计算机网络与互联网(英语).ppt

Layering Principle Data Communications On the sender, each layer: Accepts an outgoing message from the layer above Adds a header and other processing Passes resulting message to next lower layer On the receiver, each layer: Receives an incoming message from the layer below Removes the header for that layer and performs other processing Passes the resulting message to the next higher layer Data Communications The software at each layer communicates with the corresponding layer through information stored in headers Each layer adds its header to the front of the message from the next higher layer Headers are nested(嵌套) at the front of the message as the message traverses the network Internet Protocol Architecture Originally it was based on the ISO reference model Currently, Internet is mostly based on the TCP/IP protocol suite (designed in late 70’s) TCP/IP became popular as it was bundled with the UNIX/C environment ISO is still influential in designing networks Other architectures: ATM. Frame Relay ISO 7-layer and TCP/IP 5-layer Reading Materials Textbook Chapters 1, 2 Chapter 16 Summary Studying networks is important because The world is interconnected Applications now operate in a distributed environment This course Covers networking and internetworking Explains the mystery Will be hard work Computer networks Deliver data from source to destination Automatically find optimal paths Handle problems that occur We will learn how What a Network Does Provides communication that is Reliable Fair Efficient From one application to another Automatically detects and corrects Data corruption Data loss Duplication Out-of-order delivery Automatically finds optimal path from source to destination What a Network Includes Transmission hardware Special-purpose hardware devices Interconnect transmission media Control transmission Run protocol software Protocol software Encodes and formats data Detects and corrects problems Network Programming Network allows arbitrary a