IPv6 Multicast Forwarding in RPL-Based Wireless Sensor Networks

In wireless sensor deployments, network layer multicast can be used to improve the bandwidth and energy efficiency for a variety of applications, such as service discovery or network management. However, despite efforts to adopt IPv6 in networks of constrained devices, multicast has been somewhat overlooked. The Multicast Forwarding Using Trickle (Trickle Multicast) internet draft is one of the most noteworthy efforts. The specification of the IPv6 routing protocol for low power and lossy networks (RPL) also attempts to address the area but leaves many questions unanswered. In this paper we highlight our concerns about both these approaches. Subsequently, we present our alternative mechanism, called stateless multicast RPL forwarding algorithm (SMRF), which addresses the aforementioned drawbacks. Having extended the TCP/IP engine of the Contiki embedded operating system to support both trickle multicast (TM) and SMRF, we present an in-depth comparison, backed by simulated evaluation as well as by experiments conducted on a multi-hop hardware testbed. Results demonstrate that SMRF achieves significant delay and energy efficiency improvements at the cost of a small increase in packet loss. The outcome of our hardware experiments show that simulation results were realistic. Lastly, we evaluate both algorithms in terms of code size and memory requirements, highlighting SMRF’s low implementation complexity. Both implementations have been made available to the community for adoption.     

Does incision of the tunica vaginalis during the Palomo procedure prevent post-operative hydrocele?

OBJECTIVE: To assess whether incision of the tunica vaginalis of the ipsilateral testis during the Palomo procedure affects the incidence of post-operative hydrocele. PATIENTS AND METHODS: Forty-two patients with varicocele were treated between 1992 and 1996, all undergoing the Palomo procedure. In 15 patients, incision of the tunica vaginalis of the ipsilateral testis was performed with the Palomo procedure, to prevent the formation of hydrocele. All patients were followed at regular intervals, for 3 months to 4 years. RESULTS: Of 27 patients who underwent the Palomo procedure alone, four developed post-operative hydrocele requiring operation. None of those who underwent incision of the tunica vaginalis with the Palomo procedure developed a hydrocele. The duration of hospital stay was the same in both groups (mean 2.5 days). During the follow-up, there was no difference in the size of the testes, as assessed with the Prader orchidometer, between the two groups. CONCLUSION: Incision of the tunica vaginalis of the ipsilateral testis in addition to the Palomo procedure prevents the development of post-operative hydrocele and causes no adverse sequelae.     

Timestamping schemes for MPEG-2 systems layer and their effect onreceiver clock recovery

We propose and analyze several strategies for performing timestamping of an MPEG-2 Transport Stream transmitted over a packet-switched network using the PCR-unaware encapsulation scheme, and analyze their effect on the quality of the recovered clock at the MPEG-2 Systems decoder. When the timestamping scheme is based on a timer with a fixed period, the PCR values in the packet stream may switch polarity deterministically, at a frequency determined by the timer period and the transport rate of the MPEG signal. This, in turn, can degrade the duality of the recovered clock at the receiver beyond acceptable limits. We consider three timestamping schemes for solving this problem: (1) selecting a deterministic timer period to avoid the phase difference in PCR values altogether, (2) fine-tuning the deterministic timer period to maximize the frequency of PCR polarity changes, and (3) selecting the timer period randomly to eliminate the deterministic PCR polarity changes. For the case of deterministic timer period, we derive the frequency of the PCR polarity changes as a function of the timer period and the transport rate, and use it to find ranges of the timer period for acceptable quality of the recovered clock. We also analyze a random timestamping procedure based on a random telegraph process and obtain lower bounds on the rate of PCR polarity changes such that the recovered clock does not violate the PAL/NTSC clock specifications. The analytical results are verified by simulations with both synthetic and actual MPEG-2 Transport Streams sent to a simulation model of an MPEG-2 Systems decoder     

Conservative treatment of hemangiomas in infancy and childhood with interferon-alpha 2a

Hemangioma is the most common tumor of infancy. Most hemangiomas proliferate for 8 to 18 months and then slowly regress over the next 5 to 8 years. So far, steroids have been the established means of treatment, but there have been some reports of the use of interferon-alpha 2a (IFN-A2a) in such tumors. To evaluate the efficacy of IFN-A2a in treating giant hemangiomas in infancy and childhood, we administered it to ten patients aged 4 h to 6.5 years with life-threatening hemangiomas in various parts of the body. The dose used was 3 MU/m2 body surface area subcutaneously every second day. All children had previously received corticosteroids for 2 to 5 weeks without obvious success. The results were satisfactory: five patients had total or almost total regression; the rest have had partial regression while treatment is still in progress. A flu-like syndrome with fever, rhinitis, etc. accompanied the injections in some patients. The symptoms were controlled with paracetamol as necessary. Mild, transient leukopenia occurred in some children as well, but subsided after cessation of therapy for 1 week. IFN-A2a appears to be a promising and well-tolerated element in the treatment of life-threatening hemangiomas in infancy and childhood.     

Efficient algorithms for computation of the burstiness curve of video sources

The burstiness of a video source can be characterized by its burstiness curve. The burstiness curve is useful in the optimal allocation of resources to satisfy a desired quality of service for the video stream in a packet network. In this paper, we present deterministic algorithms for exact computation of the burstiness curve of a video source, for both elementary video streams and MPEG-2 Transport Streams. The algorithms exploit the piecewise linearity of the burstiness curve and compute only the points at which the slope of the burstiness curve changes. We also present approximate versions of these algorithms, which save computational effort by considering only a small number of candidate points at which the slope of the burstiness curve may change. The approximate algorithm was able to compute the burstiness curve of a 2-h long elementary video stream in approximately 10 s, as compared to over 6 h for the exact algorithm, with virtually no loss of accuracy in the computation. The efficiency of the proposed algorithms makes them suitable for quality-of-service (QoS) provisioning not only in off-line environments such as in video-on-demand (VoD) servers, but also in real-time applications such as in live TV distribution systems.     

A lightweight web-based vulnerability scanner for small-scale computer network security assessment

There appears to be a common perception amongst average computer users pointing towards a global lack of trust when using the Internet. The resolution of this lack of trust relating to the use of the Internet, particularly orientated towards its commercial use and online purchasing, requires partly from website developers to create and maintain web applications that are robust and provide a certain degree of resilience to attack from outside threats. This project intends to contribute to this particular aspect by providing site developers and system testers, as well as simple site users, with a tool for reconnaissance, vulnerability scanning and remote network mapping that is easily accessible and useable due to its web-based and visual, event-driven interface. It is anticipated that the cumbersome task of learning to use a number of command line tools and their exact functionality and parameters can be avoided through this and similar developments, and hence that this will potentially widen the access to security testing, particularly to small and medium businesses.     

Efficient algorithms for computation of the loss curve of video sources

The loss curve of a video source characterizes the loss rate of the video stream generated by the source as a function of the allocated buffer size for a given transmission rate. The loss curve is useful in the optimal allocation of resources when the video stream is transmitted over a packet network, so that the desired tradeoff can be reached among the loss rate, bandwidth and the buffer space to be allocated in the network. We present an algorithm for computation of the entire loss curve of an elementary video stream. In contrast to earlier algorithms which employ statistical approaches, our algorithm is deterministic and computes the exact loss curve of the video stream. The algorithm exploits the piecewise linearity of the loss curve and computes only the points at which the slope of the loss curve changes. We also present an extension of the algorithm to MPEG-2 transport streams. The efficiency of the algorithm is demonstrated by results from several example video streams. For example, the algorithm was able to compute the entire loss curve of a 2-h elementary video stream in approximately 11 s on a Sun Ultra-2 workstation.