Yoshifumi Nishida

The Use of SCTP Failover Mechanism for Efficient Network Handover on Mobile IPv6

In the near future, mobile communication will become majority on the Internet according to quick progress of wireless technology and mobility protocols. Mobile IPv6 has been standardized at IETF and almost ready to deploy on the Internet. However, handover technology of Mobile IPv6 is still under development. Since Mobile IPv6 does not specify optimized handover mechanism, it takes certain period to complete handover. In this paper, we investigate a mechanism to minimize handover latency without any modification to Mobile IPv6. We take position that a mobile node will utilize multiple interfaces to achieve smooth handover. With multiple interfaces, the Internet access can be continued even while Mobile IPv6s movement is proceeded. SCTP is a transport protocol capable of handling multiple addresses for each session. A mobile node uses a home address as a primary address and another available address as a secondary address. The SCTP fails over to the secondary address while the primary address (i.e. home address) is inactive during handover. The advantage of this proposal is that it required modification to neither Mobile IPv6 and SCTP.

AMS: An Adaptive TCP Bandwidth Aggregation Mechanism for Multi-homed Mobile Hosts

Recently, the number of multi-homed hosts is getting large, which are equipped with multiple network interfaces to support multiple IP addresses. Although there are several proposals that aim at bandwidth aggregation for multi-homed hosts, few of them support mobility. This paper proposes a new framework called AMS: Aggregate-bandwidth Multi-homing Support. AMS provides functions of not only bandwidth aggregation but also mobility by responding to the changes of the number of connections during communication without the support of underlying infrastructure. To achieve efficient data transmission, AMS introduces a function called address pairs selection to select an optimal combination of addresses of the peer nodes. We implemented AMS in the kernel of NetBSD and evaluated it in our test network, in which dummynet was used to control bandwidth and delay. The measured results showed that AMS achieved ideal bandwidth aggregation in three TCP connections by selecting optimal address pairs.

Smooth slow-start: refining TCP slow-start for large-bandwidth with long-delay networks

The transmission control protocol (TCP) adopts some techniques that use network resources efficiently by estimating the characteristics and condition of the network. The slow-start algorithm is the primary technique for effective resource usage. The goal of slow-start is to establish a TCP connection in an optimum state for the network path quickly unless giving an excessive load to the network. However, in large-bandwidth with long-delay links such as satellite links, the slow-start algorithm does not work properly and causes substantial performance degradation. In this paper, we describe the problem of the current slow-start algorithm in large-bandwidth with long-delay networks. We propose a new slow-start algorithm that can increase network transfer performance for large bandwidth with long delay networks. We also implemented this algorithm on a network simulator for evaluation and it resulted in over a 60% efficiency compared to a normal slow start algorithm.

A Connectivity-Driven Retransmission Scheme Based On Transport Layer Readdressing

Migration between different wireless access networks often involves disconnected period, which is caused by passing an area of bad wireless coverage and potential overhead to switch the network on the network interface to connect to. The disconnected period can cause extra transmission delay due to the timer-driven retransmission behavior in the transport protocols, such as TCP and SCTP. We propose a new retransmission scheme to achieve better migration performance in SCTP, which is a newer connection-oriented and reliable transport protocol that is becoming popular. Our scheme minimizes the extra transmission delay by leveraging address reconfiguration operation in SCTP without involving other layers. It decreases the delay more than 5 seconds compared to the original SCTP when migration involves approximately ten-second disconnected period. The implementation of our scheme is already imported in FreeBSD.

SmSCTP: A Fast Transport Layer Handover Method Using Single Wireless Interface

Many handover techniques in the Internet have been introduced with the development of mobile computing technologies. Although many proposed handover schemes utilize multiple interfaces, having multiple interfaces can increase power consumption, device installation space and hardware costs of mobile devices. Therefore, we have been studying handover schemes for mobile nodes with a single wireless network interface. To achieve seamless and efficient handover, we focus on stream control transmission protocol (SCTP) which offers message-oriented, reliable and connection-oriented delivery transport service. Unlike other transport protocols such as TCP, SCTP can provide an end-to-end handover mechanism with a multi-homing feature. However, the handover mechanism in the current SCTP causes large handover delay especially when a mobile node has only one single wireless network interface. In this paper, we have investigated the current issues in the SCTP handover mechanism and propose a new handover scheme based on SCTP, which identifies a communication path as a pair of source and destination address. We also propose new data retransmission feature for smooth handover.

Protocol Design for All-IP Computer Architecture

In this paper, we present a new computer architecture called All-IP computer architecture, which realize a flexible computer re-configuration environment via IP networks. Our new IP-based protocols connect devices to the host computer that were previously limited to a physical attachment. To construct All-IP computer environment, we designed a protocol to manage and discover device resources on IP networks. We also evaluated a protocol called USB/IP, which is expected to be one of the device interconnection protocols in the All-IP computer architecture.

Connectivity-driven flow recovery for time-sensitive transport services

PR-SCTP provides a timeliness transport service. When the lifetime of the data specified by the application expires, the sender PR-SCTP gives up retransmitting the data, and transmits a Forward TSN chunk to make the receiver advance the Cumulative ACK point. However, on the mobile communication, connectivity of the nodes is intermittent. PRSCTP does not work properly in this case, thereby the timeliness transmission is impaired. In order to address this issue, we propose a new algorithm that transmits a Forward TSN triggered by readdressing events in SCTP associations. Our scheme allows PR-SCTP to restart transmission of data with lifetime smoothly regardless of duration of the connectivity disruption.