Nikhil Handigol

Reproducible network experiments using container-based emulation

In an ideal world, all research papers would be runnable: simply click to replicate all results, using the same setup as the authors. One approach to enable runnable network systems papers is Container-Based Emulation (CBE), where an environment of virtual hosts, switches, and links runs on a modern multicore server, using real application and kernel code with software-emulated network elements. CBE combines many of the best features of software simulators and hardware testbeds, but its performance fidelity is unproven. In this paper, we put CBE to the test, using our prototype, Mininet-HiFi, to reproduce key results from published network experiments such as DCTCP, Hedera, and router buffer sizing. We report lessons learned from a graduate networking class at Stanford, where 37 students used our platform to replicate 18 published results of their own choosing. Our experiences suggest that CBE makes research results easier to reproduce and build upon.

Carving research slices out of your production networks with OpenFlow

1. SLICED PROGRAMMABLE NETWORKS OpenFlow [4] has been demonstrated as a way for researchers to run networking experiments in their production network. Last year, we demonstrated how an OpenFlow controller running on NOX [3] could move VMs seamlessly around an OpenFlow network [1]. While OpenFlow has potential [2] to open control of the network, only one researcher can innovate on the network at a time. What is required is a way to divide, or slice, network resources so that researchers and network administrators can use them in parallel. Network slicing implies that actions in one slice do not negatively affect other slices, even if they share the same underlying physical hardware. A common network slicing technique is VLANs. With VLANs, the administrator partitions the network by switch port and all traffic is mapped to a VLAN by input port or explicit tag. This coarse-grained type of network slicing complicates more interesting experiments such as IP mobility or wireless handover. Here, we demonstrate FlowVisor, a special purpose OpenFlow controller that allows multiple researchers to run experiments safely and independently on the same production OpenFlow network. To motivate FlowVisor’s flexibility, we demonstrate four network slices running in parallel: one slice for the production network and three slices running experimental code (Figure 1). Our demonstration runs on real network hardware deployed on our production network at Stanford and a wide-area test-bed with a mix of wired and wireless technologies.

Where is the debugger for my software-defined network?

The behavior of a Software-Defined Network is controlled by programs, which like all software, will have bugs - but this programmatic control also enables new ways to debug networks. This paper introduces ndb, a prototype network debugger inspired by gdb, which implements two primitives useful for debugging an SDN: breakpoints and packet backtraces. We show how ndb modifies forwarding state and logs packet digests to rebuild the sequence of events leading to an errant packet, providing SDN programmers and operators with a valuable tool for tracking down the root cause of a bug.

Energy-efficient directional routing between partitioned actors in wireless sensor and actor networks

Actor-actor communication is an important part of the functioning of wireless sensor-actor networks and enables the actor nodes to take coordinated action on a given event. Owing to various reasons such as actor mobility and low actor density, the actor network tends to get partitioned. The authors propose to use the underlying sensor nodes, which are more densely deployed, to heal these partitions. In order to maximise the utilisation of the limited energy available with the sensor nodes, a new routing protocol for actor-actor communication using directional antennas on the actor nodes is proposed. The authors contribution is threefold. First, using simulations they show that the problem of partitioning in the actor networks is significant and propose an architecture with directional antennas on actor nodes and sensor bridges to heal these partitions. Second, they identify the routing problem for this architecture based on a theoretical framework and propose centralised as well as distributed solutions to it. Third, they develop a routing protocol based on the distributed solution and show, using network simulations, that the proposed protocol not only heals the network partitions successfully, but also achieves high throughput and fairness across different flows, in addition to maximising the network lifetime.

A reliable data transport protocol for partitioned actors in Wireless Sensor and Actor Networks

In Wireless Sensor and Actor Networks (WSANs), effective Actor-Actor Communication (AAC) is an important requirement for the timely responses to events reported by the sensors. However, due to scattered nature of events, mobility of actor nodes, and low density of actor nodes, the network of actor nodes tends to get partitioned frequently. To provide effective AAC in such situations, the energy-constrained sensor nodes located between the partitioned actor nodes need to be utilized. This solution for healing the actor network partitions should involve minimal use of the sensor nodes so that the network lifetime is maximized. In this work, we propose an energy-efficient Actor-Actor Reliable Transport Protocol (A2RT) for WSANs with actor nodes equipped with directional antennas and dual radio interfaces. Our proposed transport protocol consists of a transport wrapper and a dynamic priority scheduler. Using simulations, we show that our transport wrapper achieves high reliability with minimum retransmissions both under static and dynamic network topology conditions. The results also show that the traffic scheduler of our protocol helps to achieve the goals of real-time delivery by maximizing the number of packets that meet the delay constraints.

Report on WREN 2009 -- workshop: research on enterprise networking

WREN 2009, the Workshop on Research on Enterprise Networking, was held on August 21, 2009, in conjunction with SIGCOMM 2009 in Barcelona. WREN focussed on research challenges and results specific to enterprise and data-center networks. Details about the workshop, including the organizers and the papers presented, are at http://conferences.sigcomm.org/ sigcomm/2009/workshops/wren/index.php. Approximately 48 people registered to attend WREN. The workshop was structured to encourage a lot of questions and discussion. To record what was said, four volunteer scribes (Nathan Farrington, Nikhil Handigol, Christoph Mayer, and KokKiong Yap) took notes. This report is a merged and edited version of their notes. Please realize that the result, while presented in the form of quotations, is at best a paraphrasing of what was actually said, and in some cases may be mistaken. Also, some quotes might be mis-attributed, and some discussion has been lost, due to the interactive nature of the workshop. The second instance of WREN will be combined with the Internet Network Management Workshop (INM), in conjunction with NSDI 2010; see http://www.usenix.org/event/ inmwren10/cfp/ for deadlines and additional information. Also note that two papers from WREN were re-published in the January 2010 issue of Computer Communication Review: “Understanding Data Center Traffic Characteristics,” by Theophilus A Benson, Ashok Anand, Aditya Akella, and Ming Zhang, and “Remote Network Labs: An On-Demand Network Cloud for Configuration Testing,” by Huan Liu and Dan Orban. 2. SESSION 1: SECURITY