Shortcuts through Colocation Facilities

Network overlays, running on top of the existing Internet substrate, are of perennial value to Internet end-users in the context of, e.g., real-time applications. Such overlays can employ traffic relays to yield path latencies lower than the direct paths, a phenomenon known as Triangle Inequality Violation (TIV). Past studies identify the opportunities of reducing latency using TIVs. However, they do not investigate the gains of strategically selecting relays in Colocation Facilities (Colos). In this work, we answer the following questions: (i) how Colo-hosted relays compare with other relays as well as with the direct Internet, in terms of latency (RTT) reductions; (ii) what are the best locations for placing the relays to yield these reductions. To this end, we conduct a large-scale one-month measurement of inter-domain paths between RIPE Atlas (RA) nodes as endpoints, located at eyeball networks. We employ as relays Planetlab nodes, other RA nodes, and machines in Colos. We examine the RTTs of the overlay paths obtained via the selected relays, as well as the direct paths. We find that Colo-based relays perform the best and can achieve latency reductions against direct paths, ranging from a few to 100s of milliseconds, in 76% of the total cases; 75% (58% of total cases) of these reductions require only 10 relays in 6 large Colos.Comment: In Proceedings of the ACM Internet Measurement Conference (IMC '17), London, GB, 201

Multicast Network Performance using Multiprotocol Label Switching Together with Signaling Standards

Este artículo expone los resultados de una evaluación del sistema de conmutación de etiquetas multiprotocolo (MPLS) como tecnología multidifusión (envío de datos desde una fuente a varios usuarios) utilizando el protocolo de reserva de recursos con extensiones de ingeniería de tráfico (RSVP-TE). Para determinar las ventajas de ésta implementación, el sistema se compara con el funcionamiento de una red de transmisión de data-gramas IP basada en el estándar independiente multienvío en modo denso (PIM-DM). Las simulaciones son realizadas utilizando los paquetes de software OPNET y GNS-3. Se concluye que la conmutación de etiquetas MPLS utilizando RSVP-TE posee ventajas muy superiores a otras arquitecturas. Dichas ventajas incluyen una respuesta más rápida ante fallas en los enlaces, menor retardo y fluctuación y la posibilidad de reservar ancho de banda para tráfico con prioridad. The present article shows the results of the evaluation of Multiprotocol Label Switching (MPLS) as a technology for the transfer of multicast traffic (sending data from one source to several users) through the use of signaling protocols such as RSVP-TE. To identify the advantages of such an implementation, the setup in this work is compared to a multicast IP network based on the PIM-DM protocol. Simulations were carried out using software packages such as OPNET and GNS-3. It was found that MPLS+RSVP-TE offers greater advantages over other architectures. Some of these advantages include quicker link-failure response, shorter delays and less jitter, and also the possibility to reserve bandwidth for priority traffic. Document type: Articl

Exploiting the Path Propagation Time Differences in Multipath Transmission with FEC

We consider a transmission of a delay-sensitive data stream from a single source to a single destination. The reliability of this transmission may suffer from bursty packet losses - the predominant type of failures in today's Internet. An effective and well studied solution to this problem is to protect the data by a Forward Error Correction (FEC) code and send the FEC packets over multiple paths. In this paper we show that the performance of such a multipath FEC scheme can often be further improved. Our key observation is that the propagation times on the available paths often significantly differ, typically by 10-100ms. We propose to exploit these differences by appropriate packet scheduling that we call `Spread'. We evaluate our solution with a precise, analytical formulation and trace-driven simulations. Our studies show that Spread substantially outperforms the state-of-the-art solutions. It typically achieves two- to five-fold improvement (reduction) in the effective loss rate. Or conversely, keeping the same level of effective loss rate, Spread significantly decreases the observed delays and helps fighting the delay jitter.Comment: 12 page

Exploiting the Path Propagation Time in Multipath Transmission with FEC

We consider a transmission of a delay-sensitive data stream from a single source to a single destination. The reliability of this transmission may suffer from bursty packet losses - the predominant type of failures in today's Internet. An effective and well studied solution to this problem is to protect the data by a Forward Error Correction (FEC) code and send the FEC packets over multiple paths. In this paper we show that the performance of such a multipath FEC scheme can often be further improved. Our key observation is that the propagation times on the available paths often significantly differ, usually by 10-100ms. We propose to exploit these differences by appropriate packet scheduling that we call `Spread'. We evaluate our solution with a precise, analytical formulation and trace-driven simulations. Our studies show that Spread substantially outperforms the state-of-the-art solutions. It typically achieves two- to five-fold improvement (reduction) in the effective loss rate. Or conversely, keeping the same level of effective loss rate, Spread significantly decreases the observed delays and helps fighting the delay jitter

An overlay architecture for high quality VoIP streams

Abstract — The cost savings and novel features associated with Voice over IP (VoIP) are driving its adoption by service providers. Unfortunately, the Internet’s best effort service model provides no quality of service guarantees. Because low latency and jitter is the key requirement for supporting high quality interactive conversations, VoIP applications use UDP to transfer data, thereby subjecting themselves to quality degradations caused by packet loss and network failures. In this paper we describe an architecture to improve the performance of such VoIP applications. Two protocols are used for localized packet loss recovery and rapid rerouting in the event of network failures. The protocols are deployed on the nodes of an application-level overlay network and require no changes to the underlying infrastructure. Experimental results indicate that the architecture and protocols can be combined to yield voice quality on par with the PSTN. I