Many techniques have been proposed in the last few years to address performance degradations in end-to-end congestion control. Although these techniques require parameter tuning to operate in different congestion scenarios, they miss the challenging target of both minimizing network delay and keeping goodput close to the network capacity. In this paper we propose a new mechanism, called Active Window Management (AWM), which addresses these targets by stabilizing the queue length in the network gateways. AWM acts on the Advertised Window parameter in the TCP segment carrying the acknowledge, but it does not affect the TCP protocol. The proposed technique is implemented in the network access gateways, that is, in the gateways through which both the incoming and outgoing packets related to a given TCP connection are forced to go, whatever the routing strategy used in the network. We show that when the access gateways implementing AWM are the bottleneck in the networks, TCP performance is very close to that of a pseudo constant bit rate protocol providing no loss, while network utilization is close to one.
Power consumption of the Information and CommunicationTechnology sector (ICT) has recently become a key challenge. In particular, actions to improve energy-efficiency of Internet Service Providers (ISPs) are becoming imperative. To this purpose, in this paper we focus on reducing the power consumption of access nodes in an ISP network, by controlling the amount of service capacity each network device has to offer to meet the actual traffic demand. More specifically, we propose a Green router (Grouter) implementing a congestion control technique named Active Window Management (AWM) coupled with a new capacity scaling algorithm named Energy Aware service Rate Tuner Handling (EARTH). The AWM characteristics allow to detect whether a waste of energy is playing out, whereas EARTH is aimed at invoking power management primitives at the hardware level to precisely control the current capacity of access nodes and consequently their power consumption. We test the benefits of the AWM-EARTH mechanism on a realistic scenario. Results show that the capacity scaling technique can save up to 70% of power consumption, while guaranteeing Quality of Service and traffic demand constraints.
Abstract. The most efficient approaches defined so far to address performance degradations in end-to-end congestion control exploit the flow control mechanism to improve end-to-end performance. The most authoritative solution in this context seems to be the eXplicit Control Protocol (XCP) which achieves high performance but requires changes in both network routers and hosts which make it difficult to deploy. To this aim we have developed a new mechanism, called Active Window Management (AWM), which is able to maintain the queue length in network routers almost constant providing no loss, while maximizing network utilization. The idea at the basis of AWM is to allow network routers to manipulate the Advertised Window field in TCP ACKs. In this way no modifications to the TCP protocol are required. The target of this paper is to propose an extensive numerical analysis of AWM to compare it with the XCP protocol, chosen as reference case.
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