The Department of Defense (DoD) Ports, Protocols, and Services Manual (PPSM) is described DoD Instruction 8510.10. The safe use of Internet technologies relies on protections associated with internet ports, protocols and related services. Each node that connects to the internet is assigned a unique identifier as an Internet Protocol Address (IP). Much like a house in a given city is described by the house number, street name,  city/state, and zip code. Software that needs to communicate with services on the internet to a host will use a port number.  A port is like a window or door on a house, with the walls and roof of the house as the boundary defense or firewall for protecting the contents inside. The term protocol is how a process or service is delivered. This would be equivalent to receiving mail or sending mail from or to your house. There is a set of processes to send a letter, such as return to sender address, destination address, placing the envelope in the mailbox after placing a stamp on the letter. The process of sending mail is the mail protocol using the United States Mailing Service. Within an information system Email, as a comparable example, is an application that runs on a local machine, with the email services located at the corporation or through an internet service. A protocol is how the communications are transferred between systems. For email, one of the protocols that are available is the Simple Mail Transfer Protocol (SMTP). The SMTP protocol enables the email service to communicate with the email server via port number 25 for unencrypted, and port 527 for encrypted communications and contains the “to” and “from” addresses. This is just one of many services available for an organization to leverage. Additionally, there are ~65,000 ports available for use on any given network.