The available bandwidth (ABW) of a network path is a crucial metric for various applications, such as traffic engineering, congestion control, multimedia streaming, and path selection in software-defined wide-area networks (SDWAN). In recent years, a new class of measurement methods have been proposed to estimate the available bandwidth, decreasing-chirp-train methods. However, the performance and limitations of this new class of methods are neither well studied nor fairly compared beyond simulation studies. In this work, we implement Voyager, a modular framework that allows us to conduct a fair and thorough comparison of how a variety of modern bandwidth estimation methods perform under different network paths and traffic conditions. We shed light on the characteristics and limitations of the internal algorithms of various methods, and propose two new methods. We investigate the impact of various bottleneck types and traffic types, and we explore the performance of these methods on high speed links where interrupt coalescence can cause measurement noise. We finally test Voyager on long-distance Internet links and with live traffic and report our findings.

Measuring the Available Bandwidth (ABW) is an important function for traffic engineering, and in software-defined metro and wide-area network (SD-WAN) applications. Because network speeds are increasing, it is timely to re-visit the effectiveness of ABW measurement again. A significant challenge arises because of Interrupt Coalescence (IC), that network interface drivers use to mitigate the overhead when processing packets at high speed, but introduce packet batching. IC distorts receiver timing and decreases the ABW estimation. This effect is further exacerbated with software-based forwarding platforms that exploit network function virtualization (NFV) and the lower-cost and flexibility that NFV offers, and with the increased use of poll-mode packet processing popularized by the Data Plane Development Kit (DPDK) library. We examine the effectiveness of the ABW estimation with the popular probe rate models (PRM) such as PathChirp and PathCos++, and show that there is a need to improve upon them. We propose a modular packet batching mitigation that can be adopted to improve both the increasing PRM models like PathChirp and decreasing models like PathCos++. Our mitigation techniques improve the accuracy of ABW estimation substantially when packet batching occurs either at the receiver due to IC, DPDK based processing or intermediate NFV-based forwarding nodes. We also show that our technique helps improve estimation significantly in the presence of cross-traffic.

Demands for wide-area connectivity between enterprise site-edge networks and central office core networks/cloud data centers have grown rapidly. Various software defined wide area network (SD-WAN) solutions have been developed with the primary aim of improving WAN link utilization. However, mechanisms used by existing SD-WAN solutions fail to provide high reliability and performance required by today's edge to cloud applications. In this article, we present WAN-aware MPTCP which seamlessly aggregates multiple WAN links into a “big pipe” for better WAN resilience thus minimizing application performance degradation under WAN link failures. We leverage the congestion control of MPTCP to balance traffic across multiple WAN links. The key innovation is to combine LAN virtualization at end systems with WAN virtualization at SD-WAN gateways. Through evaluation in both emulated testbeds and real-world deployment, we demonstrate the performance gain of WAN-aware MPTCP in terms of resilience and throughput over existing SD-WAN solutions.

Software Defined Networking, or SDN, based networks are being deployed not only in testbed networks, but also in production networks. Although fault-tolerance is one of the most desirable properties in production networks, there are not much study in providing fault-tolerance to SDN-based networks. The goal of this work is to develop a fault tolerant SDN architecture that can rapidly recover from faults and scale to large network sizes. This paper presents CORONET, a SDN fault-tolerant system that recovers from multiple link failures in the data plane. We describe a prototype implementation based on NOX that demonstrates fault recovery for emulated topologies using Mininet. We also discuss possible extensions to handle control plane and controller faults.

OpenFlow is a great concept, but its original design imposes excessive overheads. It can simplify network and traffic management in enterprise and data center environments, because it enables flow-level control over Ethernet switching and provides global visibility of the flows in the network. However, such fine-grained control and visibility comes with costs: the switch-implementation costs of involving the switch's control-plane too often and the distributed-system costs of involving the OpenFlow controller too frequently, both on flow setups and especially for statistics-gathering.

Network device vendors have recently opened up the processing capabilities on their hardware platform to support third-party applications. In this paper, we explore the requirements and overheads associated with co-locating middlebox functionality on such computing resources on networking hardware. In particular, we use an example of TCP acceleration proxy (CHART) that improves throughput over networks with delay and loss. The CHART system, developed by HP and its partners provides enhanced TCP/IP performance and service quality guarantees by deploying performance accelerating proxies, which enables legacy clients to benefit by high-performance network service. Use of the TCP proxy, however, requires manual configuration on the clients changing http proxy and/or routing table settings. Can we remove the need to configure end-hosts by inserting a transparent TCP proxy in the path, without losing performance? To address this question, we implement the accelerator on HP's x86-based processing blade designed to integrate network applications within switch architecture as well as on low-end home routers with OpenWRT. We describe the implementation detail such as flow redirection for transparency and new mechanisms required for easy insertion of proxies in the network path. We also evaluate its performance on HP's experimental testbed in terms of throughput and additional processing overhead.

This paper describes Hash-Based Routing (HBR), an architecture that enhances Ethernet to support dynamic management for multipath networks in scalable datacenters. This work enhances HBR to support flow ensemble management for large-scale networks of arbitrary topology. Ensemble routing eliminates measurement and control for individual flows and instead manages using summary data thus providing a unique capability for reactive datacenter-wide network management. HBR provides seamless interoperability with Ethernet and supports the attachment of unmodified L2 hosts and devices including FCoE devices within converged fabrics. Simulation experiments demonstrate efficient multipath routing for a variety of scalable topologies. Optimized routing maintains efficiency in the presence of network faults and implements spatial Quality of Service to dynamically provision physical network hardware among co-hosted tenants or applications.

The OpenFlow framework enables flow-level control over Ethernet switching, as well as centralized visibility of the flows in the network. OpenFlow's coupling of these features comes with costs, however: the distributed-system costs of involving the OpenFlow controller on flow setups, and the switch-implementation costs of involving the switch's control plane too often.

Most datacenter networks are based on specialized edge-core topologies, which are costly to build, difficult to maintain and consume too much power. We propose enhancements to layer-two (L2) Ethernet switches to enable multipath L2 routing in scalable datacenters. This replaces an expensive router with commodity switches. Our hash-based routing approach reuses and minimally extends hardware structures in high-volume switches, while exposing a powerful network management inter-face for multipath load balancing, QoS differentiation, and resilience to faults. Simulation results demonstrate near-optimal load balancing for uniform and non-uniform traffic patterns, and effective management of large datacenter networks independent of the number of traffic flows.

Traditionally, in-network services like firewall, proxy, cache, and transcoders have been provided by dedicated hardware middleboxes. A recent trend has been to remove the middleboxes by deploying the network services into switch/router-integrated computing modules or separate server/blade machines. In this abstract, by using a web Ad-insertion application as an example, we demonstrate our in-network processing (INP) framework that orchestrates various computing resources and network devices and enables seamless and efficient deployments of network services.

Most datacenter networks are based on specialized edge-core topologies, which are costly to build, difficult to maintain and consume too much power. We propose enhancements to layer-two (L2) Ethernet switches to enable multipath L2 routing in scalable datacenters. Our hash-based routing approach reuses and minimally extends hardware structures in high-volume switches, while exposing a powerful network management interface for multipath load balancing, QoS differentiation, and resilience to faults.

This paper introduces the concept of inter-domain mobility, to allow users to migrate their connectivity between different network domains. Most current mobility techniques are not well suited to handle inter-domain mobility. We present L7-mobility, a simple extension of the current mobility practices for inter-domain mobility, which adds support for both hot and policy mobility. L7-mobility makes extensive use of our connection diversity framework and its connection manager to simplify implementation. We implemented L7-mobility in an HTTP proxy, which allowed us to evaluate the complexity, deployment and performance of this new technique.

MobileIP, the standard for Internet mobility, enables transparent mobility for a mobile node, but requires communication to take a multihop path through the node's Home Agent. Although a user with a multiple-interface mobile node may desire the ability to communicate locally, perhaps while disconnected from the Internet, MobileIP offers no such support.Contact Networking provides lightweight, localized network communication to a node with diverse network interfaces. The goal is to provide support for local connectivity equivalent to that provided by MobileIP for remote connectivity. The concept of link-layer awareness enables Contact Networking to tailor its operation to different links, using link-layer native services to implement abstract services when possible. Interface management and autoconfiguration insulate the user from concerns about the number and type of interfaces available.In this paper, we motivate the need for localized mobility, and present the design and architecture of Contact Networking. Details of our prototype implementation illustrate the complexities of providing a localized mobility facility.

This paper describes a novel approach to setting up peer to wireless links, such as IrDA, Bluetooth, and 802.11b. We explain how the lack of physical contact inherent in wireless creates new configuration challenges and ease of use issues, and we discuss the limitations of current wireless autoconfiguration techniques. We present co-link configuration and co-link activation, two techniques using wireless diversity to improve the performance of minimise the power consumption of autoconfiguration. We then describe the implementations of co-link, the simple IrDA connection point and the peer-to-peer co-link implemented within the connection diversity framework.

This paper describes a novel approach to using TCP/IP applications over IrDA (Infrared Data Association) and Bluetooth. First, we look into why so few applications are available over IrDA and what is necessary to make the use of those applications attractive to end-users. Then, we present a new scheme that enables the use of the IrDA communication layer by those applications in a transparent fashion with minimal overhead. We describe the various components necessary to implement such a scheme, IrNET, the name resolver and the discovery manager, and explain how we have implemented those components under Linux. We finish by showing a few examples of use of those components with real applications.

This paper describes a novel approach to using peer to peer wireless links, such as IrDA, Bluetooth and 802.11b. We explain the concept of wireless diversity and its impact on developers and users. We also explore the limitations of classical vertical handoff protocols, such as the need of an infrastructure. We describe our connection diversity framework, upon which is built P-Handoff. We introduce P-Handoff, a new handoff protocol for peer to peer links with fine granularity, which complements vertical handoff and allows to optimise connectivity through multiple wireless links; P-Handoff doesn't require an infrastructure and uses link layer events. We describe some features of our implementation under Linux.

This paper studies the impact of common interferers found in unlicensed bands on 802.11 and other CSMA systems. First, we describe those interferers and the MAC techniques used to combat them. Then, we present fragment adaptive reduction, a scheme to overcome the effect of non-CSMA repetitive interferers, and it's implementation in the SWAP protocol. We also describe a simple model of domestic microwave oven interference. We finish by some exhaustive simulations of the impact of microwave oven and other interferers on 802.11, which illustrate the benefits of the fragment reduction scheme.

This paper studies the impact on CSMA/CA traffic of a reduction of the dwell size, a fundamental parameter of some wireless LANs. First, we explain why we want to reduce the dwell size and what are the consequences. Then, we present some ways to overcome the overhead of short dwell, mostly based on fragmentation. We finish by some exhaustive simulations of the short dwell size impact and variations, and the way those fragmentation schemes improve the network performance.

In this paper we present a medium access control (MAC) protocol for a wireless LAN which is designed to support both isochronous (voice) and asynchronous (data) traffic. The protocol is designed for use in a frequency hopping system and uses a TDMA access protocol to support voice and a CSMA/CA access protocol to support data. A wireless LAN using this protocol can be operated as either an ad-hoc network (in which case only the data service is supported) or as a managed network under the control of a control point or base station (in which case the voice service is also supported).

This paper presents a scheme to improve the efficiency of radio MAC protocols in the case of broadcast and multicast transmissions, like TCP/IP multicasting. First, the reliability problems with broadcast packets and their consequences are analysed. Then the robust broadcast scheme is presented, which decreases the probability of loss of broadcast packets over MAC protocols based on CSMA/CA. Finally, the new protocol is simulated against other simple solutions to show how it performs.