Operation Manual

Chapter 2
IP
Introduction
This chapter describes the main features of the Internet Protocol (IP) and
how to configure and operate the AT-RG213 IP interface.
IP protocols are widely used and available on nearly every hosts and PC
systems. They provide a range of services including remote login, file
transfer and Email.
The Internet
The Internet (with a capital “I”) is the name given to the large, worldwide
network of networks based on the original concepts of the ARPAnet. A large
number of government, academic and commercial organisations are
connected to the Internet, and use it to exchange traffic such as Email. The
Internet uses the TCP/IP protocols for all routing. In recent times the term
internet (with a lowercase “i”) has also come to refer to any network (usually
a wide area network) which utilises the Internet Protocol. The remainder of
this chapter will concentrate on the latter definition, i.e. that of a generalised
network which uses IP as the transport protocol.
The basic unit of data sent through an internet is a packet or datagram. An
IP network functions by moving packets between routers and/or hosts. A
packet consists of a header followed by the data (see Figure 4). The header