University of Michigan - Ann Arbor

Proper data routing requires distinct addressing mechanisms across multiple layers:

- **MAC Address**: A permanent hardware address burned into a device's network interface card, used to identify the device on a local network segment.
- **IP Address**: A logical address used to route data across networks. IPv4 addresses consist of four numeric segments (e.g., `192.168.1.5`, totaling ~4 billion addresses), whereas IPv6 introduces longer addresses to accommodate modern scale. IP addresses generally identify a network or region rather than a person's exact physical location.
- **Port Number**: A numerical identifier indicating the specific application or service on a host (e.g., port 80 for HTTP, port 443 for HTTPS). Together, an IP address and a port number uniquely identify a specific program on a specific machine.
- **Domain Name System (DNS)**: Acts as the Internet's directory service, translating human-readable hostnames (such as `example.com`) into numeric IP addresses.

Network Addressing and Identification

Which identifier is combined with an IP address to uniquely identify a specific application or program running on a specific host?

An IP address generally identifies a specific person's exact physical location.

What is the primary function of the Domain Name System (DNS)?

Compare MAC addresses and IP addresses by discussing their address type, where they are assigned or stored, and their respective roles in network communication.

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