The Impact of TLS on SIP Server Performance

This report studies the performance impact of using TLS as a transport protocol for SIP servers. We evaluate the cost of TLS experimentally using a testbed with OpenSIPS, OpenSSL, and Linux running on an Intel-based server. We analyze TLS costs using application, library, and kernel profiling, and use the profiles to illustrate when and how different costs are incurred, such as bulk data encryption, public key encryption, private key decryption, and MAC-based verification. We show that using TLS can reduce performance by up to a factor of 20 compared to the typical case of SIP over UDP. The primary factor in determining performance is whether and how TLS connection establishment is performed, due to the heavy costs of RSA operations used for session negotiation. This depends both on how the SIP proxy is deployed (e.g., as an inbound or outbound proxy) and what TLS options are used (e.g., mutual authentication, session reuse). The cost of symmetric key operations such as AES or 3DES, in contrast, tends to be small. Network operators deploying SIP over TLS should attempt to maximize the persistence of secure connections, and will need to assess the server resources required. To aid them, we provide a measurement-driven cost model for use in provisioning SIP servers using TLS. Our cost model predicts performance within 15 percent on average

A comparison of social information processing in children with and without reactive attachment disorder and the association with behavioural difficulties

The aims of this cross-sectional case-control study were to explore the social information processing (SIP) patterns of children with reactive attachment disorder (RAD) and their association with behavioural difficulties. The sample consisted of 23 children with RAD aged 4-12 matched by age and gender with a comparison sample of typically developing peers. Children completed an assessment package investigating the encoding, interpretation, response access and response evaluation components of SIP and their intellectual functioning and verbal comprehension, while caregivers completed two instruments measuring child behavioural difficulties. The children with RAD displayed significantly more errors in encoding, interpretation and response evaluation than the comparison group. There was also a tendency for children with RAD to access more aggressive responses than comparison children. In addition, there were strong associations between aspects of SIP and child behavioural difficulties, with the strongest association between encoding and emotional problems. However, both intellectual functioning and verbal comprehension were significantly associated with behavioural difficulties suggesting these variables may impact on the relationship between SIP and behavioural difficulties. The overall findings suggest that children with RAD process social information in a biased manner and this is partially associated with behavioural outcomes. The strengths and limitations of the study are discussed in addition to suggestions for future research

ATTENTIONAL BIAS AND ALCOHOL ABUSE

Selective attention towards alcohol-related cues (i.e., “attentional bias”) is thought to reflect increased incentive motivational value of alcohol and alcohol cues acquired through a history of heavy alcohol use, and as such attentional bias is considered to be a clinically relevant factor contributing to alcohol use disorders. This dissertation consists of two studies that investigated specific mechanisms through which attentional bias might serve to promote alcohol abuse. Study 1 compared magnitude of attentional bias in heavy (n = 20) and light (n = 20) drinkers following placebo and two doses of alcohol (0.45 g/kg and 0.65 g/kg). Heavy drinkers displayed significantly greater attentional bias than did moderate drinkers following placebo. However, heavy drinkers displayed a dose-dependent decrease in response to alcohol. Individual differences in attentional bias under placebo were associated with both self-reported and laboratory alcohol consumption, yet bias following alcohol administration did not predict either measure of consumption. These findings suggest that attentional bias is strongest before a drinking episode begins, and as such might be most influential in terms of initiation of alcohol consumption. Study 2 addressed theoretical accounts regarding potential reciprocal interactions between attentional bias and inhibitory control that might promote excessive alcohol consumption. Fifty drinkers performed a measure of attentional bias and a novel task that measures the degree to which alcohol-related stimuli can increase behavioral activation and reduce the ability to inhibit inappropriate responses. As hypothesized, inhibitory failures were significantly greater following alcohol images compared to neutral images. Further, heightened attentional bias was associated with greater response activation following alcohol images. These findings suggest that alcohol stimuli serve to disrupt mechanisms of behavioral control, and that heightened attentional bias is associated with greater disruption of control mechanisms following alcohol images. Taken together, these studies provide strong evidence of an association between attentional bias in sober individuals and alcohol consumption, suggesting a pronounced role of attentional bias in initiation of consumption. Further, findings show that attention to alcohol cues can serve to disrupt mechanisms of inhibitory control that might be necessary to regulate drinking behavior, suggesting a potential means through which attentional bias might promote consumption

Simulation-based optimization of signaling procedures in IP multimedia subsystem

This paper presents a simulation-based optimization of signaling procedures in Internet protocol Multimedia Subsystem (IMS). The aim is to improve the performance of signaling procedures by applying an algorithm for Session Initiation Protocol (SIP) message classification and prioritization that is proposed in our previous work. This three-priority level classification of SIP messages is implemented in Network Simulator version 2 (ns-2). Its effectiveness is verified through the simulation-based study of SIP signaling procedures under different conditions. The simulation results are analyzed in terms of Registration Request Delay (RRD), Session Request Delay (SRD), and Session Disconnect Delay (SDD). These SIP performance metrics are improved if IMS is configured to process SIP messages using the proposed algorithm. Differentiated handling of SIP messages reduces the overload in IMS and thereby improves the overall Quality of Service (QoS). This encourages our next step in research activity, i.e., implementation and incorporation of SIP message classification and prioritization algorithm into experimental environment

Growth, Yield, and Water Productivity Responses of Pepper to Sub-Irrigated Planter Systems in a Greenhouse

A sub-irrigated planter (SIP) is a container irrigation technique in which water is supplied to the crop from the bottom, stored in a saturated media-filled reservoir beneath an unsaturated soil, and then delivered by capillary action to the root zone. The aim of this study was to optimize the water management and to assess the performance of this technique in terms of water use efficiency, soil moisture, and solute distribution in comparison with surface irrigation in a Mediterranean greenhouse. The experiment consisted of four SIP treatments, with a constant water level in the bottom reservoir in order to evaluate the effect of two different irrigation salinities (1.2 and 2.2 dS m−1) and two depths of substrate profiles (25 and 15 cm). The results showed that SIP is capable of significantly improving both water-use efficiency and plant productivity compared with surface irrigation. Also, a 24% average reduction in water consumption was observed while using SIP. Moreover, SIPs with a higher depth were recommended as the optimum treatments within SIPs. The type of irrigation method affected the salinity distribution in the substrate profile; the highest salinity levels were registered at the top layers in SIPs, whereas the maximum salinity levels for the surface treatments were observed at the bottom layers. SIPs provide a practical solution for the irrigation of plants in areas facing water quality and scarcity problems

Effectiveness of Urban Shelter-in-Place. II: ResidentialDistricts

In the event of a short-term, large-scale toxic chemical release to the atmosphere, shelter-in-place (SIP) may be used as an emergency response to protect public health. We modeled hypothetical releases using realistic, empirical parameters to explore how key factors influence SIP effectiveness for single-family dwellings in a residential district. Four classes of factors were evaluated in this case-study: (a) time scales associated with release duration, SIP implementation delay, and SIP termination; (b) building air-exchange rates, including air infiltration and ventilation; (c) the degree of sorption of toxic chemicals to indoor surfaces; and (d) the shape of the dose-response relationship for acute adverse health effects. Houses with lower air leakage are more effective shelters, and thus variability in the air leakage of dwellings is associated with varying degrees of SIP protection in a community. Sorption on indoor surfaces improves SIP effectiveness by lowering the peak indoor concentrations and reducing the amount of contamination in the indoor air. Nonlinear dose-response relationships imply substantial reduction in adverse health effects from lowering the peak exposure concentration. However, if the scenario is unfavorable for sheltering (e.g. sheltering in leaky houses for protection against a nonsorbing chemical with a linear dose-response), the community must implement SIP without delay and exit from shelter when it first becomes safe to do so. Otherwise, the community can be subjected to even greater risk than if they did not take shelter indoors