application layer protocols

application layer protocols

1. application, presentation and session

   • application layer
     • It is the closest to the end user.
   • Layers of presentation and session
     • he presentation layer formats the data for the application layer and sets standards for the file formats,As the name implies, the session layer functions create and maintain dialogs between the source and destination applications.
   • TCP / IP application layer protocols
     • specify the format and control information needed for many common Internet communication functions.

2. how application protocols interact with end-user applications

   • Client-server model
     • the device that requests information is called "client", and the device that responds to the request is called "server".
   • Networks between pairs
     • In the peer-to-peer network model (P2P), data from an even device is accessed without using a dedicated server.
   • Applications between pairs
     • allows a device to function as a client and server within the same communication, as shown in the figure.
   • Common P2P applications
     • each PC in the network that runs the application can function as a client or as a server for the other PCs in the network that are running the application.

3. e-mail web protocol

   • Hypertext transfer protocol and hypertext markup language
     • When you type a web address or a uniform resource locator (URL) in a web browser, the browser establishes a connection to the web service that runs on the server using the HTTP protocol
   • HTTP y HTTPS
     • HTTP is a request / response protocol. When a client, usually a web browser, sends a request to a web server, HTTP specifies the types of messages that are used for that communication.
   • Email protocols
     • Uno de los principales servicios que un ISP ofrece es hosting de correo electrónico.
   • Operation of SMTP
     • They need a header and a message body.
   • Operation of POP
     • is used by an application to retrieve email from a mail server
   • Operation of IMAP
     • is another protocol that describes a method to retrieve email messages. Unlike POP, when the user connects to a server with IMAP capability, copies of the messages are downloaded to the client application

4. IP addressing services

   • Domain name service
     • In data networks, devices are labeled with numeric IP addresses to send and receive data through networks
   • Formato del mensaje DNS
     • In data networks, devices are labeled with numeric IP addresses to send and receive data through networks
   • DNS Hierarchy
     • utiliza un sistema jerárquico para crear una base de datos que proporcione la resolución de nombres.
   • El comando nslookup
   • DHCP operation

5. file exchange service

   • File Transfer Protocol
     • is another application layer protocol that is commonly used.
   • Server message block
     • The server message block (SMB) is a client / server file exchange protocol that describes the structure of shared network resources, such as files, directories, printers, and serial ports.

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