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R. Jain

Publications and source records attributed to R. Jain.

At least 55 records · Page 3Linked to original sources
arXiv1998

Congestion Control with Explicit Rate Indication

As the speed and the dynamic range of computer networks evolve, the issue of efficient traffic management becomes increasingly important. This work describes an approach to traffic management using explicit rate information provided to the source by the network. We present an asynchronous distributed algorithm for optimal rate calculation across the network, where optimality is understood in the maxmin sense. The algorithm quickly converges to the optimal rates and is shown to be well-behaved in transience.

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arXiv1998

A Brief Overview of ATM: Protocol Layers, LAN Emulation, and Traffic Management

Asynchronous Transfer Mode (ATM) has emerged as the most promising technology in supporting future broadband multimedia communication services. To accelerate the deployment of ATM technology, the ATM Forum, which is a consortium of service providers and equipment vendors in the communication industries has been created to develop implementation and specification agreements. In this article, we present a brief overview on ATM protocol layers and current progress on LAN Emulation and Traffic Management in the ATM Forum.

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arXiv1998

ATM Networks: Issues and Challenges Ahead

The paper begins with a discussion of current trends in networking and a historical reviews of past networking technologies some of which failed. This leads us to the discussion about what it takes for a new technology to succeed and what challenges we face in making the current dream of a seamless world-wide high-speed ATM network a reality. Issues in using ATM cells for very high speed applications are presented. Ensuring that the users benefit from ATM networks involves several other related disciplines. These are reviewed.

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arXiv1998

Congestion Control and Traffic Management in ATM Networks: Recent Advances and A Survey

Congestion control mechanisms for ATM networks as selected by the ATM Forum traffic management group are described. Reasons behind these selections are explained. In particular, selection criteria for selection between rate-based and credit-based approach and the key points of the debate between the two approaches are presented. The approach that was finally selected and several other schemes that were considered are described.

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arXiv1998

FDDI: Current Issues and Future Trends

Key issues in upcoming FDDI standards including low-cost fiber, twisted-pair, SONET mapping, and FDDI follow-on LAN are discussed after a brief introduction to FDDI and FDDI-II

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arXiv1998

Myths about Congestion Management in High Speed Networks

Weaknesses in several recently proposed ideas about congestion control and avoidance in high-speed netwroks are identified. Both sides of the debate concerning prior reservation of resources versus walk-in service, open-loop control versus feedback control, rate control versus window control, and router-based control versus source-based control are presented. The circumstances under which backpressure is useful or not are discussed, and it is argued that a single congestion scheme is not sufficient, but that a combination of several schemes is required for complete congestion management in a network.

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arXiv1998

Characteristics of Destination Address Locality in Computer Networks: A Comparison of Caching Schemes

The size of computer networks, along with their bandwidths, is growing exponentially. To support these large, high-speed networks, it is neccessary to be able to forward packets in a few microseconds. One part of the forwarding operation consists of searching through a large address databse. This problem is encountered in the design of bridges, routers, gateways and name servers. Caching can reduce the lookup time if there is a locality in the address reference pattern. Using a destination reference trace measured on an extended local are a network, we attempt to see if the destination refernces do have a significant locality. We compared the performance of MIN, LRU, FIFO, and random cache replacement algorithms. We found that the interactive (terminal) traffic in our sample had quite different locality behavior than that of the noninteractive traffic. The interactive traffic did not follow the LRU stack model while the noninteractivetraffic did. Examples are shown of the environments in which caching can help as well as those in which caching can hurt, unless the cache size is large.

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arXiv1998

A Delay Based Approach for Congestion Avoidance in Interconnected Heterogeneous Computer Networks

In heterogeneous networks, achieving congestion avoidance is difficult because the congestion feedback from one subnetwork may have no meaning to source on other other subnetworks. We propose using changes in round-trip delay as an implicit feedback. Using a black-box model of the network, we derive an expression for the optimal window as a function of the gradient of the delay-window curve. The problems of selfish optimum and social optimum are also addressed. It is shown that without a careful design, it is possible to get into a race condition during heavy congestion, where each user wants more resources than others, thereby leading to a diverging congestion It is shown that congestion avoidance using round trip delay is a promising approach. The aproach has the advantage that there is absolutely no overhead for the network itself. It is exemplified by a simple scheme. The performance of the scheme is analyzed using a simulation model. The scheme is shown to be efficient, fair, convergent and adaptive to changes in network configuration. The scheme as described works only for networks that can ne modelled with queueing servers with constant service times. Further research is required to extend it for implementation in practical networks. Several directions for future research have beensuggested.

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arXiv1998

Congestion Avoidance in Computer Networks with a Connectionless Network Layer

Widespread use of computer networks and the use of varied technology for the interconnection of computers has made congestion a significant problem. In this report, we summarize our research on congestion avoidance. We compare the concept of congestion avoidance with that of congestion control. Briefly, congestion control is a recovery mechanism, while congestion avoidance is a prevention mechanism. A congestion control scheme helps the network to recover from the congestion state while a congestion avoidance scheme allows a network to operate in the region of low delay and high throughput with minimal queuing, thereby preventing it from entering the congested state in which packets are lost due to buffer shortage. A number of possible alternatives for congestion avoidance were identified. From these alternatives we selected one called the binary feedback scheme in which the network uses a single bit in the network layer header to feed back the congestion information to its users, which then increase or decrease their load to make optimal use of the resources. The concept of global optimality in a distributed system is defined in terms of efficiency and fairness such that they can be independently quantified and apply to any number of resources and users. The proposed scheme has been simulated and shown to be globally efficient, fair, responsive, convergent, robust, distributed, and configuration-independent.

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arXiv1998

Congestion Avoidance in Computer Networks with a Connectionless Network Layer, Part I: Concepts, Goals and Methodology

Congestion is said to occur in the network when the resource demands exceed the capacity and packets are lost due to too much queuing in the network. During congestion, the network throughput may drop to zero and the path delay may become very high. A congestion control scheme helps the network to recover from the congestion state. A congestion avoidance scheme allows a network to operate in the region of low delay and high throughput. Such schemes prevent a network from entering the congested state. Congestion avoidance is a prevention mechanism while congestion control is a recovery mechanism. We compare the concept of congestion avoidance with that of flow control and congestion control. A number of possible alternative for congestion avoidance have been identified. From these a few were selected for study. The criteria for selection and goals for these schemes have been described. In particular, we wanted the scheme to be globally efficient, fair, dynamic, convergent, robust, distributed, configuration independent, etc. These goals and the test cases used to verify whether a particular scheme has met the goals have been described. We model the network and the user policies for congestion avoidance as a feedback control system. The key components of a generic congestion avoidance scheme are: congestion detection, congestion feedback, feedback selector, signal filter, decision function, and increase/decrease algorithms. These components have been explained.

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arXiv1998

Divergence of Timeout Algorithms for Packet Retransmissions

The problem of adaptively setting the timeout interval for retransmitting a packet has been discussed. A layered view of the algorithms has been presented. It is shown that a timeout algorithm consists of essentially five layers or procedures which can be independently chosen and modified. A number of timeout algorithms proposed in the literature have been decomposed into these five layers. One of the key layers not discussed in the literature is that of determining the sample round trip delay for packets that have been transmitted more than once. It is shown that this layer has a significant impact on the network performance. Under repeated packet loss, most timeout algorithms either diverge or converge to a wrong value. A number of alternative schemes have been presented. It is argued that divergence is preferable to false convergence. It is a feature that is helpful in reducing network traffic congestion.

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arXiv1998

On Caching out-of-order packets in window flow controlled networks

In window flow controlled networks, if a packet is lost the destination has to decide whether to save (cache) subsequent out-of-order packets. Also, the source has to decide whether to send just one packet or to send all packets following it. This leads to four different types of caching schemes. Simulations show, against our immediate intuition, that regardless of whether the destination is caching or not, the source should retransmit only one packet. This paper describes the alternatives to, and provides justification for, schemes used in Digital Network Architecture and ARPAnet TCP.

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arXiv1998

A Quantitative Measure Of Fairness And Discrimination For Resource Allocation In Shared Computer Systems

Fairness is an important performance criterion in all resource allocation schemes, including those in distributed computer systems. However, it is often specified only qualitatively. The quantitative measures proposed in the literature are either too specific to a particular application, or suffer from some undesirable characteristics. In this paper, we have introduced a quantitative measure called Indiex of FRairness. The index is applicable to any resource sharing or allocation problem. It is independent of the amount of the resource. The fairness index always lies between 0 and 1. This boundedness aids intuitive understanding of the fairness index. For example, a distribution algorithm with a fairness of 0.10 means that it is unfair to 90% of the users. Also, the discrimination index can be defined as 1 - fairness index.

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arXiv1998

A Comparison of Hashing Schemes for Address Lookup in Computer Networks

Using a trace of address references, we compared the efficiency of several different hashing functions, such as cyclic redundancy checking (CRC) polynomials, Fletcher checksum, folding of address octets using the exclusive-or operation and bit extraction from the address. Guidelines are provided for determining the size of the hashmark required to achieve a specified level of performance.

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arXiv1998

Error Characteristics of Fiber Distributed Data Interface (FDDI)

Fiber Distributed Data Interface (FDDI) is a 100 megabits per second fiber optic local area network (LAN) standard being developed by the American National Standard Institute (ANSI). We analyze the impact of various design decisions on the error detection capability of the protocol. In particular, we quantify frame error rate, token loss rate, and undetected error rate. Several characteristics of the 32-bit frame check sequence (FCS) polynomial, which is also used in IEEE 802 LAN protocols, are discussed.

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arXiv1998

Congestion Control in Computer Networks: Trends and Issues

Popular myths that cheaper memory, high-speed links and high-speed processors will solve the problem of congestion in computer networks are shown to be false. A simple definition for congestion based on supply and demand of resources is proposed and is then used to classify various congestion schemes. The issues that make the congestion problem a difficult one are discussed, and then the architectural decisions that affect the design of a congestion scheme are presented. It is argued that long-, medium- and short-term congestion problems require different solutions. Some of the recent schemes are brifly surveyed, and areas for further research are discussed.

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arXiv1998

Performance Analysis of FDDI Token Ring Networks: Effect of Parameters and Guidelines for Setting TTRT

The performance of Fiber-Distributed Data Interface (FDDI) depends upon several workload parameters; for example; the arrival pattern, frame size, and configuration parameters, such as the number of stations on the ring, extent of the ring, and number of stations that are waiting to transmit. In addition, the performance is affected by a parameter called the Target Token Rotation Time (TTRT), which can be controlled by the network manager. We considered the effect of TTRT on various performance metrics for different ring configurations and concluded that a TTRT value of 8 ms provides a good performance over a wide range of configurations and workloads.

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