Which identifies both the source and destination location?

An IP address operates at OSI Layer 3 and is embedded in every packet header as both a source address and a destination address, enabling routers to forward traffic between networks. Unlike MAC addresses, IP addresses are routable and meaningful beyond a single network segment, making them the standard identifier for 'where traffic comes from' and 'where it is going.'

A URL identifies a specific resource on a web server but does not by itself identify the source of a network communication.

Ports identify specific services or applications on a host, not the host's network location - a port must be paired with an IP address to form a full socket.

A MAC address identifies a device only at Layer 2 within a local network segment and is not used to route traffic between different networks.