Atsushi Tagami

Rapid Channel Zapping for IPTV Broadcasting with Additional Multicast Stream

This paper proposes a novel approach for improving channel zapping delay on IPTV broadcasting services. Channel zapping delay is a crucial issue for digital TV broadcasting, which entails audio/video data buffering before reproduction. Such delay could be mitigated in an IP environment if a receiver accelerated this buffering using additional burst transmissions from dedicated servers when a channel zap occurs. However, most conventional solutions are based on the unicast burst, which may cause an impulsive server/network load because channel zaps tend to happen simultaneously when programs are finished or suspended by commercial messages. To reduce this load, we propose a new multicast-based solution that takes into consideration the timing variation in channel zap on each receiver. We have confirmed a maximum 1-second reduction in the zapping delay using commercial multicast streams.

The Benefit of Information Centric Networking for Enabling Communications in Disaster Scenarios

Information Centric Networking (ICN) is a new paradigm where the network provides users with named content, instead of communication channels between hosts. This document outlines some research directions for Information Centric Networking with respect to applying ICN approaches for coping with natural or human- generated, large-scale disasters. We argue that ICN approaches have many benefits for enabling (or continuing) communication after a disaster has impaired a communication network. In this context, we present key research challenges and an overview of our ongoing research activities for applying Information Centric Networking to address these challenges.

Efficiently looking up non-aggregatable name prefixes by reducing prefix seeking

Content-Centric Networking (CCN) employs a hierarchical but location independent content naming scheme. While such a location independent naming brings various benefits including efficient content delivery, mobility, and multihoming, location independent name prefixes are hard to aggregate. This poses a serious scaling issue on the efficiency of looking up con-tent names in a huge Forwarding Information Base (FIB) by longest prefix matching, which requires seeking the longest matching prefix through all candidate prefix lengths. We propose a new scheme for efficiently looking up nonaggregatable name prefixes in a large FIB. The proposed scheme is based on the observation that the bottleneck of FIB lookup is the random accesses to the high-latency off-chip DRAM for prefix seeking and this can be reduced by exploiting the information on the longest matching prefix length in the previous hop.

Moderator-Controlled Information Sharing by Identity-Based Aggregate Signatures for Information Centric Networking

Information sharing services have been provided via common servers, which not only relay messages but also sometimes moderate them. A peer can become a moderator and control the distribution of messages belonging to his private message group. However, the physical transfer of a message is usually out of the peers control. Originator-signed signatures inherent in Information Centric Networking assure the integrity and provenance of messages exchanged among peers, which makes it possible to realize moderator-controlled information sharing in which a peer can become a moderator and control the distribution of his private message group as a trustable server. However, moderated content requires multiple signatures, which increases the size of the exchanged message and is inadequate, especially for short message services. We propose the use of Identity-Based Aggregate Signatures (IBAS) to decrease this overhead, and provide a proof-of-concept IBAS implementation for Named Data Networking (NDN). We also compare the performance of the proposed IBAS implementation with existing RSA signatures. An overhead reduction of approximately 45% to 60% compared to RSA signatures is achieved for an NDN packet in the proposed configuration. Because of the properties of the identity-based signature, this IBAS implementation is robust and works even during a disaster or when a trustable centralized server is not online.

Proposal on routing-based mobility architecture for ICN-based cellular networks

Forthcoming 5G networks raise an important research issue of seamless mobility management of cellular and non-cellular networks. Adopting Information Centric Networking (ICN) architecture as common mobility management is promising because existing mobility management mechanisms are complicated and incur large signaling overhead. This paper designs a routing-based mobility architecture to provide seamless mobility for the both networks. The architecture consists of routing during longer duration and anchor-less forwarding during shorter duration. A main contribution of the paper is that the architecture is designed by carefully considering how to port it to cellular networks with as few modifications to them as possible.

Congestion price for cache management in information-centric networking

We tightly integrate caching and congestion control into a unified approach to enhance user-centric performance in information-centric networking. To do that, we take advantage of the available congestion price fed back by congestion control to guide caching decision at each content router. The point is to let caching work in a longer time scale to alleviate congestion retrieving expensive content in terms of congestion cost. As a consequence, not only does caching increase throughput for users who request the cached content, but also it contributes to a large extent towards reducing network congestion, which benefits all other users who share the same congested parts of the network. Our use of existing congestion feedback signals eliminates the need for out-of-band congestion measurement such as bandwidth share computation which in reality might not reflect the true congestion state of the delivery paths. The proposed method yields positive performance gain in simulations compared with existing cache schemes.

Toy Block Networking: Easily Deploying Diverse Network Functions in Programmable Networks

Recent progress on virtualization and deeply programmable network technologies brings opportunities for network operators to flexibly deploy a diverse set of network functions as software-based middle boxes. We present a new deployment and configuration management framework for network functions, called toy block networking. In our framework, an operator can describe its network-wide deployment plan of various network functions by using a unified abstraction representing essential features of composition of network functions, without including the detail of the functions and specific configuration interfaces. This abstraction is based on a network-wide configuration graph that captures the relationships between various network functions, and thus network-wide consistency of their configurations is systematically validated by the framework. Our framework enables the network operator, like building toy blocks into a structure, to compose various network functions from different vendors into a unified network service plan, and deploy them in an operational network.

TCP Throughput Estimation by Lightweight Variable Packet Size Probing in CDMA2000 1x EV-DO Network

TCP throughput is one of the major communication quality metrics. In order to grasp this metric by active measurement while imposing a lower load, various estimation techniques have been proposed. These techniques are categorized as either equation-based or history-based; here we focus on the latter. Conventional history-based estimation techniques target a wired environment and estimate temporally. By contrast, we target a wireless environment and estimate spatially. For TCP throughput estimation using lightweight probing, we propose a new modeling whereby TCP throughput is determined by capacity and delay fluctuation. We evaluate our proposed modeling by conducting experiments in a commercial CDMA2000 1x EV-DO network. This evaluation empirically verified the validity of our model to estimate TCP throughput in a wireless environment with lightweight probing.

Efficient multipath forwarding and congestion control without route-labeling in CCN

One advantage of content-centric networking lies in its built-in support for multipath forwarding. In this paper, we propose a multipath forwarding strategy in order to fully utilize available bandwidth in a content-centric network. Using the proposed strategy, each intermediate router sensibly adjusts the amount of traffic forwarded over a given face (among a set of faces) associated with a content name based on the estimated available bandwidth it observes receiving the content through the face. Available bandwidth is sampled and estimated from the actual Data packet flow received at the face. The advantage of our method is that forwarding decision closely matches the congestion status of the forwarding face which results in efficient bandwidth utilization without biasing short round-trip time routes. What is more, by aggregating congestion control states at end users, our method requires neither route labeling nor any other kind of cooperation among routers on the delivery paths. Simulations confirm the effectiveness of our proposed scheme.

A Scalable Approach to Tomography-based Internet Measurement System

Network tomography enables network operators to detect and mitigate congestion by inferring internal states from multiple end-to-end active performance measurements. In previous studies, network tomography was applied to either small networks, e.g., a network which allows measurements in a full-mesh manner, or a reasonably large network, e.g., overlay-network with 100 end nodes. In contrast, our study was conducted to develop a large-scale tomography-based measurement system that scales with the nation-wide Internet. In this paper, we propose a novel architecture which consists of a probability measurement path selection method and a distributed database building method. The architecture provides network operators with look up services for measurement results so that they can achieve network-tomography applications.