DNS vs. DHCP: Key Differences Explained

This article explores the differences between DNS (Domain Name System) and DHCP (Dynamic Host Configuration Protocol), two essential networking protocols. We’ll cover their full forms, basic functionalities, and how they contribute to a seamless internet experience.

What is DNS? (Domain Name System)

As the title says, DNS stands for Domain Name System. It relies on DNS servers to function. Think of a DNS server as a phone book for the internet. It translates human-readable domain names (like google.com) into IP addresses (like 172.217.160.142), which computers use to locate each other.

This translation is necessary because it’s much easier for us to remember names than long strings of numbers.

Before DNS, managing a file called “hosts” was necessary to manually store IP addresses and corresponding names. As the internet grew, keeping an updated copy of this file on every computer became impossible, leading to the development of DNS.

DNS address resolution

DNS works by exchanging messages between client and server. When a user types a domain name into a browser, the application sends a request to a DNS server to resolve the corresponding IP address.

As depicted in Figure 1 (above), physical networks use hardware addresses, the internet utilizes IP addresses, and applications and users interact with symbolic addresses like domain names. ARP/RARP protocols facilitate the conversion between IP and MAC addresses. DNS bridges the gap between domain names and IP addresses.

DNS Hierarchy and Syntax

DNS Hierarchy and Syntax

DNS is structured as a distributed database, organized in a hierarchical manner using name servers. As illustrated in Figure 2, a domain name consists of a TLD (top-level domain), a label, and a host name. Organizations need to obtain a TLD (e.g., .com, .org, .edu) from a central authority.

DNS Servers and Resolvers

• DHCP’s Role: DHCP is essential at the beginning of an internet connection, allowing a client to obtain an IP address from a DHCP server.
• DNS’s Role: Once a connection is established, and a user enters a domain name in a browser, the application uses a DNS resolver to obtain the corresponding IP address.
• Most applications prioritize the order of addresses provided by the DNS resolver.

What is DHCP? (Dynamic Host Configuration Protocol)

DHCP stands for Dynamic Host Configuration Protocol.

• DHCP is defined in RFC 2131.
• It operates over UDP.
• It automates the configuration of hosts connected to a network or booted while connected.
• It provides hosts with initial configuration data, including:
  • IP address with subnet mask
  • Default gateway
  • IP address of the DNS server

How DHCP Works

How DHCP works

Figure 4 illustrates the DHCP process. A DHCP client requests its configuration from a DHCP server. The server then responds with the necessary information, such as the IP address, subnet mask, default router, DNS servers, and lease time.

DHCP Messages

DHCP messages exchanged

The following table describes the different DHCP messages exchanged between a DHCP server and a DHCP client:

Tabular Difference Between DNS and DHCP

Here’s a table summarizing the key differences between DNS and DHCP: