is greater than the length.

        The Overflow (oflw) [4 bits] is the number of IP modules that
        cannot register timestamps due to lack of space.

        The Flag (flg) [4 bits] values are

          0 -- time stamps only, stored in consecutive 32-bit words,

          1 -- each timestamp is preceded with internet address of the
               registering entity,

          3 -- the internet address fields are prespecified.  An IP
               module only registers its timestamp if it matches its own
               address with the next specified internet address.

        The Timestamp is a right-justified, 32-bit timestamp in
        milliseconds since midnight UT.  If the time is not available in
        milliseconds or cannot be provided with respect to midnight UT
        then any time may be inserted as a timestamp provided the high
        order bit of the timestamp field is set to one to indicate the
        use of a non-standard value.

        The originating host must compose this option with a large
        enough timestamp data area to hold all the timestamp information
        expected.  The size of the option does not change due to adding



 

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        timestamps.  The intitial contents of the timestamp data area
        must be zero or internet address/zero pairs.

        If the timestamp data area is already full (the pointer exceeds
        the length) the datagram is forwarded without inserting the
        timestamp, but the overflow count is incremented by one.

        If there is some room but not enough room for a full timestamp
        to be inserted, or the overflow count itself overflows, the
        original datagram is considered to be in error and is discarded.
        In either case an ICMP parameter problem message may be sent to
        the source host [3].

        The timestamp option is not copied upon fragmentation.  It is
        carried in the first fragment.  Appears at most once in a
        datagram.

  Padding:  variable

    The internet header padding is used to ensure that the internet
    header ends on a 32 bit boundary.  The padding is zero.

3.2.  Discussion

  The implementation of a protocol must be robust.  Each implementation
  must expect to interoperate with others created by different
  individuals.  While the goal of this specification is to be explicit
  about the protocol there is the possibility of differing
  interpretations.  In general, an implementation must be conservative
  in its sending behavior, and liberal in its receiving behavior.  That
  is, it must be careful to send well-formed datagrams, but must accept
  any datagram that it can interpret (e.g., not object to technical
  errors where the meaning is still clear).

  The basic internet service is datagram oriented and provides for the
  fragmentation of datagrams at gateways, with reassembly taking place
  at the destination internet protocol module in the destination host.
  Of course, fragmentation and reassembly of datagrams within a network
  or by private agreement between the gateways of a network is also
  allowed since this is transparent to the internet protocols and the
  higher-level protocols.  This transparent type of fragmentation and
  reassembly is termed "network-dependent" (or intranet) fragmentation
  and is not discussed further here.

  Internet addresses distinguish sources and destinations to the host
  level and provide a protocol field as well.  It is assumed that each
  protocol will provide for whatever multiplexing is necessary within a
  host.



 

                                                          September 1981
Internet Protocol
Specification



  Addressing

    To provide for flexibility in assigning address to networks and
    allow for the  large number of small to intermediate sized networks