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GMPLS-based optical slot switching access-distribution network with a 10 ns high-speed PLZT optical switch Masahiro Hayashitani,1,* Teruo Kasahara,1 Daisuke Ishii,1 Yutaka Arakawa,1 Satoru Okamoto,1 Naoaki Yamanaka,1 Naganori Takezawa,2 and Keiichi Nashimoto2 1
Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan Nozomi Photonics Co., Ltd., KSP R&D C333, 3-2-1 Sakado, Takatsu-ku, Kawasaki, 213-0012, Japan *Corresponding author:
[email protected]
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Received April 7, 2008; revised June 20, 2008; accepted June 27, 2008; published July 25, 2008 共Doc. ID 94189兲 We design and implement an optical slot switching network for bulk content transfer. To realize the slot switching network, we employ the generalized multiprotocol label switching (GMPLS) extension protocol to reserve and release slots dynamically according to the application. We use optical switches as relay points in the slot switching network, and we employ a 10 ns highspeed 共Pb, La兲共Zr, Ti兲O3 (PLZT) optical switch. We extend the resource reservation protocol–traffic engineering (RSVP-TE) and realize optical slot reservation. In the slot reservation, the proposed scheme allocates a slot in a frame for clients in order to guarantee the minimum bandwidth. The scheme considers the accelerated and tentative slot reservation. In the slot switching network, we use the PLZT optical switch. The PLZT switch can improve the bandwidth utilization by reducing the guard time between slots unlike the microelectromechanical system (MEMS) switch. To realize the slot switching network, we develop a PLZT optical switch system with a GMPLS-based controller. By experiment based on the experimental network, we confirm that we can realize the slot switching network. We consider the application of the proposed network as an access network for content distribution. © 2008 Optical Society of America OCIS codes: 060.1155, 060.4250.
1. Introduction In Japan, fiber-to-the-home (FTTH) subscribers exceeded 10 million in 2008 and will reach about 20 million in 2010 [1]. The spread of ultra-high-speed access networks will enable us to transfer bulk content such as high-definition (HD) movie files. The transmission rate depends on the physical network in the lower layer because each layer operates independently in the present network. Therefore, to transfer bulk content quickly and efficiently, it is necessary to operate the lower layer in conjunction with the traffic and application in the upper layer. In this paper, we design and implement an optical slot access-distribution switching network suitable for bulk content transfer. In the optical slot switching network, an optical wavelength is divided into slots that occur cyclically. The network transfers content by using slots. We consider that the optical slot switching network is the best approach because a network user can, in some slots, access large bandwidth. However, it is very difficult to realize the slot switching network with conventional optical switches such as the microelectromechanical system (MEMS) switch. Because the switching time of the MEMS switch is several hundred milliseconds and the overhead between slots is large, a network based on the MEMS switch cannot transfer content efficiently. Thus, we employ a newly developed 共Pb, La兲共Zr, Ti兲O3 (PLZT) ultra-highspeed optical switch [2–4] to overcome this limitation. The PLZT switch can improve the bandwidth utilization by reducing the guard time between slots, unlike the MEMS switch. In addition, we employ the generalized multiprotocol label switching (GMPLS) [5,6] extension protocol as the slot reservation scheme. GMPLS is a set of network control protocols to envision next-generation high-performance transport networks. Unlike time division multiplexing (TDM), GMPLS enables the slot switching 1536-5379/08/080744-15/$15.00
© 2008 Optical Society of America
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network to reserve and release slots dynamically, and it realizes the distributed control of optical switches in the network. By experiments based on the experimental network, we show that we can realize the slot switching network. We consider the application of the proposed network as an access network for content distribution. We also show that the proposed network has a large scalability, covering more than 500 subscribers, compared with a passive optical network (PON) and that it can realize a transparent and secure network because the service provider in the proposed network sends data only to the client requesting it. The rest of the paper is organized as follows. We present the optical slot switching access-distribution network in Section 2. We show the experiments of the slot switching network in Section 3. Finally, we conclude the paper in Section 4.
2. Proposed Optical Slot Switching Access-Distribution Network Figure 1 shows our proposed access-distribution network. We consider this network to support content distribution in the access network well. The proposed network has a tree topology from a service provider to clients through optical switches. The slot switching network consists of a control plane and a data plane, and it synchronizes the devices in the network. The control plane employs the GMPLS extension protocol and reserves optical slots based on [7]. The data plane is an all-optical network based on the PLZT optical switches manufactured by Nozomi Photonics. This product is the result of a collaboration between Keio University and Nozomi Photonics. The switch device specifications of this product were designed through the collaboration of Keio University and Nozomi Photonics. Nozomi fabricated the switch device, and the switch subsystem was developed by Keio, who also made the controller of the switch subsystem and the protocol controller for multiple switch systems. Frames are used in the data plane, and each frame has several slots. The data are transferred by using slots. In this section, we explain the optical slot reservation by GMPLS extension protocol and the slot switching by the PLZT high-speed optical switch. 2.A. Optical Slot Reservation by GMPLS Extension Protocol We extend the time division multiplexing–label-switched path (TDM-LSP) scheme in resource reservation protocol–traffic engineering (RSVP-TE) [8] and realize optical slot reservation. RSVP-TE is standardized as the GMPLS signaling protocol. Figure 2 shows an example of slot reservation in the slot switching network. Each vertical line is a timeline, and each timeline is divided into frames consisting of several slots. In Fig. 2, the number of slots in a frame is three. We assume that the service provider receives a content request from client A. The service provider sends a PATH message for client A after receiving the request. Intermediate nodes receiving the PATH message confirm whether there are vacant slots. If there are vacant slots,
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