Transmitting IP traffic over ARCNET networks
RFC 1201
| Document | Type |
RFC - Internet Standard
(February 1991; No errata)
Obsoletes RFC 1051
Also known as STD 46
Was draft-provan-iparcnet (individual)
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|---|---|---|---|
| Last updated | 2013-03-02 | ||
| Stream | Legacy | ||
| Formats | plain text pdf html bibtex | ||
| Stream | Legacy state | (None) | |
| Consensus Boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | RFC 1201 (Internet Standard) | |
| Telechat date | |||
| Responsible AD | (None) | ||
| Send notices to | (None) | ||
Network Working Group D. Provan
Request for Comments: 1201 Novell, Inc.
Obsoletes: RFC 1051 February 1991
Transmitting IP Traffic over ARCNET Networks
Status of this Memo
This memo defines a protocol for the transmission of IP and ARP
packets over the ARCnet Local Area Network. This RFC specifies an
IAB standards track protocol for the Internet community, and requests
discussion and suggestions for improvements. Please refer to the
current edition of the "IAB Official Protocol Standards" for the
standardization state and status of this protocol. Distribution of
this memo is unlimited.
1. Introduction
This memo specifies a method of encapsulating Internet Protocol (IP)
[1] and Address Resolution Protocol (ARP) [2] datagrams for
transmission across ARCNET [3] using the "ARCNET Packet Header
Definition Standard" [4]. This memo offers a replacement for RFC
1051. RFC 1051 uses an ARCNET framing protocol which limits
unfragmented IP packets to 508 octets [5].
2. ARCNET Packet Format
In 1989, Apple Computers, Novell, ACTINET Systems, Standard
Microsystems, and Pure Data Research agreed to use the ARCNET
datalink protocol defined in "ARCNET Packet Header Definition
Standard" [4]. We'll begin with a brief description of that
protocol.
2.1. ARCNET Framing
ARCNET hardware supports two types of frames: short frames, which are
always 256 octets long, and long frames, which are always 512 octets
long. All frames begin with a hardware header and end with the
client's data preceded by a software header. Software places padding
in the middle of the packet between the hardware header and the
software header to make the frame the appropriate fixed length.
Unbeknown to the software, the hardware removes this padding during
transmission.
Short frames can hold from 0 to 249 octets of client data. Long
frames can hold from 253 to 504 octets of client data. To handle
frames with 250, 251, or 252 octets of data, the datalink protocol
Provan [Page 1]
RFC 1201 IP on ARCNET February 1991
introduces a third frame type: the exception frame.
These three frame formats are shown here. Except as noted, each
block represents one octet.
Short Frame Long Frame Exception Frame
+---------------+ +---------------+ +---------------+
| source | | source | | source |
+---------------+ +---------------+ +---------------+
| destination | | destination | | destination |
+---------------+ +---------------+ +---------------+
| offset | | 0 | | 0 |
+---------------+ +---------------+ +---------------+
. unused . | offset | | offset |
. (offset - 3 . +---------------+ +---------------+
. octets) . . unused . . unused .
+---------------+ . (offset - 4 . . (offset - 4 .
| protocol ID | . octets) . . octets) .
+---------------+ +---------------+ +---------------+
| split flag | | protocol ID | | protocol ID |
+---------------+ +---------------+ +---------------+
| sequence | | split flag | | flag: FF hex |
+ number + +---------------+ +---------------+
| (2 octets) | | sequence | | padding: 0xFF |
+---------------+ + number + +---------------+
. . | (2 octets) | | padding: 0xFF |
. client data . +---------------+ +---------------+
. (256 - offset . . . | (protocol ID) |
. - 4 octets) . . . +---------------+
. . . . | split flag |
+---------------+ . . +---------------+
. . | sequence |
. client data . + number +
. (512 - offset . | (2 octets) |
. - 4 octets) . +---------------+
. . . .
. . . client data .
. . . (512 - offset .
. . . - 8 octets) .
. . . .
+---------------+ +---------------+
These packet formats are presented as software would see them
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