The important feature of the 21st century: digital, networked and informationization, which is a network-based information era. World Economy ------ Industry-based Economy ------ → Knowledge-based Economy computer network development process
Packet Switching CAUSE: Traditional Circuit Switching does not adapt to network digital transmission. New networks To: 1 Digital transfer between your computer 2 can connect to different types of computers (isomernes?) 3 All network nodes are equally important. (Improve network survival) 4 must have redundant routing. (Redundant Routing) 5 as simple as possible, transmit data very reliably. (TOO SIMPLE AND TO RELIABLE)
Circuit exchange must be a connection. Circuit Switching Must Be Connection-Oriented) The two users of the call always occupy the fixed transmission bandwidth of the end. Therefore, the transmission efficiency of the line is very low. While The Connection and Talk, The ENGROSS The Bandwidth of Transfers All The Time.so The Efficiency of Circuitry's Transfers Is Too Bad!
Group exchange adopts storage forwarding (Storage Transmit?) Technology. Message - SEGMENT - Plus the header - Packet (Packet) The Character of Packet Switching is label-based, and it is incnnectionless. Node Switch Exchange to forward grouping. Node Switch Get Packet Switching, And Transmit Packet. Host (HOST) user performs information processing. Host deal with the informations for user.Two problems which be brought by packet switching:! Delay and overhead.Communication subnet and resource subnet which, must be distinguish clearly Four sorts of network: ①circuit switching ②message switching③packet switching④mixed switchingOf course, you can carve up the network by the bound of action.for example: ①WAN: Wide Area Network②LAN: Local Area Network③MAN: Metropolitan Area Network④AN: Access NetworkThe two primary guide-line of the network's capability: bandwidth and delay (It is hard to learn well, I will ! read the book and write detailedly latter) Four concept: entity: all hardware and software which can send and receive messages.protocol: the aggregate of the rule which control two equity entity to keep connectionService: SAP: Service Access Point .We must distinguish The Differ Between The Protocol and Service Clearly! How Tire! I have do my best effort delivery ~ _ ~
