Search results for "Differentiated service"
showing 10 items of 15 documents
Endpoint Admission Control over Assured Forwarding PHBs and Its Performance over RED Implementations
2001
The Assured Forwarding Per Hop Behavior (AF PHB) has been devised by the IETF Differentiated Services (DiffServ) working group to provide drop level differentiation. The intent of AF is to support services with different loss requirements, but with no strict delay and jitter guarantees. Another suggested use of AF is to provide differentiated support for traffic conforming to an edge conditioning/policing scheme with respect to nonconforming traffic. Scope of this paper is twofold. First, we show that, quite surprisingly, a standard AF PHB class is semantically capable of supporting per flow admission control. This is obtained by adopting the AF PHB as core routers forwarding mechanism in c…
PCP: An End-to end Measurement Based Call Admission Control for Real-Time Services Over IP Networks
2000
Distributed end-to-end measurement based connection admission control mechanisms have been recently proposed. The goal of these schemes is to provide tight QoScon trol on a per connection basis by means of measurements taken by the edge nodes and priority based forwarding procedure at internal nodes. Since the additional flows handling procedures are implemented at the border routers and the forwarding mechanisms are for flows aggregates only, the approach is fully scalable and compatible with the IETF Differentiated Service proposal. The aim of this paper is to propose specific schemes and to investigate the advantages and limits of the approach by analyzing the basic mechanisms and evalua…
Per-flow signalling extension across DiffServ domains
2003
This paper describes a framework devised to extend per-flow admission control operation across Differentiated Services domains. Although the specific case of interoperability with RSVP is under discussion, our proposal can be easily adapted to other hop-by-hop signalling protocols. In our framework, DiffSery border routers accomplish three tasks. First, during the set-up phase, flows are mapped onto PHB groups on the basis of their QoS and traffic specifications. Second, signalling packets are tunnelled into IP packets marked as “probes”, where the “probe” marking is a DCSP value associated to the considered PHB Group. Third, when the flow set-up is complete, flow data packets are marked as…
Adding Real-Time Networking and QoS Capabilities to RTLinux-GPL
2006
This paper presents an architecture to build distributed embedded real-time systems in the RTLinux-GPL platform. The architecture (built in a layered fashion) has being built around open source projects ranging from Ethernet drivers to a CORBA environment. The paper focuses on those layers that give support for QoS and real-time networking over Ethernet networks. The main ideas are: to accomplish deterministic access times by using a TDMA protocol over Ethernet and to multiplex different types of traffic in that real-time network, providing different service types (QoS) to each type of traffic without jeopardizing the a priori guarantee of the system's real-time properties. Traffic types in…
Quality of Service Multicasting over Differentiated Services Networks
2003
This paper proposes a solution to support real-time multicast traffic with Quality of Service (QoS) constraints over Differentiated Services (DiffServ) IP networks. Our solution allows multicast users to dynamically join and leave the multicast tree. Moreover, it allows a multicast user which has negotiated a best-effort session to upgrade to a QoS-enabled session. Our solution is backward compatible with the Protocol Independent Multicast (PIM) scheme. It combines two ideas. First, resource availability along a new QoS path is verified via a probe-based approach. Second, QoS is maintained by marking replicated packets with a special DSCP value, before forwarding them on the QoS path.
The Perceived Role of Technology in Career Guidance among Practitioners Who are Experienced Internet Users
2011
The increasing use of technology is placing new demands on career guidance practitioners. This article examines what changes, if any, have occurred in the perceptions of guidance practitioners regarding their role and the role of the internet in meeting guidance goals and delivering career guidance services. The data were collected in focus groups in 2001–2002 and a follow-up study in 2010. A total of seven focus groups were held. The data were analysed using combined methods. The results indicated that practitioners now observe that the need for differentiated service delivery modes is more explicit due to varied levels of readiness in decision-making and ICT literacy.
Packet management techniques for measurement based end-to-end admission control in IP networks
2000
End-to-end Measurement Based connection Admission Control (EMBAC) mechanisms have been proposed to support real-time flows quality of service requirements over a Differentiated Services Internet architecture. The EMBAC basic idea is to decentralize the admission control decision, by requiring each individual user to probe the network path during flow setup, and by basing the accept/reject decision on the probing traffic statistics measured at the destination. In conformance with the differentiated services framework, routers are oblivious to individual flows and only need to serve data packets with a higher priority than probing traffic. In this paper, we build upon the observation that som…
An API for Advanced Traffic Control in Diffserv Routers
2003
Distributed per-flow admission control is a promising solution for Differentiated Services networks. Its deployment in DiffSery domains requires the ability to suitably configure, in each network router, low-level packet forwarding mechanisms, such as packet dropping algorithms driven by traffic measurements. In this paper we first show that performance effectiveness is achieved by means of non traditional configuration of the forwarding mechanisms. Hence, we propose a modular Application Program Interface that allows to flexibly and adaptively configure the forwarding/dropping behavior associated to a router’s output queue, well beyond the traditional RED/RIO active queue management scheme…
An analytical model of a new packet marking algorithm for TCP flows: Preliminary insights
2004
In differentiated services networks, packet marking schemes can be devised to differentiate packets belonging to a same TCP flow, with the goal of improving the experienced performance. This paper presents an analytical model for an adaptive packet marking scheme proposed in our previous work. The model combines three specific sub-models aimed at describing i) the TCP sources aggregate ii) the marker, and iii) the network status. Some preliminary simulative results seem to validate the model.
Performance Evaluation of a new Adaptive Packet Marking Scheme for TCP over DiffServ Networks
2004
In differentiated services (DiffServ) networks, packets may receive a different treatment according to their differentiated services code point (DSCP) label. As a consequence, packet marking schemes can be devised to differentiate packets belonging to the same TCP flow, with the goal of improving the experienced performance. The paper presents an extensive performance evaluation of a new adaptive packet marking scheme, applied to a traffic scenario composed of TCP flows with different lengths. The proposed marking scheme is most efficient when applied to a scenario composed of all long-lived flows. In a realistic mixed traffic scenario, composed of both long-lived and short-lived TCP flows,…