INSIGHT-IT

The protocols that make up the TCP/IP protocol suite can also be described in terms of the OSI reference model. In the OSI model, the network access layer and the application layer of the TCP/IP model are further divided to describe discrete functions that must occur at these layers.

还可以根据 OSI 参考模型描述构成 TCP/IP 协议簇的协议。在 OSI 模型中，TCP/IP 模型的网络接入层和应用层被进一步划分，用于描述这些协议层需要实现的不同功能。

At  the network access layer, the TCP/IP protocol suite does not specify which protocols to use when transmitting over a physical medium; it only describes the handoff from the internet layer to the physical network protocols. OSI Layers 1 and 2 discuss the necessary procedures to access the media and the physical means to send data over a network.

TCP/IP 协议簇在网络接入层并没有指定通过物理介质传输时使用的协议，而只是描述了从互联网层到物理网络协议的传递。而 OSI 模型第 1 层和第 2 层则论述了接入介质所需的步骤以及通过网络发送数据的物理手段。

OSI Layer 3, the network layer, maps directly to the TCP/IP Internet layer. This layer is used to describe protocols that address and route messages through an internetwork.

OSI 模型第 3 层是网络层，与 TCP/IP 的互联网层形成直接映射。该层用于描述通过网际网络编址并路由消息的协议。

OSI Layer 4, the transport layer, maps directly to the TCP/IP Transport layer. This layer describes general services and functions that provide ordered and reliable delivery of data between source and destination hosts.

OSI 模型第 4 层是传输层，与 TCP/IP 的传输层形成直接映射。该层描述了可以在源主机和目的主机之间提供有序可靠的数据传输的常用服务和功能。

The TCP/IP application layer includes a number of protocols that provide specific functionality to a variety of end user applications. The OSI model Layers 5, 6, and 7 are used as references for application software developers and vendors to produce products that operate on networks.

TCP/IP 应用层包括许多协议，为各种最终用户应用程序提供特定功能。OSI 模型第 5 层、第 6 层和第 7 层供应用程序软件开发人员和厂商参考，用于生产需要在网络上运行的产品。

Both the TCP/IP and OSI models are commonly used when referring to protocols at various layers. Because the OSI model separates the data link layer from the physical layer, it is commonly used when referring to these lower layers.

当涉及各层的协议时，TCP/IP 和 OSI 模型都很常用。由于 OSI 模型将数据链路层与物理层区分开来，当涉及这些较低层时通常使用这种模型。