Dual Queue Coupled AQM: Deployable Very Low Queuing Delay for All

On the Internet, sub-millisecond queueing delay and capacity-seeking have traditionally been considered mutually exclusive. We introduce a service that offers both: Low Latency Low Loss Scalable throughput (L4S). When tested under a wide range of conditions emulated on a testbed using real residential broadband equipment, queue delay remained both low (median 100--300 $\mu$s) and consistent (99th percentile below 2 ms even under highly dynamic workloads), without compromising other metrics (zero congestion loss and close to full utilization). L4S exploits the properties of `Scalable' congestion controls (e.g., DCTCP, TCP Prague). Flows using such congestion control are however very aggressive, which causes a deployment challenge as L4S has to coexist with so-called `Classic' flows (e.g., Reno, CUBIC). This paper introduces an architectural solution: `Dual Queue Coupled Active Queue Management', which enables balance between Scalable and Classic flows. It counterbalances the more aggressive response of Scalable flows with more aggressive marking, without having to inspect flow identifiers. The Dual Queue structure has been implemented as a Linux queuing discipline. It acts like a semi-permeable membrane, isolating the latency of Scalable and `Classic' traffic, but coupling their capacity into a single bandwidth pool. This paper justifies the design and implementation choices, and visualizes a representative selection of hundreds of thousands of experiment runs to test our claims.Comment: Preprint. 17pp, 12 Figs, 60 refs. Submitted to IEEE/ACM Transactions on Networkin

An autonomic delivery framework for HTTP adaptive streaming in multicast-enabled multimedia access networks

The consumption of multimedia services over HTTP-based delivery mechanisms has recently gained popularity due to their increased flexibility and reliability. Traditional broadcast TV channels are now offered over the Internet, in order to support Live TV for a broad range of consumer devices. Moreover, service providers can greatly benefit from offering external live content (e. g., YouTube, Hulu) in a managed way. Recently, HTTP Adaptive Streaming (HAS) techniques have been proposed in which video clients dynamically adapt their requested video quality level based on the current network and device state. Unlike linear TV, traditional HTTP- and HAS-based video streaming services depend on unicast sessions, leading to a network traffic load proportional to the number of multimedia consumers. In this paper we propose a novel HAS-based video delivery architecture, which features intelligent multicasting and caching in order to decrease the required bandwidth considerably in a Live TV scenario. Furthermore we discuss the autonomic selection of multicasted content to support Video on Demand (VoD) sessions. Experiments were conducted on a large scale and realistic emulation environment and compared with a traditional HAS-based media delivery setup using only unicast connections

FlexDRAN: Flexible centralization in disaggregated radio access networks

Radio Access Network (RAN) disaggregation allows operators to mix-and-match multivendor components and bring RAN services from one end to the other. Despite this goal, issues of resource misuse or performance undershoot may arise because of inflexible RAN function deployment and uncoordinated decision-making across different network segments. To address these issues, this paper considers full flexibility in the synthesis of end-to-end RAN services from a set of disaggregated and uncoordinated components. In particular, five design factors are jointly considered to maximize the overall network spectral efficiency: (1) User association, (2) Remote radio unit clustering, (3) RAN functional split, (4) Fronthaul network routing, and (5) Baseband unit placement. To efficiently deal with the formulated problem, we propose a two-level turbo-based solution and compare its performance with several related works. The simulation results show that our proposed solution can not only achieve a 1.33-times spectral efficiency gain compared with state-of-the-art methods, but also provides 1.27 and 1.74 multiplexing benefits for computing and networking resources, respectively.This work is supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement 5Growth (No. 856709), Affordable5G (No. 957317), DAEMON (No. 101017109), and 6GBrain (No. 101017226)

Complex response of dinoflagellate cyst distribution patterns to cooler early Oligocene oceans

Previous studies have made extensive use of dinoflagellate cysts to reconstruct past sea surface temperature (SST). Analysis of associations of dinoflagellate cysts using two new ocean datasets for the mid Eocene (Bartonian) and early Oligocene (Rupelian) reveals clear latitudinally constrained distributions for the Bartonian, but unexpected changes in their Rupelian distribution; a significant number of species with low and mid latitude northern hemisphere occurrences in the Bartonian extend their northward ranges in the Rupelian, including some forms characterised as ‘warm water’ by previous studies. This suggests either that dinoflagellates are faithfully tracking a complex oceanographic response to Rupelian cooling, or that dinoflagellate sensitivity/adaptability to a range of ecological variables means that at a global scale their distributions are not primarily controlled by sea surface temperature-variability. Previous use of dinoflagellate cysts for palaeoclimate work has relied on rather subjective and inconsistent identification of ‘warm’ and ‘cold’ water forms, rather than comprehensive analysis of community associations at the global-scale. It is clear from this study that a better understanding of the (palaeo-)ecology of dinoflagellates and their cysts is required. Rupelian dinoflagellate cyst distribution may reflect changes in a range of environmental variables linked to early Oligocene climate-cooling, for example changes in nutrient fluxes triggered by glacially-induced base-level fall; complex reorganisation of ocean current systems between the Bartonian and Rupelian, or muted changes to Rupelian summer SSTs in the northern hemisphere that have previously been reported. Many extant dinoflagellate species also exhibit relatively broad temperature tolerance. Moreover, they have potentially extensive cryptic diversity, and are able to produce dormant cysts during short-lived environmental deterioration, all of which may act to limit the value of undifferentiated dinoflagellate cyst assemblages for identifying climate signals

Shared content addressing protocol (SCAP): optimizing multimedia content distribution at the transport layer

In recent years, the networking community has put a significant research effort in identifying new ways to distribute content to multiple users in a better-than-unicast manner. Scalable delivery is more important now video is the dominant traffic type and further growth is expected. To make content distribution scalable, in-network optimization functions are needed such as caches. The established transport layer protocols are end-to-end and do not allow optimizing transport below the application layer, hence the popularity of overlay application layer solutions located in the network. In this paper, we introduce a novel transport protocol, the Shared Content Addressing Protocol (SCAP) that allows in-network intermediate elements to participate in optimizing the delivery process, using only the transport layer. SCAP runs on top of standard IP networks, and SCAP optimization functions can be plugged-in the network transparently as needed. As such, only transport protocol based intermediate functions need to be deployed in the network, and the applications can stay at the topological end points. We define and evaluate a prototype version of the SCAP protocol using both simulation and a prototype implementation of a transparent SCAP-only intermediate optimization function

Towards intelligent scheduling of multimedia content in future access networks

The popularity of streaming multimedia services has greatly increased in recent years. Telco- and cable-providers have started offering a plethora of multimedia services in the access and aggregation network, including video on demand, interactive digital television, and time-shifted TV. However, these services introduce additional challenges, such as stringent time constraints, and high bandwidth requirements. To overcome these problems, we explore the advantages of delivering such multimedia content using deadline-aware scheduling and caching algorithms. These algorithms decide when to send and store which content. This enables the network to optimize bandwidth consumption and satisfy deadline constraints. The designed algorithm was evaluated and compared to classical deadline-unaware delivery protocols. This allows us to study the efficiency of the new algorithm, and identify the scenarios in which deadline-aware scheduling improves delivery of multimedia content

An autonomic PCN based admission control mechanism for video services in access networks

The introduction of new added value services such as IPTV has introduced great challenges for today's broadband DSL access networks as these services have stringent quality demands. In an attempt to protect the quality delivery of existing sessions, operators employ admission control mechanisms that limit the amount of sessions transmitted in the network. Current admission control mechanisms require a traffic specification of each stream, in order to know beforehand how many resources need to be reserved. For variable bit rate videos, which are bursty of nature, resources are reserved using the peak rate of the video. This leads to under-utilisation of the network as the amount of resources needed is over-dimensioned. We propose an autonomic measurement based admission control algorithm, optimised for the protection of video services in multimedia access networks. The algorithm is based on the IETF precongestion notification (PCN) mechanism and autonomically adjusts its parameters to the traffic characterisation of the video. The performance of this mechanism has been extensively evaluated in a packet based network simulation environment. Tests show that the autonomic nature of the algorithm leads to a better utilisation of the network while still avoiding any congestion in the network