The evolution and the spreading of wireless access technology and the consequent increase of user mobility will make handover procedures critical for the provision of Quality of Service in the next generation wireless Internet. Often, layer 3 handovers are supposed to be driven by access layer procedures. In this way, the movement detection delay can be reduced, but at the expenses of making the Mobile IP protocol dependent of lower layer implementations. Furthermore, this approach may not be effective when users roam among heterogeneous networks. Nevertheless, movement detection algorithms, which operate at the Mobile IP layer, imply appreciable delays, usually intolerable for real time services. In this paper, we propose a Mobile IP handover scheme based on a novel movement detection algorithm at layer 3, able to timely manage migrations by exploiting advertisements losses, combined with a two-timers mechanism. We analyze the performance of our algorithm in terms of handover delay and throughput, and we show that our solution is able to decrease the movement detection delay as much as 47% with respect to other literature solutions that pursue similar approaches. In addition, this feature implies also higher values of the throughput seen by the TCP layer.

In this paper we propose a movement detection algorithm (MDA) which operates at the Mobile IP layer, in order to render Mobile IP able to timely manage migration, irrespective of the specific lower layer technologies. We also analyze the performance of our algorithm and we show that our solution can decrease the movement detection delay, as much as 47% with respect to other literature solutions that pursue similar approaches.

This work has been carried out in the framework of the Whyless.com project, which aims at providing wireless communications, by exploiting the Ultra Wide Band (UWB) technology, and relying on IP as network layer protocol. Our aim is to analyze the behavior of the Mobile IP protocol in micro-pico cellular wireless networks, where handover events are frequent. We decompose the delay introduced by handover procedures into Movement Detection Delay and Handover Completion Delay. While the latter can be effectively reduced by adopting Micro-mobility frameworks and Smooth Handover strategies, the former is still a challenging issue for developers. We primarily focus on Movement Detection (MD) methods and propose a new effective and flexible algorithms that we call Enhanced Lazy Cell Switching (ELCS). We deeply analyze their performance, putting in evidence that our solution exhibits a better behavior.

Distributed admission control solutions share the idea that no coordination among network routers (i.e. explicit signaling) is necessary, when the decision whether to admit or reject a new offered flow is pushed to the edge of the IP network. Proposed solutions differ in the degree of complexity required in internal network routers, and result in a different robustness and effectiveness in controlling the accepted traffic. This paper presents a Distributed Admission Control algorithm, called GRIP (Gauge&Gate Reservation with Independent Probing), designed to integrate the advantages of a fully distributed operation with the performance effectiveness of CAC mechanisms based on traffic measurements in IP DiffServ environments. We provide a full description and performance evaluation of the algorithm, with extensive simulation results. I. INTRODUCTION T is well known that the IntServ approach, while allowing hard QoS guarantees, suffers of scalability problems in the core network. This has motivated a large research effort to develop a stateless QoS provisioning approach, i.e. the DiffServ paradigm. The idea that per-flow admission control needs to be introduced in IP DiffServ networks, in order to control traffic load and therefore to provide quantifiable service enhancements, is gaining consensus in the Internet research arena. As suggested in the recent RFC [1], in a DiffServ framework, it appears necessary to define an " admission control function, which can determine whether to admit a service differentiated flow along the nominated network path ". In fact, an apparent limit of the DiffServ framework stays in the fact that this approach lacks a standardized admission control scheme, and does not intrinsically solve the problem of controlling congestion in the Internet. Upon overload in a given service class, all flows in that class suffer a potentially harsh degradation of service.

The present paper intends to provide an overview of the solutions and techniques defined in the framework of SUITED project in order to support Internet QoS sensitive mobile services over a satellite and terrestrial complemented system also referred to as Global Mobile Broadband System (GMBS). The designed target system architecture consists of: the EuroSkyWay (ESW) Ka Band satellite system; the GPRS (General Packet Radio Service) land mobile system; the UMTS (Universal Mobile Telecommunication System) system representing the GMBS target solution aiming at complementing the GPRS system; a W-LAN system directly accessing the satellite termination nodes, i.e. the satellite Fixed Earth Stations (FESs), to prolong the satellite link in both indoor and short range outdoor environments; a terrestrial Internet network suitably upgraded with both mobility and QoS support capabilities. The final objective of the proposed GMBS system is to allows a generic user, provided with a GMBS Multi Mode Terminal (GMMT), to access Internet QoS guaranteed services while moving across any possible user environment. I. End-to-End IP QoS Architecture Starting from the IntServ/RSVP [Wroclawsky97] and the DiffServ [Blake98] Internet QoS models, that essentially have complementary features, the approach followed in the framework of SUITED project to provide end-to-end IP QoS over the GMBS system, is based on a hybrid IntServ-DiffServ architecture. The latter, see Figure 1, foresees that in the GMBS system edge portion, consisting of the wireless segments and the edge subnetworks of the terrestrial Internet network, the RSVP protocol is implemented, whereas in the core portion of the terrestrial Internet network, where scalability is a stringent requirement, the scalable DiffServ model is adopted. GMMT Mobile Node ESW Segment

Distributed admission control solutions share the idea that no coordination among network routers (ie, explicit signaling) is necessary, when the decision whether to admit or reject a new offered flow is pushed to the edge of the IP network. Proposed solutions differ in the degree of complexity required in internal network routers, and result in a different robustness and effectiveness in controlling the accepted traffic. This paper builds on a recently proposed distributed admission control solution, called GRIP (Gauge and Gate Reservation with Independent Probing), designed to integrate the flexibility and scalability advantages of a fully distributed operation with the performance effectiveness of admission control mechanisms based on traffic measurements. We show that, in the assumption that traffic sources are dual-leaky-bucket shaped, GRIP allows providing deterministic performance guarantees. Tight QoS performances are made possible even in impulsive load conditions (i.e., sudden activation of several flows), thanks to the introduction of a "stack" mechanism in each network node. A thorough performance evaluation of the conservative effects of the stack shows that the throughput reduction brought about by this mechanism is tolerable, and limited to about 15%

This document consists of two papers. In the first one, we propose an admission control paradigm, called GRIP (Gauge&Gate Reservation with Independent Probing), devised to transparently operate over a stateless IP domain. GRIP relies the decision to admit a new flow upon the successful and timely delivery, through the domain, of probe packets independently generated by the end-points. Failed receptions of probe packets are interpreted as congestion in the network. Our solution is fully distributed and scalable, as admission control decisions are taken at the edge nodes, and no coordination between routers, which are stateless and remain oblivious to individual flows, is required. The performance of GRIP is related to the capability of routers to locally take decisions about the degree of congestion, and suitably block probe packets when congestion conditions are detected. A fundamental feature of the GRIP operation is its backward compatibility (at the expense of experienced performance) with existing routers. This solution has been devised to operate within a specific domain, developed in a R&D project sponsored by the European Union (project SUITED). Thus, in the second part of the document, we describe such domain, where high performance can be obtained, owing to suitable assumptions on the supported traffic. However, nothing impedes to adopt at least the general principles of GRIP in other IP domains or even in the whole Internet.

Providing QoS support over mobile IP networks is a non-trivial task. An important aspect of this issue is that IP mobility does not require intermediate routers to handle connection states, while connection state management is assumed in classical proposals for QoS support (e.g. RSVP), when support of per-flow admission control is aimed at. Such differences in the basic assumptions of QoS and mobility proposals have to be overcome, to provide a comprehensive and homogeneous solution. This paper builds on recent studies, which have proven that per flow admission control is indeed possible over stateless IP frameworks. In particular, the paper shows that a stateless, distributed admission control called GRIP (Gauge and Gate Reservation with Independent Probing) can be applied to Mobile IP scenarios without any major modification in the mobility management mechanism. GRIP relies the decision to admit a new flow upon the successful and timely delivery of IP probe packets independently generated by the end points. When applied within a mobile context, GRIP leaves each mobile node in charge of dynamically selecting the appropriate end point peer during handover. This feature allows limiting the scope of handover-driven admission control procedures to the network part where the path has changed. This is conformant with the spirit of local handover in micromobility architectures. Our proposal is then a first effort towards a joint support of QoS and mobility over a stateless IP domain.

Providing QoS support over mobile IP networks is a non-trivial task. To the best of our knowledge, QoS and mobility issues have been addressed almost separately, and no comprehensive solution is available up to now. In addition, IP mobility is managed at the IP level, and intermediate routers are not required to handle connection states. In the same time, connection state management appears necessary when support of per-flow admission control is aimed at. This paper builds on recent studies, which have proven that per flow admission control is indeed possible over stateless IP frameworks. In particular, the paper shows that a stateless, distributed admission control solution called GRIP (Gauge&Gate Reservation with Independent Probing) can be applied to Mobile IP scenarios without any major modification in the mobility management mechanism. GRIP relies the decision to admit a new flow upon the successful and timely delivery of IP probe packets independently generated by the end points. When applied within a mobile context, GRIP leaves each Mobile Node in charge of dynamically selecting the appropriate end point peer during handover. This feature allows limiting the scope of handover-driven admission control procedures to the network part where the path has changed; this is conformant with the spirit of local handover in micromobility architectures. Moreover, and most important, GRIP does not require even intermediate "anchor" routers to explicitly store any per flow state. Such routers only need to support GRIP as any other end-point terminal, and simply react to independent decisions taken by the mobile terminals. Our proposal is then a first effort towards a joint support of QoS and mobility.