Other Protocols and Functionalities

Below you will find a list of other “famous” TCP/IP-related protocols and functionalities that you may hear about:

  • NAT (Network Address Translation): Theoretically each computer connected to the Internet would require a valid “public” IP address. NAT allows a local network to use a single “public” IP address. For example, when you connect your home or office network to the Internet using a broadband router, the router will use the single IP address assigned by your ISP, while your computers will use IP addresses that are valid only inside your network (the so-called “magic IP addresses”, usually inside the 192.168.x.x range). From the Internet standpoint, all computers from your network are using the same IP address. So to send data to one of your computers, the source computer will use the router IP address and when this datagram arrives at the router, it will replace its IP address with the IP address that the target computer is using, which is valid only inside your network. This technique is called NAT.

  • IGMP (Internet Group Management Protocol): While sending the same datagram to all computers on a network is called broadcasting, sending the same datagram for a group of computers is called multicasting. On TCP/IP multicasting can be done even if computers are located in different networks. These groups are managed using IGMP control messages. IGMP uses IP protocol, working at the Internet layer.

  • SNMP (Simple Network Management Protocol): Protocol used for monitoring hardware devices attached to TCP/IP networks that implement this protocol. SNMP is an Application layer protocol using UDP on ports 161 and 162.

  • Finger: This is an Application layer protocol using TCP on port 79 used to discover information about a given user on a server. Since having access to personal information of all your users is really a bad idea, this service is almost always disabled.


Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.