Low analyzes the equilibrium performance of the recently developed explicit control protocol (XCP) by applying the derived window-based dynamical model. However, Low's window-based dynamic model is too complicated to be used easily. In our previous works, a simple rate-based model is proposed for analyzing XCP's equilibrium performance. Most results that appeared in Low's paper can be easily reproduced by applying our simple dynamic model. Furthermore, we prove that the shuffling parameter 7 is no more than the parameter gamma to achieve high link utilization. In this paper, we derive stringent lower and upper bounds of link utilization provided with the new constraint gamma les alpha. Furthermore, to study the equilibrium performance of networks with the compensation policy, we use the simplest topology of two links in chains. The sufficient conditions of the compensation policy are proposed, and the link utilization with the compensation policy is derived as a root of a cubic equation. Simulation results are used to verify our results.

The fair bandwidth allocations can isolate flows and protect well-behaved flows from ill-behaved ones. CSFQ (core stateless fair queueing) achieves the approximate fairness by dropping the extra packets beyond the fair share bandwidth at the routers. A heuristic method is used to estimate the fair share in CSFQ. Furthermore, we know that SRED (stabilized RED) uses a probabilistic method based on a Zombie list to estimate the number of flows at the router. In this paper, we take the probabilistic idea from SRED and apply it in CSFQ to estimate the fair share without using the Zombie list. Simulation results show that the new probabilistic approach achieves a comparable or even better performance than the original heuristic approach

Packet delay variation (or delay jitter) measurements are used by applications to estimate the service quality received from the network, or by network operators to monitor network operation states. Since a single jitter measurement takes two delay samples to calculate, the time scale over which the two delay samples are taken may affect the statistics of measured jitter. The current common practice of calculating jitter statistics is by treating all measurements as valid samples of the same sampling space. In this paper, we perform scaling analyses on measured delay sequences to show that the proper way of conducting jitter statistic analysis is by first grouping jitter samples into different clusters each containing samples that are taken over the same or similar time scales, and then carrying out statistic analysis separately on these clusters. This special treatment is desired due to the existence of strong short-range dependency among packet delays, which is introduced by queueing effect. The tool selected to perform the scaling analysis is called Deviation-Lag Function (DLF). We show that some congestion-related information of congested end-to-end paths can be derived from their DLF plots. We also discuss the potential usage of DLF for bottleneck queue detection.

In this paper we explore a control architecture that can implement active queue management and transport control. For queue management, two independent metrics-utilization factor /spl rho/ and burstiness factor /spl eta/, are used to characterize queueing congestion state. Consequently, two information bits are generated to guide the sender's adaptation of traffic intensity and burstiness. Transport control is achieved through the combination of a window and a token bucket that can respond to the two-bit feedback properly. Preliminary simulation study shows that this architecture can easily achieve specified throughput and constrain both queueing delay and delay jitter within specified bounds.

The delay-boundary prediction algorithms currently implemented by transport protocols are lowpass filters based on autoregressive and moving average (ARMA) models. However, previous studies have revealed a fractal-like structure of delay sequences, which may not be well suited to ARMA models. We propose a novel delay-boundary prediction algorithm based on a deviation-lag function (DLF) to characterize the end-to-end delay variations. Compared to conventional algorithms derived from ARMA models, the new algorithm can adapt to delay variations more rapidly and share the delay's robust high-order statistical information (jitter deviation) among competing connections along a common network path. Preliminary experiments show that it outperforms Jacobson's (1988) algorithm, which is based on an ARMA model, by significantly reducing the prediction error rate. To show the practical feasibility of the DLF algorithm, we also propose a skeleton implementation model.

Many previous studies on network traffic demonstrate that long-range dependence (LRD) is a ubiquitous property of traffic both in a local area network (LAN) and a wide area network (WAN). So the performance of the network should be dominated by this property. The packet round-trip delay is an important measurement of network performance. We present evidence that LRD exists in packet round-trip delays. This discovery has serious implications for understanding the impact on network performance of LRD network traffic, and the design of transport control protocols for special applications, i.e., of teleconferencing. Statistical analyses show that the complementary probability distribution of packet round-trip delays decays more slowly than at an exponential rate; this fact probably justifies the studies on the prediction of the queue length distribution with LRD network traffic. We also tentatively use a multi-queueing system to interpret the existence of LRD in the packet round-trip delay process, which we believe is caused by the LRD of Internet traffic.

This paper describes the analysis, implementation, and performance of a new algorithm engineered to discipline a computer clock to a source of standard time, such as a GPS receiver or another computer synchronized to such a source. The algorithm is intended for the network time protocol (NTP), which is in widespread use to synchronize computer clocks in the global Internet, or with another functionally equivalent protocol such as DTSS or PCS. It controls the computer clock time and frequency using an adaptive-parameter hybrid phase/frequency lock feedback loop. Compared with the current NTP Version 3 algorithm, the new algorithm developed for NTP Version 4 provides improved accuracy and reduced network overhead, especially when per-packet or per-call charges are involved. The algorithm has been implemented in a special-purpose NTP simulator, which also includes the entire suite of NTP algorithms. The performance has been verified using this simulator and both synthetic data and real data from Internet time servers in Europe, Asia, and the Americas.

The Network Time Protocol (NTP) is widely deployed in the Internet to synchronize computer clocks to each other and to international standards via telephone modem, radio and satellite. The protocols and algorithms have evolved over more than a decade to produce the present NTP Version 3 specification and implementations. Most of the estimated deployment of 100000 NTP servers and clients enjoy synchronization to within a few tens of milliseconds in the Internet of today. This paper describes specific improvements developed for NTP Version 3 which have resulted in increased accuracy, stability and reliability in both local-area and wide-area networks. These include engineered refinements of several algorithms used to measure time differences between a local clock and a number of peer clocks in the network, as well as to select the best subset from among an ensemble of peer clocks and combine their differences to produce a local dock accuracy better than any in the ensemble. This paper also describes engineered refinements of the algorithms used to adjust the time and frequency of the local clock, which functions as a disciplined oscillator. The refinements provide automatic adjustment of algorithm parameters in response to prevailing network conditions, in order to minimize network traffic between clients and busy servers while maintaining the best accuracy. Finally, this paper describes certain enhancements to the Unix operating system kernel software in order to realize submillisecond accuracies with fast workstations and networks.>

This paper describes a scheduling algorithm for high speed, TDMA communication networks. The problem is to find a route and determine switch schedules so that a burst of information can traverse the network from source to destination. We show that this problem is difficult, i.e., that several simple variations are NP-complete. We present an algorithm that finds schedules, and within a simplifying assumption, is guaranteed to find a route if one exists. Simulations indicate that this algorithm runs quickly in practice and overall scheduling efficiencies of 80-90% can be achieved. We also describe a variation in which the problem is to find a repeating schedule and we show how to adapt the basic algorithm for this variation.

The network time protocol (NTP), which is designed to distribute time information in a large, diverse system, is described. It uses a symmetric architecture in which a distributed subnet of time servers operating in a self-organizing, hierarchical configuration synchronizes local clocks within the subnet and to national time standards via wire, radio, or calibrated atomic clock. The servers can also redistribute time information within a network via local routing algorithms and time daemons. The NTP synchronization system, which has been in regular operation in the Internet for the last several years, is described, along with performance data which show that timekeeping accuracy throughout most portions of the Internet can be ordinarily maintained to within a few milliseconds, even in cases of failure or disruption of clocks, time servers, or networks.>

The Fuzzball is an operating system and applications library designed for the PDP11 family of computers. It was intended as a development platform and research pipewrench for the DARPA/NSF Internet, but has occasionally escaped to earn revenue in commercial service. It was designed, implemented and evolved over a seventeen-year era spanning the development of the ARPANET and TCP/IP protocol suites and can today be found at Internet outposts from Hawaii to Italy standing watch for adventurous applications and enduring experiments. This paper describes the Fuzzball and its applications, including a description of its novel congestion avoidance/control and timekeeping mechanisms.

http://deepblue.lib.umich.edu/bitstream/2027.42/6638/5/bac9439.0001.001.pdf