## 2 Overview of Network Architecture and Networking Technologies
### Usage Examples of Layer-1 BoD Services  
To accommodate the huge amounts of data generated from a big science project into our network, we want to avoid a situation in which they become bursty enough to fill up the bandwidth of the circuits through a number of transit nodes and adversely affect other service traffic. We therefore assign a sufficient fixed bandwidth between source and destination sites on demand for the project by using an end-to-end layer-1 path and completely separate the network resources between the data from the project and the other service traffic. One of the layer-1 technologies, VCAT, can assign the network resource with a granularity of 150 Mbps and can also get the network resource from parallel circuits and multiple routes between the core nodes in our network (Figure 3). We get the bandwidth from several links as equally as possible, which is good for load balancing of the layer-2/3 service traffic.  
We developed a layer-1 BoD server for the BoD services requested by users. The server calculates the appropriate path routes to get the total end-to-end bandwidth by using VCAT, triggers the setup and release of layer-1 paths, and manages the resource assignment for layer-1 services. At the specified start time, the layer-1 BoD server runs the L1-OPS to direct the source layer-1 switch to establish a layer-1 path toward the destination layer-1 switch. The layer-1 BoD server also runs the L1-OPS to change the path bandwidths for the layer-2/3 services when needed.  
Figure 3: Core network topology and initial BoD users.  
The e-VLBI project [4] led by the National Astronomical Observatory of Japan (NAOJ) is the first project to use the layer-1 BoD service. This project observes celestial bodies only when the intended radio telescopes, near Yamaguchi Univ., the National Institute for Fusion Science (NIFS), the High Energy Accelerator Research Organization (KEK), and Hokkaido Univ., are available. It therefore needs end-to-end paths only during the observation period. The data measured at these sites are transferred to a central analysis device at NAOJ. The project currently sends about 2-Gbps worth of observation data through 2.4-Gbps SDH interfaces between the sites. To make the resolution of the array even finer, plans are underway to secure additional radio telescopes and bandwidth on demand of more than 8 Gbps through 10-Gigabit Ethernet interfaces.  
The layer-1 BoD services also have excellent end-to-end QoS properties, such as small delay, no delay variance, and no packet losses. The high-quality remote backup project [8] backs up huge amounts of data with a high-performance transfer protocol. The data transfer experiments are done between Osaka Univ., NII, Hokkaido Univ., and Kyushu Univ. The project is currently evaluating the transfer performance between these sites by varying the path bandwidth from 150 Mbps to 1.05 Gbps over Gigabit Ethernet interfaces. A room-sharing video system, called t-Room [9], which allows people at different sites to feel as if they are in the same room, requires a high-quality communication environment with a maximum of a 300-Mbps bandwidth. It transfers eight-sided high-definition video images, voices, and control signals. Doshisha Univ. and NTT Communication Science Laboratories are evaluating the system performance between Kyoto and Atsugi via Tokyo. NII sometimes perform demonstrations between remote sites such as Hokkaido Univ. to Kyushu-Univ. by using 1.5-Gbps non-compressed high-definition videos [10] in order to disseminate a high-quality communication environment created by the layer-1 BoD services.