides in the ovelapped egion, a pope SP can be selected, and the handove can be pefomed in time. Fo this, seveal factos, such as packet tansmission delay, the M s moving speed, and the pocessing time of each device, should be consideed. We will continue to study this concept as a futhe study. IV. Analysis and Numeical esults In this section, we look into some chaacteistics of ou poposal, compae ou scheme with othe ones, and investigate the oveall pefomance in tems of signaling cost and latency time. We efe to [5] fo the analysis method hee. Ou scheme addesses a fast handove with a shot latency time. This scheme eliminates the signaling towad the emote A of an M as long as the M esides within the same administative domain. An attachment of an M towad a new S in the same administative domain ceates a egistation message only locally. We conside cost and delay fo signaling and packet delivey. In evaluating the latency time, tansmission delay and system time in databases ae consideed. The signaling pocedue of egistation and packet fowading by handove involves the exchange of egistation messages among the netwok elements. The costs fo location management ae associated with the taffic of messages between the entities and the accessing cost of the database. In ode to pesent and evaluate the pefomance of the signaling pocedue, we define the following paametes fo the est of the pape: c is the tansmission cost of messages between an S and a contolle. c is the tansmission cost of messages between an S and anothe S. c is the tansmission cost of messages between a contolle and anothe contolle. α is the weighting facto of the tansmission cost including layes and. β is the weighting facto of the access cost including laye. h is the numbe of total hops associated with the signaling o packet tansmission. a is the oute access cost including laye. 7 Seong Gon hoi et al. ETI Jounal, Volume 5, Numbe 5, Octobe

7 a is the database access cost of an A. a is database access cost of a contolle We also assume that the contolle and S ae modeled as a single exponential seve with an infinite buffe. A designated SP is established fo signaling between the contolle and each S. The aveage system time consists of the sevice time and the waiting time in the queue. It is epesented by s, s, and s. The s is the sevice time fo the pocessing database in the contolle, the s is the sevice time fo the laye pocess in the S accoding to the MPS, and the s is the sevice time fo the laye pocess in a oute in using a pue mobile IP. Each aveage sevice time is /µ, /µ, and /µ fo the contolle, oute, and S, espectively. The waiting times ae denoted by w, w, and w. The message tansmission delay is ignoed because the message length of signaling is vey shot, and the tansmission ate between the netwok elements is vey high. astly, it is assumed that the cost fo update and deletion in the database is the same, and fo simplicity, we deal with the pefomance only with the aveage values without delay jitte. Now we investigate the location egistation cost fo two diffeent cases. One is fo when the M pefoms a handove in the same domain, and the othe is fo when the M pefoms a handove between diffeent domains. When the M pefoms the handove in the same domain, we know that the signaling cost fo tansmission is αhc using the mobile IP fom Fig. 5. Using the, the cost is αhc. On the othe hand, we conside the access cost that involves the contolle and the S. The cost is β [(h ) a + a ] and β a c fo using the mobile IP and fo using the, espectively, whee ac indicates that the contolle efes to two databases, a outing table and a esouce state table, as shown in Fig. 5. The database access cost in using the is not dependent on a, because the signaling taffic is tansmitted at laye using the designated SP. The tansmission cost and access cost fo the handove between diffeent domains in a mobile IP ae equal to the cost fo the handove in the same domain. In using the, the tansmission cost is αhc + αhc. If we assume that the c is equal to the c, then the cost can be αhc. The access cost is βa fo contolle and contolle. onsequently, the aveage location egistation cost, (MIP) and (), can be calculated as: (MIP) = = αhc () = αhc + β a () = αhc + β a, + β[(h )a + a whee and indicate the cost fo handoves inside the ] () same domain and between the diffeent domains, espectively. Next, we investigate the cost fo signaling packet delivey. The packet delivey cost fo a mobile IP is obtained by d (MIP) = αhc + β[(h )a () = αhc + βa, d + a whee the packet delivey cost in using the is not dependent on a, because the packet is tansmitted via laye, and the cost fo laye is consideed with the tansmission cost. The delay of accessing each database, s( ), is ] () s( ) = / µ ( ) + w( ), () whee /µ( ) epesents the aveage pocessing time fo a database and w( ) denotes the waiting time fo the database. Fo example, if the aveage aival ate of location egistation at the contolle is η, then the waiting time is obtained as in [5], [6]. w η µ + η σ =, () η ( ) µ whee σ ( ) is the vaiance of the pocessing time in each database. Accodingly, the delay of the location egistation fo a handove in the same domain with the is a combination of the delay of accessing the S and the contolle. delay() = (h ) s + s µ + σ = (h ) µ + η η µ µ + σ + + η µ η µ whee the fist item is the sevice time of the S, and s indicates that the contolle accesses two databases within itself, the outing table and the esouce state table. Fo M handoves inside the same domain, the delay of location egistation is delay(mip) = (h )s + s When the M pefoms a handove between diffeent domains, the delay is (5) ETI Jounal, Volume 5, Numbe 5, Octobe Seong Gon hoi et al. 75

8 delay(mip) = (h )s delay() = (h )s + s + (s + s whee h indicates that thee ae at least Ss o outes, because an M moves into a diffeent domain. In addition, the s c and s c ae fo the system times fo contolle and contolle, espectively. Theefoe, the aveage delay fo location egistations D (MIP) and D () is D D D D (MIP) = (h )s (MIP) = (h )s () = (h )s () = (h )s + s + s, (h ) + s + s, (s = s = s ),,h ), whee D and D indicate handoves inside the same domain and between diffeent domains, espectively, and h indicates that thee ae at least Ss o outes, because the M moves into a diffeent domain. Fo signaling packet delivey, delay is simila to the case of (). D (MIP) = (h )s d + s D () = (h )s d + s Figue 7 shows the aveage location egistation cost as a function of the numbe of hops passed by a signaling message, whee ase indicates that the handove occus inside the same domain, and ase indicates that the handove occus between diffeent domains. The ase () line stats at numbe of the x axis because we assumed that an M moves into a diffeent domain. Table gives all the paametes used in ou pefomance analysis. Studying this table, we can see that the aveage location egistation cost of using a typical mobile IP inceases significantly. oweve, using the poposed method inceases the cost slightly with an incease in the numbe of hops. The initial cost of using the poposed method is lage than that of the typical mobile IP, because a contolle efes to two databases within itself, the outing table and the esouce state table. oweve, the lage the numbe of hops, the moe effective the poposed method. Figue 8 shows the aveage packet delivey cost fo signaling. In this figue, we can obseve that the aveage packet delivey cost of using the typical mobile IP is always equal to o lage than that of using the, except fo the initial point. At the initial point up to hops, the value fo using the is lage than that of using the Mobile IP, because a contolle efes to two databases within itself. Theefoe, as shown in Figs. 7 and 8, using the poposed method is moe pofitable than using the mobile IP if the. (6) (7) Table. Pefomance analysis paamete. Signaling tansmission cost Access cost Vaiance of DB pocessing time(ms) c c c a c a a σ Aveage pocessing time (ms) Avg. aival ate fo DB eg. (ms - ) Weighting facto /µ /µ /µ /µ η α β egistation cost Packet delivey cost ase (MIP) = ase (MIP) ase () ase () The numbe of hops fo egistation Fig. 7. Aveage location egistation cost. MIP The numbe of hops fo end-to-end packet delivey Fig. 8. Aveage packet delivey cost. numbe of hops fo egistation of the A is lage than when the M esides in the same domain. Figue 9 shows the aveage location egistation delay as a function of the numbe of hops passed by a signaling message, 76 Seong Gon hoi et al. ETI Jounal, Volume 5, Numbe 5, Octobe

9 whee the ase () line stats at numbe of the x axis because we assumed that an M moves into a diffeent domain. In this figue, although the aveage location egistation delay using the poposed method inceases slightly with the numbe of hops, the delay of using the typical mobile IP inceases significantly. While the initial value of the delay fo the poposed method is lage than that fo a mobile IP, it becomes lowe than that of the mobile IP when the numbe of hops inceases. Aveage delay fo egistation (ms) Aveage delay fo end-to-end packet delivey (ms) The numbe of hops fo egistation ase (MIP) = ase (MIP) ase () Fig. 9. Aveage location egistation delay. Fig.. Aveage packet delivey delay. ase () MIP The numbe of hops fo end-to-end packet delivey Figue shows the aveage packet delivey delay fo signaling. In this figue, we can see that the aveage delay of using the typical mobile IP is always equal to o lage than that of using the, except fo the initial point. At an initial point up to hops, the value fo using the is lage than that of using a mobile IP, because a contolle efes to two databases within itself. Theefoe, as shown in Figs. 9 and, using the poposed method is moe pofitable than using the mobile IP if the numbe of hops fo egistation of the A is lage than when the M esides in the same domain. V. onclusion and Futhe Study In this pape, we intoduced a hieachical achitectue fo suppoting mobility by using the on an MPS netwok. Since a contolle can manage its own domain as a centalized seve, the poposed method can diectly change the outing path at a cossove oute when a handove occus. Theefoe, in the poposed method, the fathe the distance between an FA and an A, the moe efficient the latency time and the egistation cost at the handove time. Fo using the poposed method efficiently, fist, the contolle-to-contolle should be studied moe. It can be efficient fo inte-domain handoves. Second, it would be advantageous to aange elations between the notification messages that ae sent to the contolle fom a salve (a new FA) and othe messages when an M pefoms a handove. Thid, the poposed netwok configuation still has the single point of failue although the poposed configuation can be moe eliable than pevious configuations using the gateway concept in a hieachical mobile stuctue. Thus, since the single point of failue is a vey impotant issue, we should conside the poblem as one of the most impotant fo futhe studies. efeences []. Pekins, IP Mobility Suppot, IETF F, Oct []. Pekins and D.B. Johnson, oute Optimization in Mobile IP, IETF Intenet daft, daft-ietf-mobileip-optim-.txt,. [] D.B. Johnson and. Pekins, Mobility Suppot in Ipv6, IETF Intenet daft, daft-ietf-mobileip-ipv6-.txt,. [] E. Gustafsson, A. Jonsson, and E.. Pekins, Mobile IP egional egistation, IETF Intenet daft, daft-ietf-mobileip-eg-tunnel-.txt, Ma.. [5]. amjee, T. a Pota, S. Thuel, K. Vaadhan, and S.Y. Wang, AWAII: A Domain-based Appoach fo Suppoting Mobility in Wide-Aea Wieless Netwoks, Poc. IEEE Int l onf. Netwok Potocols, 999. [6] A.T. ampbell et al., Design, Implementation and Evaluation of ellula IP, IEEE Pesonal ommunications, Aug., pp [7] Yile Guo, Z. Antoniou, and S. Dixit, IP Tanspot in G adio Access Netwoks: an MPS-Based Appoach, Poc. IEEE WN, Olando, Floida, Ma.. [8] Zhong en, hen-khong Tham, hun-hoong Foo, and hi- hung Ko, Integation of Mobile IP and Multi-Potocol abel Switching, Poc. IEEE I, elsinki, Finland, June. [9] eechang Kim, K.-S.D. Wong, Wai hen, and hi eung au, ETI Jounal, Volume 5, Numbe 5, Octobe Seong Gon hoi et al. 77

10 Mobility-Awae MPS in IP-Based Wieless Access Netwoks, Poc. IEEE Globecom, San Antonio, Texas, Nov.. [] F.A. hiussi, D.A. Khotimsky, and S. Kishnan, A Netwok Achitectue fo MPS-Based Mico-Mobility, Poc. IEEE WN, Olando, Floida, Ma.. [] Adian Fael, Paul Bitain, and Philip Matthews, Fault Toleance fo DP and -DP, daft-ietf-mpls-ldp-ft-.txt, May. [] Vishal Shama and Ben-Back ane, Famewok fo MPS-Based ecovey, IETF daft-ietf-mpls-ecovey-fmwk-.txt, Ma.. [] Avi Doia and Tom Woste, Geneal Switch Management Potocol daft-ietf-gsmp-8. txt, available at html.chates/gsmp-chate.html, Nov.. [] Buce Davie and Yakov ekhte, MPS Technology and Applications, Mogan Kaufmann Publishes,. [5] Wenye Wang and Ian F. Akyildiz, A ost-efficient Signaling Potocol fo Mobility Application Pat (MAP) in IMT- Systems, AM SIGMOBIE, ome, Italy,. [6]. Kleinock, Queueing Systmes Volume : TEOY, John Wiley & Sons, 975. Seong Gon hoi eceived his BS degee in electonics fom Kyung Pook National Univesity in 99 and MS degee fom Infomation and ommunications Univesity (IU) in 999. e woked fo G Infomation and ommunications duing e is cuently taking a doctoal couse in IU in Daejeon, Koea. is eseach inteests include mobility, high-speed netwok achitectue, and potocol. yun Joo Kang eceived the MS degee in netwoks fom Infomation ommunications Univesity (IU) in Koea in. She joined the Netwok eseach aboatoy at the Electonic and Telecommunicatins eseach Institute (ETI) in Daejeon, Koea, whee she has done session initiation potocol (SIP) poxy of VoIP. She is cuently studying DTV steaming technology and sevice level ageement in diff-sev netwoks. Jun Kyun hoi eceived his BS degee in electonics fom Seoul National Univesity in 98 and MS and PhD degees fom KAIST in 985 and 988. e woked fo ETI duing e is cuently woking as an Associate Pofesso in Infomation and ommunications Univesity in Daejeon, Koea. is eseach inteests include high-speed netwok achitectue and potocol. 78 Seong Gon hoi et al. ETI Jounal, Volume 5, Numbe 5, Octobe