Study on PMIPV6-based Network Localized Mobility Management

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Abstract. In this paper, mobility management of network inter-domain handover is deeply studied, a new localized mobility management protocol (i.e. PMIPv6) is introduced, and also mobility management mechanism of inter-domain handover is analyzed. Then, F-PMIPv6, an optimized and network-based inter-domain mobility management method, is proposed, and also an analysis is made on its performance, proving that network handover delay can be effectively reduced by this method.

Key words:PMIPv6; Network Management; Handover Delay

1. Introduction

At present, studies on network-based mobility management are mainly concentrated on intra-domain handover delay. The basic framework that should be followed by network-based mobility management was proposed by foreign IETF as follows: localized mobility anchor (LMA) in backbone network is in charge of processing mobile node's routing information which is transferred by mobile access gateway (MAG) the mobile nodes belong to currently, and all packages sent to or out from mobile nodes should be via it. To inform motion to MAG, Mobile node only needs to own ordinary mobility functions (e.g. motion detection) but not to participate in mobility management. The network-based localized mobility management protocol is independent of any particular global mobility management protocol, but has nothing to do with the final link layer between mobile node and MAG. The concept of access domain is mainly introduced in localized mobility management protocol, in which access network is managed hierarchically. When accessing to service intra-domain for handover, mobile nodes only need to inform LMA and keep transparent to home agent (HA) and opposite-end communication node (CN). When accessing to service inter-domain for handover, mobile nodes only need to inform HA and CN with global mobility management protocol, or design new and highly-efficient inter-domain handover management method of localized mobility management.

2.PMIPv6 Protocol

PMIPv6 is a network-based localized mobility management solution, aiming at defining the simple extension of mobile IPv6, supporting the network-based mobility management of IPv6 host, and also reusing the signaling and features of mobile IPv6. A PMIP client is introduced in this method, sending proxy binding update message to LMA, and informing LMA of whether mobile node is handed over within LMA. In PMIPv6 protocol, mobile node is unnecessary to be with mobility support if it is handed over between different access points in the same localized mobility domain (LMD), but is necessary only if global mobility support is needed by it. That is, in global mobility support, mobile node has been assumed to acquire home address (HoA) necessarily from home agent (HA), but it is unnecessary to be with global mobility support in the localized mobility management of LMA domain. Therefore the protocol stack burden of mobile node can be reduced by such a localized mobility management. In the protocol, signaling related to IP mobility is not involved in mobile node; only home address is used by mobile node in communication; the care-of address/Proxy-c0A is invisible to mobile node. However, circuitous route defined in MIPv6 can be used for proxyMobileIpv6 protocol. The flow of PMIPv6 inter-domain handover management signaling is shown in figure 1.

Figure 1: Flow of PMIPv6 Intra-domain Handover Signal Management Signaling

2.1 Link Layer Handover

When mobile node arrives in NMAG, it will receive wireless signals that are sent from NMAG, and these signals include routing J plug information, thus mobile node can acquire prefix information the same to what the previous mobile access network sends.

2.2 Proxy Binding Update

PMAG sends proxy binding update signal to LMA, and informs LMA mobile node of requesting unbinding the Proxy-CoA of previous mobile access network and the MN-HoA of mobile node.

2.3 Proxy Binding Acknowledgement (PBA)

LMA sends PBA signal to PMAG, suggesting proxy binding update signal has been received.

2.4NMAG Sends Binding Registration Request Signal to LMA

NMAG (New Mobile Access Gateway) sends binding registration request signal to LMA, requesting binding MN-HNP of mobile node and Prox-CoA of NMAG.

2.5 LMA Sends Registration Response Signal to NMAG

LMA sends registration response signal to NMAG, suggesting proxy binding update signal has been received.

3.Improved Intra-domain Handover Management Method (F-PMIPv6)

Because the basic mobility management method of PMIPv6 sources from MIPv6, the over-large shortcoming of PMIPv6 in handover will affect the application of some delay. The focus of the study has been transformed to introducing fast handover idea to PMIPv6 protocol and making an optimization on the performances of PMIPv6, for the purpose of reducing packet loss caused by large handover delay in the motion of mobile terminal. The network-based localized mobility management method (F-PMIPv6) applies the fast handover idea of MIPv6 to PMIPv6 protocol in handover process and also improves it. Also, predictive mode is used for predicting MN handover through bottom interaction, and thus the addresses of local nodes and MAG are configured in advance, to complete the handover of three layers. In such a way, a preparation for the handover of three layers can be made before wireless radio link is disconnected, and hence network handover delay within domain. Simultaneously, packet caching is set in PMAG and NMAG: packet is cached in PMAG when the second layer is handed over. After the channel between PMAG and NMAG is established, packet begins to be cached; after the binding updates of MN and NMAG are complete, a channel for packet transfer between PMAG and NMAG is established. In such a way, handover speed is faster, and also packet loss can be reduced in handover process if packet caching is set in PMAG and NMAG.

In PMIPv6 protocol, only the handover management method of mobile terminal within the LMA domain is given: if moving radius of mobile terminal is enlarged to exceed management scope of the LMA, the communication of the mobile node will be interrupted if no global mobility management protocol stack is installed at mobile terminal at this moment. At present, studies on PMIPv6 localized mobility management is still concentrated on intra-domain handover management. Routing can be directly established between mobile node and opposite-end communication node, and then the home address (HoA) and care-of address (CoA) of mobile node can be bound. The binding is complete in the return routability procedure (RRP), and also is periodically updated when the IP connection of the mobile node is changed. The RRP comprises of hone Home Address Test (HoT) and Care-of Address Test (COT), mainly aiming at establishing a mutual trust mechanism between mobile node and its opposite-end communication node, and confirming the smooth channel between the two sides. Such a process can also increase signal transmission burden and handover delay. In PMIPv6 protocol, the RRP of MIPv6 continues to be used, and also the binding of mobile node and its opposite-end communication node needs to be complete with the help of RRP. Therefore, the mutual trust mechanism between communication nodes can be established. Also, in PMIPv6 protocol, the mobility of mobile node will be completely controlled by network side, and mobile node can inform MAG of its motion only with ordinary mobility features, but can't participate in network-layer mobility management. When MN and CN are terminals with no MIPv6 protocol stack installed, the position of CN accessing to network plays an important role in the performance of MN inter-domain handover.

It is assumed that mobile node (MN) and its opposite-end communication node (CN) are terminals with no MIPv6 protocol stack installed, and their mobility managements are completely controlled by MAG and also are within the range of PMIPv6 protocol. Also, it is assumed that the opposite-end CN is not handed over within the routing handover of the MN. In PMIPv6 protocol inter-domain handover management, mobile node can inform MAG of its motion only needing to own ordinary mobility features, but is unnecessary to participate in mobility management. PMIPv6 protocol is independent of any particular global mobility management protocol, but has nothing to do with the final link layer between mobile node and MAG. The concept of access domain is mainly introduced in localized mobility management protocol, in which access network is managed hierarchically.

4. Performance Analysis Results

From the above analysis, it can be known that F-PMIPv6 is much lower than PMIPv6 in handover delay. In PMIPv6 handover method, the connection between MN and PMAG begins to be disconnected when the second layer is handed over, and the handover formally ends until packet sent from NMAG is finally received. Therefore, such a period is the delay of PMIPv6 handover method. Figure 2 shows the comparison between F-PMIPv6 and PMIPv6.

Fig.2: Comparison between F-PMIPv6 and PMIPv6

In F-PMIPv6 (a network-based localized mobility management of intra-domain handover), the connection between MN and PMAG begins to be disconnected after FBA message is received by MN until packet sent by NMAG is received by MN. Therefore, a conclusion can be drawn up that the intra-domain motion handover delay of mobile nodes can be effectively shortened with the network-based localized mobility management of intra-domain handover proposed in this paper.

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