Skype, for example, which uses UDP for video chat, can handle corrupt or missing packets.

例如，使用 UDP 进行视频聊天的 Skype 可以处理损坏或丢失的数据包。

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。

Inside of the UDP header is some useful, extra information.

UDP 标头内部是一些有用的额外信息。

UDP headers also include something called a checksum, which allows the data to be verified for correctness.

UDP 标头还包括一种称为校验和的东西，它允许验证数据的正确性。

In UDP, the checksum value is stored in 16 bits.

在 UDP 中，校验和值以 16 位存储。

Both of these properties sound pretty catastrophic, but some applications are ok with this, because UDP is also really simple and fast.

这两个属性听起来都非常糟糕，但一些应用程序对此没有问题，因为 UDP 也非常简单和快速。

When a packet arrives to the computer, the Operating System will look inside the UDP header and read the port number.

当数据包到达计算机时，操作系统将查看 UDP 标头内部并读取端口号。

One of the simplest and most common is the User Datagram Protocol, or UDP. UDP has its own header, which sits inside the data payload.

最简单和最常见的一种是用户数据报协议或 UDP。 UDP 有自己的标头，位于数据有效载荷内。

So to review, IP gets the packet to the right computer, but UDP gets the packet to the right program running on that computer.

因此回顾一下，IP 将数据包发送到正确的计算机，而 UDP 将数据包发送到该计算机上运行的正确程序。

That's why sometimes if you're on a bad internet connection, Skype gets all glitchy – only some of the UDP packets are making it to your computer.

这就是为什么有时如果您的互联网连接状况不佳，Skype 会出现故障 – 只有部分 UDP 数据包会发送到您的计算机。

Unfortunately, UDP doesn't offer any mechanisms to fix the data, or request a new copy – receiving programs are alerted to the corruption, but typically just discard the packet.

不幸的是，UDP 不提供任何修复数据或请求新副本的机制——接收程序会收到损坏警报，但通常只是丢弃数据包。

Also, UDP provides no mechanisms to know if packets are getting through – a sending computer shoots the UDP packet off, but has no confirmation it ever gets to its destination successfully.

此外，UDP 不提供任何机制来了解数据包是否通过——发送计算机将 UDP 数据包发射出去，但无法确认它是否成功到达目的地。

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。