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Fair packet distribution on multi-interfaced mobile router for mobile networks.

1. Introduction

In the near future, airplanes, automobiles, and even people will carry entire networks of IP devices that connect to the Internet, which is called a mobile network. To deal with the mobility support of mobile networks, the Network Mobility (NEMO) techniques have been researched [1]-[6]. In the NEMO, the mobile router (MR) is capable of changing its point of attachment to the Internet without disrupting higher layer connections of attached devices. Therefore, mobile nodes (MNs) inside a mobile network are unaware of their network's mobility; however, they are provided with uninterrupted Internet access even when the network changes its attachment point to the Internet.

This paper considers the mobile network with a multi-interfaced mobile router (MMR) as shown in [4]-[6]. In addition, to consider the heterogeneous wireless network environment [7]-[9], the MMR can be assumed to have multiple heterogeneous wireless network interfaces. Therefore, the MMR establishes simultaneously multiple paths to the Internet through external wireless interfaces such as wireless metropolitan area network (WMAN) and wireless wide area network (WWAN) with high mobility and wide coverage. However, due to bandwidth constraints of multi-path through external wireless interfaces, the MMR might require a bandwidth aggregation to get sufficient bandwidth for MNs' demanding inside a mobile network. As shown in [10]-[14], the bandwidth aggregation requires generally several functions such as bandwidth estimation, packet distribution, packet reordering, etc. Among them, this paper focuses on the packet distribution scheme which effectively and fairly distributes packets on the appropriate end-to-end path through the corresponding network interface.

Therefore, this paper proposes a packet distribution scheme on the MMR with heterogeneous wireless network interfaces for mobile networks. Since the MMR is likely to have limited resources compared with a general router, the proposed scheme adopts the frame-based behavior that has lower complexity than the priority-based behavior. In the proposed scheme, the MMR with multiple heterogeneous wireless network interfaces effectively and fairly distributes packets over end-to-end multi-path. Each network interface is considered to have a distribution counter associated with the corresponding end-to-end path. This distribution counter is used to determine if a network interface has enough capacity to distribute packets on the corresponding end-to-end path. The distribution counter can get credits by the weighted capacity in bytes. The weighed capacity is operated at the byte level and is added more to the distribution counter with higher weight than that with less weight. On the other hand, the distribution counter is decreased by the size of packets being distributed. Thus, the distribution counter for each network interface is varied by distributed packets as well as weighted capacity.

In the proposed scheme, performance indices can be defined by ratio and amount of distributed packets, packet loss, and throughput. The capacity unit is shown to be a useful design parameter to make the performance of the proposed scheme as good as possible. To show how the capacity unit affects on performance indices, computer simulations are performed for some cases according to the capacity unit, which can provide practical guidance on the choice of a capacity unit. In addition, the proposed scheme is compared with the simple weighted packet distribution scheme. From simulation results, the proposed scheme is shown to be superior to the simple weighted scheme.

The paper is organized as follows. In Section 2, a fair packet distribution scheme on the MMR with heterogeneous wireless network interfaces is proposed for mobile networks. In Section 3, extensive computer simulations are performed. Finally, concluding remarks are made in Section 4.

2. Introduction

As shown in Figure 1, this paper considers the mobile network where the MMR has multiple heterogeneous wireless network interfaces. The MMR establishes multiple communication paths to the Internet through external wireless interfaces such as WMAN and WWAN with high mobility and wide coverage. In this mobile network environment, a fair packet distribution scheme on the MMR with heterogeneous wireless network interfaces is proposed for mobile networks.

[FIGURE 1 OMITTED]

2.1 Design Parameters

In the proposed scheme, the MMR distributes packets effectively and fairly on the appropriate end-toend path through the corresponding network interface. Each network interface is considered to have a distribution counter associated with the corresponding end-to-end path. This distribution counter is used to determine if a network interface has enough capacity to distribute packets on the corresponding end-to-end path. The distribution counter can get credits by the weighted capacity in bytes. The weighted capacity is defined by Weighted capacity = Capacity unit * Weight. The capacity unit in bytes is a useful design parameter and thus can affect on the performance of the proposed scheme. The weight is determined proportionately from the estimated available bandwidth of end-to-end paths. The weighed capacity is operated at the byte level and is added more to the distribution counter with higher weight than that with less weight. On the other hand, the distribution counter is also decreased by the size of packets being distributed. Thus, the distribution counter for each network interface is varied by distributed packets as well as weighted capacity.

2.2 Operation Procedure and Example

The operation procedure for each round is as follows. For the first path, packets are distributed when the distribution counter is greater than the incoming packet's size. If it is lower, the distribution counter is increased by the weighted capacity and then the incoming packet is distributed on the current path. Then the distribution counter is decreased by the size of packet being distributed. If the distribution counter is still lower than the incoming packet's size, the incoming packet held back until the proposed scheme moves on the next path. After visiting all paths, the round is finished. The above operation procedure in next round is repeated when there are incoming packets.

As an example, the MMR is assumed to have three heterogeneous wireless network interfaces and thus there are three communication paths. These paths are called the Green (high bandwidth), Yellow (medium bandwidth), Red (low bandwidth) paths, respectively. Since this paper focuses on the packet distribution scheme, available bandwidths for three paths through corresponding interfaces are assumed to have fixed weight ratio 4:2:1. The capacity unit is set by 256 bytes and thus these paths have weighted capacity 1024, 512, 256 bytes, respectively. All initial values of distribution counters, denoted by [DC.sub.gyr], and total amount of distributed packets, denoted by [ADP.sub.g,y,r], for three paths are set with 0. There are four kinds of packet type with different sizes such as 256, 512, 768, 1024 bytes.

As shown in Figure 2, incoming packets are waiting to be distributed to the most appropriate path. The 1st round is operated. At Green path, the weighted capacity is added and thus the distribution counter, [DC.sub.g], is 1024. Then, since the [DC.sub.g] is not less than the incoming packet's size (1024 bytes), the incoming packet 'A' is distributed to Green path and thus [DC.sub.g]=0. Currently, total amount of distributed packets to Green path, [ADP.sub.g], is 1024 bytes. At Yellow path, the weighted capacity is added and thus [DC.sub.y]=512. Then, since the [DC.sub.y] is not less than the incoming packet's size (256 bytes), the incoming packet 'B' is distributed to Yellow path and thus [DC.sub.y]=256. Currently, [ADP.sub.y]=256. At Red path, the weighted capacity is added and thus [DC.sub.r]=256. Then, since the [DC.sub.r] is still less than the incoming packet's size (768 bytes), move to Green path. Currently, [ADP.sub.r]=0. The 1st round is done as shown in Table 1. Then, the 2nd round is operated. At Green path, since the [DC.sub.g] is less than the incoming packet's size (768 bytes), the weighted capacity is added and thus [DC.sub.g]=1024. Then, the incoming packet 'C' is distributed to Green path and thus [DC.sub.g]=256. Currently, [ADP.sub.g]=1792. At Yellow path, since [DC.sub.y] is less than the incoming packet's size (512 bytes), the weighted capacity is added and thus [DC.sub.y]=768. Then, the incoming packet 'D' is distributed to Yellow path and thus [DC.sub.y]=256. Currently, ADP =768. At Red path, since [DC.sub.r] is less than the incoming packet's size (768 bytes), the weighted capacity is added and thus [DC.sub.r]=512. Then, Then, the incoming packet 'E' is distributed to Green path and thus [DC.sub.g]=0. Currently, [ADP.sub.r]=512. The 2nd round is done as shown in Table I. The operation procedure in next round is repeated when there are incoming packets.

2.3 Performance Indices and Useful Design Parameters

There can be four performance indices in the proposed scheme; ratio of distributed packets, amount of distributed packets, packet loss and throughput. Their objectives are described in Table II. Of course, the throughput can be improved as many packets are distributed. However, the improvement of the throughput does not have the meaning if the packet loss increases.

As mentioned before, the capacity unit is a useful design parameter to determine weighted capacity that affect on four performance indices mentioned before. Too big value of the capacity unit can introduce excessive credits for end-to-end paths, which means that network paths have enough credits to distribute packets. Thus, incoming packets are more likely to be distributed simultaneously on every path each round, which cannot provide fair distribution according to weights for network paths. Thus, the ratio of distributed packets can be degraded. In addition, since packets can be distributed too many over each end-to-end path, the performance for packet loss can be degraded. Of course, since packets are distributed too many over each end-to-end path, the throughput can be improved. However, as mentioned before, the improvement of the throughput does not have the meaning since the packet loss increases. On the other hand, too small value of the capacity unit can introduce deficient credits for end-to-end paths, which means that end-to-end paths do not have enough credits to distribute packets. Thus, incoming packets are less likely to be distributed on every paths each round, which can thus degrade the amount of distributed packets. In addition, since the amount of distributed packets over each end-to-end path is not much, the throughput can be degraded whereas the packet loss can decrease. Therefore, the important issue here is how to choose an appropriate capacity unit to make the performance of the proposed scheme as good as possible. Following computer simulations can provide practical guidance on the choice of the capacity unit.

3. Performance Evaluations Through Computer Simulations

In this section, computer simulations are performed to evaluate the proposed scheme. The MMR is assumed to have three heterogeneous wireless network interfaces and thus there are three communication paths. Available bandwidths for three paths through corresponding interfaces are assumed to have fixed weight ratio 3:2:1. To make a clearer verification, 30 simulations are performed and each simulation generates randomly incoming packets with four kinds of packet type with different sizes such as 256, 512, 768, 1024 bytes

3.1 Performance Evaluation According to Capacity Unit

To show how the capacity unit affects on performances indices, computer simulations are performed for three cases according to capacity units such as 192, 256, 320 bytes, respectively. Table III and Table IV show average values for four performance indices for each path. As mentioned before, too big value of the capacity unit cannot provide fair distribution according to weights for each network paths. That is, the ratio of distributed packets is shown to be degraded. In addition, since packets can be distributed too many over each end-to-end path, the performance for packet loss can be degraded. Although the throughput is shown to be improved, the improvement of the throughput does not have the meaning since the packet loss increases. On the other hand, too small value of the capacity unit degrades the amount of distributed packets. In addition, since the amount of distributed packets over each end-to-end path is not much, the throughput is shown to be degraded whereas the packet loss is shown to decrease. The simulation result is shown to be more favourable than other cases when the capacity unit is 256 bytes.

3.2 Performance Comparison

The proposed packet distribution scheme is compared with the simple weighted packet distribution scheme. The simple weighted scheme distributes packets according to only the weight ratio of network paths without the distribution counter and the capacity unit. That is, the simple weighted scheme does not consider the size of incoming packets unlike the proposed scheme. As shown in Table V, the proposed scheme is shown to be superior to the simple weighted scheme for the amount of the distributed packets and comparable for the ratio of distributed packets. As shown in Table VI, the proposed scheme is shown to be inferior slightly to the simple weighted scheme for the packet loss. The proposed scheme is shown to be superior to the simple weighted scheme for the throughput. This observation is from that the proposed scheme distributes packets with the consideration of incoming packets size using the distribution counter and the capacity unit. On the other hand, the simple weighted scheme does not since long-sized packets can be distributed on specific network interface unfairly.

4. Conclusions

In this paper, the fair packet distribution scheme on the MMR with multiple heterogeneous wireless network interfaces has been proposed for mobile networks. The fair packet distribution scheme makes the MMR distribute effectively and fairly incoming packets over end-to-end multi-path. Each network interface has been considered to have a distribution counter associated with corresponding end-to-end path. This distribution counter varied by both weighted capacity and distributed packets has been used to determine if a network interface has enough credits to distribute incoming packets on corresponding end-to-end path. The capacity unit has been shown to be a useful design parameter to make the performance of the proposed scheme as good as possible. Computer simulations have shown that the proposed scheme can distribute well randomly incoming packets over end-to-end multi-path and can outperform the simple weighted packet distribution scheme.

References

[1] E. Perera, V. Sivaraman, and A. Seneviratne, "Survey on network mobility support," ACM SIGMOBILE Mobile Computing and Communications Review, vol. 8, no. 2, pp. 7~19, 2004.

[2] P. Thubert, A. Petrescu, R.Wakikawa, and V. Devarapalli, "Network Mobility (NEMO) Basic Support Protocol," IETF RFC 3963, Jan 2005.

[3] C. Ng, "Analysis of multihoming in network mobility support," IETF RFC 4980, October 2007.

[4] L. Suciu, J-M. Bonnin, K. Guillouard, and T. Ernst, "Multiple network interfaces management for mobile routers," in In 5th International Conference on ITS Telecommunications (ITST), 2005, pp. 347~351.

[5] K. Shima, Y. Uo, N. Ogashiwa, and S. Uda, "Operational experiment of seamless handover of a mobile router using multiple care-of address registration," Journal of Networks, vol. 1, no. 3, pp. 23~30, 2006.

[6] X. Chen, H. Zhou, Y. Qin, and H. Zhang, "Multiinterfaced mobile router scheme and enhanced path selection algorithm," in Proc. of the International Conference on Telecommunications (ICT), 2008, pp. 1~8.

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[8] M. Kassar, B. Kervella, and G. Pujolle, "An overview of vertical handover decision strategies in heterogeneous wireless networks," Computer Communications, vol. 31, no. 10, pp. 2607~2620, 2008.

[9] F. Kronestedt, A. Furuskar, S. Landstrom, L. Falconetti, and K. Johansson, "Heterogeneous networks--Increasing cellular capacity," Ericsson Reivew, vol. 88, no. 1, pp. 4~9, 2011.

[10] K. Chebrolu and R.R. Rao, "Bandwidth aggregation for real-time applications in heterogeneous wireless networks," IEEE Trans. on Mobile Computing, vol. 5, no. 4, pp. 388~403, 2006.

[11] M. Balakrishnan, R. Mishra, R.R. Rao, "Bandwidth aggregation for real-time applications in heterogeneous wireless networks," in Proc. of 2nd International Conference on Broadband Networks (BroadNets), 2005, pp. 1541~1547.

[12] T. Taleb, J.C. Fernandez, K. Hashimoto, Y. Nemoto, and N. Kato, "A bandwidth aggregation-aware QoS negotiation mechanism for next-generation wireless networks," in Proc. of IEEE Global Telecommunications Conference (Globecom), 2007, pp. 1912~1916.

[13] C-M. Huang, C-C. Yang, H-Y. Lin, "A bandwidth aggregation scheme for member-based cooperative networking over the hybrid VANET," in Proc. of IEEE 17th International Conference on Parallel and Distributed Systems (ICPADS), 2011, pp. 436~443.

[14] D. Krishnaswamy, D. Zhang, S. Soliman, B. Mohanty, D. Cavendish, W. Ge, S. Eravelli, "Concurrent bandwidth aggregation over wireless networks," in Proc. of International Conference on Computing, Networking and Communications (ICNC), 2012, pp. 604~6010.

Pyung-Soo Kim (1,2)

(1) Center for Embedded Computer Systems, University of California, Irvine, CA 92697, USA

(2) Department of Electronic Engineering, Korea Polytechnic University pyungk@uci.edu
TABLE I. DISTRIBUTION COUNTERS AND TOTAL AMOUNT
OF DISTRIBUTED PACKETS

                            1st Round      2nd Round

Green Path    [DC.sub.g]    1024 [right    1024  [right
                            arrow] 0       arrow] 256
              [ADP.sub.g]   1024           1972

Yellow Path   [DC.sub.y]    512 [right     768 [right
                            arrow] 256     arrow] 256
              [ADP.sub.y]   256            768

Red Path      [DC.sub.r]    256            0
              [ADP.sub.r]   0              512

TABLE II. PERFORMANCE INDICES AND THEIR OBJECTIVES

Performance
Index         Objective

Ratio of      Distributing packets fairly according to the
distributed   weight ratio of each end-to-end path
packets

Amount of     Distributing packets as many as possible over
distributed   each end-to-end path
packets

Packet loss   Minimizing lost packets on each end-to-end
              path

Throughput    Maximizing the average rate of successful
              packet delivery on each end-to-end path

TABLE III. SIMULATION RESULTS : AMOUNT AND RATIO OF DISTRIBUTED
PACKETS

                   Amount of Distributed Packets          Ratio of
                       (Mbytes, Average)                 Distributed
Capacity                                                   Packets
Unit       Green Path   Yellow Path   Red Path   Total    (Average)

192           8.16         5.11         2.64     15.90   3.10:1.94:1
256          10.01         6.50         3.37     19.88   2.97:1.93:1
320           9.70         7.70         4.17     21.57   2.33:1.85:1

TABLE IV. SIMULATION RESULTS : PACKET LOSS AND THROUGHPUT

                        Packet Loss
Capacity
Unit       Green Path   Yellow Path   Red Path

192           7.8            6.9          7.7
256           8.0            9.0         10.0
320           8.0          970.0       2138.0

                         Throughput
Capacity
Unit       Green Path   Yellow Path   Red Path

192        2.17 (72%)   1.36 (68%)    0.70 (70%)
256        2.67 (89%)   1.73 (87%)    0.90 (90%)
320        2.58 (86%)   1.93 (97%)    111.97 (97%)

TABLE V. COMPARISON : AMOUNT AND RATIO OF DISTRIBUTED PACKETS

                  Amount of Distributed Packets             Ratio of
                      (Mbytes, Average)                   Distributed
                                                            Packets
Mechanism   Green Path   Yellow Path   Red Path   Total    (Average)

Proposed
Mechanism     10.01          6.50        3.37     19.88   2.97:1.93:1

Simple
Weighted       8.47          5.65        2.83     16.95   2.99:1.99:1

TABLE VI. COMPARISON : PACKET LOSS AND THROUGHPUT

                                  Packet Loss

Mechanism            Green Path   Yellow Path   Red Path

Proposed Mechanism      8.0           9.0         10.0
Simple Weighted         7.8           7.3         8.30

                                  Throughput

Mechanism            Green Path   Yellow Path   Red Path

Proposed Mechanism   2.67 (89%)   1.73 (87%)    0.90 (90%)
Simple Weighted      2.26 (75%)   1.50 (75%)    0.76 (76%)

Figure 2. Incoming packets

[right arrow] Incoming Packets

E         D       C       B        A

(512)   (512)   (768)   (256)   (1024)
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Author:Kim, Pyung-Soo
Publication:International Journal of Communication Networks and Information Security (IJCNIS)
Article Type:Report
Date:Aug 1, 2012
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