Siemens has wide ranging experience in global development. Corporate development centers located in different geographical areas define their own processes to deal with the challenges in their respective location. It is to be understood that there is no "true globalization" in any business. From previous studies of managing offshore centers for product development, one expects that there is an amount of localization which comes in to play in projects when compared to the organization as a whole. This paper is an effort to describe how we achieve and sustain high performance effectively, in a globally distributed development, considering some of the main parameters of localization, where interaction among Germany, India, Hungary and China is involved. We describe some key practices that enable our offshore team to achieve and sustain high performance. We also show the value addition done by the offshore team along with awards, recognition, and ratings received that makes it a success story.

Distributed software development is a globally accepted practice by large organizations for achieving significant cost savings in research and development. However when it comes to product quality, defect prevention and early detection has always been a challenge. Factors such as differences in language, coding standards and documentation styles across distributed teams can aggravate the situation. These issues, if not addressed, will manifest themselves as product defects leading to enormous costs in fixing at later phases of development. This in turn reduces the business partner or product owner's confidence. Thus, along with defining effective processes to address these issues, it becomes very important to ensure that the product quality expectations of various stakeholders are understood and mutually agreed upon. This paper summarizes our approach and practice in managing these issues while also delivering the expected product quality in our recent project.

We present CPM, a unified approach that exploits server multicast, assisted by peer downloads, to provide efficient video-on-demand (VoD) in a service provider environment. We describe our architecture and show how CPM is designed to dynamically adapt to a wide range of situations including highly different peer-upload bandwidths, content popularity, user request arrival patterns, video library size, and subscriber population. We demonstrate the effectiveness of CPM using simulations (based on an actual implementation codebase) across the range of situations described above and show that CPM does significantly better than traditional unicast, different forms of multicast, as well as peer-to-peer schemes. Along with synthetic parameters, we augment our experiments using data from a deployed VoD service to evaluate the performance of CPM.

In this paper, we present an algorithm for intra-domain traffic engineering. We assume that the traffic matrix, which specifies traffic load between every source-destination pair in the network, is unknown and varies with time, but that always lies inside an explicitly defined region. Our goal is to compute a fixed robust routing with best worst case performance for all traffic matrices inside the bounding region. We formulate this problem as a semi-infinite programming problem. Then, we focus on a special case with practical merits, where (1) the traffic matrix region is assumed to be a polytope specified by a finite set of linear inequalities, and (2) our objective is to find the routing that minimizes the maximum link utilization. Under these assumptions, the problem can be formulated as a polynomial size linear programming (LP) problem with finite number of constraints. We further consider two specific set of constraints for the traffic matrix region. The first set is based on the hose model and limits the total traffic rate of network point of presence (PoP) nodes. The second set is based on the pipe model and limits the traffic between source-destination pairs. We study the effectiveness of each set of constraints using extensive simulations.

We propose a new architecture for efficient network monitoring and measurements in a traditional IP network. This new architecture enables establishment of multiple paths (tunnels) between source-destination pairs without having to modify the underlying routing protocol(s). Based on the proposed architecture we propose a measurement-based multipath routing algorithm derived from simultaneous perturbation stochastic approximation. The proposed algorithm does not assume that the gradient of analytical cost function is known to the algorithm, but rather relies on noisy estimates from measurements. Using the analytical model presented in the paper we prove the convergence of the algorithm to the optimal solution. Simulation results are presented to demonstrate the advantages of the proposed algorithm under a variety of network scenarios. A comparative study with an existing optimal routing algorithm, MATE, is also provided.

We propose a multi-hop wireless LAN architecture and demonstrate its benefits to wireless clients. For this architecture, we define implementation paths that allow interoperation with existing wireless LANs which can lead to an incremental deployment of this system. We quantify the performance benefits of the proposed schemes through measurements in realistic wireless LAN environments. We also examine the performance of such multi-hop wireless LANs through detailed simulation studies. Our results show that these multi-hop extensions can significantly improve the wireless access experience (in terms of data throughput, latency, etc.) for clients who enable such mechanisms. More interestingly, when multi-hop extensions are enabled by some of the clients, it also positively impacts the performance at other clients that are completely unaware of these extensions.

We describe a method for performing trust-preserving set operations by untrusted parties. Our motivation for this is the problem of securely reusing content-based search results in peer-to-peer networks. We model search results and indexes as data sets. Such sets have value for answering a new query only if they are trusted. In the absence of any system-wide security mechanism, a data set is trusted by a node a only if it was generated by some node which is trusted by a. Our main contributions are a formal definition of the problem as well as an efficient scheme that solves this problem by allowing untrusted peers to perform set operations on trusted data sets while also producing unforgeable proofs of correctness. This is accomplished by requiring trusted nodes to sign appropriately-defined digests of generated sets; each such digest consists of an RSA accumulator and a Bloom filter. The scheme is general, and has other applications as well. We give an analysis demonstrating the low overhead of the scheme, and we include experimental data which confirm the analysis.

This paper presents an overlay architecture where service providers deploy a set of service nodes (called MSNs) in the network to efficiently implement media-streaming applications. These MSNs are organized into an overlay and act as application-layer multicast forwarding entities for a set of clients. We present a decentralized scheme that organizes the MSNs into an appropriate overlay structure that is particularly beneficial for real-time applications. We formulate our optimization criterion as a "degree-constrained minimum average-latency problem" which is known to be NP-hard. A key feature of this formulation is that it gives a dynamic priority to different MSNs based on the size of its service set. Our proposed approach iteratively modifies the overlay tree using localized transformations to adapt with changing distribution of MSNs, clients, as well as network conditions. We show that a centralized greedy approach to this problem does not perform quite as well, while our distributed iterative scheme efficiently converges to near-optimal solutions.

A distributed scheme for trust inference in peer-to-peer networks is presented. Our work is in context of the NICE system, which is a platform for implementing cooperative applications over the Internet. We describe a technique for efficiently storing user reputation information in a completely decentralized manner, and show how this information can be used to efficiently identify noncooperative users in NICE. We present a simulation based study of our algorithms, in which we show our scheme scales to thousands of users using modest amounts of storage, processing, and bandwidth at any individual node. Lastly, we show that our scheme is robust and can form cooperative groups in systems where the vast majority of users are malicious.

Bowman is an extensible platform for active networking: it layers active networking functionality in user space software over variants of the System V UNIX operating system. The packet processing path implemented in Bowman incorporates an efficient and flexible packet classification algorithm, supports multi-threaded per-flow processing, and utilizes real time processor scheduling to achieve deterministic performance in the user-space. In this paper we describe the design and implementation of Bowman; discuss the support that Bowman provides for implementing execution environments for active networking; discuss the network-level architecture of Bowman that can be used to implement virtual networks; and present performance data showing that Bowman is able to sustain 100 Mbps throughput while forwarding IP packets over fast Ethernets.

Server replication improves the ability of a service to handle a large number of clients. One of the important factors in the efficient utilization of replicated servers is the ability to direct client requests to the "best" server, according to some optimality criteria. In the anycasting communication paradigm, a sender communicates with a receiver chosen from an anycast group of equivalent receivers. As such, anycasting is well suited to the problem of directing clients to replicated servers. This paper examines the definition and support of the anycasting paradigm at the application-layer, providing a service that uses an anycast resolver to map an anycast domain name and a selection criteria into an IP address. By realizing anycasting in the application-layer, we achieve flexibility in the optimization criteria and ease the deployment of the service. As a case study, we examine the performance of our system for a key service: replicated Web servers. To this end, we develop an approach for estimating the response time that a client will experience when accessing given servers. Such information is maintained in the anycast resolver that clients query to obtain the identity of the server with the best estimated response time. Our performance collection technique combines server push with resolver probes to estimate the expected response time without undue overhead. Our experiments show that selecting a server using our architecture and estimation technique can improve the client response time by a factor of two over nearest server selection and by a factor of four over random server selection.

Control-on-demand is a paradigm for network programmability at the network transport level. Prior work on active and programmable networking at this level either achieves flexibility by inserting significant software in the critical path of forwarding or achieves efficiency by sacrificing functionality and relegating programmability to connection management. In contrast, control-on-demand acts both in the control plane and in the data plane, still without adding software in the critical forwarding path. Rather than applying essential programs to every datagram, our approach is to apply the installed service logic asynchronously from data forwarding. This way we avoid essential processing in the critical forwarding path, applying the (user) installed service logic for service enhancement only. In this paper, we describe control-on-demand and how its service model provides sufficient richness to act in the data path. Set is restrictive enough to avoid the significant performance overhead of other in-data path approaches. The expressiveness of the programmable model is limited to observing and suggesting to the forwarding engine, but is never essential for correct processing, thus significantly reducing security and robustness concerns. Consequently, control-on-demand is efficient enough to make it viable for elementary services. Rather than replacing the interoperability layer, control-on-demand represents an evolution of router (switch) control functionality. As the required modification of router forwarding engines is insignificant, control-on-demand is viable in practice in the near future. These concepts have been prototyped as part of the Pronto Control Platform. In this paper, we describe our IPv6 router prototype implementation and discuss the application of control-on-demand on a number of interesting problems.

Active networks allow users to "program" the network infrastructure, by injecting information that describes or controls a distributed algorithm to be executed for the user by the network infrastructure. The nature of the services that can be implemented with such a facility is determined by the programming interface to the active network, i.e. the set of abstractions it exposes to users. The complexity of this interface may range from a few simple parameters to a completely general programming language. We present a model that supports reasoning independently about the correctness of both the underlying active network platform and the algorithms injected into it, in a manner that admits the full range of possible programming interfaces. The model is described without relying on any particular formalism. The interaction between the underlying platform and the user injected program is captured in a specialized form of program composition that allows properties of each to be preserved. The use of the model is illustrated via an example dealing with mobility. For the example, we use the UNITY formalism to be more precise about the programs and properties that are preserved.

A substantial fraction of all network traffic today comes from applications in which clients retrieve objects from servers. The caching of objects in locations "close" to clients is an important technique for reducing both network traffic and response time for such applications. In this paper we consider the benefits of associating caches with switching nodes throughout the network, rather than in a few locations. We also consider the use of various self-organizing or active cache management strategies for organizing cache content. We evaluate caching techniques using both simulation and a general analytic model for network caching. Our results indicate that in-network caching can make effective use of cache space, and in many cases self-organizing caching schemes yield better average round-trip latencies than traditional approaches, using much smaller per-node caches.

Server replication is an approach often used to improve the ability of a service to handle a large number of clients. One of the important factors in the efficient utilization of replicated servers is the ability to direct client requests to the best server, according to some optimality criteria. In this paper we target an environment in which servers are distributed across the Internet, and clients identify servers using our application-layer any-casting service. Our goal is to allocate servers to clients in a way that minimizes a client's response time. To that end, we develop an approach for estimating the performance that a client would experience when accessing particular servers. Such information is maintained in a resolver that clients can query to obtain the identity of the server with the best response time. Our performance collection technique combines server push with client probes to estimate the expected response time. A set of experiments is used to demonstrate the properties of our performance determination approach and to show its advantages when used within the application-layer anycasting architecture.

Active networking is the placement of user-controllable computing functionality in the switching nodes of a network. The end-to-end argument states that functions should be placed "in" the network only if they can be cost-effectively implemented there. We argue that active networking is a natural consequence of the end-to-end argument, because certain functions can be most effectively implemented with information that is only available inside the network. We propose a performance model for quantifying the benefit of implementing a particular functionality solely in the end system versus implementing it through a combination of end system and network support. We show how the model applies to specific services, including congestion control and reliable multicast.

The anycasting communication paradigm is designed to support server replication by allowing applications to easily select and communicate with the "best" server, according to some performance or policy criteria, in a group of content-equivalent servers. We examine the definition and support of the anycasting paradigm at the application layer, providing a service that maps anycast domain names into one or more IP addresses using anycast resolvers. In addition to being independent from network-layer support, our definition includes the notion of filters, functions that are applied to groups of addresses to affect the selection process. We consider both metric-based filters (e.g., server response time) and policy-based filters.

Graphs are commonly used to model the structure of internetworks, for the study of problems ranging from routing to resource reservation. A variety of graph models are found in the literature, including regular topologies such as rings or stars, "well-known" topologies such as the original ARPAnet, and randomly generated topologies. Less common is any discussion of how closely these models correlate with real network topologies. We consider the problem of efficiently generating graph models that accurately reflect the topological properties of real internetworks. We compare the properties of graphs generated using various methods with those of real internets. We also propose efficient methods for generating topologies with particular properties, including a transit-stub model that correlates well with the internet structure. Improved models for the internetwork structure have the potential to impact the significance of simulation studies of internetworking solutions, providing a basis for the validity of the conclusions.