Raj Jain

Analysis of the increase and decrease algorithms for congestion avoidance in computer networks

Congestion avoidance mechanisms allow a network to operate in the optimal region of low delay and high throughput, thereby, preventing the network from becoming congested. This is different from the traditional congestion control mechanisms that allow the network to recover from the congested state of high delay and low throughput. Both con- gestion avoidance and congestion control mechanisms are basi- cally resource management problems. They can be formulated as system control problems in which the system senses its state and feeds this back to its users who adjust their controls. The key component of any congestion avoidance scheme is the algorithm (or control function) used by the users to in- crease or decrease their load (window or rate). We abstractly characterize a wide class of such increase/decreas e algorithms and compare them using several different performance metrics. They key metrics are efficiency, fairness, convergence time, and size of oscillations. It is shown that a simple additive increase and multiplicative decrease algorithm satisfies the sufficient conditions for con- vergence to an efficient and fair state regardless of the starting state of the network. This is the algorithm finally chosen for implementation in the congestion avoidance scheme recom- mended for Digital Networking Architecture and OSI Trans- port Class 4 Networks.

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 criterion for selection between rate-based and credit-based approach and the key points of the debate between these two approaches are presented. The approach that was finally selected and several other schemes that were considered are described.

A binary feedback scheme for congestion avoidance in computer networks

We propose a scheme for congestion avoidance in networks using a connectionless protocol at the network layer. The scheme uses a minimal amount of feedback from the network to the users, who adjust the amount of traffic allowed into the network. The routers in the network detect congestion and set a congestion-indication bit on packets flowing in the forward direction. The congestion indication is communicated back to the users through the transport-level acknowledgment. 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. The scheme maintains 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 pathological overload conditions.

Scheduling in IEEE 802.16e mobile WiMAX networks: key issues and a survey

Interest in broadband wireless access (BWA) has been growing due to increased user mobility and the need for data access at all times. IEEE 802.16e based WiMAX networks promise the best available quality of experience for mobile data service users. Unlike wireless LANs, WiMAX networks incorporate several quality of service (QoS) mechanisms at the Media Access Control (MAC) level for guaranteed services for data, voice and video. The problem of assuring QoS is basically that of how to allocate available resources among users in order to meet the QoS criteria such as delay, delay jitter and throughput requirements. IEEE standard does not include a standard scheduling mechanism and leaves it for implementer differentiation. Scheduling is, therefore, of special interest to all WiMAX equipment makers and service providers. This paper discusses the key issues and design factors to be considered for scheduler designers. In addition, we present an extensive survey of recent scheduling research. We classify the proposed mechanisms based on the use of channel conditions. The goals of scheduling are to achieve the optimal usage of resources, to assure the QoS guarantees, to maximize goodput and to minimize power consumption while ensuring feasible algorithm complexity and system scalability.

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 sources on 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 condition.It is shown that congestion avoidance using round-trip delay is a promising approach. The approach 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 which can be modeled 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 been suggested.

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. The paper describes an approach to traffic management using explicit rate information provided to the source by the network. The authors 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.

A survey of the research on future internet architectures

The current Internet, which was designed over 40 years ago, is facing unprecedented challenges in many aspects, especially in the commercial context. The emerging demands for security, mobility, content distribution, etc. are hard to be met by incremental changes through ad-hoc patches. New clean-slate architecture designs based on new design principles are expected to address these challenges. In this survey article, we investigate the key research topics in the area of future Internet architecture. Many ongoing research projects from United States, the European Union, Japan, China, and other places are introduced and discussed. We aim to draw an overall picture of the current research progress on the future Internet architecture.

A precompetitive consortium on wide-band all-optical networks

The technical core of a precompetitive consortium formed by AT&T, DEC, and MIT to study the technology, architecture and applications of wideband all-optical networks of local to national (or international) extent is described. A general introduction to all-optical networks is given, and some proposed applications are discussed. The architecture, technology and testbed portions of this effort are described. >

Congestion control in computer networks: issues and trends

Myths about congestion control are examined, and an explanation of why the trend toward cheaper memory, higher-speed links, and higher-speed processors has intensified the need to solve the congestion problem is provided. A number of proposed solutions are described, and a classification of congestion problems as well as their solutions is presented. The reasons why the problem is so difficult are identified, and the protocol design decisions that affect the design of a congestion control scheme are discussed. The authors recent proposals, namely, timeout-based congestion control, a DECbit scheme and a delay-based scheme for congestion avoidance are described, and areas for future research are suggested. >

Network virtualization and software defined networking for cloud computing: a survey

Network virtualization is the key to the current and future success of cloud computing. In this article, we explain key reasons for virtualization and briefly explain several of the networking technologies that have been developed recently or are being developed in various standards bodies. In particular, we explain software defined networking, which is the key to network programmability. We also illustrate SDN¿s applicability with our own research on OpenADN - application delivery in a multi-cloud environment.