Return link optimization for internet service provision using DVB-S networks

Samaraweera, N.

doi:10.1145/505724.505726

Cited by 13 publications

(3 citation statements)

References 16 publications

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“…The reader is referred to [BPK99,Bal98,Pad98,FSS01,Sam99] for more details and experimental results.…”

Section: How Does Asymmetry Degrade Tcp Performance?mentioning

confidence: 99%

“…These may be either deterministic or random (similar to a random-drop gateway, but should take into consideration the semantics of the items in the queue). Algorithms have also been suggested to ensure a minimum ACK rate to guarantee the TCP sender window is updated [Sam99,FSS01], and to limit the number of data packets (TCP segments) acknowledged by a Stretch ACK. Per-flow state needs to be maintained only for connections with at least one packet in the queue (similar to FRED [LM97]).…”

Section: Type 1: Reverse Link Bandwidth Managementmentioning

confidence: 99%

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TCP Performance Implications of Network Path Asymmetry

Balakrishnan¹,

Padmanabhan²,

Fairhurst³

et al. 2002

100

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This document describes TCP performance problems that arise because of asymmetric effects. These problems arise in several access networks, including bandwidth-asymmetric networks and packet radio subnetworks, for different underlying reasons. However, the end result on TCP performance is the same in both cases: performance often degrades significantly because of imperfection and variability in the ACK feedback from the receiver to the sender.The document details several mitigations to these effects, which have either been proposed or evaluated in the literature, or are currently deployed in networks. These solutions use a combination of local link-layer techniques, subnetwork, and end-to-end mechanisms, consisting of: (i) techniques to manage the channel used for the upstream bottleneck link carrying the ACKs, typically using header compression or reducing the frequency of TCP ACKs, (ii) techniques to handle this reduced ACK frequency to retain the TCP sender's acknowledgment-triggered self-clocking and (iii) techniques to schedule the data and ACK packets in the reverse direction to improve performance in the presence of two-way traffic. Each technique is described, together with known issues, and recommendations for use. A summary of the recommendations is provided at the end of the document. , and several packet radio networks. These networks are increasingly being deployed as high-speed Internet access networks, and it is therefore highly desirable to achieve good TCP performance. However, the asymmetry of the network paths often makes this challenging. Examples of some networks that exhibit asymmetry are provided in the Appendix.Asymmetry may manifest itself as a difference in transmit and receive capacity, an imbalance in the packet loss rate, or differences between the transmit and receive paths [RFC3077]. For example, when capacity is asymmetric, such that there is reduced capacity on reverse path used by TCP ACKs, slow or infrequent ACK feedback degrades TCP performance in the forward direction. Similarly, asymmetry in the underlying Medium Access Control (MAC) and Physical (PHY) protocols could make it expensive to transmit TCP ACKs (disproportionately to their size), even when capacity is symmetric. Asymmetry due to Differences in Transmit and Receive CapacityNetwork paths may be asymmetric because the upstream and downstream links operate at different rates and/or are implemented using different technologies. In networks employing centralized multiple access control, asymmetry may be a fundamental consequence of the hub-and-spokes architecture of the network (i.e., a single base node communicating with multiple downstream nodes). The central node often incurs less transmission overhead and does not incur latency in scheduling its own downstream transmissions. In contrast, upstream transmission is subject to additional overhead and latency (e.g., due to guard times between transmission bursts, and contention intervals). This can produce significant network path asymmetry.Upstream capacity ma...

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“…The reader is referred to [BPK99,Bal98,Pad98,FSS01,Sam99] for more details and experimental results.…”

Section: How Does Asymmetry Degrade Tcp Performance?mentioning

confidence: 99%

Section: Type 1: Reverse Link Bandwidth Managementmentioning

confidence: 99%

TCP Performance Implications of Network Path Asymmetry

Balakrishnan¹,

Padmanabhan²,

Fairhurst³

et al. 2002

100

View full text Add to dashboard Cite

show abstract

“…The ACK reconstruction [8] technique is assumed to be used in conjunction with AF to expedite the congestion window opening during the slow start phase. With this in use, the ACK stream through the bottleneck link will be changed only in its spacing of ACKs, and the concept of group and the interaction of one-ACK-three-packets is the same as in the ATCP Model.…”

Section: Modeling Asymmetric Tcp With Ack Filteringmentioning

confidence: 99%

Prediction of short-lived TCP transfer latency on bandwidth asymmetric links

Tan

Jarvis

2006

Journal of Computer and System Sciences

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TCP over bandwidth asymmetric networks such as Cable TV and Asymmetric Digital Subscriber Loop (ADSL) exhibits different characteristics from TCP on symmetric links. A number of techniques have been proposed to address this problem. However, previous research has been largely focused on bulk transfers. This paper investigates the effects of bandwidth asymmetry on Weblike short-lived transfers. Two prediction models, one given in a closed form and the other in a recursive form, are presented for TCP transfers without and with ACK Filtering (AF), a representative optimizing technique for TCP transfers over bandwidth asymmetric links. Ns-2 based experiments show that these models can predict TCP transfer latency with a high degree of accuracy.

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TCP Performance Over Satellite Channels

Henderson

2003

Internetworking and Computing Over Satellite Networks

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Technological advances are enabling new satellite communications systems that combine broadband data rates with small terminals. These novel systems are being designed to provide affordable "last-mile" network access to home and small business users worldwide. In particular, two types of advanced broadband satellite systems are under development: high-power satellites deployed at traditional geostationary (GEO) orbits, and large constellations of satellites deployed at much lower (LEO) orbits. In this report, we explore research problems that have arisen from the attempt to use GEO satellites to provide Internet access. In particular, performance of the Internet's Transmission Control Protocol (TCP) is degraded by the high latency and high degree of bandwidth asymmetry present in such systems, and the degradation is compounded by the packet-level congestion found in today's Internet. We first study whether TCP's congestion avoidance algorithm can be adjusted to provide better fairness when satellite connections are forced to share bottleneck links with other (shorter delay) connections. Our data suggests that adjustments of the policy used in that algorithm may yield substantial fairness benefits without compromizing utilization. We next demonstrate how minor variations in TCP implementations can have drastic performance implications when used over satellite links (such as a reduction in file transfer throughput by over half), and from our observations construct a satelliteoptimized TCP implementation, using standardized options, that achieves good file transfer performance when congestion is light. We explore the performance of TCP for short data transfers such as Web traffic, and find that two experimental options relating to how TCP starts a connection, when used together, could reduce the user-perceived latency by a factor of two to three. However, because not all of these options are likely to be deployed on a wide scale, and because even the best satellite-optimized TCP implementation is vulnerable to the fairness problems identified above, we explore the performance benefits of splitting a TCP connection at a protocol gateway within the satellite network, and find that such an approach can allow the performance of the satellite connection to approach that of a non-satellite connection. Our results illustrate many of the remaining challenges facing TCP performance over GEO satellite links while also demonstrating techniques that can be used to optimize performance in many satellite networks.

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Return link optimization for internet service provision using DVB-S networks

Cited by 13 publications

References 16 publications

TCP Performance Implications of Network Path Asymmetry

TCP Performance Implications of Network Path Asymmetry

Prediction of short-lived TCP transfer latency on bandwidth asymmetric links

TCP Performance Over Satellite Channels

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