In this paper, a new scheme to mitigate the connection setup time overheads in distributed control schemes for wavelength-routed optical networks is proposed. In this scheme, we consider the reconfiguration delay of switch fabrics in the distributed signaling protocols, which designated as the signaling with switch fabric status (SWFS). Based on the reconfiguration information being carried by signaling messages along with wavelength availability information,
distributed wavelength assignment algorithm at the destination node will select a wavelength with the minimal switch reconfiguration delay along the lightpath to shorten average connection setup time. Simulation results indicate that the first-fit algorithm with switch status (S-FF) and random algorithm with switch status (S-RM) have the shorter setup time, lower switch ratio as well as better blocking performance than those of classic schemes. Especially, the proposed scheme significantly reduces the number of switch fabrics that need to be reconfigured. Moreover, we investigate the effect of number of add/drop ports of optical cross-connects (OXCs) on the blocking performance of the scheme. We find that when the number of add/drop ports of OXCs is larger than a base boundary, the network may achieve almost the best blocking performance of the distributed wavelength provisioning.
One of the challenges to dynamically set up a lightpath is to develop efficient control schemes in control as well as the management of the distributed-controlled optical networks. In networks with highly dynamic traffic loads, longer lightpath setup time may result in higher blocking probability and serious degradation of the network performance. In this paper, we propose a novel distributed signaling protocol designated as signaling with switching fabric status (SWFS). In this scheme, we consider the switch fabric configuration performing distributed signaling as well as routing and wavelength assignment. We forward the signaling request messages with available wavelength sets as well as the extra switching status for each wavelength at each node in the paths between the source-destination (S-D) pairs. The extra switching status indicates if the switch fabric should be reconfigured to provide internal port connection for specified wavelength at the node. When the signaling message reaches the destination, a wavelength with minimal reconfiguration times in the available wavelength set will be selected to shorten the connection establishment time. A distributed discrete event simulation platform has been developed to evaluate the performance of SWFS. The simulation results show that our proposed technology has the shorter setup time and lower blocking probability than the traditional non-optimization signaling technology.
In Optical burst switching (OBS) networks, one important issue is how the performance will be affected by burst assembled from packets. In this paper, we study the fundamental statistic properties of Possion and Pareto traffic, such burst length distribution, inter-arrival time distribution and the switching performance with different aggregation schemes. The results show that the traffic will approach the Gaussian distribution of both kinds of traffic, but the aggregation operation has little effect on the heavy tail of Long Range Dependent traffic. The aggregation algorithm based on aggregation time degrades the loss performance of burst switch because burst arrivals easily concentrate a moment at the period of aggregation time window.
A new optical label scheme called Common optical SCM (Subcarrier Multiplexing) label method is proposed. The label paths are consisting of multiplex SCM paths with SCM/WDM technology, which separate from the data wavelength paths. These label paths are parallel and shared for any data wavelength path. We analyzed the modulation and transmission of SCM label channels and compared the bandwidth efficiency and switching performance of main several optical label schemes. The results show that because of no guard between label and data packets the bandwidth efficiency increases and the operation complexity decreases in common optical label schemes and multiple shared parallel SCM label channels can decrease the block probability of label packets.
One of challenges to efficient utilizing network resources is to design an effective lightpath teardown strategy in IP/MPLS optical networks. In the traditional integrated routing schemes, a lightpath is established optimally for a LSP request, but may not remain optimal for future requests. Releasing the suboptimal lightpath may free wavelength resources to prepare for new optimal lightpath establishment. In this paper, we proposed and evaluated three lightpath path strategies, threshold-based period-based and no lightpath teardown strategies in a comprehensive distributed simulation platform for IP-MPLS over optical networks within the generalized MPLS (GMPLS) framework. The simulation results show that TBLTS and PBLTS achieve shorter-length paths and at low load, and TBLTS outperforms the other two in terms of blocking probability. In addition, CR-LDP also can get significant performance advantages than RSVP-TE signaling protocol.
In this paper, a traffic-grooming problem for multi-granularity traffic of SDH/SONET in WDM grooming mesh networks is investigated. We propose a path select routing algorithm to solve this problem. The performances of this traffic grooming path select routing algorithm are evaluated in WDM grooming networks. Finally, we presented and compared the simulation results of this algorithm in dynamic traffic grooming WDM mesh networks with that of other algorithms.
Constraint-based routing algorithms are a key component to meet various requirements subjects to a set of constraints for bandwidth requests in the GMPLS-based optical networks. The purpose of GMPLS control plane is to provide an intelligent automatic end-to-end label switched path provisioning/signaling framework to support arbitrary bandwidth traffic. We developed a detailed simulation platform for an IP-over-MPLS-over-WDM network, so that extensive simulations are carried out to evaluate the network performance of various routing algorithms and routing strategies with RSVP-TE or CR-LDP signaling protocol in GMPLS-based IP/MPLS optical networks in terms of blocking probability. The simulation results show that the signaling protocol improves the network performance more significantly than multi-fiber configuration and CR-LDP signaling mechanism outperforms RSVP-TE in all cases. Furthermore, the LCF routing strategy also has better performance than LCL strategy.
In this paper, the objective was optimizing the port number with dynamic traffic grooming of SDH/SONET WDM mesh networks to give useful referenced data to networks design and the cost control of networks. The performances of different path select routing algorithms were evaluated in WDM grooming networks by considering traffic of different bandwidth requests. Finally, the results were presented and compared with in distributed-controlled WDM mesh networks.
In this paper, the dynamic distributed traffic-grooming problem in WDM optical mesh network is investigated. We give the proposal of the number optimization of wavelengths and ports are evaluated in a class of IP/WDM distributed nteworks. We presented and compared the performances of dynamic distributed traffic grooming in regular and irregular optical mesh networks, and give the optimized number of wavelengths and ports in different network condition.
A new loop output buffer architecture for optical packet switching is proposed. It is consisted of multiplex FDL loops, which are divided into k stages by k (M+1) x (M+1) switches. Using this architecture, a few FDL loops can provide large optical memories and get good packet-loss performance, and the delay performance can be improved by adding switches and buffer scheduling.
Internet backbone network is undergoing a large-scale transformation from the current complex, static and multi-layer electronic-based architecture to the emerging simplified, dynamic and single-layer photonic-based architecture. The explosive growth in the Internet, multi-media services, and IP router links are demanding the next generation Internet that can accommodate the entire traffic in a cost-effective manner. There is a consensus in current industries that IP over WDM integration technologies will be viable for the next generation of the optical Internet where the simplified flat network architecture can facilitate the networking performance and the networking management. In this paper, we firstly propose a novel node architecture-Terabit Optical Router (TOR) for building the next generation optical Internet and analyzes each key function unit of TOR including multi-granularity electrical-optical hybrid switching fabrics, unified control plane unit and so on. Secondly, we discussed the unified control plane unit of TOR in detailed Thirdly we describe our cost vs. performance analysis for various application of TOR. According to our evaluation carriers can get a cost reduction of more than 60 percent by using the TOR. Finally, we reach conclusions that TORs rather than OBS or BFR(Big Fat Router) routers, a cost effective multi-granularity switching and routing technique, are feasible to build the next generation Internet.
n this paper, we propose a G1VIPLS-based unified traffic engineering scheme in optical networks to cooperate at both optical layer and IP/MPLS layer achieving high efficiency of resource utilization. In WDM networks, end-to-end all-optical paths, called lightpath, can be setup between two edge optical routers. The set of lightpath comprise of the logical topology of optical networks. In IP/MPLS layer, a LSP is established on the logical topology. With the traffic increasing or decreasing, it is expected that the logical topology can adapt to traffic changes. When the traffic in a lightpath increases and becomes extremely heavy, allotting a new lightpath can partition some traffic and relieve the congestion. On the contrary, when the bandwidth utilization in a lightpath is very low, the lightpath may be released to free up its occupied resources. Based on this idea, a topology-adaptive scheme is proposed and two adjustable thresholds are introduced which are employed to control the frequency of lightpath setup or release. Finally, several key issues in unified traffic engineering are presented
A novel multistage optical cross-connect (OXC) that combined the advantages of three technologies of Space Division Switching (SDS), Wavelength Division Switching (WDS), and Optical Time-Division Multiplexing (OTDM) has been proposed. The structures of the first and second stages of a 2 X 2 and a 4 X 4 OXC have been presented. By means of the splitter and delivery (SAD) switch, it is cost-effective and fully modularized and very convenient to scale to n X n OXCs suitable for large-scale backbones.
Wavelength-division multiplexing appears to be the solution of choice for providing a faster networking infrastructure that can meet the explosive growth of the Internet. Future networks are expected to utilize the WDM technology for optical functionalities capable of handling multi-Teragabit signals and thus the cost, therefore it is very important that the Optical cross-connects (OXCs) and optical Add-drop Multiplexers (OADMs) have performed routing and switching capacities. Optical Packet Switch (OPS) technology allows us to rapidly deliver the enormous network bandwidth. OPS offers high-speed data rate and format transparency. But there are still many technologies and key components need to solve. In this paper we propose a novel architecture for OPS using Tunable Wavelength Converters (TWC) and Fiber Delay-Lines (FDLs). We use wavelength converters and demuxes connected with several FDLs that provide different delay periods. Input wavelengths can be tuned to different ones in order to acquire different delay periods. Wavelength converters are shown to improve the traffic performance of the switch blocks for both random and burst traffic. It can also provide contention resolution solution in wavelength and time domains. This architecture improves packet switching speed and significantly decreases the use of optical switches comparing with general architecture. Finally, the simulation results show that the packet blocking can be decreased.
Optical Label Switching (OLS) is one of the practical manners of optical packet switching. It is a main research domain in optical networks. The advantage of OLS is its bandwidth efficiency and ability to support various network devices. There are a lot of practical problems need to be resolved. Today, research into OLS technology has focused on key networking and hardware issues such as high-speed optical switch, optical storage component, and network nodes source distribution optimization algorithm. The optical Label Header contains header synchronizing bits, routing address bits, etc. Header reading and rewriting includes synchronizing, routing and checking technologies. So it is the key issue in the OLS, and has very important research and application values. In this paper, a novel proposed fabric scheme was discussed to achieve the function of the header reading and rewriting. It can be applied to the high-speed header reading and rewriting to satisfy the requirements of practical applications. The fabric scheme adopts a high-speed tunable laser and wavelength converter to rewrite the header. The high-speed tunable laser is based on Grated Coupler Sampled Reflector (GCSR) structure and the wavelength converter is based on Cross-Phase Modulation (XPM) in a Semiconductor Optical Amplifier (SOA) and a Mach-Zehnder Interferometer (MZI) structure. The synchronization of the packet in the node also be discussed.
Using the feature that the gain peak wavelength only depends on the pump wavelength, the multi-pump sources and their gain peak wavelengths can be considered as the input and output variables of the single layer feed-forward neural networks, and the optimal design for multi-pumped Raman Fiber Amplifier can be converted to a optimal problem of the single layer feed-forward neural networks. With the optimal algorithm the Raman gain spectra of multi-pumped FRAs were investigated. The results show that the optimal configuring algorithm is simple and effective.
The most important feature of Raman gain spectrum is that the gain peak wavelength only depends on the pump wavelength (fixed shift about 100nm). Using the gain values of these gain peak wavelengths we can determine how to adjust power and intervals of pumps until the optimal result is made. In this paper, using the peak wavelength gain optimal method and a comprehensive model the Raman gain spectra of multi-pumped FRAs under the various conditions were investigated. The results show that controlling the pump sources power and wavelength intervals can optimize the bandwidth and flatness of gain spectrum. The optimal configuring method for the multi-pump sources of distributed FRAs is simple and effective.
Internet backbone network is undergoing a large-scale transformation from the current complex, static and multi-layer electronic-based architecture to the emerging simplified, and dynamic and one-layer photonic-based architecture. The explosive growth in the Internet, multi-media services, and IP router links are demanding the next generation Internet that can accommodate the entire traffic in a cost-effective manner. There is a consensus in current industries that IP over WDM integration technologies will be viable for the next generation of the optical Internet where the simplified flat network architecture can facilitate the networking performance and the networking management. In this paper, we firstly propose a novel node architecture-Terabit Optical Router (TOR) for building the next generation optical Internet and analyses each key function unit of TOR including multi-granularity electrical-optical hybrid switching fabrics, unified control plane unit and so on. Secondly, we give the unified routing definition of multi-layer in TOR and present control plane software structure with emphasis on multi-layer routing issues. Thirdly we describe our cost vs. performance analysis for various application of TOR. According to our calculation, we can get a cost reduction of more than 60 percent by using the TOR. Finally, we reach conclusions that TORs rather than OBS/OPS-based optical routers or big fat router, a cost effective multi-granularity switching and routing technique, are feasible to build the next generation Internet in the coming 5-10 years.
Using a comprehensive model that includes pump-to-pump, pump-to-signal, signal-to-signal interaction, Rayleigh scattering and amplified spontaneous emission the Raman gain spectra of multi-pumped Raman amplifier under the various conditions were investigated. The results show that a different pump powers and pump wavelength intervals schemes are required for multi-pumped Raman amplifier. To obtain broader bandwidth and smaller gain ripple the powers of the shorter and longest wavelength pumps are needed higher power and the powers of the middle wavelength pumps should be set lower.
Optical layer networking and survivability are very important branches of the study of optical communication network. Recent standards proposals have focused on extending MPLS protocols to manage optical network resources. These proposals have concentrated on provisioning optical connections and offering restoration capability in mesh optical networks. Few papers, however, are concentrated on protection issues of backup path. By considering the protection of backup path, survivability of protection scheme will improve. This article presents a novel paradigm enhancing the existing pre-established protection schemes using Multi-Protocol Lambda Switching architecture and demonstrates local restoration and global restoration for backup path with examples. Finally, we discuss the advantages of this approach and present future work.
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