The deployment of hybrid wide-area OpenFlow networks is essential for the gradual integration of OpenFlow technology into existing wide-area networks. Integration is necessary because it is impractical to replace such wide-area networks with OpenFlow-enabled ones at once. On the other hand, the design, deployment, and operation of such hybrid OpenFlow networks are often conducted intuitively without in-depth technical considerations. In this paper, we systematically discuss the technical aspects of the hybrid architecture for OpenFlow networks based on our experience so far in developing wide-area hybrid OpenFlow networks on JGN2plus and JGN-X, which are nation-wide testbed networks in Japan. We also describe the design and operation of RISE (Research Infrastructure for large-Scale network Experiments) on JGN-X, whose objective is to support a variety of OpenFlow network experiments.

In the IETF, discussions on the authentication method of the Dynamic Host Configuration Protocol (DHCP) message are active and several methods have been proposed. These related specifications were published and circulated as the IETF Internet-Drafts. However, they still have several drawbacks. One of the major drawbacks is that any user can reuse addresses illegally. A user can use an expired address that was allocated to a host. This kind of "illegal use" of the addresses managed by the DHCP server may cause serious security problems. In order to solve them, we propose a new access control method to be used as the DHCP message authentication mechanism. Furthermore, we have designed and developed the DAG (DHCP Access Control Gateway) according to our method. The DAG serves as a gateway that allows only network accesses from clients with the address legally allocated by the DHCP server. This provides secure DHCP service if DHCP servers do not have an authentication mechanism, which is most likely to occur. If a DHCP server has such an authentication scheme as being proposed in IETF Internet-Draft, the DAG can offer a way to enable only a specific client to access the network.

A new configuration is proposed for adaptive Rank Order Filters ('AROF') which adaptively extract the 'optimal rank'. The optimal rank is determined using the 'noise elimination efficiency' of ROF. The simulated results show that the AROF is more effective than the conventional rank-fixed ROFs at eliminating impulse noise.

A new high-speed decoding algorithm for Difference-set cyclic codes, and the design and implementation of a 50 MHz CMOS LSI for decoding the (1057, 813) DSCC, are presented. The algorithm, called modified threshold decoding, makes it possible to introduce an arbitrary number of pipeline stages into feedback loops in decoding circuits. A prototype LSI containing about 13k logic gates was fabricated using 1 µm CMOS gate-array technology. The power consumption is less than 750 mW at a 50 MHz clock rate. It is available for digital data transmission systems having an I/O data rate of up to 25 MBPS. It is being used in experimental set-ups targeted at future digital broadcasting systems. The proposed algorithm has an important advantage for much longer codes as it has the potential to be used in the high-speed decoding of DSCCs having a code length longer than 1057.