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4.2 Application layer protocols - Coggle Diagram

- - - - Compressing data
      - Encrypting data
      - Formatting data at the source device into a compatible form for the receiving device
    - - Create and maintain dialogs between source and destination applications
- - - - when a web address or uniform resource locator(URL) is typed into a web browser ,the web browser establish a connection to the web service running on the server, using the HTTP protocols.
    - - HTTP is a request /respond protocol
        
        three command HTTP message are
        
        GET
        
        POST
        
        PUT
      - HTTP Secure (HTTPS) protocol
        uses encryption and authentication to secure data.
    - - email clients communicate with mail servers to send and receive email
        
        Three protocols for email:
        
        ◦ Simple Mail Transfer Protocol
        
        (SMTP) to send email. ◦ Post Office Protocol (POP) to
        
        retrieve email. ◦ Internet Message Access Protocol
        
        (IMAP) to retrieve email.
    - - used to send email
    - - used to retrieve email from mail server
- - - - also called the domain name space
        
        inverted tree structure, much like eDirectory.
        
        DNS tree has a single domain at the top of the structure called the root domain.
        
        root domain are the top-level domains that divide the DNS hierarchy into segments.
  - - - Each message consists of a header and four sections: question, answer, authority, and an additional space. A header field (flags) controls the content of these four sections.
  - - - DHCP works in a client/server mode and operates like any other client/server relationship.
      - DHCP enables clients on an IP network to obtain or lease an IP address or configuration from a DHCP server. This can reduce the workload of managing large networks.
  - - - The Domain Name Server (DNS) is equivalent to the phone book on the Internet. They maintain a directory of domain names and convert them to Internet Protocol (IP) addresses. This is necessary because although it is easy for people to remember the domain name, computers or machines still access websites based on IP addresses.
  - - - Network administration command-line tool available in many computer operating systems for querying the Domain Name System (DNS) to obtain domain name or IP address mapping, or other DNS records. The name "nslookup" means "name server lookup"