From 4bfd864f10b68b71482b35c818559068ef8d5797 Mon Sep 17 00:00:00 2001 From: Thomas Voss Date: Wed, 27 Nov 2024 20:54:24 +0100 Subject: doc: Add RFC documents --- doc/rfc/rfc894.txt | 171 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 171 insertions(+) create mode 100644 doc/rfc/rfc894.txt (limited to 'doc/rfc/rfc894.txt') diff --git a/doc/rfc/rfc894.txt b/doc/rfc/rfc894.txt new file mode 100644 index 0000000..d5cd5eb --- /dev/null +++ b/doc/rfc/rfc894.txt @@ -0,0 +1,171 @@ + + +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 [Page 1] + + + +RFC 894 April 1984 + + +Address Mappings + + The mapping of 32-bit Internet addresses to 48-bit Ethernet addresses + can be done several ways. A static table could be used, or a dynamic + discovery procedure could be used. + + Static Table + + Each host could be provided with a table of all other hosts on the + local network with both their Ethernet and Internet addresses. + + Dynamic Discovery + + Mappings between 32-bit Internet addresses and 48-bit Ethernet + addresses could be accomplished through the Address Resolution + Protocol (ARP) [5]. Internet addresses are assigned arbitrarily + on some Internet network. Each host's implementation must know + its own Internet address and respond to Ethernet Address + Resolution packets appropriately. It should also use ARP to + translate Internet addresses to Ethernet addresses when needed. + + Broadcast Address + + The broadcast Internet address (the address on that network with a + host part of all binary ones) should be mapped to the broadcast + Ethernet address (of all binary ones, FF-FF-FF-FF-FF-FF hex). + + The use of the ARP dynamic discovery procedure is strongly + recommended. + +Trailer Formats + + Some versions of Unix 4.2bsd use a different encapsulation method in + order to get better network performance with the VAX virtual memory + architecture. Consenting systems on the same Ethernet may use this + format between themselves. + + No host is required to implement it, and no datagrams in this format + should be sent to any host unless the sender has positive knowledge + that the recipient will be able to interpret them. Details of the + trailer encapsulation may be found in [6]. + + (Note: At the present time Unix 4.2bsd will either always use + trailers or never use them (per interface), depending on a boot-time + option. This is expected to be changed in the future. Unix 4.2bsd + also uses a non-standard Internet broadcast address with a host part + of all zeroes, this may also be changed in the future.) + + + +Hornig [Page 2] + + + +RFC 894 April 1984 + + +Byte Order + + As described in Appendix B of the Internet Protocol + specification [1], the IP datagram is transmitted over the Ethernet + as a series of 8-bit bytes. + +References + + [1] Postel, J., "Internet Protocol", RFC-791, USC/Information + Sciences Institute, September 1981. + + [2] "The Ethernet - A Local Area Network", Version 1.0, Digital + Equipment Corporation, Intel Corporation, Xerox Corporation, + September 1980. + + [3] Postel, J., "A Standard for the Transmission of IP Datagrams + over Experimental Ethernet Networks", RFC-895, USC/Information + Sciences Institute, April 1984. + + [4] Postel, J., "The TCP Maximum Segment Size Option and Related + Topics", RFC-879, USC/Information Sciences Institute, November 1983. + + [5] Plummer, D., "An Ethernet Address Resolution Protocol", RFC-826, + Symbolics Cambridge Research Center, November 1982. + + [6] Leffler, S., and M. Karels, "Trailer Encapsulations", RFC-893, + University of California at Berkeley, April 1984. + + + + + + + + + + + + + + + + + + + + + + + +Hornig [Page 3] + -- cgit v1.2.3