To efficiently use alternate paths during periods of congestion, we have devised prioritized Dynamic Routing
Control Agent (pDRCA) that (1) selects best links to meet the bandwidth and delay requirements of traffic, (2)
provides load-balancing and traffic prioritization when multiple topologies are available, and (3) handles changes
in link quality and traffic demand, and link outages. pDRCA provides multiplatform load balancing to maximize
SATCOM (both P2P and multi-point) and airborne links utilization. It influences link selection by configuring the
cost metrics on a router's interface, which does not require any changes to the routing protocol itself. It supports
service differentiation of multiple traffic priorities by providing more network resources to the highest priority
flows. pDRCA does so by solving an optimization problem to find optimal links weights that increase throughput
and decrease E2E delay; avoid congested, low quality, and long delay links; and exploit path diversity in the network. These optimal link weights are sent to the local agents to be configured on individual routers per traffic priority. The pDRCA optimization algorithm has been proven effective in improving application performance. We created a variety of different test scenarios by varying traffic profile and link behavior (stable links, varying capacity, and link outages). In the scenarios where high priority traffic experienced significant loss without pDRCA, the average loss was reduced from 49.5% to 13% and in some cases dropped to 0%. Currently, pDRCA is integrated with an open-source software router and priority queues on Linux as a component of Open Tactical Router (OTR), which is being developed by ONR DTCN program.
Existing distributed approaches to topology control are poor at exploiting the large configuration space of cognitive
radios and use extensive inter-node synchronization to aim at optimality. We have created a framework to design and
study distributed topology control algorithms that combine network-formation games with machine learning. In our
approach, carefully designed incentive mechanisms drive distributed autonomous agents towards a pre-determined
system-wide optimum. The algorithms rely on game players to pursue selfish actions through low-complexity greedy
algorithms with low or no signaling overhead. Convergence and stability are ensured through proper mechanism design
that eliminates infinite adaptation process. The framework also includes game-theoretic extensions to influence behavior
such as fragment merging and preferring links to weakly connected neighbors. Learning allows adaptations that prevent
node starvation, reduce link flapping, and minimize routing disruptions by incorporating network layer feedback in
cost/utility tradeoffs. The algorithms are implemented in Telcordia Wireless IP Scalable Network Emulator. Using
greedy utility maximization as a benchmark, we show improvements of 13-40% for metrics such as the numbers of
disconnected fragments and weakly connected nodes, topology stability, and disruption to user flows. The proposed
framework is particularly suitable to cognitive radio networks because it can be extended to handle heterogeneous users
with different utility functions and conflicting objectives. Desired outcome is then achieved by application of standard
cooperation techniques such as utility transfer (payments). Additional cross-layer optimizations are possible by playing
games at multiple layers in a highly scalable manner.
WISER is a scalable network emulation tool for networks with several hundred heterogeneous wireless nodes. It
provides high-fidelity network modeling, exchanges packets in real-time, and faithfully captures the complex
interactions among network entities. WISER runs on inexpensive COTS platforms and represents multiple full network
stacks, one for each individual virtual node. It supports a flexible open source router platform (XORP) to implement
routing protocol stacks. WISER offers wireless MAC emulation capabilities for different types of links, waveforms,
radio devices, etc. We present experiments to demonstrate WISER's capabilities enabling a new paradigm for
performance evaluation of mobile sensor and ad-hoc networks.
The communication of Future Combat Systems (FCS), with rigid timing and reliability requirements, has posed
a great challenge for the existing popular transport layer protocols such as TCP and UDP. The Stream Control
Transmission Protocol (SCTP), first designed to transmit telephony signaling messages over Internet, is a promising
transport layer candidate for FCS networks. The new SCTP features such as multi-homing, multi-streaming,
and enhanced security can significantly improve the performance of FCS applications. In this paper, we propose
modifications to the congestion control and multi-streaming parts of current SCTP specifications to allow the
support of QoS for FCS applications. Multiple streams in an SCTP association provide an aggregation mechanism
to accommodate heterogeneous objects, which belong to the same application but may require different
types of QoS from the network. However, the current SCTP specification lacks an internal mechanism to support
the preferential treatment among its streams. Our work introduces the concept of grouping SCTP streams into
subflows based on their required QoS. We propose to modify the current SCTP to implement subflows (named
SF-SCTP), each with its own flow and congestion mechanism to prevent the so-called false sharing problem.
To improve the fairness of SF-SCTP towards the original SCTP, we integrate Fractional Congestion Control
into the design. The throughput performance evaluation of SF-SCTP is studied through ns-2 experiments in a
simplified Diff-Serv network. The simulation results prove the SF-SCTP's capability to support QoS among its
streams, confirm the accuracy of the analytic models, and justify our effects to integrate FCC into SF-SCTP
since it improves the fairness between SF-SCTP and the original SCTP.
In this paper we propose a new routing protocol called the Directional Flow Routing (DFR) which takes advantages of directional antenna technology envisioned in near future for ad hoc networks. DFR is a source routing protocol where the route is completely specified by a Directional Flow Vector (DFV) between the source and the destination. DFV is a time varying straight function joining the source and the destination and is computed using the relative velocity and position vectors between the two. A packet is delivered at the destination by aligning the directional antennas of nodes along the flow vector such that packets flow along the instantaneous line joining the source and the sink. DFR is a stateless source routing protocol which has the potential to efficiently handle large scale and dense ad hoc networks with very high mobility rates. The paper presents the conceptual framework for the DFR routing paradigm. Although we also propose a simple protocol for practical implementation of the concept, we do not intend to analyze the performance of the protocol in this paper. Rather, the focus of this paper lies in discussing the design choices that would be necessary for the protocol implementation. It is also intended to highlight the issues and practical challenges involved in designing algorithms using directional antennas in general and should serve as guidelines for future research.
The Stream Control Transmission Protocol (SCTP), a general-purpose
transport layer protocol standardized by the IETF, has been a promising
candidate to join UDP and TCP as a core protocol. The new SCTP features
such as multi-homing, multi-streaming, and enhanced security can
significantly improve the performance of FCS applications.
Multi-streaming provides an aggregation mechanism in an SCTP association
to accommodate heterogeneous objects, which belong to the same
application but may require different type of QoS from the network.
However, the current SCTP specification lacks an internal mechanism to
support the preferential treatment among its streams. We introduce the
concept of subflow and propose to modify the current SCTP such that the
streams are grouped into several subflows according to their required
QoS. It is also proposed that each subflow should implement its own
congestion control to prevent the so-called false sharing. To
compare the throughput differences, analytic models have been derived
for the current SCTP and for the subflow-capable SCTP with different
congestion control mechanisms. Simulations with ns-2 have been used to
qualitatively demonstrate the throughput differences of these
designs in a simplified diff-serv network. The analytical models are
confirmed to accurately reflect the SCTP behavior. The simulation also
shows that our proposed solution is able to efficiently support QoS
among the SCTP streams.
We present Dynamic Survivable Resource Pooling (DSRP) that provides
survivable access to resources and services in battlefield networks. The
servers accessed by mobile users (e.g., FCS backbone managers, TPKI,
Bandwidth Brokers, Situation Awareness/Common Network Picture, SIP) are pooled together for higher availability and failover; the Name
Servers (NSs) are responsible for maintaining server pools, load balancing, and server discovery. In the DSRP scheme, NSs are placed on a virtual
backbone (VB): a highly distributed, scalable, and survivable network
formed and maintained through one-hop beacons. By making locally scoped
decisions, VB is capable of reorganizing both itself and pool registrations
in response to mobility, failures, and partitioning. A proof-of-concept of
the DSRP successfully demonstrated its survivability.
We present a scalable architecture for assuring Quality of Service to VoIP applications in an Internet Service Provider's network. This architecture is based on the Differentiated Services and Bandwidth Broker models, and can also be used by other resource-sensitive applications. In this paper, we elaborate on a number of significant issues involved in the design, implementation, deployment and use of the Bandwidth Broker. The Call Agent architecture is used as the VoIP application. We describe the Bandwidth Broker prototype that is used to validate our approach. Our findings suggest that it is feasible to use the Bandwidth Broker architecture for assuring QoS, and a trade-off exists between the granularity of resource requests and call-setup delay.