Srinivasan Seshan

Can user-level probing detect and diagnose common home-WLAN pathologies

By: 
Partha Kanuparthy, Constantine Dovrolis, Konstantina Papagiannaki, Srinivasan Seshan, Peter Steenkiste
Appears in: 
CCR January 2012

Common Wireless LAN (WLAN) pathologies include low signal-to-noise ratio, congestion, hidden terminals or interference from non-802.11 devices and phenomena. Prior work has focused on the detection and diagnosis of such problems using layer-2 information from 802.11 devices and special purpose access points and monitors, which may not be generally available. Here, we investigate a user-level approach: is it possible to detect and diagnose 802.11 pathologies with strictly user-level active probing, without any cooperation from, and without any visibility in, layer-2 devices?

Public Review By: 
Renata Teixeira

This paper addresses the emerging problem of troubleshooting WiFi pathologies in home networks (where devices connect via a single access point). The paper focuses on identifying three pathologies: low signal-to-noise ratio (SNR), hidden terminals, and congestion. Previous tools have used support of lower layers to identify these pathologies and hence are tied to specific hardware. Instead, this paper relies solely on user-level probing. It proposes techniques that distinguish the three pathologies based on probe pairs between an end-host connected to the WLAN and a server connected to the access point through an Ethernet connection. The paper evaluates the techniques in small testbed. All reviewers single out the novelty and promise of user-level probing to identify WLAN pathologies making this paper a great work-in-progress report. The reviewers also point out some shortcomings of the current solution and evaluation. The need to deploy a wired computer undermines the usability of the approach, because many home networks don’t have such a machine. Although the solution is mostly hardware and software agnostic, for the experiments to work the authors had to change the configuration of the WiFi driver. Thus, the tool requires knowledge of interfering features of the driver. Reviewers had other specific comments on some of the assumptions, the accuracy of the techniques, and a number of suggestions for future work. Authors and reviewers agree that we need further research before the technique presented in this paper can become a practical solution.

DIRC: Increasing Indoor Wireless Capacity Using Directional Antennas

By: 
Xi Liu, Anmol Sheth, Michael Kaminsky, Konstantina Papagiannaki, Srinivasan Seshan, and Peter Steenkiste
Appears in: 
CCR October 2009

The demand for wireless bandwidth in indoor environments such as homes and offices continues to increase rapidly. Although wireless technologies such as MIMO can reach link throughputs of 100s of Mbps (802.11n) for a single link, the question of how we can deliver high throughput to a large number of densely-packed devices remains an open problem. Directional antennas have been shown to be an effective way to increase spatial reuse, but past work has focused largely on outdoor environments where the interactions between wireless links can usually be ignored.

Donnybrook: Enabling Large-Scale, High-Speed, Peer-to-Peer Games

By: 
Ashwin Bharambe, John R. Douceur, Jacob R. Lorch, Thomas Moscibroda, Jeffrey Pang, Srinivasan Seshan, and Xinyu Zhuang
Appears in: 
CCR October 2008

Without well-provisioned dedicated servers, modern fast-paced action games limit the number of players who can interact simultaneously to 16-32. This is because interacting players must frequently exchange state updates, and high player counts would exceed the bandwidth available to participating machines. In this paper, we describe Donnybrook, a system that enables epicscale battles without dedicated server resources, even in a fastpaced game with tight latency bounds. It achieves this scalability through two novel components.

Packet Caches on Routers: The Implications of Universal Redundant Traffic Elimination

By: 
Ashok Anand, Archit Gupta, Aditya Akella, Srinivasan Seshan, and Scott Shenker
Appears in: 
CCR October 2008

Many past systems have explored how to eliminate redundant transfers from network links and improve network efficiency. Several of these systems operate at the application layer, while the more recent systems operate on individual packets. A common aspect of these systems is that they apply to localized settings, e.g. at stub network access links. In this paper, we explore the benefits of deploying packet-level redundant content elimination as a universal primitive on all Internet routers. Such a universal deployment would immediately reduce link loads everywhere.

Understanding and Mitigating the Impact of RF Interference on 802.11 Networks

By: 
Ramakrishna Gummadi, David Wetherall, Ben Greenstein, and Srinivasan Seshan
Appears in: 
CCR October 2007

We study the impact on 802.11 networks of RF interference from devices such as Zigbee and cordless phones that increasingly crowd the 2.4GHz ISM band, and from devices such as wireless camera jammers and non-compliant 802.11 devices that seek to disrupt 802.11 operation. Our experiments show that commodity 802.11 equipment is surprisingly vulnerable to certain patterns of weak or narrow-band interference.

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