RFC 760 (rfc760) - Page 2 of 42


DoD standard Internet Protocol



Alternative Format: Original Text Document




                                                            January 1980
Internet Protocol
Introduction



1.4.  Operation

  The internet protocol implements two basic functions:  addressing and
  fragmentation.

  The internet modules use the addresses carried in the internet header
  to transmit internet datagrams toward their destinations.  The
  selection of a path for transmission is called routing.

  The internet modules use fields in the internet header to fragment and
  reassemble internet datagrams when necessary for transmission through
  "small packet" networks.

  The model of operation is that an internet module resides in each host
  engaged in internet communication and in each gateway that
  interconnects networks.  These modules share common rules for
  interpreting address fields and for fragmenting and assembling
  internet datagrams.  In addition, these modules (especially in
  gateways) may have procedures for making routing decisions and other
  functions.

  The internet protocol treats each internet datagram as an independent
  entity unrelated to any other internet datagram.  There are no
  connections or logical circuits (virtual or otherwise).

  The internet protocol uses four key mechanisms in providing its
  service:  Type of Service, Time to Live, Options, and Header Checksum.

  The Type of Service is used to indicate the quality of the service
  desired; this may be thought of as selecting among Interactive, Bulk,
  or Real Time, for example.  The type of service is an abstract or
  generalized set of parameters which characterize the service choices
  provided in the networks that make up the internet.  This type of
  service indication is to be used by gateways to select the actual
  transmission parameters for a particular network, the network to be
  used for the next hop, or the next gateway when routing an internet
  datagram.

  The Time to Live is an indication of the lifetime of an internet
  datagram.  It is set by the sender of the datagram and reduced at the
  points along the route where it is processed.  If the time to live
  reaches zero before the internet datagram reaches its destination, the
  internet datagram is destroyed.  The time to live can be thought of as
  a self destruct time limit.

  The Options provide for control functions needed or useful in some
  situations but unnecessary for the most common communications.  The