rm.bib
@inproceedings{SILVA_INFORUM_2012,
author = {Silva, P. and Marau, R. and Almeida, L.},
title = {Experimental validation of temporal isolation among dynamic communication channels},
booktitle = {3rd Simposium de Inform\'{a}tica (INForum'2012) Poster Session},
year = {2012},
editor = {},
volume = {},
series = {},
pages = {},
address = {Lisbon, Portugal},
month = {September},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Real-Time communications, FTT-SE},
note = {},
key = {},
abstract = {}
}
@inproceedings{MIFDAOUI_RTN_2012,
author = {Mifdaoui, A. and Behnam, M. and Nolte, T. and Pedreiras, P. and Almeida, L. and Marau, R.},
title = {Exploring alternatives to use master/slave full duplex switched Ethernet for avionics embedded applications},
booktitle = {11th International Workshop on Real-Time Networks (RTN'2012) Proceedings},
year = {2012},
editor = {},
volume = {},
series = {},
pages = {},
address = {Pisa, Italy},
month = {July},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Real-Time communications, FTT, Ethernet, Avionics},
note = {},
key = {},
abstract = {The complexity of distributed real-time systems, including military embedded applications, is increasing due to an increasing number of nodes, their functionality and higher amounts of exchanged data. This higher complexity imposes major development challenges when nonfunctional properties must be enforced. On the other hand, the current military communication networks are a generation old and are no longer effective in facing such increasingly complex requirements. A new communication network, based on Full Duplex Switched Ethernet and Master/slave approach, has been proposed previously. However, this initial approach is not efficient in terms of network bandwidth utilization. In this paper we propose two new alternative approaches that can use the network bandwidth more efficiently. In addition we provide a preliminary qualitative assessment of the three approaches concerning different factors such as performance, scalability, complexity and flexibility}
}
@inproceedings{IQBAL_SIES_2012,
author = {Iqbal, Z. and Almeida, L. and Marau, R. and Behnam, M. and Nolte, T.},
title = {Implementing hierarchical scheduling on COTS Ethernet switches using a master/slave approach},
booktitle = {7th IEEE International Symposium on Industrial Embedded Systems (SIES'2012) Proceedings},
year = {2012},
editor = {},
volume = {},
series = {},
pages = {76--84},
address = {Karlsruhe, Germany},
month = {June},
organization = {},
publisher = {},
doi = {10.1109/SIES.2012.6356572},
issn = {},
isbn = {978-1-4673-2683-4},
keywords = {Real-Time communications, FTT, Ethernet, FTT-SE},
note = {},
key = {},
abstract = {Hierarchical scheduling is instrumental to efficiently deploy component-based designs and achieve composability. It allows partitioning resources into multiple levels, hiding the complexity within each partition behind its respective interface. In this paper we focus on the network resource, particularly on Ethernet using ordinary COTS switches, and we show how hierarchical scheduling can be efficiently deployed using a master/slave approach that enforces the temporal properties of the partitions. We use the FTT-SE protocol for being open source and a bandwidth efficient master/slave alternative currently available for real-time communication over Ethernet. We present a response-time analysis for the traffic submitted within each partition and we validate it using experimental results obtained from a prototype implementation. In particular, the results highlight the strong partitioning capabilities of our approach, with full temporal isolation across partitions in different branches of the hierarchy}
}
@inproceedings{MARAU_WFCS_2012,
author = {Marau, R. and Behnam, M. and Iqbal, Z. and Silva, P. and Almeida, L. and Portugal, P.},
title = {Controlling multi-switch networks for prompt reconfiguration},
booktitle = {9th IEEE International Workshop on Factory Communication Systems (WFCS'2012) Proceedings},
year = {2012},
editor = {},
volume = {},
series = {},
pages = {233--242},
address = {Lemgo, Germany},
month = {May},
organization = {},
publisher = {},
doi = {10.1109/WFCS.2012.6242571},
issn = {},
isbn = {978-1-4673-0693-5},
keywords = {Real-Time communications, FTT, Ethernet, FTT-SE},
note = {},
key = {},
abstract = {Recent trends in distributed embedded systems, such as those found in avionics and trains, have shown an increase in the amount and heterogeneity of the information that needs to be exchanged, together with a growing importance of supporting dynamic reconfiguration and adaptive behaviors. In this paper we focus on Ethernet technologies with real-time reconfiguration support and we address the case of middle-size networking infrastructures with a few switches. We use the FTT-SE protocol with the needed adaptations to support dynamic heterogeneous real-time transactions in multi-hop networks. The paper presents a worst-case response-time analysis that provides timeliness guarantees, improving the results obtained with another previous analysis, decreasing the needed network capacity for guaranteed schedulability by 25% on average. Practical experiments and simulation results validate the proposed approach and analysis}
}
@inproceedings{SILVA_DCOSS_2012,
author = {Silva, P. and Silva, L. and Marau, R. and Almeida, L.},
title = {Demonstrating Real-Time Reconfiguration of Video Sensing Service-Oriented Applications},
booktitle = {8th IEEE International Conference on Distributed Computing in Sensor Systems (DCOSS'2012) Demos session},
year = {2012},
editor = {},
volume = {},
series = {},
pages = {295--296},
address = {Hangzhou, China},
month = {May},
organization = {},
publisher = {},
doi = {10.1109/DCOSS.2012.59},
issn = {},
isbn = {978-1-4673-1693-4},
keywords = {Real-Time communications, FTT, Ethernet, FTT-SE, iLAND, Middleware},
note = {},
key = {},
abstract = {Growing interest in facilitating the construction of real-time applications from reusable components and their run-time reconfiguration is motivating the use of Service-Oriented approaches in the real-time domain. The iLAND ARTEMIS project researches such direction, aiming at providing an SO middleware that supports dynamic reconfiguration, namely addition and removal of services and QoS-based hot swap of service implementations. In this demonstration we exhibit a few simple video sensing applications that illustrate the desired prompt reconfigurations without significant glitches and within bounded time as required for real-time applications}
}
@inproceedings{SILVA_RTSSATWORK_2011,
author = {Silva, L. and Marau, R. and Almeida, L.},
title = {Demonstrating Real-Time Reconfiguration in Service-Oriented Distributed Systems},
booktitle = {32nd IEEE Real-Time Systems Symposium (RTSS'2011) at Work Session},
year = {2011},
editor = {},
volume = {},
series = {},
pages = {},
address = {Vienna, Austria},
month = {November},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Real-Time communications, Distributed systems, iLAND, Service-oriented system},
note = {},
key = {},
abstract = {}
}
@inproceedings{BEHNAM_WCTT_2011,
author = {Behnam, M. and Iqbal, Z. and Silva, P. and Marau, R. and Almeida, L. and Portugal, P.},
title = {Engineering and Analyzing Multi-Switch Networks with Single Point of Control},
booktitle = {1st International Workshop on Worst-case Traversal Time (WCTT'2011) Proceedings},
year = {2011},
editor = {},
volume = {},
series = {},
pages = {},
address = {Vienna, Austria},
month = {November},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Real-Time communications, FTT, FTT-SE, Ethernet, Embedded systems},
note = {},
key = {},
abstract = {Recent trends in distributed embedded systems have shown an increase in the amount and heterogeneity of the information that needs to be exchanged, together with a growing importance of supporting dynamic reconfiguration and adaptive behaviors. In this paper we focus on Ethernet technology and we address the case of middle-size networking infrastructure with a few switches. We use the FTT-SE protocol to support dynamic heterogeneous real-time transactions with temporal isolation and we propose the needed scheduling adaptations to support multi-hop network configurations. The paper also includes a companion worst-case response-time analysis that allows verifying the timeliness of the system}
}
@inproceedings{BEHNAM_ETFA_2011,
author = {Behnam, M. and Marau, R. and Pedreiras, P.},
title = {Analysis and optimization of the MTU in real-time communications over Switched Ethernet},
booktitle = {16th Conference on Emerging Technologies Factory Automation (ETFA'2011) Proceedings},
year = {2011},
editor = {},
volume = {},
series = {},
pages = {1--7},
address = {Toulouse, France},
month = {September},
organization = {},
publisher = {},
doi = {10.1109/ETFA.2011.6059021},
issn = {1946-0740},
isbn = {978-1-4577-0016-3},
keywords = {Ethernet, FTT, FTT-SE, protocols, Real-Time communications, Scheduling, MTU},
note = {},
key = {},
abstract = {The Flexible Time-Triggered communication over Switched Ethernet protocol (FTT-SE) was proposed to overcome the limitation of guaranteeing the real-time communication requirements of conventional switches, and at the same time to support reconfiguration of dynamic adaptive systems. The protocol fragments large messages into a sequence of packets that are individually scheduled. The maximum transmission unit (MTU), that restricts the packets size, has a significant effect on the schedulability of the packets. In this paper, we investigate the problem of selecting the optimal MTU size that maximizes the schedulability of real-time messages. We propose two algorithms to find optimal/sub-optimal values of MTU; the first one finds an optimal solution but exhibits high computational complexity, while the second one is sub-optimal but exhibits a lower computational complexity. Finally, we evaluate our proposed algorithms by means of simulation studies and compare their results with the results of assigning MTU to the maximum packet size that the protocol can allow}
}
@article{SILVESTRE_IE_2011,
author = {Silvestre, J. and Almeida, L. and Marau, R. and Pedreiras, P.},
title = {On-line QoS Management for Multimedia Real-Time Transmission in Industrial Networks},
journal = {IEEE Transactions on Industrial Electronics},
year = {2011},
volume = {58},
number = {3},
pages = {1061--1071},
month = {March},
doi = {10.1109/TIE.2010.2049711},
issn = {0278-0046},
isbn = {ISBN-OPTIONAL},
keywords = {Ethernet, Real-Time communications, Industrial Networks, quality of service},
note = {},
key = {},
abstract = {A growing number of industrial applications incorporate multimedia information processing. These multimedia applications are commonly distributed and subject to time constraints that must be met across networks without creating intolerable interference over typical control flows. However, multimedia traffic, in general, and video streaming, in particular, have specific characteristics that conflict with the operational framework of conventional real-time protocols. In particular, video compressors generate highly variable bit-rate streams that mismatch the constant-bit-rate channels typically provided by real-time protocols, severely reducing the efficiency of network utilization. This paper focuses on low-latency multimedia transmission over Ethernet with dynamic quality-of-service (QoS) management. We propose a multidimensional mechanism that controls, in an integrated way, both the compression parameters and the network bandwidth allocated to each stream. The goal is to provide the best possible QoS to each stream, recomputing the compression levels and network bandwidth whenever significant events, such as channel setup/teardown, or structural changes happen. This paper also presents novel QoS metrics based both on the image quality and network parameters. Several experiments with prerecorded video streams illustrate the advantages of the proposed approach and the convenience of the metrics}
}
@inproceedings{MARAU_ETFA_2010,
author = {Marau, R. and Almeida, L. and Pedreiras, P. and Lakshmanan, K. and Rajkumar, R.},
title = {Utilization-based schedulability analysis for switched Ethernet aiming dynamic QoS management},
booktitle = {15th IEEE Conference on Emerging Technologies and Factory Automation (ETFA'2010) Proceedings},
year = {2010},
editor = {},
volume = {},
series = {},
pages = {1--10},
address = {Bilbao, Spain},
month = {September},
organization = {},
publisher = {},
doi = {10.1109/ETFA.2010.5641360},
issn = {1946-0740},
isbn = {978-1-4244-6848-5},
keywords = {Ethernet, FTT, FTT-SE, Switch, computational complexity, computer network management, computer network reliability, local area networks, quality of service, routing protocols, scheduling, telecommunication switching},
note = {},
key = {},
abstract = {Ethernet switches are typically found in many large-scale distributed real-time systems providing low-end transactions as well as bulk backbone routing to real-time applications. The FTT-SE protocol (Flexible Time-Triggered communication over Switched Ethernet) is a recent proposal to bypass the limitations of conventional switches in terms of real-time behavior while catering for growing requirements on dynamic reconfigurability and adaptability. For this end, this paper develops linear time-complexity and memory-efficient on-line admission control tests based on utilization bounds for Rate-Monotonic and EDF scheduling on Ethernet switches using FTT-SE, which are suited for dynamic Quality of Service (QoS) management. Our analysis also has broader applicability in general periodic task sets with bounded release delays. For FTT-SE with 100 Mbps links and 1500 bytes of maximum packet size, our sufficient schedulability condition achieves an utilization bound of 61% for RMS and 88% for EDF. Simulation results on randomly generated task sets demonstrate that such bounds are within 18% and 5% utilization of the ideal tests for RMS and EDF, respectively}
}
@inproceedings{MARAU_ETFA_2010_2,
author = {Marau, R. and Almeida, L. and Sousa, M. and Pedreiras, P.},
title = {A middleware to support dynamic reconfiguration of real-time networks},
booktitle = {15th IEEE Conference on Emerging Technologies and Factory Automation (ETFA'2010) Proceedings},
year = {2010},
editor = {},
volume = {},
series = {},
pages = {1--10},
address = {Bilbao, Spain},
month = {September},
organization = {},
publisher = {},
doi = {10.1109/ETFA.2010.5641306},
issn = {1946-0740},
isbn = {978-1-4244-6848-5},
keywords = {Middleware, Embedded systems, Distributed embedded systems, Real-Time communications, resource management},
note = {},
key = {},
abstract = {The middleware is an important software component when designing an application, facilitating the development and deployment of the applications. In the case of Distributed Embedded Systems (DES), the middleware should provide basic functionalities to abstract the complexity that results from network distribution, namely data consistency, events synchronization and resource management. Often DES applications exhibit real-time requirements and have to deal with dynamic environments that present evolving requirements. While some middleware architectures have been proposed to address resource provisioning and QoS management, none of those middle-wares supports dynamic resource reconfiguration while providing real-time guarantees. This paper proposes a middleware layer, based on the services provided by a flexible real-time communication protocol, addressing distribution abstraction, dynamic reconfiguration and dynamic QoS management under real-time constraints}
}
@inproceedings{SANTOS_WFCS_2010,
author = {Santos, R. and Vieira, A. and Pedreiras, P. and Oliveira, A. and Almeida, L. and Marau, R. and Nolte, T.},
title = {Flexible, efficient and robust real-time communication with server-based Ethernet Switching},
booktitle = {8th IEEE International Workshop on Factory Communication Systems (WFCS'2010) Proceedings},
year = {2010},
editor = {},
volume = {},
series = {},
pages = {131--140},
address = {Nancy, France},
month = {May},
organization = {},
publisher = {},
doi = {10.1109/WFCS.2010.5548632},
issn = {},
isbn = {978-1-4244-5462-4},
keywords = {Ethernet, FTT, FTT-SE, Real-Time communications, Switch, Embedded system, Ethernet networks, Protocols, Real time systems, Robustness, Throughput},
note = {},
key = {},
abstract = {The information exchanged in Networked Embedded Systems is steadily increasing in quantity, size, complexity and heterogeneity, with growing requirements for arbitrary arrival patterns and guaranteed QoS. One of the networking protocols that is becoming more common in such systems is Ethernet and its real-time Ethernet variants. However, they hardly support all the referred requirements in an efficient manner since they either favour determinism or throughput, but not both. A potential solution recently proposed by the authors is the Server-SE protocol that uses servers to confine traffic associated to specific applications or subsystems. Such an approach is dynamically reconfigurable and adaptive, being more bandwidth efficient while providing composability in the time domain. This paper proposes integrating the servers inside the Ethernet switch, boosting both the flexibility and the robustness of Server-SE, allowing, for example, the seamless connection of any Ethernet node. The switch is an FTT-enabled Ethernet Switch and the paper discusses two specific ways of integrating the servers, namely in software or in hardware. These options are described and compared analytically and experimentally. The former favours flexibility in the servers design and management while the latter provides lower latency}
}
@inproceedings{SANTOS_WARM_2010,
author = {Santos, R. and Vieira, A. and Marau, R. and Pedreiras, P. and Oliveira, A. and Almeida, L. and Nolte, T.},
title = {Improving the efficiency of Ethernet switches for real-time communication},
booktitle = {1st International Workshop on Adaptive Resource Management (WARM'2010) Proceedings},
year = {2010},
editor = {},
volume = {},
series = {},
pages = {},
address = {Stockholm, Sweden},
month = {April},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Ethernet, Switch, Real-Time Communications},
note = {},
key = {},
abstract = {}
}
@inproceedings{SANTOS_REC_2010,
author = {Santos, R. and Vieira, A. and Marau, R. and Pedreiras, P. and Oliveira, A. and Almeida, L.},
title = {Architectural Solutions for Server Scheduling Communication within Ethernet Switches},
booktitle = {6th Jornadas sobre Sistemas Reconfigur\'{a}veis (REC'2010) Proceedings},
year = {2010},
editor = {},
volume = {},
series = {},
pages = {},
address = {Aveiro, Portugal},
month = {February},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Embedded Systems, NES, FTT, Ethernet, Switch, quality of service},
note = {},
key = {},
abstract = {The information exchanged in Network Embedded Systems (NES) is steadily increasing both in terms of quantity, size and complexity. For instance, applications comprising data originated in simple 10 bit ADCs side-by-side with multi-kilobyte variable bit-rate multimedia traffic are, nowadays, becoming a commonplace. Moreover, many NES are frequently subject to some kind of real-time constraints and thus the associated information exchanges are subject to timeliness requirements. However, the existing real-time Ethernet protocols have difficulties in handling these streams efficiently, particularly in what regards the arbitrary arrival patterns and different QoS requirements. To overcome these limitations, the authors proposed recently the integration of server-based traffic scheduling concepts within a customizable Ethernet switch, called FTT-enabled switch. The server scheduling unit can be placed in different points of the FTT-enabled switch architecture. The particular placement chosen has a noticeable impact in terms of server responsiveness, flexibility, hardware complexity and global system schedulability. This paper presents a qualitative comparison about the different architectural solutions and presents a prototype implementation of the hardware-based architecture. Extensive experimental results are also included, showing the correctness of the server operation both in terms of bandwidth guarantees, traffic isolation and latency bounds}
}
@inproceedings{SANTOS_CRTS_2009,
author = {Santos, R. and Vieira, A. and Marau, R. and Pedreiras, P. and Oliveira, A. and Almeida, L. and Nolte, T.},
title = {Implementing Server-Based Communication within Ethernet Switches},
booktitle = {2nd Workshop on Compositional Theory and Technology for Real-Time Embedded Systems (CRTS'2009) Proceedings},
year = {2009},
editor = {},
volume = {},
series = {},
pages = {},
address = {Washington, USA},
month = {December},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Real-Time communications, FTT, FTT-SE, Ethernet, Switch},
note = {},
key = {},
abstract = {Server-based architectures have generated recently a considerable interest. They provide an effective means to support composability, i.e., the integration of diverse components while guaranteeing the required service-levels to each one. While common in CPU scheduling, the support for server-oriented architectures in the domain of real-time communication protocols is more limited due to distribution and specific medium access control and queues management policies within network controllers, network devices and protocol stacks. Consequently, server-based traffic scheduling is either not supported or supported in a limited and inefficient way, e.g., only basic servers, no hierarchical composition, static configuration. To overcome such limitations, the authors proposed recently the Server-SE protocol, which supports unconstrained server-based traffic scheduling over switched Ethernet, using the FTT-SE protocol and common off-the-shelf (COTS) switches as platform. This paper extends such work by bringing the servers inside a customized Ethernet switch. This option provides a high level of determinism, robustness and flexibility, being particularly suited to open systems as servers can easily be added, composed, adapted and removed at run-time. The proposal is validated with a prototype implementation and experimental results that show its effectiveness in enforcing correct resource reservations}
}
@inproceedings{SANTOS_IECON_2009,
author = {Santos, R. and Marau, R. and Vieira, A. and Pedreiras, P. and Oliveira, A. and Almeida, L.},
title = {A synthesizable ethernet switch with enhanced real-time features},
booktitle = {35th Annual Conference of IEEE Industrial Electronics (IECON'2009) Proceedings},
year = {2009},
editor = {},
volume = {},
series = {},
pages = {2817--2824},
address = {Oporto, Portugal},
month = {November},
organization = {},
publisher = {},
doi = {10.1109/IECON.2009.5415405},
issn = {1553-572X},
isbn = {978-1-4244-4650-6},
keywords = {FTT, Ethernet, Real-Time communications, Computer architecture, Ethernet networks, Field programmable gate arrays, Hardware, Protocols, Prototypes, Substation protection, Switches},
note = {},
key = {},
abstract = {The use of switched Ethernet for safe real-time communication still suffers from undesired phenomena, such as blocking caused by long non-preemptive frames, lack of protection against errors in the time domain, couplings across virtual LANs and priority levels via internal switch shared resources. Recently, a few solutions were proposed to cope with such phenomena. One such solution is based on an enhanced switch following the Flexible Time-Triggered paradigm, which enforces strict service differentiation with any kind of traffic scheduling, blocking-free forwarding and timing errors confinement. In this paper we propose a new architecture following an hardware-software co-design approach that simplifies the development of the enhanced switch features by detaching the traffic scheduling from the traffic switching. The paper shows experimental results with an actual switch prototype that confirm the desired switch properties}
}
@inproceedings{SANTOS_REC_2009,
author = {Santos, R. and Marau, R. and Oliveira, A. and Pedreiras, P. and Almeida, L.},
title = {FPGA-based Implementation of an Ethernet Switch for Real-Time Applications},
booktitle = {5th Jornadas sobre Sistemas Reconfigur\'{a}veis (REC'2009) Proceedings},
year = {2009},
editor = {},
volume = {},
series = {},
pages = {},
address = {Monte de Caparica, Portugal},
month = {February},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Ethernet, Switch, Real-Time communications},
note = {},
key = {},
abstract = {The use of switched Ethernet for precise and safe real-time communication still suffers from undesired phenomena, such as blocking caused by long non-preemptive frames, lack of protection against errors in the time domain, couplings across virtual LANs and priority levels via internal switch shared resources. Recently, a few solutions were proposed to cope with such phenomena. One such solution is based on an enhanced switch following the Flexible Time-Triggered paradigm, which enforces strict service differentiation, blocking-free forwarding and timing errors confinement. In this paper we propose a new architecture following an hardware-software co-design approach that facilitates the development of the enhanced switch features by separating the traffic scheduling from the common management activities associated to switching}
}
@inproceedings{MARAU_CRTS_2008,
author = {Marau, R. and Figueiredo, N. and Santos, R. and Pedreiras, P. and Almeida, L. and Nolte, T.},
title = {Server-based real-time communications on Switched Ethernet},
booktitle = {1st Workshop on Compositional Theory and Technology for Real-Time Embedded Systems (CRTS'2008) Proceedings},
year = {2008},
editor = {},
volume = {},
series = {},
pages = {37--44},
address = {Barcelon, Spain},
month = {November},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Ethernet, Real-Time communications, FTT, FTT-SE, protocols},
note = {},
key = {},
abstract = {Real-Time Ethernet (RTE) protocols have difficulties in the efficient handling of aperiodic message streams with arbitrary arrival patterns, while at the same time supporting the derivation of timeliness guarantees. This paper presents a server-based mechanism for switched Ethernet real-time networks, integrating concepts from the Server-CAN protocol on the FTT-SE protocol. This approach enables an efficient implementation of arbitrary server schedulers as well as their hierarchical composition. Moreover, the presented approach is very suitable for open systems as servers can easily be added, changed and removed during runtime. The paper includes a case study based on a distributed control application. The obtained results illustrate the correct operation of the server-based protocol, showing the capability of the framework in providing strict timeliness guarantees to the real-time traffic in spite of interference with arbitrary arrival patterns and load variations}
}
@inproceedings{MARAU_ECRTS_2008,
author = {Marau, R. and Almeida, L. and Pedreiras, P. and Nolte, T.},
title = {Towards Server-based Switched Ethernet for Real-Time Communications},
booktitle = {20th Conference on Real-Time Systems (ECRTS'2008) WiP Session Proceedings},
year = {2008},
editor = {},
volume = {},
series = {},
pages = {60--63},
address = {Prague, Czech Republic},
month = {July},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Ethernet, FTT, FTT-SE, Real-Time communications, Server-CAN, protocols},
note = {},
key = {},
abstract = {This paper presents work-in-progress on server-based Switched Ethernet (SE) for real-time communications. It joins the recent FTT-SE protocol with concepts from the Server-CAN protocol to allow handling aperiodic message streams with arbitrary arrival patterns while supporting the derivation of timeliness guarantees. The presented approach enables an efficient implementation of arbitrary server schedulers in the switch, and a number of server schedulers are to be investigated with respect to SE performance. Moreover, the presented approach is very suitable for open systems as servers can easily be added, changed and removed during runtime of the switch. Currently, several server-based policies are being implemented, which will allow carrying out comparisons among different policies as well as verifying the capability of the protocol for on-line integrated management of the servers}
}
@inproceedings{SANTOS_WFCS_2008,
author = {Santos, R. and Marau, R. and Oliveira, A. and Pedreiras, P. and Almeida, L.},
title = {Designing a costumized Ethernet switch for safe hard real-time communication},
booktitle = {7th IEEE International Workshop on Factory Communication Systems (WFCS'2008) Proceedings},
year = {2008},
editor = {},
volume = {},
series = {},
pages = {169--177},
address = {Dresden, Germany},
month = {May},
organization = {},
publisher = {},
doi = {10.1109/WFCS.2008.4638737},
issn = {},
isbn = {},
keywords = {FPGA, Ethernet, Real-Time communications, FTT, Switch},
note = {},
key = {},
abstract = {The use of switched Ethernet for precise and safe real-time communication still suffers from undesired phenomena that range from the blocking caused by long non-preemptive frames to lack of protection against errors in the time domain and also couplings across virtual LANs and even priority levels via internal switch shared resources. In this paper we propose a novel switch architecture enhanced with resource reservation mechanisms, based on the Flexible Time-Triggered paradigm, which enforces strict service differentiation, blocking-free forwarding and timing errors confinement. Experimental results of a preliminary 4-port prototype based on an FPGA validate the desired properties and exhibit the potential of the enhanced Ethernet switch}
}
@inbook{MARAU_DAES_2007,
author = {Marau, R. and Silva, V. and Ferreira, J. and Almeida, L. and Pedreiras, P. and Martins, E. and Fonseca, J. A.},
title = {Distributed Automotive Embedded Systems},
chapter = {Assessment of FTT-CAN master replication mechanisms for safety-critical applications},
pages = {},
publisher = {SAE International},
year = {2007},
volume = {},
series = {},
type = {},
address = {},
edition = {},
month = {November},
doi = {},
issn = {},
isbn = {978-0-7680-1966-7},
keywords = {FTT, FTT-CAN, CAN, Real-Time communications, protocols, Embedded systems},
note = {},
key = {},
abstract = {The operational flexibility of distributed embedded systems is receiving growing attention because it is required to support on-line adaptation to varying operational conditions, either due to changes in the environment or to faults in the system. However, flexibility makes dependability more difficult to achieve, because there is less a priori knowledge. One protocol that favors flexibility and is widely used in embedded systems, particularly in automotive and robotic systems, is CAN, but some claim that it is not adequate to support safety-critical applications. We argue that CAN, deployed with an adequate overlay protocol, can provide the required support for dependability and flexibility. One such overlying protocol is Flexible Time-Triggered CAN (FTTCAN), that enforces a global notion of time and a global periodic schedule by means of specific messages issued by a master node. In this paper we assess the FTT-CAN master replication mechanisms implemented in a distributed robot control system. Above all, we provide experimental results that show the robustness of such mechanisms}
}
@inproceedings{MARAU_ETFA_2007,
author = {Marau, R. and Almeida, L. and Pedreiras, P. and Harbour, M. and Sangorrin, D. and Medina, J.L.},
title = {Integration of a flexible time triggered network in the FRESCOR resource contracting framework},
booktitle = {12th IEEE Conference on Emerging Technologies and Factory Automation (ETFA'2007) Proceedings},
year = {2007},
editor = {},
volume = {},
series = {},
pages = {1481--1488},
address = {Patras, Greece},
month = {September},
organization = {},
publisher = {},
doi = {10.1109/EFTA.2007.4416964},
issn = {},
isbn = {978-1-4244-0826-9},
keywords = {FRESCOR, Ethernet, FTT, FTT-SE},
note = {},
key = {},
abstract = {In this paper we overview the integration of a framework that generic ally manages the system resources in the form of contracts, namely the FRESCOR framework, with a flexible network resource. We describe how a network resource, namely FTT-SE, supports the FRESCOR framework services and, likewise, how the network services are made available to the application through the contracting framework. In a designer perspective, we also describe how a typical distributed application can be easily deployed using such a framework}
}
@inproceedings{SILVESTRE_ETFA_2007,
author = {Silvestre, J. and Almeida, L. and Marau, R. and Pedreiras, P.},
title = {Dynamic QoS management for multimedia real-time transmission in industrial environments},
booktitle = {12th IEEE Conference on Emerging Technologies and Factory Automation (ETFA'2007) Proceedings},
year = {2007},
editor = {},
volume = {},
series = {},
pages = {1473--1480},
address = {Patras, Greece},
month = {September},
organization = {},
publisher = {},
doi = {10.1109/EFTA.2007.4416963},
issn = {},
isbn = {978-1-4244-0826-9},
keywords = {FTT-SE, Ethernet, JPEG quantification factor, MJPEG transmission, Bandwidth, Compressors, Condition monitoring, Environmental management, Ethernet, Interference constraints, Machine vision, Protocols, Time factors, Video compression},
note = {},
key = {},
abstract = {The use of multimedia within industrial applications has become commonplace, targetting improved process monitoring and machine vision. In both cases, the multimedia information is commonly distributed and subject to time constraints that must be met across networks while avoiding untolerable interference over typical control flows. This can be achieved with Constant Bit-Rate (CBR) channels, typically supported by real-time protocols. However, the compressors used to reduce the amount of information to transfer generate Variable Bit-Rate (VBR) patterns. Adapting a VBR source to a CBR channel requires specific care in order to avoid wasting channel bandwidth or dropping video frames. This paper focuses on MJPEG transmission over Ethernet and proposes a bidimensional adaptation using the JPEG quantification factor q on the source side and frame acquisition/transmission period T on the source/network side respectively, using the FTT-SE protocol and its support for dynamic QoS management. The paper also shows several experiments with pre-recorded video streams that illustrate the advantages of the proposed approach}
}
@inproceedings{MARAU_RTN_2007,
author = {Marau, R. and Pedreiras, P. and Almeida, L.},
title = {Asynchronous traffic signaling over master-slave switched ethernet protocols},
booktitle = {6th International Workshop on Real-Time Networks (RTN'2007) Proceedings},
year = {2007},
editor = {},
volume = {},
series = {},
pages = {},
address = {Pisa, Italy},
month = {July},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Ethernet, FTT, FTT-SE, Real-Time communications, master-slave, protocols },
note = {},
key = {},
abstract = {Network protocol designers have always been divided between the adoption of centralized or distributed communication architectures. Despite exhibiting negative aspects like the existence of a single point-of-failure in the master as well as computational overhead and an inefficient handling of the asynchronous communications, Master-Slave protocols have always found their space mainly given their simplicity of operation and deployment as well as good control over the communication medium. Along the years, many protocols based in this paradigm have been proposed, with many of them being still used today. Some of the negative aspects traditionally exhibited by these protocols have also been attenuated, e.g. with master replication and master/multi-slave control, but the handling of asynchronous requests is still a limitation concerning the response time and overhead. In this paper, we address the specific case of micro-segmented switched Ethernet networks, where Master-Slave protocols are used to control the load submitted to the switch and prevent high queuing jitter and memory overflows. Particularly, we propose a novel signaling mechanism that reduces the asynchronous traffic response time and network overhead, by exploiting the full duplex channels, and analyze the integration of this mechanism in the FTT-SE and Ethernet Powerlink protocols}
}
@inproceedings{MARAU_RTAS_2007,
author = {Marau, R. and Almeida, L. and Pedreiras, P. and Harbour, M. and Sangorrin, D. and Medina, J.L.},
title = {Integration of a flexible network in a resource contracting framework},
booktitle = {13th IEEE Real-Time and Embedded Applications Symposium (RTAS'2007) WiP Session Proceedings},
year = {2007},
editor = {},
volume = {},
series = {},
pages = {},
address = {Bellevue, USA},
month = {April},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Ethernet, FTT, FTT-SE, FRESCOR, protocols},
note = {},
key = {},
abstract = {In this paper we overview the integration of a framework that generically manages the system resources in the form of contracts, namely the FRESCOR framework, with a ?exible network resource. We describe how a network resource, namely FTT-SE, supports the FRESCOR framework services and, likewise, how the network services are made available to the application through the contracting framework.}
}
@inbook{ALMEIDA_HRTES_2007,
author = {Almeida, L. and Pedreiras, P. and Ferreira, J. and Calha, J. and Fonseca, J. A. and Marau, R. and Silva, R. and Martins, E.},
title = {Handbook of Real-Time and Embedded Systems},
chapter = {Online QoS Adaptation with the Flexible Time-Triggered (FTT) Communication Paradigm},
pages = {},
publisher = {Chapman and Hall/CRC},
year = {2007},
volume = {},
series = {},
type = {},
address = {},
edition = {},
month = {},
doi = {},
issn = {},
isbn = {978-1-58488-678-5},
keywords = {Ethernet, FTT, FTT-SE, Real-Time communications},
note = {},
key = {},
abstract = {}
}
@article{ALMEIDA_MDRMDES_2006,
author = {Almeida, L. and Pedreiras, P. and Marau, R.},
title = {Traffic scheduling anomalies in temporal partitions},
journal = {From Model-driven Design To Resource Management For Distributed Embedded Systems},
year = {2006},
volume = {225},
number = {},
pages = {95--104},
month = {October},
doi = {},
issn = {},
isbn = {978-0-387-39361-2},
keywords = {Real-Time, TDMA},
note = {},
key = {},
abstract = {Many network protocols rely on temporal partitions to provide isolation between different nodes (TDMA slots) or different traffic classes (multi-phase cyclic frameworks). Typically, the duration of the slots or phases is not correlated with the duration of packet transmissions, which is variable and non-preemptive. Thus, it is possible that the limit of the slot or phase be overrun by an on-going packet transmission or, if this cannot be tolerated, idle-time must be inserted at the end of the slot or phase whenever a packet does not fit in. Nevertheless, both situations lead to scheduling anomalies in which the worst-case network delay does not occur necessarily with the synchronous release of all other packets, or just the higher priority ones. This paper highlights two such anomalies showing their origin and indicating that, in such circumstances, it is not possible to determine the worst-case network delay with exactitude in the general case. However, it is still possible to upper bound the network delay and the paper shows non-optimal solutions for those cases}
}
@inproceedings{MARAU_RTN_2006,
author = {Marau, R. and Almeida, L. and Pedreiras, P.},
title = {Enhanced Ethernet Switching for Flexible Hard Real-Time Communication},
booktitle = {5th International Workshop on Real Time Networks (RTN'2006) Proceedings},
year = {2006},
editor = {},
volume = {},
series = {},
pages = {},
address = {Dresden, Germany},
month = {July},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {FTT, FTT-SE, Ethernet, Real-Time Communication},
note = {},
key = {},
abstract = {Switched Ethernet arose in the last decade as a means to increase global throughput with parallel switching paths, segment the network and create isolated collision domains, thus reducing the non determinism of the original shared Ethernet. However the services provided by COTS Ethernet switches are not enough to guarantee real-time communication, which lead to the development of several switch Ethernet-based protocols, among which the recently proposed FTT-SE. This paper proposes moving the FTT traffic management into the Ethernet switch and discusses how this architectural change enhances the performance of the transmission control and service differentiation mechanisms as well as how error confinement mechanisms can be efficiently deployed. Preliminary experimental results from a prototype implementation validate the services provided by the enhanced Ethernet switch framework}
}
@inproceedings{MARAU_WFCS_2006,
author = {Marau, R. and Almeida, L. and Pedreiras, P.},
title = {Enhancing real-time communication over COTS ethernet switches},
booktitle = {6th IEEE International Workshop on Factory Communication Systems (WFCS'2006) Proceedings},
year = {2006},
editor = {},
volume = {},
series = {},
pages = {295--302 },
address = {Torino, Italy},
month = {June},
organization = {},
publisher = {},
doi = {10.1109/WFCS.2006.1704170},
issn = {},
isbn = {1-4244-0379-0},
keywords = {Ethernet, Real-Time, Communication switching, Delay, Ethernet networks, Job shop scheduling, Multi-access communication, Multicast protocols, Switches, Telecommunication traffic, Throughput, Traffic control},
note = {},
key = {},
abstract = {Switched Ethernet arose in the last decade as a means to increase global throughput with parallel switching paths, segment the network and create isolated collision domains, thus reducing the non determinism of the original shared Ethernet. However, COTS Ethernet switches still suffer from a few drawbacks that affect negatively their real-time communication capabilities. For example, there can be overflows in ports queues with consequences across ports, priority levels and virtual LANs, and the number of priorities is too short for any kind of priority-based scheduling. Moreover, switches present extra latencies and jitter due to the need to interpret frame addresses and also due to different internal architectural solutions. In this paper we propose using the Flexible Time-Triggered communication paradigm to enhance the temporal behavior of Ethernet switches with respect to periodic streams. We explain the system architecture and we present a formulation of the global periodic traffic scheduling problem handled by the FTT master. Simulation and experimental results show the advantages of using such synchronized framework}
}
@article{MARAU_SAE_2006,
author = {Marau, R. and Almeida, L. and Fonseca, J. A. and Ferreira, J. and Silva, V.},
title = {Assessment of FTT-CAN master replication mechanisms for safety-critical applications},
journal = {SAE 2006 Transactions Journal of Passenger Cars: Electronic and Electrical Systems},
year = {2006},
volume = {},
number = {},
pages = {},
month = {April},
doi = {10.4271/2006-01-1024},
issn = {},
isbn = {},
keywords = {CAN, FTT, FTT-CAN, Real-Time communications, Embedded systems, protocols},
note = {E XTRA-INFO-OPTIONAL},
key = {KEY-OPTIONAL},
abstract = {The operational flexibility of distributed embedded systems is receiving growing attention because it is required to support on-line adaptation to varying operational conditions, either due to changes in the environment or to faults in the system. However, flexibility makes dependability more difficult to achieve, because there is less a priori knowledge. One protocol that favors flexibility and is widely used in embedded systems, particularly in automotive and robotic systems, is CAN, but some claim that it is not adequate to support safety-critical applications. We argue that CAN, deployed with an adequate overlay protocol, can provide the required support for dependability and flexibility. One such overlying protocol is Flexible Time-Triggered CAN (FTTCAN), that enforces a global notion of time and a global periodic schedule by means of specific messages issued by a master node. In this paper we assess the FTT-CAN master replication mechanisms implemented in a distributed robot control system. Above all, we provide experimental results that show the robustness of such mechanisms}
}
@inproceedings{SILVA_ETFA_2005,
author = {Silva, V. and Marau, R. and Almeida, L. and Ferreira, J. and Calha, M. and Pedreiras, P. and Fonseca, J. A.},
title = {Implementing a distributed sensing and actuation system: The CAMBADA robots case study},
booktitle = {10th IEEE Conference on Emerging Technologies and Factory Automation (ETFA'2005) Proceedings},
year = {2005},
editor = {},
volume = {2},
series = {},
pages = {781--788},
address = {Catania, Italy},
month = {September},
organization = {},
publisher = {},
doi = {10.1109/ETFA.2005.1612753},
issn = {},
isbn = {0-7803-9401-1},
keywords = {CAN, FTT-CAN, CAMBADA, controller area network, distributed actuation system, distributed computing architecture, distributed embedded system, distributed sensing system, mobile autonomous robotics},
note = {},
key = {},
abstract = {The use of distributed computing architectures has become commonplace in complex embedded systems with potential advantages, for example, in terms of scalability, dependability and maintainability. One particular area in which that trend can be witnessed is mobile autonomous robotics in which several sensors and actuators are interconnected by means of a control network. In this paper we address one case study concerning the CAMBADA robots that were developed at the University of Aveiro for the Robocup Middle Size League. These robots have a distributed architecture with two layers, a coordination layer responsible for the global behaviors and a distributed sensing and actuating layer that conveys internal state information and executes coordination commands. This paper focuses on the latter layer, which is based on the FTT-CAN protocol, following a network-centric approach that provides an efficient framework for the synchronization of all systems activities. We describe the computing and communication requirements, the robot architecture, the system design and implementation, and finally we provide experimental results that show advantages with respect to a non-synchronized distributed approach}
}