Imagine you wake one morning in a strange land where everything is written in a language you do not understand. As you venture out, you quickly find you cannot accomplish even basic tasks.
Language is a protocol, and its rules tell us how to interpret what others say. The Internet has a protocol too, and its rules make sure data gets from computer to computer.

Internet Protocol (IP) underlies all communication over the Internet. It is responsible for:

1. Describing an addressing mechanism for Internet computers
2. Breaking data up into manageable pieces and moving them from source to destination

Internet Protocol version 4 (IPv4) became standard in 1981. Today, IP version (IPv6) is gaining acceptance as the next generation IP standard.

When you send data (email, for example), Linux breaks the data into little pieces called packets^[1]. Every packet contains information on where it's going (destination address), where it came from (source address), and a data payload.

Gateways:^[2] Intermediate gateways route the IP packet to its destination host. Once there, the operating system reassembles all the packets into one unit and gives it to the appropriate program.

To connect Red Hat Linux to any TCP/IP-based network, such as the Internet, a private intranet, or a company extranet one must understand the language of protocols. The differences in how you connect have more to do with the network medium you use (that is, LAN router, cable modem) than they do with whether you are connecting to the public Internet or a company's private network (intranet). Connections to the Internet described in this module include a simple dial-up connection from your own Red Hat Linux system. The most popular protocols for making dial-up connections to the Internet are Point-to-Point Protocol (PPP) and Serial Line Internet Protocol (SLIP). This module focuses on PPP and also builds on the procedures which were previously discussed for creating your own Local Area Network (LAN) by teaching you how to connect your LAN to the Internet.
We first provide an overview of the structure of the Internet, including descriptions of domains, routing, and proxy service. It then discusses how to connect your Red Hat Linux system to the Internet using PPP dial-up connections. For those who want to connect a LAN to the Internet, it describes how to use Red Hat Linux as a router and set it up to do IP masquerading (to protect your private LAN addresses). Finally, this module describes how to configure Red Hat Linux as a proxy server, including how to configure client proxy applications such as Chrome and Firefox.

IP is a simple protocol, and thus does not take address all the possible problems in delivering messages. For instance, Internet Protocol can not:

1. Guarantee packet delivery
2. Guarantee packets arrive in the order they were sent
3. Establish a reliable connection between destination and source

Other protocols, which you will learn about in the next few lessons, build on Internet Protocol and make it more reliable.
The next lesson describes an IP address.

[1]Packet: A unit of information, usually composed of two parts: a header with controlling information and a body with actual information.

[2]Gateway:An entrance into another network, responsible for routing packets into its own network or onto a peer network.