Backbones infrastructures in wireless sensor networks reduce the communication overhead and energy consumption. In this paper, we present BackBone Routing (BBR), a fully distributed protocol for construction and rotation of backbone networks. BBR reduces energy consumption without significantly diminishing the capacity or connectivity of the network. Another key feature of BBR is its energy balancing nature by distributing the role of being Backbone Node among all the nodes. BBR builds on the observation that when a region of a shared-channel wireless network has a sufficient density of nodes, only a small number of them need be on at any time to forward traffic for active connections. Improvement in system lifetime due to BBR increases as the ratio of idle-to-sleep energy consumption increases, and increases as the density of the network increases. Our experiments show that BBR is more efficient in saving energy and extending network life without deteriorating network performance when compared with geographical shortest path routing.
Optical networking, with its almost unlimited bandwidth, is the only technology that can support communication new applications with high demand for bandwidth such as remote visualization, teleimmersion, collaborative e-science etc. In the optical networks presently deployed, each link is optically isolated by transponders doing O/E/O conversions. But these transponders are quite expensive and lack transparency; hence there is a strong motivation to use large all-optical networks. In all-optical networks, all routes need not have adequate signal quality. To provide reliable and transparent service, there is a strong interest in the industry for routing protocols that take into consideration the impairments of optical layer that degrade quality of the signal. We present a new routing protocol that uses information about the quality of signal to select paths in an all-optical network. Our simulations confirm that this new protocol reaches higher network utilization compared to existing ones.
An new optical correlator containing a tapped delay line with thousands of taps is described. This enables ultra-high resolution correlation. We apply this to monitoring quality-of-signal by correlating the received, degraded bits with and un-degraded signal. The strength of the correlation signal, which is all optical, is proportional to the quality. Dispersion and attenuation can be evaluated in less than 100 ps at 40Gb/s, and jitter and noise in less than 100 ns. This is a significant improvement over minutes or even hours for bit-error-rate measurements. Simulations show good correspondence to eye-diagram measurements, the conventional (but slow) way to measure signal quality. If a network node can know the quality of all its links in real-time, it can re-route signals around poor links, and provide restoration and protection as well. The key to all this is an optical correlator with a very large number of taps in its internal tapped delay line. Our device uses a White cell and a fixed micro-mirror array. In a White cell, light bounces back and forth between three spherical mirrors. Multiple beams circulate in the same cell without interfering and are each refocused to a unique pattern of spots. We make the spots land on the micro-mirror array to switch between cells of slightly different lengths. Our current design provides 6550 possible delays for thousands of light beams, using only ten mirrors, a lens, and the micro-mirror array. We have developed two routing and protection protocols to exploit having this real-time information available to the network.
Broadband satellite constellation networks will be required to carry all types of IP traffic, real time interactive traffic as well as nonreal time traffic, warranting the need for appropriate QoS for these different traffic flows. In this paper we investigate advantages of employing constraint-based routing using MPLS in a multilayered hierarchical satellite constellation. Bandwidth availability or residual bandwidth on a satellite link is taken into account when setting up routes for high priority real-time traffic e.g. VoIP, which is sensitive to delay and jitter. Also to protect the VoIP traffic from being swamped by bursty best-effort traffic we propose to have a separate queue for high priority traffic. The performance of the prioritized load balancing routing algorithm on a multi-layered satellite network is simulated and analyzed.
Congestion in the Internet results in wasted bandwidth and also stands in the way of guaranteeing QoS. The effect of congestion is multiplied many fold in Satellite networks, where the resources are very expensive. Thus congestion control has a special significance in the performance of Satellite networks. In today's Internet, congestion control is implemented mostly using some form of the de facto standard, RED. But tuning of parameters in RED has been a major problem throughout. Achieving high throughput with corresponding low delays is the main goal in parameter setting. It is also desired to keep the oscillations in the queue low to reduce jitter, so that the QoS guarantees can be improved. In this paper, we use a previously linearized fluid flow model of TCP-RED to study the performance and stability of the Queue in the router. We use classical control tools like Tracking Error minimization and Delay Margin to study the performance, stability of the system. We use the above-mentioned tools to provide guidelines for setting the parameters in RED, such that the throughput, delay and jitter of the system are optimized. Thus we provide guidelines for optimizing satellite IP networks. We apply our results exclusively for optimizing the performance of satellite networks, where the effects of congestion are much pronounced and need for optimization is much important. We use ns simulator to validate our results to support our analysis.
Due to the increasing demand for mobility among the Internet users, there is a urgent requirement to identify and solve the deficiencies in the wireless domain. One such urgent problem is the poor performance of TCP over wireless links. TCP still being the only protocol used in the Internet for reliable transfers, the assumptions made by TCP in the wired domain are not valid in the wireless domain. To enhance the performace of the TCP in the wireless domain, we need to differentiate the 'congestion loss' from the 'wireless loss'. We find that the previous attempts in this direction make unjustified demands from the network or the accuracy of the schemes are inadequate. We are convinced that reliable transport is a end-to-end semantic and other networkcomp onents should not be burdened with this work. In this paper we propose a scheme called the 'Source-Centric Congestion Filtering', based on the MECN protocol, which tries to differentiate the losses based on the networkfeedback.
Our simulations using the NS-2 simulator shows that our protocol has very less percentage of error and performs better than most of the other end-to-end TCP variants.
Congestion avoidance on today's Internet is mainly provided by the combination of the TCP
protocol and Active Queue Management (AQM) schemes such as the de facto
standard RED (Random Early Detection). When used with ECN (Explicit Congestion Notification),
these algorithms can be modeled as a feedback control system in which the feedback information
is carried on a single bit. A modification of this scheme called MECN was proposed,
where the marking information
is carried using 2 bits. MECN conveys more accurate feedback about the network congestion to
the source than the current 1-bit ECN. The TCP source reaction was modified so that it
takes advantage of the extra information about congestion and adapts faster to the changing congestion
scenario leading to a smoother decrease in the sending rates of the sources upon congestion detection and
consequently resulting in an increase in the router's throughput. A linearized fluid flow model
already developed for ECN is extended to our case. Using control theoretic tools
we justify the performance obtained in using the MECN scheme and give guidelines for
optimizing its parameters. We use ns simulations to illustrate
the performance improvement from the point of better throughput and low level of oscillations in the queue.
This paper proposes a new method of bandwidth allocation during congestion, called the proportional allocation of bandwidth. Traditionally, max-min fairness has been proposed to allocate bandwidth under congestion. Our allocation scheme considers the situation where flows might have different subscribed information rates, based on their origin. In proportional allocation of bandwidth, during congestion all flows get a share of available bandwidth, which is in proportion to their subscribed information rate. We suggest a method for implementing this with minimum signaling and without storing per-flow state. Our method is based on the principles of differentiated services - diffserv. We show by simulation that it is possible to obtain proportional bandwidth allocation without per-flow state storing and minimum signaling.
Due to the fundamental satellite system characteristics such as global coverage, broadcast nature, and bandwidth on demand, satellite systems are excellent candidates for providing high data rate Internet access and global connectivity accommodating the a wide variety of applications. Provisioning of quality of service (QoS) within the advanced satellite system is the critical requirement. Congestion remains the main obstacle to Quality of Service (QoS) on the Internet. Explicit Congestion Notification (ECN) is the only mechanism that delivers explicit congestion signals to the source. So improving the ECN feedback is essential for the future data and satellite networks and their QoS guarantees. In this paper we present a new traffic management scheme based on an enhanced ECN mechanism. In particular we used the mark-front strategy instead of the mark-tail one in ECN. The main advantage of mark-front strategy is that it sends faster feedback information about the congestion and consequently enables faster reaction from the source. Our analysis and simulation results show that the mark-front strategy of ECN provides better link-efficiency, fairness among users, lesser buffer requirements and much less losses than the mark-tail strategy.