Gateway Adaptive Pacing for TCP across Multihop Wireless Networks and the Internet

In this paper, we introduce an effective congestion control scheme for TCP over hybrid wireless/wired networks comprising a multihop wireless IEEE 802.11 network and the wired Internet. We propose an adaptive pacing scheme at the Internet gateway for wired-to-wireless TCP flows. Furthermore, we analyze the causes for the unfairness of oncoming TCP flows and propose a scheme to throttle aggressive wired-to-wireless TCP flows at the Internet gateway to achieve nearly optimal fairness. Thus, we denote the introduced congestion control scheme TCP with Gateway Adaptive Pacing (TCP-GAP). For wireless-to-wired flows, we propose an adaptive pacing scheme at the TCP sender. In contrast to previous work, TCP-GAP does not impose any control traffic overhead for achieving fairness among active TCP flows. Moreover, TCP-GAP can be incrementally deployed because it does not require any modifications of TCP in the wired part of the network and is fully TCP-compatible. Extensive simulations using ns-2 show that TCPGAP is highly responsive to varying traffic conditions, provides nearly optimal fairness in all scenarios and achieves up to 42% more goodput than TCP NewReno

Active Queue Management for Fair Resource Allocation in Wireless Networks

This paper investigates the interaction between end-to-end flow control and MAC-layer scheduling on wireless links. We consider a wireless network with multiple users receiving information from a common access point; each user suffers fading, and a scheduler allocates the channel based on channel quality,but subject to fairness and latency considerations. We show that the fairness property of the scheduler is compromised by the transport layer flow control of TCP New Reno. We provide a receiver-side control algorithm, CLAMP, that remedies this situation. CLAMP works at a receiver to control a TCP sender by setting the TCP receiver's advertised window limit, and this allows the scheduler to allocate bandwidth fairly between the users

TCP in the Internet of Things: from ostracism to prominence

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.TCP has traditionally been neglected as a transport-layer protocol for the Internet of Things (IoT). However, recent trends and industry needs are favoring TCP presence in IoT environments. In this article, we describe the main IoT scenarios where TCP will be used. We then analyze the historically claimed issues of TCP in the IoT context. We argue that, in contrast to generally accepted wisdom, most of those possible issues fall in one of the following categories: i) are also found in well-accepted IoT end-to-end reliability mechanisms, ii) can be solved, or iii) are not actual issues. Considering the future prominent role of TCP in the IoT, we provide recommendations for lightweight TCP implementation and suitable operation in such scenarios, based on our IETF standardization work on the topic.Postprint (author's final draft

TCP with gateway adaptive pacing for multihop wireless networks with Internet connectivity

This paper introduces an effective congestion control pacing scheme for TCP over multihop wireless networks with Internet connectivity. The pacing scheme is implemented at the wireless TCP sender as well as at the Internet gateway, and reacts according to the direction of TCP flows running across the wireless network and the Internet. Moreover, we analyze the causes for the unfairness of oncoming TCP flows and propose a scheme to throttle aggressive wired-to-wireless TCP flows at the Internet gateway to achieve nearly optimal fairness. The proposed scheme, which we denote as TCP with Gateway Adaptive Pacing (TCP-GAP), does not impose any control traffic overhead for achieving fairness among active TCP flows and can be incrementally deployed since it does not require any modifications of TCP in the wired part of the network. In an extensive set of experiments using ns-2 we show that TCP-GAP is highly responsive to varying traffic conditions, provides nearly optimal fairness in all scenarios and achieves up to 42% more goodput for FTP-like traffic as well as up to 70% more goodput for HTTP-like traffic than TCP NewReno. We also investigate the sensitivity of the considered TCP variants to different bandwidths of the wired and wireless links with respect to both aggregate goodput and fairness

Centralized Rate Allocation and Control in 802.11-based Wireless Mesh Networks

Wireless Mesh Networks (WMNs) built with commodity 802.11 radios are a cost-effective means of providing last mile broadband Internet access. Their multihop architecture allows for rapid deployment and organic growth of these networks. 802.11 radios are an important building block in WMNs. These low cost radios are readily available, and can be used globally in license-exempt frequency bands. However, the 802.11 Distributed Coordination Function (DCF) medium access mechanism does not scale well in large multihop networks. This produces suboptimal behavior in many transport protocols, including TCP, the dominant transport protocol in the Internet. In particular, cross-layer interaction between DCF and TCP results in flow level unfairness, including starvation, with backlogged traffic sources. Solutions found in the literature propose distributed source rate control algorithms to alleviate this problem. However, this requires MAC-layer or transport-layer changes on all mesh routers. This is often infeasible in practical deployments. In wireline networks, router-assisted rate control techniques have been proposed for use alongside end-to-end mechanisms. We evaluate the feasibility of establishing similar centralized control via gateway mesh routers in WMNs. We find that commonly used router-assisted flow control schemes designed for wired networks fail in WMNs. This is because they assume that: (1) links can be scheduled independently, and (2) router queue buildups are sufficient for detecting congestion. These abstractions do not hold in a wireless network, rendering wired scheduling algorithms such as Fair Queueing (and its variants) and Active Queue Management (AQM) techniques ineffective as a gateway-enforceable solution in a WMN. We show that only non-work-conserving rate-based scheduling can effectively enforce rate allocation via a single centralized traffic-aggregation point. In this context we propose, design, and evaluate a framework of centralized, measurement-based, feedback-driven mechanisms that can enforce a rate allocation policy objective for adaptive traffic streams in a WMN. In this dissertation we focus on fair rate allocation requirements. Our approach does not require any changes to individual mesh routers. Further, it uses existing data traffic as capacity probes, thus incurring a zero control traffic overhead. We propose two mechanisms based on this approach: aggregate rate control (ARC) and per-flow rate control (PFRC). ARC limits the aggregate capacity of a network to the sum of fair rates for a given set of flows. We show that the resulting rate allocation achieved by DCF is approximately max-min fair. PFRC allows us to exercise finer-grained control over the rate allocation process. We show how it can be used to achieve weighted flow rate fairness. We evaluate the performance of these mechanisms using simulations as well as implementation on a multihop wireless testbed. Our comparative analysis show that our mechanisms improve fairness indices by a factor of 2 to 3 when compared with networks without any rate limiting, and are approximately equivalent to results achieved with distributed source rate limiting mechanisms that require software modifications on all mesh routers

Micro mobility and internet access performance for TCP connections in Ad Hoc networks

In ad hoc mobile networks nodes typically communicate over wireless channels and are capable of movement. These are networks that support multihop communication and can be formed on a temporary basis. This paper evaluates a solution that allows mobile nodes to access the wired Internet and roam from base station to base station. The solution is based on the extension of Mobile IP capabilities to the ad hoc network while a micro-mobility protocol is adapted to support local migration. We evaluate the performance of this solution with regard to reliable transport layer connections. It is shown that a high throughput is possible to achieve for high mobility speeds. It is also observed that, as the number of hops between a mobile node and the base station increases, the throughput is decreased because of the characteristics of the wireless environment and the medium access layer protocol

Usability of legacy p2p multicast in multihop ad hoc networks: an experimental study

There has recently been an increasing interest in convergence of p2p and ad hoc network research. Actually, p2p systems and multihop ad hoc networks share similar features, such as self-organisation, decentralisation, self-healing, and so forth. It is thus interesting to understand if p2p systems designed for the wired Internet are suitable also for ad hoc networks and, if they are not, in which direction they should be improved. In this paper, we report our experience in running p2p applications in real multihop ad hoc network testbeds. Specifically, we used group-communication applications that require p2p systems made up of an overlay network and a p2p multicast protocol. In this paper, we present experimental results specifically related to the performance of a well-known p2p shared-tree multicast protocol (Scribe). Our results show that such a solution is far from being efficient on ad hoc networks. We emphasize that the structured multicast approach is one of the main causes of inefficiency, and suggest that stateless solutions could be preferable

Improving Performance of QUIC in WiFi

QUIC is a new transport protocol under standardization since 2016. Initially developed by Google as an experiment, the protocol is already deployed in large-scale, thanks to its support in Chromium and Google's servers. In this paper we experimentally analyze the performance of QUIC in WiFi networks. We perform experiments using both a controlled WiFi testbed and a production WiFi mesh network. In particular, we study how QUIC interplays with MAC layer features such as IEEE 802.11 frame aggregation. We show that the current implementation of QUIC in Chromium achieves sub-optimal throughput in wireless networks. Indeed, burstiness in modern WiFi standards may improve network performance, and we show that a Bursty QUIC (BQUIC), i.e., a customized version of QUIC that is targeted to increase its burstiness, can achieve better performance in WiFi. BQUIC outperforms the current version of QUIC in WiFi, with throughput gains ranging between 20% to 30%

On the performance of QUIC over wireless mesh networks

The exponential growth in adoption of mobile phones and the widespread availability of wireless networks has caused a paradigm shift in the way we access the Internet. It has not only eased access to the Internet, but also increased users’ appetite for responsive services. New protocols to speed up Internet applications have naturally emerged. The QUIC transport protocol is one prominent case. Initially developed by Google as an experiment, the protocol has already made phenomenal strides, thanks to its support in Google’s servers and Chrome browser. Since QUIC is still a relatively new protocol, there is a lack of sufficient understanding about its behavior in real network scenarios, particularly in the case of wireless networks. In this paper we present a comprehensive study on the performance of QUIC in Wireless Mesh Networks (WMN). We perform a measurement campaign on a production WMN to compare the performance of QUIC against TCP when retrieving files from the Internet. Our results show that while QUIC outperforms TCP in wired networks, it exhibits significantly lower performance than TCP in the WMN. We investigate the reasons for this behavior and identify the root causes of the performance issues. We find that some design choices of QUIC may penalize the protocol in WiFi, e.g., uncovering sub-optimal interactions of QUIC with MAC layer features, such as frame aggregation. Finally, we implement and evaluate our solution and demonstrate up to 28% increase in throughput of QUIC.This work was supported by the Erasmus Mundus Joint Doctorate in Distributed Computing EMJD-DC program, the Spanish grant TIN2016-77836-C2-2-R, and Generalitat de Catalunya through 2017-SGR-990. This research was conducted as part of the PhD thesis which is available online at upcommons.upc.edu.Peer ReviewedPostprint (author's final draft