NETWORKING:packet addressing

network packets must be properly addressed in order to reach their destinations. Several addressing schemes are used in combination:
• MAC (media access control) addresses for use by hardware
• IPv4 and IPv6 network addresses for use by software
• Hostnames for use by people


Hardware (MAC) addressing
Each of a host’s network interfaces usually has one link-layer MAC address that distinguishes it from other machines on the physical network, plus one or more IP addresses that identify the interface on the global Internet. This last part bears repeating: IP addresses identify network interfaces, not machines.

IP addressing

The mapping from IP addresses to hardware addresses is implemented at the link layer of the TCP/IP model

Hostname “addressing”


Ports
IP addresses identify a machine’s network interfaces, but they are not specific enough to address individual processes or services, many of which may be actively using the network at once. TCP and UDP extend IP addresses with a concept known as a port