RFC 2043 (rfc2043) - Page 3 of 7

The PPP SNA Control Protocol (SNACP)

RFC 2043                       PPP SNACP                    October 1996


1.2.  Terminology

   This document frequently uses the following terms:

   datagram  The unit of transmission in the network layer (such as IP).
             A datagram may be encapsulated in one or more packets
             passed to the data link layer.

   frame     The unit of transmission at the data link layer.  A frame
             may include a header and/or a trailer, along with some
             number of units of data.

   packet    The basic unit of encapsulation, which is passed across the
             interface between the network layer and the data link
             layer.  A packet is usually mapped to a frame; the
             exceptions are when data link layer fragmentation is being
             performed, or when multiple packets are incorporated into a
             single frame.

   peer      The other end of the point-to-point link.

   silently discard
             This means the implementation discards the packet without
             further processing.  The implementation SHOULD provide the
             capability of logging the error, including the contents of
             the silently discarded packet, and SHOULD record the event
             in a statistics counter.

   PIU       Path information unit.  A message unit consisting of a
             transmission header (TH) alone, or a TH followed by a basic
             information unit (BIU) or a BIU segment.  PIU is analogous
             to datagram.

   TH        Transmission header.  Control information, optionally
             followed by a basic information unit (BIU) or a BIU
             segment, that is created and used by path control to route
             message units and to control their flow within the network.

   BIU       Basic information unit.  In SNA, the unit of data and
             control information passed between half-sessions.  It
             consists of a request/response header (RH) followed by a
             request/response unit (RU).

   message unit
             In SNA, the unit of data processed by any layer; for
             example, a basic information unit (BIU), a path information
             unit (PIU), or a request/response unit (RU).




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