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Standard for the transmission of IP datagrams and ARP packets over ARCNET networks (RFC1051) Disclosure Number: IPCOM000001858D
Original Publication Date: 1988-Mar-01
Included in the Prior Art Database: 2019-Feb-15
Document File: 4 page(s) / 5K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

P.A. Prindeville: AUTHOR

Related Documents

10.17487/RFC1051: DOI


This memo specifies a standard method of encapsulating Internet Protocol (IP) and Address Resolution Protocol (ARP) datagrams on an ARCNET. This RFC is a standard protocol for the Internet community.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 59% of the total text.

Network Working Group P. Prindeville Request for Comments: 1051 McGill University March 1988

A Standard for the Transmission of IP Datagrams and ARP Packets over ARCNET Networks

Status of this Memo

This RFC specifies a standard protocol for the Internet community. Distribution of this memo is unlimited.


This RFC specifies a standard method of encapsulating Internet Protocol (IP) [1] and Address Resolution Protocol (ARP) [2] datagrams on an ARCNET [3].


The author wishes to express thanks to Robert Craig of the McGill University Computing Centre and Bruce Hughes of Datapoint Corporation for their generous support of facilities and information. I also extend my gratitude to the readers of the PCIP mailing list for their helpful ideas and comments.

Frame Format

IP and ARP datagrams are transmitted in standard ARCNET packets. As required by Datapoint Corporation, the first octet of the data field is reserved for the network layer protocol identification (the "system code" in Datapoint nomenclature), and must contain the value 240 (F0 hex) for IP or 241 (F1 hex) for ARP. The ARP hardware address type for ARCNET is 7 [9].

ARCNET supports packet formats containing 1-253 octets of data (normal format) and 257-508 octets of data (extended format), inclusive of system code. Note that there exists a range of data lengths (254-256) which are ’forbidden’. IP packets within this range should be padded (with octets of zero) to meet the minimum extended packet size of 257 data octets. This padding is not part of the IP packet and is not included in the total length field of the IP header.

Prindeville [Page 1]

RFC 1051 IP and ARP on ARCNET March 1988

On networks where some hosts do not support extended packet format, the IP Maximum Transmission Unit (MTU) should be set to 253, though implementors are encouraged to support the extended packet format mode of operation.

Because the ARCNET maximum packet length is less than the Internet default MTU, implementations are strongly encouraged to support IP level fragmentation and reassembly. Hosts not supporting this should take steps to discourage others from sending fragmented packets, such as using the TCP Maximum Segment Size option [4].

The frame format is:

Normal Packet Extended Packet +----------------+ +----------------+ | ALERT* | | ALERT* | +----------------+ +----------------+ | SOH (1) | | SOH (1) | +----------------+ +----------------+ | SID | | SID | +----------------+ +----------------+ | | | | + DID + + DID + | | | | +----------------+ +----------------+ | COUNT | | NUL (0) | +----------------+ + + | SYSTEM CODE | | COUNT | +----------------+ +----------------+ | | | SYSTEM CODE | : DATA : +----------------+ | | | | +----------------+ : DATA : | | | | + CRC + +----------------+ | | | | +----------------+ + CRC + | | +----------------+

ALERT*: Six mark bits signifying the beginning of a frame. SID: Sender’s node ID. DID: Receipient’s node ID (repeated for reliability). COUN...