Content provider: Jinniu District Wudi Software Development Studio

Following: Computer network principle [2] network application

Chapter 3: Transport layer

Basic services of the transport layer

1. Transport layer functions

A. Transport layer core functions

B. Seven functions of the transport layer

Transport layer addressing and ports

1. Port number used by the server: familiar port number and registered port number 2. Port number used by the client: temporary, the operating system randomly selects a unique port number that is not used when the client process is running.

3. Connectionless and connection-oriented services

Connectionless service (UDP) : provides connectionless, unreliable datagram transport service. Connection-oriented Service (TCP) : provides connection-oriented, reliable, ordered byte stream transport service

Reuse and decomposition of transport layer

1. Reuse and decomposition

2. Connectionless multiplexing and multiplexing

3. Connection-oriented multiplexing and multiplexing decomposition

Stop-wait protocol and sliding window protocol

1. Basic principles of reliable data transmission

Measures taken to realize reliable data transmission based on unreliable Channel:

2. Stop-wait agreement

Poor performance and low efficiency

3. Sliding window protocol

The serial numbers on the left of the sending window are 1, 2, 3, and 4. The ACK has been received. Send window: Ws=5. 5, 6, 7, 8, and 9 are available group numbers. Number 5 is the number on the right of the base number sending window. Number 10, 11, and 12 are the group numbers that cannot be used temporarily

If 5 and 6 are successful, the serial numbers on the left of the sending window are 1, 2, 3, 4, 5, and 6. ACK has been received. Send window: Ws=5. 7, 8, 9, 10, and 11 are available group numbers. Number 7 is the number on the right of the base number sending window. Number 12 is the number of the group that cannot be used temporarily