Variable-structure Congestion Control Protocol Research Articles

Fast fairness convergence through fair rate estimation in Variable-structure congestion Control Protocol

Traditional Transmission Control Protocol (TCP) faces significant limitations such as unclear congestion implication, low utilization in high-speed networks, unstable throughput and limited fairness. In order to overcome such limitations, numerous research works have been done in effective congestion control algorithms. Among these, Variable-structure congestion Control Protocol (VCP) leverages only the existing two explicit congestion notification bits for network congestion feedback, yet achieves high utilization, low persistent queue length, negligible packet loss rate and reasonable fairness. However, VCP converges to fairness relatively slowly due to its large multiplicative decrease parameter. To address this problem, we propose an end-host based method for fast fairness convergence, namely VCP-FFC (VCP with fast fairness convergence). In each Additive Increase and Multiplicative Decrease (AIMD) epoch, VCP-FFC estimates a fair rate in end-hosts, and adjusts the congestion window according to the fair rate to achieve fast fairness convergence. We evaluate the performance of VCP-FFC over a wide range of network scenarios using NS2. Simulation Results show that VCP-FFC not only maintains the good properties of VCP, but also significantly accelerates fairness convergence. Dynamic analysis shows that VCP-FFC is asymptotically stable and converges to a unique stationary point, i.e. the fair rate share.

Max-min fair rate allocation for VCP in multi-bottleneck networks

Variable-structure congestion Control Protocol VCP leverages the existing two Explicit Congestion Notification ECN bits for network congestion feedback and achieves comparable performance to eXplicit congestion Control Protocol XCP. VCP utilises the encoded load factor-based feedback scheme to deliver congestion signals. In multi-bottleneck networks, all bottleneck links on the transmission path would contribute to the aggregate congestion signal, and VCP fails to achieve max-min fairness. To address this problem, a new metric called overload period is introduced to measure the congestion level of links, and the overload period-based feedback scheme is proposed to make sure that each VCP flow's rate is controlled only by the link with minimum overload period encountered on the transmission path. It is proved that the link with minimum overload period is the flow's bottleneck, and the max-min fair rate allocation is achieved in multi-bottleneck networks. The overload period-based feedback scheme is validated using NS2 simulations.

Usage of Variable Structure Congestion Control Protocol (VCP) in Buffer Overflow Attack Blocker

In this paper, we proposed the usage of “Variable Structure Congestion Control Protocol” in network communication to avoid Buffer Overflow thereby preventing Buffer Overflow Attacks. In general transferring a signal between connected Clients are done through “Transmission Control Protocol” in which only two states are clearly shown i.e. either “0” or “1”. For successful transmission “1” is represented and for failure transmission “0” is represented during transmission process. In “Variable Structure Congestion Control Protocol “there are four possible states for representing the signal transmission. They are “00, 01, 10, and 11”. Through VCP the signal transmission can be classified as “Low load region”, “High load region” and “Overload region” from which the transmission load can be monitored thereby preventing “Buffer Overflow” in network transmission. Round Trip Time (RTT) and Round Trip Time Timeout (RTO) have been calculated together with VCP to prevent buffer overflow attack during signal transmissions.

Analysis, Simulation, and Implementation of VCP: A Wireless Profiling

Every congestion-control protocol operating in wireless networks is potentially faced with two major challenges of performance degradation. These sources are: 1) the coupling of fairness and efficiency; and 2) not properly differentiating between congestion-caused loss associated with network buffering and error-caused loss associated with fading effects. In this paper, we provide a Variable-structure Congestion-control Protocol (VCP)-based cross-layer framework of congestion control that can address both challenges noted. As a part of our framework, we introduce a loss differentiation heuristic algorithm that can be used with a variety of congestion-control protocols. Then, using analysis, simulation, implementation, and emulation, we profile the performance of a number of congestion-control alternatives in wireless networks. We describe the first implementation of VCP as a collection of loadable kernel modules along with fine-tuned implementations of XCP and TCP / AQM + ECN in Linux. We utilize NS2 as our simulation tool and a wired Linux testbed emulating wireless link effects as our experimental tool. We implement a finite-state Markov chain in both NS2 and our testbed in order to model error-caused loss over wireless links. We further use link-layer forward error correction (FEC) codes on a per-packet basis to compensate against such loss. Our profiling results demonstrate that VCP equipped with our loss differentiation heuristic and link-layer FEC represents a well-performing yet practical alternative of wireless congestion control. We also identify some of the shortcomings of VCP, including its oscillatory behavior in the presence of link estimation errors and poor fairness characteristic in multibottleneck networks.

One More Bit is Enough

Achieving efficient and fair bandwidth allocation while minimizing packet loss and bottleneck queue in high bandwidth-delay product networks has long been a daunting challenge. Existing end-to-end congestion control (e.g., TCP) and traditional congestion notification schemes (e.g., TCP+AQM/ECN) have significant limitations in achieving this goal. While the XCP protocol addresses this challenge, it requires multiple bits to encode the congestion-related information exchanged between routers and end-hosts. Unfortunately, there is no space in the IP header for these bits, and solving this problem involves a non-trivial and time-consuming standardization process. In this paper, we design and implement a simple, low-complexity protocol, called variable-structure congestion control protocol (VCP), that leverages only the existing two ECN bits for network congestion feedback, and yet achieves comparable performance to XCP, i.e., high utilization, negligible packet loss rate, low persistent queue length, and reasonable fairness. On the downside, VCP converges significantly slower to a fair allocation than XCP. We evaluate the performance of VCP using extensive ns2 simulations over a wide range of network scenarios and find that it significantly outperforms many recently-proposed TCP variants, such as HSTCP, FAST, CUBIC, etc. To gain insight into the behavior of VCP, we analyze a simplified fluid model and prove its global stability for the case of a single bottleneck shared by synchronous flows with identical round-trip times.

EVCP: a convergence time improved high-speed transport congestion control protocol

The Internet evolves to incorporate very-high-bandwidth optical links and more large-delay satellite links. TCP faces new challenges in this unique environment. Theory and experiments showed that TCP becomes inefficient and is prone to be unstable as the per-flow product of bandwidth and latency increases, regardless of the queuing scheme. Variable-structure congestion Control Protocol (VCP) is proposed to address these problems. However, VCP has problem in terms of convergence time, i.e., it takes a long time for a new VCP flow to achieve fair bandwidth allocation if the existing VCP flows have large congestion windows. This paper proposed an Extended Variable-structure congestion Control Protocol (EVCP), which adopted a convergence controller. The basic idea of convergence controller is that if a flow has larger window than its fair window, its congestion window should be decreased more aggressively than usual in Multiplicative Decrease (MD) phase. Simulations showed that EVCP has better performance in terms of convergence time while keeping the advantages of VCP.

One more bit is enough

Achieving efficient and fair bandwidth allocation while minimizing packet loss in high bandwidth-delay product networks has long been a daunting challenge. Existing end-to-end congestion control ( eg TCP) and traditional congestion notification schemes ( eg TCP+AQM/ECN) have significant limitations in achieving this goal. While the recently proposed XCP protocol addresses this challenge, XCP requires multiple bits to encode the congestion-related information exchanged between routers and end-hosts. Unfortunately, there is no space in the IP header for these bits, and solving this problem involves a non-trivial and time-consuming standardization process.In this paper, we design and implement a simple, low-complexity protocol, called Variable-structure congestion Control Protocol (VCP), that leverages only the existing two ECN bits for network congestion feedback, and yet achieves comparable performance to XCP, ie high utilization, low persistent queue length, negligible packet loss rate, and reasonable fairness. On the downside, VCP converges significantly slower to a fair allocation than XCP. We evaluate the performance of VCP using extensive ns2 simulations over a wide range of network scenarios. To gain insight into the behavior of VCP, we analyze a simple fluid model, and prove a global stability result for the case of a single bottleneck link shared by flows with identical round-trip times.