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The Composition of the Internet

Edge part: the host (end system) on the Internet. The host is the core part of information processing for users: the network and the router connected to the network. The router is the communication mode between the edge part of the end system for forwarding packets: 1. Client-server 2. Communication mode for the core part of p2p connection: 1. Circuit switching: telephone and switch (source point to destination) 2. Packet switching: use the store-and-forward technology to group packets and add a header containing control information to each packet to form a packet. 3. Message exchange: telegraph communication (sending a message to an adjacent point)Copy the code

switches

A switch, sometimes called a multi-port bridge, is a network device that encapsulates and forwards data frames based on MAC address recognition at the link layer. A switch can "learn" MAC addresses and store them in an internal address table, allowing frames to travel directly from the source address to the destination address by establishing a temporary switching path between the originator and the intended recipient. Because data can be transmitted between multiple port pairs at the same time, network bandwidth is improvedCopy the code

The network card

Network card is working in the link layer network components, is connected to the computer and transmission medium in the LAN interface Can not only realize the physical connection between a local area network transmission medium and electrical matching, still involve the sending and receiving of frame, frame encapsulation and unpacking, media access control, data coding and decoding, and the function of the data cache, etc. In general, the electrical signals in the twisted pair wire are converted into binary data signalsCopy the code

The performance of computer networks

> Rate: > Bandwidth: (The maximum data rate that a channel can pass in a unit time) > Throughput: > Delay: (transmission delay, transmission delay, processing delay, queuing delay) > latency bandwidth product (transmission delay x bandwidth) > Round-trip time RTT > UsageCopy the code

Network protocol

Syntax, semantics, synchronizationCopy the code

Computer network architecture

> Application layer: communication activities that provide services for users > Transport layer: data transmission between two computers connected in the network > Network layer: processing flow data packets on the network > Link layer: connecting the hardware part of the network (operating system, network card, optical fiber) > changes of data transmission in the physical layer network: HTTP packets -> User datagrams (packet segments)-> Packets -> FramesCopy the code