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Dynamic Source Routing (DSR) is an efficient on-demand routing protocol for ad hoc networks, in which only needed routes are found and maintained. The route discovery/setup phase becomes the dominant factor for applications with short-lived small transfer traffic (one single packet or a short stream of packets per transaction) between the source and the destination: resource discovery, text-messaging, object storage/retrieval, queries and short transactions. Route caching is helpful to avoid the need for discovering a route or to shorten route discovery delay before each data packet is sent. The goal of this work is to develop a caching strategy that permits nodes to update their cache quickly to minimize end-to-end delay for short-lived traffic. The proposed approach consists of an Active Packet that travels through the nodes of the network twice. During the first travel, it visits the nodes collecting fresh network topology information. When the first visit is finished, another one is started to validate and update the caches of the nodes with this newly obtained information. This mechanism removes invalid cache links and caches valid links based on the collected topology information. The correct information in caches allows to speed up the Route Discovery and even to avoid it.

In this paper we consider a problem of implementing a hybrid routing protocol for wireless sensor networks, which natively supports data-centric, geographic-based and address-centric communication paradigms. We demonstrate the feasibility of such protocol by presenting tinyLUNAR, an adapted to the specifics of sensor networks reactive routing scheme originally developed for mobile wireless ad hoc networks. In addition to the support for several communications paradigms tinyLUNAR implements highly efficient multihop forwarding using only 1 B field that can be directly encoded in the standard IEEE 802.15.4 MAC header.

In this paper, we analyze backoff protocols, such as Ethernet. We examine a general backoff function (GBF) rather than just the binary exponential backoff (BEB) used by Ethernet. Under some mild assumptions we find stability and optimality conditions for a wide class of backoff protocols with GBF. In particular, it is proved that the maximal throughput rate over the class of backoff protocols with stations is and the optimal average service time for any station is or about for large . The reasons of the instability of the BEB protocol (for a big enough input rate) is explained.

Ethernet protocol originally designed local area networks became very popular and in practice the only protocol used in local and metropolitan networks. Currently both IETF and IEEE are working on some improvements of this protocol to make it more attractive for usage in WAN networks. These modifications may add some additional fields into ethernet header so that the effective maximum transportable data unit will be decreased. From this point follows the problem how to inform upper layers about maximum data unit which ethernet layer can transport. This problem is not addressed in prepared IETF and IEEE standards. This paper tries to point out to this problem and propose some possible solutions.

In this paper, we first analyze the medium access delay of a packet in a terminal in the saturated IEEE 802.11 network. In our analysis, we use the renewal theory to analyze the detailed packet transmission processes of terminals in the network such as the backoff counter freezing. Using our detailed analysis of the packet transmission processes of terminals, we analyze the packet transmission process of a tagged terminal and the background traffic for the tagged terminal which is generated by non-tagged terminals, and derive the Laplace transform of the medium access delay of a packet under the saturated condition. Next, based on the analysis of the medium access delay under the saturated condition, we propose a mathematical model to analyze the packet overflow probability of an unsaturated terminal. We also provide numerical and simulation results to validate our analysis and investigate the characteristics of the system performance.

IEEE 802.11 WLAN, Distributed Coordination Function, Medium Access Delay, Performance Evaluation, Packet Overflow Probability

The BOSS project [1] aims at developing an to transmit large data rate communications between public transport vehicles and the wayside to answer to the increasing need from Public Transport operators for new and/ or enhanced on-board functionality and services, such as passenger security and exploitation such as remote diagnostic or predictive maintenance. As a matter of fact, security issues, traditionally covered in stations by means of video-surveillance are clearly lacking on-board trains, due to the absence of efficient transmission means from the train to a supervising control centre. Similarly, diagnostic or maintenance issues are generally handled when the train arrives in stations or during maintenance stops, which prevents proactive actions to be carried out. The aim of the project is to circumvent these limitations and offer a system level solution. This article focuses on the communication system challenges.

There is ongoing work on the IETF aimed to provide support for different flavors of multihoming configurations, such as SHIM6 for multihomed sites, multiple CoAs support in MIP for multihomed mobile nodes and HIP for multihomed nodes and sites. A critical aspect for all the resulting multihoming protocols is to detect failures and gain information related with the paths available between two hosts. The Failure Detection and Locator Path Exploration Protocol (in short REAchability Protocol, REAP) being defined in the SHIM6 WG of the IETF is a good candidate to be included as a reachability detection component on protocols requiring this functionality. Performance study is performed by combining analytical estimations and simulations to evaluate its behavior and tune its main parameters.

The current architecture of the Internet where anyone can send anything to anybody presents many problems. The recipient of the connection might be using a mobile access network and thus unwanted incoming connections could produce a high cost to the recipient. In addition, denial of service attacks are easy to launch. As a solution to this problem, we propose the Recipient Controlled Session Management Protocol where all incoming connections are denied by the default and the recipient of the connection can choose using certificates what incoming connections are allowed. The recipient can also revoke rights for making an incoming connection at any time.

In this paper we embrace an engineering approach to service delivery over the Internet, by presenting an actual implementation of a conferencing framework compliant with the IP Multimedia Core Network Subsystem (IMS) specification. The architecture we describe has been conceived at the outset by taking into account ongoing standardization efforts inside the various active international bodies. At its current state, it is capable to provide video conferencing facilities with session management capabilities and floor control. The system presented is intended to serve as a running experimental testbed useful for protocol testing, as well as field trials and experimentations. It will be first described from a high level design perspective and subsequently analyzed in further detail by highlighting the most notable implementation choices. A mapping between the actual system components and the corresponding IMS logical functions will be provided and a discussion concerning those parts of the system which somehow depart from the IMS paradigm will be conducted. This on one hand will help the reader figure out potential discrepancies between our solution and the IMS model; on the other hand will open space for discussion around some important open issues on which the international research community still has to attain a rough consensus.