Thomas R. Henderson

The ns-3 Network Simulator

As networks of computing devices grow larger and more complex, the need for highly accurate and scalable network simulation technologies becomes critical. Despite the emergence of large-scale testbeds for network research, simulation still plays a vital role in terms of scalability (both in size and in experimental speed), reproducibility, rapid prototyping, and education. With simulation based studies, the approach can be studied in detail at varying scales, with varying data applications, varying field conditions, and will result in reproducible and analyzable results.

ns-3 project goals

This paper reports on the project plan to develop a new major version of the popular ns-2 networking simulator. The authors have organized an NSF-funded, four-year community infrastructure project to develop the next version of ns. The project will also be oriented towards community development and open source software practices to encourage participation from the broader research and educational community. The purpose of this paper is to expand on the goals and initial design concepts for this new software development effort.

Yet another network simulator

We report on the design objectives and initial design of a new discrete-event network simulator for the research community. Creating Yet Another Network Simulator (yans, http://yans.inria.fr/yans) is not the sort of prospect network researchers are happy to contemplate, but this effort may be timely given that ns-2 is considering a major revision and is evaluating new simulator cores. We describe why we did not choose to build on existing tools such as ns-2, GTNetS, and OPNET, outline our functional requirements, provide a high-level view of the architecture and core components, and describe a new IEEE 802.11 model provided with yans.

Host Identity Protocol (HIP): Connectivity, Mobility, Multi-Homing, Security, and Privacy over IPv4 and IPv6 Networks

The Host Identity Protocol (HIP) is an inter-networking architecture and an associated set of protocols, developed at the IETF since 1999 and reaching their first stable version in 2007. HIP enhances the original Internet architecture by adding a name space used between the IP layer and the transport protocols. This new name space consists of cryptographic identifiers, thereby implementing the so-called identifier/locator split. In the new architecture, the new identifiers are used in naming application level end-points (sockets), replacing the prior identification role of IP addresses in applications, sockets, TCP connections, and UDP-based send and receive system calls. IPv4 and IPv6 addresses are still used, but only as names for topological locations in the network. HIP can be deployed such that no changes are needed in applications or routers. Almost all pre-compiled legacy applications continue to work, without modifications, for communicating with both HIP-enabled and non-HIP-enabled peer hosts. The architectural enhancement implemented by HIP has profound consequences. A number of the previously hard networking problems become suddenly much easier. Mobility, multi-homing, and baseline end-to-end security integrate neatly into the new architecture. The use of cryptographic identifiers allows enhanced accountability, thereby providing a base for easier build up of trust. With privacy enhancements, HIP allows good location anonymity, assuring strong identity only towards relevant trusted parties. Finally, the HIP protocols have been carefully designed to take middle boxes into account, providing for overlay networks and enterprise deployment concerns. This article provides an in-depth look at HIP, discussing its architecture, design, benefits, potential drawbacks, and ongoing work.

The design of an output data collection framework for NS-3

An important design decision in the construction of a simulator is how to enable users to access the data generated in each run of a simulation experiment. As the simulator executes, the samples of performance metrics that are generated beg to be exposed either in their raw state or after having undergone mathematical processing. Also of concern is the particular format this data assumes when externalized to mass storage, since it determines the ease of processing by other applications or interpretation by the user. In this paper, we present a framework for the ns-3 network simulator for capturing data from inside an experiment, subjecting it to mathematical transformations, and ultimately marshaling it into various output formats. The application of this functionality is illustrated and analyzed via a study of common use cases. Although the implementation of our approach is specific to ns-3, this design presents lessons transferrable to other platforms.

Link-to-System Mapping for ns-3 Wi-Fi OFDM Error Models

The ns-3 simulator contains detailed models of the Wi-Fi MAC layer, including beaconing, rate control, collision avoidance, block acknowledgments, and many other features. However, it relies on abstraction at the physical layer to scale well; Wi-Fi frames are evaluated by specialized interference trackers and analytical error models to arrive at frame reception decisions on a frame-by-frame basis, rather than symbol-by-symbol. Analytical models can provide fairly tight bounds for simple scenarios (additive white Gaussian noise (AWGN) channels with single antennas and limited interference), but the industry relies on detailed link-level simulations to understand more complicated scenarios. This paper reports on an extensive campaign to conduct link simulations of Wi-Fi OFDM performance over AWGN and fading channels, using a commercial link simulator with Wi-Fi support, with results validated against published references. Next, we describe a specific implementation of a technique generally known as link-to-system-mapping, to allow a vector of per-subcarrier signal-to-noise ratios to be distilled into a single effective SNR value that can be used to determine performance using link simulation results of the AWGN channel. Finally, we report on the support of our link simulation results in a new ns-3 ErrorRateModel based on tables compiled from link simulation results. Our broader contributions are the link simulation programs themselves which allow others to reproduce and extend the basic tables that we provide, and flexibility in the ns-3 implementation to allow additional tables to be added over time.

Implementation and evaluation of licklider transmission protocol (LTP) in ns-3

This paper provides performance modeling and validation results for the the ns-3 model of the Licklider Transmission Protocol, the standard transport protocol used to provide transmission reliability in Delay Tolerant Networks (DTNs). DTNs are an emerging type of network used to provide communications in extreme environments characterized by very long round trip delays and intermittent connectivity. Evaluation of some target environments requires the use of modeling since high-fidelity testbeds can be impractical. To our knowledge, we provide the first LTP model for the ns-3 network simulator. In this paper, through a combination of simulation and real-time emulation, we verify and validate this new model of LTP and show that its performance is in line with previously published performance studies of LTP.