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.
The General Packet Radio Service (GPRS) extends the Global System Mobile Communication (GSM), by introducing a packet-switched transmission service. This paper analyses the GPRS behavior under critical conditions. In particular, we focus on outages, which significantly impact the GPRS dependability. In fact, during outage periods the cumulative number of users trying to access the service grows proportionally over time.When the system resumes its operations, the overload caused by accumulated users determines a higher probability of collisions on resources assignment and therefore a degradation of the overall QoS. This paper adopts a Stochastic Activity Network modeling approach for evaluating the dependability of a GPRS network under outage conditions. The major contribution of this study lies in the novel perspective the dependability study is (*) Corresponding author -1 -framed in. Starting from a quite classical availability analysis, the network dependability figures are incorporated into a very detailed service model that is used to analyze the overload effect GPRS has to face after outages, gaining deep insights on its impact on user's perceived QoS. The result of this modeling is an enhanced availability analysis, which takes into account not only the bare estimation of unavailability periods, but also the important congestion phenomenon following outages that contribute to service degradation for a certain period of time after operations resume.
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.
SUMMARYThe differentiated services (DiffServ) architecture allows IP networks to offer different QoS levels to different users and applications. In this architecture, routers in the core network offer the same per-hop behaviour (PHB) to all packets classified as belonging to the same class at the edge of the network. One of the most important types of PHB is assured forwarding (AF) PHB. Within each AF class, IP packets can be marked with different drop precedence (DP) values, and treated differently in congested DS nodes. To this end, DiffServ nodes in the core network implement active queue management (AQM) mechanisms. The target of this paper is to provide network designers with an accurate fluid-flow analytical model of a DiffServ network, where the RED with in/out and coupled average queues (RIO-C), RED with in/out and decoupled average queues (RIO-DC) and Weighted RED (WRED) AQM techniques are implemented. We address a network simultaneously loaded with both greedy and data-limited TCP flows, and we consider one AF class in which two DPs are defined, one for packets complying with the negotiated profile (IN packets), and another for packets that do not respect it (OUT packets). A token bucket marking mechanism is modelled for this purpose. The proposed model is applied to a complex network topology. Comparison between model and simulation results demonstrates that the model is able to capture both transient and steady-state network behaviour with a high degree of accuracy, even when not all network routers implement the same AQM technique. These characteristics make our modelling approach suitable to address the issue of network parameter optimisation. As an example, the link capacity dimensioning problem in a DiffServ domain by means of an iterative optimisation algorithm is presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.