tcp/ip-link Layer

tcp/ip-link Layer

Danbo 2015-8-21

Four levels of the TCP/IP protocol cluster:

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) . such as MAC address addressing, ARP, and so on.
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 I p Protocol (Internet Protocol), I C m P protocol (i n T e R n e t internet Control Message Protocol), and I G m P protocol (i n T e R n e T Group Management Protocol). IP, ICMP, IGMP are stateless. Refers to: The next transmission can remember the ability to transmit information. HTTP is stateless, and DNS is stateful.
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 it does involves dividing the application into its pieces into appropriate chunks to the following network layer, confirming the received packet, setting the timeout clock for sending the last acknowledgment packet, and so on. 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 Transfer protocol.
SNMP Simple Network Management protocol.

Two networks connected through the router:

Most Web applications are designed to be client-server models.
Both parties have corresponding one or more protocols for communication.
The application is usually a user process, while the next three tiers are typically executed in the kernel.
The application layer cares about the details of the application, and the next three layers deal with communication details.

We can divide the end system (two hosts on both sides) and the intermediate system (intermediate systems) (the middle router). The application layer and Transport layer use end-to-end (En d-t o-e n d) protocols. In, only the end system requires these two tiers of protocol. However, the network layer provides a hop-by-step (Ho p-b y-h o P) protocol, which is used by two-terminal systems and every intermediate system.

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.

tcp/ip-link Layer