Austin Hanley

Distributed Storage-Assisted Data-Driven Overlay Network for P2P VoD Services

Providing VCR-like operations in peer-to-peer (P2P) environments is a significant challenge. This paper proposes a distributed storage-assisted data-driven overlay network (SDNet) to support P2P video-on-demand (VoD) services. It integrates two networks: a data-driven overlay network (DONet) and a multi-way tree. DONet is enhanced and used for the routine video distribution based on the buffer overlapping mechanism and gossip protocol. A novel algorithm which uses a multi-way tree structure and extra pre-fetching buffers at the nodes is proposed to support efficient VoD operations. Videos are divided into uniform segments, pre-fetched and stored in a distributed manner along the tree topology. The cooperation between DONet-based video delivery and the tree-located multimedia components enable multimedia streaming interactive commands to be performed efficiently. This paper presents and discusses the structure of SDNet and the distributed storage scheme and details the cooperation procedure. Simulation-based testing results show how the proposed SDNet is an efficient interactive streaming solution in a P2P environment.

SCTP Performance Issue on Path Delay Differential

This paper studies the effect of path delay on SCTP performance. It focuses on the SCTP fast retransmit algorithm and demonstrates that the performance in the current retransmission strategy will degrade acutely when the secondary path delay is less than the primary path delay at a certain level. The performance degradation is due to the disordered SACKs and constant congestion window size during the fast retransmit phase. Some modifications aimed at these problems are proposed and evaluated. This paper also identifies that the cause of the performance degradation in SCTP is a result of the single path configuration oriented design of the current fast retransmit algorithm. Several fast retransmission strategies are evaluated for different path delay and bandwidth configurations.

A Balanced Tree-Based Strategy for Unstructured Media Distribution in P2P Networks

Most research on P2P multimedia streaming assumes that users access video content sequentially and passively. Unlike P2P live streaming in which the peers start playback from the current point of streaming when they join the streaming session, in P2P video-on-demand streaming VCR-like operations such as forward, backward, and random-seek have to be supported. Providing this level of interactive streaming service in a P2P environment is a significant challenge. This paper proposes a balanced binary tree-based strategy for unstructured video-on- demand distribution in P2P networks (BBTU). BBTU assumes videos can be divided into several segments which can be fetched from different peers. BBTU involves two steps: 1) balance binary tree construction based on a prefetching algorithm in order to support interactivity; 2) unstructured video dissemination over network based on gossip protocol, which is the overlay for video distribution. Analysis and simulation show how BBTU is an efficient interactive streaming solution in P2P environment.

Performance Evaluation of Distributing Real-Time Video Over Concurrent Multipath

Recent research on Concurrent Multipath Transfer (CMT) and CMT with a Potentially-Failed destination state (CMT-PF) uses the transport layer multi-homing protocol Stream Control Transmission Protocol (SCTP) to increase application throughput by distributing transmitted data across multiple end-to-end paths. This paper investigates and evaluates the performance of CMT with Partial Reliability (CMT-PR) and CMT-PF with Partial Reliability (CMT-PF-PR), novel extensions of SCTP for real-time video distribution. The Evalvid-CMT platform was implemented in the University of Delawares SCTP/CMT ns-2 module to perform emulation experiments in order to compare CMT and CMT-PR, CMT-PF and CMT-PF-PR,respectively. The results presented in the paper show how the CMT-PR and CMT-PF-PR outperform CMT and CMT-PF respectively. Consequently the former are suggested as strategies for real-time video concurrent multipath transmissions.

Comparative Study of Real-Time Multimedia Transmission over Multi-homing Transport Protocols

The availability of multimedia applications suitable for deployment using 3G and GPRS networks has led to a requirement for end-to-end quality of service. More efficient mechanisms are needed in order to provide the required end user quality of service in wireless data networks. This paper investigates the performance implications of transmitting real-time multimedia content over a multi-homed transport protocol in a manner which is tolerant of network failure. It evaluates video quality with different retransmission policies combined with various path failure detection thresholds, path bandwidths, delays and loss rate conditions through Partial Reliable Stream Control Transmission Protocol (PR-SCTP). A solution called Evalvid-SCTP, which is a trace driven simulation of MPEG-4 video over SCTP, was designed to achieve the performance evaluation.

Analysis of Real-time Multimedia Transmission over PR-SCTP with Failover Detection Delay and Reliability Level Differential

The growing availability of different wireless access technologies provides the opportunity for real-time distribution of multimedia content using multi-homing technology. Investigating the behaviors and quality of such applications under heavy network load is necessary. This paper studies the effect of path failure detection threshold and reliability level on Stream Control Transmission Protocol Partial Reliability Extension (PR-SCTP) performance in symmetric and asymmetric path conditions respectively with different path loss rates. The platform Evalvid-SCTP implemented in the University of Delaware’s SCTP ns-2 module performs the emulation experiment.

An Analysis of Alterations to the SCTP RTO Calculation Mechanism for WLAN Environments

As a connection oriented transport layer protocol the Stream Control Transmission Protocol (SCTP) inherits many of the features of the Transmission Control Protocol (TCP) including the mechanism by which Retransmission Timeout (RTO) is calculated. Previous investigations have established that the mechanism through which SCTP calculates RTO is inappropriate in Wireless LAN (WLAN) environments. This paper investigates the performance implications of changes to the SCTP RTO calculation mechanism. In particular alterations to the parameters α, the smoothing factor, and β, the delay variance factor are investigated. Results indicate that performance improvements are achievable through careful selection of α and β values. Throughput improvements of 63% over the default mechanism defined in RFC 4960 are described. These performance improvements however, while significant, still can not address the switchover delays which result from the distortions caused by continuously increasing RTT values in WLAN environments.

Performance analysis of multi-homed transport protocols with network failure tolerance

The performance of multi-homed transport protocols tolerant of network failure is studied. It evaluates the performance of different retransmission policies combined with path failure detection thresholds, infinite or finite receive buffers for various path bandwidths, delays and loss rate conditions through stream control transmission protocol simulation. The results show that retransmission policies perform differently with different path failure detection threshold configurations. It identifies that retransmission of all data on an alternate path with the path failure detection threshold set to zero performs the best in symmetric path conditions but its performance degrades acutely in asymmetric path conditions even when the alternate path delay is shorter than the primary path delay. It illustrates that retransmission of all data on the same path with the path failure detection threshold set to one or zero gives the most stable performance in all path configurations.

Path Selection of SCTP Fast Retransmission in Multi-homed Wireless Environments

In heterogeneous wireless network environments, network connections of a device may have a significant differential. This paper studies the effect of path bandwidth differential on the performance of fast retransmission strategies in Multi-homing environments. It identifies that fast retransmission on an alternate path may cause receive buffer blocking when path bandwidth differential is significant and the receive buffer is limited. A theoretical model is proposed for selecting retransmission path during the fast retransmission phase, which is based on receive buffer and path conditions. The model is verified through simulations with various path differentials.

Transmission scheduling for multi-homed transport protocols with network failure tolerance

In heterogeneous network environments, the network connections of a multi-homed device may have significant bandwidth differential. For a multi-homed transmission protocol designed for network failure tolerance, such as SCTP, path selection algorithms for data transmission drastically affect performance. This article studies the effect of path bandwidth differential on the performance of retransmission strategies in multi-homing environments. It identifies that fast retransmission on an alternate path may cause receive buffer blocking when path bandwidth differential is significant and the receive buffer is limited. A theoretical model is proposed for selecting retransmission path during the fast retransmission phase, based on receive buffer and path conditions. From these observations and analysis results, this article proposes that path selection strategies for transmitting new data and retransmitted data should be decoupled. A new path selection scheme is proposed and evaluated through SCTP simulations.