242 research outputs found
Interfacing a high performance disk array file server to a Gigabit LAN
Our previous prototype, RAID-1, identified several bottlenecks in typical file server architectures. The most important bottleneck was the lack of a high-bandwidth path between disk, memory, and the network. Workstation servers, such as the Sun-4/280, have very slow access to peripherals on busses far from the CPU. For the RAID-2 system, we addressed this problem by designing a crossbar interconnect, Xbus board, that provides a 40MB/s path between disk, memory, and the network interfaces. However, this interconnect does not provide the system CPU with low latency access to control the various interfaces. To provide a high data rate to clients on the network, we were forced to carefully and efficiently design the network software. A block diagram of the system hardware architecture is given. In the following subsections, we describe pieces of the RAID-2 file server hardware that had a significant impact on the design of the network interface
CC-Fuzz: Genetic algorithm-based fuzzing for stress testing congestion control algorithms
Congestion control research has experienced a significant increase in
interest in the past few years, with many purpose-built algorithms being
designed with the needs of specific applications in mind. These algorithms
undergo limited testing before being deployed on the Internet, where they
interact with other congestion control algorithms and run across a variety of
network conditions. This often results in unforeseen performance issues in the
wild due to algorithmic inadequacies or implementation bugs, and these issues
are often hard to identify since packet traces are not available.
In this paper, we present CC-Fuzz, an automated congestion control testing
framework that uses a genetic search algorithm in order to stress test
congestion control algorithms by generating adversarial network traces and
traffic patterns. Initial results using this approach are promising - CC-Fuzz
automatically found a bug in BBR that causes it to stall permanently, and is
able to automatically discover the well-known low-rate TCP attack, among other
things.Comment: This version was submitted to Hotnets 202
System Support for Bandwidth Management and Content Adaptation in Internet Applications
This paper describes the implementation and evaluation of an operating system
module, the Congestion Manager (CM), which provides integrated network flow
management and exports a convenient programming interface that allows
applications to be notified of, and adapt to, changing network conditions. We
describe the API by which applications interface with the CM, and the
architectural considerations that factored into the design. To evaluate the
architecture and API, we describe our implementations of TCP; a streaming
layered audio/video application; and an interactive audio application using the
CM, and show that they achieve adaptive behavior without incurring much
end-system overhead. All flows including TCP benefit from the sharing of
congestion information, and applications are able to incorporate new
functionality such as congestion control and adaptive behavior.Comment: 14 pages, appeared in OSDI 200
HeteroSketch: coordinating network-wide monitoring in heterogeneous and dynamic networks
CNS-2107086 - National Science Foundation; CNS-2106946 - National Science FoundationPublished versio
Clearing the Rf Smog: Making 802.11 Robust to Cross-Technology Interference
Recent studies show that high-power cross-technology interference
is becoming a major problem in today’s 802.11 networks. Devices
like baby monitors and cordless phones can cause a wireless
LAN to lose connectivity. The existing approach for dealing
with such high-power interferers makes the 802.11 network switch
to a different channel; yet the ISM band is becoming increasingly
crowded with diverse technologies, and hence many 802.11 access
points may not find an interference-free channel.
This paper presents TIMO, a MIMO design that enables 802.11n
to communicate in the presence of high-power cross-technology
interference. Unlike existing MIMO designs, however, which require
all concurrent transmissions to belong to the same technology,
TIMO can exploit MIMO capabilities to decode in the presence
of a signal from a different technology, hence enabling diverse
technologies to share the same frequency band. We implement a
prototype of TIMO in GNURadio-USRP2 and show that it enables
802.11n to communicate in the presence of interference from baby
monitors, cordless phones, and microwave ovens, transforming scenarios
with a complete loss of connectivity to operational networks.National Science Foundation (U.S.) (NSF grant CNS-0831660)National Science Foundation (U.S.) (NSF grant CNS- 0721857)United States. Defense Advanced Research Projects Agency (DARPA ITMANET
Can User-Level Probing Detect and Diagnose Common Home-WLAN Pathologies?
Common 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 userlevel
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? In this paper, we present preliminary but
promising results indicating that such diagnostics are feasible
Analyzing the potential benefits of CDN augmentation strategies for internet video workloads
Video viewership over the Internet is rising rapidly, and market pre-dictions suggest that video will comprise over 90 % of Internet traf-fic in the next few years. At the same time, there have been signs that the Content Delivery Network (CDN) infrastructure is being stressed by ever-increasing amounts of video traffic. To meet these growing demands, the CDN infrastructure must be designed, pro-visioned and managed appropriately. Federated telco-CDNs and hybrid P2P-CDNs are two content delivery infrastructure designs that have gained significant industry attention recently. We ob-served several user access patterns that have important implica-tions to these two designs in our unique dataset consisting of 30 million video sessions spanning around two months of video view-ership from two large Internet video providers. These include par-tial interest in content, regional interests, temporal shift in peak load and patterns in evolution of interest. We analyze the impact of our findings on these two designs by performing a large scale measurement study. Surprisingly, we find significant amount of synchronous viewing behavior for Video On Demand (VOD) con-tent, which makes hybrid P2P-CDN approach feasible for VOD and suggest new strategies for CDNs to reduce their infrastructure costs. We also find that federation can significantly reduce telco-CDN provisioning costs by as much as 95%
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