1. Network Protocol (PMTOCOL)
The
so-called network protocol is a set of rules, standards, or conventions established for the exchange of data in a computer network. A protocol always refers to a layer of protocol,
accurately, it is a collection of communication rules and conventions that are developed for communication between the same layer entities. The network protocol consists of three elements:
① semantics include control information for various frame headers and processing.
② syntax includes data format, encoding, and signal power parity.
③ timing includes speed matching and sequencing.
2. Architecture of the network (Ammeetu accompany)
The architecture of Network is a collection of various levels of computer network and its protocols. The architecture of the network has the following features:
① based on function as the basis for dividing levels O
② the nth-tier entity can only use the services provided by the section (N-1) when implementing its own defined functions.
The
③n layer provides services to the N+1 layer, which includes not only the N-tier functionality, but also the functionality provided by the Downlevel service O
The
④ has an interface only between adjacent layers, and the specific implementation details of the service provided are completely shielded from the upper layer.
3.OSl Reference Model
Open Systems Interconnect (gamma-n system intei℃omlection) basic Reference Model is a standardized open computer developed by the International Organization for Standardization (back)
the network hierarchy model, also known as the ISO's OSI reference show type. "Open" means that any two systems that comply with the model and the relevant standards are able to interconnect o
level Three abstraction of 4.OSl
The OSI includes architecture, service definition, and protocol specification level three abstraction. The OSI gives only a conceptual and functional standard framework, which is the heterogeneous system
The
standard hierarchical structure of the system interconnect. The model itself is not a set of tangible and actionable protocols, not including any specific protocol definitions, nor does it include strong
consistent with the implementation of the system. Network architecture is independent of implementation.
5.OSl seven-layer model
The OSI architecture has a seven-layer model, from bottom to top, namely physical layer (PH), Data link layer (DL), Network layer (N), Transport Layer (T), Session layer (S) ,
the presentation layer (P) and the Application layer (A).
The
① Physical layer provides the mechanical, electrical, functional, and procedural characteristics required to establish, maintain, and dismantle physical links, providing information on transmitting non-
The
"bit stream" of the structure and the physical link fault detection indication.
the ② Data link layer provides the network layer entity with error frame transmission function and flow control.
The
③ Network layer provides end-to-end switched network data transfer capabilities for Transport layer entities, routing and congestion control, etc. o
The
④ Transport layer provides transparent and reliable data transmission service for the session layer entity, which guarantees the end-to-end integrity, and chooses the most suitable service that the network layer can provide .
provides the ability to establish, maintain, and dismantle transport connections.
The
⑤ Session layer provides for the creation of a cooperative presentation layer entity, the ability to maintain and end the dialog connection, and the provision of session management services.
The
⑥ presentation layer provides an application-level process with a set of services that interpret the meaning of the exchanged information, such as code conversion, format conversion, text compression, text encryption, and decryption.
The ⑦ application layer provides services for the OSI application process, such as file transfer, e-mail, and virtual terminals.
The
whole open system environment is connected by physical media as the end open system of the source and the message house and several relay open systems. In general, only
The
host may need to include all seven layers of functionality, while the IMP in the communications subnet typically requires only a minimum of three layers or even a minimum of two levels of functionality.
6. Process of information flow
The
information is not transferred directly from the application layer of a station to the application layer of station B. In fact, each layer transmits data and control information to its next layer, up to the physical layer.
The
physical layer below is the transmission medium, which transmits the actual electrical signals on the physical media.
7.061 Main features of the reference Model
The main features of the OSI model are:
The
①osi model defines an abstract structure that gives only a functional and conceptual standard framework that is independent of the implementation.
② Each layer completes the defined function, the modification of one layer does not affect the other layers.
③ uses this layer protocol to communicate between the same layer entities of different systems, and only the lowest level of direct data transmission occurs.
④ The interface between adjacent layer entities within the same system defines the service primitives and the services provided to the upper layer.
The
⑤osi model itself does not cause network traffic, and it must execute a protocol that implements a layer of functionality before performing tangible network traffic.
⑥ Two different protocols may be subordinate to the same layer of the model to implement different functions. Only the same protocol is executed at the same level to communicate with each other.
Architecture and protocols of computer network
