4,118 research outputs found
Advanced Message Routing for Scalable Distributed Simulations
The Joint Forces Command (JFCOM) Experimentation Directorate (J9)'s recent Joint Urban Operations (JUO)
experiments have demonstrated the viability of Forces Modeling and Simulation in a distributed environment. The
JSAF application suite, combined with the RTI-s communications system, provides the ability to run distributed
simulations with sites located across the United States, from Norfolk, Virginia to Maui, Hawaii. Interest-aware
routers are essential for communications in the large, distributed environments, and the current RTI-s framework
provides such routers connected in a straightforward tree topology. This approach is successful for small to medium
sized simulations, but faces a number of significant limitations for very large simulations over high-latency, wide
area networks. In particular, traffic is forced through a single site, drastically increasing distances messages must
travel to sites not near the top of the tree. Aggregate bandwidth is limited to the bandwidth of the site hosting the
top router, and failures in the upper levels of the router tree can result in widespread communications losses
throughout the system.
To resolve these issues, this work extends the RTI-s software router infrastructure to accommodate more
sophisticated, general router topologies, including both the existing tree framework and a new generalization of the
fully connected mesh topologies used in the SF Express ModSAF simulations of 100K fully interacting vehicles.
The new software router objects incorporate the scalable features of the SF Express design, while optionally using
low-level RTI-s objects to perform actual site-to-site communications. The (substantial) limitations of the original
mesh router formalism have been eliminated, allowing fully dynamic operations. The mesh topology capabilities
allow aggregate bandwidth and site-to-site latencies to match actual network performance. The heavy resource load at
the root node can now be distributed across routers at the participating sites
Exploiting AWG Free Spectral Range Periodicity in Distributed Multicast Architectures
Modular optical switch architectures combining wavelength routing based on
arrayed waveguide grating (AWG) devices and multicasting based on star couplers
hold promise for flexibly addressing the exponentially growing traffic demands
in a cost- and power-efficient fashion. In a default switching scenario, an
input port of the AWG is connected to an output port via a single wavelength.
This can severely limit the capacity between broadcast domains, resulting in
interdomain traffic switching bottlenecks. In this paper, we examine the
possibility of resolving capacity bottlenecks by exploiting multiple AWG free
spectral ranges (FSRs), i.e., setting up multiple parallel connections between
each pair of broadcast domains. To this end, we introduce a multi-FSR
scheduling algorithm for interconnecting broadcast domains by fairly
distributing the wavelength resources among them. We develop a general-purpose
analytical framework to study the blocking probabilities in a multistage
switching scenario and compare our results with Monte Carlo simulations. Our
study points to significant improvements with a moderate increase in the number
of FSRs. We show that an FSR count beyond four results in diminishing returns.
Furthermore, to investigate the trade-offs between the network- and
physical-layer effects, we conduct a cross-layer analysis, taking into account
pulse amplitude modulation (PAM) and rate-adaptive forward error correction
(FEC). We illustrate how the effective bit rate per port increases with an
increase in the number of FSRs. %We also look at the advantages of an
impairment-aware scheduling strategy in a multi-FSR switching scenario
Efficient Micro-Mobility using Intra-domain Multicast-based Mechanisms (M&M)
One of the most important metrics in the design of IP mobility protocols is
the handover performance. The current Mobile IP (MIP) standard has been shown
to exhibit poor handover performance. Most other work attempts to modify MIP to
slightly improve its efficiency, while others propose complex techniques to
replace MIP. Rather than taking these approaches, we instead propose a new
architecture for providing efficient and smooth handover, while being able to
co-exist and inter-operate with other technologies. Specifically, we propose an
intra-domain multicast-based mobility architecture, where a visiting mobile is
assigned a multicast address to use while moving within a domain. Efficient
handover is achieved using standard multicast join/prune mechanisms. Two
approaches are proposed and contrasted. The first introduces the concept
proxy-based mobility, while the other uses algorithmic mapping to obtain the
multicast address of visiting mobiles. We show that the algorithmic mapping
approach has several advantages over the proxy approach, and provide mechanisms
to support it. Network simulation (using NS-2) is used to evaluate our scheme
and compare it to other routing-based micro-mobility schemes - CIP and HAWAII.
The proactive handover results show that both M&M and CIP shows low handoff
delay and packet reordering depth as compared to HAWAII. The reason for M&M's
comparable performance with CIP is that both use bi-cast in proactive handover.
The M&M, however, handles multiple border routers in a domain, where CIP fails.
We also provide a handover algorithm leveraging the proactive path setup
capability of M&M, which is expected to outperform CIP in case of reactive
handover.Comment: 12 pages, 11 figure
Scalability of broadcast performance in wireless network-on-chip
Networks-on-Chip (NoCs) are currently the paradigm of choice to interconnect the cores of a chip multiprocessor. However, conventional NoCs may not suffice to fulfill the on-chip communication requirements of processors with hundreds or thousands of cores. The main reason is that the performance of such networks drops as the number of cores grows, especially in the presence of multicast and broadcast traffic. This not only limits the scalability of current multiprocessor architectures, but also sets a performance wall that prevents the development of architectures that generate moderate-to-high levels of multicast. In this paper, a Wireless Network-on-Chip (WNoC) where all cores share a single broadband channel is presented. Such design is conceived to provide low latency and ordered delivery for multicast/broadcast traffic, in an attempt to complement a wireline NoC that will transport the rest of communication flows. To assess the feasibility of this approach, the network performance of WNoC is analyzed as a function of the system size and the channel capacity, and then compared to that of wireline NoCs with embedded multicast support. Based on this evaluation, preliminary results on the potential performance of the proposed hybrid scheme are provided, together with guidelines for the design of MAC protocols for WNoC.Peer ReviewedPostprint (published version
Multi-layer virtual transport network management
Nowadays there is an increasing need for a general paradigm which can simplify network management and further enable network innovations. Software Defined Networking (SDN) is an efficient way to make the network programmable and reduce management complexity, however it is plagued with limitations inherited from the legacy Internet (TCP/IP) architecture. In this paper, in response to limitations of current Software Defined Networking (SDN) management solutions, we propose a recursive approach to enterprise network management, where network management is done through managing various Virtual Transport Networks (VTNs) over different scopes (i.e., regions of operation). Different from the traditional virtual network model which mainly focuses on routing/tunneling, our VTN provides communication service with explicit Quality-of-Service (QoS) support for applications via transport flows, and it involves all mechanisms (e.g., addressing, routing, error and flow control, resource allocation) needed to support such transport flows. Based on this approach, we design and implement a management architecture, which recurses the same VTN-based management mechanism for enterprise network management. Our experimental results show that our management architecture achieves better performance.National Science Foundation awards: CNS-0963974 and CNS-1346688
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