We present Dionysus, a system for fast, consistent network updates in software-defined networks. Dionysus encodes as a graph the consistency-related dependencies among updates at individual switches, and it then dynamically schedules these updates based on runtime differences in the update speeds of different switches. This dynamic scheduling is the key to its speed; prior update methods are slow because they pre-determine a schedule, which does not adapt to runtime conditions. Testbed experiments and data-driven simulations show that Dionysus improves the median update speed by 53--88% in both wide area and data center networks compared to prior methods.

/pdf/dynamic-scheduling-of-network-updates-1fmucv9mvs.pdf

Dynamic scheduling of network updates

Parallel and distributed simulation tools are emerging that offer the ability to perform detailed, packet-level simulations of large-scale computer networks on an unprecedented scale. The state-of-the-art in large-scale network simulation is characterized quantitatively. For this purpose, a metric based on the number of packet transmissions that can be processed by a simulator per second of wallclock time (PTS) is used as a means to quantitatively assess packet-level network simulator performance. An approach to realizing scalable network simulations that leverages existing sequential simulation models and software is described. Results from a recent performance study are presented concerning large-scale network simulation on a variety of platforms ranging from workstations to cluster computers to supercomputers. These experiments include runs utilizing as many as 1536 processors yielding performance as high as 106 million PTS. The performance of packet-level simulations of web and ftp traffic, and denial of service attacks on networks containing millions of network nodes are briefly described, including a run demonstrating the ability to simulate a million web traffic flows in near real-time. New opportunities and research challenges to fully exploit this capability are discussed.

/pdf/large-scale-network-simulation-how-big-how-fast-34nm4molxz.pdf

Large-scale network simulation: how big? how fast?

Systems and methods for optimizing a polling interval to capture new or changed content at an application server in a wireless network are disclosed. In one aspect, embodiments of the present disclosure include a method, which may be implemented on a system, for polling the application server using a first polling interval, monitoring responses received from the polling of the application server, adjusting the first polling interval to a second polling interval for polling the application server and/or using the second polling interval for polling another resource delivering same or similar content as the application server.

Optimization of resource polling intervals to satisfy mobile device requests

A mobile device is provided, including: a synchronization module configured to receive, at the mobile device, activity data from an activity monitoring device via a wireless connection; an activity data processing module configured to process the activity data to determine an activity metric for a user; a notification generator configured to compare the activity metric against a predefined threshold, the predefined threshold being mapped to a notification message, determine, based on the comparison, that the activity metric has reached or exceeds the predefined threshold, and access an electronic calendar associated with the user to obtain electronic calendar data; a display; and, a notification presenter configured to display the notification message on the mobile device via the display responsive to determining that the activity metric has reached or exceeded the predefined threshold, a timing of the display of the notification message being determined based on the electronic calendar data.

Notifications on a user device based on activity detected by an activity monitoring device

In one aspect of the disclosed implementations, a device includes one or more motion sensors for sensing motion of the device and providing activity data indicative of the sensed motion. The device also includes one or more processors for monitoring the activity data, and receiving or generating annotation data for annotating the activity data with one or more markers or indicators to define one or more characteristics of an activity session. The device also includes one or more feedback devices for providing feedback, a notice, or an indication to a user based on the monitoring. The device further includes a portable housing that encloses at least portions of the motion sensors, the processors and the feedback devices.

Portable monitoring devices and methods of operating the same

A wireless communication device that has one or more applications resident on a computer platform, a wireless communication interface, a display, and a user interface that, at least, appears on the display and through which a user of the wireless communication device interacts with the computer platform. The display is configured to be selectively controlled by the specific user interfaces of one or more applications resident on the computer platform, and the one or more applications and/or an arbiter that is resident on the computer platform will determine which user interface of the one or more applications resident on the computer platform controls the display based upon a predetermined criteria when the user interfaces compete for control of the display.

Wireless communication device having deterministic control of foreground access of the user interface

We describe two major developments in the general network simulation integration system (Genesis): the support for BGP protocol in large network simulations and distribution of the simulation memory among Genesis component simulations. Genesis uses a high granularity synchronization mechanism between parallel simulations simulating parts of a network. This mechanism uses checkpointed simulation state to iterate over the same time interval until convergence. It also replaces individual packet data for flows crossing the network partitions with statistical characterization of such flows over the synchronization time interval. We had achieved significant performance improvement over the sequential simulation for simulations with TCP and UDP traffic. However, this approach cannot be used directly to simulate dynamic routing protocols that use underlying network for exchanging protocol information, as no packets are exchanged in Genesis between simulated network parts. We have developed a new mechanism to exchange and synchronize BGP routing data among distributed Genesis simulators. The extended Genesis allows simulations of more realistic network scenarios, including routing flows, in addition to TCP or UDP data traffic. Large memory size required by simulation software hinders the simulation of large-scale networks. Based on our new support of distributed BGP simulation, we developed an approach to construct and simulate networks on distributed memory using Genesis simulators in such a way that each participating processor possesses only data related to the part of the network it simulates. This solution supports simulations of large-scale networks on machines with modest memory size.

https://www.cs.rpi.edu/~szymansk/papers/pads03.bgp.pdf

Parallel network simulation under distributed Genesis

Rapid growth of computer network sizes and uses necessitate analysis of network application middleware in terms of its scalability as well as performance. In this paper we analyze a distributed network management middleware based on agents that can be dispatched to locations where they can execute close to the managed nodes. The described middleware operates between the network protocol layer and the application layer and uses standard TCP protocol and SNMP probes to interface the network. By aggregating requests from many users into a single agent, our system allows multiple managers to probe problem areas with minimal management traffic overhead. We discuss and quantify the benefits of the described middleware by implementing real-time network managers using our system.The main result of this paper is a comparison of scalability and efficiency of our agent-based management middleware and traditional SNMP-based data collection. To this end, we measured traffic in both real and simulated networks. In the latter case, we designed, used and described here a method of separating simulated application flow into separate subflows to simplify design of simulations.

/pdf/scalability-and-performance-of-an-agent-based-network-f3x5mdurtp.pdf

Scalability and performance of an agent-based network management middleware

A system and method for continually updating a large and substantially continually changing dataset that is accessed by multiple application threads, such as a group identity database of members in communication groups of wireless communication devices. A first server holds the group identity database and, as application threads on the first server access the database to set up group communications, a second server sends new group identity data to update the database, with the new data arriving as discrete, ordered blocks. A first server-resident data-index table is updated with the ordering information of the new data blocks, and a first server-resident checkpointing thread places the ordering information of the new data blocks into a checkpoint cache and checkpoints the ordering information as the new data blocks are updated into the group identity database and verifies the ordering (or version) of the data as against the data-index table.

Database architecture for supporting group communications among wireless communication devices

Aspects are directed to managing event distribution to applications within a wireless communications device. A first application of a plurality of applications installed on a platform of the wireless communications device is provisioned with a private address of an interface portion of a second application from among the plurality of applications. A registration message is received at the interface portion of the second application from the first application, the registration message requesting registration for event message distribution at the interface portion of the second application based on the provisioned private address. An event notifier portion of the second application registers the first application to receive event message distribution. Next, the event notifier portion of the second application receives an indication that an event for distribution has occurred, and the event notifier portion distributes a notification, indicating at least that an event has been detected, to each registered application.

Rashim Gupta

Papers

Wireless communication device having deterministic control of foreground access of the user interface

Parallel network simulation under distributed Genesis

Scalability and performance of an agent-based network management middleware

Database architecture for supporting group communications among wireless communication devices

Managing event distribution to applications within a wireless communications device