Virtual RTCP: A Case Study of Monitoring and Repair for UDP-based IPTV Systems

IPTV systems have seen widespread deployment, but often lack robust mechanisms for monitoring the quality of experience. This makes it difficult for network operators to ensure that their services match the quality of traditional broadcast TV systems, leading to consumer dissatisfaction. We present a case study of virtual RTCP, a new framework for reception quality monitoring and reporting for UDP-encapsulated MPEG video delivered over IP multicast. We show that this allows incremental deployment of reporting infrastructure, coupled with effective retransmission-based packet loss repair

TCP smart framing: a segmentation algorithm to reduce TCP latency

TCP Smart Framing, or TCP-SF for short, enables the Fast Retransmit/Recovery algorithms even when the congestion window is small. Without modifying the TCP congestion control based on the additive-increase/multiplicative-decrease paradigm, TCP-SF adopts a novel segmentation algorithm: while Classic TCP always tries to send full-sized segments, a TCP-SF source adopts a more flexible segmentation algorithm to try and always have a number of in-flight segments larger than 3 so as to enable Fast Recovery. We motivate this choice by real traffic measurements, which indicate that today's traffic is populated by short-lived flows, whose only means to recover from a packet loss is by triggering a Retransmission Timeout. The key idea of TCP-SF can be implemented on top of any TCP flavor, from Tahoe to SACK, and requires modifications to the server TCP stack only, and can be easily coupled with recent TCP enhancements. The performance of the proposed TCP modification were studied by means of simulations, live measurements and an analytical model. In addition, the analytical model we have devised has a general scope, making it a valid tool for TCP performance evaluation in the small window region. Improvements are remarkable under several buffer management schemes, and maximized by byte-oriented schemes

Efficient Cooperative Anycasting for AMI Mesh Networks

We have, in recent years, witnessed an increased interest towards enabling a Smart Grid which will be a corner stone to build sustainable energy efficient communities. An integral part of the future Smart Grid will be the communications infrastructure which will make real time control of the grid components possible. Automated Metering Infrastructure (AMI) is thought to be a key enabler for monitoring and controlling the customer loads. %RPL is a connectivity enabling mechanism for low power and lossy networks currently being standardized by the IETF ROLL working group. RPL is deemed to be a suitable candidate for AMI networks where the meters are connected to a concentrator over multi hop low power and lossy links. This paper proposes an efficient cooperative anycasting approach for wireless mesh networks with the aim of achieving reduced traffic and increased utilisation of the network resources. The proposed cooperative anycasting has been realised as an enhancement on top of the Routing Protocol for Low Power and Lossy Networks (RPL), a connectivity enabling mechanism in wireless AMI mesh networks. In this protocol, smart meter nodes utilise an anycasting approach to facilitate efficient transport of metering data to the concentrator node. Moreover, it takes advantage of a distributed approach ensuring scalability

Timely and reliable packets delivery over Internet of Vehicles (IoVs) for road accidents prevention: a cross-layer approach

With the envisioned era of Internet of Things (IoTs), all aspects of Intelligent Transportation Systems (ITS) will be connected to improve transport safety, relieve traffic congestion, reduce air pollution, enhance the comfort of transportation and significantly reduce road accidents. In IoVs, regular exchange of current position, direction, velocity, etc., enables mobile vehicles to predict an upcoming accident and alert the human drivers in time or proactively take precautionary actions to avoid the accident. The actualization of this concept requires the use of channel access protocols that can guarantee reliable and timely broadcast of safety messages. This paper investigates the application of network coding concept to increase content of every transmission and achieve improved broadcast reliability with less number of retransmission. In particular, we proposed Code Aided Retransmission-based Error Recovery (CARER) scheme, introduced an RTB/CTB handshake to overcome hidden node problem and reduce packets collision rate. In order to avoid broadcast storm problem associated with the use of RTB/CTB packet in a broadcast transmission, we developed a rebroadcasting metric used to successfully select a vehicle to rebroadcast the encoded message. The performance of CARER protocol is clearly shown with detailed theoretical analysis and further validated with simulation experiments

Protocol-processing overhead on the performance of error recovery schemes in high-speed network environments

This paper investigates the effects of protocol-processing overhead on the performance of error recovery schemes in high-speed network environments. The investigated error recovery schemes are:• an edge-to-edge error recovery scheme, where retransmissions of erred packets only take place between source and destination nodes, and• a link-by-link error recovery scheme, where retransmissions only take place between adjacent switching nodes.For retransmission of erred packets, we consider both Go-Back-N and Selective-Repeat procedures in the analysis.The performance measures we obtain are the distribution of transfer delays and the loss probability of packets across a network. To obtain these measures, this paper develops a tandem queueing network model with feedbacks where each queue represents a protocol layer within a switching node, rather than a switching node as a whole.Numerical results show that for a network with very-high-speed/low-error-rate channels, an edge-to-edge scheme gives the smaller packet transmission delay than a link-by-link scheme for both Go-back-N and Selective-Repeat retransmission procedures, while keeping the packet loss probability sufficiently small