Selfish Optimization in Computer Networks

This paper describes two applications of decentralized (Pareto) optimization to problems of computer communication networks. The first application is to develop a generalized principle for optimality of multi-hop broadcast channel access schemes. The second application is to decentralized flow-control in fixed virtual-circuit networks (e.g., SNA) using power maximization as the performance index. The decentralized approach to optimum network behavior yields, among other results, characterization of fair global objective functions, and optimal decentralized greedy network control algorithms. The main conclusion of this paper is that Pareto-optimality methods can be successfully used to develop optimal decentralized behavior algorithms where a centralized approach is (sometimes provably) not applicable

A Statistical Mechanics of Some Interconnection Networks

Despite intensive research on distributed processor interconnection architectures, relatively little work has been done on the performance analysis of such systems. The reason for this, besides the complexity of the behavior of such systems, is that Queueing Theory cannot easily handle systems consisting of many tightly interacting components. An alternate approach, based upon statistical mechanics, is used. We analyze interconnection structures such as crossbar, linear array, binary tree and ring

Experience-Based Decisions and Brain Activity: Three New Gaps and Partial Answers

Experience-based decisions can be defined as decisions emanating from direct or vicarious reinforcements that were received in the past. Typically, in experience-based decision tasks an agent repeatedly makes choices and receives outcomes from the available alternatives, so that choices are based on past experiences, with no explicit description of the payoff distributions from which the outcomes are drawn. The study of experience-based decisions has long roots in the works of mathematical psychologists during the 1950s and 1960s of the last century (e.g., Estes and Burke, 1953; Bush and Mosteller, 1955; Katz, 1964). This type o

CUPID: A Protocol Development Environment

This paper describes research conducted towards Columbia's unified Protocol Implementation and Design (CUPID) environment. CUPID research aims at the integration and automation of protocol design and implementation tools. CUPID uses an algebraic representation of protocols based, in part, upon a variant of Milner's calculus of communicating systems (CCS). Communication behaviors are represented in terms of expressions of a universal algebra. A key notion to the automation of protocol development functions is that of a valuation over the algebra of communication behaviors. A valuation maps communication behaviors to expressions in other algebras (e.g., an algebra of delay distributions used for performance analysis). This allows one to proceed and compute attributes of communication behaviors over the respective algebras using a formal valuation process. We provide a brief introduction to CCS in the context of modelling protocol behaviors. This is followed by a brief summary of how the algebraic valuation mechanism may be used to support the different functions of a protocol design environment: multiple concurrent specifications, automated functional and performance analysis and automated test generation and performance simulation

Protocols for Loosely Synchronous Networks

This paper overviews a novel transfer mode for B-ISDN: Loosely-synchronous Transfer Mode (LTM). LTM operates by signaling periphery nodes when destinations become available. No frame structure is imposed by LTM, thus avoiding adaptation layers. Additionally, LTM can deliver a spectrum of guaranteed quality of services. New Synchronous Protocol Stacks (SPSs) build on LTM by synchronizing their activities to LTM signals. Such signals can be delivered directly to applications that may synchronize its operations to transmissions, thus minimizing buffering due to synchronization mismatches. SPSs can use current transport protocols unchanged and, potentially, enhance them with the real-time capabilities made possible through LTM

The Gigabit per Second Isochronet Switch

This paper overviews the electronic and all-optical design and the gigabit per second electronic implementation of a switch based on the Isochronets highspeed network architecture. The absence of frame processing in the Isochronets architecture is core to the switch efficiency and multi-protocol support. The electronic design is low cost and uses simple off-the-shelf components, while the optical design can be realized with current optical devices. The switch interface is simple and provides novel services such as propagation of synchronization signals to upper protocol layers. The switch makes it possible the negotiation of Quality of Service (QoS) while promoting flexible resource sharing. The modular switch designs are scaleable in number of nodes and link speed. Using faster implementation technology, the electronic design can reach scores of gigabits per second, while the all-optical design can potentially operate at terabits per second

To Take Risk is to Face Loss: A Tonic Pupillometry Study

The construct of risk taking is studied through the prism of the relation between tonic arousal and risk taking behavior. Several theories have proposed that high aroused individuals tend to exhibit risk aversion. We posit that this arousal–behavior association is activated much more strongly in risks with losses, as losses increase arousal and trigger relevant traits associated with the sensitivity to risk. In three studies we examined risk taking in experience-based decision tasks, with either token losses or relative-losses (in the gain domain). In Study 1 we found a negative correlation between pre-task pupil diameter and risk taking in the loss domain but not in the gain domain. In Study 2 we re-analyzed a previous pupillometry dataset involving symmetric mixed gains and losses. We found that the negative correlation in this mixed condition emerged even while the participants did not show loss aversion. This finding was replicated in Study 3. Thus, the effect of losses on arousal provides sufficient conditions for the moderation of the tonic arousal–behavior association. The findings suggest an important role for losses in the psychological and physiological experience of risk

An Overview of the Isochronets Architecture for High Speed Networks

This paper overviews a novel switching architecture for high-speed networks: Isochronets. Isochronets time-divide network bandwidth among routing trees. Traffic moves down a routing tree to the root during its time band. Network functions such as routing and flow control are entirely governed by band timers and require no processing of frame headers bits. Frame motions need not be delayed for switch processing, allowing Isochronets to scale over a large spectrum of transmission speeds and support all-optical implementations. The network functions as a media-access layer that can support multiple framing protocols simultaneously, handled by higher layers at the periphery. Internetworking is reduced to a simple media-layer bridging. Isochronets provide flexible quality of service control and multicasting through allocation of bands to routing trees. They can be tuned to span a spectrum of performance behaviors outperforming both circuit or packet switching

Management of Application Quality of Service

This paper proposes a new language for the development of distributed multimedia applications: Quality Assurance Language (QuAL). QuAL abstractions allow the specification of Quality of Service (QoS) constraints expected from the underlying computing and communication environment. QuAL specifications are compiled into run time components that monitor the actual QoS delivered. Upon QoS violations, application provided exception handlers are signaled to act upon the faulty events. Language level abstractions of QoS shelter programs from the heterogeneity of underlying infrastructures. This simplifies the development and maintenance of multimedia applications and promotes their portability and reuse. QuAL generates Management Information Bases (MIBs) that contain QoS statistics per application. Such MIBs may be used to integrate application level QoS management into standard network management frameworks

Active Databases for Communication Network Management

This paper has two purposes. First is to propose new database language-features for systems used in real-time management. These features enable the specification of change-traces, events and correlation among events, and they do so in a declarative set-oriented fashion. Second is to introduce network management as an important and interesting application of active distributed databases