RFC 894 (rfc894) - Page 1 of 3
Standard for the transmission of IP datagrams over Ethernet networks
Alternative Format: Original Text Document
Network Working Group Charles Hornig
Request for Comments: 894 Symbolics Cambridge Research Center
April 1984
A Standard for the Transmission of IP Datagrams over Ethernet Networks
Status of this Memo
This RFC specifies a standard method of encapsulating Internet
Protocol (IP) [1] datagrams on an Ethernet [2]. This RFC specifies a
standard protocol for the ARPA-Internet community.
Introduction
This memo applies to the Ethernet (10-megabit/second, 48-bit
addresses). The procedure for transmission of IP datagrams on the
Experimental Ethernet (3-megabit/second, 8-bit addresses) is
described in [3].
Frame Format
IP datagrams are transmitted in standard Ethernet frames. The type
field of the Ethernet frame must contain the value hexadecimal 0800.
The data field contains the IP header followed immediately by the IP
data.
The minimum length of the data field of a packet sent over an
Ethernet is 46 octets. If necessary, the data field should be padded
(with octets of zero) to meet the Ethernet minimum frame size. This
padding is not part of the IP packet and is not included in the total
length field of the IP header.
The minimum length of the data field of a packet sent over an
Ethernet is 1500 octets, thus the maximum length of an IP datagram
sent over an Ethernet is 1500 octets. Implementations are encouraged
to support full-length packets. Gateway implementations MUST be
prepared to accept full-length packets and fragment them if
necessary. If a system cannot receive full-length packets, it should
take steps to discourage others from sending them, such as using the
TCP Maximum Segment Size option [4].
Note: Datagrams on the Ethernet may be longer than the general
Internet default maximum packet size of 576 octets. Hosts connected
to an Ethernet should keep this in mind when sending datagrams to
hosts not on the same Ethernet. It may be appropriate to send
smaller datagrams to avoid unnecessary fragmentation at intermediate
gateways. Please see [4] for further information on this point.
Hornig