What is the transport layer protocol that provides reliable transmission?

The transport layer protocol that provides reliable transmission is the TCP protocol. The TCP protocol is a transmission protocol specially designed to provide reliable end-to-end byte streams on unreliable Internet networks. The design goal of TCP is to dynamically adapt to the various characteristics of the Internet.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

The transport layer protocol that provides reliable transmission is the TCP protocol.

TCP protocol introduction:

Transmission Control Protocol (TCP, Transmission Control Protocol) is a transmission specially designed to provide reliable end-to-end byte streams on unreliable Internet networks. protocol.

Internetwork is very different from a single network, as different parts of the internetwork may have drastically different topologies, bandwidth, latency, packet sizes and other parameters. The design goal of TCP is to dynamically adapt to these characteristics of the Internet and to be robust in the face of various failures.

Reliable, pipe-like connections are often required between application layers of different hosts, but the IP layer does not provide such a flow mechanism, but provides unreliable packet switching.

The application layer sends a data stream represented by 8-bit bytes for inter-network transmission to the TCP layer, and then TCP partitions the data stream into segments of appropriate length (usually affected by the network to which the computer is connected). The maximum transmission unit (MTU) limit of the data link layer). TCP then passes the resulting packet to the IP layer, which transmits the packet through the network to the TCP layer of the receiving entity. In order to ensure that packet loss does not occur, TCP gives each packet a sequence number. At the same time, the sequence number also ensures that the packets transmitted to the receiving end entity are received in order.

Then the receiving entity sends back a corresponding acknowledgment (ACK) for the successfully received packet; if the sending entity does not receive the acknowledgment within a reasonable round trip delay (RTT), then the corresponding data The packet is assumed to have been lost and will be retransmitted. TCP uses a checksum function to check whether the data has errors; checksums are calculated both when sending and receiving.

Related expansion:

Composition of TCP/IP protocol

The TCP/IP protocol refers to the OSI architecture to a certain extent. There are seven layers in the OSI model. From bottom to top they are the physical layer, data link layer, network layer, transport layer, session layer, presentation layer and application layer. But this is obviously somewhat complicated, so in the TCP/IP protocol, they are simplified to four levels.

(1) The services provided by the application layer, presentation layer and session layer are not very different, so in the TCP/IP protocol, they are merged into one layer of the application layer.

(2) Since the transport layer and network layer play a very important role in the network protocol, they are regarded as two independent layers in the TCP/IP protocol.

(3) Because the contents of the data link layer and the physical layer are similar, they are merged into one layer of the network interface layer in the TCP/IP protocol. The TCP/IP protocol with only a four-layer architecture is much simpler than the OSI with a seven-layer architecture. This is why the TCP/IP protocol is more efficient and lower cost in actual applications.

Introduce the four levels in the TCP/IP protocol respectively.

Application layer: The application layer is the first layer of the TCP/IP protocol and directly provides services to the application process.

(1) Different types of applications will use different protocols in the application layer according to their own needs. Mail transmission applications use the SMTP protocol, World Wide Web applications use the HTTP protocol, and remote login service applications use the There is TELNET protocol.

(2) The application layer can also encrypt, decrypt, and format data.

(3) The application layer can establish or terminate connections with other nodes, which can fully save network resources.

Transport layer: As the second layer of the TCP/IP protocol, the transport layer plays a mainstay role in the entire TCP/IP protocol. And in the transport layer, TCP and UDP also play the mainstay role.

Network layer: The network layer is located at the third layer of the TCP/IP protocol. In the TCP/IP protocol, the network layer can perform functions such as establishing and terminating network connections and searching for IP addresses.

Network interface layer: In the TCP/IP protocol, the network interface layer is located on the fourth layer. Since the network interface layer merges the physical layer and the data link layer, the network interface layer is not only the physical medium for transmitting data, but also provides an accurate line for the network layer.

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