What is the level of protocol in the computer?

SMPP (short message peer-to-peer) protocol is an open message conversion protocol. It defines a series of operating protocol data units (PDUS) and data exchanged between ESMS application system and smsc when SMPP is running. Thus, SMSC and Esme were completed.

Information exchange (external short message entity). Smpp is based on the exchange of request and response protocol data units between SMSC and ESME. Each SMPP operation consists of a request pdu and a corresponding response PDU, and this switch connection is in TCP/IP or x.25 network.

Above.

1, which is different from CMPP/SGIP protocol.

The definition of 1) protocol is stricter and more standardized than that of CMPP and SGIP, although both CMPP and SGIP originated from SMPP.

2) In 2)CMPP and SGIP have many definitions about charging, but SMPP does not consider this part. This fully reflects the maturity and popularity of the mobile value-added service mode realized by SMS in China.

3) 3) The network bearer layer of SMPP can be TCP/IP and X.25

2.SMPP protocol solves the interaction problem between short message entities outside the mobile network and short message centers. That is, external short message entities (ESMES) outside the mobile network are allowed to connect with the short message center (SMSC) to submit and accept short messages.

News.

3.SMPP protocol defines 1) a set of interactive operations between ESME and SMSC, and 2) the data format of interactive operations between 2)ESMS and SMSC.

4. Any SMPP operation includes a request protocol data unit and a corresponding PDU (response protocol data unit).

5.SMPP divides ESMEs into three interactive modes, namely sender/receiver/receiver, which respectively correspond to the three modes: SMS submission only/SMS reception only/SMS submission and reception.

6.SMPP session has five states: Open/Binding _ Send/Binding _ Receive/Binding _ Send/Close.

7. PDU defined by 7.SMPP includes

TCP/IP protocol

Brief introduction of TCP/IP protocol

TCP/IP communication protocol

This part briefly introduces the internal structure of TCP/IP, which lays the foundation for discussing the security issues related to the Internet. TCP/IP protocol suite is popular partly because it can be used in various channels and underlying protocols (such as T 1 and X.25, Ethernet and RS-23).

Serial interface). Specifically, TCP/IP protocol is a set of protocols including TCP protocol and IP protocol, UDP (User Datagram Protocol), ICMP (Internet Control Message Protocol) and so on.

Overview of TCP/IP overall architecture

TCP/IP protocol does not fully conform to the seven-layer reference model of OSI. Traditional open system interconnect is a seven-layer abstract reference model of communication protocols, in which each layer performs a specific task. The purpose of this model is to make all kinds of hardware communicate with each other at the same level.

Letter. These seven layers are: physical layer, data link layer, network layer, transport layer, session layer, presentation layer and application layer. TCP/IP communication protocol adopts a four-layer hierarchical structure, and each layer calls the network provided by its next layer to fulfill its own requirements. These four layers are:

Application layer: the communication layer between applications, such as Simple Email Transfer (SMTP), File Transfer Protocol (FTP), Network Remote Access Protocol (Telnet), etc.

Transport layer: At this layer, it provides data transmission services between nodes, such as Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). TCP and UDP add transmission data to the data packet and transmit it to the next layer, which is responsible for transmitting data and determining data.

Has been delivered and received.

Internet layer: responsible for providing basic data packet transmission functions, so that each data packet can reach the destination host (without checking whether it is received correctly), such as Internet Protocol (IP).

Network interface layer: the management of actual network media, which defines how to use the actual network (such as Ethernet, serial line, etc.). ) to transmit data.

TCP/IP protocol

Here is a brief introduction to the functions of the protocols in TCP/IP and how they all work:

1. Internet Protocol

Internet protocol IP is the core of TCP/IP and the most important protocol in the network layer.

The IP layer receives the data packets sent by the lower layer (network interface layer such as Ethernet device driver) and sends the data packets to the higher layer-TCP or UDP layer; Conversely, the IP layer also transmits the packets received from the TCP or UDP layer to the lower layer. IP packet is not reliable.

Because IP didn't do anything to confirm whether the packets were sent in order or not damaged. An IP packet contains the address (source address) of the host that sent it and the address (destination address) of the host that received it.

Advanced TCP and UDP services usually assume that the source address in the packet is valid when receiving the packet. It can also be said that IP addresses form the authentication basis of many services, which believe that data packets are sent from valid hosts. The IP confirmation contains an option,

It is called IP source routing and can be used to specify a direct path between the source address and the destination address. For some TCP and UDP services, IP packets using this option seem to be delivered from the last system on the path, not from its real situation.

Be practical. This option is used for testing, which shows that it can be used to trick the system into making connections that are usually prohibited. Then many services that rely on IP source address for confirmation will have problems and will be illegally invaded.

2. Transmission Control Protocol.

If there are sealed TCP packets in IP packets, IP will send them up to the TCP layer. TCP sorts and detects data packets, and at the same time realizes the connection between virtual circuits. TCP packets contain sequence numbers and acknowledgement information, so packets received out of order may

Classified and damaged packets can be retransmitted.

TCP sends its information to higher-level applications, such as Telnet servers and clients. The application sends the information back to the TCP layer in turn, and the TCP layer sends them down to the IP layer, device drivers and physical media, and finally to the receiver.

Connection-oriented services (such as Telnet, FTP, rlogin, X Windows and SMTP) require high reliability, so TCP is used. DNS uses TCP (sending and receiving domain name database) in some cases, but uses UDP to transmit information about a single host.

3. User Datagram Protocol.

UDP and TCP are in the same layer, but the packets are out of order or retransmitted. Therefore, UDP is not suitable for connection-oriented services that use virtual circuits. UDP is mainly used for query-response oriented services, such as NFS. Compared with FTP or Telnet, these services require

The amount of information to be exchanged is very small. Services that use UDP include NTP (Internet Protocol) and DNS(DNS also uses TCP).

It is easier to cheat UDP packets than TCP packets, because UDP has not established the initial connection (also called handshake) (because there is no virtual circuit between the two systems), which means that UDP-related services are more dangerous.

4. Internet control messages protocol.

ICMP is located on the same layer as IP and is used to transmit control information of IP. It is mainly used to provide path information to the destination address. ICMP's "redirection" information informs the host of a more accurate path to other systems, while the "unreachable" information indicates that

There is something wrong with the path. In addition, if the path is unavailable, ICMP can "gracefully" terminate the TCP connection. PING is the most commonly used ICMP-based service.

5. Port structure of 5.TCP and UDP

TCP and UDP services usually have a client/server relationship. For example, the Telnet service process starts to idle on the system, waiting for a connection. Users use Telnet clients to establish connections with service processes. The client program writes information into the service process,

The service process reads the information and sends a response, and the client program reads the response and reports it to the user. Therefore, this connection is duplex and can be used for reading and writing.

How to confirm and coordinate multiple Telnet connections between two systems? TCP or UDP connections are uniquely acknowledged using the following four items in each message:

Source IP address The IP address of the sending packet.

Destination IP address The IP address of the receiving packet.

Source Port The connection port on the source system.

Target Port The connection port on the target system.

A port is a software structure used by a client program or service process to send and receive information. One port corresponds to 16 bits. Service processes usually use fixed ports, for example, SMTP uses 25 and Xwindows uses 6000. These port numbers are "widely known",

Because these addresses and destination addresses are needed for communication when establishing a connection with a specific host or service.

I believe everyone has heard of the word TCP/IP. It seems to be everywhere and will always pop up in front of you. So what exactly does TCP/IP mean?

TCP/IP is actually a combination of two basic network protocols: IP protocol and TCP protocol name. Let's take a look at these two ubiquitous protocols separately.

internet protocol

The literal translation of the English name of IP(Internet Protocol) protocol is: Internet Protocol. From this name we can know the importance of IP protocol. In real life, when we transport goods, we always put them in cartons or containers.

Traffic, in the network world, all kinds of information are transmitted in a similar way. The IP protocol specifies the basic unit and format of data transmission. If it is compared to the transportation of goods, the IP agreement stipulates the packing box size and packing procedure when packing goods. In addition to these,

The IP protocol also defines the transmission method and routing of data packets. Similarly, using the metaphor of cargo transportation, IP agreement stipulates the mode and route of cargo transportation.

TCP protocol

We already know that IP protocol is very important. The IP protocol specifies the main contents of data transmission. What does TCP (Transmission Control Protocol) do? I don't know if you have noticed that the transmission defined in the IP protocol is one-way, that is,

We don't know whether the delivered goods have been received by the other party. It's like an ordinary letter of 80 cents. What if I send an important letter by registered mail? TCP protocol is to send "registered mail" for us. TCP protocol provides reliable object-oriented data flow.

Rules and practices of transport services. Simply put, in TCP mode, the other party sends you a packet, and you have to send the other party a confirmation packet. This confirmation provides reliability.

TCP/IP (short for Transmission Control Protocol/Internet Protocol, translated from Chinese into Transmission Control Protocol/Internet Protocol) is the most basic protocol of the Internet. Simply put, it is composed of the underlying IP protocol and TCP protocol.

The development of TCP/IP protocol began in 1970s, and it is the first set of protocols used on the Internet.

1. 1 TCP/IP reference model

The developers of TCP/IP protocol divide the Internet into five levels for easy understanding. Also known as Internet hierarchical model or Internet hierarchical reference model, as shown in the following table:

Application layer (fifth layer)

Transport layer (Layer 4)

Internet layer (third layer)

Network Interface Layer (Layer 2)

Physical layer (first layer)

Physical layer: the basic hardware corresponding to the network, which is also the physical composition of the Internet, that is, the hard devices we can see, such as PC, Internet server, network equipment, etc. It is necessary to standardize the electrical characteristics of these hard devices so that they can be connected with each other.

Connectivity and compatibility.

Network interface layer: it defines the rules for composing data into correct frames and transmitting frames in the network. Frame refers to a string of data, which is the unit of data transmission in the network.

Internet layer: This layer defines the format of "data packets" transmitted in the Internet and the forwarding mechanism of "data packets" from users to final destinations through one or more routers.

Transport layer: Establish, manage and tear down a reliable and effective end-to-end connection between two user processes.

Application layer: It defines the process by which applications use the Internet.

1.2 internet protocol IP

A key underlying protocol used on the Internet is the Internet protocol, which is usually called IP protocol. We use the * * * communication protocol to make the Internet a network that allows different types of computers and different operating systems to connect. Make two sets

When computers communicate with each other, they must use the same "language". Communication protocol is just like the same language used by two computers to exchange information, which stipulates the protocol that both parties should abide by in communication.

The communication protocol of computers accurately defines all the details of the communication process between computers. For example, the format and meaning of the information sent by each computer, under what circumstances should the specified special information be sent, and what response should the receiving computer make, etc.

Internet protocol IP protocol provides flexibility to adapt to all kinds of network hardware, and has almost no requirements for the underlying network hardware. As long as binary data can be transmitted from one place to another, any network can join the Internet with IP protocol.

If you want to communicate on the Internet, every computer connected to the Internet must abide by the IP protocol. To this end, every computer that uses the Internet must run IP software and be ready to send or receive information at any time.

IP protocol is of great significance to network communication: many LANs form a huge and rigorous communication system by installing IP software on computers in the network. So that the internet seems real, but it is actually a kind of right and wrong.

The existing virtual network only connects all computer LANs in the world that are willing to access the Internet with IP protocol, so that they can communicate with each other.

1.3 transmission control protocol TCP

Although computers can send and receive data by installing IP software, IP protocol cannot solve the problems that may occur in data packet transmission. Therefore, in order to solve possible problems, computers connected to the Internet also need to

Install TCP protocol to provide reliable and correct communication services.

TCP protocol is called end-to-end protocol. This is because it plays an important role in the connection between two computers: when one computer needs to connect with another remote computer, TCP protocol will let them establish the connection, send and receive data and terminate the connection.

Transmission control protocol TCP protocol provides reliable communication connection for applications by using retransmission technology and congestion control mechanism, so that it can automatically adapt to various changes on the Internet. Even when the Internet is temporarily blocked, TCP can ensure the reliability of communication.

As we all know, the Internet is a huge international network. Congestion and idle time on the network always alternate, and the transmission distance is different, so the time spent transmitting data will also change. TCP protocol has the function of automatically adjusting the "timeout value", which can

It can adapt to various changes on the Internet and ensure the correct transmission value.

Therefore, we can know from the above that IP protocol only ensures that computers can send and receive packet data, while TCP protocol can provide a reliable, controllable and full-duplex information flow transmission service.

To sum up, although IP and TCP have different functions and can be used separately, they are designed as a protocol and their functions are complementary. Only the combination of the two can ensure that the internet is in a complex

Normal operation in the environment. All computers that want to connect to the Internet must install and use these two protocols at the same time, so in practice, these two protocols are often collectively referred to as TCP/IP protocols.

1.4 IP address and its classification

All computers connected to the Internet, from mainframes to microcomputers, appear as independent identities, which we call hosts. In order to realize communication between hosts, each host must have a unique network address. It's like every house has a unique house number.

To avoid confusion when transmitting data.

The network address of the Internet refers to the address number of the computer connected to the Internet. Therefore, in the Internet network, the network address uniquely identifies a computer.

We all know that the Internet is made up of tens of millions of interconnected computers. And we want to confirm every computer on the network by being able to uniquely identify the computer's network address, which is called the abbreviation of IP (Internet Protocol) address.

, that is, the address expressed in internet protocol language.

At present, the IP address is a 32-bit binary address on the Internet. For easy memory, they are divided into 4 groups of 8 bits, separated by decimal points and represented by 4 bytes. Moreover, the value range of each byte separated by dots is 0~255, such as 202.6438+05438+06.0.6438+.

This writing method is called dot notation. IP addresses can identify any network and computers in the network, while identifying computers in other networks or networks is determined according to the classification of these IP addresses. Generally, the IP address is based on the size of the network where the node computer is located.

It is divided into three categories: A, B and C. The default network mask is determined according to the first field in the IP address.

1. Class address

The expression range of Class A address is: 0.0.0 ~ 126.255.255.255, and the default network mask is 255.0.0; Class A addresses are assigned to very large networks. Class A networks use the first set of numbers to represent the address of the network itself, and the last three sets of numbers are connected to the network.

The address of the host. It is assigned to a large network with a large number of hosts (direct individual users) and a small number of LANs. Such as IBM's network.

2. Class B address

The range of Class B address is:128.0.0 ~191.255.255.255, and the default network mask is: 255.255.0.0; Class B addresses are assigned to general medium-sized networks. Class B networks use the first and second sets of numbers to represent network addresses, and the last two sets of numbers represent host addresses on the network.

3. Class C address

The expression range of Class C address is: 192.0.0 ~ 223.255.255.255, and the default network mask is: 255.255.0; Class C addresses are assigned to small networks, such as general local area networks and campus networks, which can connect the least number of hosts. Its users are divided into

Manage several network segments. Class C networks use the first three sets of numbers to represent the network address, and the last set of numbers as the host address on the network.

In fact, there are also class D addresses and class E addresses. However, these two types of addresses have special purposes. Here is just a brief introduction: Class D addresses are called broadcast addresses, which are used by special protocols to send information to selected nodes. Class e addresses are reserved for future use.

Every networked computer, no matter what IP address it belongs to, is in an equal position with other computers in the network, because only IP address is the only identifier to distinguish computers. Therefore, the above classification of IP addresses only applies to network classification.

In the Internet, a computer can have one or more IP addresses, just as a person can have multiple communication addresses, but two or more computers cannot * * * share an IP address. If there are two computers with the same IP address, no matter which one, it will cause an exception.

The computer will not work properly.

By the way, several special IP addresses:

The destination of 1. broadcast address is all hosts on a given network, and the host segment is generally 0.

2. The destination of a unicast address is a single host address on the specified network.

3. The destination of multicast address is all host addresses in the same group.

4. The loopback address 127.0.0. 1 will be used for loopback test and broadcast test.

1.5 Subnet Division

If the company is not online, it will not worry about the IP address, because it can use all IP addresses at will, whether it is Class A or Class B, and it will not think of using subnets at this time, but if it is online, the IP address will be precious.

Now there is an internet craze all over the world. There are fewer and fewer IP addresses, and the applied IP addresses are relatively conservative at present. Only the applied IP address can be used online, but for some companies, only one class C IP address can be applied, but there are many.

If you need to use a point, then you need to use a subnet at this time, which requires consideration of subnet division. Let's briefly introduce the principle of subnet and how to plan it.

1.5. 1 subnet mask introduction

Set up any device on any network, whether it is a host, PC, router, etc. , you need to set an IP address followed by a so-called netmask. The main purpose of this netmask is to obtain the network number from the IP address (that is, IP).