Standard for the transmission of IP datagrams and ARP packets over ARCNET networks (RFC1051)
Original Publication Date: 1988-Mar-01
Included in the Prior Art Database: 2000-Sep-12
Internet Society Requests For Comment (RFCs)
This RFC specifies a standard method of encapsulating Internet Protocol (IP)  and Address Resolution Protocol (ARP)  datagrams on an ARCNET .
Network Working Group P. Prindeville
Request for Comments: 1051 McGill University
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)  and Address Resolution Protocol (ARP)  datagrams
on an ARCNET .
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.
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 .
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
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 .
The frame format is:
Normal Packet Extended Packet
| ALERT* | | ALERT* |
| SOH (1) | | SOH (1) |
| SID | | SID |
| | | |
+ DID ...