网络:传输层和网络层之间的区别 [英] Networking: Difference between Transport layer and Networking Layer

问题描述

在互联网模型中有四层:链接 -> 网络 -> 传输 -> 应用.

In Internet Model there are four layers: Link -> Networking -> Transport -> Application.

我真的不知道网络层和传输层之间的区别.当我阅读时:

I don't really know the difference between networking layer and transport layer. As I read:

Transport layer: include congestion control, flow control, reliability ...
Networking layer: route data from A to B

因此，基于上述属性，我发现这两层之间存在一些重叠.

So, base on above properties, I see that there are some overlaps between those two layers.

1) 网络层决定将数据从 A 移动到 B.但是，当数据知道如何从 A 移动到 B 时，术语流量控制"拥塞控制"是什么意思......?当数据包(和字节流在数据包中)已经知道跨网络移动时，它如何以及控制什么.

1) Networking layer decides to move data from A to B. But, when data has known how to moved from A to B, what does it means for term "flow control" "congestion control" ... ? How and What does it control when the packet (and byte stream is in packet) has already known to moved across network.

2) 或其他示例，传输层中的 TCP 协议是流的有序交付.但是，TCP 不决定如何移动数据，而是网络层.那么，TCP 能做什么呢?

2) Or other example, TCP protocol in Transport layer is ORDERED delivery of a stream. But, TCP doesn't decide how to move data, but Networking layer. So, how can TCP can do ?

所以，我无法理解这两个词.请教我.

So, I cannot get in those two terms. Please teach me.

谢谢:)

推荐答案

这些是抽象级别.

传输层是决定使用 TCP/UDP 的地方.在这一层常用的协议中，TCP 是可靠的，UDP 不是.根据所做的选择，相应的标头会附加到您的数据包中.例如，TCP 只知道 SYN-ACK、三向握手机制，但不知道远程端点的地址，也不知道通过网络获取数据包的机制.

Transport Layer is where the decision to use TCP/UDP is made. Among commonly used protocols in this layer, TCP is reliable, UDP isn't. Depending upon the choice made, the respective headers are attached to your packet. TCP for example just knows about SYN-ACK, Three-way handshake mechanisms, but does not know the address of the remote-endpoint, or the mechanism of getting the packet across the network.

拥塞控制、流量控制通过调节发送的数据包数量来帮助确保网络不会被数据包淹没.

Congestion control, Flow control help ensure that the network isn't flooded with packets, by regulating the number of packets being sent.

现在，在附加 TCP/UDP 标头后，它移至网络层.直到这一步，远程端点的 IP 地址根本不是数据包的一部分.正是在这一步，Source &目标 IP 地址被添加到数据包中.这一层实际上知道远程端点.

Now, after TCP/UDP header being appended, it moves on to the Network Layer. Till this step, the remote end-point's IP address wasn't a part of the packet at all. It is at this step that the Source & Destination IP addresses are added to the packet. This layer actually knows the remote-endpoint.

      Sender                          Receiver


    -----------                      ------------
   |           |   virtual link     |            |
   | Transport | -----------------> | Transport  |
   |           |                    |            |
    -----------                      ------------
         |                                |
         |                                |
    -----------                       -----------
   |           |    virtual link     |           |
   |  Network  | ------------------> |  Network  |
   |           |                     |           |
    -----------                       -----------
         |                                |
         |                                |
    -----------                       -----------
   |           |                     |           |
   | Physical  |                     | Physical  |
   |           |                     |           |
    -----------                       -----------
         ↓                                 ↑
         |____________real link____________|

发送方的传输层数据，是接收方传输层接收到的确切数据.

The sender's Transport Layer data, is the exact data received by the receiver's transport layer.

当数据包沿着发送方传输时，每一层都添加了自己的标头信息，但所有这些都被接收方的相应层删除.

As the packet travels down the sender, each layer is adding its own header information, but all of that is removed by the corresponding layer on the receiver.

优点是建立了虚拟链接，如上图所示，而真实链接仅在物理层.

The advantage is that a virtual link is established, like the one shown above, whereas the real link is only in the physical layer.

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