1,720,981 research outputs found
A software-defined 5G cellular network with links virtually pooled for public safety operators
No full textDuring disaster relief operations, public safety personnel performs data communication almost exclusively through terrestrial
commercial networks. However, common cellular infrastructures are often unable to provide acceptable throughput
and even basic availability owing to congestion or infrastructural disruption. In order to overcome these issues, this paper
proposes the implementation of a network abstraction that we define as virtual resource pooling. This allows to virtually
pool the resources provided by the cellular channels on which field operators are connected. The proposal aims to harmoniously
blend together the multihoming capabilities of modern devices and their collaborative potential by leveraging
the software-defined networking facilities that are expected to be present in the core infrastructures of fifth-generation
networks. Coupled with the envisioned performance and packet core plasticity of the latter, such a system may have the
potential to provide future public safety operators with broadband capabilities and high quality of experience in day-to-day
tasks and major planned events while providing improved communication guarantees in unplanned disasters. To experimentally
assess our proposal, we present a test bed that has been built and used to perform network emulation runs and
to extract their results. These indicate that a system with virtual resource pooling may greatly enhance not only throughput
and quality of service properties but also the resilience guarantees that network tenants may offer to field operators
A Congestion Control Middleware Layer with Dynamic Bandwidth Management for Satellite Communications
No full textHistorically, satellites have been set aside for what regards Internet connectivity; however, the interest in their usage to provide Internet connectivity is now rising again. Because of the growing demand for Internet services around the world, satellites can be an effective medium to serve scarcely populated areas as well as missioncritical communications. While the standard transmission control protocol (TCP) performs badly when employed on satellite links for the high propagation delay, when a number of client hosts are wirelessly connected to a gateway that forwards and receives traffic across such links, the major limit is represented by the channel condition estimation performed by the TCP through loss detection and/or acknowledgement-based timing information. This paper proposes congestion control middleware layer (C2MLC), a centralized and collaborative middleware with dynamic bandwidth management, that aims to improve performance and QoS for TCP flows in the aforementioned scenarios. Results of ns-3 simulations show an improvement in aggregate throughput, a significant reduction of
latencies because of low queues occupancy levels, and higher fairness and friendliness guarantees among flows.
They also confirm that C2MLC allows a dynamic and efficient usage of the bottleneck link, avoiding a waste of resources when some client nodes are unable to fully exploit their transmission potential
Transmission Control Protocol and Active Queue Management together against congestion: cross-comparison through simulations
No full textMost Internet traffic is carried by the Transmission Control Protocol (TCP) nowadays, even in the case of real-time services. Detecting and mitigating the congestion is one of the primary tasks of this protocol, in fact, different TCP versions are defined by their congestion control algorithms. Furthermore, Active Queue Management (AQM) algorithms share the same goal of congestion mitigation with TCP; in particular, the most efficient congestion control occurs when AQM and TCP work together. This paper presents a brief survey and a cross-comparison of the latest and most important TCP and AQM variants, then provides an evaluation of a different kind of performance on the ns-3 network simulator over various types of environments (multiple Round Trip Time, long delay, different congestion levels, etc.). In any shared bottleneck, the choice of the TCP-AQM couple to adopt is crucial. We will show that the results are not univocal and the “one size fits all” solution does not exist. Moreover, the proper couple depends on the performance that we want to boost and on the environment that we have to deal with
QRM: A queue rate management for fairness and TCP flooding protection in mission-critical networks
No full textWhen statistical multiplexing is used to provide connectivity to a number of client hosts through a high-delay link, the original TCP as well as TCP variants designed to improve performance on those links often provide poor performance and sub-optimal QoS properties. Centralised and collaborative resource management tools like C2ML have been proposed to guarantee intra-protocol fairness, inter-protocol friendliness, low queues utilisation and optimal throughput along with the reliable delivery of packets. However, such tools offer only very limited security guarantees. Both good citizenship and security from flooding attacks are fundamental conditions for the provision of fairness, especially in mission-critical networks. For example, perpetrators of a man-provoked disaster may want to perform a resource exhaustion attack on the network supporting disaster recovery operations, so as to cut out legitimate users from the communications and increase the emergency impact. In this paper we present Queue Rate Management (QRM), an Active Queue Management scheme able to provide protection from traffic overflow attacks in scenarios where access to the shared link is controlled by a tool that assigns to client hosts a bandwidth upper bound. The proposed algorithm checks whether a node is exceeding its allowed rate, and consequently decides whether to keep or drop packets coming from that host. We mathematically prove that with QRM the gateway queue size can never exceed the Bandwidth-Delay Product of the channel. Furthermore, we employ the ns-3 network simulator to compare QRM with CoDel, RED and GREEN, showing how QRM provides better performance in terms of both throughput and QoS guarantees in the aforementioned scenarios
Towards Massively Multipath Transmissions for Public Safety Communications
No full textDuring their day-to-day tasks, public safety operators rely on commercial mobile networks in order to perform
data communications and make use of data-based services. In major disasters, however, it is the norm to witness high degrees
of network congestion and, often, to experience service outages caused by infrastructural damage. This may strongly hinder the
operativity of emergency operators, that expect to rely on resilient communication infrastructures and that demand network availability no matter what. In order for today mobile networks to provide such capabilities, some degree of redundancy should be introduced, either in hardware as infrastructural deployments or in software as data replication mechanisms. This paper focuses on the latter approach. It proposes a network framework to enable collaborative hosts to concurrently forward replicated data over an arbitrary number of channels, in order to compensate for
high packet losses or sudden unavailability of routing paths. The data replication and the forwarding behavior are concerted
by an SDN controller, that transparently implements a network abstraction to virtually pool hosts network resources. The paper
also presents the test bed that has been built and used to extract the emulation results. These demonstrate that the proposal have
the potential to strongly improve data communication capabilities in constrained scenarios, in the form of higher data rates and
stronger resilience guarantees. Last but not least, it is shown that services availability may be provided in much more cases, even
when regular operativity fails
Enabling Resource Pooling in Wireless Networks through Software-Defined Orchestration
No full textThis paper proposes a network paradigm where network resources are virtually pooled through an OpenFlow controller that serves as the network orchestrator. The benefits that our proposal may guarantee with respect to the solutions currently published in literature are the installation, configuration and implementation simplicity, strong expandability properties, fallback behavior if needed, resilience to link failures, improvement of uplink data rates in addition to the downlink and, last but not least, the compatibility with common equipment, as no ad-hoc network protocols are needed. To assess the performance of our proposal, we present the test bed that has been built and used to extract the emulation results. Depending on the network characteristics, it is shown how an efficient orchestrator may succeed in allowing users to efficiently exploit the available network resources. We also show how, even in the worst-cases, the proposal exhibits significant performance improvements with respect to transfers where resources are not pooled among hosts
Which AQM fits IoT better?
No full textMost of the Internet traffic is carried by Transmission Control Protocol (TCP) nowadays, even in the case of
real-time services and IoT environments. A key point of each TCP variant that defines the specific variant trademark is the
congestion control algorithm. This congestion control, alone, is not able to mitigate the congestion problem completely; the most
efficient solution, to be coupled with it, is the Active Queue Manager (AQM). In this paper, we analyze the response to
congestion provided by the novel AQMs when coupled with popular TCP variants and, has happened in IoT networks, with
a mix of TCP variants simultaneously active on the network. We provide extensive simulations within ns-3 to highlight what is the
better AQM solution for IoT networks by considering the TCP algorithm and other environmental conditions like the number of
active nodes, the network RTT and the presence of multiple RTT flows. We collected network metrics like throughput, goodput,
latency, RTT variation, flows’ fairness and a simple drop analysis
How to avoid TCP Congestion without dropping Packets: an Effective AQM called PINK
Get PDFThis paper proposes PINK (Passive INverse feedbacK), a queue management algorithm designed to indi- rectly impose a certain resource allocation policy on defined sets of client hosts. PINK adds intelligence at intermediate nodes that connect client hosts to bottleneck links or to external networks in general, al- lowing these nodes to dynamically modify the TCP Acknowledgements (ACKs) segments passing through. The modification consists in replacing advertised Receive Window fields (RCV.WNDs) with custom values, in order to enforce a specific bandwidth utilization upper bound. To compute new RCV.WND values, PINK needs only the number of active connections, the flows RTTs and the transmission channel bandwidth. It follows that PINK permits to impose a centralized bandwidth management without the cooperation of clients, which means that no modification or addition to end hosts is needed. Furthermore, as demon- strated in this paper, our proposal does not constrain client hosts performance without purpose; on the contrary, PINK improves efficiency on multiplexed channels by exploiting their capacity and by main- taining a low queuing delay and guarantees optimal flow fairness without forcing any packet drop. We validate PINK performance in multiple scenarios by using the ns-3 network simulator
Reducing Latency in Satellite Emergency Networks through a Cooperative Transmission Control
No full textThe vast majority of efforts aimed to improve network performance are focused on the increase of application
throughput. The same holds in the context of Emergency Networks, where operators ask for more bandwidth in order to
exploit data-intensive services.
Following a steady growth in network capacities and number of users, large buffers have been inserted all over the Internet. Their
effects on networks are non-trivial: while they may effectively serve the purpose of exploiting the channel potential, they also
create unnecessary delays by damaging the behavior of the most common transport protocol, TCP. Nevertheless, they are being
assumed by new congestion control algorithms, especially those tailored for high-latency links such as satellite ones. According to
the anywhere-anytime paradigm, these channels represents a key technology for both Emergency and General-Purpose networks.
In this paper we first show how buffer lengths impact the perceived delay over satellite links that employ a recently proposed
burst-based TCP protocol, and then present a cooperative transmission control that reduce buffers usage and latency while
keeping high throughput and flow fairness, thus allowing for a better service provision through satellite links
Enabling Smart Environments by avoiding TCP Congestion through PINK: a no-drop AQM
No full textThis paper proposes PINK (Passive INverse feed-bacK), a queue management algorithm designed to indirectly
impose a certain resource allocation policy on defined sets of client hosts. PINK adds intelligence at intermediate nodes that
connect client hosts to bottleneck links or to external networks in general, allowing these nodes to dynamically modify the TCP
Acknowledgments (ACKs) segments passing through. This is made by setting TCP ACK advertised Receive Windows field
(RCV.WNDs) to custom values, in order to enforce a specific bandwidth utilization upper bound. To compute new RCV.WND
values, PINK needs only the number of active connections, the flows RTTs and the transmission channel bandwidth. It
follows that PINK permits to impose a centralized bandwidth management without the cooperation of clients, which means
that no modification or addition whatsoever to end hosts is needed with the goal of enabling a smart environment by simply
configuring the access node. Furthermore, as demonstrated in this paper, our proposal does not constraints client hosts performance
without purpose; on the contrary, PINK improves efficiency on multiplexed channels by exploiting channel throughput, main-
taining a low queuing delay, and guaranteeing optimal flow fairness without forcing any packet drop
- …
