Functions of each layer:
1. Physical layer: (shield the differences between specific transmission media and physical equipment)
- Transmission of bit streams between terminal devices
- Define voltage, interface, transmission distance, etc.
2. Digital link layer:
- Encapsulation into frame
- Error control
- flow control
- Transparent transmission
3. Network layer: (IP datagram, datagram)
- Heterogeneous network interconnection
- Routing & forwarding
- Congestion control
4. Transport layer: (data transmission service between two host processes)
- Provide reliable transmission services for end-to-end
- For end-to-end flow control, error control
5. Application layer:
- Provide web services for application program interfaces
Master the basic structure of the computing network in one picture
Postgraduate entrance examination + spring recruitment + re-examination all the way, repeatedly revised, to
ensure that this picture is rigorous and accurate! !
Common interview questions
1.TCP and UDP
- TCP is a transmission control protocol based on byte stream and connection-oriented to ensure transmission reliability and ensure that data will not be out of order. The application scenario is to transmit large amounts of data. TCP is full duplex.
- UDP is a message-oriented , connectionless datagram service with fast transmission speed, good real-time performance, and high efficiency. The application scenario is high real-time requirements, high speed requirements, no flow control, no congestion control
Supplement: How does TCP ensure reliable transmission?
Realized by sequence numbering and acknowledgment (ACK)
2. Routers and switches
Routers work at the network layer to isolate the broadcast domain. The working range is between multiple subnets. The
switch works at the link layer to isolate conflict domains and connections. All devices belong to a broadcast domain
3. Application layer functions and two major protocols
Application layer: interaction between application processes to complete specific network applications
- Domain Name System
Domain Name System DNS for short
it can be used as a domain name and IP address mapping of distributed database - HTTP protocol
HyperText Transfer Protocol
All World Wide Web (WWW) documents must comply with this standard
4. TCP three-way handshake and four waved hands
- Three handshake
- Wave four times
