Guolong Zhu

Design of survivable WDM network using multigranularity p-cycles

In this paper, a new type of p-cycles, multi-granularity flow p-cycles (MFP), is presented. A two-step approach is developed for the design of MFP with span failure recovery. Our simulation results show that MFP are more capacity-efficient than conventional span-protecting p-cycles (SP) and flow p-cycles (FP). The impacts of network topology on performance of SP, FP and MFP are evaluated. In this paper, we also propose a new p-cycle pre-selection strategy. Results show that our strategy is more efficient than two existing pre-selection strategy in p-cycle networks.

A Totally Shared Optical Packet Switch: Dimensioning, Control Algorithm and Performance

In this paper, a novel optical packet switch is proposed, which uses a set of shared fiber delay lines (FDLs) and a set of shared tunable wavelength converters (TWCs) to resolve optical packet contentions. In addition, two control algorithms, i.e., Fiber-First (FF) and Wavelength-First (WF), are proposed to schedule optical packets. Performance of the novel switch is evaluated by means of simulation experiments. Simulation results show that based on either of these two control algorithms, the switch can achieve super performance without employing a lot of FDLs and TWCs. Moreover, the performance of FF and WF is compared. Detail analyses are also given in this paper.

A novel optical packet switch: control algorithm and performance

In the paper, a new optical packet switch is proposed, which uses shared WDM buffers (fiber delay-lines) and shared tunable wavelength converters (TWCs) as contention resolution. In each fiber delay-lines, many wavelengths can be used to buffer packets at the same time. The shared TWCs have two kinds of functions, either as translators for free wavelengths in destination output fibers, or as translators for free wavelengths in the feedback FDLs. Based on this architecture, a lower packet loss rate can be achieved without the need of deploying a large number of FDLs and TWCs. The performance of the new architecture has been extensively studied by means of simulation experiments.

Influence of packet scheduling algorithms on optical packet switch

This paper focuses on the problem of buffering performance optimization for optical packet switch with shared WDM (Wavelength Division Multiplexing) optical buffers. For this purpose, several packet scheduling algorithms are proposed to make full use of buffering resources. Influences of these algorithms on optical packet switch are evaluated by simulation experiments. Simulation results show that under different traffic load, different packet scheduling algorithms should be adopted. In addition, the performance of optical buffers also depends on the granularity of FDL.

Dynamic traffic grooming using hop constraint lightpath establishment approach

This paper considers the dynamic routing issues in WDM grooming networks. Given network resources, a major objective of a routing algorithm is to minimize the blocking probability of connection requests. Wavelengths and transceivers are usually limited resources in a network. The way to use these resources directly determines the network performance. So the challenge is how to use wavelength resources efficiently while keeping higher transceiver-utilization efficiency. To solve this problem, we develop an approach called Hop Constrain Lightpath Establishment Approach (HCLEA). The main idea of HCLEA is to guide the routing algorithms not to create inefficient long lightpaths. Simulation results show that HCLEA does improve the network performance in terms of transceiver-utilization efficiency, wavelength-utilization utilization, and bandwidth blocking ratio.

Performance improvement for optical packet switch with shared buffers

In this paper, an inner wavelength method (IWM) is proposed to enlarge buffering capacity of shared FDL-buffers. In addition, an optical packet switch called Extended shared buffer type optical packet switch (Extended SB-OPS) is proposed to realize the inner wavelength method. In order to further improve performance of Extended SB-OPS, a greedy algorithm based on inner wavelength method (GA-IWM) is introduced. The performance of Extended SB-OPS is evaluated by simulation experiments.

Routing algorithms in IP/WDM networks based on hop-constraint lightpath establishment approach

To achieve higher resource utilization in IP/WDM networks, this paper develops an approach called hop-constraint lightpath establishment approach (HCLEA) to improve existing routing algorithms. HCLEA prevents the routing algorithm from creating long lightpaths with low efficiency. Simulation results show that HCLEA can achieve a significant improvement in terms of resource utilization and bandwidth blocking ratio.

Joint network design in multilayer networks

The demand to carry large amount of data as fast and as reliably as possible is continuously increasing, in parallel with formation of the information society. Nowadays, Fiber optic cables using Wavelength Division Multiplexing (WDM) are used to provide huge transport capability to support such demand effectively and economically. Each link is able to carry huge amount of traffic, thus a possible failure causes loss of tremendous data. So network survivability is highly required for such a high speed and huge capacity network. The operation of the modern telecommunication network is based on a multi-layer structure. The major reason of this multi-layer is the multiplexing hierarchy for efficient use of transmission facilities and the convenience of service and facility management. The most common example of multi-layer telecommunication network is the ATM over SDH over WDM configuration. This work investigates to the survivability of such multi-layer networks, and an integrated spare capacity dimensioning scheme, joint network design (JND) method, is proposed. Compared with single layer design (SLD) method, JND is bandwidth efficient and cost effective. The configuration problem of multi-layer fault tolerant networks is formulated as an Integer Linear Programming model. We also present a genetic algorithm approach for large networks whose size makes the ILP model difficult to use.

Performance of an optical packet switch with shared WDM buffers and shared tunable wavelength converters under bursty traffic conditions

In the paper, a novel optical packet switch is proposed, which uses shared WDM buffers (fiber delay-lines) and shared tunable wavelength converters (TWCs) as contention resolution. The shared TWCs have two kinds of functions, either as translators to translate contending wavelengths into free wavelengths in the destination output fibers, or as translators to translate contending wavelengths into available wavelengths in the shared FDLs. Based on this architecture, a low packet loss rate can be achieved without the need of deploying a large number of FDLs and TWCs. The performance of the novel architecture is extensively studied by means of simulation experiments, where bursty traffic model is assumed.

An improved method for guaranteed shared protection in WDM optical networks

Previous dynamic resource allocation method (separate path selection, SPS) for a survivable network is always separated into two steps, that is, determine a primary path first and then select a backup path for the primary path. In this paper we analyze the drawback of the traditional SPS technique and propose an efficient shared protection method called M/spl I.bar/SPS. Instead of rejecting an arrival call immediately when a backup lightpath for the optimal primary lightpath cannot be found, M/spl I.bar/SPS continue to try the sub-optimal one until a legal primary-backup pair can be selected. We apply M/spl I.bar/SPS to CERNET/spl I.bar/Like and NSFNET networks. Simulation results show that M/spl I.bar/SPS improves the network performance remarkably.