SUMMARYMulticast communications concern the transfer of data among multiple users. Multicast communications can be provided at the network layer-an example is IP multicast-or at the application layer, also called overlay multicast. An important issue in multicast communications is to control how different userssenders, receivers, and delivery nodes-access the transmitted data as well as the network resources. Many researchers have proposed solutions addressing access control in IP multicast. However, little attention has been paid to overlay multicast. In this paper, we investigate the access control issues in overlay multicast and present OMAC: a new solution to address these issues. OMAC provides access control for senders, receivers, and delivery nodes in overlay multicast. The proposed architecture, which is based on symmetric key cryptosystem, centralizes the authentication process in one server whereas it distributes the authorization process among the delivery nodes. Moreover, delivery nodes are utilized as a buffer zone between end systems and the authentication server, making it less exposed to malicious end systems. To evaluate our work, we have used simulation to compare the performance of OMAC against previous solutions. Results of the simulation show that OMAC outperforms previous multicast access control schemes.

Background: Mechanical neck dysfunction (MND) is a common disorder prevailing among the individuals of different populations. It is characterized by pain and limited range of motion (ROM) which, in turn, affects the activities of daily living and quality of life. Although manual therapy is commonly used in MND treatment to restore a range of motion and reduce pain, some techniques have low evidence in treating MND. Aim: This study was conducted to compare the effect of sustained natural apophyseal glides (SNAGs) with positional release therapy (PRT) on cervical ROM, pain intensity, and functional disability in patients with chronic mechanical neck dysfunction. Methods: One hundred and twenty patients from both genders, where they were divided randomly into three groups. Group A received conventional physical therapy, group B received conventional therapy in addition to SNAGs, and group C received conventional therapy plus PRT three times per week for eight weeks. The universal goniometer was used to measure cervical ROM, numeric pain rating scale (NPRS) was used to measure pain intensity, and neck disability index was used to measure cervical function disability at two intervals, pretreatment and post-treatment. Results:The results showed significant difference in the cervical ROM, NPRS, and NDI between the three groups (p < 0.001) in favor of the group B. Conclusion: SNAGs with conventional physical therapy have been proven to be effective method in treating patients with chronic mechanical neck dysfunction patients.

No abstract

No abstract

No abstract