FTT-SE.bib
@inproceedings{ASHJAEI_WCTT_2012,
author = {Ashjaei, M. and Liu, M. and Behnam, M. and Mifdaoui, A. and Almeida, L. and Nolte, T.},
title = {Worst-Case Delay Analysis of Master-Slave Switched Ethernet Networks},
booktitle = {2nd International Workshop on Worst-Case Traversal Time (WCTT'2012) Proceedings},
year = {2012},
editor = {},
volume = {},
series = {},
pages = {},
address = {San Juan, Puerto Rico},
month = {December},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Ethernet, FTT, FTT-SE, Real-Time communications},
note = {},
key = {},
abstract = {Switched Ethernet is increasingly used in real-time communication due to its intrinsic features such as micro segmentation and high throughput. However, COTS switches may impose long blocking times due to their FIFO queues and can also experience buffer overflow in outgoing queues due to uncontrolled packets arrival. Reconciling the use of ordinary switches with the needs of real-time communication requires an adequate overlay protocol. In this paper we focus on using a Master-Slave technique to overcome the COTS switch limitations in real-time applications, namely the FTT-SE protocol. We extend the protocol for large scale networks and we present the worst-case delay analysis using the Network Calculus formalism for such a network. Moreover, we assess the end-to-end delay of traffic with simulation}
}
@inproceedings{NOGUERO_UCAMI_2012,
author = {Noguero, A. and Calvo, I. and Almeida, L.},
title = {A time-triggered middleware architecture for ubiquitous cyber physical system applications},
booktitle = {6th International Conference on Ubiquitous Computing and Ambient Intelligence (UCAmI'2012) Proceedings},
year = {2012},
editor = {},
volume = {},
series = {},
pages = {73--80},
address = {Vitoria-Gasteiz, Spain},
month = {December},
organization = {},
publisher = {},
doi = {10.1007/978-3-642-35377-2_10},
issn = {},
isbn = {978-3-642-35376-5},
keywords = {Real-Time communications, Cyber physical systems, CPS, middleware, iLAND},
note = {},
key = {},
abstract = {Cyber Physical Systems (CPS) are a special type of ubiquitous systems where control theory, communications and real-time computing are combined in embedded applications that interact with the physical world. The development of these applications becomes more complex when real-time and other non-functional requirements are to be satisfied. This paper presents a time-triggered middleware architecture that provides fault tolerance and dynamic reconfiguration at run-time taking into account the available resources of the underlying infrastructure, i.e. devices and communication networks. This architecture aims at easing the development of ubiquitous applications based on CPS. The paper provides an overview of the design of the architecture and discusses some implementation issues}
}
@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{ASHJAEI_WFCSWIP_2012,
author = {Ashjaei, M. and Behnam, M. and Nolte, T. and Almeida, L.},
title = {Extending FTT-SE protocol for Multi-Master/Multi-Slave Networks},
booktitle = {9th IEEE International Workshop on Factory Communication Systems (WFCS'2012) WiP Session Proceedings},
year = {2012},
editor = {},
volume = {},
series = {},
pages = {},
address = {Lemgo, Germany},
month = {May},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Real-Time communications, FTT, Ethernet, FTT-SE},
note = {},
key = {},
abstract = {}
}
@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}
}
@inproceedings{YEKEH_SIES_2011,
author = {Yekeh, F. and Pordel, M. and Almeida, L. and Behnam, M. and Portugal, P.},
title = {Exploring alternatives to scale FTT-SE to large networks},
booktitle = {6th IEEE International Symposium on Industrial Embedded Systems (SIES'2011) Proceedings},
year = {2011},
editor = {},
volume = {},
series = {},
pages = {},
address = {Vasteras, Sweden},
month = {June},
organization = {},
publisher = {},
doi = {10.1109/SIES.2011.5953692},
issn = {},
isbn = {978-1-61284-819-8},
keywords = {Real-Time communications, FTT, FTT-SE, Ethernet, Embedded systems},
note = {},
key = {},
abstract = {Nowadays, most complex embedded systems follow a distributed approach in which a network interconnects potentially large numbers of nodes. One technology that is being increasingly used is switched Ethernet, but real-time variants of this protocol typically limit scalability. In this paper, we focus on the scalability of the Flexible Time Triggered communication over Switched Ethernet (FTT-SE), which has been proposed to support hard real-time applications in a flexible and predictable manner. Moreover, time-triggered and event-triggered communication methods are supported in this protocol. FTT-SE has already been explored and investigated for small scale networked applications. In this paper we address the protocol scalability and suggest three different solutions with a qualitative assessment}
}
@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_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{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{ANTUNES_INDIN_2007,
author = {Antunes, A. and Pedreiras, P. and Almeida, L. and Mota, A.},
title = {Dynamic Rate and Control Adaptation in Networked Control Systems},
booktitle = {5th IEEE International Conference on Industrial Informatics (INDIN'2007) Proceedings},
year = {2007},
editor = {},
volume = {2},
series = {},
pages = {841--846},
address = {Vienna, Austria},
month = {July},
organization = {},
publisher = {},
doi = {10.1109/INDIN.2007.4384883},
issn = {1935-4576},
isbn = {978-1-4244-0851-1},
keywords = {Real-Time systems, Embedded systems, distributed control system, distributed feedback control loop system, dynamic rate adaptation technique, embedded control system, networked control system, operational flexibility, sampling period},
note = {},
key = {},
abstract = {Modern embedded control systems are asked to exhibit higher distribution, higher degree of integration and to support operational flexibility. Conventionally the planning of distributed control systems was done either by considering worst-case requirements, leading to expensive and inefficient designs, or by considering average requirements, potentially leading to occasional run-time overloads. The dynamic rate adaptation technique was developed to support operational flexibility and a higher degree of integration in distributed control systems. This technique adapts the communication requirements of distributed feedback control loops by increasing the sampling periods of the messages associated to the control action in order to free network bandwidth when a possible network overload condition is detected. The distributed controllers have to be able to deal with the change of the sampling period and the variable sampling to actuation delay. This work reports different control approaches used in the implementation of the dynamic rate adaptation method, namely a static version based on a set of controllers with parameters pre-computed off-line, a dynamic version where the system parameters are identified online according to the dynamic behaviour of the distributed system and a hybrid version using an adaptive controller with a set of online identifiers}
}
@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}
}
@inproceedings{ALMEIDA_RTSS_2005,
author = {Almeida, L. and Pedreiras, P.},
title = {Hard Real-Time Communication over COTS Ethernet Switches},
booktitle = {26th IEEE International Real-Time Systems Symposium (RTSS'2005) Work in Progress Session Proceedings},
year = {2005},
editor = {},
volume = {},
series = {},
pages = {},
address = {Miami Florida, USA},
month = {December},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Ethernet, FTT, FTT-SE},
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 original shared Ethernet. However, the use of switches, just by itself, is not enough to provide the adequate support to hard real-time communication. For example, there can be overflows in ports queues 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 frames 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 an early formulation of the global periodic traffic scheduling problem that must be handled by the FTT master}
}
@inproceedings{PEDREIRAS_RTLIA_2003,
author = {Pedreiras, P. and Leite, R. and Almeida, L.},
title = {Characterizing the Real-Time Behavior of Prioritized Switched-Ethernet},
booktitle = {2nd International Workshop on Real-Time LANs in the Internet Age (RTLIA'2003) Proceedings},
year = {2003},
editor = {},
volume = {},
series = {},
pages = {},
address = {Oporto, Portugal},
month = {July},
organization = {},
publisher = {},
doi = {},
issn = {},
isbn = {},
keywords = {Ethernet},
note = {},
key = {},
abstract = {Ethernet is, today, the de facto standard in the Local Area Networks general domain. Despite having been designed for the office environment, it has been appropriately modified or adapted in order to fulfill the requirements of many other fields, including large distributed embedded systems and industrial automation. One typical requirement in such application fields is the need to deliver time-constrained communication services, which cannot be efficiently met using the original CSMA/CD medium access control. Among many possible solutions, either software or hardware-based, the one that became more popular, recently, is the use of switches. However, this does not enforce timeliness per se. In this paper we show a set of practical experiments that reveal the weaknesses of switched Ethernet in what concerns real-time behavior. The results point to the need for further traffic control, at the data sources, if a predictable behavior of the switch is desired}
}