TCP/IP Protocol learning Note one

First, brief

Before learning computer network in school when learning is the Network 7 layer model OSI, understand some basic computer network concepts and protocol communication format, but have not figured out the principle, including the relationship between the layers, applications, there are some common token ring network What is the thing, this OSI it and tcp/ What is the relationship between IP protocol clusters and why are there many protocols? What is the IP instruction format? Why do you always forget, can't remember? What is the 3-time handshake, 4-time handshake protocol? Ack,syn, what do you mean by unknown fields? Why Ethernet network card communication rate is 100mbps, the communication between the two hosts is less than 120KPBS? ... All of these doubts, have to let oneself again pick up the book read "TCP/IP Detailed protocol" Learn why TCP/IP can replace the OSI occupy the Internet, but this time must learn a little bit, have to do notes, let oneself understand more profound concrete, at the same time as their own records can be freely browsed.

Two, TCP/IP protocol layered 2.1 layered structure

Application Layer	Telnet, FTP, SNMP, STMP, DNS, HTTP
Transport Layer	TCP, UDP
Network layer	IP, ICMP, IGMP
Link Layer	Device drivers, network interface cards

Application layer: Handles specific application details.

Transport layer: Also called Transport layer, provides end-to-end communication for two hosts.

Network layer: Handles the grouping of activities in the network.

Link layer: Also called the data link layer, including the device driver in the OS and the computer network interface card, handling the physical interface details of the transmission media such as cables.

2.2 Example of FTP protocol communication between two hosts on a local area net-Lan

Note: 1. The first layer only cares about the communication details in the layer, but does not care about the details of the other layers;

2. The same layer can communicate with each other on the same layer, and the other layers are ignorant;

3. The next layer provides services for the previous tier, but you do not need to know the details.

2.3 Level Agreement Relationship

2.4 Network layer and application layer differences

The two tiers deal with the communication details, why do they have to be divided into two tiers instead of one layer?

Computers need to be in a complex network environment, not only a few hosts of the Simple network, and complex network environment in the network Relay equipment (hardware box, also known as IP router, IP Router), transmission protocol, communication host operating system may have a great difference, Plus the host to handle and specific application of relevant details, if all put on a layer to deal with, will inevitably increase the complexity of the network protocol, as well as the development of IP routers to make it difficult, and let the network transmission of the router to implement certain application-specific services, is not necessary. So it is bound to be divided into two times.

2.5 noun interpretation

IP routers : IP router,router, interconnection network on the network layer.

Gateway : Router formerly known as Gateway (Gateway), gateways now represent only application-tier gateways: Processes that connect two different protocols, such as TCP/IP and IBM's SNA.

End : Also known as two hosts in the End System network communication.

Intermediate Systems : Intermediate system, router between end and end.

Multi-Interface : A router with 2 or more network interface layer, connected to 2 or more networks, called multi-Interface, a host is generally not called a router, because its function is not simply to send packets from one interface to another interface, But in special cases it can be called router, router is for a certain functional role, not for a particular hardware device.

Bridge : A link-layer interconnect network that brings together multiple LANs.

DNS: A distributed database that stores [IP address <-> host name] mappings, managed by InterNIC.

IP protocol provides unreliable services, as soon as possible to send packets from the source node to the destination node, TCP based on IP protocol, but TCP provides a reliable service, TCP Why can reliable service?

TCP uses the mechanism of time-out resend, sending and receiving end-to-end acknowledgment packets.

2.6 IP Address

2.7 Data Packet Encapsulation

2.8 C/S mode

2.9 Port number

2.10 Programming Implementation

TCP/IP Protocol learning Note one