Unicast, multicast and broadcast are all used to describe the communication mode between network nodes.
So what do these terms mean? What is the difference?
1. unicast: the communication between network nodes is like a dialogue between people.
Suppose one person speaks to another. So the description of narration in terms of network technology is unicast. At this time, the information receiving and transmission is only between the two nodes. Unicast has been widely used in the network. Most of the data on the network is transmitted in unicast, only the general network users do not know.
For example, when you send and send e-mail and browse web pages, you must establish a connection with the email server and webserver. At this time, you use unicast transmission data mode. However, point to point communication is usually used instead of unicast, because unicast is generally used in correspondence with multicast and broadcast.
2. multicast: "multicast" can also be called "multicast". The application of network technology is not very much, online video conference and online video on demand are especially suitable for multicast.
Because it is assumed that unicast is adopted, the transmission process will be performed several times for how many target nodes are transmitted one by one, which is obviously very inefficient. It is not desirable; Assume that all broadcast modes are not target sensitive and all transmissions are used. Although it can be transmitted at one time. But it is obvious that the purpose of distinguishing specific data receiving objects can not be achieved. Multicast can not only transmit all the data of target nodes at a time, but also can only transfer data to specific objects.
Multicast in IP network is usually realized by multicast IP address.
Multicast IP address is a class D IP address. That is, the IP address between 224.0.0.0 and 239.255.255.255.255.
The DHCP manager in Windows 2000 supports the active assignment of multicast IP addresses.
3. broadcast: "broadcast" is widely used in the network, such as the process that clients obtain IP address through DHCP
themselves is realized by broadcasting. However, compared with unicast and multicast, broadcast takes up all the bandwidth of the network in the subnet. Take a meeting and play one example. There is only one person speaking in the meeting. Imagine that if all people speak with microphone at the same time, there will be a mess of porridge in the meeting.
Because of its working principle, the hub is impossible to filter broadcast storm. The general switch does not have this function. Only now some network switches (such as omnidirectional QS series switches) also have filtering broadcast storm function, and routers themselves have the function of isolating broadcast storm. Broadcast storm can not be completely eliminated, but it can only spread in the same subnet. It's like the sound of the speakers can only spread in the same field, so it's in a large and medium-sized LAN made up of hundreds or even thousands of computers. Generally, the sub network division is like separating a hall into many small halls with walls to achieve the purpose of isolating broadcast storms.
In IP network, broadcast address is represented by IP address "255.255.255.255". This IP address represents all IP addresses in the same subnet.
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There are three communication modes in the current network: unicast, broadcast and multicast. The multicast appears the latest but has the advantages of unicast and broadcast at the same time, and has the most development prospect.
1. unicast:
The one-to-one communication mode between hosts, switches and routers in the network only forward data without copying. Suppose 10 clients need the same data. Then the server must be transmitted one by one, and the same work is repeated 10 times. But because it can respond to every customer in time, all the web browsing today adopts unicast mode, in detail, IP unicast protocol.
Routers and switches in the network choose the transmission path according to their destination address, and transmit IP unicast data to their designated destination.
Advantages of unicast:
1) Server responds to client requests in time
2) Server can send the data that is not available to every customer, and easy realizes personalized service.
Disadvantages of unicast:
1) Server sends data flow for each client, server traffic = number of clients × Client traffic. Server is not burdened in the application of streaming media with large number of clients and large traffic of each client.
2) The existing network bandwidth is pyramid structure, and the inter city backbone bandwidth is only 5% of the total of the actual user bandwidth.
Assuming that all unicast protocols are used, the backbone of the network will be overwhelmed. Nowadays, P2P applications have blocked the backbone. It is impossible to extend the trunk by 20 times.
2. Broadcasting:
One to all communication modes between hosts, the network can copy and forward the signals sent by each host unconditionally. All hosts can receive all information (whether you need it or not). Because they do not need path selection, the network cost can be very low.
Cable TV network is a typical broadcast network, and our TV is actually receiving all the signals of the channel. But just one channel signal is restored to the screen. In the data network, it also agrees with the existence of broadcasting, but it is limited to the LAN of the two-layer switch. It is forbidden to pass the broadcast data through the router to prevent the broadcast data from affecting large-area hosts.
The advantages of Broadcasting:
1) Simple network equipment, simple maintenance and low cost
2) Because the server does not send data to each client separately, the server traffic load is extremely low.
Disadvantages of Broadcasting:
1) Unable to provide personalized services in time for each customer's requirements and time.
2) The network agrees that the bandwidth of data provided by server is limited, and the maximum bandwidth of client is the total bandwidth of service. For example, the line of the client of cable TV supports 100 channels (assuming that the digital compression technology can provide 500 channels in theory), even if the service provider has greater financial resources to configure many other transmission devices and change it into fiber backbone. It cannot be exceeded. That is to say, it is impossible to provide many other diversified and personalized services to many customers.
3) Broadcasting prohibits the consent to be transmitted over the Internet broadband network.
3. multicast:
The one-to-one communication mode between hosts, that is, the host of the same group is added to accept all data in this group. The switches and routers in the network only copy and forward the required data to the demanders. The host can request that a group be added or exited from the router. Routers and switches in the network have the choice to replicate and transmit data, that is, only transfer data within the group to those hosts that add groups. This can not only transmit data to multiple hosts that need (add group) at a time, but also ensure that other communication of other hosts that do not need (no group addition) is not affected.
Advantages of multicast:
1) Clients of the same data stream need to add the same group to share a data stream. The load of server is saved. Have the advantages of broadcasting.
2) Because multicast protocol is based on the receiver's need to copy and forward the data stream. Therefore, the total bandwidth of service end is not limited by the bandwidth of the client access end.
IP protocol has agreed to have more than 260million multicast, so the services it provides can be very rich.
3) This protocol, like unicast, agrees to transmit over Internet broadband.
Disadvantages of multicast:
1) There is no error correction mechanism compared with unicast protocol. It is difficult to make up for the loss of package and wrong package. But it can be compensated by some fault-tolerant mechanism and QoS.
2) The current network supports multicast transmission. But in terms of customer authentication and QoS, we must be in good condition. These shortcomings have mature solutions in theory, and only need to be gradually applied to the existing network.
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How far(long) the transmitter cover?
The transmission range depends on many factors. The true distance is based on the antenna installing height , antenna gain, using environment like building and other obstructions , sensitivity of the receiver, antenna of the receiver . Installing antenna more high and using in the countryside , the distance will much more far.
EXAMPLE 5W FM Transmitter use in the city and hometown:
I have a USA customer use 5W fm transmitter with GP antenna in his hometown ,and he test it with a car, it cover 10km(6.21mile).
I test the 5W fm transmitter with GP antenna in my hometown ,it cover about 2km(1.24mile).
I test the 5W fm transmitter with GP antenna in Guangzhou city ,it cover about only 300meter(984ft).
Below are the approximate range of different power FM Transmitters. ( The range is diameter )
0.1W ~ 5W FM Transmitter ：100M ~1KM
5W ~15W FM Ttransmitter : 1KM ~ 3KM
15W ~ 80W FM Transmitter : 3KM ~10KM
80W ~500W FM Transmitter : 10KM ~30KM
500W ~1000W FM Transmitter : 30KM ~ 50KM
1KW ~ 2KW FM Transmitter : 50KM ~100KM
2KW ~5KW FM Transmitter : 100KM ~150KM
5KW ~10KW FM Transmitter : 150KM ~200KM
How to contact us for the transmitter?
Call me +8618078869184 OR
Email me [email protected]
1.How far you want to cover in diameter ?
2.How tall of you tower ?
3.Where are you from ?
And we will give you more professional advice.
About Us
FMUSER.ORG is a system integration company focusing on RF wireless transmission / studio video audio equipment / streaming and data processing .We are providing everything from advice and consultancy through rack integration to installation, commissioning and training.
We offer FM Transmitter, Analog TV Transmitter, Digital TV transmitter, VHF UHF Transmitter, Antennas, Coaxial Cable Connectors, STL, On Air Processing, Broadcast Products for the Studio, RF Signal Monitoring, RDS Encoders, Audio Processors and Remote Site Control Units, IPTV Products, Video / Audio Encoder / Decoder, designed to meet the needs of both large international broadcast networks and small private stations alike.
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