Unconvinced, Unreconstructed, and Unrepentant: A Reply to Professor Friedman’s Response

Software defined networks are poised to dramatically simplify deployment and management of networks. OpenFlow, in particular, is becoming popular and starts being deployed. While the definition of the “northbound” API that can be used by the new services to interact with an OpenFlow controller is receiving considerable attention, the traditional, “southbound”, API that is used to program OpenFlow switches is far from perfect. In this paper, we analyze the current OpenFlow API and its usage in several controllers and show semantic differences between the intended and actual use. Thus, we argue for making the OpenFlow API clean and simple. In particular, we propose to mimic the process that exists in the Python community for deriving changes that result in a preferably only one, obvious way of performing a task. Toward this end, we propose three OpenFlow Enhancement Proposals: i) providing positive acknowledgment, ii) informing the controller about “silent” modifications, and iii) providing a partial order synchronization primitive.QC 20150704</p

The American Commitment to Private International Political Communications: A View of Free Europe, Inc.

The principal service of distributed hash tables (DHTs) is route(id, data), which sends data to a peer responsible for id, using typically O(log(# of peers)) overlay hops. Certain applications like peer-to-peer information retrieval generate billions of small messages that are concurrently inserted into a DHT. These applications can generate messages faster than the DHT can process them. To support such demanding applications, a DHT needs a congestion control mechanism to efficiently handle high loads of messages. In this paper we provide an extended study on congestion control for DHTs: we present a theoretical analysis that demonstrates that congestion control for DHTs is absolutely necessary for applications that provide elastic traffic. We then present a new congestion control algorithm for DHTs. We provide extensive live evaluations in a ModelNet cluster and the PlanetLab test bed, which show that our algorithm is nearly loss-free, fair, and provides low lookup times and high throughput under cross-load.QC 20140707</p

Consequences of Compliance and Deterrence Models of Law Enforcement for the Exercise of Police Discretion

The Internet is suffering from ossification. There has been substantial research on improving current protocols, but the vendors are reluctant to deploy new ones. We believe that this is in part due to the difficulty of evaluating protocols under realistic conditions. Recent wide-area testbeds can help alleviate this problem, but they require substantial resources (equipment, bandwidth) from each participant, and they have difficulty in providing repeatability and full control over the experiments. Existing in-house networking testbeds are capable of running controlled, repeatable experiments, but are typically small-scale (due to various overheads), limited in features, or expensive. The premise of our work is that it is possible to leverage the recent increases in computational power to improve the researchers' ability to experiment with new protocols in lab settings. We propose a cost-effective testbed, called MX, which emulates many programmable routers running over a realistic topology on multi-core commodity servers. We leverage open source implementations of programmable routers, such as Click, and modify them to allow coexistence of multiple instances in the same kernel in an effort to reduce packet forwarding overheads. Our initial results show that we outperform similar cost-effective solutions by a factor of 2. Next, we demonstrate that grouping and placing routers on to cores which share the L2 cache yields high performance.QC 20140707</p

The United Nations and the Human Rights Issue

This paper demonstrates a new class of bugs that is likely to occur in enterprise OpenFlow deployments. In particular, step-by-step, reactive establishment of paths can cause network-wide inconsistencies or performance- and space-related inefficiencies. The cause for this behavior is inconsistent packet processing: as the packets travel through the network they do not encounter consistent state at the OpenFlow controller. To mitigate this problem, we propose to use transactional semantics at the controller to achieve consistent packet processing. We detail the challenges in achieving this goal (including the inability to directly apply database techniques), as well as a potentially promising approach. In particular, we envision the use of multi-commit transactions that could provide the necessary serialization and isolation properties without excessively reducing network performance.QC 20140707</p

The new face of East-West migration in Europe

In order to contextualise the papers in this special issue, this paper presents an overview and framework for understanding the importance of East–West migration in Europe associated with the EU enlargement process. The new patterns and forms of migration seen among East European migrants in the West—in terms of circular and temporary free movement, informal labour market incorporation, cultures of migration, transnational networks, and other phenomena documented in the following papers—illustrate the emergence of a new migration system in Europe. Textbook narratives, in terms of standard accounts of immigration, integration and citizenship based on models of post-colonial, guestworker and asylum migration, will need to be rethought. One particularly fertile source for this is the large body of theory and research developed in the study of Mexican–US migration, itself a part of a regional integration process of comparative relevance to the new European context. While the benefits of open migration from the East will likely triumph over populist political hostility, it is a system that may encourage an exploitative dual labour market for Eastern movers working in the West, as well as encouraging a more effective racial or ethnically-based closure to immigrants from South of the Mediterranean and further afield

Foreword: The Nature of Discretion

Power consumption has become a critical issue in large scale clusters. Existing solutions for addressing the servers’ energy consumption suggest “shrinking” the set of active machines, at least until the more power-proport-ional hardware devices become available. This paper demonstrates that leveraging the sleeping state, however, may lead to unacceptably poor performance and low data availability if the distributed services are not aware of the power management’s actions. Therefore, we present an architecture for cluster services in which the deployed services overcome this problem by actively participating in any action taken by the power management. We propose, implement, and evaluate modifications for the Hadoop Distributed File System and the MapReduce clone that make them capable of operating efficiently under limited power budgets.QC 20140707</p

Is the Network Turing-Complete?

Ensuring correct network behavior is hard. This is the case even for simple networks, and adding middleboxes only complicates this task. In this paper, we demonstrate a fundamental property of networks. Namely, we show a way of using a network to emulate the Rule 110 cellular automaton. We do so using just a set of network devices with simple features such as packet matching, header rewriting and round-robin loadbalancing. Therefore, we show that a network can emulate any Turing machine. This ultimately means that analyzing dynamic network behavior can be as hard as analyzing an arbitrary program. Analyzing a network containing middleboxes is already understood to be hard. Our result shows that using even only statically configured switches can make the problem intractable

Online Testing of Federated and Heterogeneous Distributed Systems

DiCE is a system for online testing of federated and heterogeneous distributed systems. We have built a prototype of DiCE and integrated it with a BGP router. DiCE quickly detects three important classes of faults, resulting from configuration mistakes, policy conflicts and programming errors

Insulin resistance in drug naive patients with multiple sclerosis

Background/Aim. Due to the fact that there is a relatively small number of data related to systemic insulin abnormalities in the multiple sclerosis (MS), the main objective of our study was to determine whether a dysbalance of glucose and insulin metabolism exist in patients with natural course of MS. Our hypothesis was that the metabolic disorder that characterizes state of the insulin resistance (IR) and reduced insulin sensitivity (IS) in untreated patients with MS could play a role in disease progression and degree of functional disability. Methods. The study included 31 patients with relapsing-remitting (RR) MS and 14 healthy controls from the same geographic area matched by age, ethnicity and number of smokers. The glucose tolerance, IS, and IR were examined using an oral glucose tolerance test (OGTT) and using basal plasma glucose and insulin levels. The functional disability and disease progression were evaluated by the Expanded Disability Status Scale (EDSS) and Multiple Sclerosis Severity Score (MSSS). Results. The MS patients tolerated glucose equally well as the healthy controls. Basal concentrations of insulin were significantly higher in the MS group p LT 0.05), as well as insulin plasma level 30 min after oral glucose load (p LT 0.01). The patients with MS had significantly higher values of homeostasis model assessment indexes of IR (HOMA-IR) (p = 0.027; p = 0.028). The percentage of IS (HOMA2 % S) and whole body IS index (ISI Matsuda) showed significantly lower values in the MS patients than in the controls (p = 0.005; p = 0.001). The insulinogenic index in the first 30 min of OGTT was significantly higher in MS patients (p = 0.005). The measures of functional disability and MS progression did not correlate significantly with the investigated parameters of IR and IS indexes. Conclusion. This study demonstrates for the first time the existence of hyperinsulinemia, reduced insulin sensitivity and normal glucose tolerance that indicate the initial phase of IR in the natural course of MS. Additional research is necessary in order to define the mechanisms of occurrence and the impact of IR on the complex pathophysiological processes in MS