Kieran Mansley

Characterizing 10 Gbps network interface energy consumption

This paper quantifies the energy consumption in six 10 Gbps and four 1 Gbps interconnects at a fine-grained level, introducing two metrics for calculating the energy efficiency of a network interface from the perspective of network throughput and host CPU usage. It further compares the energy efficiency of multiport 1 Gbps to 10 Gbps interconnects.

Feedback, latency, accuracy: exploring tradeoffs in location-aware gaming

We are witnessing the development of large-scale location systems and a corresponding rise in the popularity of location-aware applications, especially games. Traditional computer games have pushed the limits of CPU and graphics card performance for many years and experience suggests that location-aware games will place similar demands upon location systems. Unlike traditional gaming platforms however, the mobile devices that interact with location systems are heavily constrained especially in the number of ways that feedback can be provided.In this paper we describe a location-aware, fast-paced, close quarters action game and use it to experiment with three key components of future location-aware gaming platforms: (i) the location system, (ii) the network to connect the mobile devices, and (iii) the feedback and computational capabilities of the mobile devices themselves.We investigate the tradeoffs that are possible between these components, the effect of the feedback channel and the suitability of Bluetooth as a network for mobile game devices.

Engineering a user-level TCP for the CLAN network

As networks and I/O systems converge and the bandwidth of networks increases, conventional approaches to networking are struggling to deliver the performance and flexibility required.CLAN (Collapsed LAN) is a high performance user-level network targeted at the server room. It supports RDMA and programmed I/O (PIO). We have implemented a set of IP based protocols at user level, and shown how true zero copy transmission (without modifying the sockets API) and reception can be achieved.In this paper we discuss the problems associated with placing protocol stacks at user level and the architectural decisions required to obtain high performance. We also introduce our work using the network gateway which connects CLAN to the Internet to assist a server cluster in protocol processing.

The Carrot Approach: Encouraging Use of Location Systems

The Active Bat system provides the ability to locate users and equipment with a high degree of accuracy and coverage. Despite this, participation is low. We are concerned that this is symptomatic of a fundamental problem in location-aware computing; specifically the lack of understanding about which applications are useful and what factors motivate people to use them.

Distributed computing with the CLAN network

CLAN (collapsed LAN) is a high performance user-level network targeted at the server room. It presents a simple low-level interface to applications: connection-oriented non-coherent shared memory for data transfer, and Tripwire, a user-level programmable content addressable memory (CAM) for synchronisation. This simple interface is implemented using only hardware state machines on the network interface controller (NIC), yet is flexible enough to support many different applications and communications paradigms. We show how CLAN is used to support a number of standard transport protocols and middleware: MPI, VIA, TCP/IP and CORBA. In each case we demonstrate performance that approaches,the underlying network. For TCP/IP we present our initial results using an in-kernel stack, and describe the architecture of our prototype Gigabit Ethernet/CLAN bridge, which demultiplexes Ethernet frames directly to user-level TCP/IP stacks via the CLAN network. For VIA we present a software implementation with better latency than a commercial VIA NIC implemented on ASIC technology.

TRIPWIRE: A SYNCHRONISATION PRIMITIVE FOR VIRTUAL MEMORY MAPPED COMMUNICATION

Existing user-level network interfaces deliver high bandwidth, low latency performance to applications, but are typically unable to support diverse styles of communication and are unsuitable for use in multiprogrammed environments. Often this is because the network abstraction is presented at too high a level, and support for synchronisation is inflexible. In this paper we present a new primitive for in-band synchronisation: the Tripwire. Tripwires provide a flexible, efficient and scalable means for synchronisation that is orthogonal to data transfer. We describe the implementation of a non-coherent distributed shared memory network interface, with Tripwires for synchronisation. This interface provides a low-level communications model with gigabit class bandwidth and very low overhead and latency. We show how it supports a variety of communication styles, including remote procedure call, message passing and streaming.