Enhancement Fast Handover Mechanism by ...

Reduce delay in FMIPv6 using IEEE 802.21

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Enhancement Fast Handover Mechanism by Reducing Handover Latency Using 802.21 MIH Service in FMIPv6

Abdulkader Omar Alwer Esper Naseem Ibrahim

Electronic and Electrical Department Mechanechal and Electricty Faculty Alba'ath University Homs, Syria Phone No# Abdulkader 00963 932 077579

Febreuary 2010


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Abstract An important element estimating a good seamless handover scheme is that how rapidly and accurately can anticipate the imminent Layer 3 handover. The Fast Handovers for Mobile IPv6 (FMIPv6) may be the best scheme for it because the anticipation is made by collaboration with Layer 2. The emerging IEEE802.21 standard defines Media Independent Handover Functions (MIHF) that assist mobile nodes to seamlessly roam across heterogeneous access networks. The aim of this paper is to present a mechanism which uses existing IEEE802.21 MIH services to optimize the FMIPv6 procedure and define new MIH primitives to support this procedure. In our proposed we let that each AR (Access Router) maintains a CoA (Care of Address) table and generates the new CoA from nAR then it passes this NCoA to the MN using IEEE802.21 MIH primitives before starting handover .So, The proposed scheme is depending on implementing DAD process in nAR instead of MN comparing with existing Fast Handover scheme. When NCoA arrives to MN, the binding updates to home agent and correspondent node will be performed before starting L2 handover .From the evaluation results, we can see that the proposed fast handover scheme can achieve low handover latency comparing with existing FMIPv6 scheme . In addition, with the proposed scheme, we can design the network costeffectively by reducing coverage overlap between adjacent cells because the handover initiation time in the FMIPv6 is decreased. Keywords: Mobile IPv6, fast handover, seamless handover, Mobility, IEEE802.21 MIH.

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‫‪Reduce delay in FMIPv6 using IEEE 802.21‬‬

‫تقنية لتعزيز التسليم السريع عن طريق انقاص زمن التأخير باستخدام خدمة ‪802.21 MIH‬‬ ‫في بروتوكول االنترنت اإلصدار السادس المتنقل‬ ‫م‪.‬عبد القادر عمر الور‬

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‫أ‪.‬د‪.‬م‪.‬إسبر نسيم إبراهيم‬

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‫قسم الهندسة االلكترونية واالتصاالت – كلية الهندسة الميكانيكية والكهربائية – جامعة البعث‬ ‫حمص ‪ ,‬سوريا‬ ‫ملخص‬

‫تعنربربع لية ربربل توق رب ربربيق و ل ي ربلت توق ربت حربربيلع لية ربربل تيربربة م لةربربا طيربربتول ثة ربربل ربربل ط رب وربربم‬ ‫عن صل ألس س ل يف تصي م جل ي ألي نظ م تية م سةس تن رب ل ربا تعتربع وللتولربو النرتنربت صصربي ا يرب‬ ‫دلتن رب ذي تيربربة م ي ربلت ‪ FMIPv6‬ط رب ل رب علتولربربوالع ي ليربربه دل رب وربربان تصربربي م لربربو توق رب يف لية ربربل‬ ‫تيربربة م دلربربالوان لربربيع و تع رب ل ط رب ول ثة تربربل ربربل ل ن ربربل لس رب لي ر ربربوا طع رب ا ‪- IEEE802.21‬ل ربرباي‬ ‫لربربلف ط رب تعلف و سربربم لر رب م تي ربربة م دليربربت وس رب ‪ - MIH‬ع ربربي دلتةلل ربربل ‪ MN‬ط رب تن رب يربربةس ط رب ول‬ ‫شةك ع دلختةفل ت ربيف وربا ةةربىل تق ت ربيي ربه يتربيد تيربتخيم تو ورب ‪ IEEE802.21‬حل ربل تارب لل تق‬ ‫تعلترب تو ورب يتربربيد ةييرب ليد يف لية ربل تن رب يةيرب ةع ربربي دلتةللربل ربربت تيربربتخيم وللتولربربو ‪ FMIPv6‬مت يف‬ ‫وربربان دل ربربل قربربرت نظ رب م تيربربة م سربلت طع رب علتولربربو ‪, FMIPv6‬ح ربربىل لرتاربربن يف وربربا نظ رب م دل ربربرت ل رب ا ط رب‬ ‫طربربو ي وصربربو ‪ AR‬حيربربتفجب وربربيل لنرب لت الوتيرب م ‪ CoA‬ل طرب ت ربربوم طو ربربه وصربربو جليتربربي ‪ nAR‬وتو ربربي‬ ‫لنو الوتي م جليتي لط ت وم وعية ل ختة ا لحي ن ل عنو ‪ DAD‬يف طو ه وصو جليتربي لطرب تربتم رلتربل‬ ‫ربل خربلل لحرب لصربو عنربو‬ ‫وا عنو جليتربي تق ع ربيد دلتةللربل و سربتخي م تو ورب ‪ , IEEE802.21‬لطرب‬ ‫‪ NCoA‬ةع يد دلتةللل تتم تاس ليتىل طص قل عنو جليتي تق ول رب لةربي ل ع ربيد دلي لةربل ‪,‬ح ربىل لربيع‬ ‫لةت عية تل ( اس عنو ل دلص قل ) قة ةيء وعية ل تية م لةا طيتول ثة ل ن ل‬ ‫نت جل اسل ء وا نظ م دل رت ر لع نت مج وا نظ م ميكنربه تربي ي تق ت ة رب طرب ترب خر‬ ‫رب طم ط انربربل ط رب نظ رب م حل رب ي ‪ ,‬تا رب لل تق ذ ربربا ل رب نظ رب م دل ربربرت ت رب ميكنربربه ط رب ل ربربو تصربربي م لع رب تكةفربربه‬ ‫تربربيخ يف طنث ربربل ت ث ربربل ط رب ول خل ت رب دلتج رب لان نت ج ربل الخنف رب م ط رب تة ربربر عية ربربل‬ ‫ةشربربةكل ل رب إلتربربو تن رب‬ ‫تية م يف نيوذج دل رت دليتخيم علتولو ‪FMIPv6‬‬ ‫الكلمات الدالة‪ :‬وللتولو ‪ MIPv6‬دلتن ‪ ,‬تية م يربلت ‪ ,‬نظرب م تيربة م يربةس‪ ,‬تن رب ‪IEEE802.21 ,‬‬ ‫‪MIH‬‬

‫‪ 1‬طالب دكتوراه في كلية الهندسة الميكانيكية والكهربائية‪ ,‬جامعة البعث‪ ,‬حمص‪ ,‬سوريا‪.‬‬ ‫‪ 2‬أستاذ في كلية الهندسة الميكانيكية والكهربائية‪ ,‬جامعة البعث‪ ,‬حمص‪ ,‬سوريا‪.‬‬


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INTRODUCTION The handover latency of the MIPv6(Mobile IPv6) (Kwon & Kim & Bae & Suh ,2005) is the major factor degrading overall performance of the wireless and mobile networks. Thus, most previous efforts for the enhancement of MIPv6 have focused on minimizing the handover latency (Perkins ,2002)(Soliman ,2004). We know that there are two kinds of handovers, L3 (Layer 3) and L2 (Layer 2), for the subnet changing of the MN (Mobile Node). Actually, providing node mobility is a role of the L2 because the continuous link connection is provided by it. Some wireless networks, such as WLAN, could not support full mobility but some other latest wireless networks, such as WiBro/WiMAX and HSDPA, are going to support or already support the full mobility. This means that average performance of the MIPv6 will be depend on the performance of the L3 handover in the near future. So, a new L3 handover scheme which has less latency and efficiently supports the QoS-related services is crucial. Moreover, since providing a vertical handover between heterogeneous wireless networks is being a hot issue, supporting the seamless vertical handover on L3 is also recommended. The handover process of the MIPv6 consists of four steps: movement detection, CoA (Care-of-Address) formulation, DAD (Duplicated Address Detection) and binding-update (Soliman & Castelluccia, & El Malki & Bellier , 2005). The movement detection and DAD generate most latency of the L3 handover among these four steps (Soliman et al. , 2005). It implies that the average performance of the L3 handover can dramatically increase if the latency for the movement detection and DAD are minimized. Several previous efforts to enhance the MIPv6 show that the latency which is generated by the movement detection or DAD could be minimized with the “Fast router advertisement (Soliman ,2004)” and “optimistic DAD (Daley & Pentland & Nelson,2003)”. However, the key concept of these two schemes is to ignore the protocol recommendation of the standard IPv6. In order to deploy these two enhancements on the MIPv6-based wireless networks, we should slightly modify the standard protocol of IPv6. Since the design principle of the MIP is that modifying of already existing protocols for IP mobility should be minimized, modifying of the standard IPv6 may not be best approach. Moreover, it could involve some risks that unexpected side effects are emerged. HMIPv6 (Hierarchical MIPv6) (Liebsch & Singh & Chaskar & Funato ,& Shim,2005) is a pretty good handover scheme that was standardized by IETF. It can reduce average latency by localization of binding-update path. A new entity called MAP (Mobility Anchor Point) is introduced in the HMIPv6. The MAP is a router which is located in a


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visiting network of the MN. When an MN has changed its attachment point to a new subnet, the MN executes local binding-update with the local MAP if the changed subnet belongs to the same MAP. Despite the advantage which can reduce the average latency of binding-update, the HMIPv6 has a defect that could not always guarantee the minimized latency in all cases. Another pretty good scheme is the FMIPv6 (Fast handover for MIPv6) ( Koodli ,2008) . The anticipation ability about imminent L3 handover and fast binding-update feature are the key concepts of the FMIPv6. Nowadays, real-time services such as VoIP, IPTV and on-line conferencing strongly recommend to be guaranteed the QoS (Quality of Service) in the Internet. Thus, the FMIPv6 seems more suitable to the real-time services than HMIPv6 because it can provide an uninterrupted L3 handover. For the seamless handover of FMIPv6, the MN should exchange control messages with current AR (Access Router) before the L2 handover during a very short period (Moore ,2005). In some cases, it might be an overhead because all L2 notifications related to the fast handover do not always imply the L3 handover is actually imminent. In a mobile environment, synchronizing the L3 fast handover to the L2 notifications requires quite complicate decision making process because of the properties of wireless radio signals. Most schemes based on handover anticipation such as the FMIPv6 have a little probability to make an erroneous decision in spite of their higher implementation cost. To deploy the FMIPv6 in all IP networks, it is important to provide uniform interface to interact with various L2 implementations. Fortunately, IEEE802.21 MIH (Media Independent Handover) standard can be used to provide this uniform interface for the FMIPv6. The IEEE802.21 MIH has been introduced as a standard track of IEEE in order to support the vertical handover. MIES (Media Independent Event Service) which is one of MIH services can be used to fast handover. In this paper, a new fast handover mode will be proposed. It was designed to decrease handover by sending the MN its EUI 64 to new AR to configure NCoA in new domain ( prefix from nAR with EUI 64 from MN) so DAD process can be performed in nAR .After that the information about the new access point and the associated NCoA information from new domain to the MN will be distributed using IEEE802.21 primitives since the MN is still connected to its current subnet (current domain) before moving MN to new domain. This procedure implements by propose new MIH primitives to process this operation. After that binding updates operation to HA/CN will be performed when MN still in current domain before starting handover on


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L2 .This process aims to reduce the registration latency for the binding updates process. The rest of this paper is organized as follows. The existing MIPv6 and FMIPv6 will be explained in section 2 ( relates works) . The Media Independents Handover Function will be described in details in section 3.Section 4 will explain the our proposed FMIPv6 and the result of analysis will be described in section 5. Then, conclusion will be made in section 6. RELATED WORK Handover Latency in MIPv6 The MIPv6 supports handover that changes its point of attachment to the network when a MN moves to a new IP subnet. The basic handover procedure for the MIP consists of two components, L2 handover and L3 handover. The term L2 handover denotes its support for roaming at the link layer level, while the L3 handover occurs at the network layer level. Usually, the L3 handover is independent of the L2 handover, although it must precede the L3 handover. In Figure 1, the MIPv6 handover procedure is illustrated. The MIPv6 consists of three operations. These operations may overlap each another. Movement detection which includes L2 handover is a prerequisite procedure for other handover operation. L2 handover that must precede the L3 handover performs channel scanning, authentication, association. After L2 handover, MN can detect movement to a new IP subnet by the operation of movement detection. In the base MIPv6 specification, during the movement detection, MN performs the unreachability detection and then is accomplished through finding a new and different AR available. Router discovery is achieved through the reception of a router advertisement (RA) sent from the new AR (nAR). The RA message contains the information of a router such as its prefix, link layer address (MAC), MTU, and so on. The MN must configure a new IPv6 address to be used on the new network in CoA configuration procedure. This will be the MN’s new CoA (NCoA). The uniqueness of the configured addresses must be verified on the new link according to the DAD operation. Once the MN has detected that it has moved to a new network, it obtained a new CoA that and has been granted during the access to the new network. Then MN must perform the Binding Update operation by informing its Home Agents (HAs) and Correspondent Nodes (CNs) of its new location, thus new CoA. The total handover latency in the MIPv6 can be expressed as a sum of L2 handover latency and L3 handover latency. L2 handover latency is


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about 100 to 300 ms. And L3 handover is about 2,000 to 3,000 ms. This handover latency is so long that MN suffer from packet loss and service disruption.

Figure 1: Mechanism of FMIPv6 Protocol (Johnson et at., 2003) Fast Handover For Mobile IPv6 The FMIPv6 ( Koodli ,2008) addresses the following problem of handover latency reduction: how to allow the MN to send packets as soon as it detects a new subnet link, and how to deliver packets to a mobile node as soon as its attachment is detected by the new access router (Liebsch et al.,2005)(Moore ,2005). In the FMIPv6, the MN is informed of new AR’s advertised prefix and validates the duplication of NCoA on the new link prior to the MN’s movement. So, the MN is already configured with NCoA before it is attached to the new link. In other words, the FMIPv6 is designed to eliminate the delays associated with movement detection and CoA testing, the time introduced by the CoA configuration procedure. The FMIPv6 is designed to allow MN to anticipate in its IP layer mobility. Link layer triggers are required for anticipation and handover initiation. They are delivered to network layer modules as events for reporting changes in respect to the link and physical layer conditions. In Table 1, link layer triggers for the FMIPv6 are described. Figure 2 depicts the predictive FMIPv6 procedure utilizing the link layer triggers in Table 1. However, the FMIPv6 protocol has several problems such as the followings:  AR may have the protocol to exchange information about their neighbors for constructing the mapping table between AP’s MAC addresses and their corresponding AR. But it is not defined in the IETF.  Link layer triggers should be specified by the standards organizations such as the IETF and IEEE.

Reduce delay in FMIPv6 using IEEE 802.21 

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During the handover initiation, the MN could lose its connectivity to the oAR due to a sudden degradation in the link. The MN processes normal handover in the MIPv6 or the reactive FMIPv6. Therefore, the handover latency increases.

Table 1: Link layer triggers for the FMIPv6 Description This trigger may be used to get a list of available link list link by AP scan. This trigger specifies that a new available link is Link available detected A link down event will be fired in the near link going future, so the network layer must initiate the down handover procedure This indicates that the link cannot be used for link down data transmission any more This is provided to L3 when a new link is link up connected Primitive

Figure 2: The FMIPv6 procedure using MIH primitives


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Handover Latency in The FMIPv6 The FMIPv6 has the handover initiation time to perform the CoA configuration prior to the L2 handover. After the L2 handover, the MN transmits an UNA to inform the nAR of its presence and performs the procedure of binding update. Therefore, the FMIPv6 can reduce the total handover latency by pre-configuring the CoA in the handover initiation phase.

Where : DL2 DDAD DRD DPrRD DBU DFMIP DL3-L2 DMN-nAR

Layer 2 Handover Delay Delay for DAD Delay for Router Discovery Delay for Proxy Router Discovery Delay for Binding Update procedure including RR procedure Time needed for FMIP operation to complete Time needed from completion of FMIP operation to start L2 Handover Time needed for UNA reach nAR

Figure 3: Handover Latency in the MIPv6 and the FMIPv6 ( Koodli ,2008) Previous Researches Since IEEE802.21 has appeared recently so ,many researchers focus on impleminting it on the development process of their researches. (Mussabbir & Yao , 2006) propsed a mechnism of using MIH function with FMIPv6 by collecting information of L2 and L3 and sends it back to MN,but in this mechnism L3 information is network prefix so, MN must compine it with its EUI-64 to get IPv6 in new network that MN should move to it according to the Handove measurement.In this propsed still has the main problem in FMIPv6 which is DAD time and to verfiy of uniqueness of this address before using it and this propsed study should use an external compnent (IS) which is not preferred especially in working networks,furthmore it forms an extra cost. Another paper (Tran-Trong & Tursunova & Kim , 2008) introduced new idea to deal with DAD problem that (Mussabbir & et at. , 2006) doesn't resolve it ,The sloution fouced on generate randomaly each AR


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that participate in HO proccess and store it in its Cache to provide to MN when move to new subnet and perdically it make Passive listen to other AR to verify of uniqueness of addresses in its cache. This method has many problems related to periodically updates between AR and may important update (which has duplicated Address Detection information) has not received or delayed ,so NAR will provide a wrong address to MN , so this thing may be drive to security problem from one side .From another side, the Back from HA to MN may be sent to another MN. Another problem in this proposed is BU process will be happen like current FMIPv6 procedure , so the BU delay time not resolved also. MEDIA INDEPENDENT HANDOVER FUNCTION In the mobility management protocol stack of both mobile node and network element, the Media Independent Handover Function (MIHF) is logically defined as a shim layer between the L2 data link layer and L3 network layer (Johnson & Perkins & Arkko , 2003). The upper layers are provided services by the MIH function through a unified interface. The services exposed by the unified interface are independent of access technologies. This unified interface is known as Service Access Point (SAP). The lower layer protocols communicate with the MIHF via media dependent SAP as shown in figure 4 below. MIHF defines three main services that facilitate handovers between heterogeneous networks: Media Independent Event Service (MIES), Media Independent Command Service (MICS) and Media Independent Information Service (MIIS). Detailed discussions of each of the services are given below. Media Independent Event Service (MIES) Media Independent Event Services (MIES) provide event reporting, event filtering and event classification corresponding to the dynamic changes in link characteristics, link quality and link status. The MIES report both local and remote events to the upper layers. The upper layers perform registration to receive events from the MIHF using a request/ response primitive. Some of the events that have been specified by IEEE 802.21 are “Link Up”, “Link Down”, “Link Detect”,” “Link Parameter Reports” and “Link Going Down”


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Figure 4: Media Independent Handover Function Media Independent Command Service (MICS) Media Independent Command Services (MICS) use the MIHF primitives to send commands from higher layers (e.g. Policy Engines to Mobility protocol) to lower layers. The MICS commands are utilized to determine the status of the connected links and also to execute mobile and connectivity decisions of the higher layers to the lower layers. Media Independent Information Service (MIIS) Media Independent Information Services (MIIS) provide a framework and mechanism for an MIHF entity to discover available neighboring network information within a geographical area to facilitate the handover process. The primary idea is that the MIIS can provide a set of information elements in specified structure and format which can be obtained through a certain query/response mechanism. Both static and dynamic information is provided by the MIIS. Examples of static information include the names and service providers of the MN’s current network neighborhood. Dynamic information include link layer parameters such as channel information, MAC addresses, security information, and other higher layer service information to make intelligent handover decision. This information could be made available through lower layers as well as higher layers. In some cases higher layer information services may be required when layer 2 information is not available or sufficient to make efficient handover decisions. In order to represent the information across different access technologies, the MIIS


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specifies a common way of representing this information by using a standardized format such as XML or ASN.1. THE PROPOSED HANDOVER MECHANISM Generally, the IP layer in the FMIPv6 needs the L2 trigger to perform handover initiation for NCoA configuration before L2 handover. In this case, MIH services are very useful for link layer triggers. But, with the existing MIH primitives, the handover performance of the MIPv6 is very limited because MIH service only is used for detecting L2 layer information. Especially, it hardly improves the performance of the FMIPv6. In this session, we propose an enhanced handover mechanism with new additional primitives and parameters to the MIH services. Proposed Handover Scheme Based on the above considerations, we propose an enhanced fast handover scheme for Mobile IPv6, which includes two parts. One is the new CoA generation maintenance method. By this method, the new CoA is generated by nAR beforehand and nAR maintains a CoA table for communications. The other is the proposed enhanced fast handover scheme. In this scheme, the binding updates to HA/CN are brought beforehand. Proposed New CoA Generation and Maintenance Method Method Overview: Here a new CoA generation and maintenance method is proposed to reduce the DAD (Duplicate Address Detection) latency in fast handover scheme, where the new CoA is generated by nAR instead of MN and the DAD is performed beforehand. It is also important to note that except for the reduction on latency, bringing the DAD procedure forward can make the issued NCoA unique. Thus, the binding update to HA/CN can be brought forward because there is no problem on the NCoA. We note that there are two kinds of new CoA generation methods (Thomson & Narten, 1998). One is the stateless autoconfiguration method and the other is the stateful autoconfiguration method. In this paper, we only consider stateless autoconfiguration method since it is widely used in Mobile IPv6. Brief descriptions are provided as follows. Firstly the link-local address is generated and then the DAD is performed. If DAD fails, the manual configuration should be carried out. If there is no problem with the DAD process, the router prefix should be


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obtained and the new CoA is generated using the link-local address and the router prefix. Though the probability that the duplicate link-local address occurs on the same link is low, it still cannot be ignored because communication quality will be greatly influenced if the duplicate address occurs. In the fast handover scheme (Moore ,2005), the DAD procedure is performed after the nAR receives the handover initiate packet or creating a link to the nAR is finished. Both methods will bring unpredictable latency. To reduce this latency, it is more reasonable if the new CoA is generated and the DAD is performed by nAR before requesting the NCoA by MN. At the same time, the information held by MN and needed for address autoconfiguration is the interface of MN. Thus if the nAR can know the interface and the AP-ID of the NAP, the nAR can autoconfigure the new CoA instead of the MN. Thus the new CoA generation operation can be moved from the MN to nAR. At the same time, the nAR can perform the DAD by searching the CoA list. Therefore, in the enhanced scheme, the unpredictable delay related to DAD can be avoided. Method Operations: In the proposed enhanced scheme, we let each AR maintain a CoA table as 2. This table is used to store the currently used CoA and the new CoAs for the coming MNs. If the CoA is a currently used one, the “Active” label should be specified as T. Otherwise; it will be specified as F, because this is an inactive CoA for a coming MN. Besides the “Active” label, there are some other options, such as “Start Time,” “Valid Time.” Table 2: AN EXAMPLE OF CoA TABLE MN-ID NCoA Active Start time Valid Time 2 NCoA 1 T 12:00 150s 43 NCoA 2 F 23:11 150s The Proposed Enhanced Fast Handover Scheme The proposed handover scheme defines new MIH primitives and parameters. As shown in Table 2 and Table 3 consecutively.


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Table 3: A new Primitives with its Description for the Proposed Mechanism Primitive

Service

MIH Link List

CS

MIH Link List Info

IS

MIH Link Available

ES

MIH EUI64 send

CS

MIH EUI64 send-info

IS

NCoA send

IS

MIH Link Going Down

ES

MIH Link Down

ES

MIH Link Up

ES

Description This Command sends from L3 to MIH in MN to get a list of available link by AP scan. This Information sends as response from MIH to L3 in MN to inform L3 with a list of available link by AP scan. This trigger specifies that a new available link is detected by MIH This Command sends from L3 to MIH in MN to sends its EUI64 to selected nAR This is a response information to deliver its EUI64 to nAR that selected by L3 MN This is NCoA that sends to MN L3 from nAR to inform it with new CoA that MN must uses in nAR A link down event will be fired in the near future, so the network layer must initiate the handover procedure This indicates that the link cannot be used for data transmission any more This is provided to L3 when a new link is connected

Table 4: A new Primitives and New Parameters for the Proposed Mechanism Primitive Service Parameters MIH Link List CS Interface ID , EUI64 , BW, Quality Level MIH Link List Info IS Interface ID , EUI64 , BW, Quality Level MIH Link Available ES Interface ID , EUI64 , BW, Quality Level MIH EUI64 send CS Interface ID , EUI64 MIH EUI64 send-info IS Interface ID , EUI64 NCoA send IS Interface ID , New CoA MIH Link Going Down ES Interface ID , EUI64 , BW, Quality Level MIH Link Down ES Interface ID , EUI64 MIH Link Up ES Interface ID , EUI64 So according to the new primitives and its parameters the method of our proposed we will be as follows as shown in Figure 5:


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Figure 5: The proposed fast Handover Mechanism using MIH primitives Step 1: The [MN -L3] sends periodically (MIH Link List ) to [MNMIH] to get a list of available link by AP scan. Step 2: After the [MN-MIH] receives this message from the [MN-L3] it will implement an AP scan to learn about AP and any changes that happen in its neighbours. Step 3: if it is a new AP discovers , a[MN-MIH] sends (MIH Link Available) to[MN-L3] with quality level and Bandwidth available for new subnets. Step 4: [MN-L3] test this new information about new subnets and decide which subnet ( AR, AP) will MN travel to it , so [MN-L3] sends (MIH EUI64 send) to [MN-MIH] to inform it to send its EUI64 to [nAR-L3] that selected. Step 5: MN will send its EUI64 to nAR and then nAR will find the right CoA for this MN from the CoA table and send back (NCoA send) to [MN-L3] as described previously . Step 6: The MN will save this NCoA in its cache to use it later when it moves to the new subnet and immediately the binding Update (BU) will send to HA/CN to inform them with this NCoA and tell them to send back binding Acknowledgment to New subnet (nAR). Step 7: When the link will going down the [MN –MIH] sends (MIH Link Going Down) to [MN-L3] to start Handover.


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Step 8 :[MN-L3] start handover procedure ( as in existing FMIPv6) by sending FBU(Fast Binding Update) to [oAR-L3] then [oAR-L3] will response by sending HI (Handover Initiate) to [nAR-L3] to establish tunnel between PAR and NAR. When nAR is ready,[nAR-L3] will send Hack (Handover Acknowledge) to [oAR-L3]. Step 9: The [oAR-L3] send FBack ( Fast Binding Acknowledgment) to [MN-L3] to notify MN to start handover. Then MN will start handover by sending (MIH Link Down) to [MN-L3] .Also,(MIH Link Down) will be sent to [oAR-MIH] by [oAR-L3] to inform it to disconnect MN from current attachment. Step 10: When MN connect to the new subnet on L2, [MN-MIH] will trigger (MIH Link Up) to [MN-L3] , and from the other side [nAR-MIH] will trigger (MIH Link Up) to [nAR-L3] to inform it with this MN attachment. Step 11:[MN-L3] will response by sending UNA(Unsolicited Neighbor Advertisement)(Koodli ,2008) to [nAR-L3] to tell it to deliver packets that stores to MN immediately . Step 12: In consequence of establishing binding updates before starting MN handover, packet will start arriving to MN from HA/CN immediately. In the original FMIPv6, ARs exchange the information about their neighbors and have to reconstruct the mapping table for proxy advertisements with information on the neighbouring subnets. In the proposed mechanism, since MN get the NCoA from nAR regarding new primitive and parameter in advance, AR need not exchange information about their neighbour. Also, MN need not exchange RtSolPr/PrRtAdv messages or RS/RA messages for Router Discovery, because the NCoA information is already contained in MIH primitives. On the other side , In the original FMIPv6 , binding Update process performs after MN connects to New AR . In the proposed mechanism , this process performs before start L2 Handover ( in initiated Handover process).

PERFORMANCE EVALUATION In case of the scheme FMIPv6, the handover initiation time is reduced by removing the time for Proxy Router Discovery, DPrRD and the time for Binding Update procedure including RR procedure DBU. We can observe here two cases :


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Case 1 : TBU DL2+ 2DMN-nAR So , we can write a table that discusses this Handover Latency (table 6): Table 6: Handover Latency and Handover Initiation Time for FMIPv6 with/without the Proposed scheme (Case 2) Handover Mechanism FMIPv6 Proposed FMIPv6

Handover Latency DL2+ 2DMN-nAR+ DBU 2DMN-nAR

Handover Initiation Time DPrRD+ DFMIP DFMIP

The handover latency shown in Table 5 can be expressed as follows: DHO-FMIPv6 = DL2+2RTTMN-nAR+RTTnAR-HA (3) DHO-ProFMIPv6 = 2RTTMN-nAR (4) where DL2 is the L2 handover latency, RTTMN-nAR is the round trip time between MN and nAR, and RTTnAR-HA is the round trip time between nAR and HA/CN. In both cases we can see that the important time in our proposed Protocol is 2DMN-nAR which related to the physical media that MN connect to .So , the speed of getting the stored packets in NAR is vary depending on the kind of wireless networks.


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Figure 6: Comparison of handover Latency the FMIPv6 with/without the Proposed scheme Figure 6 compares the handover latency among the FMIPv6, and the proposed mechanism depending on case 1 (the worst case). We assume RTTnAR-HA are 10ms. In case of the FMIPv6, FMIPv6 can reduce not handover latency after L2 handover but handover initiation. During the handover initiation in the FMIPv6, the MN could lose its connectivity to the oAR due to a sudden degradation of the link quality. In these failure cases, the FMIPv6 performs in the reactive FMIPv6 and thereby the handover latency is increased. So, the FMIPv6 with the proposed scheme can reduce the expected handover latency in the FMIPv6


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Figure 7: Coverage overlap for Handover Initiation Time As shown in Figure 7, coverage overlap is required for MN to perform handover initiation and link layer handover in the FMIPv6. If the coverage overlap is too large, the coverage area is reduced, resulting in capacity reduction of coverage. On the other hand, if it is too small, the MN does not have enough time for the handover initiation which the MN predicts its movement between coverages. It results in handover latency reduction (Soliman et al. , 2005). We can express the handover initiation time as follows: TFMIPv6 =DPrRD + DFMIP =2RTTMN-oAR+(2RTTMN-oAR+2RTToAR-nAR) =4RTTMN-oAR +2 ∆ TProFMIPv6= DFMIP TProFMIPv6=2RTTMN-oAR +2∆ where ∆ , RTToAR-nAR, can be neglected because they are very small values.


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Figure 8: Relationship between the Coverage Overlap Length for Handover Initiation Time and the Moving Speed of MN Figure 8 shows the coverage overlap length according to the moving speed of MN for the FMIPv6 and the proposed mechanism . Here, we can see that the handover initiation time has decreased and the size of the coverage overlap area has decreased. Thus, the whole coverage capacity has increased. Consequently, the proposed mechanism is cost-effective for network design. In other hand, the proposed mechanism increases the probability that the FMIPv6 is performed in predictive mode. CONCLUSION In this paper, we propose an enhanced fast handover scheme for Mobile IPv6 , with MIH services defined in IEEE 802.21. To do so, we defined a new primitives to the existing MIH primitives. In our scheme, each AR maintains a CoA table, and generates a new CoA for the MN that is anticipated to move to its domain. At the same time, we propose the binding updates to HA/CN are performed by MN when NCoA delivers from nAR to MN using MIH primitives in order to remove this time delay as in the existing FMIPv6. Then , we discusses tow cases of Handover latency in our propsed protocol.Finally, in our proposed scheme, we can increase the probability that the FMIPv6 can be performed in predictive mode by reducing the handover initiation time, thereby we can reduce the expected handover latency in the FMIPv6. In


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addition, with the proposed scheme, we can design the network costeffectively by reducing coverage overlap between adjacent cells because the handover initiation time in the FMIPv6 is decreased. FUTUE WORKS As a develpoment of this study we can devlope this study in many ways.First way is combine our prosed protocol (that based on FMIPv6) with HMIPv6 protocol or with PMIPv6 protocol.Second way is to study our Propsed Protocol in the ping – pong situation. ACRONYMS Ack AP AP –ID AR AR-Info Assoc Auth BU BU_Ack CN CoA DAD EIR EUI-64 FBack FBU FMIPv6 HA HACK HI HoA IEEE IETF Interface ID IP IPv6 L2 L3

Acknowledgment Access Point Access Point Identifier Access Router Access Router information Association Authentication Binding Update Binding Update Acknowledgment correspondent Node Care of Address Duplicate Address Detection Equipment Identity Register Extended Unique Identifier 64 bit Fast Binding Acknowledgement Fast Binding Update Fast Handover Mobile Internet Protocol version 6 Home Agent Handover Acknowledge Handover Initiate Home of Address Institute of Electrical and Electronic Engineers Internet Engineering Task Force Interface Identifier Internet Protocol Internet Protocol version 6 Layer 2 Layer 3

Reduce delay in FMIPv6 using IEEE 802.21 MIPv4 MIPv6 MN NAR NCoA PAR PCoA PrRtAdv QoS RA RtSolPr UNA

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Mobile Internet Protocol version 4 Mobile Internet Protocol version 6 Mobile Node New Access Router New Care of Address Previous Access Router Previous Care of Address Proxy Router Advertisement Quality of Service Router Advisement Router Solicitation for Proxy Advertisement Unsolicited Neighbor Advertisement REFERENCES

Daley, G. , & Pentland, B. ,& Nelson, R. (2003). Effects of Fast Router Advertisement on Mobile IPv6 Handovers at the 2004 IEEE ISCC’03. Johnson, D. , & Perkins, E. C. ,& Arkko, J. (2004, June). Mobility support in IPv6. RFC 3775. Kwon ,Dong-Hee, & Kim, Yong-Sung, & Bae ,Kyung-Jin, & Suh ,Young-Joo (2005,Dec.). Access router information protocol with FMIPv6 for efficient handovers and their implementations at Global Telecommunications Conference, 2005. IEEE GLOBECOM '05 , 6. Koodli, R. (2008, June). Fast handovers for mobile IPv6. RFC 5268. Liebsch, M. , & Singh, A. ,& Chaskar, H. ,& Funato, D. ,& Shim, E. (2005, July). Candidate Access Router Discovery accounting requirements. RFC 4066. Moore, N. (2005, April). Optimistic Duplicate Address Detection for IPv6 . RFC 4429. Perkins, E. C., (2002, Aug.). Mobility support in IPv4. RFC 3344. Soliman, H. (2004). Mobile IPv6 : Mobility in a Wireless Internet,First Edition , Addison-Wesley, USA. Soliman, H. , & Castelluccia, C. ,& El Malki, K. ,& Bellier, L. (2005, Aug.). Hierarchical mobile IPv6 mobility management (HMIPv6). RFC 4140. Thomson, S. , & Narten, T. (1998, Dec.). IPv6 stateless address autoconﬁguration. RFC 2462. Mussabbir , Q., & Yao , W. (2006, Dec.). Optimized FMIPv6 handover using IEEE802.21 MIH services at Proceedings of first


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ACM/IEEE international workshop on Mobility in the evolving internet architecture, 2006. Tran-Trong, S. ,& Tursunova ,S. ,& Kim ,Y. ,(2008). Enhanced Vertical Handover in Mobile IPv6 with Media Independent Handover Services and Advance Duplicate Address Detection at KNOM conference 2008.