1,720,993 research outputs found
A scalable and error-tolerant solution for traffic matrix assessment in hybrid IP/SDN networks
Full text linkThe advent of the Software Defined Networking (SDN) paradigm represents a great opportunity for the definition of new network management solutions. In this work, we focus on the definition and implementation of a novel technique to solve the Traffic Matrix Assessment (TMA) problem from the perspective of an Internet Service Provider. Since the migration from legacy IP networks to fully-deployed SDN ones needs to be incremental due to budget and technical constraints, this paper proposes a mixed measurement and estimation scalable solution for hybrid IP/SDN networks to accurately solve the TMA problem by exploiting the availability of flow rule counters in SDN switches. The performance evaluation shows that our error-Tolerant solution is able to assess the TM with a negligible estimation error by only measuring a small percentage of traffic flows, overcoming other state-of-The-Art algorithms proposed in the literature. Moreover, the performance analysis of the proposed implementation using the OpenDaylight controller over an emulated network environment, shows that a trade-off between the quality of the assessed TM and its impact on the network in terms of control messages can be found by properly tuning the number of measured flows
Reducing the reconfiguration cost of flow tables in energy-efficient Software-Defined Networks
No full textSoftware-Defined Networking (SDN) is a new networking paradigm that is attracting the attention of the research community due to the flexibility provided by the separation between data and control planes. In particular, the SDN scenario introduces new aspects to be considered when formulating the energy-aware routing problem, such as the reconfiguration cost of flow tables. In this paper we introduce and investigate the problem of minimizing the power consumption of an SDN network while also reducing the number of rules that have to be modified in the flow tables of SDN nodes. An optimization problem formulation and a GA (Genetic Algorithm) based heuristic are presented to tackle this two-fold problem. The performance analysis, carried out over different realistic network topologies, highlights that GA is able to increase the power saving opportunities up to the 20% more than other energy-aware routing solutions proposed in the literature, while reducing the number of rules that have to be modified up to 100 times
A theoretical framework for network monitoring exploiting segment routing counters
Full text linkSelf-driving networks represent the next step of network management techniques in the close future. A fundamental point for such an evolution is the use of Machine Learning based solutions to extract information from data coming from network devices during their activity. In this work we focus on a new type of data, available thanks to the definition of the novel SRv6 paradigm, referred to as SRv6 Traffic Counters (SRTCs). SRTCs provide aggregated measurements related to forwarding operations performed by SRv6 routers. In this work a detailed description of different SRTCs types (SR.INT, PISD, PSID.TM and POL) is provided and their relationships is formalized. The theoretical framework deployed is used to identify, on the basis of network configuration parameters of both SRv6 and IGP protocols, the minimum set of independent SRTCs to characterize the Network Status: we show that about the 80% of counters can be neglected with no information loss. We also apply our framework to two use cases: i) Traffic Matrix (TM) Assessment and ii) Traffic Anomaly Detection. For the TM assessment, we show that in a partially deployed SRv6 scenario a specific type of SRTCs, i.e., PSID, is more reliable than other ones; on the contrary, in a fully deployed scenario POL and PSID.TM counters provide the full TM knowledge. For the Traffic Anomaly Detection case, we show that known solutions based on link load measurements can be improved when integrating SRTCs information
Lifetime-aware cloud data centers: Models and performance evaluation
No full textWe present a model to evaluate the server lifetime in cloud data centers (DCs). In particular, when the server power level is decreased, the failure rate tends to be reduced as a consequence of the limited number of components powered on. However, the variation between the different power states triggers a failure rate increase. We therefore consider these two effects in a server lifetime model, subject to an energy-aware management policy. We then evaluate our model in a realistic case study. Our results show that the impact on the server lifetime is far from negligible. As a consequence, we argue that a lifetime-aware approach should be pursued to decide how and when to apply a power state change to a server
A heuristic approach to assess the traffic matrix of an ISP exploiting segment routing flexibility
No full textThe Ingress Egress Traffic Matrix (IE TM) assessment is a fundamental step of the network management for an ISP network, since it represents the key input parameter used by any Traffic Engineering solution to optimize the resource utilization and to improve the Quality of Service. The actual TM assessment procedures are based on estimation algorithms or measurement based approaches. This paper presents a method to measure the intensity of traffic flows, that overcomes the limits of the classical measurement/estimation based approaches. The idea is to exploit the flexibility of the Segment Routing paradigm to implement controlled routing changes so that to measure the intensity of a subset of network flows. The main contribution of the work is to show the feasibility of the proposed approach by means of a low complexity heuristic, referred to as Path Cost Bases (PaCoB), able to identify the list of routing changes that allow to improve the TM assessment procedure. The heuristic is composed of successive steps, referred to as snapshots: in each snapshot the routing of a set of flows is changed so that to assess their intensities. The performance evaluation show thatPaCoB assesses the intensity of more than 90% of flows. Moreover, when used in conjunction with an estimation algorithm, PaCoB allows to reduce the estimation error by more than 50% performing only 10 snapshots
Interface counters in segment routing v6: a powerful instrument for traffic matrix assessment
No full textIn this work we investigate the use of Segment Routing version 6 (SRv6) interface counters to improve the Traffic Matrix (TM) assessment of an ISP network. SRv6 is a source routing solution for IPv6 networks: it allows defining a network path as a sequence of routers, represented by Segments Identifiers (SID), to be crossed, i.e. a Segment List (SL). SRv6 provides a new set of interface counters able to measure the packets/ bytes of Ingress/Egress flows exploiting the forwarding operations performed on the Segment Identifiers (SIDs) reported in the SLs. In this work, we formally define the contribution of SR counters in the TM computation procedure, by integrating them in the classical TM Assessment problem. The main outcome of the performance analysis are: i) SR counters can greatly reduce the estimation error and, ii) there is a correlation between the TM assessment improvement and the SLs structure
Snoop Through Traffic Counters to Detect Black Holes in Segment Routing Networks
No full textThe new Segment Routing paradigm provides network operator the possibility of highly increasing network performance exploiting advanced Traffic Engineering features and novel network programability functions. Anyway, as any new solutions, SRv6 has a side effect: the introduction of unknown service disruption events. In this work we focus on packet lost events due to the incorrect computation of the Maximum Transmission Unit (MTU) value of an end-to-end path in an SRv6 network. This event, referred to as MTU dependent SR Black Hole, cannot be detected by known monitoring solutions based on active probing: the reason is that in SRv6 probe packets and user data can experience different network behaviors. In this work we propose a passive monitoring solution able to exploit the SRv6 Traffic Counters to detect links where packets are lost due to MTU issues. The performance evaluation shows that the algorithm proposed is able to identify the link affected by the blackhole with a precision equal to 100 % ; moreover, the flow causing the blackhole cannot be detected with the same precision, but it is possible to identify a restricted set of flows, referred to as suspected flows, containing the target one
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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