A Probabilistic Scheme for Reducing the Packet Loss in Mobile IPv6

Transcription

1 1912 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER 212 A Probabilistic Scheme for Reducing the Loss in Mobile IPv6 Md. Humayun Kabir and Khan Md. Al-Farabi Department of Computer Science and Engineering Bangladesh University of Engineering and Technology, Dhaka, Bangladesh mhkabir@gmail.com,farabibuet@gmail.com, Abstract Mobile IPv6 allows a Mobile Node to remain reachable by a Correspondent Node while roaming from one network to another network. In Mobile IPv6, a Mobile Node directly updates its current loc inform to a Correspondent Node using a route optimiz method. Route optimiz helps to culminate the packet delay incurred due to suboptimal route traversed by the packets from a Correspondent Node to a Mobile Node in Mobile IPv4. However, it introduces packet losses during Mobile Node's transition from one network to another network. This packet loss increases as the mobility of the node increases. In this paper, we propose a probabilistic scheme to reduce this packet loss. Our solution is based on the Mobile Node's mobility prediction at the Correspondent Node and a buffering mechanism at the Home Agent. Simul results prove the effectiveness of our scheme in case of reducing the packet loss problem besetting the Mobile IPv6. Index Terms, Route Optimiz, Loss, Mobility Prediction, Buffering I. INTRODUCTION Mobile IPv4 (MIPv4) [1] is the first network layer protocol used for handling the mobility. In MIPv4, each mobile node (MN) has a home-address (HoA) acquired from its home network. An MN maintains its communic with a correspondent node (CN) via a Home Agent (HA) while it is in a foreign network. HA is an entity in MN's home network which maps its HoA with the care-of-address (CoA). An MN acquires a CoA in a foreign network and sends a Binding Update (BU) message to the HA informing the CoA. Data packets sent by a CN to MN's HoA reaches HA. HA encapsulates the packets into new packets and forwards them to CoA. Thus, a triangular route CN-HA-MN along with a tunnel between the home agent and MN is created. This triangular route is a sub optimal route, which creates triangular delay problem. Therefore, Mobile IPv4 though successfully delivers the data packets to the mobile node either at the home network or at the foreign networks; it suffers from triangular delay problems. The border router checks the source IP prefix of the packets passing through the subnet. If the source IP prefix does not match with the IP prefix of the subnet, the border router drops the packets rather than passing them. This is known as ingress filtering. In MIPv4, the packets which are sent by a MN from its foreign networks may be dropped by the border routers of the foreign subnet due to ingress filtering. In order to overcome the problems suffered by MIPv4, Mobile IPv6 () [2][3] uses the route optimiz technique to provide direct communic between MN and CN. Route optimiz technique effectively solves the triangular delay and ingress filtering problems of MIPv4. However, because of the direct communic between MN and CN, some packets might get lost when a MN moves form one foreign network to another foreign network. loss occurs due to the fact that the MN's movement from its current loc to a new loc happens abruptly and remains unaware of by the CN for some time. As a result, the CN continues to send the packets to MN's obsolete loc, which is no longer reachable. A number of research works have been done to enhance the current. One of such research works is F [6]. F reduces the handover delay and packet loss. However, F needs to use link-layer triggering signal or predict the future destin. Another research work in [7] proposes H that reduces the signaling messages as well as the handover latency. However, H is effective only in intra-domain routing and fails in inter-domain routing. Research work [8] has integrated F and H into FH. In this paper, we propose a scheme to reduce the packet loss of without depending on cross layer signaling, router prediction and foreign router's buffer. Our scheme is mainly based on MN's mobility prediction at CN and a buffering mechanism at HA. Our scheme does not introduce new network overhead. Simul results show that our scheme effectively reduces the packet loss in. A short version of this research work has already been published in [12]. The rest of the paper is organized as follows: Section II describes the related research work for. Section III describes our proposed solution. In Section IV, we present our simul results. Finally, we conclude the paper in Section V. II. RELATED RESEARCH WORKS supports mobile end systems in the Internet. Unlike MIPv4, it does not suffer from sub optimal doi:1.434/jnw

2 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER routing and ingress and egress filtering. However, data loss may happen in due to frequent movements of the mobile end systems. For this reason, several extensions of exist. Among them F [6], H [7], and FH [8] are the most prominent. A. Fast Handover for Mobile IPv6 Fast Handover for Mobile IPv6 (F) [6] has extended in order to reduce the handover delay and packet loss. In F, two more additional entities are used along with the HA. One is the Previous Access Router (PAR) which is the current loc of the MN and the PAR functions as the temporary HA for the MN in the foreign link. The other one is the New Access Router (NAR) which is the future destin of the MN. The handover oper of an MN from the PAR to the NAR happens as follows. An MN can initiate the handover while it gets mobility trigger from the data link layer. This is known as MN initiated handover. An unsolicited router advertisement message is exchanged among the neighboring routers to inform about their link status inform. The PAR receives an unsolicited router advertisement message from the NAR, which contains NAR's IP and link layer addresses. The PAR maintains this inform in a binding cache. The MN gets a layer two trigger when it reaches near to NAR. The layer two trigger contains the link layer address of the NAR. The layer two trigger also contains a confidence level (in percentage) parameter which indicates whether the MN is really near to the NAR or not. While the MN gets a layer two trigger with around 9 percent confidence level, the MN assumes that it is really near to the NAR. Then, the MN sends a Router Solicit for Proxy (RtSolPr) message to the PAR which contains the link layer address of the NAR. The PAR retrieves the IP address of the NAR and the prefix of the CoA of the MN in the NAR from its binding cache using the link layer address received in RtSolPr message. The PAR sends this inform to the MN through a Proxy Router Advertisement (PrRtADV) message. The MN generates the CoA for the NAR using the prefix defined in PrRtADV message through stateless address gener mechanism and sends this generated CoA to the PAR using a Fast Binding Update (FBU) message. After getting the FBU message, the PAR sends a Handover Initi (HI) message, which includes the new CoA and the old CoA of the MN, to the NAR for authentic and non-duplicate address checking. After the successful authentic and non-duplicate address verific, the NAR sends a handover acknowledgement (HAck) message to the PAR. The PAR creates a tunnel with the NAR and sends CN's packets through the tunnel towards the NAR. The NAR buffers the data packets coming from the PAR for the MN. At the same time the PAR sends a Fast Binding Acknowledgement (FBAck) message to the current link or the CoA of the MN. While the MN gets a layer two trigger which has about 1 percent confidence level, the MN becomes aware that it reached the NAR and sends a Fast Neighbor Advertisement (FNA) message to get the buffered packets from the NAR. In F, the MN uses the CoA from the PAR to maintain the communic with CN until the route optimiz mechanism is completed. After the successful completion of the route optimiz process the MN will use the new CoA at the NAR to communicate with the CN. Figure 1 shows the signaling messages of F. Figure 1. Signaling Messages of F In F, the future network point of attachment of an MN also can be predicted instead of using link layer triggering. In both cases, MN can generate the new care of address regarding the future attachment point ahead. This reduces the delay to resume communic between the MN and the CN or the HA after moving from one network to another network. However, link layer triggering or the prediction of the future attachment point of an MN might not be possible always. In F, the previous access router functions as a temporary HA. For this reason, the foreign router has to use a buffer to store the data temporary. This temporary storage might not be available in every foreign router. In [14], the performance of F and have been compared and analyzed in terms of handover latency. B. Hierarchical Mobile IPv6 Hierarchical Mobile IPv6 (H) [7] is another extension of. A new entity is introduced in this scheme called Mobility Anchor Point (MAP). An access router in the foreign link can work as a MAP as well as a foreign access router. In order to act as a MAP, a router has to set its MAP option to true. A MAP represents the MN s in the foreign link. MAP broadcasts a Neighbor Advertisement (NA) message to its neighboring access routers to inform that it is working as a MAP. Neighboring routers caches the MAP address from the NA message. When an MN reaches the foreign link it

3 1914 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER 212 broadcasts a Router Solicit (RS) message. The routers in the foreign link reply with a Router Advertisement (RA) message. A RA message contains the MAP address and the on-link Care of Address (LCoA). The MN uses the MAP address as its Regional Care of Address (RCoA) while LCoA as its current attachment point address. In case of multiple MAPs, the MN chooses the farthest MAP based on the distance field and the preference field of MAP option in the RA message. The distance field defines the distance between a MAP and an MN. The preference field defines the availability of a MAP. In order to choose a MAP, an MN arranges the available MAPs in the descending order of their distance and then selects the first MAP from the list. The MN checks the preference field of the selected MAP. If the value of the preference field is not zero, the MN will use the selected MAP; otherwise, the MN will select the next MAP and this process will be continued until the MN gets a MAP with a nonzero preference field. After selecting the MAP, the MN has to register itself with the MAP by sending a Local Binding Update (LBU) message, which contains HoA and LCoA. A LBU message also contains the additional flag M, which is set by the MN to indicate that this BU message for the MAP not for the HA. The MAP sends a Local Binding Acknowledgement (LBAck) to the MN. Like, the MN sends the BU message to the HA, however, it sends RCoA as the CoA instead of LCoA in the BU message. When a CN wants to send a data packet to the MN, it first sends the packet to the HA. The HA tunnels the data packet to the corresponding MAP and the MAP forwards the data packets to the MN. The MN starts the route optimiz procedure after receiving the first data packet from a CN through the MAP. After the successful completion of route optimiz procedure, the MN sends a BU message to the CN. RCoA is used as the source address in this BU message instead of LCoA. The CN replies with a BAck message to the MAP. The MAP forwards the BAck message to the MN. Now, the CN is ready to send the future data packets directly to the MAP. The MAP forwards the incoming data packets to the MN. The MN can send the data packets directly to the CN setting the source address of data packet to RCoA. When MN changes the access router within the same MAP domain; it only sends a LBU message to the MAP. The MN does not require sending the BU message to the HA or to the CN which reduces the number of signaling messages. However, if the MN moves from one MAP to another MAP, the MN has to send a BU message to the HA and to the CN. This BU message contains HoA and the new RCoA of the MN. In this case, the MN registers itself with the new MAP by sending a LBU message which contains the new RCoA and LCoA. The new MAP replies with an LBAck message to complete the registr process. Figure 2 shows the signaling messages of H. Figure 2. Signaling Messages of H H reduces the signaling messages and thus reduces the handover latency for intra-domain networking system. However, it is not effective in interdomain mobility. H does not reduce the packet loss problem at all. C. Fast Handover for Hierarchical Mobile IPv6 FH [8] stands for Fast Handover for Hierarchical Mobile IPv6. This scheme uses all the messages of F. Only difference is that the Mobility Anchor Pont (MAP) of H is used instead of Previous Access Router (PAR) of F, for handling the handover messages. The detailed description of handover oper of FH is given below: The MN sends a Router Solicit for Proxy (RtSolPr) message to the MAP based on the data link layer handover trigger. In FH, RtSolPr includes inform about the link layer address of the new access router (NAR) which is the future destin of MN. The MAP stores the network prefix and the link layer address of the associated access router in its domain in the binding cache. In response to the RtSolPr message, the MAP sends a Proxy Router Advertisement (PrRtAdv) message to the MN, which contains network prefix inform about the New Local Care of Address (NLCoA) for the MN to use in the NAR region. After receiving the PrRtAdv message, the MN generates a NLCoA in a stateless manner using the inform of PrRtAdv message and sends a Fast Binding Update (FBU) message to the MAP. The FBU message contains NLCoA. After receiving the FBU message from the MN, the MAP sends a Handover Initi (HI) message to the NAR to establish a bi-directional tunnel between the MAP and the NAR. This HI message contains NLCoA

4 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER which is retrieved from the FBU message. After successful completion of authentic and nonduplicate address verific, NAR sends a handover acknowledgement (HAck) message like F to the MAP in response to the HI message and a tunnel is established between the MAP and the NAR. The NAR buffers the CN's data packets coming from the MAP for the MN. At the same time, the MAP sends a Fast Binding Acknowledgement (FBAck) message to the current loc of the MN in response to the FBU message. When the MN reaches the NAR, the MN sends a Fast Neighbor Advertisement (FNA) message to the NAR, which works as the request to deliver the buffered data packets. Then, the NAR delivers the buffered data packets to the MN. The MN then follows the normal H opers by sending a Local Binding Update (LBU) message to the MAP. Figure 3 shows the signaling messages of FH. FH reduces handover delay and packet loss like F. FH, however, suffers from all the problems of F and it does not deal with interdomain mobility. D. Recent Related Works Zaki et al. [13] proposed a two-tier buffer mechanism at CN to reduce the packet loss. In two-tier buffer mechanism, the CN stores the data packets, which have already been sent to the MN in a first tier buffer and sends the data packets from this buffer to the MN when it learns that the MN has moved to a new address. The scheme proposed a second tier buffer to store the copy of the data packets that have been sent to the MN from the first tier buffer. The CN starts sending data packets of the second tier buffer to the MN when it learns that the MN has move to a new address while receiving data packets from the first tier buffer. Always copying the data packets in two buffers introduces great overhead in this scheme. Gupta et al. [15] reduced the handover delay and packet loss problem of by predicting a set of future routers before the handover and buffering the packets in all the predicted routers during the handover. In their scheme, while the MN reaches the foreign link, it sends Router Solicit (RS) message to the neighboring routers and in reply to the RS message the neighboring routers sends the Router Advertisement (RA) message to the MN. After receiving RA message, it detects the movement from one network to another network. Then the MN sends an FBU to the Previous Access Router (PAR). The FBU message includes a group of addresses that are considered to be the possible NAR to which the MN may connect. The MN predicts those NARs as future destin based on the strength of RA message and creates a group of address in descending order of the strength. Then during handover, the packets sent by the CN towards the MN, are multicast from the PAR to the NARs where these packets will be buffered. The layer two trigger contains a confidence level (%) parameter which indicates that whether the MN is near to the NAR or not. While the MN gets a layer two trigger which has about 1 % confidence level, the MN becomes aware that it reached the NAR and sends the Neighbor Solicit (NS) message to the New Access Router (NAR) requesting for the configur of new CoA to be assigned and for sending the buffered data packet. The NAR forwards the buffered data packet to the MN. The NAR configures the unique new CoA for the MN from the free address pool using the link-layer address of MN from the NS message. The NAR then sends the new CoA to the MN by encapsulating it in the Neighbor Advertisement (NA) message. When the MN gets assigned the new CoA, it sends the BU message to the HA for its new CoA registr. On receiving the BU from MN, the HA confirms the update by sending the BA message to the MN. The MN after receiving the BA message from the HA, sends the BU to the CNs to inform them about its new CoA for direct communic. When the process is completed, the communic reestablishes. Although they reduce the handover delay by avoiding DAD process and packet loss by buffering packets at the future access routers, they require to predicting a set of future routers and to buffer packets in all of these predicted routers. The MN might move to only one of these predicted routers, i.e., multicasting the packets to all of them as well as buffering the packets in all of them are obvious wastage of resources. The Proxy Mobile IPv6 (P) [16] [17] is a network-based mobility protocol, which reduces the handover signaling messages and handover latency. The P extends the by introducing two important entities called Local Mobility Anchor (LMA) and the Mobile Access Gateway (MAG). The LMA acts similar to the HA in the and maintains the MN s binding inform, while the MAG performs the taks of mobility management for the MN. The oper of P is described as follows. When a MN reaches the access network, it sends the RS message to the router in the access network. The access router receives the RS message and works as an MAG for the MN. The RS message contains the Mobile Node ID (MN-ID). The MN-ID is the MAC address of the interface of the MAG where the MN is connected. The MAG authenticates the MN with the AAA (Authentic, Authoriz and Accounting) server. After the successful authentic, the MAG sends this MN_ID along with Proxy Care-of-Address (PCoA) through the Proxy Binding Update (PBU) message to the LMA. PCoA is the address of the MAG. The LMA accepts the PBU message and assigns a network prefix for the MN. This network prefix is known as Home Network Prefix (HNP). The LMA broadcasts this network prefix of the MN in its network domain. In the network domain of the LMA, each MN has unique network prefix. The LMA sends this assigned network prefix of the MN through the Proxy Binding Acknowledgement (PBA) message to the MAG in reply to the PBU message. Thus a tunnel is established between the MAG and the LMA. The MAG sends the assigned network prefix using Router Advertisement (RA) to the MN in reply to the RS message. The MN configures its own IPv6 address using network prefix in RA message

5 1916 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER 212 and starts communicating with the CN. The data packet sent from the MN is received by the MAG. The MAG encapsulates the traffic and transfers them to the LMA. The LMA decapsulates the packets and forwards them to the CN. The data packets coming from the CN are intercepted by the LMA and the LMA tunnels the data packets to the MAG. The MAG decapsulates the packets and forwards them to MN. Although P reduces handover latency, it does not support route optimiz process. The seamless mobility is only provided as long as the MN is connected to the network attachment points of the same LMA. When the MN moves from one LMA to another LMA, the MN has to establish the network connection again. III. PROPOSED SCHEME F [6] and FH [8] need link layer triggering or next router prediction. Moreover, FH [8] does not help in inter-network hand off. H [7] does not resolve the said packet loss issue at all. None of these schemes has resolved the packet loss problem that occurs during the hand off of a MN in IPv6 networks without depending on certain constraints, such as link layer triggering, future router prediction and Foreign Router s buffering. In this section, we propose a scheme to reduce the packet losses due to the hand off of an MN from one foreign network to another foreign network. Our goal is to make the scheme effective without imposing any constraint. A. Our solution to solve the packet loss problem in will be based on MN's mobility prediction at the CN and a buffering mechanism at the HA. We predict the probability of departure of the MN from its current care of address (CoA). Detail comput of our probability of departure is given in Section B. Based on the above probability value, CN will set its HoA bit and start sending the copies of the data packets to the HA of the MN while sending the data packets to MN's current CoA. At the same time, the CN will send a Binding Refresh Request (BRR) message to MN's HA. The HA will forward the BRR message to the current CoA of the MN and buffer the incoming data packets from the CN. The HA will set the lifetime for the buffer based on the lifetime of the home registr time which will be retrieved from the TTL value of the BU message. The buffer lifetime must be less than the lifetime of home registr. This buffer lifetime will be estimated by subtracting the arrival time of the BRR message at the home agent from home registr lifetime. If the MN is still attached to the current CoA, it will simply reply to the BRR message by sending a BU message inserting the current CoA. In this case, the HA will release the packets from the buffer since the MN did not switch from the current CoA to a new CoA and has already received all the packets that are in the buffer. If the MN moves to a new CoA, it will send a BU message to the HA inserting the new CoA and start RRP procedure in order to establish a direct communic with the CN. After receiving the BU message from the MN, the HA will forward the buffered data packets to the new CoA of the MN. Thus, no data packet will be lost while MN is moving from one CoA to another CoA. Figure 4 shows the signaling messages of our proposed solution. Figure 3. Signaling Messages of FH Figure 4. Signaling Messages of

6 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER B. Probability Mechanism In our proposed solution a CN will compute the probability of the departure of an MN from its current care of address to a new care of address. The CN will maintain three attributes in its Binding Cache to compute the above probability. One of the attributes will be a counter c, which will count the number of BU messages from the MN from its current care of address. The second attribute will be a probability estimate p, which will represent the current probability estim of the MN to move from its current loc to a new loc. The third attribute will be a threshold value Th, which will denote the threshold value of the probability p. By comparing estimated p with Th, our proposed scheme will determine whether the MN has a real possibility to change its current loc or not. In our scheme, the threshold value Th will not be fixed rather adaptive. The computs of c, p and Th are given below. A CN will reset the counter c to one when it receives a BU message from an MN from a new CoA. At each successive reception of BU message from the same CoA, we propose the CN to increment the value of c and compute Th. The CN will receive the TTL value sets by a MN in the BU message. This TTL value is the lifetime of the current CN registr, i.e., CN is allowed to send data packets to the MN directly to its current CoA only within this TTL amount of time. We propose to compute the remaining lifetime of the CN registr and call it Rtt. Just after a CN registr, a CN should set Rtt to TTL. At each unit of time passed after the current CN registr, we propose the CN to decrement Rtt by 1 and estimate the probability p using Equ (1) for each Rtt value. We propose, the CN to send a BRR message to the MN when p becomes greater than or equal to Th. After receiving the BRR message, the MN will respond with a BU message. If the MN still remains in the same CoA, it will first increase the TTL value of the BU message exponentially and send it to the CN. At the reception of a BU message with the same CoA, the CN will increment c and set its CN registr life-time equal to the TTL value of the BU message. An increment in c indicates that the MN has already stayed long time in the current loc and its probability to leave the current loc is higher. For this reason, we choose p to increase with c. However, the rate of increment of p with c should be less when c is becoming larger than that of p when c is smaller. This is because a larger c indicates little more stability of the MN in its current loc than that indicates by a smaller c. We c choose expression for p to make sure that p grows c +1 more with c when c is smaller than it does with c when c is greater. We can see this pattern of growth of p with c by plotting c p = in Figure 5 c +1 Figure 5. The growth of p against c Again, within a particular CN registr interval the probability of the MN to leave its current loc becomes higher as the remaining life-time decreases. In order to reflect the effect of the remaining life-time on the Rtt growth of p we compute p as the exponent of TTL follows: c p ( ) c + 1 Rtt TTL = (1) where Rtt =TTL, TTL-1,...,3,2,1. When Rtt value becomes 1 Equ (1) yields the highest or the peak value of p of the current CN registr interval. It is better to activate our buffering mechanism before p reaches such peak. However, it will be too early if we activate the buffering mechanism before p reaches the peak of the previous CN registr interval. For these reasons, we activate our buffering mechanism in the middle of these two peaks. Our threshold Th sets the activ point of our buffering mechanism, therefore, we calculate Th as follows: Th c ( ) c TTL c 1 + ( ) c 2 2 TTL = (2) If we plot p and Th using Equs (1) and (2) respectively against the time assuming the MN in the same loc, we will get the graphs as shown in Figure 6. The graph in the Figure 6 demonstrates our desired patterns of p, i.e., p grows both with the increment in c and with the decrement in Rtt. Within a CN registr interval, which is between any two consecutive values of c in the graph, we wanted p to grow by a faster rate with the decrement in Rtt (remaining life-time) until it reaches the peak of that particular registr interval. At the beginning of a CN registr interval, we wanted p as

7 1918 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER 212 always to start with a value less than the peak but higher than the startup value of the previous registr interval. 1 TH.95 TH.9.85 Probability.8 (P) TH C=5 C=4.75 C= TH C= C= Time(Sec) Figure 6: Probability (p) vs. Time (Sec.) Figure 6 also demonstrates that our Th for a CN registr interval is in the middle of two peak values of p, where one peak is the peak of that particular registr interval and the other peak is the peak of the previous registr interval. IV. SIMULATION RESULT We have simulated our proposed solution using OPNET simulator in order to evaluate our scheme. We have used OPNET MODELER 14. in Windows XP. In our simul scenario, we have varied the number of mobile nodes, CNs and foreign routers in order to evaluate the performance of our proposed scheme compared to that of and H with different combins of mobile nodes, CNs and foreign routers. We compare our scheme with the other schemes with respect to packet loss, end-to-end delay and network overhead. These are the standard performance metrics that have been used by many other research works [9][1][11] to compare different networking schemes. The packet loss under a networking scheme is the difference between the total number of packets sent and the total number of packets delivered by the network. The end-to-end delay is the average time required for a packet from the source to reach the destin through the network. The network overhead is the ratio between the total number of control packets and the total number of data packets passed through the network. We do not compare the performance of F and the scheme of [11] because it works in cross layer architecture and require link layer trigger. Whereas our solution is completely in the network layer and avoids cross layer triggering. We have defined the ratios of mobile nodes, CNs and foreign routers as MN: CN: FR. We have set a random distance among the mobile nodes, CNs and foreign routers in order to mimic the real-life situ. This random distance varies from 2 to 1 meters. In our simul each MN is communicating with each correspondent node. We assumed 5 packet buffering capacity at the HA. In each experiment that either measure packet loss or end-to-end delay, we ran each simul run for 5 hours. The packet transmission rate for both MN and CN has been maintained 2 packets per hour in each simul run. A. Loss vs. Time We plot cumulative packet loss against the simul time in Figures 7 and 8. In Figure 7, we set the speed of the MN and CN to human walking speed, i.e., 1 meter/sec. In Figure 8, we set it to car speed, i.e., 15 meter/sec. By varying the number of MN, CN and FR we simulated numerous scenarios for both speeds. Due to space limit we only show the results of two scenarios in both figures. The results of other scenarios follow the same pattern H solution Time(hour) Figure 7.a. Cumulative in [2], H [7] and (MN: CN: FR->4:45:25) (using human walking speed) HMIpv Time (hour) Figure 7.b. Cumulative in [2], H [7] and (MN: CN: FR->65:7:45) (using human walking speed)

8 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER H H Time(hour) Figure 8.a. Cumulative in [2], H [7] and (MN: CN: FR->4:45:25) (using car speed) Speed (m/s) Figure 9.a. Cumulative due to mobility in [2], H [7] and (MN: CN: FR->4:45:25) (Time: 5 hours) H 1 8 H Speed (m/s) Time (hour) Figure 8.b. Cumulative in [2], H [7] and (MN: CN: FR->65:7:45) (using car speed) The graphs in Figures 7 and 8 show that the cumulative packet losses are always less in our proposed solution compared to that of regular and H in all the scenarios. When the numbers of MN, CN, and FR are increasing, packet loss is even less in our proposed solution and the performance gap with the regular and H becomes wider. The packet loss is less in our scheme in all the cases since we compute the probability of departure of MN form its current loc and using this probability we activate the buffer at the HA. CN sends packets to both HA and MN (in its current loc). HA stores the data packets coming from CN in the buffer and forwards them to the MN if it moves away from its current loc. This saves a significant number of packets that could have been lost otherwise due to the mobility of the MN in regular and H. B. Loss vs. Speed of MN We plot the cumulative packet loss due to mobility against the speed of MN in Figure 9. In our simul, we varied the speed of the MN from human walking speed, i.e., 1 meter/sec, to car speed, i.e., 15 meter/sec. Figure 9.b. Cumulative due to mobility in [2], H [7] and (MN: CN: FR->65:7:45) (Time: 5 hours) In order to see the effect of node mobility only on the packet loss we draw the packet loss only due to the mobility of the MN in Figure 9. However, the packet loss may occur due to other reasons, such as bit-error and congestion. In order to see the combined effect of node mobility, bit-error, and congestion we plot the cumulative packet loss against the speed of the MN due to mobility, bit-error, and congestion in Figure H Speed (m/s) Figure 1.a. Cumulative due to mobility, bit-error and congestion in [2], H [7] and (MN: CN: FR->4:45:25) (Time: 5 hours)

9 192 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER H Speed (m/s) Figure 1.b. Cumulative due to mobility, bit-error and congestion in [2], H [7] and (MN: CN: FR->8:85:65) (Time: 5 hours) From Figures 9 and 1, we see that the packet loss is increasing along with the speed of the MN in, H and our proposed solution. The packet loss increases along with the speeds because at the higher speed the number of handoffs of the MN increases which in turn contributes to add more packet loss. However, the packet loss is less at all the speeds in our scheme compared to that of regular and H in both figures. Buffering mechanism at the HA based on the mobility prediction at the CN help our scheme to achieve less packet loss compared to that of both and H. C. End to End Delay We measure the end to end delay for, H and our proposed solution by varying the speed of the MN from 1 m/s to 15 m/s. End-to-End Delay (sec.) Speed (m/s) H Figure11.b. End to end delay vs. mobility in [2], H [7] and (MN:CN:FR-> 65: 7:45) From Figure 11, it is clear that our proposed scheme suffers from almost the same end-to-end delay as. However, it suffers from little higher delay compared to that of H. In our scheme, each time an MN moves from one network to another network it has to perform the return routability procedure and collect the missing data packets from the home agent, which adds some delay. On the other hand, in H an MN performs the return routability procedure only once when it moves from a MAP to another MAP. When the MN moves from one access network to another access network within the same MAP, it does not require to performing the return routability procedure, i.e. the delay for return routability signaling does not occur in many movements in H. C. Network Overhead We measure the network overhead for, H and our proposed solution by varying the time from 1 hour to 5 hours. 1 9 End-to-End Delay (sec.) Speed (m/s) H Network Overhead (% ) H Figure11.a. End to end delay vs. mobility in [2], H [7] and (MN:CN:FR-> 15: 2:1) Time (hour) Figure12.a. Network overhead in [2], H [7] and (MN:CN:FR->4:45:25)

10 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER Network Overhead (%) Time (hour) H Figure12.b.Network overhead in [2], H [7] and (MN:CN:FR->6:7:45) Figure 12 clearly depicts that our solution exhibits less network overhead compared to that of. Network overhead is measured as the ratio between the total number of control packets and the total number of delivered packets. The total number of control packets remains almost the same in as that of in our scheme. However, more packets are lost in compared to that of in our scheme. As a result, the total number of delivered packets becomes less in, which yields higher network overhead. Figure 1 shows that our scheme requires higher network overhead compared to that of H. In our scheme, for each movement of the MN from one access network to another access network, the MN has to perform a return routability procedure, which adds more network overheads. On the other hand, the return routability procedure is required only when the MN moves from one MAP to another MAP in H. While the MN moves within the same MAP, it does not require any return routability procedure, i.e. incurs fewer network overhead. The statistical significance of our simul results is given in the appendix. All of our simul results lie within 95% confidence interval. V. CONCLUSION Although provides seamless handoff of the MN its route optimiz introduces packet loss problem during the handoff. In this paper, we have proposed a scheme for reducing this packet loss. In our proposed scheme, the probability of departure of the MN from the current loc is computed at the CN. If it is greater than or equal to a threshold value, CN starts sending the data packets to the both HA and MN. HA receives the data packets coming from CN and stores the data packets in the buffer. HA forwards the buffered data packets to the current loc of MN when the HA receives a BU message from the MN containing a new care of address. As a result, the packet loss due to the handoff of the MN from one foreign network to another foreign network is reduced. Simul results show that our proposed solution provides significant improvement in case of reducing the packet loss in. We also measured the end-to-end delay and network overhead. In terms of end-to-end delay our scheme performs the same as but poor compared to H. H also suffers from fewer network overhead compared to our scheme. Our scheme, however, outperforms in terms of network overhead. Presently, our scheme supports the host mobility only. In future we will extend our scheme to support network mobility (NEMO). REFERENCES [1] Charles P., IP mobility support for IPv4, IETF RFC 3344, pp. 2-59, August 22. [2] Koodli R. S. and Perkins C. E., Mobile Inter-Networking with IPv6: Concepts, Principles and Practices, John Wiley & Sons, Inc.,Hoboken, New Jersey, July 27. [3] Johnson D., Perkins C., Arkko J. and Ericsson, Mobility Support in IPv6, IETF RFC-3775, pp. 5-79, June 24. [4] Hampel G. and Klein T., Mobile IPv6 Route Optimiz without Home Agent, draft-hampel-mextro-without-ha-, pp. 2-9, February 211. [5] Ivov E. and Noel T., An Experimental Performance Evalu of the IETF F Protocol over IEEE WLANS, In the proceedings of Wireless Communics and Networking Conference, IEEE Communics Society, pp , April 26. [6] Koodli R., Fast Hanover for Mobile IPv6, IETF RFC 468, pp. 3-37, July 25. [7] Soliman H., Catelluccia C., Malki K. E. and Bellier L., Hierarchical mobile IPv6 Mobility management, IETF RFC 414, pp. 3-2, August 25. [8] Jung H., Kim E., Yi J. and Lee H., A Scheme for Supporting Fast Handover in Hierarchical Mobile IPv6 Networks, Electronics and Telecommunics Research Institute Journal, vol. 27, no. 6, pp , December 25. [9] Yoo H.S., Tolentino R. S., Park B., Chang B.Y. and Kim S.H., ES-FH:An Efficient Scheme for Fast Handover over HMIPV6 Networks, Internal Journal of Future Gener Communic and Networking, vol. 2, no. 2, pp , June 29. [1] Chen-wen W. and Ping W., Improved Fast Handover Scheme for Hierarchical Mobile IPv6, In the proceedings of 4 th Internal Conference on Computer Science and Educ, pp , July 29. [11] Zhuang L., Wang C. B. and Zhang Y., Research of an Improved Mobile IPv6 Smooth Handoff Technology, In the proceedings of the Third Internal Symposium on Electronic Commerce and Security Workshops (ISECS 1) Guangzhou, pp , July 21. [12] Al-Farabi M. K. and Kabir H. M., Reducing Loss in Mobile IPv6, In the proceedings of 14 th Internal Conference on Computer and Inform Technology (ICCIT 211), pp December, 211. [13] Zaki M S. and Razak A. S., Mitigating Loss in Mobile IPv6 Using Two-Tier Buffer Scheme, CSL, ISSRES, vol. 3(2), pp. 1 1, June 211. [14] Pack S. and Choi Y., Performance Analysis of Fast Handover in Mobile Ipv6, PWC 23, LNCS 2775, pp , 23. [15] Gupta S., Sharma A. and Chowdhary M., An Improved Framework for Enhancing QoS in, Internal Journal on Computer Science and Engineering (IJCSE), vol. 3, no. 2, pp , February 211.

11 1922 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER 212 [16] Gundavelli S., Leung K., Devarapalli V., Chowdhury K. and Patil B., Proxy Mobile IPv6, IETF RFC 5213, pp. 4-82, August 28. [17] Jianfeng G., Huachun Z., Zhiwei Y., Yajuan Q. and Hongke Z., Implement and analysis of proxy, Wireless Communics and Mobil Computing, vol. 11, no. 4, pp , April 211. Md. Humayun Kabir has been working as a Professor in Computer Science and Engineering (CSE) Department of Bangladesh University of Engineering and Technology (BUET). He has received his Ph.D. degree in Computer Science from the University of Victoria, BC, Victoria, Canada in 25 and his both Masters and Bachelor degrees in CSE from BUET in the year of 1998 and 1993 respectively. His major research interests lie in computer networks, multimedia streaming, media encoding, and distributed systems. He has authored numerous internal journal and conference papers in these areas. He has started his teaching and research career from Khulna University in He has been teaching and researching in BUET from Khan Md. Al-Farabi has been working as an Assistant Professor in Computer Science Department of American Internal University-Bangladesh (AIUB). He has received his Bachelor degree in Computer Engineering from AIUB in the year of 26 and his Masters degree in Computer Science and Engineering (CSE) from Bangladesh University of Engineering and Technology (BUET) in the year of 211. His major research interests lie in computer networks, particularly in Mobile IPv6. APPENDIX TABLE 1 PACKET LOSS WITH MN: CN: FR (4:45:25) USING HUMAN WALKING SPEED Hours s , , , , , 13.6 TABLE 2- PACKET LOSS WITH MN: CN: FR (65:7:45) USING HUMAN WALKING SPEED Hours s , , , , ,51.5 TABLE 3 PACKET LOSS WITH MN: CN: FR (4:45:25) USING CAR SPEED Hour s , , , , , TABLE 4 PACKET LOSS WITH MN: CN: FR (65:7:45) USING CAR SPEED Hours at Confidenc ions e , 1.62 TABLE 5 PACKET LOSS WITH MN: CN: FR (4:45:25) DUE TO ONLY MOBILITY Spee d (m\s) , , , , , , , , , , , , , , , , , , ,53.67

12 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER TABLE 6 PACKET LOSS WITH MN: CN: FR (65:7:45) DUE TO ONLY MOBILITY Spee d (m\s) Deviatio n( SD) , , , , , , , , , , , , , , ,37.5 TABLE 7 PACKET LOSS WITH MN: CN: FR (4:45:25) DUE TO MOBILITY BIT ERROR, CONGESTION Spee d (m\s) , , , , , , , , , , , , , , ,231.9 TABLE 8 PACKET LOSS WITH MN: CN: FR (8:85:65) DUE TO MOBILITY BIT ERROR, CONGESTION Spee d (m\s) Deviatio n , Spee d (m\s) TABLE 9 END-TO-END DELAY WITH MN: CN: FR (15:2:1) Spee d (m\s) TABLE 1- END-TO-END DELAY WITH MN: CN: FR (65:7:45) Deviatio n , , , , , , , , , , , , , , ,7.5.51, , , ,5.56.9,6.5.98, , , , , , , , , , , , , , , , ,9.65

13 1924 JOURNAL OF NETWORKS, VOL. 7, NO. 12, DECEMBER , , , , , , ,1.14 TABLE 11 NETWORK OVERHEAD WITH MN: CN: FR (4:45:25) Hour s at ion , , , , , Hour s TABLE 12 NETWORK OVERHEAD WITH MN: CN: FR (6:7:45) , , , , ,452.7