Switch forwarding mechanism: store and forward and cut-through forwarding

introduction

In network communications, switches play a vital role. It is responsible for forwarding data frames within the Local Area Network (LAN). There are two main methods of switch forwarding: Store-and-Forward and Cut-Through. Both methods have their own advantages and disadvantages and are suitable for different scenarios. This article will deeply explore the working principles, advantages and disadvantages of these two forwarding mechanisms, and analyze them based on the code and kernel source code.

Store-and-Forward

working principle

The store-and-forward method stores the entire data frame in the switch's buffer before forwarding the data frame. Then check the FCS (Frame Check Sequence) bit at the end of the data frame to ensure that there are no errors in the data frame.

code example

// C++ 伪代码示例
void storeAndForward(Frame frame) {
  Buffer buffer;
  buffer.store(frame);
  if (buffer.checkFCS()) {
    buffer.forward(frame);
  }
}

Advantages and Disadvantages

advantage	shortcoming
Can effectively filter out error frames	higher latency
The network is more stable	Take up more cache resources

deep insights

The store-and-forward method is more like a "prudent" processing method. It conducts a comprehensive check before forwarding to ensure the stability of the network. This approach is much like when people make decisions, they consider all factors comprehensively before taking action.

Cut-Through

working principle

In the cut-through forwarding mode, after receiving the destination address of the data frame, it will start forwarding immediately without waiting for the entire data frame to be received.

code example

// C++ 伪代码示例
void cutThrough(Frame frame) {
  Address dest = frame.getDestination();
  forward(frame, dest);
}

Advantages and Disadvantages

advantage	shortcoming
Lower latency	Possible forwarding of incorrect frames
Less resource usage	Poor network stability

deep insights

The cut-through forwarding method is more like a "bold" processing method that pursues speed and efficiency, but it may also bring risks. This approach is very similar to how people may make quick decisions when faced with an emergency, but may also overlook some important details.

Summarize

Store-and-forward and cut-through forwarding each have their own advantages and disadvantages. Which method to choose depends on the specific application scenarios and requirements. Store-and-forward is more suitable for networks that require high stability, while cut-through and forward is more suitable for applications that have strict requirements on latency.

As Bjarne Stroustrup said in "The C++ Programming Language": "Choose the tool that best fits the problem, rather than trying to fit the tool to the problem."

references

Bjarne Stroustrup. “The C++ Programming Language”
IEEE 802.1D - Standard for Local and Metropolitan Area Networks

hope

Conclusion

In our programming learning journey, understanding is an important step for us to move to a higher level. However, mastering new skills and ideas always requires time and persistence. From a psychological point of view, learning is often accompanied by constant trial and error and adjustment, which is like our brain gradually optimizing its "algorithm" for solving problems.

This is why when we encounter mistakes, we should view them as opportunities to learn and improve, not just as annoyances. By understanding and solving these problems, we can not only fix the current code, but also improve our programming skills and prevent making the same mistakes in future projects.

I encourage everyone to actively participate and continuously improve their programming skills. Whether you are a beginner or an experienced developer, I hope my blog will be helpful on your learning journey. If you find this article useful, you may wish to click to bookmark it, or leave your comments to share your insights and experiences. You are also welcome to make suggestions and questions about the content of my blog. Every like, comment, share and attention is the greatest support for me and the motivation for me to continue sharing and creating.

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