----------- osi network infrastructure with a number of agreements

1, understand the OSI ISO IOS

ISO (full name: International Organization for Standardization) International Organization for Standardization,

　　Founded in February 23, 1947, to develop international standards for industry and commerce around the world to establish international standards bodies, I is headquartered in Geneva, Switzerland　

　　In the development of computer network standards, it plays a major role in two major international organizations are: the International Telecommunication Union Telecommunication Standardization Sector, the International Standards Organization (ISO) 　

OSI (full name: Open System Interconnection Reference Model) Open Systems Interconnection Reference Model

　　It is a conceptual model proposed by the International Organization for Standardization (ISO), trying to make a variety of interconnected computer networks as a standard framework in the world.

　　In 1984, ISO published the prestigious ISO / IEC 7498 standard, which defines a 7-layer framework for network interconnection , that is, the Open Systems Interconnection Reference Model.

IOS (full: Internetwork Operating System) operating system Cisco equipment

　　Internet Operating System (Internetwork Operating System, referred to as IOS) is Cisco's development of its network equipment operation and maintenance system, users run the command man-machine interface for network devices feature set

　　Provides functionality roughly the following: data transmission network security management function is provided between the device and the port of preference settings, network protocols and network operation functions of the device.

　　Note: This is not to be confused with ios operating system,  iOS (formerly known as iPhone OS) is Apple's mobile devices developed its proprietary mobile operating system, where the main network to accept some terms

 

Detailed: the OSI reference model: 7 layer reference model Theory

Layer 7 Application Layer
　　The application layer (Application Layer) provides for the application software set of interfaces to set up communication between the application and another.

　　For example: HTTP, HTTPS, FTP, TELNET, SSH, SMTP, POP3.HTML the like.

Layer 6 presentation layer

　　Expression layer (Presentation Layer) and converts the data format suitable for transmission compatible with the system format recipient is capable.

Session Layer Layer 5
　　Session Layer (Session Layer) responsible for setting up and maintaining a communication connection between two computers in the computer network data transmission.

Layer 4 transport layer,
　　the transport layer (Transport Layer) The transmission header (TH) is added to the data to form packets. Transmission header includes a protocol used to send information.

　　For example: Transmission Control Protocol (TCP) and the like.

Layer 3 Network Layer
　　The network layer (Network Layer) determining a route selection and forwarding data, the network header (NH) was added to a packet, to form a packet. Network header includes a data network.

　　For example: Internet Protocol (IP) and so on.

Layer 2 Data Link Layer
　　The data link layer (Data Link Layer) is responsible for network addressing, error detection and error correction. When the header and tail to be added to the data packet, it will form a frame.

　　　　Data list head (DLH) a method comprising physical address and the error detection and error correction.

　　　　Data end of the list (the DLT) is a string of data indicating the end of a string of packets.

　　Such as Ethernet, wireless LAN (Wi-Fi) and General Packet Radio Service (GPRS) and so on.
　　It is divided into two sublayers: the Logical Link Control (logical link control, LLC) sublayer and the media access control (Medium access control, MAC) sublayer.

Layer 1 Physical Layer
　　The physical layer (Physical Layer) transmitting a data frame (data frame) in the local LAN, which is responsible for managing the intercommunication between the communication device and the computer network media.

　　　　It includes pins, voltages, cable specifications, hubs, repeaters, network card, the host interface cards.

Between the level of equipment used

　　Network layer device: router

　　Data Link Layer: switch bridge (bridge switch is more interfaces)

　　Physical Layer: Hub repeater (hub is a multi-interface repeater)

 

2、 TCP/IP

　    TCP (Transmission Control Protocol) and IP (Internet Protocol)　

　　TCP / IP provides a mechanism for point to point links, and how the data should be packaged, addressed, transmission, routing, and how to receive destination, are to be standardized.

　　It abstracted into four communication process software abstraction layer, take the form of the protocol stack, respectively, to achieve a different communication protocols.

　　Various protocols under the protocol suite, according to their different functions are attributed to being among the four hierarchy, often regarded as a simplified seven-layer OSI model.

Relationship with the seven-layer OSI model:

Clarify IPS, TCP / IP, DoD

 　　Internet Protocol Suite (Internet Protocol Suite, abbreviated IPS) is a network communication model, and a whole family of network transport protocols, Internet-based communications architecture of. It is often known as TCP / IP protocol suite, referred to TCP / IP, the protocol family two core protocols: TCP (Transmission Control Protocol) and IP (Internet Protocol), for the first family of standards adopted.

　　Due to the hierarchical structure commonly used in network communication protocol, when multiple levels of agreement to work together, similar to computer science stack, it is also known TCP / IP protocol stack (English: TCP / IP Protocol Stack).

　　These agreements first originated in the United States Department of Defense (DoD abbreviated) of the ARPA network project, it is also called the DoD model (DoD Model) protocol suite that is responsible for maintenance by the Internet Engineering Task Force.

3, commonly used protocol port

Transport Layer:

　　TCP Transmission Control Protocol connection-oriented reliable

　　　　To establish a connection: three-way handshake  Disconnect: Four waving

　　UDP User Datagram Protocol for non-connection-oriented reliable