The timely computing base: Timely actions in the presence of uncertain timeliness

Verı́ssimo, Paulo; Casimiro, António; Fetzer, Christof

doi:10.1109/icdsn.2000.857587

Cited by 43 publications

(38 citation statements)

References 10 publications

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“…We are also not aware of any real-time security kernel. The TTCB builds on the Timely Computing Base work [19]. The objective of this distributed component it to assist the implementation of timed operations and to detect timing failures.…”

Section: Related Workmentioning

confidence: 99%

The Design of a COTS Real-Time Distributed Security Kernel

Correia

Verı́ssimo

Neves

2002

Dependable Computing EDCC-4

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Abstract. This paper describes the design of a security kernel called TTCB, which has innovative features. Firstly, it is a distributed subsystem with its own secure network. Secondly, the TTCB is real-time, that is, a synchronous subsystem capable of timely behavior. These two characteristics together are uncommon in security kernels. Thirdly, the TTCB can be implemented using only COTS components. We discuss essentially three things in this paper: (1) The TTCB is a simple component providing a small set of basic secure services. It aims at building a new style of protocols to achieve intrusion tolerance, which for the most part execute in insecure, arbitrary failure environments, and resort to the TTCB only in crucial parts of their operation. (2) Besides, the TTCB is a synchronous device supplying functions that may be an enabler of a new generation of timed secure protocols, until now known to be fragile due to attacks on timing assumptions. (3) Finally, we present a design methodology that establishes our hybrid failure assumptions in a well-founded manner. It helps us to achieve a robust design, despite using exclusively COTS components, with the advantage of allowing the security kernel to be easily deployed on widely used platforms.

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Section: Related Workmentioning

confidence: 99%

The Design of a COTS Real-Time Distributed Security Kernel

Correia

Verı́ssimo

Neves

2002

Dependable Computing EDCC-4

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“…Unfortunately, given the difficulty of ensuring that stipulated bounds on computation times and transmission delays are always met (which is notoriously difficult with many systems, especially those built out of COTS products), the safety/liveness/timeliness properties achieved with such systems may have a poor coverage. This holds true for any design that rests upon (some) timed semantics, including timed asynchronous systems [28] and the Timely Computing Base [29]. With such solutions, the core questions are: How do you set your timers?…”

Section: Discussionmentioning

confidence: 99%

Failure Detection with Booting in Partially Synchronous Systems

Widder

Lann

Schmid

2005

Dependable Computing - EDCC 5

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Abstract. Unreliable failure detectors are a well known means to enrich asynchronous distributed systems with time-free semantics that allow to solve consensus in the presence of crash failures. Implementing unreliable failure detectors requires a system that provides some synchrony, typically an upper bound on end-to-end message delays. Recently, we introduced an implementation of the perfect failure detector in a novel partially synchronous model, referred to as the Θ-Model, where only the ratio Θ of maximum vs. minimum end-to-end delay of messages that are simultaneously in transit must be known a priori (while the actual delays need not be known and not even be bounded). In this paper, we present an alternative failure detector algorithm, which is based on a clock synchronization algorithm for the Θ-Model. It not only surpasses our first implementation with respect to failure detection time, but also works during the system booting phase.

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“…This is somewhat disappointing since even perfect failure detectors are very hard to implement in practice. However, ordered perfect failure detectors can still be implemented using a timely computing base [19]. In such an approach, an asynchronous network is enhanced by a synchronous real-time control network (see Figure 11).…”

Section: ¡ £mentioning

confidence: 99%

(Im)Possibilities of Predicate Detection in Crash-Affected Systems

Gärtner

Pleisch

2001

Lecture Notes in Computer Science

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In an asynchronous system, where processes can crash, perfect predicate detection for general predicates is difficult to achieve. A general predicate thereby is of the form ¢ ¡ ¤ £, where and £ refer to a normal process variable and to the operational state of that process, respectively. Indeed, the accuracy of predicate detection largely depends on the quality of failure detection. In this paper, we investigate the predicate detection semantics that are achievable for general predicates using either failure detector classes, or¨. For this purpose, we introduce weaker variants of the predicate detection problem, which we call stabilizing and infinitely often accurate. We show that perfect predicate detection is impossible using the aforementioned failure detectors. Rather, ¦ and¨only allow stabilizing predicate detection. Consequently, we explore alternative approaches to perfect predicate detection: introducing a stronger failure detector, called ordered perfect, or restricting the general nature of predicates.

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The timely computing base: Timely actions in the presence of uncertain timeliness

Cited by 43 publications

References 10 publications

The Design of a COTS Real-Time Distributed Security Kernel

The Design of a COTS Real-Time Distributed Security Kernel

Failure Detection with Booting in Partially Synchronous Systems

(Im)Possibilities of Predicate Detection in Crash-Affected Systems

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