《信息网络协议基础》课程教学资源（学习资料）MOBILITY MANAGEMENT FOR ALL-IP MOBILE NETWORKS：MOBILE IPV6 VS. PROXY MOBILE IPV6

ARCHITECTURES AND PROTOCOLS FOR MOBILITY MANAGEMENT IN ALL-IP MOBILE NETWORKS MOBILITY MANAGEMENT FOR ALL-IP MOBILE NETWORKS: MOBILE IPV6 VS.PROXY MOBILE IPV6 KI-SIK KONG AND WONJUN LEE,KOREA UNIVERSITY YOUN-HEE HAN,KOREA UNIVERSITY OF TECHNOLOGY AND EDUCATION MYUNG-KI SHIN,ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE(ETRI) HEUNGRYEOL YOU,KOREA TELECOMMUNICATION(KT) MAG ABSTRACT Force (IETF),Third Generation Partnership Project (3GPP),and International Telecommu Recently,a network-based mobility manage- nication Union-Telecommunication Standard- ment protocol called Proxy Mobile IPv6 ization Sector (ITU-T)appear to increase the (PMIPv6)is being actively standardized by the possibility of realizing mobile and ubiquitous IETF NETLMM working group,and is starting computing environments.However,many chal- MAG to attract considerable attention among the lenges still remain to be solved for achieving telecommunication and Internet communities. such a goal. Unlike the various existing protocols for IP The recent fundamental networking trend has mobility management such as Mobile IPv6 been focused mostly on realizing all-IP mobile (MIPv6),which are host-based approaches,a networks.All-IP mobile networks,which are IN-HoA) network-based approach such as PMIPv6 has expected to combine the Internet and telecom- s long as salient features and is expected to expedite the munication networks tightly together,are net- e domain Proxy care-of addre real deployment of IP mobility management.In works in which IP is employed from a mobile The address c this article,starting by showing the validity of a subscriber to the access points (APs)that con- This will be the tur network-based approach,we present qualitative nect the wireless networks to the Internet.One and quantitative analyses of the representative of the most important and challenging issues for The authors present host-based and network-based mobility manage- next-generation all-IP mobile networks is mobili- ment approaches (i.e.,MIPv6 and PMIPv6), ty management.Mobility management enables the qualitative and which highlight the main desirable features and the serving networks to locate a mobile sub- key strengths of PMIPv6.Furthermore,a com- scriber's point of attachment for delivering data quantitative analyses prehensive comparison among the various exist- packets (i.e.,location management)and main- of the representative ing well-known mobility support protocols is tain a mobile subscriber's connection as it con- investigated.Although the development of tinues to change its point of attachment (i.e.. host-based and the PMIPv6 is at an early stage yet,it is strongly handover management). expected that PMIPv6 will be a promising candi- Mobile IPv6(MIPv6)[1]is one of the most representative net- date solution for realizing the next-generation representative efforts on the way toward next- work-based mobility all-IP mobile networks. generation all-IP mobile networks.However, although MIPv6 is a well-known mature stan- management INTRODUCTION dard for IPv6 mobility support and solves many problems seen in Mobile IPv4(MIPv4)[2],it has approaches. With the rapid growth in the number of mobile still revealed some problems such as handover subscribers and mobile devices such as cellular latency,packet loss,and signaling overhead.Fur- phones,personal digital assistants(PDAs),and thermore,despite the reputation of this proto- laptop computers,the demand for "anywhere, col,it has been slowly deployed in real anytime,and any way"high-speed Internet implementations over the past years,and does access is becoming a primary concern in our not appear to receive widespread acceptance in lives.Recent advances in various wireless access the market [3,4].Recently,a network-based technologies such as IEEE 802.16d/e and wide- mobility management protocol called Proxy band code-division multiple access(WCDMA) Mobile IPv6(PMIPv6)[5]is being actively stan- and the incessant efforts of several standards dardized by the IETF NETLMM working group, bodies such as the Internet Engineering Task and is starting to attract considerable attention 36 1536-1284/08/$25.00©2008IEEE EEE Wireless Communications.April 2008

36 1536-1284/08/$25.00 © 2008 IEEE IEEE Wireless Communications • April 2008 MAG MAG Proxy care-of addre The address o This will be the tunne (MN-HoA) as long as me domain ARCHITECTURES AND PROTOCOLS FOR MOBILITY MANAGEMENT IN ALL-IP MOBILE NETWORKS INTRODUCTION With the rapid growth in the number of mobile subscribers and mobile devices such as cellular phones, personal digital assistants (PDAs), and laptop computers, the demand for “anywhere, anytime, and any way” high-speed Internet access is becoming a primary concern in our lives. Recent advances in various wireless access technologies such as IEEE 802.16d/e and wide￾band code-division multiple access (WCDMA) and the incessant efforts of several standards bodies such as the Internet Engineering Task Force (IETF), Third Generation Partnership Project (3GPP), and International Telecommu￾nication Union — Telecommunication Standard￾ization Sector (ITU-T) appear to increase the possibility of realizing mobile and ubiquitous computing environments. However, many chal￾lenges still remain to be solved for achieving such a goal. The recent fundamental networking trend has been focused mostly on realizing all-IP mobile networks. All-IP mobile networks, which are expected to combine the Internet and telecom￾munication networks tightly together, are net￾works in which IP is employed from a mobile subscriber to the access points (APs) that con￾nect the wireless networks to the Internet. One of the most important and challenging issues for next-generation all-IP mobile networks is mobili￾ty management. Mobility management enables the serving networks to locate a mobile sub￾scriber’s point of attachment for delivering data packets (i.e., location management) and main￾tain a mobile subscriber’s connection as it con￾tinues to change its point of attachment (i.e., handover management). Mobile IPv6 (MIPv6) [1] is one of the most representative efforts on the way toward next￾generation all-IP mobile networks. However, although MIPv6 is a well-known mature stan￾dard for IPv6 mobility support and solves many problems seen in Mobile IPv4 (MIPv4) [2], it has still revealed some problems such as handover latency, packet loss, and signaling overhead. Fur￾thermore, despite the reputation of this proto￾col, it has been slowly deployed in real implementations over the past years, and does not appear to receive widespread acceptance in the market [3, 4]. Recently, a network-based mobility management protocol called Proxy Mobile IPv6 (PMIPv6) [5] is being actively stan￾dardized by the IETF NETLMM working group, and is starting to attract considerable attention KI-SIK KONG AND WONJUN LEE, KOREA UNIVERSITY YOUN-HEE HAN, KOREA UNIVERSITY OF TECHNOLOGY AND EDUCATION MYUNG-KI SHIN, ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE (ETRI) HEUNGRYEOL YOU, KOREA TELECOMMUNICATION (KT) ABSTRACT Recently, a network-based mobility manage￾ment protocol called Proxy Mobile IPv6 (PMIPv6) is being actively standardized by the IETF NETLMM working group, and is starting to attract considerable attention among the telecommunication and Internet communities. Unlike the various existing protocols for IP mobility management such as Mobile IPv6 (MIPv6), which are host-based approaches, a network-based approach such as PMIPv6 has salient features and is expected to expedite the real deployment of IP mobility management. In this article, starting by showing the validity of a network-based approach, we present qualitative and quantitative analyses of the representative host-based and network-based mobility manage￾ment approaches (i.e., MIPv6 and PMIPv6), which highlight the main desirable features and key strengths of PMIPv6. Furthermore, a com￾prehensive comparison among the various exist￾ing well-known mobility support protocols is investigated. Although the development of PMIPv6 is at an early stage yet, it is strongly expected that PMIPv6 will be a promising candi￾date solution for realizing the next-generation all-IP mobile networks. MOBILITY MANAGEMENT FOR ALL-IP MOBILE NETWORKS: MOBILE IPV6 VS. PROXY MOBILE IPV6 The authors present the qualitative and quantitative analyses of the representative host-based and the representative net￾work-based mobility management approaches. KONG LAYOUT 4/9/08 11:02 AM Page 36

among the telecommunication and Internet com- mance improvement in MIPv6.However,MIPv6 Compared to munities.Unlike the various existing protocols and its various enhancements basically require for IP mobility management such as MIPv6, protocol stack modification of the MN in order host-based mobility which are host-based approaches,a network- to support them.In addition,the requirement based approach such as PMIPv6 has salient fea- for modification of MNs may cause increased management tures and is expected to expedite the real complexity on them.On the other hand,in a approaches such as deployment of IP mobility management.To the network-based mobility management approach best of our knowledge,this article is the first to such as PMIPv6,the serving network handles the MIPv6 and its present qualitative and quantitative analyses on mobility management on behalf of the MN:thus. MIPv6 and PMIPv6.In addition,this article pro- the MN is not required to participate in any enhancements,a vides a comprehensive comparison and summary mobility-related signaling.Compared to host- network-based that addresses the main strong and weak points based mobility management approaches such as of PMIPv6 against various existing well-known MIPv6 and its enhancements,a network-based mobility management mobility support protocols. mobility management approach such as PMIPv6 The remainder of this article is organized as has the following salient features and advan- approach such as follows.First,we briefly present overviews and tages discuss problems of host-based mobility manage- Deployment perspective:Unlike host-based PMIPv6 has several ment approaches and then identify several key mobility management,network-based mobility advantages. strengths of the network-based mobility manage- management does not require any modification ment approach.Then we present an overview of of MNs.The requirement for modification of the network-based mobility management MNs can be considered one of the primary rea- approach(i.e.,PMIPv6)to providing IP mobility sons MIPv6 has not been widely deployed in support.Qualitative and quantitative compar- practice,although several commendable MIPv6 isons of PMIPv6 against various existing mobility enhancements have been reported over the past support protocols are thoroughly investigated. years [3,4.Therefore,no requirement for modi- highlighting the main desirable features and key fication of MNs is expected to accelerate the strengths of PMIPv6.Finally,concluding remarks practical deployment of PMIPv6.Such an expec- are given. tation can easily be demonstrated by the fact that in the WLAN switching market,no modifi- WHY NETWORK-BASED cation of the software on MNs has been required to support IP mobility,so these unmodified MNs MOBILITY MANAGEMENT? have enabled network service providers to offer services to as many customers as possible [8. Mobile IP is probably the most widely known IP Performance perspective:Generally,wireless mobility support protocol.Two versions of resources are very scarce.In terms of scalability Mobile IP have been standardized for support- efficient use of wireless resources can result in ing host-based mobility on the Internet:MIPv4 enhancement of network scalability.In host- and MIPv6.They support the mobility of IP based network layer approaches such as MIPv6, hosts by allowing them to utilize two IP address- the MN is required to participate in mobility- es:a home address(HoA)that represents the related signaling.Thus,a lot of tunneled mes- fixed address of a mobile node (MN)and a care- sages as well as mobility-related signaling of-address (CoA)that changes with the IP sub- messages are exchanged via the wireless links. net to which an MN is currently attached.In Considering the explosively increasing number terms of the fundamental architectural aspects, of mobile subscribers,such a problem would these two mobility support standards follow the cause serious performance degradation.On the same concept.However,there are slight differ- contrary,in a network-based network layer ences with regard to some important details approach such as PMIPv6,the serving network MIPv6 comprises three components:the MN, controls the mobility management on behalf of the home agent (HA),and the correspondent the MN,so the tunneling overhead as well as a node (CN).The role of the foreign agent (FA) significant number of mobility-related signaling in MIPv4 was replaced by the access router message exchanges via wireless links can be (AR)in MIPv6.In addition,although route opti- reduced.Generally,the signaling latency intro- mization extensions were proposed for both duced by an MN can be significantly affected by MIPv4 and MIPv6,they were only standardized the performance parameters such as wireless for MIPv6.A detailed description of MIPv6 channel access delay and wireless transmission route optimization as well as details of MIPv4 delay.The latencies incurred by such perfor- and MIPv6 can be found in [1,2]. mance parameters can be considerable com- Although MIPv6 is a mature standard for IP pared to those of the wired link;thus,the mobility support and solves many problems,such signaling latency introduced by the MN could as triangle routing,security,and limited IP result in increasing handover failures as wireless address space,addressed in MIPv4,it still has channel access and wireless transmission delays some problems such as handover latency,packet get larger (more details on handover latency can loss,and signaling overhead.Besides,the hand- be found later in this article). over latencies associated with MIPv4/v6 do not Network service provider perspective:From provide the quality of service (QoS)guarantees the perspective of a network service provider,it required for real-time applications.Therefore, is expected that network-based mobility manage various MIPv6 enhancements such as hierarchi- ment would enhance manageability and flexibili- cal Mobile IPv6 (HMIPv6)[6]and fast handover ty by enabling network service providers to for Mobile IPv6(FMIPv6)[7]have been report- control network traffic and provide differentiat- ed over the past years,mainly focused on perfor- ed services and so on.Such a possibility can easi- EEE Wireless Communications.April 2008

IEEE Wireless Communications • April 2008 37 among the telecommunication and Internet com￾munities. Unlike the various existing protocols for IP mobility management such as MIPv6, which are host-based approaches, a network￾based approach such as PMIPv6 has salient fea￾tures and is expected to expedite the real deployment of IP mobility management. To the best of our knowledge, this article is the first to present qualitative and quantitative analyses on MIPv6 and PMIPv6. In addition, this article pro￾vides a comprehensive comparison and summary that addresses the main strong and weak points of PMIPv6 against various existing well-known mobility support protocols. The remainder of this article is organized as follows. First, we briefly present overviews and discuss problems of host-based mobility manage￾ment approaches and then identify several key strengths of the network-based mobility manage￾ment approach. Then we present an overview of the network-based mobility management approach (i.e., PMIPv6) to providing IP mobility support. Qualitative and quantitative compar￾isons of PMIPv6 against various existing mobility support protocols are thoroughly investigated, highlighting the main desirable features and key strengths of PMIPv6. Finally, concluding remarks are given. WHY NETWORK-BASED MOBILITY MANAGEMENT? Mobile IP is probably the most widely known IP mobility support protocol. Two versions of Mobile IP have been standardized for support￾ing host-based mobility on the Internet: MIPv4 and MIPv6. They support the mobility of IP hosts by allowing them to utilize two IP address￾es: a home address (HoA) that represents the fixed address of a mobile node (MN) and a care￾of-address (CoA) that changes with the IP sub￾net to which an MN is currently attached. In terms of the fundamental architectural aspects, these two mobility support standards follow the same concept. However, there are slight differ￾ences with regard to some important details. MIPv6 comprises three components: the MN, the home agent (HA), and the correspondent node (CN). The role of the foreign agent (FA) in MIPv4 was replaced by the access router (AR) in MIPv6. In addition, although route opti￾mization extensions were proposed for both MIPv4 and MIPv6, they were only standardized for MIPv6. A detailed description of MIPv6 route optimization as well as details of MIPv4 and MIPv6 can be found in [1, 2]. Although MIPv6 is a mature standard for IP mobility support and solves many problems, such as triangle routing, security, and limited IP address space, addressed in MIPv4, it still has some problems such as handover latency, packet loss, and signaling overhead. Besides, the hand￾over latencies associated with MIPv4/v6 do not provide the quality of service (QoS) guarantees required for real-time applications. Therefore, various MIPv6 enhancements such as hierarchi￾cal Mobile IPv6 (HMIPv6) [6] and fast handover for Mobile IPv6 (FMIPv6) [7] have been report￾ed over the past years, mainly focused on perfor￾mance improvement in MIPv6. However, MIPv6 and its various enhancements basically require protocol stack modification of the MN in order to support them. In addition, the requirement for modification of MNs may cause increased complexity on them. On the other hand, in a network-based mobility management approach such as PMIPv6, the serving network handles the mobility management on behalf of the MN; thus, the MN is not required to participate in any mobility-related signaling. Compared to host￾based mobility management approaches such as MIPv6 and its enhancements, a network-based mobility management approach such as PMIPv6 has the following salient features and advan￾tages. Deployment perspective: Unlike host-based mobility management, network-based mobility management does not require any modification of MNs. The requirement for modification of MNs can be considered one of the primary rea￾sons MIPv6 has not been widely deployed in practice, although several commendable MIPv6 enhancements have been reported over the past years [3, 4]. Therefore, no requirement for modi￾fication of MNs is expected to accelerate the practical deployment of PMIPv6. Such an expec￾tation can easily be demonstrated by the fact that in the WLAN switching market, no modifi￾cation of the software on MNs has been required to support IP mobility, so these unmodified MNs have enabled network service providers to offer services to as many customers as possible [8]. Performance perspective: Generally, wireless resources are very scarce. In terms of scalability, efficient use of wireless resources can result in enhancement of network scalability. In host￾based network layer approaches such as MIPv6, the MN is required to participate in mobility￾related signaling. Thus, a lot of tunneled mes￾sages as well as mobility-related signaling messages are exchanged via the wireless links. Considering the explosively increasing number of mobile subscribers, such a problem would cause serious performance degradation. On the contrary, in a network-based network layer approach such as PMIPv6, the serving network controls the mobility management on behalf of the MN, so the tunneling overhead as well as a significant number of mobility-related signaling message exchanges via wireless links can be reduced. Generally, the signaling latency intro￾duced by an MN can be significantly affected by the performance parameters such as wireless channel access delay and wireless transmission delay. The latencies incurred by such perfor￾mance parameters can be considerable com￾pared to those of the wired link; thus, the signaling latency introduced by the MN could result in increasing handover failures as wireless channel access and wireless transmission delays get larger (more details on handover latency can be found later in this article). Network service provider perspective: From the perspective of a network service provider, it is expected that network-based mobility manage￾ment would enhance manageability and flexibili￾ty by enabling network service providers to control network traffic and provide differentiat￾ed services and so on. Such a possibility can easi￾Compared to host-based mobility management approaches such as MIPv6 and its enhancements, a network-based mobility management approach such as PMIPv6 has several advantages. KONG LAYOUT 4/9/08 11:02 AM Page 37

The fundamental IP tunnel LMA:Local mobility anchor foundation of PMIPy6 IP-in-IP tunnel between LMA and MAG MAG:Mobile access gateway is based on MIPv6 in the sense that it LMA Home network MN's home network extends MIPv6 (topological anchor point) MAG signaling and re-uses many concepts such &、LMA address(LMAA) That will be the tunnel entry point as the HA functionality. NETLMM domain- However,PMIPv6 is Proxy binding acknowledgment(PBA) MAG Movement management domain)The control message sent by LMA to MAG designed to provide network-based Proxy binding update(PBU) The control messag e sent by MAG to LMA mobility management MN's home address (MN-HoA) to establish a binding to use it as long as between MN-HoA and Proxy-CoA support to an MN in it roams within the same domain Proxy care-of address (Proxy-CoA) atopologicaly The address of MAG. This will be the tunnel end point localized domain. Figure 1.Overview of PMIPv6. ly be expected from legacy cellular systems such ment,and should support any type of wireless as IS-41 and Global System for Mobile Commu- link technology nications (GSM),which can be considered net- Handover performance improvement:A net- work-based (i.e.,network-controlled)systems. work-based approach should minimize the Note that PMIPv6 has some resemblance to time required for handover. General Packet Radio Service (GPRS)in that they are both network-based mobility manage- OVERVIEW OF PMIPV6 ment protocols and have similar functionalities. The fundamental foundation of PMIPv6 is based However,PMIPv6 is an Internet protocol that is on MIPv6 in the sense that it extends MIPv6 sig- not dependent on any access-technology-specific naling and reuses many concepts such as the HA protocol,so it could be used in any IP-based net- functionality.However,PMIPv6 is designed to work,while GPRS is an access-technology-spe- provide network-based mobility management cific protocol closely coupled with the signaling support to an MN in a topologically localized protocols used in legacy cellular systems. domain.Therefore,an MN is exempt from par- ticipation in any mobility-related signaling,and NETWORK-BASED MOBILITY the proxy mobility agent in the serving network performs mobility-related signaling on behalf of MANAGEMENT:PMIPV6 the MN.Once an MN enters its PMIPv6 domain and performs access authentication,the serving In a network-based approach such as PMIPv6, network ensures that the MN is always on its the serving network controls mobility manage- home network and can obtain its HoA on any ment on behalf of the MN:thus,the MN is not access network.That is,the serving network required to participate in any mobility-related assigns a unique home network prefix to each signaling.The design goals the IETF NETLMM MN,and conceptually this prefix always follows working group aims to cover are very extensive. the MN wherever it moves within a PMIPv6 The primary features of such goals are as follows domain.From the perspective of the MN,the (more details are provided in [4,8): entire PMIPv6 domain appears as its home net- .Support for unmodified MNs:Unlike a host- work.Accordingly,it is needless (or impossible) based approach,a network-based approach to configure the CoA at the MN. should not require any software update for IP The new principal functional entities of mobility support on MNs. PMIPv6 are the mobile access gateway (MAG) I Typically,there are vari- Support for IPv4 and IPv6:Although the ini- and local mobility anchor (LMA).The MAG ous link-layer-specific tial design of a network-based approach uses typically runs on the AR.The main role of the events on which the MAG an IPv6 host,it is intended to work with IPv4 MAG is to detect the MN's movements!and ini- can depend for detecting or dual-stack hosts as well. tiate mobility-related signaling with the MN's the MN's attachment and Efficient use of wireless resources:A network- LMA on behalf of the MN.In addition,the detachment within a based approach should avoid tunneling over- MAG establishes a tunnel with the LMA for PMIPv6 domain.For head over a wireless link;hence,it should enabling the MN to use an address from its example,the help of layer minimize overhead within the radio access home network prefix and emulates the MN's 2 triggers such as network. home network on the access network for each MN ATTACH and Link technology agnostic:A network-based MN.On the other hand,the LMA is similar to MN DETACH may be approach should not use any wireless-link-spe- the HA in MIPv6.However,it has additional needed [91. cific information for basic routing manage- capabilities required to support PMIPv6.The 38 EEE Wireless Communications.April 2008

38 IEEE Wireless Communications • April 2008 ly be expected from legacy cellular systems such as IS-41 and Global System for Mobile Commu￾nications (GSM), which can be considered net￾work-based (i.e., network-controlled) systems. Note that PMIPv6 has some resemblance to General Packet Radio Service (GPRS) in that they are both network-based mobility manage￾ment protocols and have similar functionalities. However, PMIPv6 is an Internet protocol that is not dependent on any access-technology-specific protocol, so it could be used in any IP-based net￾work, while GPRS is an access-technology-spe￾cific protocol closely coupled with the signaling protocols used in legacy cellular systems. NETWORK-BASED MOBILITY MANAGEMENT: PMIPV6 In a network-based approach such as PMIPv6, the serving network controls mobility manage￾ment on behalf of the MN; thus, the MN is not required to participate in any mobility-related signaling. The design goals the IETF NETLMM working group aims to cover are very extensive. The primary features of such goals are as follows (more details are provided in [4, 8]): • Support for unmodified MNs: Unlike a host￾based approach, a network-based approach should not require any software update for IP mobility support on MNs. • Support for IPv4 and IPv6: Although the ini￾tial design of a network-based approach uses an IPv6 host, it is intended to work with IPv4 or dual-stack hosts as well. • Efficient use of wireless resources: A network￾based approach should avoid tunneling over￾head over a wireless link; hence, it should minimize overhead within the radio access network. • Link technology agnostic: A network-based approach should not use any wireless-link-spe￾cific information for basic routing manage￾ment, and should support any type of wireless link technology. • Handover performance improvement: A net￾work-based approach should minimize the time required for handover. OVERVIEW OF PMIPV6 The fundamental foundation of PMIPv6 is based on MIPv6 in the sense that it extends MIPv6 sig￾naling and reuses many concepts such as the HA functionality. However, PMIPv6 is designed to provide network-based mobility management support to an MN in a topologically localized domain. Therefore, an MN is exempt from par￾ticipation in any mobility-related signaling, and the proxy mobility agent in the serving network performs mobility-related signaling on behalf of the MN. Once an MN enters its PMIPv6 domain and performs access authentication, the serving network ensures that the MN is always on its home network and can obtain its HoA on any access network. That is, the serving network assigns a unique home network prefix to each MN, and conceptually this prefix always follows the MN wherever it moves within a PMIPv6 domain. From the perspective of the MN, the entire PMIPv6 domain appears as its home net￾work. Accordingly, it is needless (or impossible) to configure the CoA at the MN. The new principal functional entities of PMIPv6 are the mobile access gateway (MAG) and local mobility anchor (LMA). The MAG typically runs on the AR. The main role of the MAG is to detect the MN’s movements1 and ini￾tiate mobility-related signaling with the MN’s LMA on behalf of the MN. In addition, the MAG establishes a tunnel with the LMA for enabling the MN to use an address from its home network prefix and emulates the MN’s home network on the access network for each MN. On the other hand, the LMA is similar to the HA in MIPv6. However, it has additional capabilities required to support PMIPv6. The ■ Figure 1. Overview of PMIPv6. Movement MAG IP tunnel IP-in-IP tunnel between LMA and MAG MAG LMA LMA: Local mobility anchor MAG: Mobile access gateway NETLMM domain (network-based localized mobility management domain) Home network MN’s home network (topological anchor point) LMA address (LMAA) That will be the tunnel entry point Proxy binding acknowledgment (PBA) The control message sent by LMA to MAG Proxy binding update (PBU) The control message sent by MAG to LMA to establish a binding between MN-HoA and Proxy-CoA Proxy care-of address (Proxy-CoA) The address of MAG. This will be the tunnel end point MN’s home address (MN-HoA) MN continues to use it as long as it roams within the same domain 1 Typically, there are vari￾ous link-layer-specific events on which the MAG can depend for detecting the MN’s attachment and detachment within a PMIPv6 domain. For example, the help of layer 2 triggers such as MN_ATTACH and MN_DETACH may be needed [9]. The fundamental foundation of PMIPv6 is based on MIPv6 in the sense that it extends MIPv6 signaling and re-uses many concepts such as the HA functionality. However, PMIPv6 is designed to provide network-based mobility management support to an MN in a topologically localized domain. KONG LAYOUT 4/9/08 11:28 AM Page 38

PBU:Proxy binding update Unlike MIPv6, PBA:Proxy binding acknowledgment a tunnel in PMIPv6 is MN MAG AAA server LMA CN established between (1)MN attachment the LMA and the (2)AAA query with MN-ID MAG,and not an (3)AAA reply with profile MN.This could be (4)PBU with MN-ID desirable because the (5)AAA query with MN-ID tunneling increases the bandwidth (6)AAA reply constraints on the (7)PBA with MN-ID,homhe network prefix option wireless link and Bidirectional tunnel setup Router advertisement the processing burden Data packets. Tunneled data packets on the MN. Data packets Figure 2.Message flow in PMIPv6. main role of the LMA is to maintain reachability message.If the sender is a trusted MAG.the to the MN's address while it moves around with- LMA accepts the PBU message. in a PMIPv6 domain,and the LMA includes a Step 7:Then the LMA sends a proxy binding binding cache entry for each currently registered acknowledgment(PBA)message including the MN.The binding cache entry maintained at the MN's home network prefix option,and sets up LMA is more extended than that of the HA in a route for the MN's home network prefix MIPv6 with some additional fields such as the over the tunnel to the MAG. MN-Identifier,the MN's home network prefix,a Unlike MIPv6.a tunnel in PMIPv6 is estab flag indicating a proxy registration,and the lished between the LMA and the MAG,and interface identifier of the bidirectional tunnel not an MN.This could be desirable because the between the LMA and MAG.Such information tunneling increases the bandwidth constraints associates an MN with its serving MAG.and on the wireless link and the processing burden enables the relationship between the MAG and on the MN.Once the MAG receives the PBA LMA to be maintained. message from the LMA,it has obtained all the Figure 1 illustrates an overview of how required information to emulate the MN's PMIPv6 works within a localized domain.The home network on the access network,and it brief descriptions of the basic terminology are then starts to send a router advertisement (RA) also shown in this figure. message to the MN.It is noted that the RA MESSAGE FLOW OF PMIPV6 message contains the MN's home network pre- fix.After receiving the RA message,the MN Figure 2 shows the message flow of the overall configures its home address by combining the operations in PMIPv6.Each step shown in Fig.2 home network prefix included in the RA mes- is described as follows: sage and its interface address,which is based Steps 1 and 2:When an MN first attaches to an on the supported address configuration mode access network connected to the MAG.the (e.g.,stateless or stateful address configuration access authentication procedure is performed mode)from the policy store.It must be noted using an MN's identity (i.e.,MN-Identifier) that since PMIPv6 only supports the per-MN- via the deployed access security protocols on prefix model and not the shared-prefix model,a the access network. unique home network prefix is assigned to each Step 3:After successful access authentication. MN.Therefore,unlike MIPv6 and its various the MAG obtains the MN's profile.which enhancements,the MN always obtains its contains the MN-Identifier,LMA address, unique home address while it moves within a supported address configuration mode,and so PMIPv6 domain. on from the policy store (e.g.,authentication, After the bidirectional tunnel is successfully authorization,and accounting [AAA]server). set up,all traffic sent from the MN gets routed Step 4:Then the MAG sends a proxy binding to its LMA through the tunnel.The LMA update (PBU)message including the MN- receives any data packets sent by the CN to the Identifier to the MN's LMA on behalf of the MN.The LMA forwards the received packet to MN. the MAG through the tunnel.After receiving Steps 5 and 6:Once the LMA receives the PBU the packets,the MAG on the other end of the message,it checks the policy store to ensure tunnel removes the outer header and forwards that the sender is authorized to send the PBU the packets to the MN. IEEE Wireless Communications.April 2008 39

IEEE Wireless Communications • April 2008 39 main role of the LMA is to maintain reachability to the MN’s address while it moves around with￾in a PMIPv6 domain, and the LMA includes a binding cache entry for each currently registered MN. The binding cache entry maintained at the LMA is more extended than that of the HA in MIPv6 with some additional fields such as the MN-Identifier, the MN’s home network prefix, a flag indicating a proxy registration, and the interface identifier of the bidirectional tunnel between the LMA and MAG. Such information associates an MN with its serving MAG, and enables the relationship between the MAG and LMA to be maintained. Figure 1 illustrates an overview of how PMIPv6 works within a localized domain. The brief descriptions of the basic terminology are also shown in this figure. MESSAGE FLOW OF PMIPV6 Figure 2 shows the message flow of the overall operations in PMIPv6. Each step shown in Fig. 2 is described as follows: Steps 1 and 2: When an MN first attaches to an access network connected to the MAG, the access authentication procedure is performed using an MN’s identity (i.e., MN-Identifier) via the deployed access security protocols on the access network. Step 3: After successful access authentication, the MAG obtains the MN’s profile, which contains the MN-Identifier, LMA address, supported address configuration mode, and so on from the policy store (e.g., authentication, authorization, and accounting [AAA] server). Step 4: Then the MAG sends a proxy binding update (PBU) message including the MN￾Identifier to the MN’s LMA on behalf of the MN. Steps 5 and 6: Once the LMA receives the PBU message, it checks the policy store to ensure that the sender is authorized to send the PBU message. If the sender is a trusted MAG, the LMA accepts the PBU message. Step 7: Then the LMA sends a proxy binding acknowledgment (PBA) message including the MN’s home network prefix option, and sets up a route for the MN’s home network prefix over the tunnel to the MAG. Unlike MIPv6, a tunnel in PMIPv6 is estab￾lished between the LMA and the MAG, and not an MN. This could be desirable because the tunneling increases the bandwidth constraints on the wireless link and the processing burden on the MN. Once the MAG receives the PBA message from the LMA, it has obtained all the required information to emulate the MN’s home network on the access network, and it then starts to send a router advertisement (RA) message to the MN. It is noted that the RA message contains the MN’s home network pre￾fix. After receiving the RA message, the MN configures its home address by combining the home network prefix included in the RA mes￾sage and its interface address, which is based on the supported address configuration mode (e.g., stateless or stateful address configuration mode) from the policy store. It must be noted that since PMIPv6 only supports the per-MN￾prefix model and not the shared-prefix model, a unique home network prefix is assigned to each MN. Therefore, unlike MIPv6 and its various enhancements, the MN always obtains its unique home address while it moves within a PMIPv6 domain. After the bidirectional tunnel is successfully set up, all traffic sent from the MN gets routed to its LMA through the tunnel. The LMA receives any data packets sent by the CN to the MN. The LMA forwards the received packet to the MAG through the tunnel. After receiving the packets, the MAG on the other end of the tunnel removes the outer header and forwards the packets to the MN. ■ Figure 2. Message flow in PMIPv6. PBU: Proxy binding update PBA: Proxy binding acknowledgment (1) MN attachment MN MAG AAA server LMA CN Router advertisement Data packets Data packets Tunneled data packets (2) AAA query with MN-ID (4) PBU with MN-ID (7) PBA with MN-ID, home network prefix option (3) AAA reply with profile (5) AAA query with MN-ID (6) AAA reply Bidirectional tunnel setup Unlike MIPv6, a tunnel in PMIPv6 is established between the LMA and the MAG, and not an MN. This could be desirable because the tunneling increases the bandwidth constraints on the wireless link and the processing burden on the MN. KONG LAYOUT 4/9/08 11:02 AM Page 39

Category MIPv6 PMIPv6 Mobility management type Host-based mobility management Network-based mobility management Mobility scope Global mobility Localized mobility Functionally correspondent entity HA LMA(i.e.,HA functionality with additional capabilities) Topologically correspondent entity AR MAG MN modification Yes No Location registration message Binding update message Proxy binding update message MN address HoA or CoA HoA(always) Relation between tunnel and binding cache entry 1:1 relation (i.e.,HA-MN tunnel) 1:m relation (i.e.,LMA-MAG tunnel) Tunneling over wireless link Required Not required Router advertisement type Broadcast Unicast Lookup key in binding cache HoA MN identifier Addressing model Shared-prefix model Per-MN-prefix model Supported link type Any type of link Point-to-point link Route optimization Supported Not supported Movement detection Required(performed by RS/RA) Not required(performed by layer 2) Duplicate address detection(DAD) Performed at every subnet move Performed only one time(at initial movement into the ment domain) Return routability Required Not required Table 1.Comparison between MIPv6 and PMIPv6. QUALITATIVE ANALYSIS ing some extensions for supporting the IPv4 tun- In this section we qualitatively investigate neling mechanism and specific encapsulation PMIPv6 based on various evaluation criteria and modes. compare it with various existing well-known Basically,PMIPv6 attempts to reuse MIPv6 mobility support protocols as well as MIPv6.A because MIPv6 is a considerably mature proto- synopsis of the main characteristics,including col with several implementations that have the strong and weak points of PMIPv6 compared been realized through interoperability testing. to the various existing well-known mobility sup- Thus,the functionality of the LMA in PMIPv6 port protocols,is provided in Tables 1 and 2. can be considered as an enhanced HA with additional capabilities.In MIPv6 a bidirectional COMPARISON BETWEEN MIPV6 AND PMIPV6 tunnel is established between the HA and each We first compare MIPv6 and PMIPv6 in terms MN,whereas a bidirectional tunnel in PMIPv6 of some high-level characteristics and perfor- is established between the LMA and MAG,not mance aspects,which are shown in Table 1. each MN.This is because the MN is not MIPv6 is a host-based solution for handling the involved in any type of mobility-related signal- global mobility of hosts in IPv6 networks.This ing.As in MIPv4 [2],the bidirectional tunnel means that a host is involved in mobility-related between the LMA and MAG is typically a signaling;thus,a modification of the host proto- shared tunnel,and can be employed for routing col stack is required for operating MIPv6(i.e., traffic streams for different MNs attached to an MN sends the BU message for location regis- the same MAG.It extends the 1:1 relation tration).In contrast,PMIPv6 provides a net- between a tunnel and an MN's binding cache work-based solution for handling the localized entry to a 1:m relation,reflecting the shared mobility of hosts in IPv6 networks (i.e.,a net- nature of the tunnel. work entity,the MAG,sends the PBU message MIPv6 employs the shared-prefix model in for location registration).Therefore,no require- which multiple MNs in the same subnet are ment of the hosts is needed.Moreover,PMIPv6 configured with a common IPv6 network prefix. can also support IPv4 as well as IPv6 by specify- In contrast,PMIPv6 employs the per-MN-prefix 40 EEE Wireless Communications.April 2008

40 IEEE Wireless Communications • April 2008 QUALITATIVE ANALYSIS In this section we qualitatively investigate PMIPv6 based on various evaluation criteria and compare it with various existing well-known mobility support protocols as well as MIPv6. A synopsis of the main characteristics, including the strong and weak points of PMIPv6 compared to the various existing well-known mobility sup￾port protocols, is provided in Tables 1 and 2. COMPARISON BETWEEN MIPV6 AND PMIPV6 We first compare MIPv6 and PMIPv6 in terms of some high-level characteristics and perfor￾mance aspects, which are shown in Table 1. MIPv6 is a host-based solution for handling the global mobility of hosts in IPv6 networks. This means that a host is involved in mobility-related signaling; thus, a modification of the host proto￾col stack is required for operating MIPv6 (i.e., an MN sends the BU message for location regis￾tration). In contrast, PMIPv6 provides a net￾work-based solution for handling the localized mobility of hosts in IPv6 networks (i.e., a net￾work entity, the MAG, sends the PBU message for location registration). Therefore, no require￾ment of the hosts is needed. Moreover, PMIPv6 can also support IPv4 as well as IPv6 by specify￾ing some extensions for supporting the IPv4 tun￾neling mechanism and specific encapsulation modes. Basically, PMIPv6 attempts to reuse MIPv6 because MIPv6 is a considerably mature proto￾col with several implementations that have been realized through interoperability testing. Thus, the functionality of the LMA in PMIPv6 can be considered as an enhanced HA with additional capabilities. In MIPv6 a bidirectional tunnel is established between the HA and each MN, whereas a bidirectional tunnel in PMIPv6 is established between the LMA and MAG, not each MN. This is because the MN is not involved in any type of mobility-related signal￾ing. As in MIPv4 [2], the bidirectional tunnel between the LMA and MAG is typically a shared tunnel, and can be employed for routing traffic streams for different MNs attached to the same MAG. It extends the 1:1 relation between a tunnel and an MN’s binding cache entry to a 1:m relation, reflecting the shared nature of the tunnel. MIPv6 employs the shared-prefix model in which multiple MNs in the same subnet are configured with a common IPv6 network prefix. In contrast, PMIPv6 employs the per-MN-prefix ■ Table 1. Comparison between MIPv6 and PMIPv6. Category MIPv6 PMIPv6 Mobility management type Host-based mobility management Network-based mobility management Mobility scope Global mobility Localized mobility Functionally correspondent entity HA LMA (i.e., HA functionality with additional capabilities) Topologically correspondent entity AR MAG MN modification Yes No Location registration message Binding update message Proxy binding update message MN address HoA or CoA HoA (always) Relation between tunnel and binding cache entry 1:1 relation (i.e., HA-MN tunnel) 1:m relation (i.e., LMA-MAG tunnel) Tunneling over wireless link Required Not required Router advertisement type Broadcast Unicast Lookup key in binding cache HoA MN identifier Addressing model Shared-prefix model Per-MN-prefix model Supported link type Any type of link Point-to-point link Route optimization Supported Not supported Movement detection Required (performed by RS/RA) Not required (performed by layer 2) Duplicate address detection (DAD) Performed at every subnet move￾ment Performed only one time (at initial movement into the domain) Return routability Required Not required KONG LAYOUT 4/9/08 11:02 AM Page 40

Protocol criteria MIPv4 MIPv6 HMIPv6 FMIPv6 Cellular IP SIP SCTP PMIPv6 Network Network Network Network Network Application Transport Network Operating layer layer layer layer layer layer layer layer layer Mobility scope Global Global Local Local/global Local Local/global Local/global Local Location management Yes Yes Yes No Yes Yes No Yes Handover manage- Yes Yes Yes Yes No Yes ment (limited) (limited) Yes Yes Required infra- HA,FA HA HA,MAP HA, Enhanced LMA, enhanced AR Registrar structure BS None MAG MN modification Yes Yes Yes Yes Yes No Yes No Handover latency Bad Bad Moderate Good Good Bad Good Good1 Route optimization No Yes Yes No Yes Yes No 1 Stateless address autoconfiguration is assumed. Table 2.Comparison between PMIPv6 and various well-known mobility support protocols. model.Hence,a unique home network prefix is application layer mobility support protocol (e.g., assigned to each MN,and no other MN shares SIP).A detailed description of each of these this prefix.Therefore,the prefix follows the mobility support protocols is provided in [3,6,7, MN while the MN moves within a PMIPv6 10.In this article we assume that readers are domain,so the network layer movement detec- reasonably familiar with these protocols.Basical- tion and duplicate address detection (DAD) ly,MIPv4/v6 and their enhancement protocols processes are not required within a PMIPv6 except FMIPv6 support location and handover domain (note that for inter-PMIPv6 domain management functionalities to some extent.On movement,network layer movement detection the other hand,SCTP does not support location and DAD are performed)[9].In contrast,for management,and SIP does not support hand- MIPv6,movement detection and DAD,which over management.Therefore,in terms of mobili- are time-consuming operations that can degrade ty management,these protocols might not be handover performance significantly,are essen- entirely suitable by themselves.Realizing suc- tial during every subnet movement.With regard cessful deployment of MIPv4/v6 and their to some aspects such as movement detection, enhancement protocols basically requires the DAD,and return routability [1],it can easily be addition or modification of some functionality in deduced that PMIPv6 is superior to MIPv6,as both the network and MN.In contrast,PMIPv6 shown in Table 1.However,for route optimiza- requires no modification of the MN's protocol tion,PMIPv6 does not have a corresponding stack. capability.In PMIPv6 an individual RA mes- Generally,most of existing mobility support sage should be unicast to the MN because protocols have been developed for their own PMIPv6 only supports the per-MN-prefix characteristic purposes and suitable environ- model.However,MIPv6 supports the shared- ments.For example,Cellular IP,HMIPv6,and prefix model;thus,the RA message is broad- PMIPv6 have been proposed to reduce handover cast in the same network.The choice of the and registration latencies in a localized domain per-MN-prefix model in PMIPv6 conflicts with Similar to PMIPv6.Cellular IP maintains a sin- the use of a shared link layer (e.g.,Ethernet, gle IP address while changing subnets within a IEEE 802.11)as the last hop in a PMIPv6 domain.However,it has some inherent draw- domain.Hence,the type of supported link in backs.such as lack of scalability,incurred by PMIPv6 is simply point-to-point.Detailed establishing host-specific routes.For HMIPv6 descriptions are provided in [9]. although it is an efficient localized mobility man- agement protocol that can reduce handover COMPARISON BETWEEN PMIPV6 AND VARIOUS latency significantly compared to MIPv6,it still WELL-KNOWN MOBILITY SUPPORT PROTOCOLS requires movement detection and DAD because the MN's on-link CoA (LCoA)should be newly In Table 2 we provide a summary of the main assigned whenever the MN moves to another characteristics of PMIPv6 compared to various subnet within a domain.However,the perfor- other existing well-known mobility support pro- mance of handover latency in PMIPv6 appears tocols such as MIPv6 enhancements (e.g., to be better than that of HMIPv6 because the HMIPv6 and FMIPv6),IP micromobility proto- MN within a PMIPv6 domain always uses the cols (e.g.,Cellular IP)[10],transport layer same home address,and hence does not perform mobility support protocol (e.g.,SCTP),and movement detection and DAD IEEE Wireless Communications.April 2008 41

IEEE Wireless Communications • April 2008 41 model. Hence, a unique home network prefix is assigned to each MN, and no other MN shares this prefix. Therefore, the prefix follows the MN while the MN moves within a PMIPv6 domain, so the network layer movement detec￾tion and duplicate address detection (DAD) processes are not required within a PMIPv6 domain (note that for inter-PMIPv6 domain movement, network layer movement detection and DAD are performed) [9]. In contrast, for MIPv6, movement detection and DAD, which are time-consuming operations that can degrade handover performance significantly, are essen￾tial during every subnet movement. With regard to some aspects such as movement detection, DAD, and return routability [1], it can easily be deduced that PMIPv6 is superior to MIPv6, as shown in Table 1. However, for route optimiza￾tion, PMIPv6 does not have a corresponding capability. In PMIPv6 an individual RA mes￾sage should be unicast to the MN because PMIPv6 only supports the per-MN-prefix model. However, MIPv6 supports the shared￾prefix model; thus, the RA message is broad￾cast in the same network. The choice of the per-MN-prefix model in PMIPv6 conflicts with the use of a shared link layer (e.g., Ethernet, IEEE 802.11) as the last hop in a PMIPv6 domain. Hence, the type of supported link in PMIPv6 is simply point-to-point. Detailed descriptions are provided in [9]. COMPARISON BETWEEN PMIPV6 AND VARIOUS WELL-KNOWN MOBILITY SUPPORT PROTOCOLS In Table 2 we provide a summary of the main characteristics of PMIPv6 compared to various other existing well-known mobility support pro￾tocols such as MIPv6 enhancements (e.g., HMIPv6 and FMIPv6), IP micromobility proto￾cols (e.g., Cellular IP) [10], transport layer mobility support protocol (e.g., SCTP), and application layer mobility support protocol (e.g., SIP). A detailed description of each of these mobility support protocols is provided in [3, 6, 7, 10]. In this article we assume that readers are reasonably familiar with these protocols. Basical￾ly, MIPv4/v6 and their enhancement protocols except FMIPv6 support location and handover management functionalities to some extent. On the other hand, SCTP does not support location management, and SIP does not support hand￾over management. Therefore, in terms of mobili￾ty management, these protocols might not be entirely suitable by themselves. Realizing suc￾cessful deployment of MIPv4/v6 and their enhancement protocols basically requires the addition or modification of some functionality in both the network and MN. In contrast, PMIPv6 requires no modification of the MN’s protocol stack. Generally, most of existing mobility support protocols have been developed for their own characteristic purposes and suitable environ￾ments. For example, Cellular IP, HMIPv6, and PMIPv6 have been proposed to reduce handover and registration latencies in a localized domain. Similar to PMIPv6, Cellular IP maintains a sin￾gle IP address while changing subnets within a domain. However, it has some inherent draw￾backs, such as lack of scalability, incurred by establishing host-specific routes. For HMIPv6, although it is an efficient localized mobility man￾agement protocol that can reduce handover latency significantly compared to MIPv6, it still requires movement detection and DAD because the MN’s on-link CoA (LCoA) should be newly assigned whenever the MN moves to another subnet within a domain. However, the perfor￾mance of handover latency in PMIPv6 appears to be better than that of HMIPv6 because the MN within a PMIPv6 domain always uses the same home address, and hence does not perform movement detection and DAD. ■ Table 2. Comparison between PMIPv6 and various well-known mobility support protocols. Protocol criteria MIPv4 MIPv6 HMIPv6 FMIPv6 Cellular IP SIP SCTP PMIPv6 Operating layer Network layer Network layer Network layer Network layer Network layer Application layer Transport layer Network layer Mobility scope Global Global Local Local/global Local Local/global Local/global Local Location management Yes Yes Yes No Yes Yes No Yes Handover manage￾ment Yes (limited) Yes (limited) Yes Yes Yes No Yes Yes Required infra￾structure HA, FA HA HA, MAP HA, enhanced AR Enhanced BS Registrar None LMA, MAG MN modification Yes Yes Yes Yes Yes No Yes No Handover latency Bad Bad Moderate Good Good Bad Good Good1 Route optimization No Yes Yes — No Yes Yes No 1 Stateless address autoconfiguration is assumed. KONG LAYOUT 4/9/08 11:02 AM Page 41

The delay between the AR/MAG and CN is tah tac,which is the time required for a packet to am be sent between the AR/MAG and the CN. and not via the HA. The delay between the HA and CN is thc The delay between the mobility agents and AAA is t IP network HA AAA For simplicity,we make the following assump- AR/MAG MAP/LMA tions: Radio For a fair analysis of these protocols under the access same network structure,the administrative network (in case Administrative domain 气 domain can be applied as follows.From the MN (MAP domain in case of HMIPv6 or CN's home home network in case of PMIPv6) network thc perspective of MIPv6,the administrative domain is assumed to be simply a foreign net- work.From the perspective of HMIPv6,it is assumed to be a foreign MAP domain.Simi- CN larly,for PMIPv6,it is assumed to be a home network domain because the MN always Figure 3.A simple analytical model for performance analysis. moves around within a home network regard- less of its point of attachment. Based on the above assumption,the mobility QUANTITATIVE ANALYSIS agents of each protocol follow the mapping scenario shown in Fig.3.For example,if From the viewpoint of the network layer PMIPv6 is considered,the location of the approach,mobility management protocols can LMA is assumed to be the same as that of the be classified into three types of approaches. MAP in HMIPv6 because they both have func- MIPy6 and HMIPv6 can be considered represen- tionalities similar to the HA in MIPv6 within tative host-based global mobility management a localized administrative domain. and representative host-based localized mobility For a fair analysis,we assume that the MNs management protocols,respectively.They have are allowed to access a serving network after been standardized by the IETF,which is the the AAA procedure is completed,and these organization for defining Internet protocols. access delays are assumed to be all the same Similarly,PMIPv6 can be considered a represen- for MIPv6,HMIPv6,and PMIPv6. tative network-based localized mobility manage- Address configuration is only performed by ment protocol.It is also being standardized by means of stateless address autoconfiguration, the IETF.Currently,a network-based global and the time required to combine the network mobility management protocol is not available prefix obtained from the RA message to its and does not appear to be developed,because interface is negligible in the case of address only the MN rather than the network can detect configuration delay. and select a new serving network.Instead,in All the delays mentioned above are symmetric. order to develop a globally deployable Internet- The delay between the MN and CN is shorter based easy-to-use mobility management architec- than the sum of the delays between the MN ture.a combination of host-based global mobility and HA and between the HA and CN. management and network-based localized mobil- For simplicity,router solicitation (RS)mes- ity management would be a good choice [11].In sages are not considered here.Thus,only RA this section we focus on a quantitative analysis messages can affect the movement detection among MIPv6,HMIPv6,and PMIPv6 on hand- of the MN. over latency,which is one of the most critical Generally,IP handover latency can be factors in next-generation all-IP mobile net- expressed as the sum of the movement detection works. delay(TMD),address configuration delay (TDAD), the delay involved in performing the AAA pro- BASIC ASSUMPTIONS AND cedure(T44),and location registration delay HANDOVER LATENCY ANALYSIS (TREG).In this article,more specifically,hand- over latency is defined as the time that elapses For performance analysis,similar to [12],we between the moment the layer 2 handover com- consider a simple analytical model shown in Fig. pletes and the moment the MN can receive the 3.We use the following notations: first data packet after moving to the new point The delay between the MN and AP is imr, of attachment. which is the time required for a packet to be In order to estimate the movement detection sent between the MN and AP through a wire- delay,based on the above assumptions,we only less link. consider the delay caused by the reception of an The delay between the AP and AR/MAG is unsolicited RA message without considering an tra,which is the time between the AP and the RS message.Therefore,in this case the move- AR/MAG connected to the AP. ment detection delay depends on the period of The delay between the AR/MAG and MAP/ the RA message.In [1]it is specified that the LMA (i.e.,the delay between the AR and routers for supporting mobility should be able to MAP in HMIPv6 or between the MAG and be configured with a smaller MinRtrAdvInter- LMA in PMIPV6)is tam val (MinInt)value and MaxRtrAdvInter- The delay between the AR/MAG and HA is val (MaxInt)value in order to allow sending Tah- unsolicited RA messages more often.The mean 42 IEEE Wireless Communications April 2008

42 IEEE Wireless Communications • April 2008 QUANTITATIVE ANALYSIS From the viewpoint of the network layer approach, mobility management protocols can be classified into three types of approaches. MIPv6 and HMIPv6 can be considered represen￾tative host-based global mobility management and representative host-based localized mobility management protocols, respectively. They have been standardized by the IETF, which is the organization for defining Internet protocols. Similarly, PMIPv6 can be considered a represen￾tative network-based localized mobility manage￾ment protocol. It is also being standardized by the IETF. Currently, a network-based global mobility management protocol is not available and does not appear to be developed, because only the MN rather than the network can detect and select a new serving network. Instead, in order to develop a globally deployable Internet￾based easy-to-use mobility management architec￾ture, a combination of host-based global mobility management and network-based localized mobil￾ity management would be a good choice [11]. In this section we focus on a quantitative analysis among MIPv6, HMIPv6, and PMIPv6 on hand￾over latency, which is one of the most critical factors in next-generation all-IP mobile net￾works. BASIC ASSUMPTIONS AND HANDOVER LATENCY ANALYSIS For performance analysis, similar to [12], we consider a simple analytical model shown in Fig. 3. We use the following notations: • The delay between the MN and AP is tmr, which is the time required for a packet to be sent between the MN and AP through a wire￾less link. • The delay between the AP and AR/MAG is tra, which is the time between the AP and the AR/MAG connected to the AP. • The delay between the AR/MAG and MAP/ LMA (i.e., the delay between the AR and MAP in HMIPv6 or between the MAG and LMA in PMIPv6) is tam. • The delay between the AR/MAG and HA is tah. • The delay between the AR/MAG and CN is tac, which is the time required for a packet to be sent between the AR/MAG and the CN, and not via the HA. • The delay between the HA and CN is thc. • The delay between the mobility agents and AAA is ta. For simplicity, we make the following assump￾tions: • For a fair analysis of these protocols under the same network structure, the administrative domain can be applied as follows. From the perspective of MIPv6, the administrative domain is assumed to be simply a foreign net￾work. From the perspective of HMIPv6, it is assumed to be a foreign MAP domain. Simi￾larly, for PMIPv6, it is assumed to be a home network domain because the MN always moves around within a home network regard￾less of its point of attachment. • Based on the above assumption, the mobility agents of each protocol follow the mapping scenario shown in Fig. 3. For example, if PMIPv6 is considered, the location of the LMA is assumed to be the same as that of the MAP in HMIPv6 because they both have func￾tionalities similar to the HA in MIPv6 within a localized administrative domain. • For a fair analysis, we assume that the MNs are allowed to access a serving network after the AAA procedure is completed, and these access delays are assumed to be all the same for MIPv6, HMIPv6, and PMIPv6. • Address configuration is only performed by means of stateless address autoconfiguration, and the time required to combine the network prefix obtained from the RA message to its interface is negligible in the case of address configuration delay. • All the delays mentioned above are symmetric. • The delay between the MN and CN is shorter than the sum of the delays between the MN and HA and between the HA and CN. • For simplicity, router solicitation (RS) mes￾sages are not considered here. Thus, only RA messages can affect the movement detection of the MN. Generally, IP handover latency can be expressed as the sum of the movement detection delay (TMD), address configuration delay (TDAD), the delay involved in performing the AAA pro￾cedure (TAAA), and location registration delay (TREG). In this article, more specifically, hand￾over latency is defined as the time that elapses between the moment the layer 2 handover com￾pletes and the moment the MN can receive the first data packet after moving to the new point of attachment. In order to estimate the movement detection delay, based on the above assumptions, we only consider the delay caused by the reception of an unsolicited RA message without considering an RS message. Therefore, in this case the move￾ment detection delay depends on the period of the RA message. In [1] it is specified that the routers for supporting mobility should be able to be configured with a smaller MinRtrAdvInter￾val (= MinInt) value and MaxRtrAdvInter￾val (= MaxInt) value in order to allow sending unsolicited RA messages more often. The mean ■ Figure 3. A simple analytical model for performance analysis. MN CN AAA ta tmr ta ta tac thc tah AR/MAG Administrative domain (MAP domain in case of HMIPv6 or home network in case of PMIPv6) Radio access network MAP/LMA IP network CN’s home network tra tam HA Home network (in case of MIPv6) AAA KONG LAYOUT 4/9/08 11:03 AM Page 42

time between unsolicited RA messages can be PMIPv6 can be composed of the sum of the Unlike MIPv6 and expressed as (MinInt MaxInt)/2.Therefore AAA access delay(T4),the registration delay for simplicity,we assume that the mean value of between the MAG and LMA (TRv6),and the HMIPV6,PMIPV6 movement detection delay(TMD)in MIPv6 and packet transmission delay from the MAG to the HMIPv6 is half of the mean time between unso- MN (i.e.,(tmr +tra)).Finally,the handover does not require the licited RA messages;thus,TMD =(MinInt latency in PMIPv6 (DPv6)within a PMIPv6 movement detection MaxInt)/4.More detailed analysis of movement domain can be simply expressed as follows: detection delay can be found in our previous and the DAD study [13].After an MN detects network layer DHgIPv6 TAA TRegv6 tmr +tra (3) movement,new prefix information of the net- processes except work (or subnet)becomes available to the MN where TReov6 2tam when the MN first From the prefix information,a new CoA is gen- erated by means of IPv6 stateless (or stateful) NUMERICAL RESULTS enters a PMIPV6 address autoconfiguration.In order to verify the Here,we show the numerical results based on the uniqueness of this CoA,it performs the DAD analysis derived in the previous subsection. domain.In addition, process before combining the network prefix to Although we only focus on analyzing the handover its interface.During this process,the MN cannot latency within a domain in order to simplify the the MN's movement use the CoA for communication.Therefore analysis because there are various possible scenar- within a PMIPv6 according to [13],the DAD delay in MIPv6 and ios [15]for interdomain movement,we believe HMIPv6 can be simply expressed as TDAD R x that this analysis could fully reflect the main fea- domain is also D,where R and D denote RetransTimer and tures of each protocol.For our analysis,t is DupAddrDetectTransmits specified in [14] assumed to be 10 ms,considering the relatively fransparent to the respectively.From the perspective of network low bandwidth in the wireless link,and the other outside of the service providers.in order to make mobile ser- parameters used are as follows:tr=2 ms,Im= vices feasible in public wireless Internet,AAA the =10 ms,tah tac 20 ms,and ta 3 ms, PMIPv6 domain. functions performed by AAA protocols such as respectively.All these values are the same or simi- DIAMETER must be implemented.Based on lar to the parameter setting values given in [12 the above assumption,these access delays(T444) We set MinInt 30 ms and MaxInt 70 ms [1 are all the same;thus,T44 =2 x 2ta=4ta for and R 1000 ms and D 1 [13,16],respectively. the three protocols(i.e.,one access is performed between AR/MAG and AAA.the other between Impad of Wireless Link Delay-Figure 4a shows the HA/MAP/LMA and AAA). impact of t on handover latency.For all of the On the other hand,the registration delay in mobility support protocols,it can be observed MIPv6(TREG)requires the time equivalent to that handover latencies increase with the wire. the sum of the HA registration delay (i.e.,2(tmr less link delay even if the slopes of each graph +tra+tah))and the CN registration delay (i.e., are different from each other.MIPv6 is most 2(Imr +tra tac)).Moreover,in order to register affected by the change in wireless link delay with the CN,the delay for return routability (i.e.. because it requires the largest number of mes- 2(tmr +tra tah+the))[1]is additionally sages (e.g.,the message exchanges for the BU or required prior to the CN registration.Therefore, binding acknowledgment(BA)to/from the HA including all the factors mentioned above,the the return routability procedure,and the BU for handover latency in MIPv6(DAPv6)can be the CN)to be exchanged over the wireless link. expressed as follows: In contrast,PMIPv6 is least affected because the MN is not involved in mobility-related signaling DMo6 TMD TDAD Taa T In particular,it must be noted that the handover latencies of MIPv6 and HMIPv6 based on RFC where T=6(tmr +tra)+4tah 2462 [14]are significantly larger than that of +2(tac +the). PMIPv6.This is because the time required for the DAD process in MIPv6 and HMIPv6 is con- Unlike MIPv6,the registration delay in siderably larger than the delays caused by other HMIPv6(Tv6)only requires the MAP regis- factors that may affect handover latency.As tration delay (i.e,2(tmr tra +tam))without the mentioned earlier,the DAD process is very time requirement of the CN registration delay within consuming.Hence,several efforts to optimize a MAP domain.This is because the MN's move- DAD latency have been undertaken.For exam- ment within a MAP domain is transparent out- ple,the IETF IPv6 working group has attempted side of the MAP domain.Therefore,including to revise RFC 2462,which specifies that the IPv6 all the factors mentioned above.the handover DAD process consumes at least 1000 ms,and latency in HMIPv6 (DfIPv6)within a MAP some enhancements such as optimistic DAD domain can be expressed as follows: (oDAD,RFC 4429 [17])have been made recent- ly.Based on the premise that DAD is far more DHIno TMD TDAD +TA Teupv6 (2) likely to succeed than fail,oDAD provides an approach to eliminate the DAD delay.Although Unlike MIPv6 and HMIPv6,PMIPv6 does oDAD reduces the handover latency in the non- not require movement detection and DAD collision case,it can incur some penalty for both except when the MN first enters a PMIPv6 the optimistic MN and the rightful owner of the domain.In addition,the MN's movement within address if address collision occurs.Hence,for a PMIPv6 domain is also transparent outside of our analysis of handover latency in MIPv6 and the PMIPv6 domain because PMIPv6 is a local- HMIPv6,we evaluated the handover latencies ized mobility management protocol similar to based on both RFC 2462 and RFC 4429,respec- HMIPv6.Therefore,the handover latency in tively. IEEE Wireless Communications.April 2008 43

IEEE Wireless Communications • April 2008 43 time between unsolicited RA messages can be expressed as (MinInt + MaxInt)/2. Therefore, for simplicity, we assume that the mean value of movement detection delay (TMD) in MIPv6 and HMIPv6 is half of the mean time between unso￾licited RA messages; thus, TMD = (MinInt + MaxInt)/4. More detailed analysis of movement detection delay can be found in our previous study [13]. After an MN detects network layer movement, new prefix information of the net￾work (or subnet) becomes available to the MN. From the prefix information, a new CoA is gen￾erated by means of IPv6 stateless (or stateful) address autoconfiguration. In order to verify the uniqueness of this CoA, it performs the DAD process before combining the network prefix to its interface. During this process, the MN cannot use the CoA for communication. Therefore, according to [13], the DAD delay in MIPv6 and HMIPv6 can be simply expressed as TDAD = R × D, where R and D denote RetransTimer and DupAddrDetectTransmits specified in [14], respectively. From the perspective of network service providers, in order to make mobile ser￾vices feasible in public wireless Internet, AAA functions performed by AAA protocols such as DIAMETER must be implemented. Based on the above assumption, these access delays (TAAA) are all the same; thus, TAAA = 2 × 2ta = 4ta for the three protocols (i.e., one access is performed between AR/MAG and AAA, the other between HA/MAP/LMA and AAA). On the other hand, the registration delay in MIPv6 (TREG MIPv6 ) requires the time equivalent to the sum of the HA registration delay (i.e., 2(tmr + tra + tah)) and the CN registration delay (i.e., 2(tmr + tra + tac)). Moreover, in order to register with the CN, the delay for return routability (i.e., 2(tmr + tra + tah+ thc)) [1] is additionally required prior to the CN registration. Therefore, including all the factors mentioned above, the handover latency in MIPv6 (DHO MIPv6) can be expressed as follows: DHO MIPv6 = TMD + TDAD + TAAA + TREG MIPv6 (1) where TREG MIPv6 = 6(tmr + tra) + 4tah + 2(tac + thc). Unlike MIPv6, the registration delay in HMIPv6 (TREG HMIPv6 ) only requires the MAP regis￾tration delay (i.e., 2(tmr + tra + tam)) without the requirement of the CN registration delay within a MAP domain. This is because the MN’s move￾ment within a MAP domain is transparent out￾side of the MAP domain. Therefore, including all the factors mentioned above, the handover latency in HMIPv6 (DHO HMIPv6) within a MAP domain can be expressed as follows: DHO HMIPv6 = TMD + TDAD + TAAA + TREG HMIPv6 (2) Unlike MIPv6 and HMIPv6, PMIPv6 does not require movement detection and DAD except when the MN first enters a PMIPv6 domain. In addition, the MN’s movement within a PMIPv6 domain is also transparent outside of the PMIPv6 domain because PMIPv6 is a local￾ized mobility management protocol similar to HMIPv6. Therefore, the handover latency in PMIPv6 can be composed of the sum of the AAA access delay (TAAA), the registration delay between the MAG and LMA (TREG PMIPv6 ), and the packet transmission delay from the MAG to the MN (i.e., (tmr + tra)). Finally, the handover latency in PMIPv6 (DHO PMIPv6) within a PMIPv6 domain can be simply expressed as follows: DHO PMIPv6 = TAAA + TREG PMIPv6 + tmr + tra (3) where TREG PMIPv6 = 2tam. NUMERICAL RESULTS Here, we show the numerical results based on the analysis derived in the previous subsection. Although we only focus on analyzing the handover latency within a domain in order to simplify the analysis because there are various possible scenar￾ios [15] for interdomain movement, we believe that this analysis could fully reflect the main fea￾tures of each protocol. For our analysis, tmr is assumed to be 10 ms, considering the relatively low bandwidth in the wireless link, and the other parameters used are as follows: tra = 2 ms, tam = thc = 10 ms, tah = tac = 20 ms, and ta = 3 ms, respectively. All these values are the same or simi￾lar to the parameter setting values given in [12]. We set MinInt = 30 ms and MaxInt = 70 ms [1], and R = 1000 ms and D = 1 [13, 16], respectively. Impact of Wireless Link Delay — Figure 4a shows the impact of tmr on handover latency. For all of the mobility support protocols, it can be observed that handover latencies increase with the wire￾less link delay even if the slopes of each graph are different from each other. MIPv6 is most affected by the change in wireless link delay because it requires the largest number of mes￾sages (e.g., the message exchanges for the BU or binding acknowledgment (BA) to/from the HA, the return routability procedure, and the BU for the CN) to be exchanged over the wireless link. In contrast, PMIPv6 is least affected because the MN is not involved in mobility-related signaling. In particular, it must be noted that the handover latencies of MIPv6 and HMIPv6 based on RFC 2462 [14] are significantly larger than that of PMIPv6. This is because the time required for the DAD process in MIPv6 and HMIPv6 is con￾siderably larger than the delays caused by other factors that may affect handover latency. As mentioned earlier, the DAD process is very time consuming. Hence, several efforts to optimize DAD latency have been undertaken. For exam￾ple, the IETF IPv6 working group has attempted to revise RFC 2462, which specifies that the IPv6 DAD process consumes at least 1000 ms, and some enhancements such as optimistic DAD (oDAD, RFC 4429 [17]) have been made recent￾ly. Based on the premise that DAD is far more likely to succeed than fail, oDAD provides an approach to eliminate the DAD delay. Although oDAD reduces the handover latency in the non￾collision case, it can incur some penalty for both the optimistic MN and the rightful owner of the address if address collision occurs. Hence, for our analysis of handover latency in MIPv6 and HMIPv6, we evaluated the handover latencies based on both RFC 2462 and RFC 4429, respec￾tively. Unlike MIPv6 and HMIPv6, PMIPv6 does not require the movement detection and the DAD processes except when the MN first enters a PMIPv6 domain. In addition, the MN’s movement within a PMIPv6 domain is also transparent to the outside of the PMIPv6 domain. KONG LAYOUT 4/9/08 11:03 AM Page 43

Impact of Delay between MN and CN-Figure 4b shows the impact of (tr+tra+tac)on hand- 1600 over latency.Since we evaluate handover latency only for intradomain movement,HMIPv6 and 1400 PMIPv6 do not require registration to the CN because the MN's movement within a domain is 1200 transparent outside the domain.That is,the delay between the MN and CN does not affect 1000 the handover latency of each protocol within a -MIPv6 domain.However.for MIPv6.the handover 800 e-HMIPv6 latency increases with the delay between the MN A-MIPV6- opt and CN.This is because MIPv6 requires regis- 600 HMIPv PMIPv6 tration to both the HA and CN whenever the MN moves across subnets;thus,the increase in 400 the delay between the MN and CN affects the increase in handover latency in MIPv6. 200 Impact of Movement Detection Delay-Figure 4c 0 5 10 15 20 25303540455055 shows the impact of TMp on handover latency. 60 As mentioned earlier,in PMIPv6 movement Wireless link delay (ms) detection does not occur except when the MN (a) moves across a PMIPv6 domain.This is due to the fact that since PMIPv6 only supports the 1400 per-MN-prefix model,a unique home network prefix is assigned to each MN.That is,from the 1200 G perspective of the MN,the entire PMIPv6 domain appears as its home network.In other G words,the MN is not related to movement detec- 1000 tion delay in intradomain movement.On the contrary,the graphs for MIPv6 and HMIPv6 800 -MIPv6 HMIPv6 increase with the same slope as the movement A-MIPv6-opt detection delay does.In MIPv6 and HMIPv6. 600 HMIPv6-opt whenever the MN moves across subnets,it con- PMIPv6 figures the different CoAs via stateless (or state- 400 ful)address autoconfiguration.Therefore,in MIPv6 and HMIPv6,movement detection should be performed as quickly as possible in order to 200 minimize handover latency and packet loss. Increased movement detection delay results in 0 increased handover latency.and this could cause 2025303540455055606570 75 significant degradation to be experienced by the Delay between MN and CN(ms) MNs. (b) CONCLUDING REMARKS 1400 To the best of our knowledge,this article is the first to provide qualitative and quantitative anal- 1200 G yses of MIPv6 and PMIPv6.In this article our analysis results demonstrate the superiority of G PMIPv6.Although various IP mobility support 1000 protocols have been proposed,from the perspec- tive of the practical deployment of each proto- 800 B-MIPv6 col,a confrontation has existed between the -e-HMIPv6 A-MIPv6-opt telecommunications and Internet communities 600 平-HMIPv6-opt for a long time.However,PMIPv6 could be con- PMIPv6 sidered a promising compromise between them. It is a practical derivative of MIPv6 rather than a 400 new idea,and could be considered a turn for the better because it reflects telecommunication 200 operators'favor,enabling them to manage and control their networks more efficiently. Although we have chiefly focused on the 10 2030 40 5060708090100110 120 comparison between MIPv6 and PMIPy6 in this Movement detection delay(ms) article,the interactions between them would also (c) be possible.For example,similar to the HMIPv6 MIPv6 interaction,PMIPv6 could be used as a localized mobility management protocol,where- Figure 4.Comparison between handover latencies in MIPv6,HMIPv6,and as MIPv6 could be used as a global mobility PMIPv6:a)impact of wireless link delay;b)impact of delay between MN and management protocol.Details on the various CN;c)impact of movement detection delay. interaction scenarios and related issues can be 44 IEEE Wireless Communications April 2008

44 IEEE Wireless Communications • April 2008 Impact of Delay between MN and CN — Figure 4b shows the impact of (tmr + tra + tac) on hand￾over latency. Since we evaluate handover latency only for intradomain movement, HMIPv6 and PMIPv6 do not require registration to the CN because the MN’s movement within a domain is transparent outside the domain. That is, the delay between the MN and CN does not affect the handover latency of each protocol within a domain. However, for MIPv6, the handover latency increases with the delay between the MN and CN. This is because MIPv6 requires regis￾tration to both the HA and CN whenever the MN moves across subnets; thus, the increase in the delay between the MN and CN affects the increase in handover latency in MIPv6. Impact of Movement Detection Delay — Figure 4c shows the impact of TMD on handover latency. As mentioned earlier, in PMIPv6 movement detection does not occur except when the MN moves across a PMIPv6 domain. This is due to the fact that since PMIPv6 only supports the per-MN-prefix model, a unique home network prefix is assigned to each MN. That is, from the perspective of the MN, the entire PMIPv6 domain appears as its home network. In other words, the MN is not related to movement detec￾tion delay in intradomain movement. On the contrary, the graphs for MIPv6 and HMIPv6 increase with the same slope as the movement detection delay does. In MIPv6 and HMIPv6, whenever the MN moves across subnets, it con￾figures the different CoAs via stateless (or state￾ful) address autoconfiguration. Therefore, in MIPv6 and HMIPv6, movement detection should be performed as quickly as possible in order to minimize handover latency and packet loss. Increased movement detection delay results in increased handover latency, and this could cause significant degradation to be experienced by the MNs. CONCLUDING REMARKS To the best of our knowledge, this article is the first to provide qualitative and quantitative anal￾yses of MIPv6 and PMIPv6. In this article our analysis results demonstrate the superiority of PMIPv6. Although various IP mobility support protocols have been proposed, from the perspec￾tive of the practical deployment of each proto￾col, a confrontation has existed between the telecommunications and Internet communities for a long time. However, PMIPv6 could be con￾sidered a promising compromise between them. It is a practical derivative of MIPv6 rather than a new idea, and could be considered a turn for the better because it reflects telecommunication operators’ favor, enabling them to manage and control their networks more efficiently. Although we have chiefly focused on the comparison between MIPv6 and PMIPv6 in this article, the interactions between them would also be possible. For example, similar to the HMIPv6- MIPv6 interaction, PMIPv6 could be used as a localized mobility management protocol, where￾as MIPv6 could be used as a global mobility management protocol. Details on the various interaction scenarios and related issues can be ■ Figure 4. Comparison between handover latencies in MIPv6, HMIPv6, and PMIPv6: a) impact of wireless link delay; b) impact of delay between MN and CN; c) impact of movement detection delay. Wireless link delay (ms) (a) 10 200 Handover latency (ms) Handover latency (ms) 0 400 600 800 1000 1200 1400 1600 5 15 20 25 30 35 40 45 50 55 60 MIPv6 HMIPv6 MIPv6-opt HMIPv6-opt PMIPv6 MIPv6 HMIPv6 MIPv6-opt HMIPv6-opt PMIPv6 Delay between MN and CN (ms) (b) 25 200 0 400 600 800 1000 1200 1400 20 30 35 40 45 50 55 60 65 70 75 Handover latency (ms) Movement detection delay (ms) (c) 20 200 0 400 600 800 1000 1200 1400 10 30 40 50 60 70 80 90 100 110 120 MIPv6 HMIPv6 MIPv6-opt HMIPv6-opt PMIPv6 KONG LAYOUT 4/9/08 11:03 AM Page 44

found in [15].Future research will explore cross- August 2007 he was a research professor at Korea Univer- layering issues (e.g.,PMIPv6 over IEEE 802.11 sity and Ewha Womans University.Currently,he is a A confrontation has research professor in the Department of Computer Science or 802.16e networks)as well as route optimiza- and Engineering at Korea University.His research interests existed between the tion and fast handover issues in PMIPv6. include IP mobility/QoS support,performance modeling. and optimization issues in next-generation wireless mobile telecommunication ACKNOWLEDGMENTS networks.He was listed in Marquis Who's Who in Science and Engineering (2006-2007,2008-2009).Who's Who in and the Internet This work was supported in part by the Korea the World (2008),and Outstanding Scientists of the 21st Research Foundation Grant funded by the Kore- Century (2007-2008),respectively. communities for a an Government(MOEHRD)[KRF-2006-331- D00539],and in part by the Ministry of YOUN-HEE HAN [M](yhhan@kut.ac.kr)received his B.S. long time.However, Information and Communication (MIC),Korea, degree in mathematics from Korea University in 1996.He received his M.S.and Ph.D.degrees in computer science under ITRC IITA-2007-(C1090-0701-0046). PMIPv6 could be and engineering from Korea University in 1998 and 2002, respectively.From March 4,2002 to February 28,2006 he REFERENCES was a senior researcher in the Communication and Net- considered as a [1]D.Johnson,C.Perkins,and J.Arkko,"Mobility Support work Group of Samsung Advanced Institute of Technology. in IPv6,"IETF RFC 3775,June 2004. Since March 2,2006 he has been a professor in the School promising [2]C.Perkins,"IP Mobility Support for IPv4,"IETF RFC of Internet-Media Engineering at Korea University of Tech- compromise between 3344.Aug.2002. nology and Education,CheonAn.His primary research [3]N.Banerjee,W.Wu,and S.K Das,"Mobility Support in interests include theory and application of mobile comput- Wireless Internet,"IEEE Wireless Commun.,vol.10,no. ing,including protocol design and performance analysis. them.It is a practical 5,0ct.2003,pp.54-61 Since 2002 his activities have focused on IPv6,IPv6 mobili- [4]J.Kempf,"Problem Statement for Network-Based Local- ty,media-independent handover,and cross-layer optimiza- derivative of MIPv6, ized Mobility Management(NETLMM),"IETF RFC 4830, tion for efficient mobility support in IEEE 802 wireless Apr.2007. networks.He is a member of IEICE.He has also made sev- rather than a eral contributions to leTf and leEe standardization cur. [5]S.Gundavelli et al.,"Proxy Mobile IPv6,"IETF Inter et draft,draft-ietf-netlmm-proxymip6-01.txt,June 2007. rently,he is chair of the IPv6 over WiBro working group of new idea. work in progress. TTA IPv6 Project Group in Korea. [6]H.Soliman,C.Castelluccia,K.E.Malki,and L.Bellier, "Hierarchical Mobile IPv6 Mobility Management MYUNG-KI SHIN(mkshin@etri.re.kr)is currently a senior (HMIPV6),"IETF RFC 4140,Aug.2005 researcher at the Protocol Engineering Center of the Elec- (7]R.Koodli,"Fast Handover for Mobile IPv6,"IETF RFC tronics and Telecommunications Research Institute (ETRI) 4068.Ju2005 Korea.He is a technical leader of the Mobile Router project [8]J.Kempf,"Goals for Network-Based Localized Mobility in ETRI.He has been working on IP protocols since 1994. Management(NETLMM),"IETF RFC 4831,Apr.2007. His research interests include IPv6,Mobile IPv6,multicast, [9]J.Laganier and S.Narayanan,"Network-Based Localized and future network technologies.He was also a guest Mobility Management Interface Between Mobile Node and researcher at the U.S.National Institute of Standards and Mobility Access Gateway,"IETF Internet draft,draft-ietf- Technology in 2004-2005.He is actively involved in IETF IP netlmm-mn-ar-if-02,May 2007,work in progress. related WGs (IPv6,multicast,mobility).He is an author of [10]P.Reinbold and O.Bonaventure,"IP Micro-Mobility several IETF RFCs(RFC 3338,RFC 4038,RFC 4489,etc.).He Protocols,"IEEE Commun.Surveys Tutorials,vol.5, is also a member of the CTO Executive Committee of the no.1,3 rd qtr.2003,pp.40-56. IPv6 Forum.He received a Ph.D.degree in computer engi- [11]P.Roberts and J.Kempf,"Mobility Architecture for the neering doing research on IPv6 multicast and mobility from Global Intemnet,"Proc MobiArch 06,Dec.2006,pp.23-28. Chungnam National University in 2003. [12]H.Faithi and R.Prasad,"Mobility Management for VolP in 3G Systems:Evaluation of Low-Latency Handoff HEUNG-RYEOL You (hryou@kt.com)received B.S.,M.S.,and Schemes,"IEEE Wireless Commun.,vol.12,no.2,Apr. Ph.D.degrees in electronic engineering from Yonsei Univer- 2005,pp.96-104. sity,Seoul,Korea,in 1985,1987,and 2002,respectively. [13]Y.Han,J.Choi,and S.Hwang,"Reactive Handover He has been a research engineer with Korea Telecom Optimization in IPv6-Based Mobile Networks,"/EEE Authority (now KT),Seoul,Korea,since 1987 and is cur- J5AC,vol.24,no.9,5ept.2006,pp.1758-72 rently director of the Infra Laboratory,KT.His research [14]S.Thomson and T.Narten,"IPv6 Stateless Address interests are in the areas of mobility management,seam- Autoconfiguration,"IETF RFC 2462,Dec.1998 less mobility,wireless communication network and system [15]H.Soliman and G.Giaretta,"Interactions Between design,and position location technologies. PMIPv6 and MIPv6:Scenarios and Related Issues,"IETF Internet draft,draft-giaretta-netlmm-mip-interactions. WoNUN LEE [SM](wlee@korea.ac.kr)received B.S.and M.S 00,Apr.2007,work in progress. degrees in computer engineering from Seoul National Uni- [16]T.Narten,E.Nordmark,and W.Simpson,"Neighbor versity in 1989 and 1991,respectively,an M.S.in computer science trom the Universitv of Marvland.colleae Park in Discovery for IP Version 6,"IETF RFC 2461,Dec.1998. [17]N.Moore,"Optimistic Duplicate Address Detection 1996,and a Ph.D.degree in computer science and engi- (DAD)for IPv6,"IETF RFC 4429,Apr.2006. neering from the University of Minnesota,Minneapolis in 1999.In 1998 he was a research associate at Stanford BIOGRAPHIES Research International (SRI),Menlo Park,California.In March 2002 he joined the faculty of Korea University KI-SIK KoNG (kisik.kong@gmail.com)received his B.S.,M.S. where he is currently an associate professor in the Depart- and Ph.D.degrees in computer science and engineering ment of Computer Science and Engineering.He has pub- from Korea University in 1999,2001,and 2005,respective- lished over 45 journal papers with IEEE,Elsevier,and ly.From 1999 to August 2005 he was a researcher in the Springer-Verlag.His research interests include mobile com- Research Institute of Computer Information and Communi- munications and protocol engineering applied to wireless cation at Korea University.From September 2005 to systems. IEEE Wireless Communications April 2008 45

IEEE Wireless Communications • April 2008 45 found in [15]. Future research will explore cross￾layering issues (e.g., PMIPv6 over IEEE 802.11 or 802.16e networks) as well as route optimiza￾tion and fast handover issues in PMIPv6. ACKNOWLEDGMENTS This work was supported in part by the Korea Research Foundation Grant funded by the Kore￾an Government (MOEHRD) [KRF-2006-331- D00539], and in part by the Ministry of Information and Communication (MIC), Korea, under ITRC IITA-2007-(C1090-0701-0046). REFERENCES [1] D. Johnson, C. Perkins, and J. Arkko, “Mobility Support in IPv6,” IETF RFC 3775, June 2004. [2] C. Perkins, “IP Mobility Support for IPv4,” IETF RFC 3344, Aug. 2002. [3] N. Banerjee, W. Wu, and S. K. Das, “Mobility Support in Wireless Internet,” IEEE Wireless Commun., vol. 10, no. 5, Oct. 2003, pp. 54–61. [4] J. Kempf, “Problem Statement for Network-Based Local￾ized Mobility Management (NETLMM),” IETF RFC 4830, Apr. 2007. [5] S. Gundavelli et al., “Proxy Mobile IPv6,” IETF Internet draft, draft-ietf-netlmm-proxymip6-01.txt, June 2007, work in progress. [6] H. Soliman, C. Castelluccia, K. E. Malki, and L. Bellier, “Hierarchical Mobile IPv6 Mobility Management (HMIPv6),” IETF RFC 4140, Aug. 2005. [7] R. Koodli, “Fast Handover for Mobile IPv6,” IETF RFC 4068, July 2005. [8] J. Kempf, “Goals for Network-Based Localized Mobility Management (NETLMM),” IETF RFC 4831, Apr. 2007. [9] J. Laganier and S. Narayanan, “Network-Based Localized Mobility Management Interface Between Mobile Node and Mobility Access Gateway,” IETF Internet draft, draft-ietf￾netlmm-mn-ar-if-02, May 2007, work in progress. [10] P. Reinbold and O. Bonaventure, “IP Micro-Mobility Protocols,” IEEE Commun. Surveys & Tutorials, vol. 5, no. 1, 3rd qtr. 2003, pp. 40–56. [11] P. Roberts and J. Kempf, “Mobility Architecture for the Global Internet,” Proc. MobiArch ’06, Dec. 2006, pp. 23–28. [12] H. Faithi and R. Prasad, “Mobility Management for VoIP in 3G Systems: Evaluation of Low-Latency Handoff Schemes,” IEEE Wireless Commun., vol. 12, no. 2, Apr. 2005, pp. 96–104. [13] Y. Han, J. Choi, and S. Hwang, “Reactive Handover Optimization in IPv6-Based Mobile Networks,” IEEE JSAC, vol. 24, no. 9, Sept. 2006, pp. 1758–72. [14] S. Thomson and T. Narten, “IPv6 Stateless Address Autoconfiguration,” IETF RFC 2462, Dec. 1998. [15] H. Soliman and G. Giaretta, “Interactions Between PMIPv6 and MIPv6: Scenarios and Related Issues,” IETF Internet draft, draft-giaretta-netlmm-mip-interactions- 00, Apr. 2007, work in progress. [16] T. Narten, E. Nordmark, and W. Simpson, “Neighbor Discovery for IP Version 6,” IETF RFC 2461, Dec. 1998. [17] N. Moore, “Optimistic Duplicate Address Detection (DAD) for IPv6,” IETF RFC 4429, Apr. 2006. BIOGRAPHIES KI-SIK KONG (kisik.kong@gmail.com) received his B.S., M.S. and Ph.D. degrees in computer science and engineering from Korea University in 1999, 2001, and 2005, respective￾ly. From 1999 to August 2005 he was a researcher in the Research Institute of Computer Information and Communi￾cation at Korea University. From September 2005 to August 2007 he was a research professor at Korea Univer￾sity and Ewha Womans University. Currently, he is a research professor in the Department of Computer Science and Engineering at Korea University. His research interests include IP mobility/QoS support, performance modeling, and optimization issues in next-generation wireless mobile networks. He was listed in Marquis Who’s Who in Science and Engineering (2006–2007, 2008–2009), Who’s Who in the World (2008), and Outstanding Scientists of the 21st Century (2007–2008), respectively. YOUN-HEE HAN [M] (yhhan@kut.ac.kr) received his B.S. degree in mathematics from Korea University in 1996. He received his M.S. and Ph.D. degrees in computer science and engineering from Korea University in 1998 and 2002, respectively. From March 4, 2002 to February 28, 2006 he was a senior researcher in the Communication and Net￾work Group of Samsung Advanced Institute of Technology. Since March 2, 2006 he has been a professor in the School of Internet-Media Engineering at Korea University of Tech￾nology and Education, CheonAn. His primary research interests include theory and application of mobile comput￾ing, including protocol design and performance analysis. Since 2002 his activities have focused on IPv6, IPv6 mobili￾ty, media-independent handover, and cross-layer optimiza￾tion for efficient mobility support in IEEE 802 wireless networks. He is a member of IEICE. He has also made sev￾eral contributions to IETF and IEEE standardization. Cur￾rently, he is chair of the IPv6 over WiBro working group of TTA IPv6 Project Group in Korea. MYUNG-KI SHIN (mkshin@etri.re.kr) is currently a senior researcher at the Protocol Engineering Center of the Elec￾tronics and Telecommunications Research Institute (ETRI), Korea. He is a technical leader of the Mobile Router project in ETRI. He has been working on IP protocols since 1994. His research interests include IPv6, Mobile IPv6, multicast, and future network technologies. He was also a guest researcher at the U.S. National Institute of Standards and Technology in 2004–2005. He is actively involved in IETF IP related WGs (IPv6, multicast, mobility). He is an author of several IETF RFCs (RFC 3338, RFC 4038, RFC 4489, etc.). He is also a member of the CTO Executive Committee of the IPv6 Forum. He received a Ph.D. degree in computer engi￾neering doing research on IPv6 multicast and mobility from Chungnam National University in 2003. HEUNG-RYEOL YOU (hryou@kt.com) received B.S., M.S., and Ph.D. degrees in electronic engineering from Yonsei Univer￾sity, Seoul, Korea, in 1985, 1987, and 2002, respectively. He has been a research engineer with Korea Telecom Authority (now KT), Seoul, Korea, since 1987 and is cur￾rently director of the Infra Laboratory, KT. His research interests are in the areas of mobility management, seam￾less mobility, wireless communication network and system design, and position location technologies. WONJUN LEE [SM] (wlee@korea.ac.kr) received B.S. and M.S. degrees in computer engineering from Seoul National Uni￾versity in 1989 and 1991, respectively, an M.S. in computer science from the University of Maryland, College Park in 1996, and a Ph.D. degree in computer science and engi￾neering from the University of Minnesota, Minneapolis in 1999. In 1998 he was a research associate at Stanford Research International (SRI), Menlo Park, California. In March 2002 he joined the faculty of Korea University, where he is currently an associate professor in the Depart￾ment of Computer Science and Engineering. He has pub￾lished over 45 journal papers with IEEE, Elsevier, and Springer-Verlag. His research interests include mobile com￾munications and protocol engineering applied to wireless systems. A confrontation has existed between the telecommunication and the Internet communities for a long time. However, PMIPv6 could be considered as a promising compromise between them. It is a practical derivative of MIPv6, rather than a new idea. KONG LAYOUT 4/9/08 11:03 AM Page 45