Performance of Meshed Tree Protocols for Loop Avoidance in Switched Networks

Loop free frame forwarding in layer 2 switched networks that use meshed topologies to provision for link and path redundancy is a continuing challenge. The challenge is addressed through special protocols at layer 2 that build logical trees over the physically meshed topologies, along which frames can be forwarded. The first such protocol was based on the spanning tree. The spanning tree protocol (STP) had high convergence times subsequent to topology changes. Rapid STP and IETF RFC 5556 Transparent Interconnection of Lots of Links (TRILL) on Router Bridges (RBridges) were then developed to reduce the convergence times. RSTP cntinued to use the spanning tree while TRILL adopted link state routing to support a tree from every switch. TRILL introduces high processing complexity into layer 2 networks. In this article a new meshed tree algorithm (MTA) and a loop avoidance protocol based on the MTA, namely the meshed tree protocol (MTP) are discussed. The MTA allows constructing several overlapping trees from a single root switch. This speeds up convergence to link failures. The MTP proposes a simple numbering scheme to implement meshed trees – thus, the processing complexity is low. The specification for the MTP is currently an ongoing IEEE standard Project 1910.1. In this article the operational details of MTP are presented and its performance evaluated and compared with RSTP

Integrating adolescent livelihood activities within a reproductive health program for urban slum dwellers in India

The Population Council’s Frontiers in Reproductive Health (FRONTIERS) program and Policy Research Division, in collaboration with CARE India, conducted an operations research study in Allahabad, Uttar Pradesh to examine the feasibility and impact of adding livelihood counseling and training, savings formation activities, and follow-up support to an ongoing reproductive health program for adolescents. The short-term objective of the study was to foster development of alternative socialization processes for adolescent girls that encourage positive sexual and reproductive health behaviors. The study also aimed to produce a replicable model for CARE and other agencies to use in adding livelihood activities to adolescent reproductive health programs. Results from the midline survey showed a positive impact of the intervention in terms of increased skill use, changing time use patterns, increased work aspirations, and more progressive gender role attitudes. Girls expressed satisfaction with the courses and trainers; many used their skills after completing the vocational courses; and they expressed a desire for the adolescent meetings to continue, seeing them as a time to relax and mingle with their peers

Structural Basis for Dual-Inhibition Mechanism of a Non-Classical Kazal-Type Serine Protease Inhibitor from Horseshoe Crab in Complex with Subtilisin

Serine proteases play a crucial role in host-pathogen interactions. In the innate immune system of invertebrates, multi-domain protease inhibitors are important for the regulation of host-pathogen interactions and antimicrobial activities. Serine protease inhibitors, 9.3-kDa CrSPI isoforms 1 and 2, have been identified from the hepatopancreas of the horseshoe crab, Carcinoscorpius rotundicauda. The CrSPIs were biochemically active, especially CrSPI-1, which potently inhibited subtilisin (Ki = 1.43 nM). CrSPI has been grouped with the non-classical Kazal-type inhibitors due to its unusual cysteine distribution. Here we report the crystal structure of CrSPI-1 in complex with subtilisin at 2.6 Å resolution and the results of biophysical interaction studies. The CrSPI-1 molecule has two domains arranged in an extended conformation. These two domains act as heads that independently interact with two separate subtilisin molecules, resulting in the inhibition of subtilisin activity at a ratio of 1:2 (inhibitor to protease). Each subtilisin molecule interacts with the reactive site loop from each domain of CrSPI-1 through a standard canonical binding mode and forms a single ternary complex. In addition, we propose the substrate preferences of each domain of CrSPI-1. Domain 2 is specific towards the bacterial protease subtilisin, while domain 1 is likely to interact with the host protease, Furin. Elucidation of the structure of the CrSPI-1: subtilisin (1∶2) ternary complex increases our understanding of host-pathogen interactions in the innate immune system at the molecular level and provides new strategies for immunomodulation

Mobility prediction for seamless mobility in wireless networks

One of the requirements for seamless mobility is efficient resource reservation and context transfer procedures during handoff. If context transfer and resource reservation can occur prior to handoff continuation of the same level of service as at the previous connection point is possible. Resource reservation is required to be non-aggressive for optimal use of limited bandwidth and a low call-blocking probability. In this work we present a method of mobility prediction that can aid in achieving seamless mobility. In order to optimise the efficiency of a resource reservation algorithm we believe accurate prediction of the future movements of the user is required.<br /

User mobility prediction in hybrid and ad hoc wireless networks

Next Generation Networks will employ hybrid network architectures using both cellular and ad hoc networking concepts. The vision of real-timemultimedia services requires that mobility management be addressed in a proactive manner. If the user movements can be predicted accurately in ahybrid network environment then handoff/cluster change, resource reservation and context transfer procedures can be efficiently completed as required by node mobility. In this work we propose a sectorized ad hoc mobility prediction scheme for cluster change prediction. Simulation study of the scheme shows it to be efficient in terms of prediction accuracy and prediction related control overhead despite randomness in user movement.<br /

A Secure Cloud Internetwork Model with Economic and Social Incentives (SCIMES)

The Internet has exponentially expanded to meet the new demands placed on its ever-growing network structure. However, its original data-sharing design cannot address issues, such as malware, Distributed Denial of Service, or the increased need to offer more reliable and trusted connections. With trusted connections come more revenue, reduced risks, and a greater variety of services. However, without incentives to provide better services, infrastructure and service providers have no reason to build a better Internet. The Secure Cloud Internetwork Model with Economic and Social Incentives (SCIMES) provides the framework via a new internetwork model that will support trust ratings, as well as secure social and economic choice mechanisms to promote a more secure Internet. This in turn will result in more revenue for providers and greater benefits for users