instant messaging

来源：哇谷im-原创 2020-07-21 20:16:35

nstant messaging (IM) and real-time communication are network communication systems, whose essence is forward information. The biggest difference is the requirement of time information transmission. The differences between them can be found in the following aspects:

Common instant messaging solutions include text chat, voice messaging, file transfer, audio and video playback. Generally speaking, it's texting. scene

Real time communication, including voice, video conference, Internet phone, etc. In general, it is a call. Instant messaging architecture.

2、 Product appeal point

Instant messaging: the main requirements are reliable quality and delivery evaluation rate. If you send a text message and the result is lost, the other party has not received it! You don't believe in texting. Instant messaging.

Real time communication: the main requirement of low delay and connection rate. Is wechat an instant messaging tool.

Low latency: you make a call, every word, and the other is a response of only a few seconds, and the phone also tells you not to turn right.

Connection rate: when you call you and hear your profile open, and actually don't respond to the other person's phone, it's actually walking up. It's not sent with the mail, and the adverse effects are the same.

Three technical aspects

IM technology: confirmation message and sending, [access end message, service logic processing of end message, message storage and forwarding of the cache server, end user state management service, heartbeat mechanism, message sender], message receiving and confirmation. Is wechat instant messaging.

Technical aspects: acquisition, preprocessing, coding, [access server, forwarding access server], decoding, rendering and playback.

Some of these technical aspects overlap: forwarding information.

4、 Transmission protocol

Instant messaging: what is rongyun instant messaging

Public Internet, the most commonly used communication protocol is TCP, UDP. Instant messaging intranet.

TCP: transmission control protocol, transmission control protocol is a connection based protocol, that is, before receiving data, you must create a reliable connection with the other party. It has uncontrollable delay characteristics.

UDP: user datagram protocol, user datagram protocol, is the protocol corresponding to TCP. This is a non connection oriented protocol, it does not establish a connection with the other party, but directly sends the package. Packet loss, jitter and delay characteristics.

In order to ensure the reliability of the connection, the most commonly used protocol in e-mail system is TCP or TCP connection protocol. The characteristic of this protocol is to pursue the reliability of the connection, but it does not cause controllable delay of more than two seconds. The delayed response is normal, even dozens of minutes. The real-time communication standard with operators is 400ms, and a new transportation solution is created based on the need for another way of real-time communication through the Internet. This, in turn, is linked to the programme. SMS, delivery delay of a few seconds, users almost no impact.

Real time communication, using UDP as the underlying transport protocol. In the design of real-time communication service with low delay, UDP performance is much better than TCP. This is because of real-time communication, low latency is more important than reliability. Phone calls, a few seconds of delay can't be tolerated.

Encapsulating the retransmission of TCP protocol message, it is almost impossible to optimize the retransmission mechanism to achieve low waiting time in the application of TCP protocol. In particular, when a mobile network, more than 30% of the packet loss, TCP can be more than 50% of the packet loss, or even easily break, delay to dozens of minutes. In addition, UDP may also send data at 30% loss of the connecting rod, and TCP cannot perform real-time communication. UDP based protocol

With the development of various packet loss compensation algorithms, on the one hand, continuity and data recovery are guaranteed as much as possible. On the other hand, when some packets cannot be recovered, the corresponding audio and video packets will be discarded, and the subsequent real-time communication services will not be affected. What does instant messaging mean.

Fifth, the costs involved

Part of the cost of: server access, storage and forwarding. PC instant messaging message.

The difference between the two link costs is: from the perspective of server, the world's first instant messaging.

Access, using TCP to ensure the reliability of instant messaging protocol, can establish multiple connections, UDP compared to this is an expensive transmission is connectionless transmission. Real time communication can be based on UDP protocol to establish a flexible and fast access mechanism with the server.

Storage, real-time forwarding server of real-time communication, is not the data stored in the server in general. The data that the instant messaging system will cache into the memory, including rich media data, takes up a lot of storage space, resulting in more and more storage costs. From the perspective of cost

, information and data transmission, instant messaging method based on TCP, more emphasis on reliability, the same amount will be the preferred multi line transmission room, the cost is relatively high; real time and instant messaging technology based on UDP.

In communication system, the best path for data transmission is preferred, and the transmission path can be dynamically adjusted to make use of available bandwidth effectively, improve transmission efficiency and reduce cost.

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