First off, TCP packets are given sequential numbers.

首先，TCP 数据包被赋予序列号。

TCP uses this information to adjust how aggressively it sends packets – a mechanism for congestion control.

TCP 使用此信息来调整它发送数据包的积极程度——一种拥塞控制机制。

You might wonder why anyone would use UDP when TCP has all these nifty features.

您可能想知道，当 TCP 具有所有这些漂亮的功能时，为什么有人会使用 UDP。

So if an email comes in all scrambled, the TCP implementation in your computer's operating system will piece it all together correctly.

因此，如果一封电子邮件以乱码的形式出现，您计算机操作系统中的 TCP 实现将把它们正确地拼凑在一起。

But, if DNS returns a valid address, which it should for " youtube.com" , then your browser shoots off a request over TCP for the website's data.

但是，如果 DNS 返回一个有效地址，它应该是“youtube.com”，那么您的浏览器会通过 TCP 发出对网站数据的请求。

So, basically, TCP can handle out-of-order packet delivery, dropped packets – including retransmission – and even throttle its transmission rate according to available bandwidth.

因此，基本上，TCP 可以处理无序的数据包传输、丢弃的数据包——包括重传——甚至可以根据可用带宽限制其传输速率。

When it " absolutely, positively needs to get there" , programs use the Transmission Control Protocol, or TCP, which like UDP, rides inside the data payload of IP packets.

当它“绝对、肯定地需要到达那里”时，程序使用传输控制协议或 TCP，它与 UDP 一样，位于 IP 数据包的数据有效负载中。

And today, we mostly covered the Transport layer, protocols like UDP and TCP, which are responsible for point to point data transfer between computers, and also things like error detection and recovery when possible.

今天，我们主要介绍了传输层，UDP 和 TCP 等协议，它们负责计算机之间的点对点数据传输，以及可能时的错误检测和恢复。

We've also grazed the Session Layer – where protocols like TCP and UDP are used to open a connection, pass information back and forth, and then close the connection when finished – what's called a session.

我们还了解了会话层——TCP 和 UDP 等协议用于打开连接、来回传递信息，然后在完成后关闭连接——这就是所谓的会话。

Now, armed with the IP address of the computer you want, your web browser opens a TCP connection to a computer that's running a special piece of software called a web server.

现在，有了您想要的计算机的 IP 地址，您的 Web 浏览器就会打开一个到运行称为 Web 服务器的特殊软件的计算机的 TCP 连接。