Application layer protocols: DHCP PROTOCOL

Application layer protocols are a set of protocols that operate at the highest layer of the OSI (Open Systems Interconnection) model, the seventh layer. These protocols facilitate communication between applications or software programs running on different devices over a network. They define the rules and conventions for data exchange, including formatting, sequencing, error handling, and authentication. Some common application layer protocols include:

1)DHCP

2)HTTP

3)HTTPS

4)FTP

5)SMTP

6)POP3

7)IMAP

8)DNS

1)DHCP

DHCP stands for Dynamic Host Configuration Protocol. It is responsible to assign IP address to the host machine dynamically. We all know that message will be transferred from top most layer to bottom layer. DHCP is an application layer protocol. At application layer DHCP request message will be generated . This request message will be transmitted to the transport layer. At transport layer DHCP request message gets encapsulated and will be placed in UDP packet. UDP packet contains DHCP request message and port number . Then these packet gets transferred to the network layer. In network layer UDP packet gets encapsulated in IP packet. . DHCP client broadcast the IP packet over network. DHCP server will reply the corresponding IP address to DHCP client so that reply may be broadcast or unicast packet. This entire process can be happened with the help of DORA process.

DORA PROCESS:

Client Initialization: When a device (such as a computer, smartphone, or printer) connects to a network, it initially doesn't have an IP address. The device sends out a broadcast message called a DHCPDISCOVER message to discover DHCP servers available on the network.

DHCP Server Offer: DHCP servers on the network receive the DHCPDISCOVER message and respond with a DHCPOFFER message. This message includes an IP address that the server is willing to assign to the client, along with other network configuration parameters such as subnet mask, default gateway, DNS server addresses, lease duration, etc.

Client Request: Upon receiving one or more DHCPOFFER messages, the client selects one of the offers and sends a DHCPREQUEST message to the chosen DHCP server, indicating its acceptance of the offered configuration.

DHCP Server Acknowledgment: The DHCP server that receives the DHCPREQUEST message sends a DHCPACK message to the client, confirming that the offered configuration has been accepted. At this point, the client is configured with the IP address and other network parameters provided by the DHCP server.

Configuration Renewal: The client periodically checks in with the DHCP server to renew its lease on the assigned IP address and to update other network configuration parameters. This typically happens when the lease duration is about to expire, ensuring that devices maintain their network connectivity.