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Today, I would like to share with you the relevant knowledge of TCP gigabit network communication. The content is detailed and the logic is clear. I believe most people still know too much about this, so share this article for your reference. I hope you can get something after reading this article. Let's take a look at it.

First of all, through the simple analysis above, we should be clear about one thing: the TCP protocol is very complex, and the handshake alone requires a complex process of "three handshakes and four waves", which is not particularly suitable for the pure logic implementation of FPGA, because the main purpose of Ethernet communication with FPGA is to transmit data with low latency, and once the design scale reaches a certain order of magnitude, the advantages of FPGA communication will no longer exist. In turn, it reflects the disadvantage of low performance-to-price ratio.

Is it impossible to communicate using the TCP protocol? The answer is, of course, no. Because now the major manufacturers will add soft core and hard core in their own chips, and using soft core and hard core to achieve Ethernet communication is also a widely used way, but not all TCP protocols are suitable for soft core or hard core implementation. Next, we will briefly introduce the relatively simple TCP/IP protocol stack lwIP (A Lightweight TCP/IP stack).

First, take a look at LwIP's network model so that you have an overall concept, as shown in the following figure:

Fig. 8 Mur16 LwIP model

The UDP/IP model will be described in more detail later, and there is nothing special about this picture, which mainly has an overall concept of LwIP.

The key point of LwIP implementation is to reduce the occupation of RAM while maintaining the main functions of TCP protocol. It only needs more than ten KB RAM and 40K ROM to run, which makes LwIP protocol stack suitable for use in low-end embedded systems. LwIP has three application programming interfaces (API):

Raw API: the original LwIP API. It uses event callback mechanism for application development. The API provides the best performance and optimized code length, but increases the complexity of application development.

Netconn API: for high-level ordered API, it needs the support of real-time operating system (RTOS) (provides a method of inter-process communication). Netconn API supports multithreading.

BSD Socket API: Berkeley-like socket API (developed on top of Netconn API).

For the above three interfaces, the first one can be called only by bare metal, and the latter two can only be called by the operating system. Therefore, there are two ways to migrate LwIP: first, only the kernel is ported, and the application can only be written based on RAW/Callback API. Second, transplant the kernel and upper API, at this time, application programming can use three kinds of API, namely: RAW/Callback API, Sequential API and Socket API.

These are all the contents of the article "what is TCP Gigabit Network Communications?" Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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