Pei Zheng

EMPOWER: a network emulator for wireline and wireless networks

The increasing need of protocol development environments and network performance evaluation tools gives rise to the research of flexible, scalable, and accurate network emulators. The desired network emulator should be able to facilitate the emulation of either wireline or wireless networks. In the case when network topology is critical to the underlying network protocol, the emulator should provide specific mechanisms to emulate network topology. In this paper, we present a distributed network emulation system EMPOWER, which not only can fulfill those requirements, but also can generate user-defined network conditions and traffic dynamics at packet level. EMPOWER is highly scalable in that each emulator node could be configured to emulate multiple network nodes. Some significant research issues such as topology mapping scheme and scalability of the emulator are discussed and addressed. Preliminary emulation results show that EMPOWER is capable of assisting the study of both wireless and wireline network protocols and applications.

EMWIN:: emulating a mobile wireless network using a wired network

Test and performance evaluation of protocols and algorithms in mobile wireless networks is known to be challenging. Due to the highly varying characteristics of mobile wireless networks, one cannot merely rely on either network simulation or a testbed. Network emulation provides a controllable and reproducible environment, yet it generally lacks the support for the emulation of network topology and mobility, which are extremely critical in mobile wireless network research. We introduce EMWIN, a new IP-based mobile wireless emulation system that can overcome those drawbacks. In EMWIN, a target mobile wireless network is precisely mapped to an emulation configuration in a laboratory private network consisting of several emulator nodes, each of which is able to emulate multiple mobile hosts. Moreover, the emulator node can be flexibly configured such that predefined network conditions and traffic dynamics can be generated in an automatic manner. With EMWIN, the mobility of the target mobile wireless network with a number of mobile nodes can be faithfully emulated in a wired network environment.

VMNet: Realistic Emulation of Wireless Sensor Networks

Many research activities on wireless sensor networks (WSNs) need detailed performance statistics about protocols, systems, and applications; however, current simulation tools and testbeds lack mechanisms to report these statistics realistically and conveniently. To address this need, we have developed a WSN emulator, VMNet. VMNet emulates networked sensor nodes at the level of CPU clock cycles and executes the binary code of real applications directly. It emulates the radio channel with loss and noise as well as emulates the peripherals in sufficient detail. Moreover, VMNet takes parameter values from the real world and logs detailed runtime information of emulated nodes. Consequently, the application performance, both in response time and in power consumption, is reported realistically in VMNet, as demonstrated by our comparison studies with real sensor networks

EMPOWER: a cluster architecture supporting network emulation

Network research generally requires a simulation or emulation environment to test protocol implementations, to evaluate the performance of a scheme or a system, and to study complicated and highly varying network operations. For large network simulation, simulators consume a large amount of time and memory; and its result is largely based on some modeling assumptions that may not hold in the real world. Emulators are difficult to scale for large network emulation because of the high cost of equipment if a one-to-one mapping scheme is employed. Otherwise, the target network has to be abstracted to a single router modeled with some performance metrics. We present a distributed IP network emulator cluster EMPOWER, which not only can be used to emulate a large network with a limited number of commodity computers, but also can generate user-defined arbitrary network conditions and traffic dynamics at packet level for specific test scenarios. EMPOWER is highly scalable in that each emulator node could be configured to emulate multiple network nodes, and the increment of the number of emulator nodes does not affect emulation validity. Some significant research issues such as network mapping and mobile wireless network emulation are discussed and addressed. Preliminary emulation results show that EMPOWER is capable of assisting the study of both wireline and wireless network protocols and applications.

Chapter 10 – Intrusion Response Systems: A Survey

Publisher Summary This chapter considers the distributed systems as composed of multiple services and the services interact with one another through standardized network protocols. It describes the primary Intrusion Response Systems (IRSs) and label each in one of the following four categories. IRSs, called static decision making, provides a static mapping of the alert from the detector to the response that is to be deployed. The second class, called dynamic decision making, reasons about an ongoing attack based on the observed alerts and determines an appropriate response to take. The third class, called intrusion tolerance through diverse replicas, provides masking of security failures through the use of diverse replicas concurrently for performing security critical functions. The fourth class includes IRSs meant to target specific kinds of attacks, with our focus being on distributed denial-of-service attacks. Then, we present a discussion on the nascent field of benchmarking of IRSs. Finally, the chapter presents five key areas in which IRSs need to evolve for a widespread adoption. In addition, it considers the metrics that are relevant for evaluating an IRS.

SODON: a high availability multi-source content distribution overlay

Multi-source content distribution and file download systems such as BitTorrent and Edonkey emerge as a better scheme than the traditional ftp systems in distributing files to very large scale systems. However, a major drawback of those systems is that they largely rely on a tracker server to maintain state information of a horde. Furthermore, if the peer holding all the pieces of a file leaves the system, there is a high probability that the other peers cannot download the entire file. We propose a scalable and highly available P2P multi-source content distribution system called SODON to solve those problems. SODON distributes all the pieces of a file from a seed to a number of carefully selected sub-seeds in order to guarantee a complete set of pieces that are available for a long time. The sub-seeds also work as sub-trackers to maintain the horde state information. As a result, the original tracker server is not overwhelmed by a large population of download requests. Our traces on BitTorrent and simulation result show that SODON is feasible to build, and the sub-seeding and sub-tracking schemes effectively reduce the tracker load while offering a comparatively high availability of shared files

EMPOWER: a scalable framework for network emulation

The development and implementation of new network protocols and applications need accurate, scalable, reconfigurable, and inexpensive tools for debugging, testing, performance tuning and evaluation purposes. Network emulation provides a fully controllable laboratory network environment in which protocols and applications can be evaluated against predefined network conditions and traffic dynamics. In this paper, we present a new framework of network emulation EMPOWER. EMPOWER is capable of generating a decent network model based on the information of an emulated network, and then mapping the model to an emulation configuration in the EMPOWER laboratory network environment. It is highly scalable not only because the number of emulator nodes may be increased without significantly increasing the emulation time or worrying about parallel simulation, but also because the network mapping scheme allows flexible ports aggregation and derivation. By dynamically configuring a virtual device, effects such as link bandwidth, packet delay, packet loss rate, and out-of-order delivery, can be emulated.

Optical Network Survivability

Publisher Summary This chapter gives a brief overview of optical network survivability. Engineering the network for survivability plays an increasingly important role in transport networks. Protection techniques are well established in Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) and include point-to-point, dedicated protection rings, and shared protection rings. Point-to-point protection schemes work for simple systems with diverse fiber routes between node locations. In addition, optical channel layer protection is needed if some channels are to be protected while others are not. Optical multiplex section (OMS) layer protection is more cost effective for those cases where all the traffic needs to be protected. The optical layer consists of the optical channel layer (or path layer), the OMS layer (or line layer), and the optical transmission section layer. The choice of protection schemes is dictated primarily by the service classes to be supported and by the type of equipment deployed. In the SONET/SDH world, protection is performed primarily by the SONET/SDH line terminals and add/drop multiplexers and not by digital cross connects.

CoStore: a reliable and highly available storage system using clusters

The CoStore cluster architecture is proposed to construct a reliable and highly available storage system. A prototype CoStore was implemented and its performance was measured with the cluster being mirrored in various network environments. The preliminary results demonstrate that there is little impact on performance if the cluster is mirrored in efficient campus network environments with high bandwidth and low latency. As a result the CoStore architecture considerably reinforces a storage systems preparedness for disaster recovery without sacrificing performance.

Accurate Emulation of Wireless Sensor Networks

Wireless sensor networks (WSNs) have a wide range of useful, data-centric applications, and major techniques involved in these applications include in-network query processing and query-informed routing. Both techniques require realistic environments and detailed system feedback for development and evaluation. Unfortunately, neither real sensor networks nor existing simulators/emulators are suitable for this requirement. In this design paper, we propose a distributed sensor network emulator, a Virtual Mote Network (VMNet), to meet this requirement. We describe the system architecture, the synchronization of the nodes and the virtual time emulation with a focus on mechanisms that are effective for accurate emulation.