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International Conference on distributed Computing systems

作者： K. Ravindran K.K. Ramakrishnan Department of computer and Information Sciences Kansas State University Manhattan KS USA Distributed Systems Architecture and Performance Digital Equipment Corporation Littleton MA USA

A syntax-oriented model for naming feature-based specification of services is provided. The model allows a service to evolve or reconfigure in functionality by adding and removing features and still coexist with its previous versions. The model's two aspects are examined. With this model for specifying services, name server functions may be factorized from service specific functions and implemented in a generic fashion in terms of parse and match operations and function invocations. This model can provide significant extension to such naming schemes as X.500 and the Universal Naming Protocol in supporting feature-based service interfaces.< >

关键词： File servers distributed computing Computer architecture Protocols Operating systems Workstations

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A ring purger for the FDDI token ring

A ring purger for the FDDI token ring

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Conference on Local Computer Networks (LCN)

作者： H. Yang K.K. Ramakrishnan Distributed Systems Architecture and Performance Digital Equipment Corporation Littleton MA USA

The fiber distributed data interface (FDDI) is a 100 Mb/s token ring which includes extensive reliability and robustness mechanisms to provide fault detection, isolation, monitoring, and recovery functions. The authors examine two well-known problems on token rings and their potential impact on FDDI. The two problems are no-owner frame (NOF) and duplicate tokens. FDDI effectively resolves these problems only when either the NOF or the duplicate token collides into a transmitting station. The impact of NOFs and duplicate tokens during the period from the occurrence of the NOF and the duplicate token until they are removed by a transmitting station can be severe. This paper presents a ring purger that transparently and continuously removes the NOFs and detects and removes duplicate tokens. A ring purger is a designated station on a ring that performs its normal functions as a station and, in addition, performs the removal of NOFs and duplicate tokens. A distributed election algorithm is used to elect a single station on a given ring to be the ring purger. The authors also present performance and robustness considerations used in the design of the ring purger algorithms. They study the performance effect of continuously purging the ring and show that the effect is negligible even in the worst case.< >

关键词： FDDI Token networks Robustness Local area networks Integrated circuit interconnections LAN interconnection Circuit faults ANSI standards Optical fiber devices Fault detection

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Frame content independent stripping for token rings

Frame content independent stripping for token rings

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1990 ACM Symposium on Communications architectures and Protocols, SIGCOMM 1990

作者： Yang, Henry Ramakrishnan, K.K. Distributed Systems Architecture and Performance Digital Equipment Corporation 550 King Street LittletonMA01460 United States

ISBN: (纸本)0897914058

Token rings have the property that a station that transmits a frame on the ring is responsible for removing the frame after it has been delivered to the destination stations. The algorithm to perform the frame removal is called 'Frame Stripping'. Most existing algorithms strip frames based on their content This is not always adequate. The need for a new algorithm arises from the fact that frames transmitted by a station need not have the station's own address as the source address for a variety of reasons - such as when a bridge transmits a frame or when another ad-dress is used as the source address by a station instead of its original station address. This paper discusses a new frame content independent stripping (FCIS) algorithm for token rings. The FCIS algorithm counts the number of frames transmitted by the station after capturing the token. In addition, the station places a special delimiter frame at the end of the transmission of frames, before releasing the token. The station then strips all received frames until either the number of frames stripped equals the number of frames transmitted or when either the delimiter frame or a token is received. We demonstrate that the FCIS algorithm has a minimal impact on the performance of the ring. We study the robustness of the algorithm to errors and demonstrate that its reliability is as good as the inherent mechanisms of the token ring. The algorithm studied here is very simple to implement and interoperates with other stations not implementing this algorithm. The algorithm places no topological restrictions on the network and has the attractive feature of removing large fragments and no-owner frames. © 1990 ACM.

关键词： Internet protocols

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Frame content independent stripping for token rings

Frame content independent stripping for token rings

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Conference on Local Computer Networks (LCN)

作者： K.K. Ramakrishnan H. Yang Distributed Systems Architecture and Performance Digital Equipment Corporation Littleton MA USA

A frame content independent stripping (FCIS) algorithm for token rings is described that can be used by source-routing bridges due to its simplicity and the fact that the resulting size of the fragments remaining on the ring is very small. The FCIS algorithm counts the number of outstanding frames that a station has transmitted but not yet stripped from the ring and in addition places a global delimiter such as a void frame at the end of the transmission of the information frames. The station then stops stripping when either the count goes to zero or when the void frame or token is received by the station. The algorithm is simple to implement and does not place any topological restrictions on the network. It also allows for interoperation with stations which do not implement the FCIS algorithm. With the FCIS algorithm, frames are stripped at the earliest possible moment. It is shown that the combination of both the count and void is necessary for an FCIS algorithm by demonstrating that the inclusion of either just the void or the count could result in considerable overstripping of frames on the ring due to errors on the ring. The void frame adds a total of 28 bytes of overhead to every transmission opportunity at a participating station.< >

关键词： Token networks Local area networks Media Access Protocol FDDI Strips ANSI standards Standards development Integrated circuit technology Optical fibers Costs

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Frame content independent stripping 90

Frame content independent stripping

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Proceedings of the ACM symposium on Communications architectures & protocols

作者： H. Yang K. K. Ramakrishnan Distributed Systems Architecture and Performance Digital Equipment Corporation 550 King Street Littleton MA

ISBN: (纸本)9780897914055

Token rings have the property that a station that transmits a frame on the ring is responsible for removing the frame after it has been delivered to the destination stations. The algorithm to perform the frame removal is called 'Frame Stripping'. Most existing algorithms strip frames based on their content. This is not always adequate. The need for a new algorithm arises from the fact that frames transmitted by a station need not have the station's own address as the source address for a variety of reasons - such as when a bridge transmits a frame or when another address is used as the source address by a station instead of its original station address. This paper discusses a new frame content independent stripping (FCIS) algorithm for token *** FCIS algorithm counts the number of frames transmitted by the station after capturing the token. In addition, the station places a special delimiter frame at the end of the transmission of frames, before releasing the token. The station then strips all received frames until either the number of frames stripped equals the number of frames transmitted or when either the delimiter frame or a token is received. We demonstrate that the FCIS algorithm has a minimal impact on the performance of the ring. We study the robustness of the algorithm to errors and demonstrate that its reliability is as good as the inherent mechanisms of the token *** algorithm studied here is very simple to implement and interoperates with other stations not implementing this algorithm. The algorithm places no topological restrictions on the network and has the attractive feature of removing large fragments and no-owner frames.

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File access characterization of VAX/VMS environments

File access characterization of VAX/VMS environments

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International Conference on distributed Computing systems

作者： P. Biswas K.K. Ramakrishnan Business and Office Systems Engineering Functional Analysis Group Digital Equipment Corporation Nashua NH USA Distributed Systems Architecture and Performance Group Digital Equipment Corporation Littleton MA USA

A comprehensive analysis of file access behavior of several commercial production VAX/VMS environments, based on detailed I/O traces, is presented. The characterization focuses on file control operations (such as opens and closes) which are often expensive in both processing and I/O requirements. The motivation for this analysis is the need to design good data management algorithms for distributed file systems. These algorithms are particularly important for managing client caches. Most of the operations for managing client caches are performed on file opens and closes. The authors present quantitative data on the number of file opens and closes, their timing characteristics, and their declared intent to allow sharing or have exclusive access. The precise dynamic sharing of files is examined.< >

关键词： Voice mail File systems Production systems Algorithm design and analysis Availability File servers Network servers Business systems engineering and theory Functional analysis

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performance ANALYSIS OF MASS-STORAGE SERVICE ALTERNATIVES FOR distributed systems

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IEEE TRANSACTIONS ON SOFTWARE ENGINEERING 1989年第2期15卷 120-133页

作者： RAMAKRISHNAN, KK EMER, JS Distributed Systems Architecture and Performance Digital Equipment Corporation Littleton MA 01460

In this paper, we consider the performance of alternative mass storage services for a client-server style distributed system. Some qualitative arguments are presented on the ramifications of implementations of mass storage services at various levels of the storage semantics hierarchy. This paper concentrates, in particular, on contrasting disk and files services. The functionality of disk and file services are distinguished by their primitive operations: individual disk block access, for the disk service; and individual file block access, for the file service. This difference results in different partitionings of the computation between the client and server, as well as different network communication requirements. To understand the ramifications of such differences between the services, this paper presents performance estimates for basic disk and file services. To provide a commensurate comparison of the performance of the two services, a uniform closed queueing network model was developed that accurately portrayed this computation/communication tradeoff. Detailed parameterization of the model was done through measurements of prototype systems. The workload applied to the mass storage service is based on measurements of timesharing systems performed in earlier studies. In addition to the basic comparisons, performance estimates for several design alternatives are also presented. Some of these performance enhancing alternatives were: caching of file/disk blocks and file-opens, kernel-based services, and using a network interface able to do gather write to eliminate data copies. [ABSTRACT FROM AUTHOR]

关键词： Closed queueing network models disk services distributed systems file services performance measurement and modeling remote mass storage

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The workstation on the network: performance considerations for the communications interface

The workstation on the network: performance considerations f...

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Workshop on Workstation Operating systems

作者： K.K. Ramakrishnan W.R. Hawe Distributed Systems Architecture and Performance Digital Equipment Corporation Littleton MA USA

The authors discuss their efforts at understanding the design of network adapter subsystems. Their goal has been to understand design issues, define metrics for characterizing performance in a comprehensive manner, and examine the impact of design choices on the performance of the adapter subsystem. They look at current workstation designs and the implementation of the datalink layer in the drivers of operating systems such as Unix and VMS.< >

关键词： Workstations Operating systems Hardware Throughput distributed computing Telecommunication traffic Local area networks Delay Trademarks Software performance

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Reliable client-server communication in distributed programs

Reliable client-server communication in distributed programs

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Conference on Local Computer Networks (LCN)

作者： K. Ravindran S.T. Chanson K.K. Ramakrishnan Department Of Computer Science & Automation Indian Institute of Science Bangalore India Department of Computing & Information Sciences Kansas State University Manhattan KS USA Department of Computer Science University of British Columbia Vancouver BC Canada Distributed Systems Architecture & Performance Digital Equipment Corporation Littleton MA USA

The authors' premise is that applications have the ability to tolerate certain types of failures under certain situations. This may, in turn, relax the top-level constraint on failure recovery algorithms in the interprocess communication (IPC) layer and allow exploitation of the inherent tolerance of applications to failures in a systematic way to simplify failure recovery. Using this application-driven approach, the authors present a model of a distributed program based on the well-known client-server relationship among the processes of the program. The model reflects certain generic properties of the application layer that can be exploited by the IPC layer during failure recovery. New techniques as to how the properties can be used for recovery are outlined. The authors use remote procedure call and shared variable as communication abstractions for the client and the server processes in the program to communicate with one another. The simplicity and generality of the failure recovery renders the application-driven approach particularly useful in contemporary distributed systems which are large and heterogeneous and hence have complex failure modes.< >

关键词： Local area networks Automation Computer networks distributed computing Microcomputers LAN interconnection Application software Network interfaces File systems Veins

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A binary feedback scheme for congestion avoidance in computer networks with a connectionless network layer 88

A binary feedback scheme for congestion avoidance in compute...

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1988 Symposium on Communications architectures and Protocols, SIGCOMM 1988

作者： Ramakrishnan, K.K. Jain, Raj Distributed Systems Architecture and Performance Digital Equipment Corporation United States

ISBN: (纸本)0897912799

We propose a scheme for congestion avoidance in networks using a connectionless protocol at the network layer. The scheme uses feedback from the network to the users of the network. The interesting challenge for the scheme is to use a minimal amount of feedback (one bit in each packet) from the network to adjust the amount of traffic allowed into the network. The servers in the network detect congestion and set a congestion indication bit on packets (lowing in the forward direction. The congestion indication is communicated back to the users through the transport level acknowledgement. The scheme is distributed, adapts to the dynamic state of the network, converges to the optimal operating point, is quite simple to implement, and has low overhead while operational. The scheme also addresses a very important aspect of fairness in the service provided to the various sources utilizing the network. The scheme attempts to maintain fairness in service provided to multiple sources. This paper presents the scheme and the analysis that went into the choice of the various decision mechanisms. We also address the performance of the scheme under transient changes in the network and for pathological conditions. © 1988 ACM.

关键词： Network layers

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