IEEE Final Year Projects 2011-2012 :: Elysium Technologies Pvt Ltd::Networknew

Elysium Technologies Private Limited
ISO 9001:2008 A leading Research and Development Division
Madurai | Chennai | Trichy | Coimbatore | Kollam| Singapore
Website: elysiumtechnologies.com, elysiumtechnologies.info
Email: info@elysiumtechnologies.com

IEEE Final Year Project List 2011-2012

Abstract NETWORK 2011 - 2012

01 A Novel Approach for Failure Localization in All-Optical Mesh Networks

Achieving fast and precise failure localization has long been a highly desired feature in all-optical mesh networks.
Monitoring trail (m-trail) has been proposed as the most general monitoring structure for achieving unambiguous failure
localization (UFL) of any single link failure while effectively reducing the amount of alarm signals flooding the networks.
However, it is critical to come up with a fast and intelligent m-trail design approach for minimizing the number of m-trails
and the total bandwidth consumed, which ubiquitously determines the length of the alarm code and bandwidth overhead
for the m-trail deployment, respectively. In this paper, the m-trail design problem is investigated. To gain a deeper
understanding of the problem, we first conduct a bound analysis on the minimum length of alarm code of each link required
for UFL on the most sparse (i.e., ring) and dense (i.e., fully meshed) topologies. Then, a novel algorithm based on random
code assignment (RCA) and random code swapping (RCS) is developed for solving the m-trail design problem. The
algorithm is verified by comparison to an integer linear program (ILP) approach, and the results demonstrate its superiority
in minimizing the fault management cost and bandwidth consumption while achieving significant reduction in computation
time. To investigate the impact of topology diversity, extensive simulation is conducted on thousands of random network
topologies with systematically increased network density.

02 A Simple Model for Chunk-Scheduling Strategies in P2P Streaming

Peer-to-peer (P2P) streaming tries to achieve scalability (like P2P file distribution) and at the same time meet real-time
playback requirements. It is a challenging problem still not well understood. In this paper, we describe a simple stochastic
model that can be used to compare different downloading strategies to random peer selection. Based on this model, we
study the tradeoffs between supported peer population, buffer size, and playback continuity. We first study two simple
strategies: Rarest First (RF) and Greedy. The former is a well-known strategy for P2P file sharing that gives good scalability
by trying to propagate the chunks of a file to as many peers as quickly as possible. The latter is an intuitively reasonable
strategy to get urgent chunks first to maximize playback continuity from a peer’s local perspective. Yet in reality, both
scalability and urgency should be taken care of. With this insight, we propose a Mixed strategy that achieves the best of
both worlds. Furthermore, the Mixed strategy comes with an adaptive algorithm that can adapt its buffer setting to dynamic
peer population. We validate our analytical model with simulation. Finally, we also discuss the modeling assumptions and
the model’s sensitivity to different parameters and show that our model is robust.

03 A Unified Approach to Optimizing Performance in Networks Serving Heterogeneous Flows

We study the optimal control of communication networks in the presence of heterogeneous traffic requirements.
Specifically, we distinguish the flows into two crucial classes: inelastic for modeling high-priority, delay-sensitive, and
fixed-throughput applications; and elastic for modeling low-priority, delay-tolerant, and throughput-greedy applications.We
note that the coexistence of such diverse flows creates complex interactions at multiple levels (e.g., flow and packet levels),
which prevent the use of earlier design approaches that dominantly assume homogeneous traffic. In this work, we develop
the mathematical framework and novel design methodologies needed to support such heterogeneous requirements and
propose provably optimal network algorithms that account for the multilevel interactions between the flows. To that end, we
first formulate a network optimization problem that incorporates the above throughput and service prioritization
requirements of the two traffic types. We, then develop a distributed joint load-balancing and congestion control algorithm

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that achieves the dual goal of maximizing the aggregate utility gained by the elastic flows while satisfying the fixed
throughput and prioritization requirements of the inelastic flows. Next, we extend our joint algorithm in two ways to further
improve its performance: in delay through a virtual queue implementation with minimal throughput degradation and in
utilization by allowing for dynamic multipath routing for elastic flows. A unique characteristic of our proposed dynamic
routing solution is the novel two-stage queueing architecture it introduces to satisfy the service prioritization requirement.

04 Adjacent Link Failure Localization With Monitoring Trails in All-Optical Mesh Networks

Being reported as the most general monitoring structure for out-of-band failure localization approach, the monitoring trail
(m-trail) framework has been witnessed with great efficiency and promises to serve in the future Internet backbone with all-
optical mesh wavelength division multiplex (WDM) networks. Motivated by its potential and significance, this paper
investigates failure localization in all-optical mesh networks using m-trails. By considering shared risk link groups (SRLGs)
with up to all adjacent links of any node in the network, a novel algorithm of m-trail allocation for achieving unambiguous
failure localization (UFL) of any single SRLG failure is developed. The proposed algorithm aims to minimize the number of
required m-trails and can achieve superb performance with respect to the computation efficiency. We claim that among all
the previously reported counterparts, this paper has considered one of the most applicable scenarios to the design of
network backbone, and the proposed method can be easily extended to the case of node failure localization. Extensive
simulation is conducted to verify the proposed algorithm in comparison to its existing

05 An Adaptive Network Coded Retransmission Scheme for Single-HopWireless Multicast Broadcast Services

Network coding has recently attracted attention as a substantial improvement to packet retransmission schemes in
wireless multicast broadcast services (MBS). Since the problem of finding the optimal network code maximizing the
bandwidth efficiency is hard to solve and hard to approximate, two main network coding heuristic schemes, namely
opportunistic and full network coding, were suggested in the literature to improve the MBS bandwidth efficiency. However,
each of these two schemes usually outperforms the other in different receiver, demand, and feedback settings. The
continuous and rapid change of these settings in wireless networks limits the bandwidth efficiency gains if only one
scheme is always employed. In this paper, we propose an adaptive scheme that maintains the highest bandwidth efficiency
obtainable by both opportunistic and full network coding schemes in wireless MBS. The proposed scheme adaptively
selects, between these two schemes, the one that is expected to achieve the better bandwidth efficiency performance. The
core contribution in this adaptive selection scheme lies in our derivation of performance metrics for opportunistic network
coding, using random graph theory, which achieves efficient selection when compared to appropriate full network coding
parameters. To compare between different complexity levels, we present three approaches to compute the performance
metric for opportunistic coding using different levels of knowledge about the opportunistic coding graph. For the three
considered approaches, simulation results show that our proposed scheme almost achieves the bandwidth efficiency
performance that could be obtained by the optimal selection between the opportunistic and full coding schemes.

06 An Optimal Algorithm for Relay Node Assignment in Cooperative Ad Hoc Networks

Recently, cooperative communications, in the form of having each node equipped with a single antenna and exploit spatial
diversity via some relay node’s antenna, is shown to be a promising approach to increase data rates in wireless networks.
Under this communication paradigm, the choice of a relay node (among a set of available relay nodes) is critical in the
overall network performance. In this paper, we study the relay node assignment problem in a cooperative ad hoc network
environment, where multiple source–destination pairs compete for the same pool of relay nodes in the network. Our


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objective is to assign the available relay nodes to different source–destination pairs so as to maximize the minimum data
rate among all pairs. The main contribution of this paper is the development of an optimal polynomial time algorithm, called
ORA, that achieves this objective. A novel idea in this algorithm is a “linear marking” mechanism, which maintains linear
complexity of each iteration. We give a formal proof of optimality for ORA and use numerical results to demonstrate its
capability.

07 Approaching Throughput-Optimality in Distributed CSMA Scheduling Algorithms With Collisions

It was shown recently that carrier sense multiple access (CSMA)-like distributed algorithms can achieve the maximal
throughput in wireless networks (and task processing networks) under certain assumptions. One important but idealized
assumption is that the sensing time is negligible, so that there is no collision. In this paper, we study more practical CSMA-
based scheduling algorithms with collisions. First, we provide a Markov chain model and give an explicit throughput
formula that takes into account the cost of collisions and overhead. The formula has a simple form since the Markov chain
is “almost” time-reversible. Second, we propose transmission-length control algorithms to approach throughput-optimality
in this case. Sufficient conditions are given to ensure the convergence and stability of the proposed algorithms. Finally, we
characterize the relationship between the CSMA parameters (such as the maximum packet lengths) and the achievable
capacity region.

08 Architecture and Abstractions for Environment and Traffic-Aware System-Level Coordination of Wireless Networks

This paper presents a system-level approach to interference management in an infrastructure-based wireless network with
full frequency reuse. The key idea is to use loose base-station coordination that is tailored to the spatial load distribution
and the propagation environment to exploit the diversity in a user population’s sensitivity to interference. System
architecture and abstractions to enable such coordination are developed for both the downlink and the uplink cases, which
present differing interference characteristics. The basis for the approach is clustering and aggregation of traffic loads into
classes of users with similar interference sensitivities that enable coarse-grained information exchange among base
stations with greatly reduced communication overheads. This paper explores ways to model and optimize the system under
dynamic traffic loads where users come and go, resulting in interference-induced performance coupling across base
stations. Based on extensive system-level simulations, we demonstrate load-dependent reductions in file transfer delay
ranging from 20%–80% as compared to a simple baseline not unlike systems used in the field today while simultaneously
providing more uniform coverage. Average savings in user power consumption of up to 75% is achieved. Performance
results under heterogeneous spatial loads illustrate the importance of being traffic- and environment-aware..

09 BRICK: A Novel Exact Active Statistics Counter Architecture

In this paper, we present an exact active statistics counter architecture called Bucketized Rank Indexed Counters (BRICK)
that can efficiently store per-flow variable-width statistics counters entirely in SRAM while supporting both fast updates and
lookups (e.g., 40-Gb/s line rates). BRICK exploits statistical multiplexing by randomly bundling counters into small fixed-
size buckets and supports dynamic sizing of counters by employing an innovative indexing scheme called rank indexing.
Experiments with Internet traces show that our solution can indeed maintain large arrays of exact active statistics counters
with moderate amounts of SRAM.


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10 Buffer Sizing for 802.11-Based Networks

We consider the sizing of network buffers in IEEE 802.11-based networks.Wireless networks face a number of fundamental
issues that do not arise in wired networks.We demonstrate that the use of fixed-size buffers in 802.11 networks inevitably
leads to either undesirable channel underutilization or unnecessary high delays. We present two novel dynamic buffer-
sizing algorithms that achieve high throughput while maintaining low delay across a wide range of network conditions.
Experimental measurements demonstrate the utility of the proposed algorithms in a production WLAN and a lab test bed.

11 Capacity of Large-Scale CSMA Wireless Networks

In the literature, asymptotic studies of multihop wireless network capacity often consider only centralized and deterministic
time-division multiple-access (TDMA) coordination schemes. There have been fewer studies of the asymptotic capacity of
large-scale wireless networks based on carrier-sensing multiple access (CSMA), which schedules transmissions in a
distributed and random manner. With the rapid and widespread adoption of CSMA technology, a critical question is whether
CSMA networks can be as scalable as TDMA networks. To answer this question and explore the capacity of CSMA
networks, we first formulate the models of CSMA protocols to take into account the unique CSMA characteristics not
captured by existing interference models in the literature. These CSMA models determine the feasible states, and
consequently the capacity of CSMA networks. We then study the throughput efficiency of CSMA scheduling as compared to
TDMA. Finally, we tune the CSMA parameters so as to maximize the throughput to the optimal order. As a result, we show
that CSMA can achieve throughput as ohm(1/root(n)), the same order as optimal centralized TDMA, on uniform random
networks. Our CSMA scheme makes use of an efficient backbone–peripheral routing scheme and a careful design of dual
carrier-sensing and dual channel scheme. We also address implementation issues of our CSMA scheme.

12 Coloring Spatial Point Processes With Applications to Peer Discovery in Large Wireless Networks

In this paper, we study distributed channel assignment in wireless networks with applications to peer discovery in ad hoc
wireless networks.We model channel assignment as a coloring problem for spatial point processes in which nodes are
located in a unit cube uniformly at random and each node is assigned one of colors, where each color represents a
channel. The objective is to maximize the spatial separation between nodes of the same color. In general, it is hard to derive
the optimal coloring algorithm, and we therefore consider a natural online greedy coloring algorithm first proposed by Ko
and Rubenstein in 2005.We prove two key results: 1) with just logn/loglog colors, the distance separation achieved by the
greedy coloring algorithm asymptotically matches the optimal distance separation that can be achieved by an algorithm
which is allowed to optimally place the nodes but is allowed to use only one color; and 2) when K=ohm(logn) the greedy
coloring algorithm asymptotically achieves the best distance separation that can be achieved by an algorithm which is
allowed to both optimally color and place nodes. The greedy coloring algorithm is also shown to dramatically outperform a
simple random coloring algorithm. Moreover, the results continue to hold under node mobility.

13 Component-Based Localization in Sparse Wireless Networks

Localization is crucial for wireless ad hoc and sensor networks. As the distance-measurement ranges are often less than
the communication ranges for many ranging systems, most communication- dense wireless networks are localization-
sparse. Consequently, existing algorithms fail to provide accurate localization supports. In order to address this issue, by
introducing the concept of component, we group nodes into components so that nodes are able to better share ranging and
anchor knowledge. Operating on the granularity of components, our design, CALL, relaxes two essential restrictions in

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localization: the node ordering and the anchor distribution. Compared to previous designs, CALL is proven to be able to
locate the same number of nodes using the least information. We evaluate the effectiveness of CALL through extensive
simulations. The results show that CALL locates 90% nodes in a network with average degree 7.5 and 5% anchors, which
outperforms the state-of-the-art design Sweeps by about 40%.

14 Continuous Neighbor Discovery in Asynchronous Sensor Networks

In most sensor networks, the nodes are static. Nevertheless, node connectivity is subject to changes because of
disruptions in wireless communication, transmission power changes, or loss of synchronization between neighboring
nodes. Hence, even after a sensor is aware of its immediate neighbors, it must continuously maintain its view, a process we
call continuous neighbor discovery. In this work, we distinguish between neighbor discovery during sensor network
initialization and continuous neighbor discovery. We focus on the latter and view it as a joint task of all the nodes in every
connected segment. Each sensor employs a simple protocol in a coordinate effort to reduce power consumption without
increasing the time required to detect hidden sensors.

15 Cross-Layer Jamming Detection and Mitigation in Wireless Broadcast Networks

Wireless communication systems are often susceptible to the jamming attack where adversaries attempt to overpower
transmitted signals by injecting a high level of noise. Jamming is difficult to mitigate in broadcast networks because
transmitting and receiving are inherently symmetric operations: A user that possesses the key to decode a transmission
can also use that key to jam the transmission.We describe a code tree system that provides input to the physical layer and
helps the physical layer circumvent jammers. In our system, the transmitter has more information than any proper subset of
receivers. Each receiver cooperates with the transmitter to detect any jamming that affects that receiver. In the resulting
system, each benign user is guaranteed to eliminate the impact of the attacker after some finite number of losses with
arbitrarily high probability. We show that any system that relies on only using spreading code, and no other physical
factors, to mitigate jamming must use at least j+1 codes, where is the number of jammers. We then propose an optimized
scheme that is power-efficient: Each transmission is sent on at most 2j+1 codes simultaneously. Finally, we demonstrate
that our scheme approaches the best possible performance by performing an extensive analysis of the system using both
event-driven ns-2 and chip-accurate MATLAB simulations.

16 Crosstalk-Preventing Scheduling in Singleand Two-Stage AWG-Based Cell Switches

Array waveguide grating (AWG)-based optical switching fabrics are receiving increasing attention due to their simplicity
and good performance. However, AWGs are affected by coherent crosstalk that can significantly impair system operation
when the same wavelength is used simultaneously on several input ports. To permit large port counts in a N cross N AWG,
a possible solution is to schedule data transmissions across the AWG preventing switch configurations that generate large
crosstalk. We study the properties and the existence conditions of switch configurations able to control coherent crosstalk.
The presented results show that, by running a properly constrained scheduling algorithm to avoid or minimize crosstalk, it
is possible to operate an AWG-based switch with large port counts without significant performance degradation.

17 Delay Analysis and Optimality of Scheduling Policies for Multihop Wireless Networks


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We analyze the delay performance of a multihop wireless network with a fixed route between each source–destination pair.
We develop a new queue grouping technique to handle the complex correlations of the service process resulting from the
multihop nature of the flows. A general set-based interference model is assumed that imposes constraints on links that can be
served simultaneously at any given time. These interference constraints are used to obtain a fundamental lower bound on the
delay performance of any scheduling policy for the system. We present a systematic methodology to derive such lower
bounds. For a special wireless system, namely the clique, we design a policy that is sample-path delay-optimal. For the
tandem queue network, where the delay-optimal policy is known, the expected delay of the optimal policy numerically
coincides with the lower bound. We conduct extensive numerical studies to suggest that the average delay of the back-
pressure scheduling policy can be made close to the lower bound by using appropriate functions of queue length.

18 Delay-Optimal Opportunistic Scheduling and Approximations: The Log Rule

This paper considers the design of multiuser opportunistic packet schedulers for users sharing a time-varying wireless
channel from performance and robustness points of view. For a simplified model falling in the classical Markov decision
process framework, we numerically compute and characterize mean-delay-optimal scheduling policies. The computed
policies exhibit radial sum-rate monotonicity: As users’ queues grow linearly, the scheduler allocates service in a manner
that deemphasizes the balancing of unequal queues in favor of maximizing current system throughput (being
opportunistic). This is in sharp contrast to previously proposed throughput-optimal policies, e.g., Exp rule and MaxWeight
(with any positive exponent of queue length). In order to meet performance and robustness objectives, we propose a new
class of policies, called the Log rule, that are radial sum-rate monotone (RSM) and provably throughput-optimal. In fact, it
can also be shown that an RSM policy minimizes the asymptotic probability of sum-queue overflow. We use extensive
simulations to explore various possible design objectives for opportunistic schedulers. When users see heterogenous
channels, we find that emphasizing queue balancing, e.g., Exp rule and MaxWeight, may excessively compromise the
overall delay. Finally, we discuss approaches to implement the proposed policies for scheduling and resource allocation in
OFDMA-based multichannel systems.

19 Differential Encoding of DFAs for Fast Regular Expression Matching

Deep packet inspection is a fundamental task to improve network security and provide application-specific services. State-
of-the-art systems adopt regular expressions due to their high expressive power. They are typically matched through
deterministic finite automata (DFAs), but large rule sets need a memory amount that turns out to be too large for practical
implementation. Many recent works have proposed improvements to address this issue, but they increase the number of
transitions (and then of memory accesses) per character. This paper presents a new representation for DFAs, orthogonal to
most of the previous solutions, called delta finite automata ( dell FA), which considerably reduces states and transitions
while preserving a transition per character only, thus allowing fast matching. A further optimization exploits th order
relationships within the DFA by adopting the concept of “temporary transitions.”.

20 Efficient Multipath Communication for Time-Critical Applications in Underwater Acoustic Sensor Networks


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Due to the long propagation delay and high error rate of acoustic channels, it is very challenging to provide reliable data
transfer for time-critical applications in an energy-efficient way. On the one hand, traditional retransmission upon failure
usually introduces very large end-to-end delay and is thus not proper for time-critical services. On the other hand, common
approaches without retransmission consume lots of energy. In this paper, we propose a new multipath power-control
transmission (MPT) scheme, which can guarantee certain end-to-end packet error rate while achieving a good balance
between the overall energy efficiency and the end-to-end packet delay. MPT smartly combines power control with multipath
routing and packet combining at the destination. With carefully designed power-control strategies, MPT consumes much
less energy than the conventional one-path transmission scheme without retransmission. Besides, since no hop-by-hop
retransmission is allowed, MPT introduces much shorter delays than the traditional one-path scheme with retransmission.
We conduct extensive simulations to evaluate the performance of MPT. Our results show that MPT is highly energy-efficient
with low end-to-end packet delays.

21 Energy-Efficient Protocol for Cooperative Networks

In cooperative networks, transmitting and receiving nodes recruit neighboring nodes to assist in communication. We model
a cooperative transmission link in wireless networks as a transmitter cluster and a receiver cluster. We then propose a
cooperative communication protocol for establishment of these clusters and for cooperative transmission of data. We
derive the upper bound of the capacity of the protocol, and we analyze the end-to-end robustness of the protocol to data-
packet loss, along with the tradeoff between energy consumption and error rate. The analysis results are used to compare
the energy savings and the end-to-end robustness of our protocol with two non-cooperative schemes, as well as to another
cooperative protocol published in the technical literature. The comparison results show that, when nodes are positioned on
a grid, there is a reduction in the probability of packet delivery failure by two orders of magnitude for the values of
parameters considered. Up to 80% in energy savings can be achieved for a grid topology, while for random node placement
our cooperative protocol can save up to 40% in energy consumption relative to the other protocols. The reduction in error
rate and the energy savings translate into increased lifetime of cooperative sensor networks.

22 Exploring Second Life

Social virtual worlds such as Second Life (SL) are digital representations of the real world where human-controlled avatars
evolve and interact through social activities. Understanding the characteristics of virtual worlds can be extremely valuable
in order to optimize their design. In this paper, we perform an extensive analysis of SL. We exploit standard avatar
capabilities to monitor the virtual world, and we emulate avatar behaviors in order to evaluate user experience. We make
several surprising observations.We find that 30% of the regions are never visited during the six-day monitoring period,
whereas less than 1% of the regions have large peak populations. Moreover, the vast majority of regions are static, i.e.,
objects are seldom created or destroyed. Interestingly, we show that avatars interact similarly to humans in real life,
gathering in small groups of 2–10 avatars. We also show that user experience is poor. Most of the time, avatars have an
incorrect view of their neighbor avatars, and inconsistency can last several seconds, impacting interactivity among avatars.

23 Fast Simulation of Service Availability in Mesh Networks With Dynamic Path Restoration

A fast simulation technique based on importance sampling is developed for the analysis of path service availability in mesh
networks with dynamic path restoration. The method combines the simulation of the path rerouting algorithm with a
“dynamic path failure importance sampling” (DPFS) scheme to estimate path availabilities efficiently. In DPFS, the failure
rates of network elements are biased at increased rates until path failures are observed under rerouting. The simulated
model uses “failure equivalence groups,” with finite/infinite sources of failure events and finite/infinite pools of repair
personnel, to facilitate the modeling of bidirectional link failures, multiple in-series link cuts, optical amplifier failures along


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links, node failures, and more general geographically distributed failure scenarios. The analysis of a large mesh network
example demonstrates the practicality of the technique.

24 Forward Correction and Fountain Codes in Delay-Tolerant Networks

Delay-tolerant ad hoc networks leverage the mobility of relay nodes to compensate for lack of permanent connectivity and
thus enable communication between nodes that are out of range of each other. To decrease delivery delay, the information
to be delivered is replicated in the network. Our objective in this paper is to study a class of replication mechanisms that
include coding in order to improve the probability of successful delivery within a given time limit. We propose an analytical
approach that allows to quantify tradeoffs between resources and performance measures (energy and delay). We study the
effect of coding on the performance of the network while optimizing parameters that govern routing. Our results, based on
fluid approximations, are compared to simulations that validate the model.

25 Impact of File Arrivals and Departures on Buffer Sizing in Core Routers

Traditionally, it had been assumed that the efficiency requirements of TCP dictate that the buffer size at the router must be
of the order of the bandwidth-delay (c * RTT) product. Recently, this assumption was questioned in a number of papers, and
the rule was shown to be conservative for certain traffic models. In particular, by appealing to statistical multiplexing, it was
shown that on a router with long-lived connections, buffers of size Q((C*RTT)/root (n)) or even Q(1) are sufficient. In this
paper, we reexamine the buffer-size requirements of core routers when flows arrive and depart. Our conclusion is as
follows: If the core-to-access-speed ratio is large, then Q(1) buffers are sufficient at the core routers; otherwise, larger
buffer sizes do improve the flow-level performance of the users. From a modeling point of view, our analysis offers two new
insights. First, it may not be appropriate to derive buffer-sizing rules by studying a network with a fixed number of users. In
fact, depending upon the core-to-access-speed ratio, the buffer size itself may affect the number of flows in the system, so
these two parameters (buffer size and number of flows in the system) should not be treated as independent quantities.
Second, in the regime where the core-to-access-speed ratio is large, we note that the Q(1) buffer sizes are sufficient for
good performance and that no loss of utilization results, as previously believed.

26 Improved Bounds on the Throughput Efficiency of Greedy Maximal Scheduling in Wireless Networks

In this paper, we derive new bounds on the throughput efficiency of Greedy Maximal Scheduling (GMS) for wireless
networks of arbitrary topology under the general -hop interference model. These results improve the known bounds for
networks with up to 26 nodes under the 2-hop interference model. We also prove that GMS is throughput-optimal in small
networks. In particular, we show that GMS achieves 100% throughput in networks with up to eight nodes under the 2-hop
interference model. Furthermore, we provide a simple proof to show that GMS can be implemented using only local
neighborhood information in networks of any size.

27 Jamming-Aware Traffic Allocation for Multiple-Path Routing Using Portfolio Selection

Multiple-path source routing protocols allow a data source node to distribute the total traffic among available paths. In this

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paper, we consider the problem of jamming-aware source routing in which the source node performs traffic allocation
based on empirical jamming statistics at individual network nodes. We formulate this traffic allocation as a lossy network
flow optimization problem using portfolio selection theory from financial statistics. We show that in multisource networks,
this centralized optimization problem can be solved using a distributed algorithm based on decomposition in network utility
maximization (NUM). We demonstrate the network’s ability to estimate the impact of jamming and incorporate these
estimates into the traffic allocation problem. Finally, we simulate the achievable throughput using our proposed traffic
allocation method in several scenarios.

28 Licklider Transmission Protocol (LTP)-Based DTN for Cislunar Communications

Delay/disruption-tolerant networking (DTN) technology offers a new solution to highly stressed communications in space
environments, especially those with long link delay and frequent link disruptions in deep-space missions. To date, little
work has been done in evaluating the performance of the available “convergence layer” protocols of DTN, especially the
Licklider Transmission Protocol (LTP), when they are applied to an interplanetary Internet (IPN). In this paper, we present an
experimental evaluation of the Bundle Protocol (BP) running over various “convergence layer” protocols in a simulated
cislunar communications environment characterized by varying degrees of signal propagation delay and data loss. We
focus on the LTP convergence layer (LTPCL) adapter running on top of UDP/IP (i.e., BP/LTPCL/UDP/IP). The performance of
BP/LTPCL/UDP/IP in realistic file transfers over a PC-based network test bed is compared to that of two other DTN protocol
stack options, BP/TCPCL/TCP/IP and BP/UDPCL/UDP/IP. A statistical method of -test is also used for analysis of the
experimental results. The experiment results show that LTPCL has a significant performance advantage over Transmission
Control Protocol convergence layer (TCPCL) for link delays longer than 4000 ms regardless of the bit error rate (BER). For a
very lossy channel with a BER of around 10 , LTPCL has a significant goodput advantage over TCPCL at all the link delay
levels studied, with an advantage of around 3000 B/s for delays longer than 1500 ms. LTPCL has a consistently significant
goodput advantage over UDPCL, around 2500–3000 B/s, at all levels of link delays and BERs.

29 Lifetime and Coverage Guarantees Through Distributed Coordinate-Free Sensor Activation

In wireless sensor networks (WSNs), a large number of sensors perform distributed sensing of a target field. A
sensor cover is a subset of the set of all sensors that covers the target field. The lifetime of the network is the time
from the point the network starts operation until the set of all sensors with nonzero remaining energy does not
constitute a sensor cover any more. An important goal in sensor networks is to design a schedule—that is, a
sequence of sensor covers to activate in every time slot—so as to maximize the lifetime of the network. In this paper,
we design a polynomial-time distributed algorithm for maximizing the lifetime of the network and prove that its
lifetime is at most a factor O (logn * lognB) lower than the maximum possible lifetime, where n is the number of
sensors and is an upper bound on the initial energy of each sensor. Our algorithm does not require knowledge of
the locations of nodes or directional information, which is difficult to obtain in sensor networks. Each sensor only
needs to know the distances between adjacent nodes in its transmission range and their sensing radii. In every slot,
the algorithm first assigns a weight to each node that is exponential in the fraction of its initial energy that has been
used up so far. Then, in a distributed manner, it finds an O(logn) approximate minimum weight sensor cover, which it
activates in the slot.

30 Live Streaming With Receiver-Based Peer-Division Multiplexing


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A number of commercial peer-to-peer (P2P) systems for live streaming have been introduced in recent years. The behavior
of these popular systems has been extensively studied in several measurement papers. Due to the proprietary nature of
these commercial systems, however, these studies have to rely on a “black-box” approach, where packet traces are
collected from a single or a limited number of measurement points, to infer various properties of traffic on the control and
data planes. Although such studies are useful to compare different systems from the end-user’s perspective, it is difficult to
intuitively understand the observed properties without fully reverse-engineering the underlying systems. In this paper, we
describe the network architecture of Zattoo, one of the largest production live streaming providers in Europe at the time of
writing, and present a large-scale measurement study of Zattoo using data collected by the provider. To highlight, we found
that even when the Zattoo system was heavily loaded with as high as 20 000 concurrent users on a single overlay, the
median channel join delay remained less than 2–5 s, and that, for a majority of users, the streamed signal lags over-the-air
broadcast signal by no more than 3 s.

31 Local Restoration With Multiple Spanning Trees in Metro Ethernet Networks

Ethernet is becoming a preferred technology to be extended to metropolitan area networks (MANs) due to its low cost,
simplicity, and ubiquity. However, current Ethernet lacks a fast failure recovery mechanism as it reconstructs the spanning
tree after the failure is detected, which commonly requires tens of seconds. Some fast failure-handling methods based on
multiple spanning trees have been proposed in the literature, but these approaches are either centralized or require
periodic message broadcasting over the entire network. In this paper, we propose a local restoration mechanism for metro
Ethernet using multiple spanning trees, which is distributed and fast and does not need failure notification. Upon failure of
a single link, the upstream switch locally restores traffic to preconfigured backup spanning trees. We propose two
restoration approaches, connection-based and destination-based, to select backup trees. We formulate the tree pre
configuration problem that includes working spanning tree assignment and backup spanning tree configuration. We prove
that the pre configuration problem is NP-complete and develop an integer linear programming model. We also develop
heuristic algorithms for each restoration approach to reduce the computation complexity. To evaluate the effectiveness of
our heuristic algorithms, we carry out the simulation on grid and random networks. The simulation results show that our
heuristic algorithms have comparable performance close to the optimal solutions, and both restoration approaches can
efficiently utilize the network bandwidth to handle single link failures.

32 Maelstrom: Transparent Error Correction for Communication Between Data Centers

The global network of data centers is emerging as an important distributed systems paradigm—commodity clusters
running high-performance applications, connected by high-speed “lambda” networks across hundreds of milliseconds of
network latency. Packet loss on long-haul networks can cripple applications and protocols: A loss rate as low as 0.1% is
sufficient to reduce TCP/IP throughput by an order of magnitude on a 1-Gb/s link with 50-ms one-way latency. Maelstrom is
an edge appliance that masks packet loss transparently and quickly from intercluster protocols, aggregating traffic for
high-speed encoding and using a new forward error correction scheme to handle bursty loss.

33 Measuring Multipath Routing in the Internet

Tools to measure Internet properties usually assume the existence of just one single path from a source to a destination.


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However, load-balancing capabilities, which create multiple active paths between two end-hosts, are available in most
contemporary routers. This paper extends Paris traceroute and proposes an extensive characterization of multipath routing
in the Internet. We use Paris traceroute from RON and PlanetLab nodes to collect various datasets in 2007 and 2009. Our
results show that the traditional concept of a single network path between hosts no longer holds. For instance, 39% of the
source–destination pairs in our 2007 traces traverse a load balancer. This fraction increases to 72% if we consider the paths
between a source and a destination network. In 2009, we notice a consolidation of per-flow and per-destination techniques
and confirm that per-packet load balancing is rare.

34 Model-Based Identification of Dominant Congested Links

In this paper, we propose a model-based approach that uses periodic end–end probes to identify whether a “dominant
congested link” exists along an end–end path. Informally, a dominant congested link refers to a link that incurs the most
losses and significant queuing delays along the path. We begin by providing a formal yet intuitive definition of dominant
congested link and present two simple hypothesis tests to identify whether such a link exists. We then present a novel
model-based approach for dominant congested link identification that is based on interpreting probe loss as an unobserved
(virtual) delay. We develop parameter inference algorithms for hidden Markov model (HMM) and Markov model with a
hidden dimension (MMHD) to infer this virtual delay. Our validation using ns simulation and Internet experiments
demonstrate that this approach can correctly identify a dominant congested link with only a small amount of probe data.
We further provide an upper bound on the maximum queuing delay of the dominant congested link once we identify that
such a link exists.

35 Network-Coding Multicast Networks With QoS Guarantees

It is well known that without admission control, network congestion is bound to occur. However, to implement admission
control is difficult in IP-based networks, which are constructed out of the end-to-end principle, and semantics of most major
signaling protocols can only be interpreted at the edge of the network. Even if routers can perform admission control
internally, the path computation and the state updating activities required for setting up and tearing down each flow will
overwhelm the network. A new QoS architecture, called a nonblocking network, has been proposed recently, and it requires
no internal admission control and can still offer hard QoS guarantees. In this architecture, as long as each edge node
admits not more than a specified amount of traffic, the network will never experience link congestion. For multicast
networks, the main problem with this approach is low throughput. Conventional tree-based multicast routing algorithms
lead to a throughput so low that the nonblocking concept is rendered impractical. In this paper, we show how network
coding can solve this problem. We demonstrate that a nonblocking unicast network and a multicast network share the
same optimal paths, and that a nonblocking multicast network with network coding can admit the same amount of traffic as
a nonblocking unicast network. The above conclusions apply to explicit-routing (MPLS-like) and shortest-path routing (IP-
like) networks.

36 On Combining Shortest-Path and Back-Pressure Routing Over Multihop Wireless Networks

Back-pressure-type algorithms based on the algorithm by Tassiulas and Ephremides have recently received much attention
for jointly routing and scheduling over multihop wireless networks. However, this approach has a significant weakness in
routing because the traditional back-pressure algorithm explores and exploits all feasible paths between each source and
destination. While this extensive exploration is essential in order to maintain stability when the network is heavily loaded,
under light or moderate loads, packets may be sent over unnecessarily long routes, and the algorithm could be very


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inefficient in terms of end-to-end delay and routing convergence times. This paper proposes a new routing/scheduling
back-pressure algorithm that not only guarantees network stability (throughput optimality), but also adaptively selects a set
of optimal routes based on shortest-path information in order to minimize average path lengths between each source and
destination pair. Our results indicate that under the traditional back-pressure algorithm, the end-to-end packet delay first
decreases and then increases as a function of the network load (arrival rate). This surprising low-load behavior is explained
due to the fact that the traditional back-pressure algorithm exploits all paths (including very long ones) even when the
traffic load is light. On the other-hand, the proposed algorithm adaptively selects a set of routes according to the traffic load
so that long paths are used only when necessary, thus resulting in much smaller end-to-end packet delays as compared to
the traditional back-pressure algorithm.

37 On Cooperative Settlement Between Content, Transit, and Eyeball Internet Service Providers

Internet service providers (ISPs) depend on one another to provide global network services. However, the profit-seeking
nature of the ISPs leads to selfish behaviors that result in inefficiencies and disputes in the network. This concern is at the
heart of the “network neutrality” debate, which also asks for an appropriate compensation structure that satisfies all types
of ISPs. Our previous work showed in a general network model that the Shapley value has several desirable properties, and
that if applied as the profit model, selfish ISPs would yield globally optimal routing and interconnecting decisions. In this
paper, we use a more detailed and realistic network model with three classes of ISPs: content, transit, and eyeball. This
additional detail enables us to delve much deeper into the implications of a Shapley settlement mechanism. We derive
closed-form Shapley values for more structured ISP topologies and develop a dynamic programming procedure to compute
the Shapley values under more diverse Internet topologies.We also identify the implications on the bilateral compensation
between ISPs and the pricing structures for differentiated services. In practice, these results provide guidelines for solving
disputes between ISPs and for establishing regulatory protocols for differentiated services and the industry.

38 On the Complexity of the Regenerator Placement Problem in Optical Networks

Placement of regenerators in optical networks has attracted the attention of recent research works in optical networks. In
this problem, we are given a network with an underlying topology of a graph G and with a set of requests that correspond to
paths in G. There is a need to put a regenerator every certain distance, because of a decrease in the power of the signal. In
this paper, we investigate the problem of minimizing the number of locations to place the regenerators. We present
analytical results regarding the complexity of this problem, in four cases, depending on whether or not there is a bound on
the number of regenerators at each node, and depending on whether or not the routing is given or only the requests are
given (and part of the solution is also to determine the actual routing). These results include polynomial time algorithms,
NP-completeness results, approximation algorithms, and in approximability results.

39 On the Dimensioning of WDM Optical Networks With Impairment-Aware Regeneration

Although the problem of dimensioning an optical transport network is not new, the consideration of signal quality
degradation caused by the optical medium calls for revisiting the problem in the context of dimensioning optical
wavelength division multiplexing (WDM) networks. This paper addresses the issue of minimum-cost planning of long-reach
WDM networks in combination with optoelectronic signal regeneration as a countermeasure for sanitizing the signal quality
of lightpaths that are found to be impaired. The commonly used method of placing regenerators proportionally to the
physical distance covered by a lightpath is evaluated in a realistic dimensioning scenario and for various heterogeneity
degrees of optical equipment, showing that it is plagued with a serious tradeoff between efficacy and cost of regeneration.
As a remedy, we propose a novel method for design/dimensioning and regeneration placement for WDM networks that
employs impairment-awareness. Through experimentation with real optical network configurations and for varying


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heterogeneity of optical equipment, the proposed method is shown to break the aforementioned tradeoff, resulting in
significant reduction in regeneration effort compared to distance-based regeneration. This is achieved without
compromising the signal quality of any of the lightpaths selected by the dimensioning process and with increased cost
efficiency.

40 On the Levy-Walk Nature of Human Mobility

We report that human walk patterns contain statistically similar features observed in Levy walks. These features include
heavy-tail flight and pause-time distributions and the superdiffusive nature of mobility. Human walks are not random walks,
but it is surprising that the patterns of human walks and Levy walks contain some statistical similarity. Our study is based
on 226 daily GPS traces collected from 101 volunteers in five different outdoor sites. The heavy-tail flight distribution of
human mobility induces the super-diffusivity of travel, but up to 30 min to 1 h due to the boundary effect of people’s daily
movement, which is caused by the tendency of people to move within a predefined (also confined) area of daily activities.
These tendencies are not captured in common mobility models such as random way point (RWP). To evaluate the impact of
these tendencies on the performance of mobile networks, we construct a simple truncated Levy walk mobility (TLW) model
that emulates the statistical features observed in our analysis and under which we measure the performance of routing
protocols in delay-tolerant networks (DTNs) and mobile ad hoc networks (MANETs). The results indicate the following.
Higher diffusivity induces shorter intercontact times in DTN and shorter path durations with higher success probability in
MANET. The diffusivity of TLW is in between those of RWP and Brownian motion (BM). Therefore, the routing performance
under RWP as commonly used in mobile network studies and tends to be overestimated for DTNs and underestimated for
MANETs compared to the performance under TLW.

41 On the Price of Security in Large-Scale Wireless Ad Hoc Networks

Security always comes with a price in terms of performance degradation, which should be carefully quantified. This is
especially the case for wireless ad hoc networks (WANETs), which offer communications over a shared wireless channel
without any preexisting infrastructure. Forming end-to-end secure paths in such WANETs is more challenging than in
conventional networks due to the lack of central authorities, and its impact on network performance is largely untouched in
the literature. In this paper, based on a general random network model, the asymptotic behaviors of secure throughput and
delay with the common transmission range Tn and the probability Pf of neighboring nodes having a primary security
association are quantified when the network size n is sufficiently large. The costs and benefits of secure-link-augmentation
operations on the secure throughput and delay are also analyzed. In general, security has a cost: Since we require all the
communications operate on secure links, there is a degradation in the network performance when Pf<1. However, one
important exception is that when Pf i(ohm(1/log(n))), the secure throughput remains at the Gupta and Kumar bound of
omega(1/root(n logn)) packets/time slot, wherein no security requirements are enforced onWANETs. This implies that even
when the Pf goes to zero as the network size becomes arbitrarily large, it is still possible to build throughput-order-optimal
secure WANETs, which is of practical interest since Pf is very small in many practical large-scale WANETs.

42 Opportunity Cost Analysis for Dynamic Wavelength Routed Mesh Networks

Optical backbone networks are becoming increasingly intelligent and flexible. These networks are able to establish high-
bandwidth wavelength connections on-demand to support future network-centric applications. Choosing an efficient path
in a timely manner, while considering important criteria such as operation costs and network performance, is a key problem
confronting the network operators. Subtle path preferences of different dynamic routing algorithms (which are usually
ignored by traditional analysis techniques) can make a significant difference in performance on mesh networks. It opens
new research to advance routing algorithms in both analysis and implementation paradigms. In this paper, we propose an
opportunity cost model that provides fast and accurate analysis for threshold-based online congestion-aware routing

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algorithms. The model is simple to compute, robust to different network topologies, and scalable. We show that our model
further aids in the design of a number of new routing algorithms that can be easily applied to practical networks. In contrast
to previous work, the optimal threshold values for our algorithms can be identified analytically, and the values sustain good
performance on different network topologies and sizes.

43 Optimal Anycast Technique for Delay-Sensitive Energy-Constrained Asynchronous Sensor Networks

In wireless sensor networks (WSNs), asynchronous sleep–wake scheduling protocols can be used to significantly reduce
energy consumption without incurring the communication overhead for clock synchronization needed for synchronous
sleep–wake scheduling protocols. However, these savings could come at a significant cost in delay performance. Recently,
researchers have attempted to exploit the inherent broadcast nature of the wireless medium to reduce this delay with
virtually no additional energy cost. These schemes are called “anycasting,” where each sensor node forwards the packet to
the first node that wakes up among a set of candidate next-hop nodes. In this paper, we develop a delay-optimal anycasting
scheme under periodic sleep–wake patterns. Our solution is computationally simple and fully distributed. Furthermore, we
show that periodic sleep–wake patterns result in the smallest delay among all wake-up patterns under given energy
constraints. Simulation results illustrate the benefit of our proposed schemes over the state of the art.

44 Parametric Methods for Anomaly Detection in Aggregate Traffic

This paper develops parametric methods to detect network anomalies using only aggregate traffic statistics, in contrast to
other works requiring flow separation, even when the anomaly is a small fraction of the total traffic. By adopting simple
statistical models for anomalous and background traffic in the time domain, one can estimate model parameters in real
time, thus obviating the need for a long training phase or manual parameter tuning. The proposed bivariate parametric
detection mechanism (bPDM) uses a sequential probability ratio test, allowing for control over the false positive rate while
examining the tradeoff between detection time and the strength of an anomaly. Additionally, it uses both traffic-rate and
packet-size statistics, yielding a bivariate model that eliminates most false positives. The method is analyzed using the bit-
rate signal-to-noise ratio (SNR) metric, which is shown to be an effective metric for anomaly detection. The performance of
the bPDM is evaluated in three ways. First, synthetically generated traffic provides for a controlled comparison of detection
time as a function of the anomalous level of traffic. Second, the approach is shown to be able to detect controlled artificial
attacks over the University of Southern California (USC), Los Angeles, campus network in varying real traffic mixes. Third,
the proposed algorithm achieves rapid detection of real denial-of-service attacks as determined by the replay of previously
captured network traces. The method developed in this paper is able to detect all attacks in these scenarios in a few
seconds or less.

45 Pareto Boundary of Utility Sets for Multiuser Wireless Systems

Pareto optimality is an important property in game theory and mechanism design, which can be utilized to design resource
allocation strategies in wireless systems. We analyze the structure of the boundary points of certain utility sets based on
interference functions. We particularly investigate the cases with no power constraints, with individual power constraints,
and with a total power constraint. We display the dependency between Pareto optimality and interference coupling in
wireless systems. An axiomatic framework of interference functions and a global dependency matrix is used to characterize
interference coupling in wireless systems. The relationship between interference-balancing functions and Pareto optimality
of the boundary points is elucidated. Among other results, it is shown that the boundary points of utility sets with individual
power constraints and with strictly monotonic interference functions are Pareto-optimal if and only if the corresponding
restricted global dependency matrix is irreducible. The obtained results provide certain insight when suitable algorithms
can be designed for network utility maximization.


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46 Peering Equilibrium Multipath Routing: A Game Theory Framework for Internet Peering Settlements

It is generally admitted that interdomain peering links represent nowadays the main bottleneck of the Internet, particularly
because of lack of coordination between providers, which use independent and “selfish” routing policies. We are interested
in identifying possible “light” coordination strategies that would allow carriers to better control their peering links while
preserving their independence and respective interests. We propose a robust multipath routing coordination framework for
peering carriers, which relies on the multiple-exit discriminator (MED) attribute of Border Gateway Protocol (BGP) as
signaling medium. Our scheme relies on a game theory modeling, with a non-cooperative potential game considering both
routing and congestions costs. Peering equilibrium multipath (PEMP) coordination policies can be implemented by
selecting Pareto-superior Nash equilibria at each carrier. We compare different PEMP policies to BGP Multipath schemes by
emulating a realistic peering scenario. Our results show that the routing cost can be decreased by roughly 10% with PEMP.
We also show that the stability of routes can be significantly improved and that congestion can be practically avoided on
the peering links. Finally, we discuss practical implementation aspects and extend the model to multiple players
highlighting the possible incentives for the resulting extended peering framework.

47 Practical Computation of Optimal Schedules in Multihop Wireless Networks

Interference and collisions greatly limit the throughput of mesh networks that use contention-based MAC protocols such as
IEEE 802.11. Significantly higher throughput is achievable if transmissions are scheduled. However, traditional methods to
compute optimal schedules are computationally intractable (unless co-channel interference is neglected). This paper
presents a practical technique to compute optimal schedules. The resulting algorithm searches for a low-dimensional
optimization problem that has the same solution as the full problem. Such a low-dimensional problem is shown to always
exist. The resulting algorithm converges arithmetically fast or geometrically fast, depending on whether the objective is to
maximize the proportional fair throughput or to maximize the minimum throughput, where the minimum is over all flows in
the network. At each iteration of the algorithm, a graph-theoretic optimization known as the maximum weighted
independent set (MWIS) problem must be solved. While the general MWIS problem is NP-hard in the worst case, we find that
the MWIS can be solved efficiently. Specifically, computational experiments on over 17 000 topologies indicate that the ratio
of the time to solve the MWIS and the mean degree of the conflict graph grows polynomially with the number of nodes.

48 Practical Routing in a Cyclic MobiSpace

A key challenge of routing in delay-tolerant networks (DTNs) is finding routes that have high delivery rates and low end-to-
end delays. When future connectivity information is not available, opportunistic routing is preferred in DTNs, in which
messages are forwarded to nodes with higher delivery probabilities. We observe that real objects have repetitive motions,
whereas no prior research work has investigated the time-varying delivery probabilities of messages between nodes at
different times during a repetition of motion of the nodes.We propose to use the expected minimum delay (EMD) as a new
delivery probability metric in DTNs with repetitive but nondeterministic mobility. First, we model the network as a
probabilistic time–space graph with historical contact information or prior knowledge about the network. We then translate
it into a probabilistic state–space graph, in which the time dimension is removed.With the state–space graph, we apply the
Markov decision process to derive the EMDs of the messages. We propose an EMD-based probabilistic routing protocol,
called routing in cyclic MobiSpace (RCM). To make RCM more practical, we show a simple extension that reduces routing
information exchanged among nodes. We perform simulations with real and synthetic traces. Simulation results show that
RCM outperforms several existing opportunistic routing protocols.


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49 Predictive Resource Management of Multiple Monitoring Applications

We propose a predictive resource management scheme for network monitoring systems that can proactively shed excess
load while maintaining the accuracy of monitoring applications within bounds defined by the operator. The main novelty of
our scheme is that it considers monitoring applications as black boxes, with arbitrary (and highly variable) input traffic and
processing cost. This way, the monitoring system preserves a high degree of flexibility, increasing the range of
applications and network scenarios where it can be used. We implemented our load-shedding-based resource management
scheme in an existing network monitoring system and deployed it in a large research and educational network. We present
experimental evidence of the performance and robustness of our system with multiple concurrent monitoring applications
during long-lived executions and using real-world traffic traces.

50 Primary User Activity Modeling Using First-Difference Filter Clustering and Correlation in Cognitive Radio Networks

In many recent studies on cognitive radio (CR) networks, the primary user activity is assumed to follow the Poisson traffic
model with exponentially distributed interarrivals. The Poisson modeling may lead to cases where primary user activities
are modeled as smooth and burst-free traffic. As a result, this may cause the cognitive radio users to miss some available
but unutilized spectrum, leading to lower throughput and high false-alarm probabilities. The main contribution of this paper
is to propose a novel model to parametrize the primary user traffic in a more efficient and accurate way in order to
overcome the drawbacks of the Poisson modeling. The proposed model makes this possible by arranging the first-
difference filtered and correlated primary user data into clusters. In this paper, a new metric called the Primary User Activity
Index, , is introduced, which accounts for the relation between the cluster filter output and correlation statistics. The
performance of the proposed model is evaluated by means of traffic estimation accuracy, false-alarm probabilities while
keeping the detection probability of primary users at a constant value. Simulation results show that the appropriate
selection of the Primary User Activity Index, higher primary-user detection accuracy, reduced false-alarm probabilities, and
higher throughput can be achieved by the proposed model.

51 ProgME: Towards Programmable Network MEasurement

Traffic measurements provide critical input for a wide range of network management applications, including traffic
engineering, accounting, and security analysis. Existing measurement tools collect traffic statistics based on some
predetermined, inflexible concept of “flows.” They do not have sufficient built-in intelligence to understand the application
requirements or adapt to the traffic conditions. Consequently, they have limited scalability with respect to the number of
flows and the heterogeneity of monitoring applications. We present ProgME, a Programmable MEasurement architecture
based on a novel concept of flowset—an arbitrary set of flows defined according to application requirements and/or traffic
conditions. Through a simple flowset composition language, ProgME can incorporate application requirements, adapt itself
to circumvent the scalability challenges posed by the large number of flows, and achieve a better application-perceived
accuracy. The modular design of ProgME enables it to exploit the surging popularity of multicore processors to cope with
7-Gb/s line rate. ProgME can analyze and adapt to traffic statistics in real time. Using sequential hypothesis test, ProgME
can achieve fast and scalable heavy hitter identification.


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52 Risk-Aware Provisioning for Optical WDM Mesh Networks

A service-level agreement (SLA) typically specifies, among other metrics, the availability a service provider (SP) promises
to a customer. In an optical wavelength division multiplexing (WDM) network, connection-oriented provisioning is
commonly based on whether the path’s statistical availability complies with the SLA-requested availability. Because of the
stochastic nature of network failures, the actually provisioned availability over a specific time period is subject to
uncertainty, and hence the SLA is usually at risk.We consider this uncertainty and study provisioning to minimize SLA
violations. We show that the SLA Violation Risk is affected by a number of factors (e.g., failure profiles, availability target,
and penalty period), and hence cannot simply be characterized by statistical path availability. We formulate the problem of
risk-aware provisioning in WDM mesh networks, where path selection is dictated by SLA Violation Risk. In particular, we
focus on devising an efficient scheme capable of computing path(s) that are likely to successfully accommodate the SLA-
requested availability. A novel technique is applied to convert links with heterogeneous failure profiles to reference links
that capture the main risk features in a relative manner. Based on the “reference link” concept, our Risk-Aware Provisioning
scheme uses only limited failure information. We also extend our Risk-Aware Provisioning to use shared-path protection
(SPP) for connections with strict availability requirements. We evaluate the performance and demonstrate the effectiveness
of our schemes in terms of SLA violation ratio compared to the generic availability- aware approaches.

53 Robust Network Codes for Unicast Connections: A Case Study

We consider the problem of establishing reliable unicast connections across a communication network with
nonuniform edge capacities. Our goal is to provide instantaneous recovery from single edge failures. With
instantaneous recovery, the destination node can decode the packets sent by the source node even if one of the
network edges fails, without the need of retransmission or rerouting. It has been recognized that the network coding
technique offers significant advantages for this problem over standard solutions such as disjoint path routing and
diversity coding. We focus on two cases of practical interest: 1) backup protection of a single flow that can be split
into two subflows; and 2) shared backup protection of two unicast flows. We present an efficient network coding
algorithm that operates over a small finite field (GF(2)). The small size of the underlying field results in a significant
reduction in the computational and communication overhead associated with the practical implementation of the
network coding technique. Our algorithm exploits the unique structure of minimum coding networks, i.e., networks
that do not contain redundant edges. We also consider the related capacity reservation problem and present an
approximation algorithm that finds a solution whose cost is at most two times more than the optimum.

54 ROC: Resilient Online Coverage for Surveillance Applications

We consider surveillance applications in which sensors are deployed in large numbers to improve coverage fidelity.
Previous research has studied how to select active sensor covers (subsets of nodes that cover the field) to efficiently
exploit redundant node deployment and tolerate unexpected node failures. Little attention was given to studying the
tradeoff between fault tolerance and energy efficiency in sensor coverage. In this work, our objectives are twofold. First, we
aim at rapidly restoring field coverage under unexpected sensor failures in an energy-efficient manner. Second, we want to
flexibly support different degrees of redundancy in the field without needing centralized control. To meet these objectives,
we propose design guidelines for applications that employ distributed cover-selection algorithms to control the degree of
redundancy at local regions in the field. In addition, we develop a new distributed technique to facilitate switching between
active covers without the need for node synchronization. Distributed cover selection protocols can be integrated into our
referred to as “resilient online coverage” (ROC) framework. A key novelty in ROC is that it allows every sensor to control

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the degree of redundancy and surveillance in its region according to current network conditions. We analyze the benefits of
ROC in terms of energy efficiency and fault tolerance. Through extensive simulations, we demonstrate the effectiveness of
ROC in operational scenarios and compare its performance with previous surveillance techniques.

55 Scalable and Cost-Effective Interconnection of Data-Center Servers Using Dual Server Ports

The goal of data-center networking is to interconnect a large number of server machines with low equipment cost
while providing high network capacity and high bisection width. It is well understood that the current practice where
servers are connected by a tree hierarchy of network switches cannot meet these requirements. In this paper, we
explore a new server-interconnection structure. We observe that the commodity server machines used in today’s
data centers usually come with two built-in Ethernet ports, one for network connection and the other left for backup
purposes.We believe that if both ports are actively used in network connections, we can build a scalable, cost-
effective interconnection structure without either the expensive higher-level large switches or any additional
hardware on servers. We design such a networking structure called FiConn. Although the server node degree is only
2 in this structure, we have proven that FiConn is highly scalable to encompass hundreds of thousands of servers
with low diameter and high bisection width. We have developed a low-overhead traffic-aware routing mechanism to
improve effective link utilization based on dynamic traffic state. We have also proposed how to incrementally deploy
FiConn.

56 Scheduling Algorithms for Multicarrier Wireless Data Systems

We consider the problem of scheduling multicarrier wireless data in systems such as IEEE 802.16 (WiMAX). Each
scheduling decision involves assigning carriers to users for each time slot, subject to the constraint that each carrier is
assigned to at most one user, but multiple carriers can potentially be assigned to the same user. One important aspect of
our problem is that a scheduler knows the channel rates across all users and all carriers whenever a scheduling decision is
made. This “global” information may give a potential for enhancing performance via an optimized allocation of carriers to
users. We analyze this problem in a situation where finite queues are fed by a data arrival process. The well-known
MaxWeight algorithm for the single-carrier setting maximizes the product of queue size and service rate.We focus on how
to adapt MaxWeight to the multicarrier setting. If the same objective is pursued, more service than needed may be assigned
to drain a queue, thereby creating wastage. While a simple variant in the objective forbids this wastage, it turns an easy-to-
compute old objective into an intractable new objective. We state the hardness of the new optimization problems and
propose several extremely simple algorithms with provable performance bounds. We conclude with supporting simulation
examples.

57 Self-Reconfigurable Wireless Mesh Networks

During their lifetime, multihop wireless mesh networks (WMNs) experience frequent link failures caused by channel
interference, dynamic obstacles, and/or applications’ bandwidth demands. These failures cause severe performance
degradation in WMNs or require expensive manual network management for their real-time recovery. This paper presents
an autonomous network reconfiguration system (ARS) that enables a multiradio WMN to autonomously recover from local
link failures to preserve network performance. By using channel and radio diversities in WMNs, ARS generates necessary
changes in local radio and channel assignments in order to recover from failures. Next, based on the thus-generated
configuration changes, the system cooperatively reconfigures network settings among local mesh routers. ARS has been
implemented and evaluated extensively on our IEEE 802.11-based WMN test-bed as well as through ns2-based simulation.
Our evaluation results show that ARS outperforms existing failure-recovery schemes in improving channel-efficiency by
more than 90% and in the ability of meeting the applications’ bandwidth demands by an average of 200%.


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58 SPAF: Stateless FSA-Based Packet Filters

We propose a stateless packet filtering technique based on finite-state automata (FSA). FSAs provide a comprehensive
framework with well-defined composition operations that enable the generation of stateless filters from high-level
specifications and their compilation into efficient executable code without resorting to various opportunistic optimization
algorithms. In contrast with most traditional approaches, memory safety and termination can be enforced with minimal run-
time overhead even in cyclic filters, thus enabling full parsing of complex protocols and supporting recursive encapsulation
relationships. Experimental evidence shows that this approach is viable and improves the state of the art in terms of filter
flexibility, performance, and scalability without incurring in the most common FSA deficiencies, such as state-space
explosion.

59 Star-Block Design in Two-Level Survivable Optical Networks

An efficient fault restoration framework is proposed for accomplishing loopback recovery in optical networks. The
proposed -cycle-based framework achieves both a minimal spare capacity requirement and a rapid restoration time. In the
proposed approach, an algorithm designated as Star-Block is used to simplify the original topology to a 2-connected graph
and to partition the graph into multiple blocks, where each block contains a center node and the minimum number of
neighboring nodes that collectively form a complete cycle. The simplified graph is then restored to the original topology
using conventional graph rules. The Block Selection algorithm is then used to assign the edges belonging to multiple
blocks to an appropriate block for fault recovery purposes.Within each block, the working flows are restored in real-time via
local -cycles on the on-cycle and spoke fibers. The performance of the proposed protection framework is evaluated
numerically in terms of the spare capacity to working capacity ratio and the length of the restoration path. The framework
has a better spare capacity efficiency than existing loopback recovery schemes or the conventional -cycles approach. In
addition, the Star-Block decomposition algorithm shortens the average length of the restoration path and therefore reduces
the restoration time. Finally, the protection scheme not only provides a differentiated recovery service for traffic with
different QoS requirements in the event of single-link failures within a single block, but also supports multiple-fault
restoration for the case in which multiple single-link failures occur simultaneously.

60 Stochastic Model and Connectivity Dynamics for VANETs in Signalized Road Systems

The space and time dynamics of moving vehicles regulated by traffic signals governs the node connectivity and
communication capability of vehicular ad hoc networks (VANETs) in urban environments. However, none of the previous
studies on node connectivity has considered such dynamics with the presence of traffic lights and vehicle interactions. In
fact, most of them assume that vehicles are distributed homogeneously throughout the geographic area, which is
unrealistic. We introduce in this paper a stochastic traffic model for VANETs in signalized urban road systems. The
proposed model is a composite of the fluid model and stochastic model. The former characterizes the general flow and
evolution of the traffic stream so that the average density of vehicles is readily computable, while the latter takes into
account the random behavior of individual vehicles. As the key contribution of this paper, we attempt to approximate
vehicle interactions and capture platoon formations and dissipations at traffic signals through a density- dependent
velocity profile. The stochastic traffic model with approximation of vehicle interactions is evaluated with extensive


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simulations, and the distributional result of the model is validated against real-world empirical data in London. In general,
we show that the fluid model can adequately describe the mean behavior of the traffic stream, while the stochastic model
can approximate the probability distribution well even when vehicles interact with each other as their movement is
controlled by traffic lights. With the knowledge of the mean vehicular density dynamics and its probability distribution from
the stochastic traffic model, we determine the degree of connectivity in the communication network and illustrate that
system engineering and planning for optimizing both the transport (in terms of congestion) and communication networks
(in terms of connectivity) can be carried out with the proposed model.

61 Survivable Multipath Provisioning With Differential Delay Constraint in Telecom Mesh Networks

Survivability is a critical concern in modern telecom mesh networks because the failure of a network element may cause
tremendous data and revenue loss in such networks using high-capacity optical fibers employing wavelength-division
multiplexing (WDM). Multipath provisioning is a key feature of next-generation SONET/SDH networks (which can be used on
top of optical WDM), and they can support virtual concatenation (VCAT); thus, multipath provisioning can significantly
outperform single-path provisioning in resource efficiency, service resilience, and flexibility. However, in multipath
provisioning, differential delay is an important constraint that should be considered. We investigate survivability of service
paths based on differential-delay constraint (DDC) and multipath provisioning together in telecom backbone mesh
networks. We propose the Shared Protection of the Largest Individual Traversed link (SPLIT) method for survivable
multipath provisioning and present a DDC-based algorithm for multipath routing subject to DDC. We also compare the DDC-
based algorithm with the K shortest link-disjoint paths (KDP) algorithm, using SPLIT, under dynamic service requests. We
find that exploiting link-disjoint paths is very efficient for survivable multipath provisioning, and our algorithm is resource-
efficient, has low signaling overhead, and has fast fault recovery for survivable multipath provisioning with DDC. For a 5-ms
DDC, our algorithm can decrease the bandwidth blocking ratio (BBR) significantly in typical U.S. backbone networks.

62 SWARM: The Power of Structure in Community Wireless Mesh Networks

Community wireless networks (CWNs) have been proposed to spread broadband network access to underprivileged,
underprovisioned, and remote areas. Research has focused on optimizing network performance through intelligent routing
and scheduling, borrowing solutions from mesh networks. Surprisingly, however, there has been no work on how to make
efficient use of multiple channels in CWNs in the presence of multiple gateways and a single radio per device. In fact,
today’s deployments in underprivileged areas are primarily single-radio and do operate on a single channel. Frequency
selection in such CWNs is very complex because it does not only determine the nodes’ channel of operation, but also the
gateway and the routing tree to the gateway—a rather computationally intensive task. In this paper, we propose, design,
implement, and evaluate SWARM, a practical system that allows a CWN to make effective use of the available wireless
channels in order to offer globally optimal performance. SWARM improves performance versus current single-channel
protocols by up to 7.7 * in our experiments. Moreover, while we should be expecting performance gains due to channel
diversity, we clearly demonstrate that up to 3.7 improvement is attributed to the network organization into efficient traffic
distribution structures.

63 The Limit of Information Propagation Speed in Large-Scale Multihop Wireless Networks

This paper investigates the speed limit of information propagation in large-scale multihop wireless networks, which
provides fundamental understanding of the fastest information transportation and delivery that a wireless network is able to
accommodate. We show that there exists a unified speed upper bound for broadcast and unicast communications in large-
scale wireless networks. When network connectivity is considered, this speed bound is a function of node density. If the
network noise is constant, the bound is a constant when node density exceeds a threshold; if the network noise is an


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increasing function of node density, the bound decreases to zero when node density approaches infinity. As achieving the
speed bound places strict requirements on node locations, we also quantify the gap between the actual achieved speed and
the desired bound in random networks in which the relay nodes are not located as desired. We find that the gap converges
to zero exponentially as node density increases to infinity.

64 TOFU: Semi-Truthful Online Frequency Allocation Mechanism for Wireless Networks

In wireless networks, we need to allocate spectrum efficiently. One challenge is that the spectrum usage requests often
come in an online fashion. The second challenge is that the secondary users in a cognitive radio network are often selfish
and prefer to maximize their own benefits. In this paper, we address these two challenges by proposing TOFU, a semi-
truthful online frequency allocation method for wireless networks when primary users can sublease the spectrums to
secondary users. In our protocol, secondary users are required to submit the spectrum bid alpha time slots before its
usage. Upon receiving an online spectrum request, our protocol will decide whether to grant its exclusive usage or not,
within at least gamma time slots of requests’ arrival. We assume that existing spectrum usage can be preempted with
some compensation. For various possible known information, we analytically prove that the competitive ratios of our
methods are within small constant factors of the optimum online method. Furthermore, in our mechanisms, no selfish users
will gain benefits by bidding lower than their willing payment. Our extensive simulation results show that they perform
almost optimum: Our methods get a total profit that is more than 95% of the offline optimum when gamma is about the
duration of spectrum usage delta.

65 Topological Transformation Approaches to TCAM-Based Packet Classification

Several range reencoding schemes have been proposed to mitigate the effect of range expansion and the limitations of
small capacity, large power consumption, and high heat generation of ternary content addressable memory (TCAM)-based
packet classification systems. However, they all disregard the semantics of classifiers and therefore miss significant
opportunities for space compression. In this paper, we propose new approaches to range reencoding by taking into
account classifier semantics. Fundamentally different from prior work, we view reencoding as a topological transformation
process from one colored hyperrectangle to another, where the color is the decision associated with a given packet. Stated
another way, we reencode the entire classifier by considering the classifier’s decisions rather than reencode only ranges in
the classifier ignoring the classifier’s decisions as prior work does. We present two orthogonal, yet composable,
reencoding approaches: domain compression and prefix alignment. Our techniques significantly outperform all previous
reencoding techniques. In comparison to prior art, our experimental results show that our techniques achieve at least five
times more space reduction in terms of TCAM space for an encoded classifier and at least three times more space
reduction in terms of TCAM space for a reencoded classifier and its transformers. This, in turn, leads to improved
throughput and decreased power consumption.

66 Towards Realizable, Low-Cost Broadcast Systems for Dynamic Environments

A main design issue in a wireless data broadcasting system is to choose between push-based and pull-based logic: The
former is used as a low-cost solution, while the latter is preferred when performance is of utmost importance. Therefore, the
most significant advantage of a push system is the minimal cost. This fact implies that hardware limitations do exist in the
case of push systems. As a consequence, every related proposed algorithm should primarily be cost-effective. This

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attribute, however, has been overlooked in related research. In this paper, popular broadcast scheduling approaches are
tested from an implementation cost aspect, and the results render them only conditionally realizable. Moreover, a new,
cost-effective, adaptivity oriented schedule constructor is proposed as a realistic, minimal-cost solution.

67 Towards Systematic Design of Enterprise Networks

Enterprise networks are important, with size and complexity even surpassing carrier networks. Yet, the design of enterprise
networks remains ad hoc and poorly understood. In this paper, we show how a systematic design approach can handle two
key areas of enterprise design: virtual local area networks (VLANs) and reachability control. We focus on these tasks given
their complexity, prevalence, and time-consuming nature. Our contributions are threefold. First, we show how these design
tasks may be formulated in terms of network-wide performance, security, and resilience requirements. Our formulations
capture the correctness and feasibility constraints on the design, and they model each task as one of optimizing desired
criteria subject to the constraints. The optimization criteria may further be customized to meet operator-preferred design
strategies. Second, we develop a set of algorithms to solve the problems that we formulate. Third, we demonstrate the
feasibility and value of our systematic design approach through validation on a large-scale campus network with hundreds
of routers and VLANs.

68 Traffic-Oblivious Routing in the Hose Model

Routing traffic subject to hose model constraints has been of much recent research interest. Two-phase routing has been
proposed as a mechanism for routing traffic in the hose model. It has desirable properties in being able to statically
preconfigure the transport network and in being able to handle constraints imposed by specialized service overlays. In this
paper, we investigate whether the desirable properties of two-phase routing come with any resource overhead compared
to: 1) direct source–destination path routing; and 2) optimal scheme among the class of all schemes that are allowed to
even make the routing dynamically dependent on the traffic matrix. In the pursuit of this endeavor, we achieve several
milestones. First, we develop a polynomial-size linear programming (LP) formulation for maximum throughput routing of
hose traffic along direct source–destination paths. Second, we develop a polynomial-size LP formulation for maximum
throughput two-phase routing of hose traffic for a generalized version of the scheme proposed in our previous work. Third,
we develop a polynomial- size LP formulation for minimum-cost two-phase routing of hose traffic for the generalized
version of the scheme. We also give a second (simpler) LP formulation and fast combinatorial algorithm for this problem
using an upper bound on the end-to-end traffic demand. Fourth, we prove that the throughput (and cost) of two-phase
routing is within a factor of 2 of that of the optimal scheme. Using the polynomial-size LP formulations developed, we
compare the throughput of two-phase routing to that of direct source–destination path routing and optimal scheme on
actual Internet service provider topologies collected for the Rocketfuel project and three research network topologies. The
throughput of two-phase routing matches that of direct source–destination path routing and is close to that of the optimal
scheme on all evaluated topologies. We conclude that two-phase routing achieves its robustness to traffic variation without
imposing any appreciable additional resource requirements over previous approaches.

69 Using Link Gradients to Predict the Impact of Network Latency on Multitier Applications

Managing geographically dispersed deployments of complex multitier applications involves dealing with the substantial
effects of network latency. However, the effects of network latency on an application’s end-to-end performance can be far
from obvious, thus making it difficult to predict the true impact of infrastructure changes such as network upgrades or
server relocation on the users of an application. In this paper, we propose a new metric to quantify this impact called the
link gradient. We develop a novel noise-resistant, nonintrusive technique to measure the link gradients in running systems

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without requiring knowledge of the system structure by using a combination of run-time delay injection and spectral
analysis.We evaluate the intrusiveness and accuracy of our approach using micro-benchmarks and a deployment of two
benchmark multitierWeb applications on PlanetLab. Using these results, we show that link gradients can be used to
accurately predict the impact of network latency changes on the end-to-end responsiveness of individual application
transactions, even in new application configurations and without requiring a dedicated test environment.

70 Valuable Detours: Least-Cost Anypath Routing

In many networks, it is less costly to transmit a packet to any node in a set of neighbors than to one specific neighbor. This
observation was previously exploited by opportunistic routing protocols by using single-path routing metrics to assign to
each node a group of candidate relays for a particular destination. This paper addresses the least-cost anypath routing
(LCAR) problem: how to assign a set of candidate relays at each node for a given destination such that the expected cost of
forwarding a packet to the destination is minimized. The key is the following tradeoff: On one hand, increasing the number
of candidate relays decreases the forwarding cost, but on the other, it increases the likelihood of “veering” away from the
shortest-path route. Prior proposals based on single-path routing metrics or geographic coordinates do not explicitly
consider this tradeoff and, as a result, do not always make optimal choices. The LCAR algorithm and its framework are
general and can be applied to a variety of networks and cost models. We show how LCAR can incorporate different aspects
of underlying coordination protocols, for example a link-layer protocol that randomly selects which receiving node will
forward a packet, or the possibility that multiple nodes mistakenly forward a packet. In either case, theLCARalgorithm finds
the optimal choice of candidate relays that takes into account these properties of the link layer. Finally, we apply LCAR to
low-power, low-rate wireless communication and introduce a new wireless link-layer technique to decrease energy
transmission costs in conjunction with anypath routing. Simulations show significant reductions in transmission cost to
opportunistic routing using single-path metrics. Furthermore, LCAR routes are more robust and stable than those based on
single-path distances due to the integrative nature of the LCAR’s route cost metric.


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IEEE Final Year Projects 2011-2012 :: Elysium Technologies Pvt Ltd::Networknew

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