7,437 research outputs found
Multiclass scheduling algorithms for the DAVID metro network
AbstractâThe data and voice integration over dense wavelength-division-multiplexing (DAVID) project proposes a metro network architecture based on several wavelength-division-multiplexing (WDM) rings interconnected via a bufferless optical switch called Hub. The Hub provides a programmable interconnection among rings on the basis of the outcome of a scheduling algorithm. Nodes connected to rings groom traffic from Internet protocol routers and Ethernet switches and share ring resources. In this paper, we address the problem of designing efficient centralized scheduling algorithms for supporting multiclass traffic services in the DAVID metro network. Two traffic classes are considered: a best-effort class, and a high-priority class with bandwidth guarantees. We define the multiclass scheduling problem at the Hub considering two different node architectures: a simpler one that relies on a complete separation between transmission and reception resources (i.e., WDM channels) and a more complex one in which nodes fully share transmission and reception channels using an erasure stage to drop received packets, thereby allowing wavelength reuse. We propose both optimum and heuristic solutions, and evaluate their performance by simulation, showing that heuristic solutions exhibit a behavior very close to the optimum solution. Index TermsâData and voice integration over dense wavelength-division multiplexing (DAVID), metropolitan area network, multiclass scheduling, optical ring, wavelength-division multiplexing (WDM). I
CMD: A Multi-Channel Coordination Scheme for Emergency Message Dissemination in IEEE 1609.4
In the IEEE 1609.4 legacy standard for multi-channel communications in
vehicular ad hoc networks(VANETs), the control channel (CCH) is dedicated to
broadcast safety messages while the service channels (SCH's) are dedicated to
transmit infotainment service content. However, the SCH can be used as an
alternative to transmit high priority safety messages in the event that they
are invoked during the service channel interval (SCHI). This implies that there
is a need to transmit safety messages across multiple available utilized
channels to ensure that all vehicles receive the safety message. Transmission
across multiple SCH's using the legacy IEEE 1609.4 requires multiple channel
switching and therefore introduces further end-to-end delays. Given that safety
messaging is a life critical application, it is important that optimal
end-to-end delay performance is derived in multi-channel VANET scenarios to
ensure reliable safety message dissemination. To tackle this challenge, three
primary contributions are in this article: first, a channel coordinator
selection approach based on the least average separation distance (LAD) to the
vehicles that expect to tune to other SCH's and operates during the control
channel interval (CCHI) is proposed. Second, a model to determine the optimal
time intervals in which CMD operates during the CCHI is proposed. Third, a
contention back-off mechanism for safety message transmission during the SCHI
is proposed. Computer simulations and mathematical analysis show that CMD
performs better than the legacy IEEE 1609.4 and a selected state-of-the-art
multi-channel message dissemination schemes in terms of end-to-end delay and
packet reception ratio.Comment: 15 pages, 10 figures, 7 table
Packet Transactions: High-level Programming for Line-Rate Switches
Many algorithms for congestion control, scheduling, network measurement,
active queue management, security, and load balancing require custom processing
of packets as they traverse the data plane of a network switch. To run at line
rate, these data-plane algorithms must be in hardware. With today's switch
hardware, algorithms cannot be changed, nor new algorithms installed, after a
switch has been built.
This paper shows how to program data-plane algorithms in a high-level
language and compile those programs into low-level microcode that can run on
emerging programmable line-rate switching chipsets. The key challenge is that
these algorithms create and modify algorithmic state. The key idea to achieve
line-rate programmability for stateful algorithms is the notion of a packet
transaction : a sequential code block that is atomic and isolated from other
such code blocks. We have developed this idea in Domino, a C-like imperative
language to express data-plane algorithms. We show with many examples that
Domino provides a convenient and natural way to express sophisticated
data-plane algorithms, and show that these algorithms can be run at line rate
with modest estimated die-area overhead.Comment: 16 page
Multi-Granular Optical Cross-Connect: Design, Analysis, and Demonstration
A fundamental issue in all-optical switching is to offer efficient and cost-effective transport services for a wide range of bandwidth granularities. This paper presents multi-granular optical cross-connect (MG-OXC) architectures that combine slow (ms regime) and fast (ns regime) switch elements, in order to support optical circuit switching (OCS), optical burst switching (OBS), and even optical packet switching (OPS). The MG-OXC architectures are designed to provide a cost-effective approach, while offering the flexibility and reconfigurability to deal with dynamic requirements of different applications. All proposed MG-OXC designs are analyzed and compared in terms of dimensionality, flexibility/reconfigurability, and scalability. Furthermore, node level simulations are conducted to evaluate the performance of MG-OXCs under different traffic regimes. Finally, the feasibility of the proposed architectures is demonstrated on an application-aware, multi-bit-rate (10 and 40 Gbps), end-to-end OBS testbed
High-Capacity Clos-Network Switch for Data Center Networks
Scaling-up Data Center Networks (DCNs) should be done at the network level as well as the switching elements level. The glaring reason for this, is that switches/routers deployed in the DCN can bound the network capacity and affect its performance if improperly chosen. Many multistage switching architectures have been proposed to fit for the next-generation networking needs. However all of them are either performance limited or too complex to be implemented. Targeting scalability and performance, we propose the design of a large-capacity switch in which we affiliate a multistage design with a Networks-on- Chip (NoC) design. The proposal falls into the category of buffered multistage switches. Still, it has a different architectural aspect and scheduling process. Dissimilar to common point-to-point crossbars, NoCs used at the heart of the three-stage Clos-network allow multiple packets simultaneously in the modules where they can be adaptively transported using a pipelined scheduling scheme. Our simulations show that the switch scales well with the load and size variation. It outperforms a variety of architectures under a range of traffic arrivals
Concave Switching in Single and Multihop Networks
Switched queueing networks model wireless networks, input queued switches and
numerous other networked communications systems. For single-hop networks, we
consider a {()-switch policy} which combines the MaxWeight policies
with bandwidth sharing networks -- a further well studied model of Internet
congestion. We prove the maximum stability property for this class of
randomized policies. Thus these policies have the same first order behavior as
the MaxWeight policies. However, for multihop networks some of these
generalized polices address a number of critical weakness of the
MaxWeight/BackPressure policies.
For multihop networks with fixed routing, we consider the Proportional
Scheduler (or (1,log)-policy). In this setting, the BackPressure policy is
maximum stable, but must maintain a queue for every route-destination, which
typically grows rapidly with a network's size. However, this proportionally
fair policy only needs to maintain a queue for each outgoing link, which is
typically bounded in number. As is common with Internet routing, by maintaining
per-link queueing each node only needs to know the next hop for each packet and
not its entire route. Further, in contrast to BackPressure, the Proportional
Scheduler does not compare downstream queue lengths to determine weights, only
local link information is required. This leads to greater potential for
decomposed implementations of the policy. Through a reduction argument and an
entropy argument, we demonstrate that, whilst maintaining substantially less
queueing overhead, the Proportional Scheduler achieves maximum throughput
stability.Comment: 28 page
- âŠ