Optical IP Networks Research Articles

A Numerical Model of a Bulk Flow TCP and its Routing Performance Analysis for the Optical IP Networks

bulk flow TCP and its routing performance of the optical IP networks is analyzed numerically. Four types of data transmission viz. fixed size flow discard, fixed size early flow discard, variable size flow discard and variable size early flow discard for the optical domain are investigated. Various probability density functions for the data transmissions are derived for the computation. State transition diagrams for the various flow transmission techniques are designed to study the steady state probability of the buffer usage. The variable size early flow discard technique provides good throughput of 44% for a load of 3.5 for a mostly congested traffic where as the conventional packet discard exhibits only 3% of good throughput under same load and traffic condition. Buffer usage is found to be a minimum value for the variable size early flow discard (43%) than the packet discard (99%).

Demonstration of the Transportation of a Microwave Environment Over an Optical IP Network

The concept of the transportation of a microwave environment-a technology that can transport microwaves over an IP network- is discussed. The several possible applications facilitated by this concept are also discussed. A pair of UHF-band microwave/Internet protocol (IP) conversion network interfaces are prototyped, and a unidirectional transport of an integrated service of digital broadcasting-terrestrial (ISDB-T) signal is demonstrated. It is shown that the ISDB-T signal can be transported over an IP network maintaining the bit error rate quality of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> even when the microwave is sampled by the 6-bit ADC device with an operation rate lower than twice the transported frequency. However, the demonstration shows the IP transportation requires additional carrier-to-noise power ratio margin for the microwave before the IP transportation because of the flat-top sampling process with limited analog input/output bandwidth of ADC/DAC devices. This paper also suggests that transporting truncated microwaves intermittently over an IP network and analyzing them centrally are effective for collecting and monitoring microwave conditions at remote multiple places, such as power levels and spectrums, with reduced throughput.

Energy saving and cost reduction in multi-granularity green optical networks

With the energy consumption increase and the greenhouse effect becomes more and more serious, the energy saving has become the focus in the whole world. At the same time, as the network traffic largely growing, the size and the cost of network equipments keep increasing so that the network cost reduction is also very important. In recent years, the concept of green Internet was proposed to construct an energy-efficient and cost-optimal green network. In this paper, we firstly present the current studies working on the energy saving and cost reduction in multi-granularity optical network that is the convergence between IP network and optical network to support both the low-speed IP data and the high-speed optical transmission. After analyzing the current studies, in our opinion, the traffic grooming mechanism with optical bypass technology is the feasible solution by binding a lot of low-rate IP data into a few of high-speed lightpaths to reduce a lot of electrical ports consumption in IP routers for saving the energy, the waveband switching mechanism is the feasible solution by binding multiple lightpaths into a few of waveband tunnels to save the optical transmitting ports consumption in Multi-Granularity Optical Cross-Connects (MG-OXCs) for reducing the network costs, and the multi-granularity grooming mechanism is the feasible solution by integrating the traffic grooming with the waveband switching to achieve both the energy saving and cost reduction. Based on our opinion, this paper proposes the challenging issues including the network node model, virtual topology design, certain traffic matrix and uncertain traffic matrix for energy saving and cost reduction in multi-granularity optical network, with possible solutions and preliminary simulation results to guide the future work.

Energy Consumption in Optical IP Networks

As community concerns about global energy consumption grow, the power consumption of the Internet is becoming an issue of increasing importance. In this paper, we present a network-based model of power consumption in optical IP networks and use this model to estimate the energy consumption of the Internet. The model includes the core, metro and edge, access and video distribution networks, and takes into account energy consumption in switching and transmission equipment. We include a number of access technologies, including digital subscriber line with ADSL2+, fiber to the home using passive optical networks, fiber to the node combined with very high-speed digital subscriber line and point-to-point optical systems. In addition to estimating the power consumption of today's Internet, we make predictions of power consumption in a future higher capacity Internet using estimates of improvements in efficiency in coming generations of network equipment. We estimate that the Internet currently consumes about 0.4% of electricity consumption in broadband-enabled countries. While the energy efficiency of network equipment will improve, and savings can be made by employing optical bypass and multicast, the power consumption of the Internet could approach 1% of electricity consumption as access rates increase. The energy consumption per bit of data on the Internet is around 75\bm muJ at low access rates and decreases to around 2-4 \bm muJ at an access rate of 100 Mb/s.

IP Routing and Traffic Analysis in Coherent Optical CDMA Networks

This paper proposes a novel IP routing schemes over coherent optical code-division multiple-access (OCDMA) network. As spreading code, flexible in length double-padded modified prime code (DPMPC) has been deployed. The performance has been analyzed in terms of the users' channel utilization factor in the network. The results are comparable with previous schemes and indicate that the architecture is power efficient and capable of accommodating greater number of active users with advantage of shorter code length (i.e., higher bit rate). It is shown that for a maximum bit rate the network performance can be improved by reducing the channel utilization. However, when each user in the network has a fixed bit rate, optimal channel utilization can be set for the overall network performance. Additionally, each IP packet is buffered only at the edge of this network, thus the buffer delay is significantly reduced compared with traditional routing schemes. Since the optical encoder is adjusted for number of packets rather than individually, the encoder adjusting time is also significantly reduced. Analytical results clearly indicate that coherent OCDMA technique can be a fine candidate for the future ultra fast optical IP networks.

Evolution of WDM Optical IP Networks: A Cost and Energy Perspective

We review technologies and architectures for WDM optical IP networks from the viewpoint of capital expenditure and network energy consumption. We show how requirements of low cost and low energy consumption can influence the choice of switching technologies as well as the overall network architecture.

New insights on survivability in multi-domain optical networks

With the development of intelligent optical networks and the general multi-protocol label switching (GMPLS) technique, the seamless convergence between IP network and optical network is no longer be a dream but a practical reality. Similar to the Internet, current optical networks have been divided into multiple domains each of which has its own network provider and management policy. Therefore, the development of multi-domain optical networks will be the trend of new-generation intelligent optical networks, and GMPLS-based survivability for multi-domain optical networks will become a hot topic of research in the future. This paper provides a comprehensive review of the existing survivable schemes in multi-domain optical networks and analyzes the shortcomings of current research. Based on previous studies, we present possible challenges and propose new ideas to design efficient survivable schemes to guide the future work of researchers in multi-domain optical networks.

Performance Analysis of Bulk Flow TCP for Routing in Optical Network

Information through optical networks has been extensively studied in recent year to provide high through put, high capacity for the Internet traffic. Optical packet switching network deploying buffering, wavelength conversion and multipath routing could be the most suitable one. However due to the packet oriented routing and switching, network can result in a large amount of packet out-of-order, packet loss and cause various delays in arriving upon end system, causing TCP flows that comprise those packets corrupted. The corrupted flows can increase the business of the internet traffic and cause malfunction in the higher layer protocol. In this paper, a novel performance analysis for routing and switching in optical IP networks has been proposed and implemented. The effect of fixed and variable size in flow discard (FD) and early flow discard (EFD) process to achieve higher throughput rate has been studied extensively. We have achieved the loss is only about 24.95 % in optical flow routing which is 71.17 % in optical packet routing. This technique ensures a maximum and uniform delay in arrival of packet and it increases the throughput.

Latest Trends in Traffic Matrix Modeling and Its Application to Multilayer TE

We survey traffic matrix models, whose elements represent the traffic demand between source-destination pair nodes. Modeling the traffic matrix is useful for multilayer Traffic Engineering (TE) in IP optical networks. Multilayer TE techniques make the network so designed flexible and reliable. This is because it allows reconfiguration of the virtual network topology (VNT), which consists of a set of several lower-layer (optical) paths and is provided to the higher layer, in response to fluctuations (diurnal) in traffic demand. It is, therefore, important to synthetically generate traffic matrices as close to the real ones as possible to maximize the performance of multilayer TE. We compare several models and clarify their applicability to VNT design and control. We find that it is difficult in practice to make an accurate traffic matrix with conventional schemes because of the high cost for data measurement and the complicated calculations involved. To overcome these problems, we newly introduce a simplified traffic matrix model that is practical; it well mirrors real networks. Next, this paper presents our developed server, the IP Optical TE server. It performs multilayer TE in IP optical networks. We evaluate the effectiveness of multilayer TE using our developed IP Optical server and the simplified traffic matrix. We confirm that multilayer TE offers significant CAPEX savings. Similarly, we demonstrate basic traffic control in IP optical networks, and confirm the dynamic control of the network and the feasibility of the IP Optical TE server.

Fast Restoration Based on Alternative Wavelength Paths in a Wide Area Optical IP Network

In this article we describe an experimental investigation of IP network restoration based on wavelength recovery. We propose a procedure for metro and wide area gigabit Ethernet networks that allows us to route the wavelength in case of link failure to another existing link by exploiting wavelength division multiplexing in the fiber. Such a procedure is obtained by means of an optical switch that is managed by a loss-of-light signal that is generated by a router in case of link failure. Such a method has been tested in an IP network consisting of three core routers with optical gigabit Ethernet interfaces connected by means of 50-km-long single-mode fibers between Rome and Pomezia. Compared with other conventional restoration techniques, such as OSPF and MPLS, our method -in very fast (20 ms) and is compatible with real-time TV services and low-cost chips.

Comparison between objective and subjective measurements of quality of service over an Optical Wide Area network

AbstractThe introduction of intelligence for management and control of the quality of service (QoS) are key issues for the evolution of the next generation IP optical network based on Ethernet technology. A test bed of a core‐access network was implemented to investigate such issues and in this paper, the authors report measurements concerning the QoS of multimedia services for different traffic conditions. The network was implemented with a differentiated service over Multi‐Protocol Label Switch (MPLS) architecture; it consists of a real optical network based on core routers with optical Gigabit Ethernet (GBE) interfaces connected by means of long single mode fibres (about 50\,km), contained in an installed cable between Rome and Pomezia. The network is based on different access devices, but in this paper we only refer to an access based on Fibre To The building (FTTB) architecture. The QoS was investigated both in terms of network (or objective) tests that include packet loss, jitter, one way delay and throughput measurements and perceptive (or subjective) tests that conversely are based on the evaluation of user perception. The services under test mainly consisted of video streams that circulated in the network according to the switching operations based in the IP differentiated service over MPLS technique that allowed us to guarantee the QoS for some class of service, also in the presence of network overload. Particular attention was given to the correlation between objective and subjective measurements. Furthermore, in order to have a complete analysis about QoS of real networks, measurements were performed also in the presence of restoration operations for link failures; in particular we compare the results in the case of conventional IP network restoration with a procedure proposed by us and based on a link switching activated by the loss of signal command coming from the routers. Copyright © 2007 John Wiley &amp; Sons, Ltd.

IP over optical cross-connect architectures [Topics in Optical Communications

IP over optical network architectures have been extensively discussed within the research literature over the past few years. However, although signaling protocols between IP routers and optical cross-connect networks have been standardized, large IP backbones are not typically deployed over optical cross-connect networks with automatic reconfigurability features, such as automatic restoration or dynamic establishment of new IP links. One of the most important criteria in determining whether an IP backbone should be carried over such an optical cross-connect network is economic viability. In this article we analyze and explore four architectures for a typical large ISP backbone. In contrast with some other published claims, our results suggest it is more economically attractive to bypass an intermediate cross-connect network, given current equipment and IP backbone network design requirements. However, for ISPs who also provide a large volume of private line services, we propose an integrated architecture for IP over optical cross-connect networks that may provide an attractive alternative for providing rapid and cost-effective restoration from network failures

Performance of deflection routing algorithms in IP optical transport networks

This paper 1 Work partially supported by EU IST Network of Excellence e-Photon/ONe. A preliminary version of this paper has been presented at BROADNETS 2004 conference. 1 deals with optical packet switching in a full-IP transport network scenario. For the switching of IP packet flows different node architectures are considered that are based on current optical routing devices. The traffic performance of a mesh network is evaluated with the various node structures, assuming that nodes employ either shortest path routing or deflection routing to forward packets to the addressed destinations. The paper shows how the different node structures behave in terms of packet loss probability with different network configurations when the node parameters are varied.

Value-added proposition of the GMPLS control plane in IP optical networks

We quantify the value-added proposition of the generalized multiprotocol label switching (GMPLS) distributed control plane vis a vis the centralized network management (CNM) plane. Our main objective is not to propose new protocols or algorithms, but rather to provide guidance to network operators on how to maximize the benefits of deploying a GMPLS control plane. We identify two main goals for maximizing these benefits: (1) decreasing operations costs and (2) increasing revenues through enhancing the efficiency of existing network assets as well as through enabling new services. Control plane functionalities such as dynamic routing, user-initiated end-to-end connection setup, and distributed fault management in IP optical networks are analyzed to determine optimal operating regions where their values are maximized. Extensive simulations using NSFNET topology have been carried out from which we have found that there are certain operating regions where (1) the distributed routing can improve the efficiency of network assets by saving 15% of the number of wavelengths per link, or increasing traffic loads by 20%. However, if the call interarrival time is shorter than 1 min, the efficiency (in terms of call blocking ratio) of distributed dynamic routing is reduced due to the OSPF convergence delay. (2) Enabling bandwidth on demand (BoD) services at finer bandwidth granularities connections is more cost-effective to the operator than doing the same at coarse bandwidth granularities. (3) The connection setup delay is the limiting factor in determining the types of BoD services a carrier offers. The call blocking ratio will increase quickly if the average call interarrival time is less than tens of seconds. (4) Assuming only single link failure, M:N shared protection can achieve 100% recovery at the expense of 10% increase in the number of wavelengths compared with nonprotection schemes, while saving are as high as 48% wavelengths compared with 1:1 dedicated protection.

Proposal of One-by-One Transmission through Ring Optical IP Networks

One-by-one transmission and the IP routing through one-fiber ring have been proposed. The network was constructed, the routing functions were implemented, and the throughputs were measured. No additional degradations were found between the throughputs by the proposed transmission and the direct uploading.

Dynamic Routing of Bandwidth Guaranteed Connections in MPLS Networks

Finding a path in the network for a new incoming connection able to guarantee some quality parameters such as bandwidth and delay is the task of QoS routing techniques developed for new IP optical networks based on label forwarding techniques such as Generalized Multiprotocol Label Switching (GMPLS). In this paper we focus on the routing of bandwidth guaranteed flows in a dynamic scenario where new connection requests arrive at the network edge nodes. When more than one path satisfying the bandwidth demand exists, the selection of the path aims at minimizing the blocking probability of future requests. We propose a new routing algorithm named Virtual Flow Deviation (VFD) which exploits the information of the ingress and egress nodes of the network and the traffic statistics. This new algorithm, in most scenarios, achieves remarkable reduction in the blocking probability with respect to previously proposed schemes.

Design and Analysis of a Backbone Architecture with TDMA Mechanism for IP Optical Networking

This paper presents a new technique for constructing IP over photonic systems. The use of lable switching is assumed in the IP routers, while a new routing architecture is introduced to transport IP packets across an optical backbone network. The architecture is based on a two-level TDMA structure with wavelength division multiplexing (WDM). Many IP-based network applications such as high-resolution image, distributed database, and real-time video/audio service generally require high-speed transmissions in WAN/LAN. The network traffic in these applications usually exhibits traffic locality. As a result, traditional TDMA is not efficient for such traffic. Consequently, based on the traffic parameters such as locality and loading, an architecture named a PG (Partition-Group) Network is proposed. Furthermore, the interleaved control slot (ICS) with cross-group section (CGS) or non-cross-group section (NCGS) for reducing collisions is also presented. The slot reuse can be easily achieved by using the ICS scheme, and the slot utilization of the network can be improved within the high traffic locality.

Flow Routing and its Performance Analysis in Optical IP Networks

Optical packet-switching networks deploying buffering, wavelength conversion and multi-path routing have been extensively studied in recent years to provide high capacity transport for Internet traffic. However due to packet-based routing and switching, such a network could result in significant disorder and delay variation of packets when they are received by end users, thus increasing the burstiness of the Internet traffic and causing higher-layer protocol to malfunction. This paper addresses a novel routing and switching method for optical IP networks — flow routing, and its facilitating protocol. Flow routing deals with packet-flows to reduce flow corruption due to packet out-of-order, delay variation and packet loss, without using complicate control mechanism. Detailed performance analysis is given for output-buffered optical routers adopting flow routing. Two flow-oriented discarding techniques, i.e., flow discard (FD) and early flow discard (EFD), are discussed. Compared with optical packet-switching routers, a remarkable improvement of good-throughput is obtained in the optical flow-routers, especially under high congestion periods. We conclude that EFD behaves as a robust technique, which is more tolerant than FD to the change of traffic and transmission system factors.

Analysis and design of backbone architecture alternatives for IP optical networking

The unprecedented growth of IP traffic is leading Internet service providers and network operators worldwide to investigate architectural alternatives for cost effective, reliable, scalable, and flexible multiterabit IP backbones. In this paper, several overlay, service, and transport layer networking architectures, which employ IP, MPLS, SONET/SDH, and DWDM technologies, are proposed and analyzed. Multiple parameters, such as network capacity, cost, restoration strategy, reconfigurability, and accommodation of preemptable traffic, are considered for the architectural comparison. Detailed network design and economic analysis are provided for the different alternatives considering a typical nationwide U.S. backbone with projected IP traffic in approximately three years. Several sensitivity analysis results are also shown, to evaluate the effect of cost changes in some of the critical technological factors in these architectures, such as 10 Gb/s optics cost or IP router cost. The results show the value of transport layer networking architectures for multiterabit IP backbones, and how, when compared to service layer architectures, they provide additional desirable features such as wavelength reconfigurability and restoration scalability.