Abstract
The multimedia applications generally support one-tomany group communication. Multicasting decreases the communication costs for applications, which send the same data to multiple receivers. Table 1 summarizes the types of the communication among the hosts. Currently, there is an increasing need for scalable and efficient group communication. Theoretically, multicasting is optimal for such purposes. Therefore, this technology is an emerging media dissemination technology, instead of the traditional unicast communication. It has two important types: the networklevel, namely IP-multicast, and the Application-Layer, host-multicast. In the former one, the data packets are delivered by the IP protocol, from one host to many hosts that are member of a multicast group. The routers run an IP-multicast routing protocol in order to construct a multicast tree. Along this tree, the data is forwarded to each host. Special IP addresses (224.0.0.0 - 239.255.255.255 address range) are used, which do not belong to hosts, but rather define multicast channels. In the case of Application-Layer Multicast (ALM), the hosts use unicast IP delivery, and the routers do not play any special role. Reliability is one of the most important features of all multimedia applications, independently from the multicast technology in use. This requirement is especially critical in the case of multicast, where the large volume of data is to be transferred, and correction or resending of lost data is even more difficult in time. In the multicast technology, the maintenance of the group membership information is also an important question from the point of view of the robustness of the so-called multicast delivery tree. The root of the tree is the sender, the leaves are the receivers, and the intermediate nodes are the routers in case of the IP-multicast. In the following sections, the reliability properties of different multicast technologies are overviewed.
TopIntroduction
The multimedia applications generally support one-to-many group communication. Multicasting decreases the communication costs for applications, which send the same data to multiple receivers. Table 1 summarizes the types of the communication among the hosts.
Table 1. The possible types of the communication among the hosts
| Type | Name | Description |
| point-to-point | unicast | One host communicates with another. |
| point-to-multipoint | multicast | One host (sender) send data to a group of hosts, the sender sends data only once and every member of the group will receive. |
| multipoint-to-multipoint | multipoint multicast | In a communication session more than one sender exist, which independently send data to every member of the group |
| multipoint-to-point | concast | The every member of the group sends data to only one host. |
| point-to- everypoint | broadcast | One host sends data to every host. |
Currently, there is an increasing need for scalable and efficient group communication. Theoretically, multicasting is optimal for such purposes. Therefore, this technology is an emerging media dissemination technology, instead of the traditional unicast communication. It has two important types: the network-level, namely IP-multicast, and the Application-Layer, host-multicast. In the former one, the data packets are delivered by the IP protocol, from one host to many hosts that are member of a multicast group. The routers run an IP-multicast routing protocol in order to construct a multicast tree. Along this tree, the data is forwarded to each host. Special IP addresses (224.0.0.0 - 239.255.255.255 address range) are used, which do not belong to hosts, but rather define multicast channels. In the case of Application-Layer Multicast (ALM), the hosts use unicast IP delivery, and the routers do not play any special role.
Reliability is one of the most important features of all multimedia applications, independently from the multicast technology in use. This requirement is especially critical in the case of multicast, where the large volume of data is to be transferred, and correction or resending of lost data is even more difficult in time.
In the multicast technology, the maintenance of the group membership information is also an important question from the point of view of the robustness of the so-called multicast delivery tree. The root of the tree is the sender, the leaves are the receivers, and the intermediate nodes are the routers in case of the IP-multicast. In the following sections, the reliability properties of different multicast technologies are overviewed.
Key Terms in this Chapter
AJAX: The Asynchronous JavaScript and XML is a Web development technique used for creating interactive Web applications.
Software Project: An educational activity where students are required to develop or specify a program following guidelines and requirements that were previously established.
CSCL: The computer supported collaborative learning is a research area that uses software and hardware to provide an environment for collaborative learning.
FTP: The file transfer protocol is a protocol to transfer files from one computer to another over the Internet.
UDF: The unit development folder is a kind of structured report to describe a development process.
Web 2.0: A perceived second generation of Web-based communities and hosted services, such as social-networking sites and wikis, which aim to facilitate collaboration and sharing between users.
Peer Review Method: Peer review is a process used for checking the work performed by one’s equals (peers) to ensure it meets specific criteria. The peer review method uses peer review to evaluate assignments from student groups.
Collaborative Learning: An instruction method in which students work in groups toward a common academic goal.
Individual Learning: An instruction method in which students work individually at their own level?and rate toward an academic goal.