Ju-Won Park

TCP-ROME: A transport-layer parallel streaming protocol for real-time online multimedia environments

Real-time multimedia streaming over the Internet is rapidly increasing with the popularity of user-created contents, Web 2.0 trends, and P2P (peer-to-peer) delivery support. While many homes today are broadband-enabled, the quality of experience (QoE) of a user is still limited due to frequent interruption of media playout. The vulnerability of TCP (transmission control protocol), the popular transport-layer protocol for streaming in practice, to the packet losses, retransmissions, and timeouts makes it hard to deliver a timely and persistent flow of packets for online multimedia contents. This paper presents TCP-real-time online multimedia environment (ROME), a novel transport-layer framework that allows the establishment and coordination of multiple many-to-one TCP connections. Between one client with multiple home addresses and multiple co-located or distributed servers, TCP-ROME increases the total throughput by aggregating the re- sources of multiple TCP connections. It also overcomes the band- width fluctuations of network bottlenecks by dynamically coordinating the streams of contents from multiple servers and by adapting the streaming rate of all connections to match the bandwidth requirement of the target video.

Virtual-node-based multicast routing and wavelength assignment in sparse-splitting optical networks

This paper investigates several problems associated with optical multicast routing and wavelength assignment in sparse-splitting optical networks for interactive real-time media distribution. Unfortunately, the constrained multicast routing with optimized wavelength assignment leads to NP-complete condition. Thus, in this paper, a virtual-node-based multicast routing algorithm is first proposed to satisfy the requirements of interactive real-time multicasting as well as the constraints from underlying optical networks. For the constructed multicast tree, we then associate an effective wavelength assignment algorithm. The experimental results show that the proposed algorithm combination performs well in terms of (1) the wavelength channel cost, (2) the maximum variation of inter-destination node delays, (3) the signal quality, and (4) the number of wavelength conversions.

Open media service architecture for advanced collaboration environments

Advanced collaboration environments are extensively utilized for distance learning, e-science, and other distributed global collaboration events. In such environments, high-quality and seamless media services play an important role in improving the quality of user experience to participants. In this paper, to support high-quality media-based services, we design open media service architecture for advanced collaboration environments, by combining the open interface for state-of-the-art media tools, the performance monitoring tools for devices and networks, and application-level adaptation schemes for media streaming. By implementing the proposed architecture on top of an open-source Access Grid (AG) collaboration toolkit, we verify that high-quality collaboration among several collaboration sites can be effectively realized over a multicast-enabled network testbed with improved media quality experience.

TCP-ROME: A Transport-Layer Approach to Enhance Quality of Experience for Online Media Streaming

Live streaming of multimedia content over the Internet is rapidly increasing, e.g. with the Web 2.0 and via peer-to-peer systems. While many homes today are equipped with sufficient bandwidth (DSL) to support high quality live streaming, the quality of experience of a user is dismal: the video resolution and size is small and the displaying is often interrupted. One of the key problems arises because TCP is used as the underlying transport layer protocol: packet loss, retransmissions and timeouts prevent TCP from delivering a timely, steady flow of packets and thus inhibits the provision of online multimedia content. This paper presents TCP-ROME, a novel transport-layer framework that allows an establishment of multiple TCP connections between one client with possibly multiple home addresses and multiple co-located or distributed servers. The download over multiple TCP connections increases the total throughput by aggregating the resources of multiple TCP connections. Moreover, TCP-ROME provides the means to overcome bandwidth fluctuations and network bottlenecks by dynamically coordinating the downloaded content from the different servers and by coordinating and adapting the streaming rate of the different connections to meet the bandwidth requirements of the video.

End-to-end monitoring service for multicast-based high-quality real-time media delivery

As the demand for high-quality real-time media service through multicast-enabled AG (access grid) increases, the end-to-end QoS (quality of service) provisioning of the media service has become very important. To guarantee the end-to-end QoS, it is essential to monitor the time-varying status of both network (i.e., delay, jitter and loss) and system metrics (i.e., CPU and memory utilization). In this paper, we propose a new service for the AG, to monitor the time-varying conditions of both multicast networks and the AG node systems. When the performance of the AG degrades, the proposed monitoring attempts to pinpoint the cause of performance degradation and explores corresponding reactions to improve the end-to-end performance of the AG. The experimental results show that the proposed monitoring service is really useful in improving the quality of media service for the AG.

QoS-driven multicast routing in sparse-splitting optical networks

This paper investigates the quality-of-service (QoS)-driven multicast routing problem in a sparse-splitting optical network. The main objective is to minimize the total cost of wavelength channels utilized by the light-tree while satisfying required QoS parameters. In this paper, both the optical-layer constraints (e.g., optical signal power) and application-layer requirements (e.g., end-to-end delay and inter-destination delay variation) are considered as the QoS parameters. First, integer linear programming (ILP) formulations to solve the optimal multicast routing problem with the given QoS parameters are presented. Solving the ILP formulations for large-scale networks can easily overwhelm the capabilities of state-of-the-art computing facilities, and hence, a heuristic algorithm is proposed to construct a feasible light-tree that satisfies the required QoS parameters in large-scale networks. Simulation results demonstrate the performance of the proposed heuristic algorithm in terms of the cost of utilized wavelength channels.

A futuristic service framework for flexible media-oriented service composition in future internet

As the Internet evolves into an irreplaceable service-oriented infrastructure, a key issue to consider is that of creating and managing a rich variety of novel services while keeping aware of individual requirements for QoE (Quality of Experience) guarantee. In this paper, we present our on-going effort of designing a futuristic service framework for flexible media-oriented service composition in Future Internet. In our framework, media-oriented contents, generic service, and programmable infrastructure cooperate to flexibly compose media-oriented services with diverse requirements according to users context and resource heterogeneity.

Quality monitoring for real-time IP media transport over multi-point delivery environment

As the demand for real-time IP media transport over multi-point delivery environments increases, it is essential to monitor the time-varying status of both network metrics (i.e., delay, jitter, and loss) and system metrics (i.e., CPU and memory utilization). In this paper, we propose and implement a new monitoring system for the high-quality real-time media delivery over multicast-enabled network. It monitors the time-varying conditions of both the multicast network and the node system. When the media performance degrades, the proposed monitoring system attempts to pinpoint the cause of performance degradation to improve the end-to-end performance. The experimental results show that we can effectively infer the cause of performance degradation using the implemented prototype of the proposed monitoring system.

Opportunistic Fair Parallel Download Protocol

Parallel download protocols that establish multiple TCP connections to distributed replica servers have the potential to reduce file download time and to achieve a server-side load balancing. Unfortunately, parallel download protocols are also inherently unfair towards single-flow downloads and may even starve them. This paper presents TCP-ROME, a parallel download protocol that allows a dynamic mitigation of throughput and fairness. The key novelty is a receiver-based framework that allows a dynamic adjustment of the congestion and rate control of each subconnection. TCP-ROME offers two usage modes: a binary mode where the congestion control of each subconnection can be switched between a TCP-fair rate (high priority) and at a TCP-LP fair rate (low priority), and a more complex range mode where the aggregated throughput aims at meeting a specified target rate. Apart from the protocol specification, this paper develops novel analytical throughput models for TCP-LP and for TCP-ROME. The models are validated via simulations. Extensive simulation scenarios show the flexibility of TCP-ROME in mitigating performance for fairness.

Hybrid monitoring scheme for end-to-end performance enhancement of multicast-based real-time media

As real-time media applications based on IP multicast networks spread widely, end-to-end QoS (quality of service) provisioning for these applications have become very important. To guarantee the end-to-end QoS of multi-party media applications, it is essential to monitor the time-varying status of both network metrics (i.e., delay, jitter and loss) and system metrics (i.e., CPU and memory utilization). In this paper, targeting the multicast-enabled AG (Access Grid) a next-generation group collaboration tool based on multi-party media services, the applicability of hybrid monitoring scheme that combines active and passive monitoring is investigated. The active monitoring measures network-layer metrics (i.e., network condition) with probe packets while the passive monitoring checks both application-layer metrics (i.e., user traffic condition by analyzing RTCP packets) and system metrics. By comparing these hybrid results, we attempt to pinpoint the causes of performance degradation and explore corresponding reactions to improve the end-to-end performance. The experimental results show that the proposed hybrid monitoring can provide useful information to coordinate the performance improvement of multi-party real-time media applications.