Jin Seek Choi

Dimensioning Burst Assembly Process in Optical Burst Switching Networks

Suitably aggregated data burst enhances link utilization and reduces data processing complexity of optical transport networks rather than just transmitting each bursty input traffic from access networks. This data burst generation method is called as a burst assembly process and has two assembly parameters, timer and threshold, for regulating burst release time and burst size. Since the traffic characteristics of data burst generated at the burst assembler may affect network performance, the decision of burst assembly parameters should be carefully designed. Thus, in this paper we study the dimensioning burst assembly process to find the burst assembly parameter values satisfying target performance. For this purpose, we first analyze timer-based and threshold-based burst assembly processes, respectively. As constraints on the dimensioning burst assembly process, we consider the following performance metrics: 1) processing delay of control packet, 2) burst loss at control plane, and 3) link utilization. Based on these constraints, a decision mechanism of the burst assembly parameters is proposed. From numerical analysis, we suggest a possible lower boundary value for the burst assembly parameters satisfying the target burst loss rate and delay time at the control plane.

A new distributed location management algorithm for broadband personal communication networks

We propose an efficient location management algorithm for broadband personal communication networks (PCNs) which reduces the complexity of network signaling and delay due to database access when locating a portable station (PS). Previous works on updating and search algorithms for personal communications have concentrated on the access delay due to signaling network traffic only. But, with the advances in fiber optic technology, it will be possible to provide the capacity of signaling network on the order of several Mbps in broadband PCNs. Thus it may be more important to simplify the signaling procedure and reduce the number of database accesses for mobility management at the cost of some increase of signaling traffic. In the proposed algorithm, we first remove all visitor location registers (VLRs) in order to achieve the simplicity of signaling procedure. Thus, only home databases for mobility management are distributed in a global network, and each database keeps only the current locations of PSs initially registered in its management area. It can solve the problem of requiring an impractically large database in a centralized database structure by distributing home location registers (HLRs) while maintaining the simplicity of mobility management and reducing database loads. This algorithm has a simple signaling procedure, and reduces database operations when compared to hierarchical algorithms as network switching hierarchy increases or relocation and calling rate increase. >

Power and cost reduction by hybrid optical packet switching with shared memory buffering

The power consumption of a network becomes a critical performance metric for a petabit-per-second scale Internet, in addition to the system cost. We investigate the power and cost efficiency of all-optical and electrical technologies to understand the design principle for petabit-scale hybrid optical switch nodes for optical packet and burst switching. In order to achieve an efficient hybrid design, we point out the interesting observation that the use of long packets switched by passive-medium photonic switches can substantially reduce power consumption and system cost. For contention resolution, shared electronic memory buffers are more effective and power efficient than fiber delay line buffers. An empirical optimization exhibits that a traditional all-optical solution is not the best choice for power and cost efficiency. Using passive-medium photonic switches with electronic memory buffers, we can introduce a substantial savings in power and cost, approximately half of those of commercially available optical cross-connect systems, with a packet loss rate as low as 10-6.

A dynamic wavelength allocation scheme with status information for fixed- and variable-length messages

We propose a new multiple access protocol to support both fixed- and variable-length messages, in a wavelength division multiple access (WDM) based local network using a passive star coupler. The proposed protocol is the dynamic wavelength allocation scheme based on a contention-based reservation protocol. In the proposed protocol, a whole message can be transmitted after the first reservation of the control channel is successfully completed. To reserve the subsequent slots, the status information is used, instead of the control channel. Moreover, the data channels are dynamically allocated to the nodes that win the reservation. Thus, the proposed protocol can reduce the probability of the control and data channel conflicts, and uses the same data channel while transmitting a whole message.

Performance Analysis of a Bandwidth Guaranteed Medium Access Control Protocol for WDM Local Networks

In this paper, we propose and analyze a bandwidth guaranteed medium access control protocol for broadcast-and-select WDM local networks with a star topology. The proposed protocol is based on a combination of contention and dedicated reservation mechanisms for time slotted WDM networks. Every node accesses the data channel by transmitting request packets in minislots on a separate control channel. There are two types of minislots; dedicated minislots and contention minislots. Nodes requiring bandwidth guarantees, called guaranteed nodes, use dedicated minislots that are assigned by the centralized control node. The remaining nodes, called random-access nodes, share contention minislots using a distributed random access mechanism. The dedicated minislots can guarantee a minimum bandwidth for the guaranteed nodes. The contention minislots enable on-demand services at the optical layer and achieve good fairness for the remaining bandwidth. Here, the data channels are dynamically assigned to the minislots successfully returned on a first-come-first-served (FCFS) basis. This protocol can combine the best of centralized and distributed access protocols such as simplicity, efficiency, and flexibility. We analyze the maximum throughput and verify the results by simulation.

Design and performance analysis of hierarchical location management strategies for wireless mobile communication systems

In this paper, we propose three hierarchical location management strategies for wireless mobile communication systems. The first one is home server first (HSF) scheme in which callees location is queried at callees home location server first. Next, we propose least-common-ancestor server first (LSF) scheme in which a search starts at the least-common-ancestor server of callers current location and callees home server. Finally, we propose distributed LSF in which the location management is made on 2-layered distributed structure. We evaluate the performance of the proposed schemes and compare it with that of another hierarchical scheme proposed by Wang (J.Z. Wang, A fully distributed location registration strategy for universal personal communication systems, IEEE J. Select. Areas Commun., 11(6) (1993) 850-860) and IS-41-based scheme. It is shown that the proposed schemes have reduced location management cost and that the cost is less affected by the increment of communication cost than the compared schemes.

Mobile location management strategy with implicit location registration

We propose a new location management strategy by introducing the concept of implicit location registration. Implicit location registration is triggered whenever a transaction occurs between the backbone network and a mobile terminal. The mobiles most recently notified cell and its neighboring cells are paged to locate a mobile. It is shown that the proposed strategy has the lower paging cost than the simultaneous paging scheme. In addition, the proposed strategy can further reduce the paging cost when the terminal mobility is low and when there are many transactions between the backbone network and mobile terminals.

LMA initiated route optimization protocol for improving PMIP handover performance

We propose a Local Mobility Anchor (LMA) initiated route optimization protocol for a smooth transition from the old optimized path to a new optimized path after handover in Proxy Mobile IP (PMIP). The LMA initiated protocol can reduce the handover latency and achieve fast recovery of the optimized path after handover. As a result, the proposed protocol solves the out-of-sequence delivery problem during the route optimization procedure.

Design and Implementation of a Stateful PCE-Based Unified Control and Management Framework for Carrier-Grade MPLS-TP Networks

This paper presents the design and evaluation of a generalized topology discovery, operational monitoring, and provisioning (G-TOP) controller for a carrier-grade transport network. The G-TOP controller is a vendor-specific extension of the stateful PCE that integrates network topology discovery, path computation, and provisioning functions, but decouples the switch specific management framework. The G-TOP protocol enables the G-TOP controller to collect topology information, set up LSPs, and monitor state both from and to the management framework in a unified way. To validate the feasibility of the proposed framework, the author implemented a testbed using a multi-protocol label switching transport profile (MPLS-TP) switches and performed experimental testing. The experimental results show that the centralized control framework reduces provisioning time by approximately 68 ms and the autonomous management framework reduces fault recovery time by approximately 27 ms, while reducing the traffic load on the controller by several orders of magnitude compared to the OpenFlow approach.

Design and implementation of a PCE-based software-defined provisioning framework for carrier-grade MPLS-TP networks

In this paper, we present a path computation element (PCE)- based provisioning framework for carrier-grade multi-protocol label switching-transport profile (MPLS-TP) networks. In the proposed framework, a centralized PCE integrates the service function as well as the path provisioning function into a unified provisioning controller. The service function allows the provisioning manager to initiate the establishment of a label-switched path (LSP). The provisioning function computes an optimal path, sets up and maintains the LSP in a unified way while directly configuring the LSP over the switches. The management function, as a separation from the provisioning function, can fully utilize the MPLS-TP switch to keep monitoring the performance of the provisioned LSP tunnels in a distributed way. The balanced partitioning of service provisioning and management functions reduces traffic load on the controller and improves the scalability. The software-defined provisioning control using an extended PCE communication protocol enables the cooperation between them to monitor and customize the LSPs flexibly and efficiently. We implement and show that the proposed framework not only simplifies the provisioning procedure with a single instance, but reduces the provisioning time in a MPLS-TP test bed.