Marwan Fayed

Virtual Network Migration on Real Infrastructure: A PlanetLab Case Study

Network virtualization enables the deployment of novel network architectures and services on existing Internet infrastructure. In addition, virtual networks (VNs) can share the resources in the physical substrate. To enable efficient resource reallocation and network agility, VNs must sometimes migrate, i.e., change their placements on a substrate network. While VN placement, and to a lesser extent migration, has been studied in the past, little attention has been devoted to deploying and evaluating these functions over a real infrastructure. In this paper, we study the VN migration problem based on network virtualization in PlanetLab. We create a tool, PL-VNM, that orchestrates the VN migration on PlanetLab for a given new VN placement. The design and deployment of the tool reveal challenges and constraints. Some are particular to PlanetLab while others apply more generally to any virtualized infrastructure. Most significantly, we find that while in principle one can specify a migration schedule (sequence of migration steps) as an input to our tool, certain PlanetLab features make VN migration scheduling very difficult if not infeasible. Our work leads to recommendations about the features of a general virtualization environment and specific recommendations for PlanetLab that enable VN migration and migration scheduling. We believe that the recommended features make long-term experiments and application deployments on PlanetLab and other realistic virtualized infrastructures possible.

TCP Hollywood: An unordered, time-lined, TCP for networked multimedia applications

Ossification of the transport-layer limits networked multimedia applications to use TCP or UDP, despite standardisation of new transport protocols that better support their requirements. To improve transport for these applications, we present TCP Hollywood, an unordered, time-lined, TCP variant designed to support real-time multimedia traffic while being widely deployable. Analysis of the protocol indicates that it increases the utility of the network in lossy conditions where total one-way delay is constrained, such as with telephony applications and low-latency video streaming. This allows retransmissions to be useful in cases where they are not with standard TCP, improving the timely good-put of the protocol and reducing overheads. Initial experiments show that TCP Hollywood is deployable on the Internet, successfully operating on all major fixed and mobile networks in the UK, with safe failure modes.

Binder: a system to aggregate multiple internet gateways in community networks

We present a novel system termed Binder that seamlessly aggregates multiple geographically distributed Internet gateways in community networks. The proxy based approach taken in Binder allows for applications on end-user devices to enjoy the benefits from gateway aggregation without requiring any modifications. Binder makes novel use of multipath TCP (MPTCP), and additionally leverages OpenVPN tunneling and loose source routing (in a limited form that avoids security concerns) as part of an easily deployable implementation. Binder supports flexible gateway aggregation without negative effects from packet reordering through its use of MPTCP and generalizes link aggregation mechanisms to handle distributed links. Our proof of concept evaluation of Binder using a real implementation over an emulation based lab testbed demonstrate its benefits in terms of bandwidth aggregation, load balancing and fault tolerance relative to common practice.

TCP goes to hollywood

Real-time multimedia applications use either TCP or UDP at the transport layer, yet neither of these protocols offer all of the features required. Deploying a new protocol that does offer these features is made difficult by ossification: firewalls, and other middleboxes, in the network expect TCP or UDP, and block other types of traffic. We present TCP Hollywood, a protocol that is wire-compatible with TCP, while offering an unordered, partially reliable message-oriented transport service that is well suited to multimedia applications. Analytical results show that TCP Hollywood extends the feasibility of using TCP for real-time multimedia applications, by reducing latency and increasing utility. Preliminary evaluations also show that TCP Hollywood is deployable on the public Internet, with safe failure modes. Measurements across all major UK fixed-line and cellular networks validate the possibility of deployment.

Aqua-Net: A flexible architectural framework for water management based on wireless sensor networks

Traditional techniques and technologies for water management will no longer be cost effective or efficient in meeting the demands and challenges of the coming years. In this paper we describe Aqua-Net, a wireless sensor networks (WSNs)-based architectural framework for an efficient and reliable water management application. We identify areas of research that we are currently engaged in. The proposed framework is a flexible and multi-tiered hybrid network architecture that consists of a large number of autonomous single-hop “sensor communities”, a traveling backbone network, and a data depot. The key elements of the proposed architecture are reconfigurability, fault-tolerance and modularity. The architecture also addresses practical considerations in operating such monitoring networks during floods and other natural disasters.

Distributed k-core decomposition of dynamic graphs

The k-core decomposition can be used to reveal structure in a graph. It is straight-forward to implement using a centralised algorithm with complete knowledge of the graph, but no distributed k-core decomposition algorithm has been published. We present a continuous, distributed, k-core decomposition algorithm for dynamic graphs, outline a proof of correctness, and give initial performance results. We briefly describe an application of this distributed k-core algorithm to landmark selection for compact routing.

Implementing Real-Time Transport Services over an Ossified Network

Real-time applications require a set of transport services not currently provided by widely-deployed transport protocols. Ossification prevents the deployment of novel protocols, restricting solutions to protocols using either TCP or UDP as a substrate. We describe the transport services required by real-time applications. We show that, in the short-term (i.e., while UDP is blocked at current levels), TCP offers a feasible substrate for providing these services. Over the longer term, protocols using UDP may reduce the number of networks blocking UDP, enabling a shift towards its use as a demultiplexing layer for novel transport protocols.

An Evaluation of Chord and Pastry Models in OverSim

Peer-to-peer (P2P) simulation frameworks are excellent tools for developing and testing P2P algorithms, however there has been very little work done on validation of the models within these frameworks. Validation of these models is an important issue, as without knowing the models are valid we can not necessarily rely on the results generated using such models. In this work we provide an independent evaluation of both the Chord and Pastry Distributed Hash Table (DHT) models within OverSim, and validate the models by comparison against results presented in the original Chord and Pastry papers.

Revisiting Planarity in Position-Based Routing for Wireless Networks

In this paper we investigate the limits of routing according to left- or right-hand rule (LHR). Using LHR, a node upon receipt of a message will forward to the neighbour that sits next in counter-clockwise order in the network graph. When used to recover from greedy routing failures, LHR guarantees success if implemented over planar graphs. This is often referred to as face-routing. In the current body of knowledge it is known that if planarity is violated then LHR is guaranteed only to eventually return to the point of origin. Our work begins with an analysis to enumerate all node configurations that cause intersections. A trace over each configuration reveals that left-hand rule is able to recover from all but a single case, the ‘umbrella’ configuration so named for its appearance. We use this information to propose the Prohibitive Link Detection Protocol (PLDP) that can guarantee delivery over non-planar graphs using standard face-routing techniques. As the name implies, the protocol detects and circumvents the ‘bad’ links that hamper LHR. The goal of this work is to maintain routing guarantees while disturbing the network graph as little as possible. In doing so, a new starting point emerges from which to build rich distributed protocols in the spirit of CLDP and GDSTR.

RemIX: A Distributed Internet Exchange for Remote and Rural Networks

The concept of the \ac{IXP}, an Ethernet fabric central to the structure of the global Internet, is largely absent from the development of community-driven collaborative network infrastructure. The reasons for this are two-fold. \acp{IXP} exist in central, typically urban, environments where strong network infrastructure ensures high levels of connectivity. Between rural and remote regions, where networks are separated by distance and terrain, no such infrastructure exists. In this paper we present RemIX a distributed \acp{IXP} architecture designed for the community network environment. We examine this praxis using an implementation in Scotland, with suggestions for future development and research.