Lesson 22 - Network protocol analysis
22.1 Network Model
| OSI Reference Model |
TCP / IP reference model parameters (LINUX ) |
| Application layer |
Application layer |
| Presentation layer |
|
| Session Layer |
|
| Transport Layer |
Transport Layer |
| Network layer |
Network layer |
| data link layer |
Network Interface Layer |
| Physical Layer |
OSI is a network communication model often used in a computer network, corresponding to the four-layer model is linux. NIC driver frequently used, belonging to the data link layer communication model in the network belonging to the network interface layer linux system.
This is a fact to be eliminated TCP / IP 4-layer model agreement. No large-scale use in the world today.
22.1 Network Protocols
l What is a network protocol
First is a network protocol rules, like TFTP protocol we used before.
(1) rules. For TFTP protocol, A transmits a request packet to B, B sends a response packet to A. And this is only a rule, a protocol is composed of multiple rules.
(2) format. The format is another element of the agreement, each packet must have its format.
l protocol framework
The relationship between the protocol l Protocol (reflected in the relationship between the data packet A comprising Relationship)
22.2 packet format
Internet can find a variety of different formats of package, in order to deepen our impression. The package format with real data packets we want to find a comparison. For a better comparison, we can download a software wireshark, network packet capture, packet format and see the real is what follows:
A concrete network protocol and the figure will have some access to the actual subject, in some places "the length of the data field" into "data types." Our IP packets, for example, to see what's inside, as shown below:
VERS: version. HELEN: Length
Specific wireshark follows:
TCP：
UDP：