Standard for the transmission of IP datagrams over IEEE 802 networks
RFC 1042

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Network Working Group                                          J. Postel
Request for Comments:  1042                                  J. Reynolds
                                                                     ISI
Obsoletes: RFC-948                                         February 1988

 A Standard for the Transmission of IP Datagrams over IEEE 802 Networks

Status of this Memo

   This RFC specifies a standard method of encapsulating the Internet
   Protocol (IP) [1] datagrams and Address Resolution Protocol (ARP) [2]
   requests and replies on IEEE 802 Networks.  This RFC specifies a
   protocol standard for the Internet community.  Distribution of this
   memo is unlimited.

Acknowledgment

   This memo would not exist with out the very significant contributions
   of Drew Perkins of Carnegie Mellon University, Jacob Rekhter of the
   T.J. Watson Research Center, IBM Corporation, and Joseph Cimmino of
   the University of Maryland.

Introduction

   The goal of this specification is to allow compatible and
   interoperable implementations for transmitting IP datagrams and ARP
   requests and replies.  To achieve this it may be necessary in a few
   cases to limit the use that IP and ARP make of the capabilities of a
   particular IEEE 802 standard.

   The IEEE 802 specifications define a family of standards for Local
   Area Networks (LANs) that deal 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) [3,4,5] and one Data Link Layer Standard (802.2) [6] 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.

   This memo describes the use of IP and ARP on the three types of
   networks.  At this time, it is not necessary that the use of IP and
   ARP be consistent across all three types of networks, only that it be
   consistent within each type.  This may change in the future as new
   IEEE 802 standards are defined and the existing standards are revised

Postel & Reynolds                                               [Page 1]
RFC 1042            IP and ARP on IEEE 802 Networks        February 1988

   allowing for interoperability at the Data Link Layer.

   It is the goal of this memo to specify enough about the use of IP and
   ARP on each type of network to ensure that:

      (1) all equipment using IP or ARP on 802.3 networks will
      interoperate,

      (2) all equipment using IP or ARP on 802.4 networks will
      interoperate,

      (3) all equipment using IP or ARP on 802.5 networks will
      interoperate.

   Of course, the goal of IP is interoperability between computers
   attached to different networks, when those networks are
   interconnected via an IP gateway [8].  The use of IEEE 802.1
   compatible Transparent Bridges to allow interoperability across
   different networks is not fully described pending completion of that
   standard.

Description

   IEEE 802 networks may be used as IP networks of any class (A, B, or
   C).  These systems use two Link Service Access Point (LSAP) fields of
   the LLC header in much the same way the ARPANET uses the "link"
   field.  Further, there is an extension of the LLC header called the
   Sub-Network Access Protocol (SNAP).

   IP datagrams are sent on IEEE 802 networks encapsulated within the
   802.2 LLC and SNAP data link layers, and the 802.3, 802.4, or 802.5
   physical networks layers.  The SNAP is used with an Organization Code
   indicating that the following 16 bits specify the EtherType code (as
   listed in Assigned Numbers [7]).

   Normally, all communication is performed using 802.2 type 1
   communication.  Consenting systems on the same IEEE 802 network may
   use 802.2 type 2 communication after verifying that it is supported
   by both nodes.  This is accomplished using the 802.2 XID mechanism.
   However, type 1 communication is the recommended method at this time
   and must be supported by all implementations.  The rest of this
   specification assumes the use of type 1 communication.

   The IEEE 802 networks may have 16-bit or 48-bit physical addresses.
   This specification allows the use of either size of address within a
   given IEEE 802 network.

   Note that the 802.3 standard specifies a transmission rate of from 1

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RFC 1042            IP and ARP on IEEE 802 Networks        February 1988

   to 20 megabit/second, the 802.4 standard specifies 1, 5, and 10
   megabit/second, and the 802.5 standard specifies 1 and 4
   megabit/second.  The typical transmission rates used are 10
   megabit/second for 802.3, 10 megabit/second for 802.4, and 4
   megabit/second for 802.5.  However, this specification for the