Implementation of Provably Stable MaxNet

MaxNet TCP is a congestion control protocol that uses explicit multi-bit signalling from routers to achieve desirable properties such as high throughput and low latency. In this paper we present an implementation of an extended version of MaxNet. Our contributions are threefold. First, we extend the original algorithm to give both provable stability and rate fairness. Second, we introduce the MaxStart algorithm which allows new MaxNet connections to reach their fair rates quickly. Third, we provide a Linux kernel implementation of the protocol. With no overhead but 24-bit price signals, our implementation scales from 32 bit/s to 1 peta-bit/s with a 0.001% rate accuracy. We confirm the theoretically predicted properties by performing a range of experiments at speeds up to 1 Gbit/sec and delays up to 180 ms on the WAN-in-Lab facility

Evaluation of FAST TCP in Low-Speed DOCSIS-based Access Networks

There is strong evidence that the efficiency of the Internet is limited by its existing TCP congestion control system. A replacement, FAST, has been shown to improve performance in high-speed networks. In order to achieve widespread acceptance and standardisation, it must also be tested in environments more typical of the existing Internet. This paper experimentally evaluates the performance of FAST over a typical access link, with bandwidths of around 0.5-3 Mbps. Links both using the DOCSIS cable modem medium access control (MAC) protocol and simple low rate links were investigated. It is shown that the random delay introduced by MAC protocol of the cable modem does not appear to interfere significantly with FAST's ability to set the congestion window size to its target. However, the cable modem does appear to introduce consistent additional delays when the link is highly, but not fully, utilised. These unexplained delays mean that a larger congestion window is required, and must be taken into account when setting FAST's parameters, notably the target queue size, alpha

Understanding XCP: Equilibrium and Fairness

We prove that the XCP equilibrium solves a constrained max-min fairness problem by identifying it with the unique solution of a hierarchy of optimization problems, namely those solved by max-min fair allocation, but solved by XCP under an additional constraint. This constraint is due to the "bandwidth shuffling" necessary to obtain fairness. We describe an algorithm to compute this equilibrium and derive a lower and upper bound on link utilization. While XCP reduces to max-min allocation at a single link, its behavior in a network can be very different. We illustrate that the additional constraint can cause flows to receive an arbitrarily small fraction of their max-min fair allocations. We confirm these results using ns2 simulations

High Performance DiffServ Mechanism for Routers and Switches: Packet Arrival Rate based Queue Management for Class Based Scheduling

This paper introduces a technique for applying packet arrival rate based queue management to class based scheduling algorithms. This enables a DiffServ architecture with very low packet latency, loss, and high link utilisation. Simulation results demonstrate that the proposed technique outperforms the current weighted random early drop (WRED) and weighted fair queue (WFQ) architecture

MaxNet: Faster Flow Control Convergence

MaxNet is a distributed congestion control architecture in which only the most severely bottlenecked link on the end-to-end path generates the congestion signal that controls the source rate. This is unlike SumNet networks, such as the current Internet or REM, where all of the bottlenecked links on the end-to-end path add to the congestion signal (by packet marking or dropping). Previously, we have shown that MaxNet results in MaxMin like rate allocation and is stable for arbitrarily large networks. In this paper we analyze the small-signal convergence speed of MaxNet. We show that MaxNet is able to converge faster than the SumNet architecture. Faster convergence results in less delay jitter, higher utilisation and lower buffer sizes. Furthermore, we show that MaxNet decouples the control, so that each pole position depends only on parameters of one bottleneck link and of the sources controlled by that bottleneck, enabling optimal pole placement

TCP MaxNet-Implementation and Experiments on the WAN in Lab

We describe implementation and performance of TCP MaxNet, a new protocol that uses a multi-bit explicit signaling approach to congestion control. The MaxNet sender algorithm operates by adjusting its congestion window in response to explicit feedback from the most congested link encountered in the network. This scheme has numerous theoretical advantages over the ubiquitous practice of adjusting the congestion window based on the total amount of congestion in the path. We implement the MaxNet control scheme on top of the existing Linux TCP/IP protocol framework and evaluate its performance in the high bandwidth-delay environment of the WAN in Lab. Our experiments show that MaxNet possesses the desirable properties that theory predicts: very short router queues and fair sharing among multiple flows of different RTTs