6,504 research outputs found
Optimal LQG Control Across a Packet-Dropping Link
We examine optimal Linear Quadratic Gaussian control for a system in which communication between the sensor (output of the plant) and the controller occurs across a packet-dropping link. We extend the familiar LQG separation principle to this problem that allows us to solve this problem using a standard LQR state-feedback design, along with an optimal algorithm for propagating and using the information across the unreliable link. We present one such optimal algorithm, which consists of a Kalman Filter at the sensor side of the link, and a switched linear filter at the controller side. Our design does not assume any statistical model of the packet drop events, and is thus optimal for an arbitrary packet drop pattern. Further, the solution is appealing from a practical point of view because it can be implemented as a small modification of an existing LQG control design
Phase transition and hysteresis in scale-free network traffic
We model information traffic on scale-free networks by introducing the node
queue length L proportional to the node degree and its delivering ability C
proportional to L. The simulation gives the overall capacity of the traffic
system, which is quantified by a phase transition from free flow to congestion.
It is found that the maximal capacity of the system results from the case of
the local routing coefficient \phi slightly larger than zero, and we provide an
analysis for the optimal value of \phi. In addition, we report for the first
time the fundamental diagram of flow against density, in which hysteresis is
found, and thus we can classify the traffic flow with four states: free flow,
saturated flow, bistable, and jammed.Comment: 5 pages, 4 figure
FAIR: Forwarding Accountability for Internet Reputability
This paper presents FAIR, a forwarding accountability mechanism that
incentivizes ISPs to apply stricter security policies to their customers. The
Autonomous System (AS) of the receiver specifies a traffic profile that the
sender AS must adhere to. Transit ASes on the path mark packets. In case of
traffic profile violations, the marked packets are used as a proof of
misbehavior.
FAIR introduces low bandwidth overhead and requires no per-packet and no
per-flow state for forwarding. We describe integration with IP and demonstrate
a software switch running on commodity hardware that can switch packets at a
line rate of 120 Gbps, and can forward 140M minimum-sized packets per second,
limited by the hardware I/O subsystem.
Moreover, this paper proposes a "suspicious bit" for packet headers - an
application that builds on top of FAIR's proofs of misbehavior and flags
packets to warn other entities in the network.Comment: 16 pages, 12 figure
- …