CCNA study notes - 7-layer model structure

OSI Reference Model: The International Organization for Standardization (ISO) established a subcommittee in 1979 to specialize in an Open Systems Interconnection (OSI). The term "open" means that a system can be connected to any other system in the world that also follows the OSI standard, as long as the OSI standard is followed. This subcommittee proposes an open system interconnection, the OSI reference model, which defines a standard framework for connecting heterogeneous computers.

OSI layered model: high-level and data flow layer

High level:

Application layer

2. Presentation layer

3. Session layer

Data stream layer:

4. Transport layer

5. Network layer

6. Data link layer

7. Physical layer

Layer: An effective communication process that describes all the requirements, and the logical group of these processes is called a layer.

Application layer: providing user interface

User Interface: An application that communicates with other computers, corresponding to the application's communication services.

Common application layer protocols: Telnet, SMTP, HTTP, FTP

Presentation layer: Data represents special processing such as encryption (decryption, encoding, decoding). The main functions are to define the data format (ASCII MPG JPEG, etc.) and encryption.

Session layer: guarantees data differentiation between different applications, defines how to start, control and end a session, including control and management of multiple bidirectional sessions, so that the application can be notified when only a part of the continuous message is completed, so that the presentation layer The data seen is continuous.

Transport layer: reliable or unreliable data transmission, error correction before data retransmission. Whether to select the error recovery protocol or the error-free recovery protocol, the input of the data stream of different applications is multiplexed on the same host, and the received data packets are reordered in the wrong order. It also defines a segmentation method for dividing a large block of data into smaller segments. TCP, UDP, SPX.

Network layer: Determines the logical addressing of the path, the format of the packet and address. Defines the logical address that can represent all nodes, and defines how the route is implemented and how it is learned. In order to accommodate transmission media with a maximum transmission unit length less than the packet length, the network layer also defines a segmentation method for how to decompose a packet into smaller packets. IP, IPX

Data Link Layer: Encapsulates into frames, controls access to physical layer media, identifies network devices connected to media, finds errors but cannot correct them. It defines how data is transmitted on a single link. 802.3/802.2, HDLC/PPP, Frame-Relay

Physical layer: Accept or transmit bitstreams between devices to describe voltage, line speed, and cable. Physical layer protocols are divided into functional protocols and procedural protocols. EIA/TIA-232, V.35, RJ45

If you study the cccn well the you can refer to the complete booklist for ccie rs written and lab preparation for the ccie certification. More info reach to evedumps.com cisco tags.