bluuebunny/crossref_metadata_2025 huggingface dataset:
Protection in flexible operating system architectures
Authors: Rippert Christophe
Published: October 2004

This paper presents our work concerning flexibility and protection in operating system kernels. In most existing operating systems, security is enforced at the price of flexibility by imposing protection models on the system programmer when building his system. We prove that flexibility can be preserved by separating the management of the protection policy from the tools used to enforce it. We present the secure software framework we have implemented in the T
HINK
architecture to manage protection policies and guarantee they are carried out as specified. We then detail the elementary protection tools provided to the programmer so he can protect his system against unauthorized accesses and denial of service attacks. These tools are implemented in a policy-neutral way so as to guarantee their flexibility. Finally we validate our results by evaluating the flexibility of the protection provided on selected examples of dynamic modification of the protection policy.
Weaknesses of Lee-Li-Hwang's hash-based password authentication scheme
Authors: Ku Wei-Chi , Chen Chien-Ming , Lee Hui-Lung
Published: October 2004

Many password authentication schemes employ hash functions as their basic building blocks to achieve better efficiency. In 2000, Peyravian and Zunic proposed a hash-based password authentication scheme that is efficient and can be easily implemented. Recently, Lee, Li, and Hwang demonstrated that Peyravian-Zunic's hash-based password authentication scheme is vulnerable to the off-line guessing attack, and then proposed an improved version. In this article, we show that their improved scheme is still vulnerable to the off-line guessing attack, the denial-of-service attack, and the stolen-verifier attack.
ID-based password authentication scheme using smart cards and fingerprints
Authors: Kim Hyun-Sung , Lee Sung-Woon , Yoo Kee-Young
Published: October 2004

This paper proposes two ID-based password authentication schemes, which does not require a dictionary of passwords or verification tables, with smart card and fingerprint. In these schemes, users can change their passwords freely. For a network without synchronization clocks, the proposed nonce-based authentication scheme can withstand message replay attacks. The proposed two schemes require a system to authenticate each user by each user's knowledge, possession, and biometrics, and this feature makes our schemes more reliable.
An authentication scheme for mobile satellite communication systems
Authors: Hwang Min-Shiang , Yang Chao-Chen , Shiu Cheng-Yeh
Published: October 2004

This paper discusses the security aspects of a registration protocol in a mobile satellite communication system. We propose a new mobile user authentication and data encryption scheme for mobile satellite communication systems. The scheme can remedy a replay attack.
A novel packet-pair-based inferring bandwidth congestion control mechanism for layered multicast
Authors: Liyong Ren , Bo Chen , Jing Wu
Published: October 2004

Layered transmission of data is the generally recommended solution to the problem of varying bandwidth constraints and heterogeneity in multicast applications. In this paper, we describe a new multicast congestion control mechanism for layered multicast (PLMCC), which is based on packet-pair inferring bandwidth. In PLMCC, intermediate nodes and receivers infer local available bandwidth accurately and quickly using hop-by-hop downward packet-pair. Compared with PLM introduced by Legout et al., PLMCC eliminates the problem associated with large Internet group management protocol (IGMP) leave latencies, it has faster convergence speed. Moreover, our simulation results show that PLMCC is also TCP-friendly and scalable.
Session summary
Authors: Wellings Andy , Tokar Joyce L.
Published: October 2004

The purpose of this session was to review the Real-Time Specification for Java (RTSJ) and look at the scheduling that Java offers. The discussion focused on the assertion that Java offers a higher-level of abstraction for scheduling than Ada.
Dynamic ceiling priorities in GNAT implementation report
Authors: Miranda Javier , Schonberg Edmond , Masmano Miguel , Real Jorge , Crespo Alfons
Published: October 2004

This document presents the required modifications to the GNAT compiler to support dynamic ceiling priorities in protected objects [1]. In a nutshell, dynamic ceilings for protected objects can be implemented in a simple and efficient manner in the GNAT compiler and run-time.
Managing multiple execution-time timers from a single task
Authors: Harbour Michael González , Rivas Mario Aldea
Published: October 2004

A proposal for adding execution time clocks and timers to the Ada language through a new package called
Ada.Real_Time.Execution_time
is being considered by the ARG. In that proposal, execution time budgets can be managed through protected objects that provide an entry to detect execution time budget overruns. With that interface, a given task can only wait for one budget overrun, thus making it impossible for a single task to manage the execution time budgets of several other tasks. In this paper we propose an extension to the
Execution_Time
package that would allow a monitoring task to manage multiple budgets.
Application-defined scheduling in Ada
Authors: Rivas Mario Aldea , Harbour Michael González
Published: October 2004

This paper is a proposal for an application program interface (API) that would enable Ada applications to use application-defined scheduling algorithms in a way compatible with the scheduling model of the Ada 95 Real-Time Systems Annex. With this API, several application-defined schedulers, implemented by extending a tagged type, can coexist in the system in a predictable way together with their scheduled tasks, and with regular fixed priority tasks directly scheduled by the run-time system. Task synchronization through protected objects is also considered by adding the Stack Resource Policy, which can be used in a large variety of fixed and dynamic priority scheduling policies.
Space & Time Partitioning with ARINC 653 and pragma profile
Authors: Tokar Joyce L.
Published: October 2004

The development of embedded applications is entering into a new domain with the availability of new high-speed processors and low cost on-chip memory. As the result of these new developments in hardware, there is an interest in enabling multiple applications to share a single processor and memory. To facilitate such a model the execution time and memory space of each application must be protected from other applications in the system.The ARINC Specification 653[1] provides the definition of an APplication EXecutive (APEX) that supports space and time partitioning of applications. ARINC 653 systems are composed of software partitions. Each partition is a separate application and there is dedicated memory space for each partition thereby providing space partitioning. Similarly, the APEX provides a dedicated time slice for each partition to support time partitioning. ARINC 653 supports a multitasking environment in each partition through a well-defined set of process communication mechanisms and preemptive priority based scheduling.The availability of a multi-tasking environment within each ARINC 653 partition reduces the need for the use of the Ada process model in the development of applications to execute on top of the ARINC 653 APEX. This paper will presents a proposal for a new profile definition, ARINC_653_Processes, for consideration using the
pragma
Profile
capability of Ada.
Ravenscar design patterns?
Authors: Vardanega Tullio
Published: October 2004

Industrial developers have started to use the Ravenscar Profile in challenging application domains. The thorough feedback that begins to emerge from these experiences is of great interest to the community (i.e. the IRTAW group) that rst conceived and promoted the Pro le. This paper undertkes a rst analysis of a specific experience report to which the author had early and privileged access.
An approach to formal verication of real time concurrent Ada programs
Authors: Howe Douglas J. , Michell Stephen
Published: October 2004

The SPARK system provides static analysis tools for a highly restricted sequential Ada subset, including a proof checking tool for verifying partial correctness properties. Recently, SPARK Ada has been extended to include much of the Ravenscar Tasking Pro le which supports construction of high integrity real time systems. However, the veri cation machinery has not been changed, and can only handle purely sequential properties of the code. This paper sketches an approach to reasoning about the concurrent and real-time aspects that SPARK cannot handle. The approach involves compiling an abstract model of the Ada program that can be embedded in a general purpose theorem prover (e.g. PVS). The compilation makes heavy use of SPARK's existing static analysis tools.
Revisiting IP QoS
Authors: Armitage Grenville J.
Published: October 2004

ACM SIGCOMM 2003 included a number of workshops, including the all-day workshop "Revisiting IP QoS: Why do we care, what have we learned? (RIPQOS)." The goal of RIPQOS was to critique the evolution and deployment of IP quality of service (QoS) mechanisms, from both the research and operational community perspectives. The workshop's name was a challenge to all interested communities to reflect on whether IP QoS has lived up to the hype or whether it is simply misunderstood. The workshop saw 6 papers, 2 short papers, a discussion panel, a range of opinions and lots of questions. This report attempts to capture the essence of our workshop's discussions, presentations and experiences.
Theoretical performance analysis of sliding window link level flow control for a local area network
Authors: Arthurs E. , Chesson G. L. , Stuck B. W.
Published: October 2004

A transmitter sends packets over a local area network to a receiver. The receiver has a finite amount of storage capacity for buffering messages. A
sliding window protocol
is employed to insure all packets are delivered without error in order of arrival. Mean throughput rate and packet delay statistics are studied as a function of model parameters. Simulation data are presented.
Commercial network security—does anyone care?
Authors: Burke Edmund L.
Published: October 2004

Since World War II, the US government has had a comprehensive way to deal with communication security. Under pressure from commercial interests, the government moved in the 70's to make some communication security technology available in the form of the
D
ata
E
ncryption
S
tandard.

DES has been available for some time, yet there is little interest in the marketplace. The lack of interest could stem from unawareness or unconcern with security or from the feeling that data security is not the weak point in the system.

This session will investigate the techniques and vulnerabilities of commercial network security. Panel members will present their experiences with developmental and product activities aimed at providing security in a business environment. The panel will try to stimulate discussion on why there has been no market and what technical characteristics that market should have.
A methodology for the design of reliable communication networks in distributed processing systems
Authors: Besharatian Hossein
Published: October 2004

The combined problem of the communication network design and resource allocation is studied for Distributed Data Processing (DDP) networks. The reliability measure for a distributed data processing system is used in order to enhance network reliability.

A model is proposed to determine an optimal DDP network and to allocate resources that maximize the reliability measure of the network, The model takes into consideration network topology, resource avaliability and channel capacity. It is shown that the model may be represented by a linear programming model.
Analysis of reliable multicast algorithms for local networks
Authors: Mockapetris Paul V.
Published: October 2004

Local networks offer unique opportunities for supporting multicast transmissions. This paper describes and analyzes several families of multicast algorithms for local networks. The algorithms examined provide reliable service by dealing with the effects of transmission errors.
Panel on multimedia computer mail—technical issues and future standards
Authors: Deutsch Debra P. , Forsdick Harry C. , Aceves J. J. Garcia Luna , Naffah Najah , Poggio Andrew , Postel Jonathan B. , White James E. , Kuo Franklin F.
Published: October 2004

A computer-based message system (CBMS) consists of computer facilities that expedite the creation, management, and nonreal time distribution of messages. These systems are increasingly being used for formal and informal communication, supporting the distribution of textual messages. However, nontext media such as voice and graphics are very important for human interaction, and are becoming more and more important in computer system applications. As a result, there is a growing need for the support of media other than text in CBMS.

Before standards for multimedia CBMS can be implemented, there are many technical issues that must be addressed. These range from the design of new mechanisms for the distribution of multimedia mail, to the design of tools needed for editing nontext media. This panel will be discussing issues encountered in the development of multimedia CBMS and an outlook for standards for multimedia computer mail.
A function oriented corporate network
Authors: Wang P. S.-C. , Kimbleton S. R.
Published: October 2004

The ITT/NET is an internal corporate network built to satisfy the distributed programming requirements of ITT technology and engineering communities. This paper describes the network: its goals, its architecture, its operational environment and prototype development activities.

The various issues involved in the construction of a Corporate Network based upon diverse, existing systems and communication methods are described in detail. The architectural and implementation decisions are discussed and justified. The programming process and the methodologies adopted are presented and some conclusions are drawn as to the practicality and usefulness of formal development methods in the context of this particular project.
Enabling conferencing applications on the internet using an overlay muilticast architecture
Authors: Chu Yang , Rao Sanjay , Seshan Srinivasan , Zhang Hui
Published: October 2004

In response to the serious scalability and deployment concerns with IP Multicast, we and other researchers have advocated an alternate architecture for supporting group communication applications over the Internet where all multicast functionality is pushed to the edge. We refer to such an architecture as End System Multicast. While End System Multicast has several potential advantages, a key concern is the performance penalty associated with such a design. While preliminary simulation results conducted in static environments are promising, they have yet to consider the challenging performance requirements of real world applications in a dynamic and heterogeneous Internet environment.In this paper, we explore how Internet environments and application requirements can influence End System Multicast design. We explore these issues in the context of audio and video conferencing: an important class of applications with stringent performance requirements. We conduct an extensive evaluation study of schemes for constructing overlay networks on a wide-area test-bed of about twenty hosts distributed around the Internet. Our results demonstrate that it is important to adapt to both latency and bandwidth while constructing overlays optimized for conferencing applications. Further, when relatively simple techniques are incorporated into current self-organizing protocols to enable dynamic adaptation to latency and bandwidth, the performance benefits are significant. Our results indicate that End System Multicast is a promising architecture for enabling performance-demanding conferencing applications in a dynamic and heterogeneous Internet environment.
Algorithms for provisioning virtual private networks in the hose model
Authors: Kumar Amit , Rastogi Rajeev , Silberschatz Avi , Yener Bulent
Published: October 2004

Virtual Private Networks
(VPNs) provide customers with predictable and secure network connections over a shared network. The recently proposed
hose
model for VPNs allows for greater flexibility since it permits traffic to and from a hose endpoint to be arbitrarily distributed to other endpoints. In this paper, we develop novel algorithms for provisioning VPNs in the hose model. We connect VPN endpoints using a
tree
structure and our algorithms attempt to optimize the total bandwidth reserved on edges of the VPN tree. We show that even for the simple scenario in which network links are assumed to have infinite capacity, the general problem of computing the optimal VPN tree is NP hard. Fortunately, for the special case when the ingress and egress bandwidths for each VPN endpoint are equal, we can devise an algorithm for computing the optimal tree whose time complexity is
O
(
mn
), where
m
and
n
are the number of links and nodes in the network, respectively. We present a novel integer programming formulation for the general VPN tree computation problem (that is, when ingress and egress bandwidths of VPN endpoints are arbitrary) and develop an algorithm that is based on the primal-dual method. Our experimental results with synthetic network graphs indicate that the VPN trees constructed by our proposed algorithms dramatically reduce bandwidth requirements (in many instances, by more than a factor of 2) compared to scenarios in which
Steiner trees
are employed to connect VPN endpoints.
Topology discovery for large ethernet networks
Authors: Lowekamp Bruce , O'Hallaron David , Gross Thomas
Published: October 2004

Accurate network topology information is important for both network management and application performance prediction. Most topology discovery research has focused on wide-area networks and examined topology only at the IP router level, ignoring the need for LAN topology information. Recent work has demonstrated that bridged Ethernet topology can be determined using standard SNMP MIBs; however, these algorithms require each bridge to learn about all other bridges in the network. Our approach to Ethernet topology discovery can determine the connection between a pair of the bridges that share forwarding entries for only three hosts. This minimal knowledge requirement significantly expands the size of the network that can be discovered. We have implemented the new algorithm, and it has accurately determined the topology of several different networks using a variety of hardware and network configurations. Our implementation requires access to only one endpoint to perform the queries needed for topology discovery.
Dynamic behavior of slowly-responsive congestion control algorithms
Authors: Bansal Deepak , Balakrishnan Hari , Floyd Sally , Shenker Scott
Published: October 2004

The recently developed notion of
TCP-compatibility
has led to a number of proposals for alternative congestion control algorithms whose long-term throughput as a function of a steady-state loss rate is similar to that of TCP. Motivated by the needs of some streaming and multicast applications, these algorithms seem poised to take the current TCP-dominated Internet to an Internet where many congestion control algorithms co-exist. An important characteristic of these alternative algorithms is that they are
slowly-responsive
, refraining from reacting as drastically as TCP to a single packet loss.However, the TCP-compatibility criteria explored so far in the literature considers only the static condition of a fixed loss rate. This paper investigates the behavior of slowly-responsive, TCP-compatible congestion control algorithms under more realistic dynamic network conditions, addressing the fundamental question of whether these algorithms are safe to deploy in the public Internet. We study persistent loss rates, long- and short-term fairness properties, bottleneck link utilization, and smoothness of transmission rates.
Informed content delivery across adaptive overlay networks
Authors: Byers John , Considine Jeffrey , Mitzenmacher Michael , Rost Stanislav
Published: October 2004

Overlay networks have emerged as a powerful and highly flexible method for delivering content. We study how to optimize throughput of large transfers across richly connected, adaptive overlay networks, focusing on the potential of collaborative transfers between peers to supplement ongoing downloads. First, we make the case for an erasure-resilient encoding of the content. Using the digital fountain encoding approach, end-hosts can efficiently reconstruct the original content of size $n$ from a subset of any $n$ symbols drawn from a large universe of encoded symbols. Such an approach affords reliability and a substantial degree of application-level flexibility, as it seamlessly accommodates connection migration and parallel transfers while providing resilience to packet loss. However, since the sets of encoded symbols acquired by peers during downloads may overlap substantially, care must be taken to enable them to collaborate effectively. Our main contribution is a collection of useful algorithmic tools for efficient estimation, summarization, and approximate reconciliation of sets of symbols between pairs of collaborating peers, all of which keep message complexity and computation to a minimum. Through simulations and experiments on a prototype implementation, we demonstrate the performance benefits of our informed content delivery mechanisms and how they complement existing overlay network architectures.
Network topology generators
Authors: Tangmunarunkit Hongsuda , Govindan Ramesh , Jamin Sugih , Shenker Scott , Willinger Walter
Published: October 2004

Following the long-held belief that the Internet is hierarchical, the network topology generators most widely used by the Internet research community, Transit-Stub and Tiers, create networks with a deliberately hierarchical structure. However, in 1999 a seminal paper by Faloutsos et al. revealed that the Internet's degree distribution is a power-law. Because the degree distributions produced by the Transit-Stub and Tiers generators are not power-laws, the research community has largely dismissed them as inadequate and proposed new network generators that attempt to generate graphs with power-law degree distributions.Contrary to much of the current literature on network topology generators, this paper starts with the assumption that it is more important for network generators to accurately model the large-scale structure of the Internet (such as its hierarchical structure) than to faithfully imitate its local properties (such as the degree distribution). The purpose of this paper is to determine, using various topology metrics, which network generators better represent this large-scale structure. We find, much to our surprise, that network generators based on the degree distribution more accurately capture the large-scale structure of measured topologies. We then seek an explanation for this result by examining the nature of hierarchy in the Internet more closely; we find that degree-based generators produce a form of hierarchy that closely resembles the loosely hierarchical nature of the Internet.
Traffic matrix estimation
Authors: Medina A. , Taft N. , Salamatian K. , Bhattacharyya S. , Diot C.
Published: October 2004

Very few techniques have been proposed for estimating traffic matrices in the context of Internet traffic. Our work on POP-to-POP traffic matrices (TM) makes two contributions. The primary contribution is the outcome of a detailed comparative evaluation of the three existing techniques. We evaluate these methods with respect to the estimation errors yielded, sensitivity to prior information required and sensitivity to the statistical assumptions they make. We study the impact of characteristics such as path length and the amount of link sharing on the estimation errors. Using actual data from a Tier-1 backbone, we assess the validity of the typical assumptions needed by the TM estimation techniques. The secondary contribution of our work is the proposal of a new direction for TM estimation based on using choice models to model POP fanouts. These models allow us to overcome some of the problems of existing methods because they can incorporate additional data and information about POPs and they enable us to make a fundamentally different kind of modeling assumption. We validate this approach by illustrating that our modeling assumption matches actual Internet data well. Using two initial simple models we provide a proof of concept showing that the incorporation of knowledge of POP features (such as total incoming bytes, number of customers, etc.) can reduce estimation errors. Our proposed approach can be used in conjunction with existing or future methods in that it can be used to generate good priors that serve as inputs to statistical inference techniques.
Route flap damping exacerbates internet routing convergence
Authors: Mao Zhuoqing Morley , Govindan Ramesh , Varghese George , Katz Randy H.
Published: October 2004

Route flap damping is considered to be a widely deployed mechanism in core routers that limits the widespread propagation of unstable BGP routing information. Originally designed to suppress route changes caused by link flaps, flap damping attempts to distinguish persistently unstable routes from routes that occasionally fail. It is considered to be a major contributor to the stability of the Internet routing system.We show in this paper that, surprisingly, route flap damping can significantly exacerbate the convergence times of relatively stable routes. For example, a route to a prefix that is withdrawn exactly once and re-announced can be suppressed for up to an hour (using the current RIPE recommended damping parameters). We show that such abnormal behavior fundamentally arises from the interaction of flap damping with BGP path exploration during route withdrawal. We study this interaction using a simple analytical model and understand the impact of various BGP parameters on its occurrence using simulations. Finally, we outline a preliminary proposal to modify route flap damping scheme that removes the undesired interaction in all the topologies we studied. .
Lightweight network support for scalable end-to-end services
Authors: Calvert Kenneth L. , Griffioen James , Wen Su
Published: October 2004

Some end-to-end network services benefit greatly from network support in terms of utility and scalability. However, when such support is provided through service-specific mechanisms, the proliferation of one-off solutions tend to decrease the robustness of the network over time. Programmable routers, on the other hand, offer generic support for a variety of end-to-end services, but face a different set of challenges with respect to performance, scalability, security, and robustness. Ideally, router-based support for end-to-end services should exhibit the kind of generality, simplicity, scalability, and performance that made the Internet Protocol (IP) so successful. In this paper we present a router-based building block called ephemeral state processing (ESP), which is designed to have IP-like characteristics. ESP allows packets to create and manipulate small amounts of temporary state at routers via short, predefined computations. We discuss the issues involved in the design of such a service and describe three broad classes of problems for which ESP enables robust solutions. We also present performance measurements from a network-processor-based implementation.
On fundamental tradeoffs between delay bounds and computational complexity in packet scheduling algorithms
Authors: Xu Jun , Lipton Richard J.
Published: October 2004

In this work, we clarify, extend and solve an open problem concerning the computational complexity for packet scheduling algorithms to achieve tight end-to-end delay bounds. We first focus on the difference between the time a packet finishes service in a scheduling algorithm and its virtual finish time under a GPS (General Processor Sharing) scheduler, called GPS-
relative delay
. We prove that, under a slightly restrictive but reasonable computational model, the lower bound computational complexity of any scheduling algorithm that guarantees
O
(1) GPS-relative delay bound is Ω (

log
2
n

) (widely believed as a "folklore theorem" but never proved). We also discover that, surprisingly, the complexity lower bound remains the same even if the delay bound is relaxed to
O
(

n
a

) for 0‹
a
⋵1. This implies that the delay-complexity tradeoff curve is "flat" in the "interval" [
O
(1),
O
(
n
)). We later extend both complexity results (for
O
(1) or
O
(

n
a

) delay) to a much stronger computational model. Finally, we show that the same complexity lower bounds are conditionally applicable to guaranteeing tight end-to-end delay bounds. This is done by untangling the relationship between the GPS-relative delay bound and the end-to-end delay bound.
New directions in traffic measurement and accounting
Authors: Estan Cristian , Varghese George
Published: October 2004

Accurate network traffic measurement is required for accounting, bandwidth provisioning and detecting DoS attacks. These applications see the traffic as a collection of flows they need to measure. As link speeds and the number of flows increase, keeping a counter for each flow is too expensive (using SRAM) or slow (using DRAM). The current state-of-the-art methods (Cisco's sampled NetFlow) which log periodically sampled packets are slow, inaccurate and resource-intensive. Previous work showed that at different granularities a small number of "heavy hitters" accounts for a large share of traffic. Our paper introduces a paradigm shift for measurement by concentrating only on large flows --- those above some threshold such as 0.1% of the link capacity.We propose two novel and scalable algorithms for identifying the large flows: sample and hold and multistage filters, which take a constant number of memory references per packet and use a small amount of memory. If $M$ is the available memory, we show analytically that the errors of our new algorithms are proportional to $1/M$; by contrast, the error of an algorithm based on classical sampling is proportional to $1/\sqrtM$, thus providing much less accuracy for the same amount of memory. We also describe further optimizations such as early removal and conservative update that further improve the accuracy of our algorithms, as measured on real traffic traces, by an order of magnitude. Our schemes allow a new form of accounting called threshold accounting in which only flows above a threshold are charged by usage while the rest are charged a fixed fee. Threshold accounting generalizes usage-based and duration based pricing.
Expertise, extraversion and group interaction styles as performance indicators in virtual teams
Authors: Balthazard Pierre , Potter Richard E. , Warren John
Published: October 2004

This study investigates how a personality trait and expertise affect virtual teams interaction, and how that interaction leads to different levels of performance (e.g., solution quality, solution acceptance, cohesion). Teams have been shown to exhibit constructive, aggressive/defensive, or passive/defensive interaction styles that affect communication and thus team performance by facilitating or hindering the exchange of information among group members. These styles reflect an aggregation of the behaviors exhibited by individual team members, which are rooted in their individual personalities. The effects of interaction style on team performance have been well established in face-to-face and virtual teams. Generally, constructive interaction styles produce positive outcomes whereas passive/defensive styles beget negative ones. Aggressive/defensive teams produce solutions that are correlated with the expertise of those that have wrested control of the group but there is often little support for those solutions. The current work explores how different constellations of extraversion and expertise manifest themselves into group interaction styles and, ultimately, outcomes. The study involves 248 professional managers from executive MBA and professional development programs in 63 virtual teams that performed an intellective task. Results show that expertise and extraversion to be curvilinearly related to group interactions and performance, and high levels of extraversion and higher variations in extraversion between team members lead to less constructive and more passive/defensive interaction styles within teams. Results show that although expertise is the best predictor of task performance, it is primarily group interaction styles that predict contextual outcomes (e.g., solution acceptance, cohesion, effectiveness) in virtual teams.
The measurement manifesto
Authors: Varghese George , Estan Cristian
Published: October 2004

Useful measurement data is badly needed to help monitor and control large networks. Current approaches to solving measurement problems often assume minimal support from routers and protocols (e.g., active measurement) or place the entire burden on the router to support heavy-weight mechanisms (e.g., NetFlow). In this paper we argue that the research agenda in measurement must change to consider measurement solutions which enlist the cooperation of routers, protocols, and tools. We believe that the need is so urgent that the deployment issues associated with such holistic solutions can be finessed by cooperation between a few key ISPs and a few key router vendors. If this agenda is accepted, there is a rich vein of technical problems, hitherto considered only from an active measurement perspective, for which there can be new and effective orchestrated solutions. We illustrate this thesis using two examples. Our major example is that of measuring traffic matrices using class counters and class sampling (as opposed to the implementation cost of per-prefix counters, or the errors inherent in tomography). We also provide a smaller example of measuring route stability by modifying route computation. Beyond specific techniques, we hope the guidelines in this paper can provide a focus for discussion among researchers, router vendors, protocol designers, and network operators---the stakeholders in the measurement enterprise.
The cutting EDGE of IP router configuration
Authors: Caldwell Don , Gilbert Anna , Gottlieb Joel , Greenberg Albert , Hjalmtysson Gisli , Rexford Jennifer
Published: October 2004

Human error in configuring routers undermines attempts to provide reliable, predictable end-to-end performance on IP networks. Manual configuration, while expensive and error-prone, is the dominant mode of operation, especially for large enterprise networks. These networks often lack the basic building blocks---an accurate equipment inventory, a debugged initial configuration, and a specification of local configuration policies---to support the holy grail of automation. We argue the
migrating an existing network
to automated configuration is a rich and challenging research problem rooted in data analysis and in the modeling of network protocols and operational practices. We propose a novel,
bottom-up
approach that proceeds in three phases: (i)analysis of configuration data to summarize the existing network state and uncover configuration problems; (ii) data mining to identify the network's local configuration policies and violations of these policies; and ultimately (iii)boot-strapping of a database to drive future configuration changes. The first stage reduces the number of errors, the second normalizes the local policies, and the third prevents new errors and reduces the manpower needed to configure the network. We describe the architecture of our EDGE tool for steps (i) and (ii), and present some examples from our experiences applying the tool to several large enterprise networks.
The dark side of the Web
Authors: Pai Vivek S. , Wang Limin , Park KyoungSoo , Pang Ruoming , Peterson Larry
Published: October 2004

With the advent of large-scale, wide-area networking testbeds, researchers can deploy long-running services that interact with other resources on the Web. While such interaction can easily attract clients and traffic, our experience suggests that projects accepting outside input and interacting with outside resources must carefully consider the avenues for abuse of such services. The CoDeeN Content Distribution Network, deployed on PlanetLab, uses a network of caching Web proxy servers to intelligently distribute and cache requests from a potentially large client population. Due to CoDeeN's non-commerical nature, content is not pushed/advertised by content providers, but instead is pulled by clients who have configured their browsers to use CoDeeN.In effect, CoDeeN is one of the largest "open" proxy networks in the world, and therefore draws unwanted attention from malicious users. This paper discusses our experiences with undersirable traffic on CoDeeN, the mechanisms we developed to curtail it, and the future directions for such work. We believe that this work provides a safe alternative to open proxies and will encourage others to deploy similar systems. Some of the security mechanisms we are developing are suitable for ISPs to deploy on their own networks to detect misbehaving customers before problems arise. Finally, other research projects that allow "open" access to Web resources may face similar situations, and may be able to adopt similar mechanisms.
Opportunistic routing in multi-hop wireless networks
Authors: Biswas Sanjit , Morris Robert
Published: October 2004

This paper describes Extremely Opportunistic Routing (ExOR), a new unicast routing technique for multi-hop wireless networks. ExOR forwards each packet through a sequence of nodes, deferring the choice of each node in the sequence until after the previous node has transmitted the packet on its radio. ExOR then determines which node, of all the nodes that successfully received that transmission, is the node closest to the destination. That closest node transmits the packet. The result is that each hop moves the packet farther (or average) than the hops of the best possible pre-determined route.The ExOR design addresses the challenge of choosing a forwarding node after transmission using a distributed algorithm. First, when a node transmits a packet, it includes in the packet a simple schedule describing the priority order in which the potential receivers should forward the packet. The node computes the schedule based on shared measurements of inter-node delivery rates. ExOR then uses a distributed slotted MAC protocol for acknowledgements to ensure that the receivers agree who the highest priority receiver was.The efficacy of ExOR depends mainly on the rate at which the reception probability falls off with distance. Simulations based on measured radio characteristics [6] suggest that ExOR reduces the total number of transmissions by nearly a factor of two over the best possible pre-determined route.
Decoupling policy from mechanism in Internet routing
Authors: Snoeren Alex C. , Raghavan Barath
Published: October 2004

Routing is a black art in today's Internet. End users and ISPs alike have little control over how their packets are handled outside of their networks, stemming in part from limitations of the current wide-area routing protocol, BGP. We believe that many of these constraints are due to policy-based restrictions on route-exportation. Separating forwarding policy from route discovery would allow users to select among the possibly many inter-AS paths available to them and enable ISPs to more effectively manage the end-to-end behavior of their customers' traffic.As a concrete mechanism for enforcing forwarding policy, we purpose the concept of a network capability that binds together a path request, an accountable resource principal, and an authorizing agent. Network capabilities are central to Platypus, a loose source routing protocol we are designing, which composes network capabilities authorized by multiple ISPs to construct alternative inter-AS routes that can be independently validated and accounted for on the fly.
Unmanaged Internet Protocol
Authors: Ford Bryan
Published: October 2004

Though appropriate for core Internet infrastructure, the Internet Protocol is unsuited to routing within and between emerging ad-hoc edge networks due to its dependence on hierarchical, administratively assigned addresses. Existing ad-hoc routing protocols address the management problem but do not scale to Internet-wide networks. The promise of ubiquitous network computing cannot be fulfilled until we develop an
Unmanaged Internet Protocol
(UIP), a scalable routing protocol that manages itself automatically. UIP must route within and between constantly changing edge networks potentially containing millions or billions of nodes, and must still function within edge networks disconnected from the main Internet, all without imposing the administrative burden of hierarchical address assignment. Such a protocol appears challenging but feasible. We propose an architecture based on self-certifying, cryptographic node identifies and a routing algorithm adapted from distributed hash tables.
A case for run-time adaptation in packet processing systems
Authors: Kokku Ravi , Riché Taylor L. , Kunze Aaron , Mudigonda Jayaram , Jason Jamie , Vin Harrick M.
Published: October 2004

Most packet processing applications receive and process multiple types of packets. Today, the processors available within packet processing systems are allocated to packet types at design time. In this paper, we explore the benefits and challenges of adapting allocations of processors to packet types in packet processing systems. We demonstrate that, for all the applications and traces considered, run-time adaptation can reduce energy consumption by 70--80% and processor provisioning level by 40--50%. The adaptation benefits are maximized if processor allocations can be adapted at fine time-scales and if the total available processing power can be allocated to packet types in small granularities. We show that, of these two factors, allocating processing power to packet types is small granularity is more important---if the allocation granularity is large, then even a very fine adaptation time-scale yields meager benefits.
A constraint satisfaction approach to testbed embedding services
Authors: Considine Jeffrey , Byers John W. , Meyer-Patel Ketan
Published: October 2004

Today's networking community is becoming increasingly skeptical of the significance of research results founded wholly upon experimental results conducted in simulation. Now, with the availability of wide-area distributed testbeds such as PlanetLab, it is feasible to move beyond evaluation by simulation, and to perform wide-area experiments across the Internet as an alternate. However, while use of a distributed testbed affords much greater realism than a network simulation, there is a significant downside, as tight control over one's experiments is relinquished.We argue that providing services for distributed testbeds that capture aspects of the specifiable, repeatable behavior implicit in simulation and emulation will be an integral component of next-generation textbeds. As a case study, we consider the following problem: given a desired end-system topology consisting of a set of pairwise constraints (such as upper and lower bounds on bandwidth and delay), locate a representative subtopology within a wide-area testbed that satisfies those constraints. Previous work on Netbed addresses wide-area embedding problems of this form using an optimization framework, whereas we employ constraint satisfaction. We discuss the relative merits of these approaches, outline the theoretical foundations of a distributed service that provides a synergy between adaptive network measurements and the embedding process, and report on preliminary experimental results conducted on PlanetLab.
Addressing reality
Authors: Clark David D. , Sollins Karen , Wroclawski John , Faber Ted
Published: October 2004

A system as complex as the Internet can only be designed effectively if it is based on a core set of design principles, or tenets, that identify points in the architecture where there must be common understanding and agreement. The tenets of the original Internet architecture [6] arose as a response to the technical, governmental, and societal environment of internetworking's earliest days, but have remained central to the Internet as it has evolved. In light of the increasing integration of the Internet into the social, economic, and political aspects of our lives, it is worth revisiting the underlying tenets of what is becoming a central element of the world's infrastructure.This paper examines three key tenets that we believe should guide the evolution of the Internet in its next generation and beyond. They are: design for change, controlled transparency, and the centrality of the tussle space. [8] Our purpose is not to present these ideas as new, but rather to propose that they should be elevated to central tenets of the evolving architecture of the Internet, and explore the ramifications of doing so. The paper first examines the tenets somewhat abstractly, and then in more detail by studying their relation to several design choices needed for a complete architecture. We conclude with a discussion of the relationship between the network architecture and the applications it serves.
Plutarch
Authors: Crowcroft Jon , Hand Steven , Mortier Richard , Roscoe Timothy , Warfield Andrew
Published: October 2004

It is widely accepted that the current Internet architecture is insufficient for the future: problems such as address space scarcity, mobility and non-universal connectivity are already with us, and stand to be exacerbated by the explosion of wireless, ad-hoc and sensor networks. Furthermore, it is far from clear that the ubiquitous use of standard transport and name resolution protocols will remain practicable or even desirable.In this paper we propose
Plutarch
, a new inter-networking architecture. It subsumes existing architectures such as that determined by the Internet Protocol suite, but makes explicit the heterogeneity that contemporary inter-networking schemes attempt to mask. To handle this heterogeneity, we introduce the notions of
context
and
interstitial function
, and describe a supporting architecture. We discuss the benefits, present some potential scenarios, and consider the research challenges posed.