Shulou(Shulou.com)06/01 Report--

1. Model

Physical layer:

Converting data into electronic signals that can be transmitted through a physical medium is equivalent to a porter in a post office.

Bits are transmitted through the media, providing mechanical and electrical protocols.

It mainly defines the physical equipment standard, such as the interface type of network cable, the interface type of optical fiber, the transmission rate of various transmission media and so on. Its main function is to transmit bit stream (that is, from 1, 0 to current strength for transmission, and to 1, 0 after arriving at the destination, that is, what we often call digital-to-analog conversion and analog-to-digital conversion). The data in this layer is called bit.

Data Link layer:

In this layer, the data is framed and the flow control is handled. This layer specifies the topology and provides hardware addressing. Equivalent to the packing and unpacking workers in the post office.

Defines how to allow formatted data for transmission, and how to control access to physical media, and this layer usually provides error detection and correction to ensure reliable data transmission.

Network layer:

Provide connections and path choices between two host systems in networks located in different geographical locations. The development of Internet has greatly increased the number of users accessing information from various sites in the world, and the network layer is the layer that manages this connection.

Transport layer:

Provides a port-to-port connection. (after shielding the lower layer, it can be understood as communication between ports)

Some protocols and port numbers for data transmission (WWW port 80, etc.) are defined, such as: TCP (transmission control protocol, low transmission efficiency, high reliability, used for transmitting data with high reliability and large amount of data), UDP (user Datagram protocol, contrary to TCP, used to transmit data with low reliability and small amount of data, such as QQ chat data is transmitted in this way) The data received from the lower layer is mainly segmented and transmitted, and then reorganized when it reaches the destination address. This layer of data is often called segment.

Session layer:

Establish, manage, and terminate sessions. That is, the path of data transmission is established through the transport layer (port number: transmission port and receiving port), mainly initiating sessions or accepting session requests between your systems (devices need to know each other can be IP, MAC or hostname).

Presentation layer:

Convert, compress and encrypt the data.

It ensures that the information sent by the application layer of one system can be read by the application layer of another system. For example, the PC program communicates with another computer, one of which uses the extended binary Decimal Interchange Code (EBCDIC) and the other uses the American Standard Code for Information Interchange (ASCII) to represent the same characters. If necessary, the presentation layer converts between multiple data formats by using a common format.

Application layer:

Is the OSI layer closest to the user, which provides network services for the user's applications, such as email, file transfer, and terminal emulation.

Data transmission

Common protocols:

Network layer:

IP (IPV4,IPV6): the transport mechanism used by the TCP/IP protocol family at the network layer is an unreliable connectionless Datagram protocol, a nearly best-effort service. Best effort: IP packets may be damaged, lost, out of order or delayed arrival, and may cause network congestion. Lack of error control and auxiliary mechanisms (ICMP resolution). For reliability, rely on the tcp protocol.

ARP (Address Resolution Protocol): address Resolution Protocol-maps the logical address (IP address) from the ip protocol to the corresponding physical address, and then gives the physical address to the data link layer for MAC encapsulation.

RARP (Reverse Address Resolution Protocol): reverse address Resolution Protocol-allows physical machines in a local area network to request their IP addresses from the ARP table or cache of the gateway server.

ICMP (Internet Control Message Protocol) Internet Control message Protocol-- error control and auxiliary mechanism for IP protocol. It is a sub-protocol of the TCP/IP protocol family, which is used to transfer control messages between IP hosts and routers.

IGMP: (Internet Group Management Protocol) is a multicast protocol in the Internet protocol family that is used by IP hosts to report their group membership to any directly adjacent router.

Unicast routing protocols (RIP,OSPF and BGP)

RIP: routing Information Protocol

OSPF: open shortest path first Protocol

BGP: border network management protocol, a routing protocol used to connect independent systems on Internet.

IS-IS: (Intermediate System to Intermediate System Routing Protocol) routing protocol from intermediate system to intermediate system.

IPsec: Internet Protocol Security is an open standard framework that ensures secure and secure communication over Internet Protocol (IP) networks through the use of encrypted security services.

Transport layer:

TCP (Transmission Control Protocol) Transmission Control Protocol.

UDP (User Datagram Protocol) user Datagram Protocol

DCCP (Datagram Congestion Control Protocol) Datagram congestion Control Protocol

SCTP (STREAM CONTROL TRANSMISSION PROTOCOL) flow Control Transport Protocol

RTP (Real-time Transport Protocol or RTP) Real-time Transport Protocol

RSVP (Resource ReSer Vation Protocol) resource reservation protocol

PPTP (Point to Point Tunneling Protocol) Point-to-Point tunneling Protocol

Application layer:

DHCP (dynamic Host allocation Protocol)

DNS (Domain name Resolution)

FTP (File Transfer Protocol) File transfer Protocol

Gopher (English original meaning: The Internet Gopher Protocol Chinese interpretation: (RFC-1436) Internet Gopher Protocol)

HTTP (Hypertext Transfer Protocol) Hypertext transfer Protocol

IMAP4 (Internet Message Access Protocol 4) is the fourth version of the Internet Information access Protocol

IRC (Internet Relay Chat) Network chat Protocol

NNTP (Network News Transport Protocol) RFC-977) Network News transfer Protocol

XMPP Extensible message processing Field Protocol

POP3 (Post Office Protocol 3) is the third version of the Post Office Protocol

SIP signaling control protocol

SMTP (Simple Mail Transfer Protocol) is simple Mail transfer Protocol

SNMP (Simple Network Management Protocol, simple Network Management Protocol)

SSH (Secure Shell) secure Shell Protocol

TELNET Telnet Protocol

RPC (Remote Procedure Call Protocol) (RFC-1831) remote procedure call protocol

RTCP (RTP Control Protocol) RTP control protocol

RTSP (Real Time Streaming Protocol) Real-time streaming Transport Protocol

TLS (Transport Layer Security Protocol) secure Transport layer Protocol

SDP (Session Description Protocol) session description Protocol

SOAP (Simple Object Access Protocol) simple object access Protocol

GTP general data transmission platform

STUN (UDP simple traversal of Simple Traversal of UDP over NATs,NAT) is a network protocol.

NTP (Network Time Protocol) Network timing Protocol

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