Basic UNIX network programming knowledge (1)

1. Hypertext Transfer Protocol (Hypertext Transfer Protocol: HTTP );

Simple Mail Transfer Protocol (SMTP ).

2. PDU (Protocol Data Unit): the Unit information exchanged between peer entities on each layer of the computer network.

3. SDU (Service Data Unit): a Service Data Unit. The PDU of each layer are provided to the Service Interface of this layer through the adjacent lower layer.

Service data unit.

4. Application Layer entity:

A. One two-way byte stream with no length limit is exchanged between TCP application processes.

B. Exchange Between UDP application processes a single record whose length does not exceed the UDP sending buffer size

C. In SCTP (Traffic Control Transfer Protocol), one or more two-way record streams are exchanged between application processes without the total length limit.

5. Transport Layer entity:

In the TCP transmission layer, the sender TCP splits the byte stream data from the application process in order and encapsulates the data in each segment and sends it to the receiver.

TCP.

6. network layer entities:

The PDU exchanged between entities at the network layer is called IP datagram. Its length is limited. IPV4 has a maximum length of 65535 bytes and IPV6 has a maximum length of 65575 bytes.

7. Link Layer entity:

The PDUS exchanged between link layer entities are called frames. Their lengths depend on the specific interfaces.

8. Link Layer:

The IP address is used as the SDU of The Link Layer to pass into the link layer. The data encapsulated by the link layer in frames is called packet ). It is possible to see a group

It is a complete IP data packet. It may also be the result of a new IP header being assigned to a segment of the SDU of an IP data packet.

9. MSS (Maximum Segment Size): Maximum partition Size, which is the interface attribute between the application layer (TCP) and the transport layer.

10. MTU (Maximum Transmission Unit): The Maximum Transmission byte. It is the interface attribute between the network layer and the link layer.