Implementation and analysis of proxy MIPv6

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1 WIRELESS COMMUNICATIONS AND MOBILE COMPUTING Wirel. Commun. Mob. Comput. 2011; 11: Published online 17 September 2009 in Wiley Online Library (wileyonlinelibrary.com)..842 SPECIAL ISSUE PAPER Implementation and analysis of proxy MIPv6 Jianfeng Guan, Huachun Zhou, Zhiwei Yan, Yajuan Qin and Hongke Zhang National Engineering Laboratory for Next Generation Internet Interconnection Devices, Beijing Jiaotong University, Beijing, , China ABSTRACT Mobile IPv6 (MIPv6) is a host-based mobility support specification which has been approved by the IETF as the standardized solution of global mobility management in IPv6 network for Mobile Node (MN). However, MIPv6 handover procedure results in a large handover delay. To improve its performance, some MIPv6 variants such as Fast Handover for MIPv6 (FMIPv6) and Hierarchical MIPv6 (HMIPv6) were proposed. However, they all require the MN to support the mobility management protocols which increase the difficulty of management and deployment. Recently, IETF NETLMM workgroup published the Proxy Mobile IPv6 (PMIPv6) which is a network-based localized mobility management to provide the mobility support for mobile host without the involvement of the mobility signaling. In this paper, we analyze the singling cost of PMIPv6 and implement it in our test-bed to evaluate its performance. The results show that the PMIPv6 has lower signaling cost and packet delivery cost, and it can improve the handover performance of UDP and TCP than the other mobility management protocols under low-delay networks, as for the wide area networks, it needs to introduce some mechanism like fast handover to further improve its performance. Copyright 2009 John Wiley & Sons, Ltd. KEYWORDS PMIPv6; implementation; handover; Mobile IPv6; FMIPv6; HMIPv6 * Correspondence Huachun Zhou, National Engineering Laboratory for Next Generation Internet Interconnection Devices, Beijing Jiaotong University, Beijing, , China. hchzhou@bjtu.edu.cn 1. INTRODUCTION With the development of wireless and mobile technologies, more devices can get the Internet service during the movement. In order to provide the continuous communication for mobile devices, several global mobility support protocols were proposed. Mobile IPv6 (MIPv6) [1] is designed to provide the mobility support for the Mobile Node (MN) away from the home network. MN configures a new IPv6 address which is called Care-of-Address (CoA) after attaching to the foreign networks. In order to maintain the on-going session, the MN has to use its Home Address (HoA) to communicate with the Correspond Node (CN). To provide this mechanism, MIPv6 extends the IPv6 specification to set up the binding between CoA and HoA. It uses the CoA to indicate the location of MN and uses the HoA to identify the MN. However, the handover delay of MIPv6 is so large that it is unacceptable for the real time applications. To reduce the handover delay, Fast Handover for MIPv6 (FMIPv6) [2] was proposed which is an extension of MIPv6 to provide the mobility support with the aid of the access routers. FMIPv6 configures the New CoA (NCoA) based on the link layer information in advance to shorten the handover delay, and it also sets up the tunnel between Previous AR (PAR) and New AR (NAR) to minimize the packet loss during the handover. Besides, Hierarchical MIPv6 (HMIPv6) [3] was proposed to eliminate the overhead of global handover signaling. HMIPv6 introduces Mobility Anchor Point (MAP) entity which performs the local HA function to hide the location of MN from the Home Agent (HA) and CN. As a result, the MN configures two addresses, the On-link CoA (LCoA) and Regional CoA (RCoA). When the MN moves within a MAP domain, it only registers its LCoA with the MAP, and when the MN moves among different MAP domains, it first registers its LCoA with the new MAP, and then registers its RCoA with the HA. FMIPv6 and HMIPv6 are two experimental mobility management protocols developed from the MIPv6, and they are also the host-based mobility support specifications and require the MN to implement the client function in the IPv6 stack which limits the deployment and management of mobility services. Recently, Proxy Mobile IPv6 (PMIPv6) [4] were proposed to provide the mobility support for the mobile Copyright 2009 John Wiley & Sons, Ltd. 477

2 Implementation and analysis of proxy mipv6 J. Guan et al. cost, and packet delivery cost. Section 5 evaluates the PMIPv6 in detail and gives the experimental results. Finally, Section 6 concludes this paper. 2. RELATED WORK 2.1. Mobile IPv6 Figure 1. Proxy Mobile IPv6 application scenario. hosts without host involvement in the signaling interaction. The PMIPv6 is a network-based mobility protocol and Figure 1 shows the typical PMIPv6 application scenario. The PMIPv6 extends the MIPv6 and introduces two important entities called Local Mobility Anchor (LMA) and the Mobile Access Gateway (MAG). The LMA performs the full HA functionality and maintains the MN s binding information, while the MAG performs the mobility management for the MNs and emulates the home network in a PMIPv6 domain. When a MN moves among the PMIPv6 domain, the MAG will create a PMIPv6 tunnel to transmit the packets for the MN. The endpoints of this tunnel are the LMA Address (LMAA) and Proxy-CoA. The MNs belong to the same LMA will share the PMIPv6 tunnel when they attach to the same MAG. Fu and Lei [5] evaluated the benefits of PMIPv6 by analytical method and compared it with other mobility support protocols. The results show that PMIPv6 may cause high handover latency when the LMA is far from the current MAG. Zhou et al. [6] proposed a fast handover scheme based on the FMIPv6 operation and IEEE link layer trigger mechanism to improve the PMIPv6. The analytical results show that the proposed scheme has lower handover latency than PMIPv6. Besides, Kong et al. [7] analyzed the handover latency of PMIPv6 and compared it with MIPv6 and its variants. The results show that the PMIPv6 has much lower handover latency than that of MIPv6 and HMIPv6, and has the lower the handover latency than that of FMIPv6 when the delay between MN and MAG is greater than the delay between MAG and LMA. Recently, Guan et al. [8] implemented the PMIPv6 and evaluated its performance in WLAN environment and some researches [9] also studied the empirical performance of PMIPv6. In this paper, we mainly analyze the signaling cost and UDP/TCP performance of PMIPv6 and compare it with other mobility support protocols based on our previous work. The rest of the paper is organized as follows. Section 2 describes the related work of various mobility support protocols. Section 3 describes our implementation of PMIPv6. Section 4 analyses the handover delay, signaling MIPv6 provides a general IP mobility support framework and uses the CoA and HoA to carry the location information and identifier information, respectively. When a MN leaves the home network and enters a foreign network, it configures the CoA at first by the stateless or stateful address configuration mechanism, and performs the movement detection during the address configuration procedure. After that, the MN sends the Binding Update (BU) message to register its CoA with the HA. The HA, after receiving the BU message, updates the binding cache and modifies the tunnel. And then, the HA replies with a Binding Acknowledge (BA) message. The MN updates the tunnel after receiving the BA message. If the CN supports the MIPv6, the MN should also set up the binding cache in the CN to realize the optimal routing. During the movement, the MN can maintain the session through the HA without rebuilding the connections. Lots of MIPv6 implementations were developed in the past few years. Santti et al. [10] survey the MIPv6 implementations under the Windows, FreeBSD and Linux platforms, and analyze their features. MIPv6 for Linux (MIPL) [11] which was developed by Helsinki University of Technology is a popular implementation under Linux operation system. Figure 2 shows the function architecture of MIPL2.0 implementation. The implementation divides into two parts, the user space part and the kernel space part. The user space part consists of dynamic HA address discovery module, routing optimization module, mobile prefix discovery module, return routability procedure, movement detection module, and the BU module. The kernel space implements the IPsec module, routing module and tunnel module, and generates the MIPv6 signaling messages including the Figure 2. The function block diagram of MIPL Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd.

3 J. Guan et al. Implementation and analysis of proxy mipv6 Figure 3. Predictive and reactive fast handover. mobility header and the new ICMPv6 types. The MIPv6 signaling messages use the socket to transmit the data between user space and kernel space. The IPsec module, routing module and neighbor list use the Netlink to communicate with the user space. The tunnel module uses the ioctl to transmit the data between user space and kernel space Fast Handover for Mobile IPv6 The FMIPv6 enables the MN to perform the address configuration procedure based on the link layer information when MN is still attached to the PAR, and it introduces the access routers to assist the mobility management. Figure 3 shows signaling interaction flow in FMIPv6 [2]. At first, the MN uses the specified link layer method to get the available access points information in advance. And then, the MN sends the Router Solicitation for Proxy Advertisement (RtSolPr) message to the PAR for resolving subnet routing information. The PAR, after receiving the RtSolPr message, replies with a Proxy Router Advertisement (PrRtAdv) message. The MN configures the NCoA based on the information included in the PrRtAdv message. And then the MN sends the Fast Binding Update (FBU) message including the NCoA to its PAR. The PAR sends the Handover Initiate (HI) message to the NAR and begins to buffer the packets once it receives the FBU message. The NAR, after receiving the HI message, performs the Duplicate Address Detection (DAD) procedure on behalf of the MN to check the validity of NCoA. After that, the NAR replies with the Handover Acknowledge (HAck) message to the PAR, and sets up a tunnel between the Previous CoA (PCoA) and the NCoA. The PAR, after receiving the HAck message, sends the Fast Binding Acknowledgement (FBack) message to the MN and the NAR. The PAR begins to tunnel the packets to the PCoA during the handover. The tunnel between PCoA and NCoA will be active until the MN Figure 4. The implementation architecture of FMIPv6. completes register procedure with the HA. The NAR buffers the packets until it receives the Fast Neighbor Advertisement (FNA) message. Once the MN attaches to the NAR, it sends the FNA message at first and begins to gets the buffered packets until it finishes the binding with the HA. The FMIPv6 has two operation modes shown in Figure 3. In the predictive mode, the MN sends the FBU message through the PAR link. In the reactive mode, the MN loses its attachment with PAR before sending the FBU message, so it has to send the FBU message to the PAR through the new link by encapsulating the FBU in the FNA message. Some FMIPv6 implementations have been developed. Albert CA et al. [12] implemented the FMIPv6 under the Linux platform ( kernel) based on the MIPL1.1, and their implementation consists of two parts, the fh-base module which runs into the kernel space and the fh-daemon module which is a user space daemon to perform the FMIPv6 operations. Afterwards, Ivov and Andre [13] implemented the FMIPv6 in WLAN networks based on the MIPL 2.0. Figure 4 shows the implementation architecture of FMIPv6. The kernel space modifies the network card driver to monitor the link layer signal strength and sends signal status reports to the FMIPv6 demon. The user-space runs the MIPv6 daemon and FMIPv6 daemon, and uses the process communication to perform the fast handover. The handover performance of FMIPv6 is mainly based on the link layer trigger technology, which is dependent on the specific link layer technologies Hierarchical MIPv6 The HMIPv6 extends the MIPv6 by introducing the MAP entity to hides the micro-mobility from the HA and CN, and it can reduce the signaling exchange and provides the location privacy. Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd. 479

4 Implementation and analysis of proxy mipv6 J. Guan et al. Figure 6. The double-process in the MN. Figure 5. HMIPv6 operation flow. Figure 5 shows the operation flow of HMIPv6. We assume that a HMIPv6-aware MN moves among the foreign networks. When the MN enters into a foreign network, it should check the MAP option after receiving the router advertisement (RA) messages. If the RA message does not contain the MAP options, it performs the MIPv6 handover, or else the MN has to register with at least one MAP. The MN sends the Local BU (LBU) message to the selected MAP to bind its current LCoA with the RCoA. During the movement, the MN has to detect whether it is in the same MAP domain. When the MN moves within the same MAP domain (intra-map handover), it only updates its binding in the MAP. Once the MN moves from one MAP domain to another MAP domain (inter-map handover), it has to send the BU message to register its RCoA with the HA after registering the new LCoA with the new MAP. The HMIPv6 maintains two tunnels, one is MN-MAP tunnel and the other is the MN-HA tunnel. To provide the smooth inter-map handover, the MN may send a BU message to the previous MAP to forward the packets between previous MAP and the new MAP. Daley [14] implemented the HMIPv6 based on the MIPL 0.9.4, and the HMIP implementation provides the full functional MAP hierarchy, dynamic configuration of MAP/MN tunnels, full basic HMIPv6 signaling, dynamic MAP propagation. Recently, we implemented the HMIPv6 in the WLAN according to the HMIPv6 specification, and our implementation is based on the MIPL2.0 and consists of the MN function and the MAP function. The implementation of MAP is similar to the HA in MIPL 2.0 since the MAP performs the local HA function. The MN function uses the double-process in the MN to register with HA and MAP, respectively. Figure 6 shows the double-process in the MN. The MN runs two processes (noted as MN MAP and MN HA) and communicates with the MAP and the HA. The MN MAP process performs the intra-map handover detection and inter-map handover detection, and the MN HA process detects the change of RCoA by listening to the named pipe set up by MN MAP.IfMNMAP detects the Intra-MAP handover, it only registers with the MAP and binds the LCoA to RCoA. Once the MN detects the inter-map handover, it firstly registers with the MAP and then it transmits the RCoA to the MN HA process through the named pipe to register the RCoA with the HA. 3. IMPLEMENTATION OF PMIPV Overview of PMIPv6 The PMIPv6 adopts the network-based manner to manage the mobility on behalf of the MNs, and introduces the LMA and the MAG to perform the mobility signaling which makes the MN independent of the mobility signaling. LMA supports the HA function of MIPv6 and extends the binding cache entry data structure which adds the new PMIPv6 flag, MN-identifier, interface identifier, link local address for each interface of MN, IPv6 home prefix, bi-directional tunnel interface identifier, the access technology and 64 bits timestamp. The LMA supports the Per-MN-Prefix model and it assigns the unique prefix for every MN in a PMIPv6 domain. When an MN has multiple network interfaces, the LMA assigns the different prefix for every interface. MAG typically acts as a default router on the access link for MN and it has three functions. Firstly, the MAG detects the MN s movements on the access link including the attachment event and the detachment event, and it initiates the PMIPv6 signaling interworking procedure with the LMA based on these events. Secondly, the MAG advertises the MN s Home Network Prefix (HNP) information to emulate the home link. Thirdly, MAG sets up the data path for the MN to transmit the packets. 480 Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd.

5 J. Guan et al. Implementation and analysis of proxy mipv6 Figure 7. The signaling flow of PMIPv6. Figure 8. Implementation modules in PMIPv6. Figure 7 shows the signaling flow of PMIPv6. Assume that a MN attaches to the P-MAG at first, and then attaches the N-MAG. The P-MAG, after detecting the attachment event, authorizes the MN for network-based mobility management service. To do so, the P-MAG acquires the MN-ID and the policy profile which is typical configured in an AAA server. After that, P-MAG sends the Proxy BU (PBU) message to the LMA of MN. Once receiving the PBU message, the LMA checks the PBU message and allocates the HNP for the MN. And then, the LMA creates the binding cache entry and sets up the tunnel to the P-MAG. After that, the LMA replies with a Proxy BA (PBA) message to the P-MAG. After receiving the PBA message, the P-MAG sets up the tunnel and routing state. To emulate the MN s home link, the P-MAG sends the RA message with the prefix information option(s) for the MN. MN may send the Router Solicitation (RS) message at any time after the attachment and there is no strict ordering relation with the other messages. The MN configures the IP address after receiving RA messages. When the MN leaves the P-MAG, the P-MAG detects the detachment event and releases the resource. Besides, P-MAG notifies the LMA to delete the binding cache. Once the MN attaches to the N-MAG, the N-MAG will perform the same signaling flow. As long as MN moves in the same PMIPv6 domain, it can use the same address configuration Implementation Our PMIPv6 implementation runs on the Linux kernel , which is based on the MIPL2.0. The current implementation covers the basic part of the PMIPv6. The PMIPv6 implementation includes the LMA, the MAG, and the AAA, and Figure 8 shows the PMIPv6 implementation framework. The modules in the MAG consist of MN detection modules, PBU/PBA process module, routing state update module, BU list maintenance module and the RA module. The MN detection module is used by the MAG to monitor the attachment and detachment evens through the link layer technologies (the implementation uses the syslog function). The PBU/PBA process module is used to generate and process the mobility signaling messages including the PBU and PBA. BU list maintenance module is used to set up and maintain the BU list in MAG. RA module is used by MAG to emulate the home link through sending the home link prefix from the LMA. The modules in the LMA consist of the PBU/PBA Process module which is similar to that of MAG, the routing state update module, BU cache maintenance module and HNP management module. The routing state update module is used to set up the tunneling between LMA and MAG. The BU cache maintenance module is used to record the BU in LMA. The HNP management is used to allocate the IPv6 prefixes for MNs belong to the PMIPv6 domain. Besides, the AAA module is used to authenticate the MN, while in our implementation, this module is implement in the MAG. The detailed operation flow of PMIPv6 is shown as follows: (1) At first, a MN attaches to the layer 2 equipment. In our implementation, we use the Cisco 1200 AP. (2) The layer 2 equipment detects the attachment events and notifies the MAG. (3) The MAG gets the layer 2 address of the MN from the notified message, and acquires the MN-Identifier and policy profile from the policy server. In our implementation, the profile is stored in the local store. (4) The MAG gets the MN-Identifier and AAA information. (5) The MAG sends the PBU message to the LMA. (6) The LMA performs the PBU/PBA module to maintain binding caches and update the routing states. After that, the LMA replies with a PBA message to the MAG. Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd. 481

6 Implementation and analysis of proxy mipv6 J. Guan et al. not perform the DAD process when MN within a PMIPv6 domain [18] and FMIPv6 performs the DAD in advance. T FMIP is the time interval between MN sending the FBU and receiving the FBack. T AA is the access authentication delay which is required by PMIPv6 to get the MN profile. T bind is the signaling proceed delay between the MAG and the LMA, while T SR is the routing setup delay. The handover delay of PMIPv6 consists of four parts. The first part is the layer 2 handover delay T L2. In WLAN, the layer 2 handover consists of the scanning procedure, the authentication and association procedure. The second part is the access authentication delay T AA which includes the MN attachment detection delay and the authentication messages delivery and processing delay. The third part is the binding delay T bind. The final part is the routing state updating delay T SR which includes the tunnel setup delay, the default router updating delay and the address configuration delay especially when a MN firstly attaches to a PMIPv6 domain Signaling Cost Analysis Figure 9. Handover procedure and signaling timing diagram. (7) The MAG performs the PBU/PBA module to maintain the BU list and routing state. (8) After finishing the registration with the LMA, the MAG advertises the HNP, and then the MN configures the address and communicates with the corresponding node. 4. PERFORMANCE ANALYSIS 4.1. Handover Delay Analysis Some previous studies have analyzed the handover latency of MIPv6, FMIPv6, and HMIPv6 [15, 16]. In this section, we mainly discuss the handover of PMIPv6. Figure 9 shows the handover procedure and signaling timing diagram of four schemes. Some notations in the figure are made as following. T L2 is the layer 2 (link layer) handover delay, and assuming that they has the same handover delay. T MD is the movement detection delay which means the layer 3 detection delay used by MIPv6 and HMIPv6, and it depends on the MinDelayBetweenRAs (minimal RA interval). The default value of MinDelayBetweenRAs is 3 s according to the MIPv6 specification. T DAD is the duplicated address detection delay which means the time interval between the movement detection completion and the completion of address configuration and DAD. T DAD is equal to RT DT imes, which RT is RetransTimer and the DT imes is the DupAddrDetectTransmits according to Reference [17]. Besides, PMIPv6 does Lee et al. [19] use the fluid flow model to analyze the cost of HMIPv6 and PMIPv6, while in this section we use the analysis model in Reference [20,21] to analyze the signaling cost (we mainly concern on the location update cost), and we use a four-layer domain model in wireless network to calculate the total number of subnet handover and domain handover, and compute the total signaling cost during one call. Figure 10 shows the four-layer domain model, and subnet at the center of the domain is called the layer 0, and the subnets which are enclosed by every dashed line form different layers, noted as layer 1, layer 2, and layer 3. Assume that a MN resides in a subnet for a period and moves to one of its four neighbors with the same probability equal to 1/4. We use the <x, y> to mark the different subnet, where x indicates that this subnet is in layer x, and y indicates the types of this subnet. The subnets at the symmetrical positions have same traffic flow pattern and same type. Figure 10. Four layer domain model. 482 Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd.

7 J. Guan et al. Implementation and analysis of proxy mipv6 in a call is E(N s ) = Kα s (K) (3) K=0 The probability that MN traverses K domains in a call is { 1 1 α d (K)= [1 f ω d (λ c)] K = 0 1 [1 f ω d (λ c)] 2 [fd (λ c)] K 1 K>0 (4) Figure 11. State transient diagram. In two-dimensional layered mesh random walk model, the number of layers in a domain is presented with n, the transient state (x, y) presents that MN is in the state <x, y>, and the state (n, 0) are absorbing state which presents that MN moves out of the domain from state (n-1, j), where 0 j n 1. In the random walk model we presented, the number of all states is S = (n 2 n)/2 + 2, where n 1. The transition matrix of this random walk model is S S matrix which could denoted with P = (p (x1,y1)(x2,y2) ) where p (x1,y1)(x2,y2) represents the probability that MN moves from state (x1, y1) to state (x2, y2) in one step. Figure 11 shows the state diagram of the random walk model for four-layer domain model and its state transition matrix is as follows: /4 0 1/4 1/ / /4 1/4 1/4 0 P = 0 1/ /4 1/ / / /4 1/ / /4 1/ / Let t s and t d denote the subnet residence time and domain residence time of MN, respectively. They are both independently and identically distributed random variables, and assume that f s (t) and f d (t) are the density function of t s and t d. Suppose that the subnet residence time and the domain residence time of the MN have exponentially distributed with parameter λ s and λ d, respectively. Furthermore, assume that the call hold time is the exponentially distributed with parameter λ c. Based on this model the probability that a MN traverses K subnets in a call time is shown as follows: { 1 1 ρ α s (K)= [1 f s (λ c)] K = 0 1 [1 f ρ s (λ c)] 2 [fs (λ c)] K 1 K>0 where f s (s) is the Laplace transform of f s(t), ρ = λ c /λ s which is called the Call-to-Mobility Ratio (CMR). Then the average number of subnet which the MN moves across (2) (1) where fd (s) is the Laplace transform of f d(t), ω = λ c /λ d. Then, the number of domain which MN moves across in a call is E(N d ) = Kα d (K) (5) K=0 We used the network model in Reference [19] to analyze the signaling cost during one call, and we do not consider the register procedure with the CN. The parameters used in the following analysis are shown in Table I. Note that when the MH boots up in the PMIPv6 domain, the LMA located in that domain acts as an HA. (1) The signaling cost for MIPv6 C MIPv6 = BU HA + E(N s ) BU HA (6) Table I. System parameters. Message Description Value RS RS message size 16 B RA RA message size 64 B RtSolPr Proxy RS message size nb PrRtAdv Proxy RA message size 104 B BU BU message size 72 B BA BA message size 40 B PBU Proxy BU message size 76 B PBA Proxy BA message size 52 B FBU Fast BU message size 72 B FBack Fast Back message size 32 B HI HI message size 72 B HAck HAck message size 32 B FNA Fast NA message size 24 B l The length of session packets 1 10 kb ω The ratio of packets on indirect path 0.2 The session tunneling weight cost 1.2 is the ratio of communication 0.3 start before entering to the MAP domain c Call hold time parameter 1/300 a Distance among MAP/LMA 15 b Distance between AR/MAG and 5 MAP/LMA c Distance between AR/MAG and 1.5 MN d Distance among AR/MAG 2 Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd. 483

8 Implementation and analysis of proxy mipv6 J. Guan et al. where BU HA = (RS + RA) c + (BU + BA) (b + c + a + b) (2) The signaling cost for HMIPv6 are decreased, and the PMIPv6 has the lower signaling cost than the others. C HMIPv6 = BU MAP + BU HA +E(N s ) BU MAP + E(N d ) BU HA (7) where BU MAP = (RS + RA) c + (BU + BA) (b + c) BU HA = (BU + BA) (b + c + a + b) (3) The signaling cost for FMIPv6 C FMIPv6 = BU HA + E(N s ) (FBU AR + BU HA ) where FBU AR = (RtSolPr + PrRtAdv+ FBU + FBack + FNA) c + (HI + HAck + FBack) d BU HA = (BU + BA) (b + c + a + b) (4) The signaling cost for PMIPv6 (8) 4.3. Packet Delivery Cost Analysis We analyze the packet delivery cost according to Reference [19] and assume that the CN sends the packets to the MN through the routing optimization path (direct path) and nonrouting optimization path (indirect path). In the analysis, the indirect packet ratio is defined as ω, σ is the session tunneling weight cost [22], and the μ is the ratio of communication start before entering to the domain. (1) The packet delivery cost of MIPv6 PC MIPv6 = ωlp nro ro MIPv6 + (1 ω)lpmipv6 (10) where P nro MIPv6 = (a + 2b + c) CN HA P ro MIPv6 = a + 2b + 2c CN MN (2) The packet delivery cost of HMIPv6 + σ(a + 2b + c) HA MN C PMIPv6 = PBU LMA + PBU HA + E(N s ) PBU LMA + E(N d ) PBU HA (9) where PBU LMA = (RS + RA) c + (PBU + PBA) b PBU HA = (BU + BA) (a + b + c) Figure 12 shows the singling cost under different Callto-Mobility Ratio. We can get that with the increase of the CMR, the signaling cost of four mobility support protocols PC HMIPv6 = μ(ωlp nro ro HMIPv6 + (1 ω)lphmipv6 ) + (1 μ)lp ro HMIPv6 (11) where P nro (a + 2b + c) + σ(a + b) + 2σ(b + c) CN HA HA MAP MAP MN P ro HMIPv6 HMIPv6 = = (a + b + c) CN MAP + σ(b + c) MAP MN (3) The packet delivery cost of FMIPv6 PC FMIPv6 = ωlp nro ro FMIPv6 + (1 ω)lpfmipv6 (12) where P nro (a + 2b + c) + σ(a + 2b) + 2σd + σc CN HA HA PAR PAR NAR NAR MN P ro FMIPv6 FMIPv6 = = (a + 2b + c) CN PAR + σd + c PAR NAR NAR MN (4) The packet delivery cost of PMIPv6 Figure 12. The signaling cost versus CMR. PC PMIPv6 = μ(ωlp nro ro PMIPv6 + (1 ω)lppmipv6 ) + (1 μ)lp ro PMIPv6 (13) 484 Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd.

9 J. Guan et al. Implementation and analysis of proxy mipv6 Table II. Implementations configuration. Configuration/IPv6 address Description MN Dell latitude D 500 HA/LMA BJTU wireless/mobile router AR1/AR2/AR3/MAP BJTU star 2600 Access point Cisco 1200 AP LMA/HA 2001:da8:205:60a::2/64 MAG1/AR1 2001:da8:205:60d::2/64 MAG2/AR2 2001:da8:205:60e::2/64 MAG3/AR3 2001:da8:205:60f::2/64 where P nro PMIPv6 P ro PMIPv6 Figure 13. The packet delivery cost. = (a + b + c) CN HA = (a + b + c) CN LMA + σa + 2σb HA LMA LMA MAG + σb + c LMA MAG MAG MN + σc MAG MN Figure 13 shows the packet delivery cost. We can get that the packet delivery cost increases with the length of the packets. PMIPv6 and HMIPv6 reduce packet delivery cost due to the reduced path length and tunnel overhead. As for FMIPv6, it enlarges the packet delivery cost because it induces the additional delivery cost between PAR and NAR. 5. PERFORMANCE EVALUATION 5.1. Experiment Setup We set up a test-bed to evaluate the performance of various mobility protocols. We use the MIPL 2.0 [11] and the fmipv6.org [13] to perform the MIPv6 and FMIPv6 handover, respectively. For the HMIPv6 implementation, we use our double-process based HMIPv6, and mainly test the intra-map handover performance. Figure 14 shows the experimental topology of our testbed. The LMA/HA uses the BJTU wireless and mobile router which supports MIPv6, FMIPv6, and HMIPv6. The MN is Dell 500 computer with Cisco 350 series wireless card. The MAG/AR is BJTU star 2600 series which support unicast and multicast routing protocols. Besides, MAG/AR attaches to Cisco Aironet 1200 series AP which supports IEEE b specifications. All the network entities in test-bed are running Linux operating system (Fedora Core 2). Table II shows the hardware configuration and IPv6 address configuration. To evaluate the performance in different environments, the MAP runs the NIST net [23] to emulate the wide area networks conditions. Since the NIST net only supports the IPv4, we use the IPv6-in-IPv4 tunnel to emulate an IPv6 network. We set up two test scenarios and test the performance of UDP and TCP during the handover. The first experimental scenario is a small topology which does not introduce additional delay. We test the round trip time between different entities by the PING6. Table III shows the round trip time in scenario 1. In the second scenario, the NIST net is used to introduce transmission delay among different entities, and Table IV shows the round trip time in scenario Experimental Results Handover Performance of PMIPv6. We use the PING6 to test the round trip time between the MN and the CN. The packet size of ICMPv6 is 64 byte, and the sending interval is 10 ms. Figure 15 shows the round trip time between the MN and the CN during the handover. Table III. The round trip time in scenario 1. Peer entities Round trip time (ms) Figure 14. Test-bed topology. Min Max Average Mdev MAG1-LMA MAG2-LMA MAG1-MAG MN-MAG MN-MAG LMA-CN Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd. 485

10 Implementation and analysis of proxy mipv6 J. Guan et al. Table IV. The round trip time in scenario 2. Peer entities Round trip time (ms) Min Max Average Mdev MAG1-LMA MAG2-LMA MAG1-MAG MN-MAG MN-MAG LMA-CN Figure 16. The PMIPv6 handover procedure in scenario 1. Figure 15. The round trip time in a PMIPv6 handover. Figure 15 (a) shows the round trip times in the scenario 1 and seven packets were lost during the handover. Figure 15 (b) shows the round trip times in the scenario 2 and 78 packets were lost. Figure 16 shows the handover procedure of the PMIPv6 in the scenario 1, and the total handover delay is s. The Cisco 1200 AP generates a syslog message to notify the MAG the attachment of MN after receiving the L2 association message. The MAG authenticates the MN and gets the policy profile from the local store. After that, the MAG sends the PBU message to the LMA to set up the tunnel between the MAG and the LMA. After receiving the PBU message, the LMA sets up the tunnel and replies with a PBA message to the MAG. The MAG, after receiving the PBA message, advertises the RA message with the HNP for the MN. After receiving the RA message, the MN configures the IPv6 address and communicates with CN. The access authentication delay in the scenario 1 is very short for the authentication is implemented in the local domain. And the binding delay is shortened for the round trip time between MAG and LMA is small according to the Table II. So, the total handover delay in the scenario 1 mainly consists of the layer 2 handover and the routing updating delay. Figure 17 shows the handover procedure in the scenario 2. The handover delay is about 1 second. The MN leaves the MAG1 at s, and attaches to the MAG2 at s. And then, the MN sends the PBU message at s. The LMA replies with a PBA message after receiving the PBU message. MAG2 receives the PBA message at s. After updating the routing state, the MAG2 sends the RA message. The MN configures the IPv6 address based on the HNP in the RA message. So, the total PMIPv6 handover delay is about 1 s. When the MN enters the PMIPv6 domain for the first time, the handover delay will be longer since it needs to configure the address. After that, and the MN move among a PMIPv6 domain, the handover delay will be lower than the first handover. We use the PING6 to test the handover delay of MIPv6, FMIPv6, HMIPv6, and PMIPv6, and Figure 18 shows the experimental results. The HMIPv6 delay is the intra-map handover delay, and the FMIPv6 delay is the proactive handover delay. As shown in the Figure 18 (a), the PMIPv6 has the lowest handover delay which is about 200 ms, and the MIPv6 has the largest handover delay, whereas FMIPv6 and HMIPv6 are in between. This is because that the PMIPv6 implementation performs the authentication procedure in MAG, and the default routing configuration does not change during the handover. So, we can conclude that the PMIPv6 can reduce the handover delay under the lower-delay net- Figure 17. The PMIPv6 handover procedure in scenario Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd.

11 J. Guan et al. Implementation and analysis of proxy mipv6 Figure 18. The handover delay in the experiments. Figure 20. The throughput of UDP experiment. works. Figure 18 (b) shows that the handover delay of FMIPv6 and PMIPv6 are much similar. This is because that the PMIPv6 binding delay increases with the network delay. And both of them are lower than MIPv6 and HMIPv6. Figure 19 shows the maximum, minimum, and mean handover delay of four mobility management protocols. The experimental results show that the PMIPv6 can reduce the handover delay and improve the handover performance than the other mobility support protocols. However, the handover delay of PMIPv6 increases with the increase of the transmission delay compared with that of other mobility support specifications Comparison of UDP Performance. We test the UDP performance during the handover. The CN sends 1000 byte UDP packets during the 40 s to the MN, and the total number of UDP during that period is Figure 20 shows one experiment result. We can get that during the handover, the MIPv6 and HMIPv6 will suffer from large throughput deterioration, while the performance of PMIPv6 and FMIPv6 is smoother. Figure 21 shows the packet loss during the handover of nine experiments for each mobility protocol. As shown in Figure 21 (a), the FMIPv6 has smallest packet loss for it uses the PAR and NAR to buffer the packets during the handover, and the packet loss of the PMIPv6 is little larger than the FMIPv6, but much smaller than MIPv6 and HMIPv6. In the scenario 2 as shown in Figure 21 (b), with the transmission delay increased, and the packet loss of each mobility specification also increased, but the PMIPv6 still has lower packet loss than that of MIPv6 and HMIPv6. Besides, the packet loss of PMIPv6 is similar to FMIPv6. Figure 22 shows the throughput of UDP of nine experiments under the scenario 1 and scenario 2. We can see that the throughput of UDP in two scenarios is similar and the throughput of PMIPv6 and FMIPv6 is much more than that of MIPv6 and HMIPv6. Figure 19. The maximum, mean, and minimum handover delay. Figure 21. The packet loss of UDP. Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd. 487

12 Implementation and analysis of proxy mipv6 J. Guan et al. Figure 24. The experiment results of TCP. Figure 22. The throughput of UDP Comparison of TCP Performance. Figure 23 shows the time-sequence graph of TCP. During the handover, the packet was lost, and there are some broken sections in the curves. The disruption time of TCP is dependent on the layer 2, layer 3 handover delay, and RTO delay. Since the four schemes use the WLAN technology, the layer 3 handover delay and RTO delay are different. The RTT is small in the scenario 1, and the initial RTO is small, hence there will be a number of retransmissions during the handover. If the layer 3 handover delay is larger than initial RTO, the RTO will be doubled. So, we can conclude that the TCP performance of PMIPv6 is better than MIPv6, HMIPv6, and FMIPv6 in scenario 1. In scenario 2 the RTT is large, and the initial RTO is big and hence less retransmissions occurs. As a result, the MN cannot get the packet if the RTO is timeout before the handover finished. So, we can get that in scenario 2 the TCP performance of PMIPv6 degraded, whereas the FMIPv6 has the best TCP performance. This is because that the FMIPv6 uses the short tunnel between PAR and PAR to transmit the packets. Figure 24 shows the TCP throughout of nine experiments. The TCP performance degraded with the increase of the transmission delay. And the throughput will decrease by about 80%. The reason is that the TCP throughput mainly depends on the arrival rate of the ACK. When the RTT is small (scenario 1), ACK arrives quickly and data is sent at a higher rate. Hence, throughput is high for small RTT, and decreases for large RTT. Besides, we can get that the experimental results are unstable due to the packet loss caused by the wireless link error and handover delay. The above experimental results show that the PMIPv6 can reduce the handover delay and packet loss under the low-delay networks. However, when the network delay increases, the packet loss will increase and the performance of TCP will degrade. To further improve the performance of PMIPv6, the PMIPv6 need add some fast handover mechanism like the FMIPv6 to reduce the packet loss during the handover. 6. CONCLUSIONS In this paper, we analyze signaling cost and packet delivery cost of PMIPv6 and implement it in our test-bed. The analysis results show that the PMIPv6 has lower signaling cost and packet delivery cost than other mobility management protocols. And the experimental results show that the PMIPv6 can reduce the handover delay and packet loss. Future work on the PMIPv6 is to implement the fast handover on PMIPv6 to reduce the packet loss during the handover and further improve its performance. ACKNOWLEDGEMENTS Figure 23. The handover performance of TCP. This paper is supported in part by the National Natural Science Foundation of China under Grant No , , and in part by the National Basic Research Program of China ( 973 program ) under contract No. 2007CB and No. 2007CB Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd.

13 J. Guan et al. Implementation and analysis of proxy mipv6 REFERENCES 1. Johnson D, Perkins C, Arkko J. Mobility Support in IPv6, RFC3775, Koodli R, Gopal D, Karim EM, et al. Fast Handover for Mobile IPv6, RFC4068, Soliman H, Castelluccia C, Malki KE, Bellier L. Hierarchical Mobile IPv6 Management (HMIPv6), RFC 4140, Gundavelli S, leung K, Devarapalli V, Chowdhury K, Patil B. Proxy Mobile IPv6, RFC5213, Fu XM, Lei J. Evaluating the Benefits of Introducing PMIPv6 for Localized Mobility Management, Technical Report No. IFI-TB , Institute of Computer Science, University of Goettingen, Germany, Zhou HC, Zhang HK, Qin YJ. A fast handover scheme of PMIPv6 and performance analysis. Journal of Internet Technology 2007; 8(4): Kong KS, Lee W, Han YH, et al. Handover latency analysis of a network-based localized mobility management protocol. IEEE ICC 2008; Guan JF, Zhou HC, Xiao WS, et al. Implementation and Analysis of Network-based Mobility Management Protocol in WLAN Environment, Mobility Conference 2008, MobiWorld Workshop Hyeon SL, Han YH, Lee HB, Choi HY. Empirical Performance Evaluation of IETF Mobile IPv6 and Proxy Mobile IPv6, Mobility Conference 2008, MobiWorld Workshop, Santti K, Auvray S, Egeland G. Survey of Mobile IPv6 Implementations FreeBSD and Linux, DOI=www. eurescom.de/public-web-deliverables/p1100-series/ P1113/D1/ pdfs/pir41/41 mip.pdf Helsinki University of Technology, MIPL - Mobile IPv6 for Linux, DOI=mobile-ipv6.org 12. Albert CA, Jose NM, Hector JB, et al. Evaluation of the Fast Handover Implementation for Mobile IPv6 in a Real Test bed, IPOM 2005, LNCS ; Ivov E, Andre M. The FMIPv6 Open Source Implementation Suite, DOI= Daley G. Hierarchical Mobile IPv6 Research at CTIE, DOI= 6features Fu SJ, Atiquzzaman M. Handover latency comparison of SIGMA, FMIPv6, HMIPv6 and FHMIPv6. IEEE GLOBECOM, 2005; 6: Haseeb S, Ismail AF. Handoff Latency Analysis of Mobile IPv6 Protocol Variations, Computer Communications, Vol ; Han Y, Choi J, Hwang S. Reactive handover optimization in IPv6-based mobile networks. IEEE JSAC 2006; 24(9): Kong KS, Lee WJ, Han YH, Shin MK, You HR. Mobility management for all-ip Mobile Networks: Mobile IPv6 vs. Proxy Mobile IPv6 [J]. IEEE Wireless Communications (Special Issue on Architectures and Protocols for Mobility Management in All-IP Mobile Networks), 2008; 15(2): Lee JH, Chung TM, Gundavelli S. A comparative signaling cost analysis of Hierarchical Mobile IPv6 and Proxy Mobile IPv6, IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 08), September 2008; Akyildiz IF, Lin YB, Lai WR, Chen, RJ. A new random walk model for PCS networks. IEEE Journal on Selected Areas in Communications (JASC) 2000; 18(7): Lin YB. Reducing location update cost in a PCS network. ACM/Baltzer Wireless Network 1997; 5(1): Han Y-H, Hwang S-H. Care-of address provisioning for efficient IPv6 mobility support. Computer Communications 2006; 29(9): Carson M, Santay D. NIST Net Network Emulator, DOI=snad.ncsl.nist.gov/itg/ nistnet AUTHORS BIOGRAPHIES Jianfeng Guan received his B.S. degree from Northeastern University of China in He is working toward the Ph.D. degree at Beijing Jiaotong University, where his main research interests focus around mobile IP, mobile multicast, and next generation Internet. Huachun Zhou received his B.S. degree from People s Police Officer University of China in 1986, and the M.S. and Ph.D. degree from Beijing Jiaotong University of China in 1989 and 2008, respectively. He is currently an assistant professor with the Institute of Electronic Information Engineering, Beijing Jiaotong University of China. His main research interests are in the area of mobility management, mobile and secure computing, routing protocols, network management technologies and database applications. Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd. 489

14 Implementation and analysis of proxy mipv6 J. Guan et al. Zhiwei Yan received his B.S. degree form TaiYuan University of Technology in He is working toward the Ph.D. degree at Beijing Jiaotong University. His main research interests focus around mobility management and next generation Internet technologies. Yajuan Qin received her B.S. and M.S. degrees from the University of Electronic Science and Technology of China (formerly known as Chengdu Institute of Radio Engineering) in 1985 and 1988, respectively, and Ph.D. degree in communication engineering from Beijing University of Posts and Telecommunications in Her research interests are in the areas of computer networks and wireless communications. Hongke Zhang received his M.S. and Ph.D. degrees in Electrical and Communication Systems from the University of Electronic Science and Technology of China (formerly known as Chengdu Institute of Radio Engineering) in 1988 and 1992, respectively. From September 1992 to June 1994, he was a post-doc research associate at Beijing Jiaotong University (formerly known as Northern Jiaotong University). In July 1994, he jointed Beijing Jiaotong University, where he is a professor. He has published more than 100 research papers in the areas of communications, computer networks, and information theory. He is the author of eight books written in Chinese and the holder of more than 30 patents. Dr Zhang received the Zan Tianyou Science and Technology improvement award in 2001, the Mao Yisheng Science and Technology improvement award in 2003, the first class Science and Technology improvement Award of the Beijing government in 2005, and other various awards. He is now the Chief Scientist of a National Basic Research Program ( 973 program). 490 Wirel. Commun. Mob. Comput. 2011; 11: John Wiley & Sons, Ltd.