计算机英语第五章翻译.docx

Ch5 The Network LayerThe network layer is concerned with getting packets from the source all the way to the destination. Getting to the destination may require making many hops at intermediate routers along the way. 网络层关心的是把包从源到目的地的所有方式。到达目的地可能需要在中间路由器沿途许多跳。5.1 Network Layer Design Issues In the following sections we will provide an introduction to some of the issues that the designers of the network layer must grapple with. These issues include the service provided to the transport layer and the internal design of the subnet. 在下面的章节中我们将提供一些，网络层的设计必须解决的问题的介绍。这些问题包括服务提供给传输层和子网的内部设计。5.1.1 Store-and-Forward Packet Switching A host with a packet to send transmits it to the neares t router, either on its own LAN or over a point-to-point link to the carrier. The packet is stored there until it has fully arrived so the checksum can be verified. Then it is forwarded to the next router along the path until it reaches the destination host, where it is delivered. This mechanism is store-and-forward packet switching, as we have seen in previous chapters.一个数据包的主机发送发送到相图T路由器，在自己的局域网或一个点至点链接到载体。包是直到它完全是校验和可以验证有存储。然后转发到下一个路由器沿路径，直到它到达目的主机，它是交付。这种机制是存储转发分组交换，我们在前几章已经看到5.1.2 Services Provided to the Transport Layer The network layer provides services to the transport layer at the network layer/transport layer interface. An important question is what kind of services the network layer provides to the transport layer. The network layer services have been designed with the following goals in mind. 网路层提供服务给传输层在网络层和传输层接口。一个重要的问题是，什么样的服务提供的网络层到传输层。网络层的服务在设计时考虑以下目标。1. The services should be independent of the router technology. 1。服务应该是独立的路由器技术。2. The transport layer should be shielded from the number, type, and topology of the routers present.2。传输层应该屏蔽的数量，类型，和路由器的当前拓扑。3. The network addresses made available to the transport layer should use a uniform numbering plan, even across LANs and WANs.3.网络地址提供给传输层应使用统一的编号方案，即使在局域网和广域网。One camp (represented by the Internet community) argues that the r