Computer Network (Learning 1)

Computer Network (Learning 1) I. Several defined networks of computer networks, the Internet composed of computer networks, and the Internet formed by many networks connected together; the world's largest Internet 2, computer network structure connectivity, sharing edge part: Computer, server, common structures such as C/S and P2P server programs run on the server side, the client is the core part that runs the client program. The routing selection protocol, Link, packet forwarding, and so on. 1. The three phases of the Internet are the first phase, and the APRNET phase, the trial run of the TCP/IP protocol on APRNET in 1983 marks the birth of the second stage of the network. The three-tier structure consists of the backbone network, Campus Network (Enterprise Network), the third stage of the user, and the ISP stage, it can be interconnected or several stages can be generated based on the NAP Internet protocol. The draft Internet ---> recommended standard ---> draft standard ---> Internet standard 2, telephone Network ---> circuit switching must be a connection-oriented service. Step 3: establish connections, call, and release connections. Storage forwarding ---> connection-oriented With the implementation of a router, a complete packet is first divided into several groups and then forwarded. The storage of the route uses registers rather than disks, so as to improve the transmission rate. (1) circuit Switching -----> (2) packet transmission -----> (3) the difference between storage Forwarding (1) and (2) is that the storage Forwarding is connected to the surface, (2) the difference with (3) is group 3. The network structure is Layer 7 (top ---> bottom): application layer, presentation layer, Session Layer, transmission layer, network layer, link layer, layer-4 Structure of the physical layer (upper ---> lower): application layer, transmission layer, Internet layer, network interface layer, and layer-5 structure (upper ---> lower): application layer, transmission layer, the communication between the Internet layer, the link layer, and the physical layer and the layer is equivalent, and the communication object is a process. Previous and previous transmission was controlled by protocol. A protocol is a rule set that controls communication between two objects. Physical Layer; only processing, for example, what voltage is used to mark the link layer (including the hub and the original repeater) with 0 or 1, including the switch (hardware device), bridge (software device) network layer, and router Application Layer: gateway