First, let's get rid of a few minor problems
1. Why computer network protocols to be designed as a hierarchical style?
Between two hosts via a communications network to transfer files it is a very complicated matter, if not hierarchical division of labor process, a single module for processing, it will become bloated complex. When slicing, it can bring many benefits:
①, independent of each other between the layers. A processing time does not need to know the layer under a layer of how it works, a complex problem can be decomposed into a number of simple intractable problems tractable.
②, flexible. Modify a single layer, as long as the relationship between the interface layers unchanged, upper and lower layers are not affected.
③, spaced separable structure. The layers are using the most appropriate technology to be realized.
④, easy to maintain and handle.
⑤, promote standardization. Tasks distinct layers.
2 OSI and TCP / IP are different,
OSI is an international standard on the law, but it is not enough ground gas, complicated and impractical, resulting in TCP / IP occupied most of the market, resulting in a TCP / IP has become the de facto international standard.
There OSI seven layer protocol architecture, TCP / IP is a four-layer protocol architecture, an integrated OSI and TCP / IP advantage is produced protocol architecture of five.
First, the application layer
The application layer is the task to complete the application process by interaction between specific network applications.
It defines the rules for inter-process communication and interactive applications for different network applications using different protocols: Domain Name System DNS, Web application HTTP, SMTP email and FTP file transfer, etc.
Second, the transport layer
Task transport layer is to provide communication between the two hosts in charge of the process of data transmission services . With this application process service delivery application layer packets.
There are transport layer TCP (Transmission Control Protocol: to provide connection-oriented, reliable data transmission service) and UDP (User Datagram Protocol: to provide connectionless data transmission services to make maximum effort)
Third, the network layer
Mission network layer is to provide a host of different packet switched network communications services.
The network layer using the IP protocol
Fourth, the data link layer
Task data link layer is the data transmission between two hosts in charge.
V. Physical Layer
Physical layer tasks is to consider how to transmit data bit stream on a computer connected to various transmission media , rather than to specific transmission medium
- Five-layer Internet protocol stack
- Application Layer : The task is accomplished through the interaction between application-specific network application process
- Transport layer : responsible for providing data transmission services in the process of communication between two hosts
- Network Layer : Responsible for providing communication services to a packet switched network of a different host, select the appropriate route
- Link layer : The network layer datagram encapsulated in a frame using a link layer protocol on the link between adjacent nodes transmission frame
- Physical Layer : The bits of a frame from one node to the next node
- Seven-layer OSI reference model
- Presentation Layer : that the application can interpret the meaning of the communication to exchange data, provide data compression, data encryption services
- Session Layer : provides the delimitation and synchronization data exchange, comprising a checkpoint recovery scheme and method
