Best Effort and Practice Activation Codes

Activation Codes are used in many different digital services and known by many different names including voucher, e-coupon and discount code. In this paper we focus on a specific class of ACs that are short, human-readable, fixed-length and represent value. Even though this class of codes is extensively used there are no general guidelines for the design of Activation Code schemes. We discuss different methods that are used in practice and propose BEPAC, a new Activation Code scheme that provides both authenticity and confidentiality. The small message space of activation codes introduces some problems that are illustrated by an adaptive chosen-plaintext attack (CPA-2) on a general 3-round Feis- tel network of size 2^(2n) . This attack recovers the complete permutation from at most 2^(n+2) plaintext-ciphertext pairs. For this reason, BEPAC is designed in such a way that authenticity and confidentiality are in- dependent properties, i.e. loss of confidentiality does not imply loss of authenticity.Comment: 15 pages, 3 figures, TrustBus 201

Energy-Efficient NoC for Best-Effort Communication

A Network-on-Chip (NoC) is an energy-efficient on-chip communication architecture forMulti-Processor System-on-Chip (MPSoC) architectures. In an earlier paper we proposed a energy-efficient reconfigurable circuit-switched NoC to reduce the energy consumption compared to a packetswitched NoC. In this paper we investigate a chordal slotted ring and a bus architecture that can be used to handle the best-effort traffic in the system and configure the circuitswitched network. Both architectures are compared on their latency behavior and power consumption. At the same clock frequency, the chordal ring has the major benefit of a lower latency and higher throughput. But the bus has a lower overall power consumption at the same frequency. However, if we tune the frequency of the network to meet the throughput requirements of control network, we see that the ring consumes less energy per transported bit

The Asymmetric Best-Effort Service

We present Asymmetric Best-Effort, a novel service to provide a ``throughput versus delay jitter`` differentiated service for IP packets. With this service, every best effort packet is marked as either green or blue. Green packets, typically sent by real-time applications such as interactive audio, receive more losses during bouts of congestion than blue ones. In return, they receive less delay jitter. Both green and blue services are best-effort. The incentive to choose one or other is based on the nature of one`s traffic and on traffic conditions. If applications are TCP-friendly, an application sending blue packets will receive more throughput but also more delay jitter, than it would if it sent green packets for a given network state and path. Service provision at each cooperating router can be achieved by Packet Admission Control (PAC) and scheduling. We develop and simulate an initial algorithm that supports this service. It uses a modified version of RED for packet drop differention while scheduling of blue and green packets is facilated using Earliest Deadline First (EDF). These first results show the feasiblity of the service

Insights into the Fallback Path of Best-Effort Hardware Transactional Memory Systems

DOI 10.1007/978-3-319-43659-3Current industry proposals for Hardware Transactional Memory (HTM) focus on best-effort solutions (BE-HTM) where hardware limits are imposed on transactions. These designs may show a significant performance degradation due to high contention scenarios and different hardware and operating system limitations that abort transactions, e.g. cache overflows, hardware and software exceptions, etc. To deal with these events and to ensure forward progress, BE-HTM systems usually provide a software fallback path to execute a lock-based version of the code. In this paper, we propose a hardware implementation of an irrevocability mechanism as an alternative to the software fallback path to gain insight into the hardware improvements that could enhance the execution of such a fallback. Our mechanism anticipates the abort that causes the transaction serialization, and stalls other transactions in the system so that transactional work loss is mini- mized. In addition, we evaluate the main software fallback path approaches and propose the use of ticket locks that hold precise information of the number of transactions waiting to enter the fallback. Thus, the separation of transactional and fallback execution can be achieved in a precise manner. The evaluation is carried out using the Simics/GEMS simulator and the complete range of STAMP transactional suite benchmarks. We obtain significant performance benefits of around twice the speedup and an abort reduction of 50% over the software fallback path for a number of benchmarks.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Less-than-Best-Effort capacity sharing over high BDP networks with LEDBAT

There has been a renewed interest at the Internet Engineering Task Force (IETF) in using Less-than-Best Effort (LBE) methods for background applications. IETF recently published a RFC for Low Extra Delay Background Transport (LEDBAT), a congestion control algorithm for LBE transmissions. This paper provides an analysis of LEDBAT performance over congested large bandwidth X delay product (LBDP) networks, and assesses the validity of having a fixed target queuing time. In particular, we lead a study of the impact of this target queuing delay when LEDBAT is used over 4G satellite networks. The rationale is to explore the possibility to grab the unused 4G satellite links' capacity to carry non-commercial traffic. We show that this is achievable with LEDBAT. However, depending on the fluctuation of the load, performance improvements could be obtained by properly setting the target value. We generalize this evaluation over different congested LBDP networks and confirm that the target value might need to be adjusted to networks' and traffic's characteristics. Further work will study whether and how this parameter should be dynamically adapted, and LEDBAT's congestion control improved