Quality Authenticator Scheme

This deliverable combines the work described in deliverables D2.1 and D2.2 and defines the common STORK Quality Authentication Assurance framework. It describes how national authentication levels can be mapped onto STORK QAA levels to ensure eID interoperability. Mapping these levels onto each other is not always straightforward. Recommendations are given to ensure proper mapping. Furthermore, legal implications regarding the use of qualified certificates are taken into account in the STORK QAA framework. Solution directions are offered to ensure the legally allowed use of identifiers in STORK.16. Peace, justice and strong institution

Delivering Live Multimedia Streams to Mobile Hosts in a Wireless Internet with Multiple Content Aggregators

We consider the distribution of channels of live multimedia content (e.g., radio or TV broadcasts) via multiple content aggregators. In our work, an aggregator receives channels from content sources and redistributes them to a potentially large number of mobile hosts. Each aggregator can offer a channel in various configurations to cater for different wireless links, mobile hosts, and user preferences. As a result, a mobile host can generally choose from different configurations of the same channel offered by multiple alternative aggregators, which may be available through different interfaces (e.g., in a hotspot). A mobile host may need to handoff to another aggregator once it receives a channel. To prevent service disruption, a mobile host may for instance need to handoff to another aggregator when it leaves the subnets that make up its current aggregator�s service area (e.g., a hotspot or a cellular network).\ud In this paper, we present the design of a system that enables (multi-homed) mobile hosts to seamlessly handoff from one aggregator to another so that they can continue to receive a channel wherever they go. We concentrate on handoffs between aggregators as a result of a mobile host crossing a subnet boundary. As part of the system, we discuss a lightweight application-level protocol that enables mobile hosts to select the aggregator that provides the �best� configuration of a channel. The protocol comes into play when a mobile host begins to receive a channel and when it crosses a subnet boundary while receiving the channel. We show how our protocol can be implemented using the standard IETF session control and description protocols SIP and SDP. The implementation combines SIP and SDP�s offer-answer model in a novel way

Measurements of SIP Signaling over 802.11b Links

The Session Initiation Protocol (SIP) is a popular application-level signaling protocol that is used for a wide variety of applications such as session control and mobility handling. In some of these applications, the exchange of SIP messages is time-critical, for instance when SIP is used to handle mobility for voice over IP sessions. SIP may however introduce significant delays when it runs on top of UDP over lossy (wireless) links. These delays are the result of the exponential back-off retransmission scheme that SIP uses to recover from packet loss, which has a default back-off time of half a second. In this paper, we empirically investigate the delay introduced by SIP when it runs on top of UDP over IEEE 802.11b links. We focus on the operation of SIP at the edge of an 802.11b cell (e.g., to update a mobile host’s IP address after a handoff) as this is where SIP’s retransmissions scheme is most likely to come into play. We experiment with a few 802.11 parameters that influence packet loss on the wireless link, specifically with different link-level retransmission thresholds, signal-to-noise-ratios (SNRs), and amounts of background traffic. We conduct these experiments in a controlled environment that is free from interfering 802.11 sources. Our results indicate that (1) SIP usually introduces little delay except for an SNR range of a few dBs at the very edge of an 802.11 cell in which the delay increases sharply, and (2) that a maximum of four 802.11 retransmissions suffices to limit the delay introduced by SIP retransmissions. The first result is of interest to developers of SIP applications who have to decide at which SNR to initiate a handoff to another network. The second result allows network providers to optimize their 802.11b networks for delay sensitive SIP applications