The difference between multicast and broadcast

You must first understand the definitions of multicast and broadcast:

##Multicast(multicasting) is A form of multicast delivery that uses hardware technology to communicate by using a large number of multicast addresses. When a group of machines needs to communicate, a multicast address is selected, the corresponding network interface hardware is configured, the multicast address is identified, and a copy of the group on the multicast address is received. (Recommended learning: PHP video tutorial)

There are not many applications of network technology. Online video conferencing and online video viewing are particularly suitable for multicast methods.

Multicast in IP networks is generally implemented through multicast IP addresses. Multicast IP addresses are Class D IP addresses, which are IP addresses between 224.0.0.0 and 239.255.255.255. The DHCP manager in Windows 2000 supports automatic allocation of multicast IP addresses.

Broadcasting (Broadcasting) is the most common form of multicast delivery, which delivers a copy of the packet to each destination station. This can be accomplished by delivering multiple single packets, or by passing copies of the packets over separate connections until each recipient has received a copy.

A large number of broadcast packets cannot appear in the network for a long time, otherwise a so-called "broadcast storm" will occur. Broadcast storm means that the network is occupied by a large number of broadcast packets for a long time, normal point-to-point communication cannot be carried out normally, and the external performance is that the network speed is extremely slow. There are many reasons for broadcast storms. A faulty network card may send broadcast packets to the network for a long time, causing broadcast storms.

Broadcast storms cannot be completely eliminated, but they can only propagate within the same subnet, just like the sound of a loudspeaker can only propagate within the same venue. Therefore, in a large network composed of hundreds or even thousands of computers, In medium-sized LANs, subnets are generally divided, just like dividing a hall into many small halls with walls, in order to achieve the purpose of isolating broadcast storms.

In the IP network, the broadcast address is represented by the IP address "255.255." This IP address represents all IP addresses in the same subnet.

"Multicast" is also known as "Multicast" can be understood as one person speaking to multiple people (but not everyone present), which can improve the efficiency of the call. If you want to notify specific people of the same thing, but don't want to Others know that it is very troublesome to use the phone to notify one by one, and using the loudspeakers used in daily life to broadcast notifications will not achieve the purpose of notifying only individual people. In this case, it will be very convenient to use "multicast" to achieve it. It is fast, but there are very few multicast equipment in real life.

"Broadcast" can be understood as a person talking to all the people present through the broadcast speaker. The advantage of this is that the call efficiency is high and the information is all at once It can be passed to everyone.

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