RFC 963 (rfc963) - Page 2 of 19

Some problems with the specification of the Military Standard Internet Protocol

Alternative Format: Original Text Document




RFC 963                                                    November 1985
Some Problems with MIL-STD IP


2.  Internet Protocol

   The Internet Protocol (IP) is a network layer protocol in the DoD
   protocol hierarchy which provides communication across interconnected
   packet-switched networks in an internetwork environment.  IP provides
   a pure datagram service with no mechanism for reliability, flow
   control, sequencing, etc.  Instead, these features are provided by a
   connection-oriented protocol, DoD Transmission Control Protocol (TCP)
   [MILS83b], which is implemented in the layer above IP.  TCP is
   designed to operate successfully over channels that are inherently
   unreliable, i.e., which can lose, damage, duplicate, and reorder
   packets.

   Over the years, DARPA has supported specifications of several
   versions of IP; the last one appeared in [POSJ81].  A few years ago,
   the Defense Communications Agency decided to standardize IP for use
   in DoD networks.  For this purpose, the DCA supported formal
   specification of this protocol, following the design discussed in
   [POSJ81] and the technique and organization defined in [SDC82].  A
   detailed specification of this protocol, given in [MILS83a], has been
   adopted as the DoD standard for the Internet Protocol.

   The specification of IP state transitions is organized into decision
   tables; the decision functions and action procedures are specified in
   a subset of Ada[1], and may employ a set of machine-specific data
   structures.  Decision tables are supplied for the pairs  as follows: ,
   , and .  To provide an error indication in the case that some
   fragments of a datagram are received but some are missing, a decision
   table is also supplied for the pair .  (The event names are English descriptions and not
   the names employed by [MILS83a].)

3.  Problems with MIL Standard IP

   One of the major functions of IP is the fragmentation of datagrams
   that cannot be transmitted over a subnetwork in one piece, and their
   subsequent reassembly.  The specification has several problems in
   this area.  One of the most significant is the failure to insert the
   last fragment of an incoming datagram; this would cause datagrams to
   be delivered to the upper-level protocol (ULP) with some data
   missing. Another error in this area is that an incorrect value of the
   data length for reassembled datagrams is passed to the ULP, with
   unpredictable consequences.

   As the specification [MILS83a] is now written, these errors are of


Sidhu

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