The blog post for the structural basis of memory network.
Network architecture
set is a network architecture (Architecture) and computer network protocol layers. Stated another way, the architecture of the computer network is a computer network and the precise definition of the member function to be completed.
Architecture five agreements
The concept of the seven-layer OSI protocol architecture clear, complete theory, but complex and impractical.
TCP / IP architecture is a four-layer architecture, comprising an application layer, transport layer, network interface layer and the Internet layer (Internet layer with the name of this layer is emphasized in order to solve interconnection of different networks).
Five compromise agreement for the integrated OSI and TCP / IP advantages.
(1) the application layer (application layer)
task is to complete the application layer application-specific network through the interaction between the application process. The application layer protocol is defined by the rules of inter-process communication and application interaction. Here is the process in the host program is running. For different network applications require different application layer protocols.
The application layer protocol in the Internet a lot, such as the Domain Name System DNS, HTTP protocol support Web applications, e-mail support SMTP protocols.
Interactive application layer data unit referred to as packet (message).
(2) transport layer (transport layer) / Transport Layer
task transport layer is responsible for providing universal data transmission service to communication between two hosts in the process. With this application process service delivery application layer packets.
Since a host can run multiple processes simultaneously, the transport layer multiplexing and demultiplexing functions. Multiplexing a plurality of application layer processes that can simultaneously use the service transport layer below; multiplexing and demultiplexing the contrary, the process corresponding to the transport layer, respectively, to deliver the information received in the application layer above.
The transport layer uses two main protocols:
transmission control protocol TCP (Transmission Control Protoclol): to provide reliable connection-oriented data transmission services, the data transmission unit segment (segment).
User Datagram Protocol UDP (User Datagram Protocol): provides connectionless data transmission services to make the greatest effort (does not guarantee the reliability of data transmission), the unit of data transfer User Datagram.
(3) network layer (network layer)
mission network layer is responsible for providing communications services to different hosts a packet-switched network. When transmitting data, segment the transport layer, network layer or user-generated data packets encapsulated into packets or a packet is transmitted. In the TCP / IP system, since the network layer using the IP protocol, thus packet also called IP packets or simply packets.
(4) data link layer (data link layer)
referred to as the link layer. Between two adjacent nodes to transmit data, the data link layer, network layer IP datagram delivery down drive assembly frame (Framing), a transmission frame (Frame) on the link between two adjacent nodes. Each frame comprising data and control information necessary (e.g., synchronization information, address information, interleave control, etc.).
When receiving data, the control information enables the receiving terminal to know which bit of a frame to which the bits from the beginning and the end. The data link layer so that after receiving a frame can be extracted from the data portion, to the upper network layer. Control information further enable the receiving end can detect the presence or absence of frame errors received. If there is an error, the data link layer is simply discards the frame, so as to avoid waste of resources continues to transmit. If the need to correct errors occurring during data transmission, it is necessary to use a reliable transport protocol to correct the error occurs, this method makes the data link protocol layer complex.
(5) physical layer (physical layer)
units on the physical layer of the transmitted data is a bit. The physical layer to consider how much the voltage representative of "1" or "0", and how to identify the recipient of bits transmitted by the sender. The physical layer also determines the cable plug connector pin may be the number of the pin connector and how to explain the task does not mean a physical layer represented by the bits.
Note that, some of the physical transmission medium used by the information, such as twisted pair, coaxial cable, fiber optic cable, wireless channel, etc. are not in the physical layer of the protocol, but below the physical layer protocol, the physical layer and therefore it was below 0 physical media as the first layer.
Data transfer process
The figure illustrates the application process of the data transfer process between the respective layers undergo changes (environmental simple two hosts are connected by a router).
TCP / IP Architecture
TCP / IP architecture may now use the Internet has evolved as shown above, i.e., some applications can directly use the IP layer, or even directly lowermost network interface layer.
As shown above, a specific hierarchical protocol drawn to represent the TCP / IP protocol suite, which is characterized by two large and small middle vertical: the application layer and network interface layer have a variety of protocols, the IP layer and the intermediate small the upper layer protocols to converge in a downward IP protocol.
This kind of TCP / IP protocol suite show:
TCP / IP protocol can service a wide range of applications, and TCP / IP protocol also allows the IP protocol to run on a variety of network including the Internet, it can also be seen the central role of IP protocol in the Internet species.
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