The initial TCP slow start phase seeks to ramp up data transmission rates quickly to meet available capacity but also to exit the slow start phase before causing undue congestion. Unfortunately, the typical default TCP implementation often exits slow start too early, before capacity has been reached, causing underutilization, particularly detrimental to networks with large capacities and high delays. This study introduces a novel enhancement to TCP slow start - Slow start Exit At Right CHokepoint (SEARCH) - where the link capacity is inferred at the server based on bytes delivered compared to the expected bytes delivered, smoothed to account for link latency variation and normalized to accommodate link capacities. Empirical evaluation over geosynchronous satellite links, low-orbit satellite links, and 4G LTE links shows our approach is a substantial improvement over default TCP implementations by not exiting slow start too early, but better than traditional TCP, too, by exiting slow start before encountering packet loss.

The Slow start Exit At Right CHokepoint (SEARCH) algorithm is designed to exit the TCP slow start phase after the flow has reached the link capacity but before packets have been lost. To do this, SEARCH keeps a history of the bytes delivered over a recent time window, aggregated into bins. Unfortunately, this delivery history must be kept per-flow, adding additional memory load for each TCP connection. We address this per-flow memory load by observing that SEARCH only needs the relative number of bytes delivered and propose a bit-shifting technique that dynamically compresses bin values as needed. Our approach is tunable to the memory-use reduction required compared to the delivery precision needed. Evaluation of our approach over a satellite network shows SEARCH bin memory use can be reduced by 50% or even 75% without any significant sacrifice in SEARCH algorithm accuracy. Our approach is generalizable to other network algorithms, too, reducing memory use for algorithms that use sliding windows and historical data tracking.

TCP’s slow start phase is particularly inefficient over most wireless networks, especially high-latency, high-bandwidth paths such as satellite networks, often exiting too early or too late (after packet loss). To address this, the Slow start Exit At CHokepoint (SEARCH) algorithm is designed to improve exit decisions during slow start by analyzing delivery trends across sliding RTT-based windows. This paper presents a first implementation of SEARCH in the FreeBSD kernel using FreeBSD’s modular congestion control framework. We evaluate our implementation on a testbed with an actual GEO satellite link with ~600 ms RTT and 150 Mb/s capacity. Preliminary results show that SEARCH exits slow start more effectively than HyStart and HyStart++, achieving higher throughput and better utilization.

QUIC is increasingly being deployed on the Internet as an alternative to TCP. However, QUIC over satellite links faces particular challenges as high and variable round-trip times (RTTs) make it difficult to determine and then reach link capacity. Standard slow start algorithms to detect link capacity can perform poorly over satellite links, often exiting slow start too early and limiting throughput or exiting too late and causing unnecessary packet loss. The Slow start Exit At Right CHokepoint (SEARCH) algorithm aims to exit slow start after reaching link capacity but before incurring packet loss by tracking delivery rates and exiting when rates have not increased by the expected amount. SEARCH has shown benefits over traditional slow start for TCP connections but has yet to be implemented and evaluated in QUIC. This paper presents the design and implementation of SEARCH in an open-source QUIC library, with the code publicly available as a contribution. Evaluation of SEARCH over a geostationary satellite link show SEARCH successfully exits slow start before loss in the majority of cases, Improving goodput compared to the baseline.

TCP slow start begins at a conservative bitrate but quickly ramps up to the available bandwidth. Unfortunately, current TCP implementations can either: 1) exit from slow start prematurely, which is especially detrimental to utilization on satellite links, or 2) exit from slow start too late, causing unnecessary packet loss. We propose a novel technique to exit slow start while avoiding both premature and belated exits. We evaluate our approach over commercial satellite links - long, fat networks that pose challenges to determining the right slow start exit time. Preliminary results show a high success rate for picking appropriate exit points over satellite links, with potentially being applicable to other types of networks, more generally.

Geosynchronous satellite (GEO) networks are a crucial option for users beyond terrestrial connectivity. However, unlike terrestrial networks, GEO networks exhibit high latency and deploy TCP proxies and traffic shapers. The deployment of proxies mitigates the impact of high network latency, while traffic shapers help realize customer-controlled data-saver options that optimize data usage. It is unclear how the interplay between GEO networks' high latency, TCP proxies, and traffic-shaping policies affects the quality of experience (QoE) for commonly used video applications. In our study, we examine this relationship through a series of video streaming experiments at a shaped rate of 900kbps. Our preliminary analysis reveals that 28% of TCP sessions (with TCP proxies) and 18% of gQUIC sessions (without TCP proxies) experience rebuffering events, while the median average resolution is only 380p for TCP and 299p for gQUIC. Additionally, we identify two key factors contributing to sub-optimal performance: (i) unlike TCP, gQUIC only utilizes 63% of network capacity; and (ii) YouTube's chunk request pipelining is imperfect. To avoid potential degradation in video quality, the satellite provider subsequently discontinued providing data saver options that shape video traffic to US residential customers.

Understanding how new TCP congestion control algorithms interact with the default TCP Cubic over a wide-range of network conditions is important for moving congestion control research forward. Unfortunately, lacking are studies over actual satellite Internet networks where high latencies pose challenges to TCP performance. This paper presents results from experiments over a commercial satellite Internet link assessing TCP congestion control algorithm performance for Cubic when competing with algorithms using four different approaches: loss-based (Cubic), bandwidth-estimation based (BBR), utility function-based (PCC) and satellite optimized (Hybla). Analysis shows: 1) the default Cubic algorithms are fair to each other; 2) Cubic dominates PCC during steady state; 3) Hybla dominates Cubic during start-up; and 4) BBR dominates Cubic during both start-up and steady state.

Satellite networks often use Performance Enhancing Proxies (PEPs) in order to overcome the inherent high latencies that are detrimental to TCP throughputs. Measurements of TCP performance over Satellite PEPs are lacking, both for actual PEP benefits and for interactions between PEPs and TCP congestion control algorithms. This paper presents results from experiments that assess the benefits of a PEP for a commercial satellite network, considering four TCP congestion control algorithms: Cubic, BBR, Hybla and PCC. Without the PEP, the four algorithms have similar steady state throughputs (about 70 Mb/s), but significant differences in start-up throughputs. In particular, the PEP dramatically improves (3x) start-up throughputs for TCP Cubic – the default congestion control algorithm used by most Internet servers. Overall, the PEP equalizes performance irrespective of the TCP congestion control algorithm chosen.

Satellite connections are critical for continuous network connectivity when disasters strike and for remote hosts that cannot use traditional network connections. While satellite Internet bitrates have increased, satellite latencies can still degrade TCP performance. Assessment of TCP over satellite networks is lacking, typically done only by simulation or emulation only, if at all. This paper presents experiments over a commercial satellite network comparing two popular TCP congestion control algorithms: Cubic (the default for most Internet servers) and BBR (recently deployed by Google servers). Analysis of the results shows similar steady-state bitrates for both BBR and Cubic, but with BBR having significantly higher bitrates (and, subsequently, higher round-trip times) than Cubic during start-up.

In this paper, we study the performance of Quick Idle State Protocol (QISP) introduced in CDMA 1xEV-DO Rev. B standard to enhance the battery life of Access Terminals (ATs) in the idle mode. We develop an analytical model to assess the performance of QISP and use it to compare QISP with Enhanced Idle State Protocol (EISP) of earlier standard. Specifically, we evaluate the average control channel monitoring time of ATs in the idle state as a function of AT page probability and the total number of pages in the control channel cycle. The results from the model indicate a considerable reduction in the awake time of access terminals with QISP within typical ranges of operating parameters. Finally, we offer some insights on the design of QISP within the flexibility offered by the 1xEV-DO Rev. B standard.

As use of non-TCP applications such as streaming media and network games increases, the potential for unfair, misbehaving flows and the threat of congestion collapse also increases. This paper introduces a statistical traffic filtering technique, stochastic fairness guardian (SFG), that effectively regulates misbehaving flows with minimal traffic state information. SFG can be used in conjunction with an active queue management (AQM) mechanism to improve both network protection and efficiency. Simulations are used to evaluated SFG and the integration of SFG with a proportional-integral (PI) controller in comparison with other similar statistical flow management mechanisms including RED-PD, SFB and CHOKe. The SFG-PI combination outperforms other mechanisms in terms of fairness, queuing delay, stability and TCP performance over a wide range of realistic traffic loads and conditions.

Active Queue Management (AQM) is intended to achieve high link utilization with a low queuing delay. Recent studies show that RED, one of the most well-known AQMs, is difficult to configure and does not provide significant performance gains given the complexity required for proper configuration. Recent variants of RED, such as Adaptive-RED are designed to provide more robust RED performance under a wider-range of traffic conditions but have not yet been evaluated. This paper presents a router queue behavior model (a queue law) for TCP-dropping and TCP-marking control systems, and uses the queue law to illustrate the impact of TCP traffic on the load and queue behavior of congested routers. Through queue law analysis and simulation, this paper confirms that RED-like AQM techniques that employ packet dropping do not significantly improve performance over that of drop-tail queue management. However, when AQM techniques use Explicit Congestion Notification (ECN) as a method to notify TCP sources of congestion rather than packet drops, the performance gains of AQM in terms of goodput and delay can be significant over that of drop-tail queue management.

Video streaming on the Internet often suffers from high frame loss rates due to fragmentation of large frames and inter-frame dependencies needed for high compression. We propose adding lightweight, priority-based queue management to Internet routers to significantly improve performance of video streaming. We extend a Rate-Based RED approach to support three priority classes and apply it to MPEG. The performance of the mechanism on video streams is measured, analyzed and compared with Drop-Tail and RED in terms of transport layer throughput, system fairness, application layer throughput and goodput, and video stream quality. Extensive simulation shows that our approach improves MPEG video stream quality and network system fairness over traditional RED under a variety of workloads.

The explosive increase in the volume and variety of Internet traffic has placed a growing emphasis on congestion control and fairness in Internet routers. Approaches to the problem of congestion, such as active queue management schemes like Random Early Detection (RED) use congestion avoidance techniques and are successful with TCP flows. Approaches to the problem of fairness, such as Fair Random Early Drop (FRED), keep per-flow state and punish misbehaved, non-TCP flows. Unfortunately, these punishment mechanisms also result in a significant performance drop for multimedia flows that use flow control. We extend Class-Based Threshold (CRT) [12], and propose a new active queue management mechanism as an extension to RED called Dynamic Class-Based Threshold (D- CBT) to improve multimedia performance on the Internet. Also, as an effort to reduce multimedia jitter, we propose a lightweight packet scheduling called Cut-In Packet Scheduling (ChIPS) as an alternative to FIFO packet scheduling. The performance of our proposed mechanisms is measured, analyzed and compared with other mechanisms (RED and CBT) in terms of throughput, fairness and multimedia jitter through simulation using NS. The study shows that D-CBT improves fairness among different classes of flows and ChIPS improves multimedia jitter without degrading fairness.

Article Free Access Share on An experimental evaluation of crash recovery machanisms Authors: Jack Kent View Profile , Hector Garcia-Molina View Profile , Jae Chung View Profile Authors Info & Claims PODS '85: Proceedings of the fourth ACM SIGACT-SIGMOD symposium on Principles of database systemsMarch 1985 Pages 113–122https://doi.org/10.1145/325405.325419Online:25 March 1985Publication History 7citation97DownloadsMetricsTotal Citations7Total Downloads97Last 12 Months8Last 6 weeks2 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF