The QoS provided by today's best effort Internet is not good enough for real-time premium traffic. It is believed that the QoS guarantees of the Internet could be better provided by connection-oriented networks. IP/MPLS is one such technology and these connection-oriented networks are inherently more vulnerable to network failures. Network failures can broadly be classified into two types, ie., link/path and degraded failures. Degraded failures that account for about 50% of total failures are detected by control-plane timers. The control plane and the data plane of IP/MPLS networks are logically separated and therefore a failure in the control plane should not immediately terminate communications on the data plane. The Virtual Path Hopping (VPH) concept proposed in this study distinguishes these degraded failures from link/path failures and avoids the terminations of data communications on the data plane that are due to these degraded failures. It changes the traffic carrying a degraded VP to a new VP in a predetermined VP-pool before the control-plane timer expires due to degraded failure. This paper discusses the concept of VPH and its numerous advantages such as load balancing, traffic distribution, and the ability to support dual-failure situations. Computer simulations were conducted and the results are presented to support the concept of VPH.

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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.

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If a shared IP network is to deliver large-volume streaming media content, such as real-time videos, we need a technique for explicitly setting and dynamically changing the transmission paths used to respond to the congestion situation of the network, including multi-path transmission of a single-flow, to maximize network bandwidth utilization and stabilize transmission quality. However, current technologies cannot realize flexible multi-path transmission because they require complicated algorithms for route searching and the control load for route changing is excessive. This paper proposes a scheme that realizes routing control for multi-path transmission by combining multiple virtual networks on the same physical network. The proposed scheme lowers the control load incurred in creating a detour route because routing control is performed by combining existing routing planes. In addition, our scheme simplifies route searching procedure because congestion avoidance control of multi-path transmission can be realized by the control of a single path. An experiment on the JGN-X network virtualization platform finds that while the time taken to build an inter-slice link must be improved, the time required to inspect whether each slice has virtual nodes that can be connected to the original slice and be used as a detour destination can be as short as 40 microseconds per slice even with large slices having more than 100 virtual nodes.

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We propose a multicast tree management method in an OpenFlow controller that handles both fast failure recovery and dynamic multicast group membership changes. Multicast communication is an efficient tool to distribute data to many hosts in various services such as live video streaming. To use multicast in such services, multicast communication must be reliable, which means multicast communication should be restored quickly after failures, and multicast tree management mechanism should support frequent group membership changes. A conventional approach, Point to Multipoint (P2MP) MPLS, only supports fast failure recovery for reliability, and is not very effective in terms of group membership changes. A new approach using OpenFlow supports dynamic group membership changes, but does not consider fast failure recovery in physical switches whose flow entry modification is slow. Our proposed method is to control multicast trees centrally, and it uses a precomputation and pre-installation approach for tree management. A controller calculates and keeps multiple trees that cover all switches where receivers are potentially connected and that have less common nodes and edges, and installs their sub-trees covering switches where receivers are actually connected. The controller calculates the difference per tree between sub-trees before and after membership changes, and reflects them into the network. At the time of failure, the controller checks and finds a pre-installed tree that is unaffected by the failure, and installs a new rule only to a root switch to send packets through the pre-installed alternate tree. Our experiments using switches and our prototype controller show that our proposed method can restore packet delivery quickly after a failure, as well as that our proposed method can handle tree modifications faster than a method of recalculating or reinstalling a tree every time that group memberships are changed.

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The QoS provided by current best effort Internet is not good enough for real-time multimedia applications that are categorized as premium traffic. It is believed that QoS guarantees could be better provided by the connection oriented networks. Multi Protocol Label Switching (MPLS) is one such technology and these connection oriented networks are inherently more prone to network failures. Re-routing is a solution to cope with them. However, the re-routing always causes packet losses and results in service outage. Therefore, the QoS of the real-time premium traffic is highly degraded. The seamless failure recovery proposed in this paper can be used for real-time premium traffic that needs a guaranteed QoS. It applies an FEC technique to the conventional re-routing based path protection and seamlessly recovers the packet losses due to re-routing by way of an FEC recovery technique. The numerical and simulation results show that the proposed method can provide network architecture without service outage for real-time premium traffic while minimizing the service costs such as redundant traffic and additional buffer at edge routers.

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Previously, routers have been responsible for both data forwarding and network management. Software-Defined Networking (SDN) separates these functions into a data plane and a control plane in order to simplify network operations and enable the construction of programmable networks. However, flow updates transmitted using the OpenFlow protocol introduce a communication overhead. Since Ternary Content Addressable Memory (TCAM) is used to quickly search flow entries, the associated costs rise significantly as the scale of the network increases. To address these problems, a method has been proposed that reduces flow entry update work and minimizes traffic overhead by aggregating some flows on a specific path in an SDN-managed network using SR (Segment Routing)-MPLS (Multi-Protocol Label Switching). However, while overall work is reduced, the load on the specific path used for the flow aggregation increases. This paper proposes a flow distribution algorithm with SR that efficiently utilizes network resources, while also addressing the two aforementioned limitations of Software-Defined Networking (SDN) to enable a more reliable SDN infrastructure. To evaluate the proposed algorithm, simulation experiments compared the proposed algorithm with the shortest-path algorithm on four network topologies with 13, 24, 48 or 58 nodes, and our results showed that the average standard deviation of the number of packets forwarded by each node under the proposed method was 861.04–1496.17 packets lower by comparison with the shortest-path method when the total number of transmitted packets was 50,000, and 1743.37–2950.34 packets lower when the total number of transmitted packets was 100,000. We also noted that the average path length for each packet under the proposed method was just 0.15–1.08 hops longer than that of the shortest-path method.

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