RFC 948 (rfc948) - Page 2 of 6

Two methods for the transmission of IP datagrams over IEEE 802

Network Working Group                                        Ira Winston
Request for Comments: 948                     University of Pennsylvania
                                                               June 1985

         TWO METHODS FOR THE TRANSMISSION OF IP DATAGRAMS OVER
                          IEEE 802.3 NETWORKS


Status of this Memo

   This memo describes two methods of encapsulating Internet
   Protocol (IP) [1] datagrams on an IEEE 802.3 network [2].  This RFC
   suggests a proposed protocol for the ARPA-Internet community, and
   requests discussion and suggestions for improvements.  Distribution
   of this memo is unlimited.

Introduction

   The IEEE 802 project has defined a family of standards for Local Area
   Networks (LANs) that deals with the Physical and Data Link Layers as
   defined by the ISO Open System Interconnection Reference Model
   (ISO/OSI).  Several Physical Layer standards (802.3, 802.4, and
   802.5) [2, 3, 4] and one Data Link Layer Standard (802.2) [5] have
   been defined.  The IEEE Physical Layer standards specify the ISO/OSI
   Physical Layer and the Media Access Control Sublayer of the ISO/OSI
   Data Link Layer.  The 802.2 Data Link Layer standard specifies the
   Logical Link Control Sublayer of the ISO/OSI Data Link Layer.

   The 802.3 standard is based on the Ethernet Version 2.0 standard [6].
   The Ethernet Physical Layer and the 802.3 Physical Layer are
   compatible for all practical purposes however, the Ethernet Data Link
   Layer and the 802.3/802.2 Data Link Layer are incompatible.

   There are many existing Ethernet network installations that transmit
   IP datagrams using the Ethernet compatible standard described in [7].
   IEEE 802.3 Physical Layer compatible connections can be added to
   these networks using an an Ethernet Data Link Layer compatible method
   for transmitting IP datagrams without violating the 802.3 standard.
   Alternatively, an 802.2/802.3 Data Link Layer compatible method for
   transmitting IP datagrams can be used.

Ethernet Compatible Method

   IEEE 802.3 networks must use 48-bit physical addresses and 10
   megabit/second bandwidth in order to be Ethernet compatible.

   The IEEE 802.3 packet header is identical to Ethernet packet header
   except for the meaning assigned to one of the fields in the header.
   In an Ethernet packet header this field is used as a protocol type
   field and in an 802.3 packet header the field is used as a length
   field.  The maximum allowed length field value on a 10 megabit/second


Winston