Recognizable series is a model of a sequential machine. A recognizable series S is represented by a triple (λ,µ,γ), called a linear representation of S, where λ is a row vector of dimension n specifying the initial state, γ is a column vector of dimension n specifying the output at a state, and µ is a morphism from input words to nn matrices specifying the state transition. The output for an input word w is defined as λ(µw) γ, called the coefficient of w in S, and written as (S,w). We present an algorithm which constructs a reduced linear representation of an unknown recognizable series S, with coefficients in a commutative field, using coefficient queries and equivalence queries. The answer to a coefficient query, with a word w, is the coefficient (S, w) of w in S. When one asks an equivalence query with a linear representation (λ,µ,γ), if (λ,µ,γ) is a linear representation of S, yes is returned, and otherwise a word c such that λ (µc) γ(S, c) and the coefficient (S, c) are returned: Such a word c is called a counterexample for the query. For each execution step of the algorithm, the execution time consumed from the initial step to the current step is O(mN 4M), where N is the dimension of a reduced linear representation of S, M is the maximum time consumed by a single fundamental operation (addition, subtraction, multiplication or division), and m is the maximum length of counterexamples as answers to equivalence queries returned until that step.

This paper proposes a fast and scalable traffic monitoring system called Fast xFlow Proxy. For efficiently provisioning and operating networks, xFlow such as IPFIX and NetFlow is a promising technology for visualizing the detailed traffic matrix in a network. However, internet protocol (IP) packets in a large carrier network are encapsulated with various outer headers, e.g., layer 2 tunneling protocol (L2TP) or multi-protocol label switching (MPLS) labels. As native xFlow technologies are applied to the outer header, the desired inner information cannot be visualized. From this motivation, we propose Fast xFlow Proxy, which explores the complicated carrier's packet, extracts inner information properly, and relays the inner information to a general flow collector. Fast xFlow Proxy should be able to handle various packet processing operations possible (e.g., header analysis, header elimination, and statistics) at a wire rate. To realize the processing speed needed, we implement Fast xFlow Proxy using the data plane development kit (DPDK) and field-programmable gate array (FPGA). By optimizing deployment of processes between DPDK and FPGA, Fast xFlow Proxy achieves wire rate processing. From evaluations, we can achieve over 20 Gbps performance by using a single server and 100 Gbps performance by using scale-out architecture. We also show that this performance is sufficiently practical for monitoring a nationwide carrier network.

A new mobility management architecture is proposed to optimize end-to-end routes for mobile nodes (MNs) and mobile routers (MRs) within a nested mobile network environment. By applying local network mobility management mechanisms based on Hierarchical Mobile IPv6 (HMIPv6) to a mobile network, the proposed approach can optimize the route to the mobile network effectively. Combining the proposed route optimization methods and HMIPv6 functionality can enable it to provide more effective route optimization, reducing the burden of location registration for handovers. A route optimization method for local fixed nodes in a mobile network has also been developed by adding proxy mobile node and correspondent node functions to the MRs. Numerical evaluations on mean route length and traffic routed through network nodes demonstrate the effectiveness and applicability of the proposed methods especially in large-scale networks.

With the spread of broadband and wireless Internet access, there is a growing need for a nomadic network environment that enables the use of network services anywhere, via various access media. In a nomadic network environment, however, the connectivity is decreased because users move among different access networks, and the bandwidth is narrow and fluctuating, especially for radio propagation in wireless networks. To solve these problems, we propose a multilink system with three key functions: IPinIP tunneling, dynamic distribution of packets, and reordering of distributed packets. In particular, our distribution function includes a novel algorithm based on available bandwidth estimation. A prototype of our system was evaluated through experiments using real wireless environments and its efficiency is discussed.