New Expansion of Science Information Network
- Configuration of New Network -

1. Introduction

As announced in an article entitled "Toward the Implementation of a High-Speed Network" in NACSIS Newsletter No.9, December 1993, the NACSIS has started High-Speed Science Information Network in September 1994, using the latest communications technology called Asynchronous Transfer Mode (ATM). At the same time, we introduced high-speed digital cirsuit of 6 Mega bits per second (6Mbps) to main trunk circuits connecting 10 nucleus node, 1Mbps circcuits among other 19 nodes and nucleus nodes, as well as 2Mbps cirsuit for international connection between Japan and the US. Details of the new configuration of new Science Information Network are given in this article.

2. New Network Configuration

2.1 Outline is TCP/IP Internet backbone using Time Division Multiplexer (TDM) to carryh both traffic through single trunk circuit. However, by limitation of thses TDMs, communication capacities assigned to these networks are not so flexible to change dynamically. This meant that each network had to operate individually with rigidly allocated capacity. It is quite inconvenient form the viewpoint of efficient circuit usage. That is why the NACSIS is aiming toward providing high speed and flexible network service by introduction of ATM. ATM makes also possible to deploy 155Mbps and further which is included in the future plan by the Nippon Telegraph and Telephone Corporation (NTT).

The systematic features of ATM enable it to handle any form of data, even files and audio clips, by dividing it into short (48 x 8 bits) units called cells for transfer. This system is configured of dedicated hardware that uses high-speed elements, which will also make it possible to reduce transfer delays.

There are several vital areas that the introduction of an ATM switching network must address. It should not only provide for higher speeds in the future, but also ensure efficient use of capacity between the two independent networks, using asynchronous transfer, and enable flexible configuration of logical topology between nodes.

2.2 Node Configuration Instead of TDMs, the basic configuration includes an ATM switch (ASX-100, made by FORE Systems) in every network nodes as shown in Figure 1. A Cell Assembly and Disassembly (CLAD) and concentrating equipment (Fujitus E-5340 or Cascade's B-STDX9000) is used on the front end of each ATM switch in order to multiplex packet and Internet traffic and to dividing into ATM cell. A speed converter (Fujitsu SC-1A) for converting the 155 Mbps used by a SONET/OC-3c to the 6 Mbps of the high-speed digital circuits is used on on the trank. This is because 6 Mbps is currently the maximum speed provided by communications carriers. An IP Router (BL-3000 provided by NTT) with the direct ATM interfaces is also introduced in 10 nucleus nodes, to ensure that future enhancement, such as campus LAN using FDDI and/or ATM Hub can be handled directly by BL-3000 and ATM switch.
The main advantages over the previous setup are:

  1. Capacity allocations to packet switchers and SINET routers can be changed dynamically.
  2. Forward compatibility will be possible with ultra-fast (155 Mbps) links of the future.
***** Figure 2: Physical and Logical Line Configuration ********

3. Conclusion

The introduction of ATM converters has enabled us to enjoy all the advantages of faster speeds, without subscribers having to change their current connection methods. It also enables the future direct connection of further additions such as in-house LANs, and we expect that even users who require high-speed communications for large quantities of data will be highly satisfied.

However, there is still a great deal to be discussed concerning the operation of an ATM network. It is thought that some time will be required before large numbers of researchers will be able to use the high-speed functions of ATM with ease, but we are confident that this is deeply significant as a first step toward the implementation of the next generation of the Science Information Network.

We hope that you will continue to support us and bear with any minor inconveniences as we work towards providing stable operation of the Science Information Network with even more features.

NACSIS Newsletter p.3-5 (February 1995)