Layer-Based TCP/IP

Network protocols are usually developed at different levels, and each layer is responsible for different communication functions. A protocol family, such as t c p/I p, is a combination of multiple protocols at different levels. T c p/I p is generally considered as a layer-4 protocol system.

1. Relationship between each layer

 

2. features of each layer

Application Layer: responsible for specific application details

Transport Layer: Responsible for end-to-end communication between two computers

Network Layer: process group activities in the Network

Data link layer: Device Drivers and network interface cards

An application is generally a user process, while the lower layer is generally running in the (operating system) kernel. Although this is not necessary, it is usually done in this way, such as the u n I X operating system.

 

3. Various protocols in TCP/IP and the content in charge of the Protocol

T c p and u d p are two of the most famous transport layer protocols, both of which use I P as the network layer protocol. Although t c p uses unreliable I p services, it provides a reliable transport layer service. These applications are generally user processes.
U d p sends and receives data packets for applications. A datagram refers to an information unit transmitted from the sender to the receiver (for example, a certain number of bytes specified by the sender ). However, unlike t c p, u d p is unreliable, and it cannot ensure that the datagram can safely reach the final goal. S n m p also uses the u d p protocol, but it also needs to process more protocols.
I p is the main Protocol on the network layer and is used by T C P and U D p at the same time. Each data group of t c p and u d p is transmitted over the Internet through the end system and the I p layer of each intermediate router. We provide an application that directly queries I p. This is rare, but also possible (some older routing protocols are implemented in this way. Of course, the new transport layer protocol may also use this method ). However, in order to make the content more targeted, some details will be carried out in the subsequent chapters. I c m p is a subsidiary protocol of the I p protocol. The I p layer uses it to exchange error messages and other important information with other hosts or routers.
Although I c m p is mainly used by I p, the application may also ask it. We will analyze two popular diagnostic tools, p I n g and tr a c e r o u t e, both of which use I c m p. I g m p is an I n t e r n e t group management protocol. It is used to multicast an u d p datagram to multiple hosts.
A r p (Address Resolution Protocol) and r a r p (Reverse Address Resolution Protocol) are special protocols used by some network interfaces (such as Ethernet and ring-based network, it is used to convert the addresses used by the I p layer and the network interface layer.

4. IP Address

Each interface on the Internet must have a unique I n t e r n e t address (also known as I P address ). The I P address is 32 bit long. I n t e r n e t address is not flat address space, such as 1, 2, 3. I P address has a certain structure, which is seen in five different Internet address formats.

4.1 differentiate IP addresses

The easiest way to distinguish an IP address is to look at its first decimal bit.