4,718 research outputs found
An Optimal Lower Bound for Buffer Management in Multi-Queue Switches
In the online packet buffering problem (also known as the unweighted FIFO
variant of buffer management), we focus on a single network packet switching
device with several input ports and one output port. This device forwards
unit-size, unit-value packets from input ports to the output port. Buffers
attached to input ports may accumulate incoming packets for later transmission;
if they cannot accommodate all incoming packets, their excess is lost. A packet
buffering algorithm has to choose from which buffers to transmit packets in
order to minimize the number of lost packets and thus maximize the throughput.
We present a tight lower bound of e/(e-1) ~ 1.582 on the competitive ratio of
the throughput maximization, which holds even for fractional or randomized
algorithms. This improves the previously best known lower bound of 1.4659 and
matches the performance of the algorithm Random Schedule. Our result
contradicts the claimed performance of the algorithm Random Permutation; we
point out a flaw in its original analysis
Buffer Overflow Management with Class Segregation
We consider a new model for buffer management of network switches with
Quality of Service (QoS) requirements. A stream of packets, each attributed
with a value representing its Class of Service (CoS), arrives over time at a
network switch and demands a further transmission. The switch is equipped with
multiple queues of limited capacities, where each queue stores packets of one
value only. The objective is to maximize the total value of the transmitted
packets (i.e., the weighted throughput).
We analyze a natural greedy algorithm, GREEDY, which sends in each time step
a packet with the greatest value. For general packet values , we show that GREEDY is -competitive, where . Furthermore, we show a lower bound of on the competitiveness of any deterministic online algorithm.
In the special case of two packet values (1 and ), GREEDY is shown
to be optimal with a competitive ratio of
Scheduling Packets with Values and Deadlines in Size-bounded Buffers
Motivated by providing quality-of-service differentiated services in the
Internet, we consider buffer management algorithms for network switches. We
study a multi-buffer model. A network switch consists of multiple size-bounded
buffers such that at any time, the number of packets residing in each
individual buffer cannot exceed its capacity. Packets arrive at the network
switch over time; they have values, deadlines, and designated buffers. In each
time step, at most one pending packet is allowed to be sent and this packet can
be from any buffer. The objective is to maximize the total value of the packets
sent by their respective deadlines. A 9.82-competitive online algorithm has
been provided for this model (Azar and Levy. SWAT 2006), but no offline
algorithms have been known yet. In this paper, We study the offline setting of
the multi-buffer model. Our contributions include a few optimal offline
algorithms for some variants of the model. Each variant has its unique and
interesting algorithmic feature. These offline algorithms help us understand
the model better in designing online algorithms.Comment: 7 page
Stable Wireless Network Control Under Service Constraints
We consider the design of wireless queueing network control policies with
particular focus on combining stability with additional application-dependent
requirements. Thereby, we consequently pursue a cost function based approach
that provides the flexibility to incorporate constraints and requirements of
particular services or applications. As typical examples of such requirements,
we consider the reduction of buffer underflows in case of streaming traffic,
and energy efficiency in networks of battery powered nodes. Compared to the
classical throughput optimal control problem, such requirements significantly
complicate the control problem. We provide easily verifyable theoretical
conditions for stability, and, additionally, compare various candidate cost
functions applied to wireless networks with streaming media traffic. Moreover,
we demonstrate how the framework can be applied to the problem of energy
efficient routing, and we demonstrate the aplication of our framework in
cross-layer control problems for wireless multihop networks, using an advanced
power control scheme for interference mitigation, based on successive convex
approximation. In all scenarios, the performance of our control framework is
evaluated using extensive numerical simulations.Comment: Accepted for publication in IEEE Transactions on Control of Network
Systems. arXiv admin note: text overlap with arXiv:1208.297
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