Network fundamentals, ASP. NET Core Knowledge (1) *

Why write a network?

My original plan was this, two days in a row to comb the core knowledge of ASP. Speaking of which, someone asked. " did you say you made the ASP?" Why Write Network Basics? Isn't that stupid? "

the reason is this. As a web developer, the SOFTWARE PRODUCT you develop is ultimately going to run on the web. It is like a manufacturer that produces products for the Northeast, and producers have no knowledge of the weather, geography, and humanity of the northeast. The manufacturer's product is certainly not available, or low-end! The quality of the product is not good, it is natural. The quality of the product is good, that is you a little high. as an ASP. NET developer, the effect is the same if you don't understand the HTTP protocol, don't know Ajax, or even know JavaScript at all.

In short, a wealth of knowledge reserves, will be your software products to bring more quality assurance.

Of course, we want to understand the main is the HTTP protocol, for this article to organize the content, only do understand. The aim is to have a general conception of the whole knowledge system. Forget it, speak frankly. This article is of little significance, and the fundamental reason for writing it is that I want to recall my network knowledge in such a way. After all, once a unwinnable network engineer (and so on, I know no use, but just went to college, thought very bad. It took a little thought to remember college life. Of course, this is just a summary of the comb.

about the architecture

1.OSI, TCP/IP, and five-tier architecture  

Speaking of the architecture of the network, there are a total of two classic partitioning methods, namely OSI layer Seven and TCP/IP layer four.

1) OSI

OSI's seven layer protocol architecture, clarity, integrity. But the complexity is high, but not practical.

2) TCP/IP

Compared to the OSI seven layer complex, TCP/IP four-layer structure has been widely used.

However, from a practical point of view, TCP/IP only uses three layers in practical applications.

3) Five-tier architecture.

TCP/IP the lowest layer of the network interface, there is nothing particularly new specific content, and the general communication link is not much different.

Therefore, in the study of the use of a moderate approach, is the TCP/IP system, and the OSI system combined

Form a five-tier architecture, from the physical layer, the data link layer, the internetwork layer, the transport layer to the application layer.

2. For the five layer protocol, the description of each layer

1) Physical Layer

The mechanical, electrical and functional return journey characteristics of communication equipment are defined. (That was so, I understand that is the case, "square plug, plug not in the round mouth. is to define such a standard? ")

Devices: Hubs (forming a collision domain)

2) Data Link layer

Establish, maintain, and release data links between network entities, a data link that turns the network into an error-free channel. (Mac Media Access Layer, LLC Logic link layer)

Key features Remember three O ' 1. Encapsulating into frames

2. Transparent transmission

3. Error detection

Devices: Bridge, cache, accept Mac frames.

3) Network layer:

belongs to the communication subnet, exchanging the data emitted by the transport layer entity through the network connection. It solves the problem of routing, network congestion and heterogeneous network interconnection. (Sending a message)

IP Internetwork Protocol

ARP Address Resolution Protocol

RARP Reverse Address Resolution Protocol

ICMP Inter-network Control Message Protocol

IGMP Internetwork Group Management Protocol

4) Transport Layer

The end-to-end data packet transmission is implemented by the sending and receiving end, which is responsible for ensuring the error-free, loss-free and non-redundant transmission of packets. (Access point for the service is port)

TCP (Transmission Control Protocol) reliable, connection-oriented, responsive mechanism

UDP (User Datagram Protocol) unreliable, no connection, no response mechanism

5) Application Layer

Although we are program developers, what does the above-mentioned protocol say? To be honest, we don't have much contact with us. To the application layer is closely related to our work.

HTTP Hypertext Transfer Protocol This is what we need to understand.

FTP File Transfer Protocol

DHCP Dynamic Host Configuration Protocol

NFS Network File System

Telnet Remote Login Protocol

DNS Domain Name System

SNMP Simple Network Management Protocol

a few concepts to understand

1.URL

The scientific name of this thing: Uniform Resource Locator. He said he found the resource location of a resource in the Internet and the way to access the resources.

The usual structure is this.

"Agreement"://"host": "Port"/"path"? Request parameters

That's it under HTTP.

http:/"host", "Port"/"path"

2.HTTP protocol

• This article is called: Hypertext Transfer Protocol.
  As the name implies, the HTTP protocol defines how the browser requests documents from the Web server and how the server transmits the document to the browser.
• The HTTP protocol is request-and-response. The wood responds without a request.
• HTTP is text-oriented, so each field in the message is a number of ASCII strings, so the length of each field is indeterminate.
• There are two types of HTTP messages in total, requesting messages and responding messages.
  1) Request message
  2) Response message
• Both the request message and the response message can be divided into three parts.
  1) Start line
  2) Header Line
  My habit is to call the two parts above, the message header. The following section is called the newspaper style. (I don't know if it's right)
  3) Actual subject
• For details, the next article it to write a superficial study of the HTTP protocol.

Network fundamentals, ASP. NET Core Knowledge (1) *