Software-defined networking (SDN) and network function virtualization (NFV) processed in multi-access edge computing (MEC) cloud systems have been proposed as critical paradigms for achieving the low ...latency requirements of the tactile Internet. While virtual network functions (VNFs) allow greater flexibility compared to hardware-based solutions, the VNF abstraction also introduces additional packet processing delays. In this paper, we investigate the practical feasibility of NFV with respect to the tactile Internet latency requirements. We develop, implement, and evaluate Chain-based Low latency VNF ImplemeNtation (CALVIN), a low-latency management framework for distributed Service Function Chains (SFCs). CALVIN classifies VNFs into elementary, basic, and advanced VNFs; moreover, CALVIN implements elementary and basic VNFs in the kernel space, while the advanced VNFs are implemented in the user space. Throughout, CALVIN employs a distributed mapping with one VNF per Virtual Machine (VM) in a MEC system. Furthermore, CALVIN avoids the metadata structure processing and batch processing of packets in the conventional Linux networking stack so as to achieve short per-packet latencies. Our rigorous measurements on off-the-shelf conventional networking and computing hardware demonstrate that CALVIN achieves round-trip times from a MEC ingress point via two elementary forwarding VNFs (one in kernel space and one in user space) and a MEC server to a MEC egress point on the order of 0.32 ms. Our measurements also indicate that MEC network coding and encryption are feasible for small 256 byte packets with an MEC latency budget of 0.35 ms; whereas, large 1400 byte packets can complete the network coding, but not the encryption within the 0.35 ms.
Public Space and Play Theory Isik, Pelin; Reicher, Christa; Sezer, Ceren
Transactions of the Association of European Schools of Planning,
11/2023, Letnik:
7, Številka:
1
Journal Article
Recenzirano
Public spaces serve as the sensory system of urban life, and are crucial for interconnecting individuals, ideas, and cultures within the fabric of cities. This study provides a fresh interpretation ...of public spaces by examining people’s activities from a new perspective. By applying play theory to public space analysis, the study uncovers spontaneous and unplanned activities and the novel relationships which exist between users and their environments. In so doing it paves the way for a new approach to public space design.
With a focus on Aachen as a place of play, this study seeks to develop urban design tools that take into account users’ leisure time activities. By recognizing the unique relationships that play can create between individuals and their surroundings in terms of perceptions, intentions, actions, and uses of space, the research encourages a fresh perspective on urban design tools. Ultimately, the findings of this study offer a new design approach for creating public spaces that are more participating, inclusive, and user-centred.
Public Space and Play Theory Pelin Isik; Christa Reicher; Ceren Sezer
Transactions of the Association of European Schools of Planning,
10/2023, Letnik:
7, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Public spaces serve as the sensory system of urban life, and are crucial for interconnecting individuals, ideas, and cultures within the fabric of cities. This study provides a fresh interpretation ...of public spaces by examining people’s activities from a new perspective. By applying play theory to public space analysis, the study uncovers spontaneous and unplanned activities and the novel relationships which exist between users and their environments. In so doing it paves the way for a new approach to public space design. With a focus on Aachen as a place of play, this study seeks to develop urban design tools that take into account users’ leisure time activities. By recognizing the unique relationships that play can create between individuals and their surroundings in terms of perceptions, intentions, actions, and uses of space, the research encourages a fresh perspective on urban design tools. Ultimately, the findings of this study offer a new design approach for creating public spaces that are more participating, inclusive, and user-centred.
Memory-intensive applications, such as in-memory databases, caching systems, and key-value stores, are increasingly demanding larger main memory to fit their working sets. Conventional swapping can ...enlarge the memory capacity by paging out inactive pages to backend stores. However, existing swapping solutions suffer several performance and compatibility issues, making them unsuitable for high-concurrency and memoryintensive applications. In this paper, we redesign the swapping system and propose Lightswap, a high-performance user-space swapping solution that supports paging with both local SSDs and remote memories. First, to avoid kernel involvement, we propose to leverage the extended Berkeley Packet Filter (eBPF) for handling page faults in user space and further eliminate the heavy I/O stack with the help of user-space I/O drivers. Then, we co-design the page fault handling with lightweight thread (LWT) scheduling to improve system throughput and reduce the end-to-end page fault latency. Finally, we propose a try-catch framework in Lightswap to deal with swap-in errors which have been exacerbated by the scaling in process technology. We implement Lightswap in our production-level system and evaluate it with various benchmarks. Results show that Lightswap achieves scalable page fault notification latency (4μs under 128 LWTs), reduces the page fault handling latency by 3-5 times, and improves the throughput of memcached by more than 40% compared with the state-of-art swapping systems.
Traditionally, the only option for developers was to implement file systems (FSs) via drivers within the operating system kernel. However, there exists a growing number of file systems (FSs), notably ...distributed FSs for the cloud, whose interfaces are implemented solely in user space to (i) isolate FS logic, (ii) take advantage of user space libraries, and/or (iii) for rapid FS prototyping. Common interfaces for implementing FSs in user space exist, but they do not guarantee POSIX compliance in all cases, or suffer from considerable performance penalties due to high amounts of wait context switchs between kernel and user space processes.
We propose DEFUSE: an interface for user space FSs that provides fast accesses while ensuring access correctness and requiring no modifications to applications. DEFUSE: achieves significant performance improvements over existing user space FS interfaces thanks to its novel design that drastically reduces the number of wait context switchs for FS accesses. Additionally, to ensure access correctness, DEFUSE: maintains POSIX compliance for FS accesses thanks to three novel concepts of
bypassed file descriptor (FD) lookup
,
FD stashing
, and
user space paging
. Our evaluation spanning a variety of workloads shows that by reducing the number of wait context switchs per workload from as many as 16,000 or 41,000 with filesystem in user space down to 9 on average, DEFUSE: increases performance 2× over existing interfaces for typical workloads and by as many as 10× in certain instances.
Conflict is one of the important factors affecting user satisfaction and trust in smart environments, yet conflict modeling in mixed initiative smart environments has not been sufficiently explored. ...Most of the existing literature on conflict in smart homes are centered on conflicts between users. Although research has shown that about 75% of conflicts are between users and system <xref ref-type="bibr" rid="ref1">1 , only a few studies have considered user-system conflicts in smart homes. The aim of this article is to empirically propose both a definition and a run-time detection method for conflicts between users and smart home systems. Our empirical study is based on conflict sample scenarios collected from 163 users. Using clustering on these scenarios, we form an empirical definition of user-system conflict in smart homes. We also propose two functions that characterize each class of the collected scenarios, and we detect conflicts from this characterization. Our conflict detection model could help users achieve a more satisfactory experience in smart homes. Moreover, the model can offer benefits for system developers to design and deploy more reliable smart homes.
This paper explains the importance (1) of full user-space identification with categorization in requirements engineering (RE) and of ensuring that the categorization is a partition of the user space, ...(2) of the creation and application of user-space-covering personas in RE, (3) of the use of grounded analysis to do RE to produce a specification as a grounded theory, and (4) of privacy and security features in computer-based systems. Then it gives the steps of a grounded analysis method for doing user-space identification with categorization and producing personas as a grounded theory that is describing the classes of users for a computer-based system. The paper summarizes a case study of an iterative application of this method to arrive at a set of user-space-covering personas for privacy and security features in computer-based systems, and it shows how these personas can be used to inform RE for these features. The full case study and the descriptions of the personas are found in the appendices.
•We summarize the importance of the creation and application of personas in requirements engineering (RE).•We summarize the importance of user-space identification with categorization in RE.•We summarize the importance of privacy and security (PAS) in computer-based systems.•We give the steps of a grounded analysis (GA) method for doing RE.•We give a case study of using the GA method to do RE for PAS tools.
Scalable Analytics on Fast Data Kipf, Andreas; Pandey, Varun; Böttcher, Jan ...
ACM transactions on database systems,
01/2019, Letnik:
44, Številka:
1
Journal Article
Recenzirano
Today’s streaming applications demand increasingly high event throughput rates and are often subject to strict latency constraints. To allow for more complex workloads, such as window-based ...aggregations, streaming systems need to support
stateful
event processing. This introduces new challenges for streaming engines as the state needs to be maintained in a consistent and durable manner and simultaneously accessed by complex queries for real-time analytics.
Modern streaming systems, such as Apache Flink, do not allow for efficiently exposing the state to analytical queries. Thus, data engineers are forced to keep the state in external data stores, which significantly increases the latencies until events become visible to analytical queries. Proprietary solutions have been created to meet data freshness constraints. These solutions are expensive, error-prone, and difficult to maintain. Main-memory database systems, such as HyPer, achieve extremely low query response times while maintaining high update rates, which makes them well-suited for analytical streaming workloads. In this article, we explore extensions to database systems to match the performance and usability of streaming systems.
Conventional data deletion is implemented for reclaiming storage as a rapid operation. However, the content of the deleted file still persists on the storage medium. Secure data deletion is a task of ...deleting data irrecoverably from the physical medium. Mobile devices use flash memory as the internal storage. However, flash memory does not support the in-place update which is in direct opposition to efforts to securely delete sensitive data from storage. Previously practical secure deletion tools and techniques are rapidly becoming obsolete, and are rendered ineffective. Therefore, research on secure data deletion approaches for mobile devices has become a practical and urgent issue.
In this paper, we study the logic structure and operation characteristics of flash memory, and survey related work on secure data deletion. In addition, we define the adversary capability and threat model, putting forward the design goals that secure data deletion scheme needs to meet. Then an approach in user space that uses the user space file system to provide secure deletion guarantees at file granularity is proposed, independent of the characteristics of the underlying file system and storage medium. The approach encrypting every file on an insecure medium with a unique key that can later be discarded to cryptographically render the data irrecoverable. Moreover, we implement our secure data deletion approach on Android platform named SADUS. Finally, experiments are conducted, and the results indicate that SADUS prototype ensures the secure deletion of data in flash memory on mobile devices with comparable overhead and it can meet the requirements of the users in daily use.
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