Traditionally, research on routing and wavelength assignment over wavelength-routed WDM networks is concerned with immediate reservation (IR) demands. An IR demand typically does not specify a holding time for data transmission and the start time of the data transmission is assumed to be immediate (i.e. when the connection request arrives). The concept of advance reservation (AR) has recently been gaining attention for optical networks. An AR demand typically specifies information about the start of the data transmission or a deadline, as well as the holding time of the transmission. AR has several important applications for both wide-area networks and Grid networks. For example, AR can be used for adjusting virtual topologies to adapt to predictable peak hour traffic usage. It can be used to provide high-bandwidth services such as video conferencing and in Grid applications requiring the scheduled distribution of large files and for co-allocation of network and grid resources. AR can also be beneficial to the network by allowing the network operator to better plan resource usage and therefore increase utilization. Knowledge of the holding time can lead to more optimal decisions for resource allocation. This translates to better quality of service for users. In this paper we provide a comprehensive survey of the past and current work on advance reservation for optical networks. There have been many variations of the advance reservation concept proposed, so we will also provide a broad classification. In addition to the survey, we will discuss what we believe are important areas of future work and open challenges for advance reservation on optical networks.

A Survey of Advance Reservation Routing and Wavelength Assignment in Wavelength-Routed WDM Networks

Aiming at solving the scaling issues of bandwidth and latency in current hierarchical data center network (DCN) architectures, we propose and investigate a novel optical flat DCN architecture in which the number of interconnected ToRs scales as the square of the optical packet switches’ (OPS) port count (OPSquare). The proposed flat DCN architecture consists of two parallel interand intra-cluster networks that are built on a single-hop OPS with nanosecond time and wavelength switching for efficient statistical multiplexing operations. Fast optical flow control is implemented for solving packet contentions that may occur at the buffer-less optical switches. The performance of OPSquare DCN in terms of scalability, packet loss, latency, and throughput is assessed by a numerical simulation employing OMNeT++ under realistic data center (DC) traffic. The results report a server-to-server latency of less than 2 / s (including packet retransmission), a packet loss <10−5 at a load of 0.4, and aDC size of 10,240 servers with a ToR buffer size equal to 50 KB for all traffic patterns. Moreover, the cost and power consumption of the OPSquare DCN have been studied and compared with fat-tree DCN based on electrical switches and H-LION connected by an arrayed wave guide grating router (AWGR). The results indicate 23.8% and 39% cost and power savings, respectively, for the OPSquare DCN supporting 160,000 servers with respect to the fat-tree DCN. The OPSquare has a cost saving of 56% compared with H-LION for a 160,000-server DCN.

Opsquare: A flat DCN architecture based on flow-controlled optical packet switches

Toward integrated Cloud–Fog networks for efficient IoT provisioning: Key challenges and solutions

With the increasing diversity of applications supported over optical networks, new service guarantees must be offered to network customers. Among the emerging data-intensive applications are those which require their data to be transferred before a predefined deadline. We call these deadline-driven requests (DDRs). In such applications, data-transfer finish time (which must be accomplished before the deadline) is the key service guarantee that the customer wants. In fact, the amount of bandwidth allocated to transfer a request is not a concern for the customer as long as its service deadline is met. Hence, the service provider can choose the bandwidth (transmission rate) to provision the request. In this case, even though DDRs impose a deadline constraint, they provide scheduling flexibility for the service provider since it can choose the transmission rate while achieving two objectives: 1) satisfying the guaranteed deadline; and 2) optimizing the network's resource utilization. We investigate the problem of provisioning DDRs with flexible transmission rates in wavelength-division multiplexing (WDM) mesh networks, although this approach is generalizable to other networks also. We investigate several (fixed and adaptive to network state) bandwidth-allocation policies and study the benefit of allowing dynamic bandwidth adjustment, which is found to generally improve network performance. We show that the performance of the bandwidth-allocation algorithms depends on the DDR traffic distribution and on the node architecture and its parameters. In addition, we develop a mathematical formulation for our problem as a mixed integer linear program (MILP), which allows choosing flexible transmission rates and provides a lower bound for our provisioning algorithms.

Provisioning of deadline-driven requests with flexible transmission rates in WDM mesh networks

The design of a reconfigurable 4 × 4 photonic switch simultaneously supporting both packet and circuit switching is proposed and experimentally validated. Error-free operation and routing correctness is verified for pseudorandom 4 × 10-Gb/s packets and a 10-Gb/s stream.

Design and demonstration of an all-optical hybrid packet and circuit switched network platform for next generation data centers

We review our work on an intra-data center (DC) network based on co-deployment of optical packet switching (OPS) and optical circuit switching (OCS), conducted within the framework of a five-year-long national R&D program in Japan (∼March 2016). For the starter, preceding works relevant to optical switching technologies in intra-DC networks are briefly reviewed. Next, we present the architecture of our torus-topology OPS and agile OCS intra-DC network, together with a new flow management concept, where instantaneous optical path on-demand, so-called Express Path is established. Then, our hybrid optoelectronic packet router (HOPR), which handles 100 Gbps (25 Gbps × 4-wavelength) optical packets and its enabling device and sub-system technologies are presented. The HOPR aims at a high energy-efficiency of 0.09 [W/Gbps] and low-latency of 100 ns regime. Next, we provide the contention resolution strategies in the OPS and agile OCS network and present the performance analysis with the simulation results. It is followed by the discussions on the power consumption of intra-DC networks. We compare the power consumption and the throughput of a conventional fat-tree topology with the N -dimensional torus topology. Finally, for further power saving, we propose a new scheme, which shuts off HOPR buffers according to the server operation status.

Torus-Topology Data Center Network Based on Optical Packet/Agile Circuit Switching with Intelligent Flow Management

A deadline-aware-scheduling scheme for the lambda grid system is proposed to support a huge computer grid system based on an advanced photonic network technology. The assignment of wavelengths to jobs in order to efficiently carry various services is critical in lambda grid networks. Such services have different requirements such as the job-completion deadlines, and wavelength assignment must consider the job deadlines. The conventional job scheduling approach assigns a lot of time slots to a call within a short period in order to finish the job as quickly as possible. This raises the blocking probability of short deadline calls. Our proposal assigns wavelengths in the lambda grid networks to meet quality-of-services guarantees. The proposed scheme assigns time slots to a call over time according to its deadline, which allows it to increase the system performance in handling short deadline calls, for example, lowering their blocking probability. Computer simulations show that the proposed scheme can reduce the blocking probability by a factor of 100 compared with the conventional scheme under the low load condition in which the ratio of long deadline calls is high. The proposed scheduling scheme can realize more efficient lambda grid networks.

http://biblio.yamanaka.ics.keio.ac.jp/file/jlt_miyagi.pdf

Advanced Wavelength Reservation Method Based on Deadline-Aware Scheduling for Lambda Grid Networks

We review recent development of energy-efficient, low-latency intra-data center network, emphasizing on intelligent flow control capability, which simultaneously supports both OPS and OCS on-demand on a 100-Gbps (25-Gbps × 4-wavelength) platform consisting of hybrid optoelectronic packet routers.

Optical packet and path switching intra-data center network: Enabling technologies and network performance with intelligent flow control

In order to realize a multiplexer/demultiplexer in which utilization efficiency of a frequency is high, wavelength characteristics of a transmission band is flat, the cost is low, the size is small, and a wavelength and a band are variable, the multiplexer/demultiplexer includes: first light branching means for branching inputted light into plurality of pieces of light and outputting the branched pieces of light; a plurality of light wavelength separating means for separating and outputting light outputted from the first light branching means for each of predetermined frequency bands; and an optical coupling means for making outputs having frequency bands different from each other among outputs from the light wavelength separating means gather and be outputted.

Multiplexer/demultiplexer and multiplexing/demultiplexing method

This paper proposes a source-based high-speed wavelength-path protection scheme configuring a tree-shaped backup path in WDM networks. In the proposed scheme, a failure-detecting node on a primary path starts protection by sending a failure notification to a source node of the primary path through the tree-shaped backup path. Intermediate nodes on the backup path and the source node which receive the failure notification switch to the backup path autonomously. Therefore, the proposed scheme provides high-speed protection. The simulation results revealed that the proposed scheme reduces the failure-recovery time compared with the conventional protection schemes.

Masahiro Hayashitani

Papers

Torus-Topology Data Center Network Based on Optical Packet/Agile Circuit Switching with Intelligent Flow Management

Advanced Wavelength Reservation Method Based on Deadline-Aware Scheduling for Lambda Grid Networks

Optical packet and path switching intra-data center network: Enabling technologies and network performance with intelligent flow control

Multiplexer/demultiplexer and multiplexing/demultiplexing method

Source-based wavelength-path protection scheme with tree-shaped backup-path configuration in WDM networks