RFC 2497

Transmission of IPv6 Packets over ARCnet Networks

📅 published January 1999, from ietf

RFC 2497: Transmission of IPv6 Packets over ARCnet Networks 💖

Okay bestie, let's get into it 🎀 This is RFC 2497, a Standards Track doc from January 1999, written by Ignatios Souvatzis of The NetBSD Project. It's marked as See Also: RFC 1201, and it doesn't list anything it obsoletes or updates, so it's just doing its own thing ✨ It defines how IPv6 packets ride over ARCnet networks, plus how ARCnet link-layer addresses get used in Neighbor Discovery stuff 🦋

Status of This Memo ✨

This doc is an Internet standards track protocol for the Internet community, and it's literally asking for discussion and suggestions for improvements 🫶 For the current standardization state and status, check the "Internet Official Protocol Standards" (STD 1) 📚 Distribution of this memo is unlimited 🌈

Copyright Notice 🔒

1. Introduction 🌸

So this memo gives you a frame format for sending IPv6 [IPV6] packets, plus the way you form IPv6 link-local and statelessly autoconfigured addresses on ARCnet networks 🦋 It also spells out what goes in the Source/Target Link-layer Address option used by Router Solicitation, Router Advertisement, Neighbor Solicitation, Neighbor Advertisement, and Redirect messages from [DISC], whenever those messages travel over ARCnet 🧚

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [KWORD]. 💅

2. Frame Format 🎀

IPv6 packets get link layer fragmented and reassembled according to [PHDS]. A brief but sufficient discussion of this fragmentation method can be found in [ARCIPV4] 🫶

The protocol ID (System Code in ARCnet terminology) assigned to IPv6 is C4 hexadecimal 💖

3. Maximum Transmission Unit 🍓

The maximum IPv6 packet length possible with this encapsulation method is 60480 octets. Like, that's giving huge 😭 but it's also impractical because the worst case transmission time is several seconds. So all ARCnet implementations on a given ARCnet network should agree on a smaller value 🫶

The default MTU for IPv6 [IPV6] packets on an ARCnet is 9072 octets. 🌈

In the presence of a router, this size MAY be changed by a Router Advertisement [DISC] containing an MTU option. 🦋 If a Router Advertisement comes in with an MTU option specifying an MTU larger than 60480, or larger than a manually configured value less than 60480, that MTU option may be logged to system management but MUST be otherwise ignored. Not me ignoring the vibes 💀

If no router is available, the local MTU MUST be left at 9072 or MUST be manually configured to the same different value on all connected stations. ✨

Implementations MAY accept arriving IPv6 datagrams which are larger than their configured maximum transmission unit. They are not required to discard such datagrams. If they can not handle larger datagrams, they MAY log the event to the system administration, but MUST otherwise silently discard them. 🙈

4. Stateless Auto-configuration 🧚

If a node has an EUI-64 that isn't used to form the Interface Identifier for any other interface, it SHOULD use that EUI-64 to form the Interface Identifier for its ARCnet interface 💜 If that EUI-64 is already in use for another interface attached to a different link, it MAY be used for the ARCnet interface as well. 🫶

The Interface Identifier is then formed from the EUI-64 by complementing the "Universal/Local" (U/L) bit, which is the next-to-lowest order bit of the first octet of the EUI-64. 🌸

When a node has no EUI-64 available for forming its ARCnet Interface Identifer, it MUST form that identifier as specified in [AARCH], Appendix A, section "Links with Non-Global Identifier". That is, the 8 bit manually configured ARCnet address is appended to the 56 zero bits. 🎀

For example, for an ARCnet interface with the configured address of 49 hexadecimal, this results in the following identifier: 🍓

   |0              1|1              3|3              4|4              6|
   |0              5|6              1|2              7|8              3|
   +----------------+----------------+----------------+----------------+
   |0000000000000000|0000000000000000|0000000000000000|0000000001001001|
   +----------------+----------------+----------------+----------------+

Note that this results in the universal/local bit set to "0" to indicate local scope. 👑

An IPv6 address prefix used for stateless auto-configuration [ACONF] of an ARCnet interface MUST have a length of 64 bits. 💅

5. Link-Local Addresses 🦋

The IPv6 link-local address [AARCH] for an ARCnet interface is formed by appending the Interface Identifier, as defined above, to the prefix FE80::/64. It's giving structure ✨

    10 bits            54 bits                  64 bits
   +----------+-----------------------+----------------------------+
   |1111111010|         (zeros)       |    Interface Identifier    |
   +----------+-----------------------+----------------------------+

6. Address Mapping -- Unicast 💖

The procedure for mapping IPv6 addresses into ARCnet link-layer addresses is described in [DISC]. When the link layer is ARCnet, the Source/Target link layer Address option has the following form. 🌈

             0                   1
             0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |     Type      |    Length     |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |ARCnet address |               |
            +---------------+              -+
            |                               |
            +-    5 octets of padding      -+
            |                               |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Option fields:

Type: 1 for Source Link-layer address. 2 for Target Link-layer address.
Length: 1 (in units of 8 octets).
ARCnet address: The 8 bit ARCnet address, in canonical bit order.

7. Address Mapping -- Multicast 🧚

As ARCnet only provides 1 multicast address (00 hexadecimal), all IPv6 multicast addresses MUST be mapped to this address. 🔥

8. Security Considerations 💀

⚠️ Serious moment, bestie. The method of deriving Interface Identifiers from ARCnet addresses is intended to preserve local uniqueness when possible. However, there is no protection from duplication through accident or forgery. Zero protection. Be careful out there 😭

9. Acknowledgements 🫶

Big parts of this new version are either based on [ETHIPV6] or on Matt Crawford's review of an earlier version. Thank you, Matt 💜

10. References 📚

   [AARCH]   Hinden, R. and S. Deering, "IP Version 6 Addressing
             Architecture", RFC 2373, July 1998.

   [ACONF]   Thomson, S. and T. Narten, "IPv6 Stateless Address
             Autoconfiguration", RFC 2462, December 1998.

   [ARCIPV4] Provan, D., "Transmitting IP Traffic over ARCNET Networks",
             RFC1201, Novell, Inc., February 1991.

   [DISC]    Narten, T., Nordmark, E. and W. Simpson, "Neighbor
             Discovery for IP Version 6 (IPv6)", RFC 2461, December
             1998.

   [ETHIPV6] Crawford, M., "Transmission of IPv6 Packets over Ethernet
             Networks", RFC 2464, December 1998.

   [EUI64]   "64-Bit Global Identifier Format Tutorial", http://stan�
             dards.ieee.org/db/oui/tutorials/EUI64.html.

   [IPV6]    Deering, S. and R. Hinden, "Internet Protocol, Version 6
             (IPv6) Specification", RFC 2460, December 1998.

   [KWORD]   Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [PHDS]    Novell, Inc., "ARCNET Packet Header Definition Standard",
             Novell Part Number 100-00721-001, November 1989.

11. Author's Address 🌷

   Ignatios Souvatzis
   The NetBSD Project
   Stationenweg 29
   D-53332 Bornheim
   Germany

   Phone (work): +49 (228) 734316
   EMail: is@netbsd.org

12. Full Copyright Statement 💅

This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. 🔒

The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. ♾️

This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 👑

📦 where this page comes from

ietf: rfc2497 1999-01
💖 girlified by claude-haiku-5-5 on 2026-10-17: a language model's rewrite of the original, under its terms