HTTP streaming, which is currently based on the pull-based HTTP/1.1 protocol, has a tradeoff problem between overhead and adaptivity. We propose an adaptation method for adaptive streaming over the new HTTP/2 protocol, leveraging its server push feature. The method is based on a cost function that takes into account the number of pushed segments and the client buffer level. Experiment results show that the proposed method can improve the balance between the number of requests and buffer stability compared to existing methods.
Botnet involves various communication protocols and according to recent reports DNS TXT record has been used for botnet communications. However, we have never statistically analyzed the usage of DNS TXT record and the signatures of its malicious usage, thus, it is difficult to block out the malicious usage only. In this paper, we analyze the usage of the DNS TXT record and present statistical results obtained from more than 5 million real DNS TXT record queries with responses captured in our campus network for over 3 months. As a result, we filtered out 2,293 “Unconfirmed” usages of DNS TXT record queries and checked the queried domain name and the destination IP address in detail. Finally, we confirmed that it is effective to check the unknown usage of DNS TXT queries for detecting botnet communication.
Elastic Lambda Aggregation Network (EλAN), the next-generation access and aggregation integrated network, has been proposed. In EλAN, Optical Line Terminals (OLTs) are programmable, and Logical-OLTs (L-OLTs) can be migrated between different P-OLTs. L-OLT migration leads to enhance failure resistance and improve power saving. We have experimented L-OLT migration between P-OLTs in our laboratory. However it is necessary to evaluate how L-OLT migration time changes according to physical distance. Therefore we made an experiment of L-OLT migration in wide area network on JGN-X. This paper proposes estimation equation of L-OLT migration time. The equation leads to determine L-OLT arrangements considering time of L-OLT migration for physical distance.
Recently, the next generation (5-th generation: 5G) mobile communication systems have been actively investigated all over the world, in order to satisfy the strong demand for the faster and larger data communication. In 5G systems, not only UHF band but also SHF/EHF bands have been attracted much attention. Hence, frequency characteristics of radio propagation path loss have been studied. We have previously investigated outdoor to indoor (O2I) propagation characteristics in the 2.2 GHz band, and a modified path loss model instead of 3GPP model has been proposed. In this paper, in order to investigate frequency characteristics in terms of O2I propagation, the received power is measured for O2I propagation when considering 0.8, 2.2 and 4.7 GHz bands. Moreover, we investigate O2I propagation characteristics for different frequency bands by using O2I factor which denotes co-efficient versus transmit distance with logarithm expression when considering O2I propagation. Moreover, we consider O2I factor which is calculated by the least square approximation.
This paper proposes a reflector backed dipole antenna whose reflector is composed of frequency selective reflector (FSR) and the size of the FSR elements aligned in the both side columns is changed. Since the width of the frequency selective reflector, which is composed of an array of the frequency selective elements, is chosen discretely, it is difficult to design an arbitrary beamwidth of the reflector backed antenna because the beamwidth of the reflector backed dipole antenna can be adjusted by the size of the reflector. The proposed antenna configuration can achieve arbitrary beamwidth by using different size of the FSR elements aligned in the both side columns. This paper also shows the condition of the FSR element size aligned in the both side columns to obtain sector radiation pattern.