Giwon Lee

Optimal Flow Distribution in Service Function Chaining

Service function chaining (SFC) enables the creation of composite network services that consist of an ordered set of service functions. For scalable and fault-tolerant SFC services, multiple service function instances should be deployed across networks and incoming flows should be distributed to multiple service function instances appropriately. In this paper, we formulate the flow distribution problem in SFC under resource constraints and evaluate its optimal solution in a realistic network topology generated by the GT-ITM topology generator. Simulation results reveal that the optimal solution can reduce the total flow latency significantly.

Timer-Based Bloom Filter Aggregation for Reducing Signaling Overhead in Distributed Mobility Management

Distributed mobility management (DMM) is a promising technology to address the mobile data traffic explosion problem. Since the location information of mobile nodes (MNs) are distributed in several mobility agents (MAs), DMM requires an additional mechanism to share the location information of MNs between MAs. In the literature, multicast or distributed hash table (DHT)-based sharing methods have been suggested; however they incur significant signaling overhead owing to unnecessary location information updates under frequent handovers. To reduce the signaling overhead, we propose a timer-based Bloom filter aggregation (TBFA) scheme for distributing the location information. In the TBFA scheme, the location information of MNs is maintained by Bloom filters at each MA. Also, since the propagation of the whole Bloom filter for every MN movement leads to high signaling overhead, each MA only propagates changed indexes in the Bloom filter when a pre-defined timer expires. To verify the performance of the TBFA scheme, we develop analytical models on the signaling overhead and the latency and devise an algorithm to select an appropriate timer value. Extensive simulation results are given to show the accuracy of analytical models and effectiveness of the TBFA scheme over the existing DMM scheme.

FW-DAS: Fast Wireless Data Access Scheme in Mobile Networks

In wireless data access applications, reduction of both the access latency and the wireless traffic volume is essential. In this paper, we propose a fast wireless data access scheme (FW-DAS) for wireless data access applications in which data objects are frequently updated and fast access to data objects is indispensable. In FW-DAS, different operation modes are defined depending on the data object popularity, and only popular data objects are proactively pushed to the access point/base station to minimize the access latency while mitigating the traffic load over the wireless link. An analytical model for the access latency is developed and an operation mode selection algorithm is introduced to reduce the access latency. Extensive simulation results show the effects of access-to-update ratio, data popularity, cache size, data object size, and wireless bandwidth. Analytical and simulation results demonstrate that FW-DAS can reduce the access latency with reasonable traffic load compared with poll-each-read (PER)/callback (CB) and their combinations.

Optimized and distributed data packet forwarding in LTE/LTE-A networks

Recently, a data packet forwarding scheme between evolved node Bs (eNBs) in long-term evolution (LTE)/LTE-advanced (LTE-A) networks has been proposed to reduce the signaling overhead and delay incurred in the data path switching scheme. However, the conventional data packet forwarding scheme suffers from the increased delay when the length of the data packet forwarding chain is inappropriately long. To attain the optimal handover performance in LTE/LTE-A networks, we propose an optimized and distributed data packet forwarding scheme where an optimal length of the forwarding chain is obtained by a Markov decision process (MDP). Numerical results demonstrate that the proposed scheme achieves the optimal and adaptive performance in diverse network environments.

Fast wireless data access scheme in wireless networks

For wireless data access applications where objects are frequently updated and fast access to objects is required, we propose a fast wireless data access scheme (FW - DAS), which extends the callback (CB) scheme to minimize the access latency and combines it with the poll each read (PER) scheme to mitigate the traffic load over the wireless link. Extensive simulations are carried out to show the effects of operation mode, access-to-update ratio, data popularity, and cache size. Simulation results show that FW-DAS can reduce the access latency with reasonable traffic load compared with PER/CB and their combinations.

Optimal middlebox function placement in virtualized evolved packet core systems

Current evolved packet core (EPC) systems in LTE/LTE-A networks suffer from the exponentially increased mobile traffic and thus research on new EPC architectures is ongoing. In this paper, we introduce a virtualized EPC (vEPC) system where middlebox functions of the existing EPC systems are implemented in virtualized software modules and the virtualized software modules operate over selected physical service nodes. To minimize the impact of the increased transmission cost in vEPC, the optimal placement of middlebox functions is also investigated. Numerical results demonstrate that the proposed scheme can achieve lower packet transmission cost than the conventional one.

Efficient delta synchronization algorithm in mobile cloud networks

In mobile cloud applications where the data is shared by multiple mobile users, it is essential to provide the consistency among mobile users by means of synchronization algorithms. In particular, if the data is frequently updated and the number of mobile users sharing the data is large, the synchronization traffic can be significant. In this paper, we propose an efficient delta synchronization (EDS) algorithm that aggregates the updated data to reduce the synchronization traffic and synchronizes the aggregated one periodically to satisfy the consistency. To find out an optimal policy for the aggregation and the periodical synchronization, an optimization problem is formulated as a Markov decision process (MDP) and a value iteration algorithm is presented for computing the stationary deterministic policy. Numerical results demonstrate that EDS can choose an optimal action that strikes a balance between the reduction of the synchronization traffic and the satisfaction of the consistency.

Pseudonyms in IPv6 ITS communications: use of pseudonyms, performance degradation, and optimal pseudonym change

IPv6 developed as a next generation Internet protocol will provide us with safer and more efficient driving environments as well as convenient and infotainment features in cooperative intelligent transportation systems (ITS). In this paper, we introduce the use of pseudonyms in IPv6 ITS communications for preserving location privacy. We conduct qualitative study on the performance degradation due to the use of pseudonyms and quantitative analysis on the optimal pseudonym change interval. Numerical results demonstrate that an appropriate pseudonym change interval should be changed depending on the packet arrival rate, mobility rate, and security level.

Proxy-based aggregated synchronization scheme in mobile cloud computing

Recently, data sharing applications among mobile users in cloud computing platforms (e.g., Dropbox and Google Drive) are very popular. In such applications, a cloud server is responsible for synchronization among mobile users and thus the synchronization traffic can be significant when the data are frequently updated and shared by many mobile users. To address this problem, we propose a proxy-based aggregated synchronization (PAS) scheme in which the proxy server and the cloud server conduct localized and aggregated synchronizations, respectively. Preliminary simulation results demonstrate that PAS can reduce the synchronization traffic by 83.1%.