Network architecture: seven-layer protocol interpretation

Layer Seven Protocol:

Physical Layer :

The computer is connected by a network cable/radio wave, while the physical device only transmits electrical signals (high (1) low (0) levels!

Example://010101010000111010101010101010 (data that needs to be passed)

Data Link layer :

Pure 0 and 1 have no practical significance! 0 and 1 must be grouped and interpreted in a defined way!

Ethernet protocol: LAN protocol! Put forward the concept of "packet"!

Network layer :

The network layer is mainly: the establishment of "host/IP" to "host/IP" connection between.

So what if you find the only computer in the network?

can be accessed via network address

Network Address-->IP Address: Find the only computer in the network by IP address!

IP address: Can be used as an area address:

such as: Country/Province/County/district/community ...

MAC address: Can be used as the home number!

IP address: is the only one! mark the only computer in the network!

and subnet mask: Determine the subnet where the current computer is located! By doing the "and/and" operation with the subnet mask and IP address, the resulting value is identified

The subnet where the current IP address resides!

Router: Gateway. Send your message in a routed form!

DNS server: resolves the domain name! Responsible for resolving the domain name into an IP address!

Transport Layer :

The transport layer is: establish the "port" to "port" communication between!

The network layer can only let the computer receive and send information, but do not know which application should be passed to!

How do I establish communication between "application" and "Application"?

is actually a number for each application that uses a NIC

where port: 0 ~ 65535;  0~1024 is System-occupied! More than 1024 can be set by themselves!

TCP protocol: Secure connection Protocol/three-time handshake protocol: To ensure the safe transmission of information, no loss of information!

UDP Protocol: Packet header protocol. Don't care if you can receive the information.

The common denominator of TCP and UDP protocols: both must be accompanied by a port number!

Router/switch: With network addressing, you can find the only computer in the network based on the IP address!

Session Layer :

The main set up a set of automatic receiving and sending information, automatic Network addressing mechanism!

Presentation layer :

Solve the communication problems between different systems.

Application Layer :

Specify the data transfer format for your application!

HTTP protocol: Hypertext Transfer Protocol!

File protocol: Files Transfer Protocol!

Mail protocol: Email protocol!

How information is delivered in the network:

1. Broadcast: information is transmitted in the same LAN as broadcast!

2. Routing: Information is spread across different LANs! In the form of routing!

Packet: Divided into header and data

Ethernet packet: The total size of an Ethernet packet is no more than 1500 bytes !

Header: The sender and receiver's MAC address!

Data: Data that needs to be passed! (maximum 1500 bytes)

IP packet: IP packet placed in the data portion of the Ethernet packet! IP packets typically do not exceed 65,535 bytes !

Also divided into headers and data

Header: IP address of both sides

Data: Data that needs to be passed!

Unpacking: when the IP packet is larger than the Ethernet packet, it needs to be split and sent !

IP packet: 5,000 bytes!

{<1> {IP packet: Header: 20 bytes: Data: 1480 (0~1479)}}

{<2> {IP packet: Header: 20 bytes: Data: 1480 (1480~2959)}}

{<3> {IP packet: Header: 20 bytes: Data: 1480 (2960~4439)}}

{<4> {IP packet: Header: 20 bytes: Data: 540 (4439~4979)}}

Transport Layer:tcp/udp; The total size of the general Transport Layer packet will not exceed 65,535 bytes! The data portion of an IP packet can drop exactly one transport Layer packet!

{

TCP/UDP Data Packets

Header: The port number of both sides!

Data: Data section

Application Tier Data!

Pack: After you get the packets, combine them sequentially to get the complete data!

Socket: Sockets/Sockets! Used to solve the communication problems of applications between different computers!

  

HTTP protocol! Instant communication

Socket: "host" + "port" = socket/socket; Just a communication model, not a seven Layer protocol (network protocol).

and a Socket contains at least 2 layers of protocol: Network layer/Transport layer .

Network architecture: seven-layer protocol interpretation