Introduction to the application of multicast technology (1)

IP multicast technology has been around for a long time, but it is only the beginning of the IP multicast era. We believe that IP multicast is one of the most exciting network technologies that have emerged since the promotion of WWW technology.
As the bandwidth of the backbone network increases, the special network video/audio becomes possible, and the video/audio applications in the residential network are continuously enriched. The emergence of such applications that rely on multicast technologies makes the support for Multicast technology an important part of network construction.
Currently, the domain multicast routing protocol of the dense distribution model is PIM. The full name of PIM protocol is "protocol-Independent Multicast Routing Protocol", which is mainly used in routers. It is also widely used in high-end multi-layer switches. It is not limited by the network size, and its applications are very flexible.
The IP multicast technology is based on the idea of optimizing the business communication structure. In some services, a certain number of users are receiving identical data streams. If the IP Unicast technology is used to serve these users, the sender needs to create a separate data stream for each user. Because these data streams repeatedly send identical data, the load on the sending host and communication network is greatly increased, and it is difficult to guarantee the fairness of the services of different recipients. However, the multicast technology only requires the sender to send a data stream for the same data, and select an appropriate communication device through the network, copy the same data stream for different users to reduce the host service load, network communication load, and achieve Service Fairness.
Multicast Applications can be divided into three types: point-to-point applications, point-to-point applications, and point-to-point applications.
Currently, it is difficult for multicast applications to provide effective user authentication and billing methods, and there is a lack of mature commercial Foundation. At the same time, there is also a lack of effective measures to ensure the quality of service, this includes latency, loss rate, and support for heterogeneous links. Currently, these problems are mainly solved by the application itself.
The following uses a harbor switch that supports PIM as an example to discuss three network modes.
Point-to-point applications
Point-to-point applications refer to the Application Form of one sender and multiple receivers. This is the most common form of multicast applications. Typical applications include:
Media broadcast: events on schedule, such as presentations, presentations, and meetings. Traditional media distribution methods generally use television and broadcasting. This type of applications usually require one or more data streams at a constant rate. When multiple data streams are used, such as voice and video, they usually need to be synchronized and have different priorities. They usually require high bandwidth and low latency jitter, but they do not require high absolute latency.
Media push: such as news titles, weather changes, sports scores, and other non-commercial key dynamic changes. They require low bandwidth and no latency requirements.
Information Caching: such as website information, code execution, and other file-based distributed replication or cache updates. They generally require bandwidth and latency.
Event Notification: such as network time, multicast session schedule, random numbers, keys, Configuration updates, network alarms for effective ranges, or other useful information. They have different bandwidth requirements, but generally have relatively low requirements for latency.
Status Monitoring: such as stock prices, sensing devices, security systems, production information, or other real-time information. Such bandwidth requirements vary according to the sampling period and precision, and may have a constant rate bandwidth or burst bandwidth requirements. Generally, the bandwidth and latency requirements are average.
Point-to-Point application network device connection topology 1 is shown.
Multi-Point-to-multi-point applications
Multi-Point-to-Multi-Point application refers to the application form of multiple senders and multiple receivers. Generally, each receiver can receive data sent by multiple senders, and each sender can send data to multiple receivers. Typical applications include:
Multi-Point Meeting: Generally, audio/video and whiteboard applications constitute multi-point meeting Applications. In multi-point meetings, different data streams have different priorities. Traditional multi-point conferences use dedicated multi-point control units to coordinate and allocate them. Multicast can be directly sent to all receivers by any single sender. The multi-point control unit is used to control the current voice. Such applications require high bandwidth and latency.
Resource synchronization: synchronization of distributed databases such as schedules, directories, and information. They generally require bandwidth and latency.
Parallel Processing: such as distributed parallel processing. It has high requirements on bandwidth and latency.
Collaborative processing: such as editing shared documents. It generally requires bandwidth and latency.
Remote Learning: This is actually the support of the media broadcast application and the support for upstream data streams that allow students to ask questions to their teachers. It generally requires bandwidth and latency.