Published papers

The 5G core network will employ network slices, logical networks over physical infrastructure, each of which provides a specific service. There are two typical methods for network slicing: the hop- by-hop method using SDN and the edge-overlay method using Layer 2 over Layer 3 (L2 over L3) tunneling. In the hop-by-hop method, migration from the existing infrastructure is difficult and the SDN controller will become a single point of failure. In the edge-overlay method, tunneling causes header overhead and throughput degradation. This paper proposes a network slicing method without using SDN nor tunneling for the 5G core network using IPv6. In the proposed method, the lower 64-bit part of an IPv6 address (the node identifier) identifies a node and the upper 64-bit part (the locator) specifies the subnet to which the node is attached. This approach is suitable to support mobility management without tunneling such as MocLis. The slice identifier and the subnet number in the slice are embedded within the locator. Thus, the proposed method avoids the problems of system migration, a single point of failure, header overhead, and throughput degradation. In the proof of concept prototype, a Docker container is used as a virtual node in a network slice and a MPLS label-switched path is used as a virtual link between virtual nodes. TCP Throughput evaluation shows that the proposed method is superior to the edge-overlay method.

This paper argues that a layered approach is more suitable for Information CentricNetworking (ICN) than a narrow-waist approach and proposes an ICN mechanism called ZINK. In ZINK, a location-independent content name is resolved to a list of node IDs of content servers in the application layer and a node ID is mapped to a node locator in the network layer, which results in scalable locator-based routing. An ID/Locator split approach in the network layer can efficiently support client/serever mobility. Efficient content transfer is achieved by using sophisticated functions in the transport layer such as multipath transfer for bandwidth aggregation or fault tolerance. Existing well-tuned congestion control in the transport layer achieves fairness not only among ICN flows but also among ICN flows and other flows. A proof-of concept prototype of ZINK is implemented on an IPv6 stack. Evaluation results show that the time for content finding is practical, efficient content transfer is possible by using multipath transfer, and the mobility support mechanism is scalable as shown in a nationwide experiment environment in Japan.

Recently, application demands placed on the network have become more multifaceted. Highly functional application-to-application communication services such as bandwidth aggregation, fault tolerant communication, and delay/disruption tolerant networking (DTN) were developed independently in the network layer, the transport layer, and the application layer. As a result, protocol layering has become complicated. This paper proposes to insert Layer-5 (L5) between the application layer and the transport layer to separate communication policies and communication mechanisms to make protocol layering clearer. The transport layer (L4) provides end-to-end communication mechanisms such as reliable byte stream while L5 realizes communication policies such as bandwidth aggregation by combining the communication mechanisms in L4. This paper proposes five types of L5-paths as communication policies: (1) the L5 bundled path for bandwidth aggregation or fault tolerant communication, (2) the L5 spatially-spliced path for communication with middleboxes, (3) the L5 temporally-spliced path for DTN, (4) the L5 spliced-bundled path, and (5) the L5 bundled over spatially-spliced path. An application can select and use an appropriate L5-path depending on the network circumstances through a common API. A prototype of L5 is implemented in the Linux user space as a library to make deployment and maintenance easier. An evaluation shows that establishment time of L5-paths is short enough and performance of L5-paths is comparable or superior to existing technologies.

In LTE (Long Term Evolution) / LTE-Advanced (LTE-A) system, the user-plane for a user equipment (UE) is provided by tunneling, which increases header overhead, processing overhead, and management overhead. In addition, the LTE-A system does not support moving cells which are composed of a mobile Relay Node (RN) and UEs attached to the mobile RN. Although there are several proposals for moving cells in the LTE-A system and the 5G system, all of them rely on tunneling for the user-plane, which means that none of them avoid the tunneling overheads. This paper proposes MocLis, a moving cell support protocol based on a Locator/ID split approach. MocLis does not use tunneling. Nested moving cells are supported. Signaling cost for handover of a moving cell is independent of the number of UEs and nested RNs in the moving cell. A MocLis prototype, implemented in Linux, includes user space daemons and modified kernel. Measurements show that the attachment time and handover time are short enough for practical use. MocLis has higher TCP throughput than the tunneling based approaches.

In the LTE/LTE-Advanced (LTE-A) system, user-plane for a user equipment (UE) is provided by tunneling which causes header overhead, processing overhead, and management overhead. In addition, the LTE-A system does not support moving cells which are composed of a mobile Relay Node (RN) and UEs attached to the mobile RN. There are several proposals for moving cells in the LTE-A system and the 5G system, however, all of them rely on tunneling for the user-plane, which means that none of them avoid the tunneling overheads. This paper proposes MocLis, a moving cell support protocol based on a Locator/ID split approach. MocLis does not use tunneling. Nested moving cells are supported. Signaling cost for handover of a moving cell is independent of the number of UEs and nested RNs in the moving cell. MocLis is implemented in Linux; user space daemons and modified kernel. The measurement results show that the attachment time and handover time are short enough for practical use. TCP throughput in MocLis is faster than that in the tunneling based approaches.

An experimental network environment plays an important role to examine new protocols and systems. This paper proposes an IaC (Infrastructure as Code) based tool called LiON (Lightweight On-demand Networking) for constructing virtual networks on the Internet for various experiments. For virtual nodes, various types of virtualization technologies such as network namespace, container, and virtual machine are supported. VXLAN is employed for virtual links between virtual nodes. JSON (JavaScript Object Notation) is adopted as the configuration file format, which enables the experimenter to intuitively design virtual network topologies. Layer-3 protocol agnostic experimental networks can be constructed, which enable to examine non-IP protocol stacks. LiON is implemented in Python and shell script. The time for constructing a virtual network slightly increases as the number of virtual nodes increases. TCP throughput of a virtual link is approximately 97 % of that of a physical link.