Devices on a network require distinct identifiers to ensure data reaches the correct destination at different network layers.

A **MAC address** (Media Access Control address) is a permanent hardware address burned into a device's network interface card. It identifies a specific device on a local network segment and is used for direct, local communication.

An **IP address** (Internet Protocol address) is a logical address used to route data packets across multiple independent networks. IPv4 addresses, formatted as numbers such as `192.168.1.5`, provide roughly 4 billion unique addresses. Because IPv4 addresses became scarce, IPv6 was introduced with significantly longer addresses to support a vastly larger quantity of connected devices.

Contrary to the misconception that an IP address pinpoints an individual's exact physical location, it typically identifies a general network or geographic region. Furthermore, multiple devices can share a single public IP address through Network Address Translation (NAT).

MAC and IP Addresses

While an IP address directs data to a specific machine across the network, a **port number** identifies the specific application or service on that machine intended to receive the data.

Standard services listen on designated port numbers by convention. For instance, web servers typically listen for unencrypted web traffic on port 80 (HTTP) and encrypted web traffic on port 443 (HTTPS).

Together, the combination of an IP address and a port number uniquely identifies both the target host and the exact running process or software service on that host.

Port Numbers and Program Identification

Network addressing is facilitated by automated systems that translate identities and configure host parameters.

The **Domain Name System (DNS)** functions as the directory or "phone book" of the Internet. It translates human-readable hostnames, such as `example.com`, into the numeric IP addresses required by computers to route packets.

The **Dynamic Host Configuration Protocol (DHCP)** automates network setup by assigning an IP address to a device automatically when it connects to a network, removing the need for manual configuration.

Domain Name System and DHCP

University of Michigan - Ann Arbor

Ch.2 Addressing and Resolution Services - Demystifying Network Architecture: Protocols, Addressing, and Packet Flow @ University of Michigan - Ann Arbor

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