Mapping follows:
Computer Network Architecture mainly layered architecture, layered architecture comprises two, namely the OSI reference model and TCP / IP reference model .
The OSI reference model communication function of the entire computer network is divided into seven, 1 to 3 layers for performing data exchange and data transmission , the network is called low-level, 5 to 7 layers for performing an information processing function , called network level, wherein The fourth layer for connecting lower and upper.
Physical Layer : The main function is to achieve transmission structure without bitstream over a transmission medium.
The data link layer : The main function is implemented between neighboring nodes reliable and efficient data transmission.
Network layer : The main function is the data forwarding and routing.
Transport layer : The main function of multiplexing / demultiplexing, reliable end to end data transfer, connection control, flow control and congestion control mechanisms.
Session Layer : The main function is accomplished by establishing a session between the two computers, managing, and terminating communication.
Presentation Layer : The main function is to deal with the syntax between application entities to exchange data with the aim to resolve differences and file encryption and decryption of data representation formats and so on.
Application Layer : The main function is to provide users using a network application "Interface."
The figure is the data package transmission process described in the OSI reference model:
In the data transmission process, the transmission and reception of each content as shown below:
TCP / IP reference model compared to the above seven, less three, only the application layer, transport layer, network interconnect layer, network interface layer.
The reason why there appeared TCP / IP reference model, because of the OSI reference model layered in more detail, but not suitable for practical application of the network, resulting in too small a hierarchical resource waste and low utilization, and therefore more practical network applications use the TCP / IP reference model.
So the focus of this book five reference models , the next to find out more.
In the foregoing description, a brief overview of what we OSI and TCP / IP reference model, then five, a combination of both, eventually consisting of a physical layer, a data link layer, network layer, transport layer and application layer , most commonly in a computer network, closest to the actual network reference model.
Application Layer : support a variety of network applications
eg：FTP，SMTP，HTTP
: Transport Layer data transmission process - the process
eg：TCP，UDP
Network layer routing the data packet and forwarding the source host to the destination host:
eg: IP protocol and routing protocol
Link layer : data transmission in an adjacent network elements (hosts, switches, routers, etc.)
eg: Ethernet, 802.11, PPP
Physical layer : bit transfer
