**Definition:**TCP/IP (Transmission Control Protocol/Internet Protocol), also referred to as the Internet Protocol Suite, is the World Wide Web's core communication system that enables every Internet-connected device to communicate with every other such device simultaneously. It is, in essence, a computerized syntax (language) that is installed on every computer, both for public (Internet) and private (intranets and extranets) networks. The development of this protocol has enabled the internet — and as a result, online commerce — to grow quickly.
TCP/IP is a two-layered program: the higher layer (TCP) disassembles message content into small "data packets" that are then transmitted over the Internet to be re-assembled by the receiving computer's TCP back into the message's original form. The lower layer (IP) plays the role of "address manager" and gets each data packet to the correct destination. IP addresses are checked by every computer in a network to ensure messages are forwarded as needed.
TCP/IP runs on the client-server communication model, meaning that the user of a first computer (the client) makes a service request, such as forwarding a Web page, to a second network computer or web hosting provider (the server). TCP/IP also relies on point-to-point communication, meaning that communications move from one host computer to another within a pre-defined network boundary. Finally, TCP/IP is said to be stateless because each request is new and unrelated to all previous requests, making network pathways free to be continuously used by all.
Many higher-level apps that ecommerce businesses need to be familiar with utilize and/or are built on TCP/IP. These apps constitute a higher layer of protocol language and are often packaged along with TCP/IP as a single "suite." Examples include:
HTTP (the Internet's Hyper-text Transfer Protocol)
FTP (the Internet's File Transfer Protocol)
Telnet, which enables logging on computers from remote locations
SMTP (Simple Mail Transfer Protocol)
Accessing the Internet via analog phone modems will involve the use of one of two special protocols: SLIP (Serial Line Internet Protocol) or PPP (Point to Point Protocol). The function of these protocols is to "encapsulate" data-packets in a form that allows them to be sent over dial-up phone connections to the access provider's modem.
UDP (User Data-gram Protocol) is an alternative to TCP that is sometimes used for very specialized purposes. It uses hyper-simple, "connection-less" transmission that requires only a minimal amount of protocol. It is mostly used for low-latency, loss-tolerant connections between online apps.
TCP/IP-related protocols used in the exchange of router data include:
ICMP (Internet Control Message Protocol)
IGP (Interior Gateway Protocol)
EGP (Exterior Gateway Protocol)
BGP (Border Gateway Protocol)