IP (Internet Protocol, Internetworking Protocol) acronym, is a TCP / IP network layer protocol system is the core of the TCP / IP protocol suite, also form the basis of the Internet. IP design aims to improve network scalability: First, solve the problem of the Internet, large-scale, heterogeneous network interconnection intercommunication, emphasizing adaptability, simplicity and operability, and reliability make some sacrifices; Second, the coupling between top dividing network applications and the underlying network technology, in order to facilitate the development of both independent. According to the design principles of end to end, IP only for the host to provide a connectionless, unreliable, best-effort datagram delivery service.
Devices on the network must have at least one unique IP address, the same device can have multiple IP addresses.
Transmitting information on the network depends packet will specify the source and destination addresses. Only a source address, destination address, there is at least one. Depending on the destination address, transmission method can be divided into three kinds: unicast, multicast, and broadcast transmission.
Unicast
Unicast is a one-pass mode. In this mode, the IP packet issued by the source, which is the IP header destination address represent a single destination device, so that only the destination device can receive the IP packet. Information packets transmitted over the Internet, the vast majority are single point IP packet transmission.
Broadcast transmission
broadcast transmission is a one to many transmission method. In this manner, IP packets sent by the source device, the destination address of an IP header on behalf of a network, rather than a single device, all devices within the network can receive and process broadcast information, such IP package. Because of this feature, broadcast packets must be used with care, otherwise the slightest mistake, it will spread to all of the devices within the network.
Multicast
Multicast mode is a transfer mode interposed between unicast and broadcast transmission. Multicast transmission is also part of one to many, but it is very different from the broadcast transmission. Broadcast transmission must be sent to all devices within a network, but they can transmit multicast packets to a group of the specified device. That Multicast IP packet destination address on behalf of its IP header is a group selected device. Those who belong to this group of devices can receive the multicast packets.
The reason why the multicast approach is: Suppose we want to copy the data must be transferred to the specified device on the network 10. If you use unicast, the operation must be repeated 10 times in order to achieve the purpose of the transfer is not only inefficient and wasteful of network bandwidth. If broadcast transmission mode, all the network is specified (e.g., 20) receives the computer, and must process the broadcast transport packets, in other words, will affect unrelated to other computers. At this time, if you are using multicast, will be able to avoid a single problem with the transmission of broadcast transmission point.
Multicast is ideal for transferring some of the real-time information sharing to a group of users, such as video conferencing, broadcast and other parties. However, while multicasting is no technical problem in the same network, but if you want through the Internet, the router must support along the way of the relevant agreements for the job, which is the multicast bottleneck faced.
