To the memory of my father, Dr. Leon Roberto Arango Garrido (1915-1978), my sole inspiration in b... more To the memory of my father, Dr. Leon Roberto Arango Garrido (1915-1978), my sole inspiration in becoming a man of science.
Stephen Pink received a Bachelor's degree from the University of Minnesota, a Master's de... more Stephen Pink received a Bachelor's degree from the University of Minnesota, a Master's degree from Cornell University and a PhD from the Royal Institute of Technology in Sweden. He is the manager of the Computer and Network Architecture research group at the Swedish Institute of Computer Science and a Professor of Computer Science and Engineering at Luieä University in Sweden. His major interests are in protocol design, high speed and wireless networking, multimedia, and distributed operating systems.
Toxic trace element pollutants present in the raw product gas and raw flue gas streams produced d... more Toxic trace element pollutants present in the raw product gas and raw flue gas streams produced during the gasification of coal or similar carbonaceous solids containing sulfur and such trace elements are recovered by separately scrubbing the product gas and flue gas with water, combining the resulting aqueous effluents, and removing the pollutants from the combined aqueous stream as insoluble metal sulfides.
A key characteristic of mobile computing is that the end systems involved can experience differin... more A key characteristic of mobile computing is that the end systems involved can experience differing degrees of connectivity during typical operational cycles. This paper discusses the issues associated with developing distributed system services to operate in such an environment. We focus on the provision of file system support and argue that existing file systems, including those developed for use in a mobile environment, contain assumptions about their underlying communications infrastructures which are unlikely to hold in a mobile environment. This argument is supported by an in-depth examination of a specific file system issue: the support of shared libraries. A new service to support shared libraries in mobile environments is proposed and we discuss the integration of this service into a wider architecture of reactive services being developed to support distributed mobile computing. 1: Introduction Recent years have seen the emergence of mobile computing as a major new field of ...
This paper presents new algorithms that were implemented in Berkeley TCP to lessen the frequency ... more This paper presents new algorithms that were implemented in Berkeley TCP to lessen the frequency of "congestion collapse" on the Internet. So successful were these algorithms, that all Internet host TCP implementations are required to use them [4]. Indeed, these algorithms have been given credit for saving the Internet from permanent congestion collapse.
Flexibility to adapt to radically different network environments will be key to the success of ne... more Flexibility to adapt to radically different network environments will be key to the success of new distributed operating systems. An operating system must be able to support the distribution of objects on high bandwidth fiber-optic as well low-bandwidth wireless networks. In this position paper, we provide a sketch of OS6, a new operating system being designed to provide low latency run-time services in distributed environments made up of both high and low bandwidth networks. Efficient distribution of objects is maintained by special operating system agents that pre-fetch and cache data facilities as well as guard object consistency. Network-level multicast filtering supports the replication and consistency tasks performed by these agents. Support for mobility is provided by persistent virtual memory which guarantees consistent object state across reboots of the machine. Real-time quality of service guarantees for distributed multimedia applications are supported by a "meta-sch...
We present an architecture where clients can make resource reservations through agents. For each ... more We present an architecture where clients can make resource reservations through agents. For each domain in the network, there is an agent responsible for admission control. The architecture provides scalable resource reservations for uni-directional virtual leased lines. Reservations from different sources to the same destination are aggregated as their paths merge toward the destination. When there are sufficient resources in a destination domain, pre x aggregation is performed. Thus, all reservations for a given destination domain are aggregated as their paths merge. Agents are responsible for setting up police points at edges for checking commitments.
JetFile is a distributed file system designed to support shared file access in a heterogenous env... more JetFile is a distributed file system designed to support shared file access in a heterogenous environment such as the Internet. It uses multicast communication and optimistic strategies for synchronization and distribution. JetFile relies on "peer-to-peer" communication over multicast channels. Most of the traditional file server responsibilities have been decentralized. In particular, the more heavyweight operations such as serving file data and attributes are, in our system, the responsibility of the clients. Some functions such as serializing file updates are still centralized in JetFile. Since serialization is a relatively lightweight operation in our system, serialization is expected to have only minor impact on scalability. We have implemented parts of the JetFile design and have measured its performance over a local-area network and an emulated wide-area network. Our measurements indicate that, using a standard benchmark, JetFile performance is comparable to that of...
For some time, the networking community has assumed that it is impossible to do IP routing lookup... more For some time, the networking community has assumed that it is impossible to do IP routing lookups in software fast enough to support gigabit speeds. IP routing lookups must �nd the routing entry with the longest matching pre�x, a task that has been thought to require hardware support at lookup frequencies of millions per second. We present a forwarding table data structure designed for quick routing lookups. Forwarding tables are small enough to �t in the cache of a conventional general purpose processor. With the table in cache, a 200 MHz Pentium Pro or a 333 MHz Alpha 21164 can perform a few million lookups per second. This means that it is feasible to do a full routing lookup for each IPpacket at gigabit speeds without special hardware. The forwarding tables are very small, a large routing table with 40,000 routing entries can be compacted to a forwarding table of 150�160 Kbytes. A lookup typically requires less than 100 instructions on an Alpha, using eight memory references ac...
This article defines a wireless broadcasting algorithm as having two components: A retransmission... more This article defines a wireless broadcasting algorithm as having two components: A retransmission strategy and a backoff strategy. Several strategies are proposed in this article and a comparative analysis is presented between existing algorithms and the strategies proposed herein. Simulation experiments and analysis are used to study or demonstrate the properties and performance of specific strategies or to obtain results of a more general nature. Strategies are also evaluated with respect to their impact on routing protocols that rely on broadcasting to perform path discovery. The purpose of this evaluation is to determine which strategies result in more stable routes. The second part of this article analyzes the problem of broadcasting when nodes are assumed to be arranged on a strip. Such arrangement occurs in vehicular broadcasting applications. We present the Strip Broadcasting retransmission strategy that can be modeled as a one-dimensional problem to significantly reduce the...
In this paper, we shall describe the delayed-choice experiment first proposed by Wheeler and then... more In this paper, we shall describe the delayed-choice experiment first proposed by Wheeler and then analyze the experiment based on both our interpretation of what is happening and the Wheeler/Feynman interpretation. Our interpretation includes wave-function collapse due to a measurement, while the Wheeler/Feynman interpretation attempts to avoid wave-function collapse in a measurement, as part of their explanation, to preserve consistent unitarity. in quantum processes. We will also show that there are severe consequences for quantum computing if there is no wave function collapse due to a measurement.
This work-in-progress paper consists of four points which relate to the foundations and physical ... more This work-in-progress paper consists of four points which relate to the foundations and physical realization of quantum computing. The first point is that the qubit cannot be taken as the basic unit for quantum computing, because not every superposition of bit-strings of length n can be factored into a string of n-qubits. The second point is that the “No-cloning” theorem does not apply to the copying of one quantum register into another register, because the mathematical representation of this copying is the identity operator, which is manifestly linear. The third point is that quantum parallelism is not destroyed only by environmental decoherence. There are two other forms of decoherence, which we call measurement decoherence and internal decoherence, that can also destroy quantum parallelism. The fourth point is that processing the contents of a quantum register “one qubit at a time” destroys entanglement. Keywords-qubit; entanglement; decoherence; no-cloning theorem; quantum regi...
We present an architecture where clients can make resource reservations through agents. For each ... more We present an architecture where clients can make resource reservations through agents. For each domain in the network, there is an agent responsible for admission control. The architecture provides scalable resource reservations for uni-directional virtual leased lines. Reservations from di erent sources to the same destination are aggregated as their paths merge toward the destination. When there are su cient resources in a destination domain, pre x aggregation is performed. Thus, all reservations for a given destination domain are aggregated as their paths merge. Agents are responsible for setting up police points at edges for checking
To the memory of my father, Dr. Leon Roberto Arango Garrido (1915-1978), my sole inspiration in b... more To the memory of my father, Dr. Leon Roberto Arango Garrido (1915-1978), my sole inspiration in becoming a man of science.
Stephen Pink received a Bachelor's degree from the University of Minnesota, a Master's de... more Stephen Pink received a Bachelor's degree from the University of Minnesota, a Master's degree from Cornell University and a PhD from the Royal Institute of Technology in Sweden. He is the manager of the Computer and Network Architecture research group at the Swedish Institute of Computer Science and a Professor of Computer Science and Engineering at Luieä University in Sweden. His major interests are in protocol design, high speed and wireless networking, multimedia, and distributed operating systems.
Toxic trace element pollutants present in the raw product gas and raw flue gas streams produced d... more Toxic trace element pollutants present in the raw product gas and raw flue gas streams produced during the gasification of coal or similar carbonaceous solids containing sulfur and such trace elements are recovered by separately scrubbing the product gas and flue gas with water, combining the resulting aqueous effluents, and removing the pollutants from the combined aqueous stream as insoluble metal sulfides.
A key characteristic of mobile computing is that the end systems involved can experience differin... more A key characteristic of mobile computing is that the end systems involved can experience differing degrees of connectivity during typical operational cycles. This paper discusses the issues associated with developing distributed system services to operate in such an environment. We focus on the provision of file system support and argue that existing file systems, including those developed for use in a mobile environment, contain assumptions about their underlying communications infrastructures which are unlikely to hold in a mobile environment. This argument is supported by an in-depth examination of a specific file system issue: the support of shared libraries. A new service to support shared libraries in mobile environments is proposed and we discuss the integration of this service into a wider architecture of reactive services being developed to support distributed mobile computing. 1: Introduction Recent years have seen the emergence of mobile computing as a major new field of ...
This paper presents new algorithms that were implemented in Berkeley TCP to lessen the frequency ... more This paper presents new algorithms that were implemented in Berkeley TCP to lessen the frequency of "congestion collapse" on the Internet. So successful were these algorithms, that all Internet host TCP implementations are required to use them [4]. Indeed, these algorithms have been given credit for saving the Internet from permanent congestion collapse.
Flexibility to adapt to radically different network environments will be key to the success of ne... more Flexibility to adapt to radically different network environments will be key to the success of new distributed operating systems. An operating system must be able to support the distribution of objects on high bandwidth fiber-optic as well low-bandwidth wireless networks. In this position paper, we provide a sketch of OS6, a new operating system being designed to provide low latency run-time services in distributed environments made up of both high and low bandwidth networks. Efficient distribution of objects is maintained by special operating system agents that pre-fetch and cache data facilities as well as guard object consistency. Network-level multicast filtering supports the replication and consistency tasks performed by these agents. Support for mobility is provided by persistent virtual memory which guarantees consistent object state across reboots of the machine. Real-time quality of service guarantees for distributed multimedia applications are supported by a "meta-sch...
We present an architecture where clients can make resource reservations through agents. For each ... more We present an architecture where clients can make resource reservations through agents. For each domain in the network, there is an agent responsible for admission control. The architecture provides scalable resource reservations for uni-directional virtual leased lines. Reservations from different sources to the same destination are aggregated as their paths merge toward the destination. When there are sufficient resources in a destination domain, pre x aggregation is performed. Thus, all reservations for a given destination domain are aggregated as their paths merge. Agents are responsible for setting up police points at edges for checking commitments.
JetFile is a distributed file system designed to support shared file access in a heterogenous env... more JetFile is a distributed file system designed to support shared file access in a heterogenous environment such as the Internet. It uses multicast communication and optimistic strategies for synchronization and distribution. JetFile relies on "peer-to-peer" communication over multicast channels. Most of the traditional file server responsibilities have been decentralized. In particular, the more heavyweight operations such as serving file data and attributes are, in our system, the responsibility of the clients. Some functions such as serializing file updates are still centralized in JetFile. Since serialization is a relatively lightweight operation in our system, serialization is expected to have only minor impact on scalability. We have implemented parts of the JetFile design and have measured its performance over a local-area network and an emulated wide-area network. Our measurements indicate that, using a standard benchmark, JetFile performance is comparable to that of...
For some time, the networking community has assumed that it is impossible to do IP routing lookup... more For some time, the networking community has assumed that it is impossible to do IP routing lookups in software fast enough to support gigabit speeds. IP routing lookups must �nd the routing entry with the longest matching pre�x, a task that has been thought to require hardware support at lookup frequencies of millions per second. We present a forwarding table data structure designed for quick routing lookups. Forwarding tables are small enough to �t in the cache of a conventional general purpose processor. With the table in cache, a 200 MHz Pentium Pro or a 333 MHz Alpha 21164 can perform a few million lookups per second. This means that it is feasible to do a full routing lookup for each IPpacket at gigabit speeds without special hardware. The forwarding tables are very small, a large routing table with 40,000 routing entries can be compacted to a forwarding table of 150�160 Kbytes. A lookup typically requires less than 100 instructions on an Alpha, using eight memory references ac...
This article defines a wireless broadcasting algorithm as having two components: A retransmission... more This article defines a wireless broadcasting algorithm as having two components: A retransmission strategy and a backoff strategy. Several strategies are proposed in this article and a comparative analysis is presented between existing algorithms and the strategies proposed herein. Simulation experiments and analysis are used to study or demonstrate the properties and performance of specific strategies or to obtain results of a more general nature. Strategies are also evaluated with respect to their impact on routing protocols that rely on broadcasting to perform path discovery. The purpose of this evaluation is to determine which strategies result in more stable routes. The second part of this article analyzes the problem of broadcasting when nodes are assumed to be arranged on a strip. Such arrangement occurs in vehicular broadcasting applications. We present the Strip Broadcasting retransmission strategy that can be modeled as a one-dimensional problem to significantly reduce the...
In this paper, we shall describe the delayed-choice experiment first proposed by Wheeler and then... more In this paper, we shall describe the delayed-choice experiment first proposed by Wheeler and then analyze the experiment based on both our interpretation of what is happening and the Wheeler/Feynman interpretation. Our interpretation includes wave-function collapse due to a measurement, while the Wheeler/Feynman interpretation attempts to avoid wave-function collapse in a measurement, as part of their explanation, to preserve consistent unitarity. in quantum processes. We will also show that there are severe consequences for quantum computing if there is no wave function collapse due to a measurement.
This work-in-progress paper consists of four points which relate to the foundations and physical ... more This work-in-progress paper consists of four points which relate to the foundations and physical realization of quantum computing. The first point is that the qubit cannot be taken as the basic unit for quantum computing, because not every superposition of bit-strings of length n can be factored into a string of n-qubits. The second point is that the “No-cloning” theorem does not apply to the copying of one quantum register into another register, because the mathematical representation of this copying is the identity operator, which is manifestly linear. The third point is that quantum parallelism is not destroyed only by environmental decoherence. There are two other forms of decoherence, which we call measurement decoherence and internal decoherence, that can also destroy quantum parallelism. The fourth point is that processing the contents of a quantum register “one qubit at a time” destroys entanglement. Keywords-qubit; entanglement; decoherence; no-cloning theorem; quantum regi...
We present an architecture where clients can make resource reservations through agents. For each ... more We present an architecture where clients can make resource reservations through agents. For each domain in the network, there is an agent responsible for admission control. The architecture provides scalable resource reservations for uni-directional virtual leased lines. Reservations from di erent sources to the same destination are aggregated as their paths merge toward the destination. When there are su cient resources in a destination domain, pre x aggregation is performed. Thus, all reservations for a given destination domain are aggregated as their paths merge. Agents are responsible for setting up police points at edges for checking
Uploads
Papers by Stephen Pink