TCP/IP Overview

1) The link layer, sometimes referred to as the data link layer or the network interface layer, usually includes the device drivers in the operating system and the corresponding network interface cards in the computer. They work together with the physical interface details of the cable (or any other transmission medium).

2) The network layer, sometimes referred to as the Internet layer, handles the grouping of activities in the network, such as grouping routing. In the T C p/i P protocol family, the network layer protocol includes the I P Protocol (Internet Protocol), I C M P Protocol (i n T e R n E t

Protocol), and the I-G M P Protocol (i-N T e R n E T-Group Management Protocol).

3) The transport layer mainly provides end-to-end communication for applications on two host computers. In the T C p/i P Protocol family, there are two different transport protocols: T C P (Transmission Control Protocol) and U D P (User Datagram Protocol).
T C P provides high-reliability data communication for two hosts. The work that it does involves putting the data that the application gives to it into the appropriate small pieces to the network layer below, confirming the received packet, setting the timeout clock to send the last acknowledgment packet
such as Because the transport layer provides high-reliability end-to-end communication, the application layer can ignore all of these details. On the other hand, the U D P provides a very simple service for the application layer. It only sends packets called datagrams from one host to another, but does not guarantee that the datagram will reach the other end. Any required reliability must be provided by the application layer.

These two transport layer protocols have different uses in different applications, which will be seen later.

4) The application layer is responsible for handling specific application details. Almost all of the different T C p/i P implementations provide the following common applications

? Telnet Telnet.
? FTP file Transfer Protocol.
? SMTP Simple Mail delivery protocol.
? SNMP Simple Network Management protocol.

In the T C p/i P protocol family, the network layer I p provides an unreliable service. In other words, it simply sends the packet from the source node to the destination node as quickly as possible, but does not provide any reliability guarantees. On the other hand, T C P provides a reliable transport layer on the unreliable I P-layer. To provide this reliable service, T C p uses a mechanism such as timeout retransmission, sending and receiving end-to-end acknowledgement packets. Thus, the transport layer and the network layer are responsible for different functions respectively.

T C P and U D P are two of the most well-known transport layer protocols, both using I p as the Network layer protocol.

Although T C P uses unreliable I-p services, it provides a reliable transport layer service.

U D P sends and receives datagrams for the application. A datagram is a unit of information (for example, a certain number of bytes specified by the sender) that is transmitted from the sender to the receiving party. Unlike T C P, however, the U D p is unreliable and does not guarantee that the datagram will arrive at its final destination safely and without error.

I P is the main protocol on the network layer and is used by T C P and U D p. Each set of data for T C p and U D P is transmitted over the Internet through the end system and the I p layer in each intermediate router.

I C M P is a subsidiary agreement of the I P protocol. The I P-layer uses it to exchange error messages and other important information with other hosts or routers.

G M P is the i n T e R n e T Group Management protocol. It is used to multicast a U D P datagram to multiple hosts.

A r P (address Resolution Protocol) and R A R p (inverse address Resolution Protocol) are some network interfaces (such as Ethernet and Token Ring
A special protocol used to convert the addresses used by the I P-layer and the network interface layer.

Each interface on the Internet must have a unique i n T e R n E address (also called an I-P address). The I p address is longer than the bit. I N T e R n E t address does not take a flat form of address space, such as 1, 2, 3 and so on. I P address has a certain structure, five different types of Internet address format

These 3 2-bit addresses are usually written in four decimal digits, where each integer corresponds to one byte. This representation is called "dotted decimal notation (dotted decimal notation)"

Although the network interface on the host can be identified by the I P-address, the host name is the preferred one. In the T C p/i P domain, the domain Name System (D N S) is a distributed database that provides mapping information between the I P address and the host name.

The U D p data is basically consistent with the T C P data. The only difference is that the information unit that U D p transmits to I p is called the U d P datagram (UDP datagram), and the first Minister of U D p is 8 bytes.

Since t C P, U D p, i c M P, and I G m P all transmit data to I p, I p must include some identification in the generated I P header to indicate which layer the data belongs to. To do this, I p in the first deposit a value of 8 B I T, called the protocol domain. 1 is expressed as I C m P protocol, 2 is expressed as I G m P protocol, 6 is expressed as T C P protocol, and 1 7 is expressed as U D P protocol.

Similarly, many applications can use T C p or U D p to transmit data. The Transport layer protocol stores an identifier for an application when generating a message header. T C P and u D p all use a port number of 1 6 b i t to represent different applications. T C P and u D p respectively deposit the source port number and destination port number into the header of the message.

The network interface is to send and receive I P, A R p and r a r p data, and therefore must also include some form of identification in the frame header of the Ethernet to indicate the network layer protocol that generated the data. For this reason, the Ethernet frame header also has a single-bit frame Type field.

Divided by

When the destination host receives an Ethernet data frame, the data begins to rise from the bottom of the protocol stack, removing the headers of each layer protocol. Each layer of the Protocol box is to check the protocol ID in the header to determine the upper layer protocol that receives the data. This process is called a split (D e m u l t i p l e x i n g), and figure 1-8 shows how the process occurs.

I n T e R n E t The first letter of the word is capitalized to determine its different meanings.
I n T e R n e t means to connect multiple networks together with a common protocol family. The I n te R n e t refers to all the host collections (more than 1 0 0 units) that communicate with each other through T-C p/i P in the world. I n T e R n E T is an i n T e R n e t, but i n T e R n e t is not equal to I n T e R n e T.

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TCP/IP Overview