RFC 3791
Survey of IPv4 Addresses in Currently Deployed IETF Routing Area Standards Track and Experimental Documents
Survey of IPv4 Addresses in Currently Deployed IETF Routing Area Standards Track and Experimental Documents 🦋
okay bestie, let's start with the title block 💅 This is RFC 3791, published in June 2004 through the Network Working Group. It's an Informational doc, so it's a survey and not a spec. The authors are C. Olvera from Consulintel and P. Nesser, II from Nesser & Nesser Consulting. The title block doesn't list anything this RFC obsoletes or updates, so it's standing on its own 🌸
Status of this Memo 🎀
This memo is here to give info to the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited ✨
Copyright Notice 🌈
Copyright (C) The Internet Society (2004). The Internet Society holds the copyright on this one 💜
Abstract 🧚
okay so this investigation is trying to document every single place IPv4 addresses are used in the currently deployed IETF Routing Area documented standards. 👀 The whole point is getting from an all-IPv4 Internet to an all-IPv6 Internet, and that's going to take a lot of interim steps. One of those steps is evolving current protocols that depend on IPv4. The hope is that these protocols (and their implementations) get redesigned to be network address independent. If that doesn't happen, they should at least support IPv4 and IPv6 at the same time, which is called dual support 🫶 To make that happen, every Standards doc (Full, Draft, and Proposed) and every Experimental RFC gets surveyed, and any dependencies get written down 💖
Table of Contents 🍓
1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Document Organization . . . . . . . . . . . . . . . . . . . . 2
3. Full Standards. . . . . . . . . . . . . . . . . . . . . . . . 3
4. Draft Standards . . . . . . . . . . . . . . . . . . . . . . . 3
5. Proposed Standards. . . . . . . . . . . . . . . . . . . . . . 3
6. Experimental RFCs . . . . . . . . . . . . . . . . . . . . . . 7
7. Summary of Results. . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9. Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . 12
10. References. . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1. Normative References . . . . . . . . . . . . . . . . . . 13
10.2. Informative References . . . . . . . . . . . . . . . . . 13
11. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . 14
12. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 151. Introduction ✨
so this work is all about documenting every use of IPv4 addresses in the currently deployed IETF Routing Area standards 📚 It also talks through how routing protocols might get updated to support IPv6 addresses. Iconic, right? 🙈
This material used to live in one single document, but that got way too big to manage. So it got split into 7 documents, one for each of the IETF's main areas: Application [2], Internet [3], Operations & Management [4], Routing [this document], Security [5], Sub-IP [6], and Transport [7] 🌸
The general overview, the methodology, and the scope for all 7 documents are in the introduction of this set, which is [1] 🫶
Quick scope check, bestie: this study looks at Full, Draft, and Proposed Standards, plus Experimental RFCs. Informational, BCP, and Historic RFCs are not covered. RFCs that have been obsoleted (by newer versions or by moving through the standards process) are also out of scope 💅
2. Document Organization 🗂️
here's how this doc is laid out 💖
Sections 3, 4, 5, and 6 are the raw analysis of Full Standards, Draft Standards, Proposed Standards, and Experimental RFCs. Each RFC gets its own turn, starting at RFC 1 and going up to (around) RFC 3100. The comments are "raw," which means each RFC is looked at in a vacuum. Problems don't "look ahead" to see if they were already fixed later 🙈
Section 7 is where the analysis happens. It takes everything from Sections 3, 4, 5, and 6, looks at it all together, and links up the problems that got fixed in later RFCs 🔥
3. Full Standards 👑
Full Internet Standards (usually just called "Standards") are fully mature protocol specs that are widely implemented and used all over the Internet. Very established, very main character ✨
3.1. RFC 1722 (STD 57) RIP Version 2 Protocol Applicability Statement
RIPv2 is only meant for IPv4 networks. 💀
3.2. RFC 2328 (STD 54) OSPF Version 2
this RFC defines a protocol for IPv4 routing, and it's super assumptive that addresses are IPv4 in nature 🙄
3.3. RFC 2453 (STD 56) RIP Version 2
RIPv2 is only meant for IPv4 networks. Again, it's giving déjà vu 😭
4. Draft Standards 🌈
Draft Standards are the penultimate standard level in the IETF, so basically one step away from the top 🧚 A protocol can only reach draft standard when there are multiple, independent, interoperable implementations. Draft Standards are usually pretty mature and widely used 💜
4.1. RFC 1771 A Border Gateway Protocol 4 (BGP-4)
this RFC defines a protocol for exchanging IPv4 routing information, and it does not support IPv6 as it's defined. no cap, that's a big gap 🫠
4.2. RFC 1772 Application of the Border Gateway Protocol in the Internet
this one is a discussion of how BGP-4 gets used on the Internet 🌸
4.3. RFC 3392 Capabilities Advertisement with BGP-4
the protocol enhancements have zero IPv4 dependencies, but the base protocol, BGP-4, is IPv4 only. so close, bestie 🥺
5. Proposed Standards 🦋
Proposed Standards are the introductory-level docs. There are no requirements for even a single implementation 🫨 A lot of the time, Proposed ones never get implemented or moved forward in the IETF standards process. So they're often just ideas being shown to the Internet community. Sometimes flaws get exposed, or they're one of many competing solutions to the same problem. In those later cases, there's no discussion here, since it wouldn't help this survey 💅
5.1. RFC 1195 Use of OSI IS-IS for routing in TCP/IP and dual environments
this document specifies a protocol for exchanging IPv4 routing information 🔥
5.2. RFC 1370 Applicability Statement for OSPF
this doc talks about a version of OSPF that's limited to IPv4 🙈
5.3. RFC 1397 Default Route Advertisement In BGP2 and BGP3 Version of The Border Gateway Protocol
BGP2 and BGP3 are both deprecated, so they're not discussed in this document 🪦
5.4. RFC 1478 An Architecture for Inter-Domain Policy Routing
the architecture described here has no IPv4 dependencies. giving clean energy ✨
5.5. RFC 1479 Inter-Domain Policy Routing Protocol Specification: Version 1 (IDPR)
there are no IPv4 dependencies in this protocol 💖
5.6. RFC 1517 Applicability Statement for the Implementation of Classless Inter-Domain Routing (CIDR)
this document deals exclusively with IPv4 addressing issues 🙃
5.7. RFC 1518 An Architecture for IP Address Allocation with CIDR
this document deals exclusively with IPv4 addressing issues. same energy as the last one 🫠
5.8. RFC 1519 Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy
this document deals exclusively with IPv4 addressing issues. three in a row, it's a whole theme 🌈
5.9. RFC 1582 Extensions to RIP to Support Demand Circuits
this protocol extends a protocol that exchanges IPv4 routing information 🧚
5.10. RFC 1584 Multicast Extensions to OSPF
this document defines how IPv4 multicast gets used with an IPv4-only routing protocol 🍓
5.11. RFC 1793 Extending OSPF to Support Demand Circuits
there are no IPv4 dependencies in this protocol, other than the fact that it's a new feature for a routing protocol that only supports IPv4 networks 🤷♀️
5.12. RFC 1997 BGP Communities Attribute
the protocol enhancements have no IPv4 dependencies, but the base protocol, BGP-4, is IPv4 only 🥹
5.13. RFC 2080 RIPng for IPv6
this RFC documents a protocol for exchanging IPv6 routing information, so it's not discussed here 🫡
5.14. RFC 2091 Triggered Extensions to RIP to Support Demand Circuits
this RFC defines an enhancement for an IPv4 routing protocol. even though it has no IPv4 dependencies, it's inherently limited to IPv4 🙃
5.15. RFC 2338 Virtual Router Redundancy Protocol (VRRP)
this protocol is IPv4 specific. there are tons of references to 32-bit IP addresses 💀
5.16. RFC 2370 The OSPF Opaque LSA Option
there are no IPv4 dependencies in this protocol, other than that it's a new feature for a routing protocol that only supports IPv4 networks 🌸
5.17. RFC 2439 BGP Route Flap Damping
the protocol enhancements have no IPv4 dependencies, even though the base protocol, BGP-4, is an IPv4-only routing protocol 🫶
5.18. RFC 2545 Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing
this RFC documents IPv6 routing methods, so it's not discussed in this document 🙅♀️
5.19. RFC 2740 OSPF for IPv6
this document defines an IPv6-specific protocol, so it's not discussed here either 🧚♀️
5.20. RFC 2784 Generic Routing Encapsulation (GRE)
this protocol is only defined for IPv4. the Appendix says:
o IPv6 as Delivery and/or Payload Protocol
This specification describes the intersection of GRE currently
deployed by multiple vendors. IPv6 as delivery and/or payload
protocol is not included.so basically, IPv6 as a delivery or payload protocol isn't part of it 😭
5.21. RFC 2796 BGP Route Reflection - An Alternative to Full Mesh IBGP
the protocol enhancements have no IPv4 dependencies, but the base protocol, BGP-4, is an IPv4-only routing protocol. this spec updates RFC 1966 but doesn't obsolete it 🌈
5.22. RFC 2858 Multiprotocol Extensions for BGP-4
this is the one that says, in its Abstract:
Currently BGP-4 is capable of carrying routing information only for
IPv4. This document defines extensions to BGP-4 to enable it to
carry routing information for multiple Network Layer protocols (e.g.,
IPv6, IPX, etc...). The extensions are backward compatible - a
router that supports the extensions can interoperate with a router
that doesn't support the extensions.so the document isn't examined any further here 🫡
5.23. RFC 2890 Key and Sequence Number Extensions to GRE
there are no IPv4 dependencies in this protocol 💖
5.24. RFC 2894 Router Renumbering for IPv6
this RFC defines an IPv6-only doc, so it's not part of this survey 🧚
5.25. RFC 2918 Route Refresh Capability for BGP-4
the protocol enhancements have no IPv4 dependencies, but the base protocol, BGP-4, is an IPv4-only routing protocol 🥺
5.26. RFC 3065 Autonomous System Confederations for BGP
the protocol enhancements have no IPv4 dependencies, but the base protocol, BGP-4, is an IPv4-only routing protocol 🫠
5.27. RFC 3101 The OSPF Not-So-Stubby Area (NSSA) Option
this document defines an extension to an IPv4 routing protocol 🍓
5.28. RFC 3107 Carrying Label Information in BGP-4
there are no IPv4 dependencies in this protocol ✨
5.29. RFC 3122 Extensions to IPv6 Neighbor Discovery for Inverse Discovery Specification
this is an IPv6-related document, so it's not discussed here 💅
6. Experimental RFCs 🧪
Experimental RFCs usually define protocols that don't have wide-scale implementation or use on the Internet 🌱 They're often proprietary in nature or used in limited arenas. They get documented for the Internet community so that potential interoperability or some other useful scenario can be explored. In a few cases, they're presented as alternatives to the mainstream solution for a known problem 🔬
6.1. RFC 1075 Distance Vector Multicast Routing Protocol (DVMRP) 🦋
okay so this one is all about IPv4 multicast routing. it defines a protocol for it, and that's the whole vibe 💜
6.2. RFC 1383 An Experiment in DNS Based IP Routing 🍓
bestie, this proposal is IPv4 limited 😭 but the idea is cute. the record is built for easy general purpose extensions in the DNS, and its content is just a text string. the RX record holds three fields: a record identifier, a cost indicator, and an IP address. the three strings get separated by a single comma.
here's what an example record looks like 👇
___________________________________________________________________
| domain | type | record | value |
| - | | | |
|*.27.32.192.in-addr.arpa | IP | TXT | RX, 10, 10.0.0.7|
|_________________________|________|__________|___________________|so basically, for all hosts whose IP address starts with the three octets "192.32.27", the IP host "10.0.0.7" can be used as a gateway, and the preference value is 10 🎀
6.3. RFC 1476 RAP: Internet Route Access Protocol 🥀
this one is giving IPv7 routing protocol energy, but the IETF abandoned it as a feasible design. so it's not considered in this document. rip 🕊️
6.4. RFC 1765 OSPF Database Overflow 🌸
there are no IPv4 dependencies in this protocol, other than the fact that it's a new feature for a routing protocol that only supports IPv4 networks. the whole thing is about the way that it works with IPv4 🧚
6.5. RFC 1863 A BGP/IDRP Route Server alternative to a full mesh routing ✨
this protocol is both IPv4 and IPv6 aware, and it needs no changes. iconic behavior, no notes 👑
6.6. RFC 1966 BGP Route Reflection An alternative to full mesh IBGP 🫶
ngl this one's a little complicated. the protocol enhancements have no IPv4 dependencies, but the base protocol, BGP-4, is an IPv4 only routing protocol. also, this specification has been updated by RFC 2796 💅
6.7. RFC 2189 Core Based Trees (CBT version 2) Multicast Routing 🌈
this document specifies a protocol that depends on IPv4 multicast. there are a lot of packet formats defined here that show IPv4 usage, so it's very much an IPv4 situation 🙈
6.8. RFC 2201 Core Based Trees (CBT) Multicast Routing Architecture 🍓
see the previous section for the IPv4 limitation in this protocol. it's the same story, bestie 💖
6.9. RFC 2337 Intra-LIS IP multicast among routers over ATM using Sparse Mode PIM 🦋
this protocol is designed for IPv4 multicast. that's the main character of this one 💅
6.10. RFC 2362 Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification 👑
this protocol is both IPv4 and IPv6 aware, and it needs no changes. slay, honestly 🔥
6.11. RFC 2676 QoS Routing Mechanisms and OSPF Extensions 💜
okay so there are IPv4 dependencies in this protocol. it requires the use of the IPv4 TOS header field 😭
7. Summary of Results ✨
okay here's the tea 🫖 in the initial survey of RFCs, 23 positives were identified out of a total of 46. the breakdown looks like this:
Standards: 3 out of 3 or 100.00%
Draft Standards: 1 out of 3 or 33.33%
Proposed Standards: 13 out of 29 or 44.83%
Experimental RFCs: 6 out of 11 or 54.54%a lot of what was identified doesn't need any action, because it documents outdated and unused protocols. other stuff documents protocols that the appropriate working groups are actively updating 🌸 there are also plenty of standards that should be updated but don't cause any operational impact if they aren't. the remaining instances are documented below. the authors tried to organize the results in a format that makes it easy for other protocol designers to reference them 🧚 the assignment of statements is based entirely on the authors' perceived needs for updates, and it should not be taken as an official statement, so keep that in mind 🫶
7.1. Standards 👑
7.1.1. STD 57 RIP Version 2 Protocol Applicability Statement (RFC 1722) 💖
this problem has been fixed by RFC 2081, RIPng Protocol Applicability Statement ✨
7.1.2. STD 54 OSPF Version 2 (RFC 2328) 🎀
this problem has been fixed by RFC 2740, OSPF for IPv6 🦋
7.1.3. STD 56 RIP Version 2 (RFC 2453) 🌈
this problem has been fixed by RFC 2080, RIPng for IPv6 💅
7.2. Draft Standards 🍓
7.2.1. Border Gateway Protocol 4 (RFC 1771) 🥹
this problem has been fixed in RFC 2858 Multiprotocol Extensions for BGP-4, RFC 2545 Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing, and in [8].
RFC 2858 extends BGP to support multi-protocol extensions, which allows routing information for other address families to be exchanged. RFC 2545 further extends RFC 2858 for full support of exchanging IPv6 routing information, and it additionally clarifies support of the extended BGP-4 protocol using TCP+IPv6 as a transport mechanism. rfc 1771, 2858 & 2545 must be supported in order to provide full IPv6 support, so don't skip any of them 🔥
also, all the BGP extensions analyzed earlier in this memo function without changes with the updated version of BGP-4. that's a whole vibe 🫶
7.3. Proposed Standards 🧚
7.3.1. Use of OSI IS-IS for routing in TCP/IP and dual environments (RFC 1195) 🌸
this problem is being addressed by the IS-IS WG [9] 💜
7.3.2. Applicability Statement for OSPFv2 (RFC 1370) ✨
this problem has been resolved in RFC 2740, OSPF for IPv6 🎀
7.3.3. Applicability of CIDR (RFC 1517) 🦋
the contents of this specification have been treated in various IPv6 addressing architecture RFCs. see RFC 3513 & 3587 🌈
7.3.4. CIDR Architecture (RFC 1518) 💅
the contents of this specification have been treated in various IPv6 addressing architecture RFCs. see RFC 3513 & 3587 🍓
7.3.5. Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy (RFC 1519) 👑
the contents of this specification have been treated in various IPv6 addressing architecture RFCs. see RFC 3513 & 3587 ✨
7.3.6. RIP Extensions for Demand Circuits (RFC 1582) 🥹
this problem has been addressed in RFC 2080, RIPng for IPv6 💖
7.3.7. OSPF Multicast Extensions (RFC 1584) 🦋
this functionality has been covered in RFC 2740, OSPF for IPv6 🫶
7.3.8. OSPF For Demand Circuits (RFC 1793) 🌸
this functionality has been covered in RFC 2740, OSPF for IPv6 🧚
7.3.9. RIP Triggered Extensions for Demand Circuits (RFC 2091) 🎀
this functionality is provided in RFC 2080, RIPng for IPv6 💜
7.3.10. Virtual Router Redundancy Protocol (VRRP)(RFC 2338) 🌈
the problems identified are being addressed by the VRRP WG [10] 💅
7.3.11. OSPF Opaque LSA Option (RFC 2370) 🍓
this problem has been fixed by RFC 2740, OSPF for IPv6. opaque options support is an inbuilt functionality in OSPFv3, so that part's already handled 👑
7.3.12. Generic Routing Encapsulation (GRE)(RFC 2784) ✨
ngl this one's a bit of a mess. even though GRE tunneling over IPv6 has been implemented and used, its use has not been formally specified. clarifications are required 🥺
7.3.13. OSPF NSSA Option (RFC 3101) 💖
this functionality has been covered in RFC 2740, OSPF for IPv6 🦋
7.4. Experimental RFCs 🌈
7.4.1. Distance Vector Multicast Routing Protocol (RFC 1075) 🥀
this protocol is a routing protocol for IPv4 multicast routing. it's no longer in use and doesn't need to be redefined. rest in peace 🕊️
7.4.2. An Experiment in DNS Based IP Routing (RFC 1383) 🍓
this protocol relies on the IPv4 DNS RR, but it's no longer relevant and has never seen much use. no action is necessary 💅
7.4.3. Core Based Trees (CBT version 2) Multicast Routing (RFC 2189) 🌸
this protocol relies on IPv4 IGMP Multicast, and a new protocol standard may be produced. however, the multicast routing protocol has never been in much use and is no longer relevant. no action is necessary 🧚
7.4.4. Core Based Trees (CBT) Multicast Routing Architecture (RFC 2201) 🫶
see the previous section for the limitation in this protocol 💜
7.4.5. Intra-LIS IP multicast among routers over ATM using Sparse Mode PIM (RFC 2337) 🎀
this protocol is designed for IPv4 multicast. however, Intra-LIS IP multicast among routers over ATM is not believed to be relevant anymore. a new mechanism may be defined for IPv6 multicast 🦋
7.4.6. QoS Routing Mechanisms and OSPF Extensions (RFC 2676) 🌈
QoS extensions for OSPF were never used for OSPFv2, and there seems to be little need for them in OSPFv3 💅
however, if necessary, an update to this document could simply define the use of the IPv6 Traffic Class field, since it is defined to be exactly the same as the IPv4 TOS field ✨
8. Security Considerations 🔐
this document examines the IPv6-readiness of routing specification. this does not have security considerations in itself 🙈
9. Acknowledgements 🫶
the original author, Philip J. Nesser II, would like to acknowledge the support of the Internet Society in the research and production of this document 💖
he would also like to thank his partner in all ways, Wendy M. Nesser 🥹
Cesar Olvera would like to thank Pekka Savola for extended guidance and comments on the edition of this document, and Jordi Palet for his support and reviews 🌸
he would further like to thank Andreas Bergstrom, Brian Carpenter, Jeff Haas, Vishwas Manral, Gabriela Medina, Venkata Naidu, Jeff Parker and Curtis Villamizar for valuable feedback 🧚
10. References 📚
10.1. Normative References 🎀
[1] Nesser, II, P. and A. Bergstrom, Editor, "Introduction to the Survey of IPv4 Addresses in Currently Deployed IETF Standards", RFC 3789, June 2004.
[2] Sofia, R. and P. Nesser, II, "Survey of IPv4 Addresses in Currently Deployed IETF Application Area Standards", RFC 3795, June 2004.
[3] Mickles, C. and P. Nesser, II, "Internet Area: Survey of IPv4 Addresses Currently Deployed IETF Standards", RFC 3790, June 2004.
[4] Nesser, II, P. and A. Bergstrom, "Survey of IPv4 addresses in Currently Deployed IETF Operations & Management Area Standards", RFC 3796, June 2004.
[5] Nesser, II, P. and A. Bergstrom. "Survey of IPv4 Addresses in Currently Deployed IETF Security Area Standards", RFC 3792, June 2004.
[6] Nesser, II, P. and A. Bergstrom. "Survey of IPv4 Addresses in Currently Deployed IETF Sub-IP Area Standards", RFC 3793, June 2004.
[7] Nesser, II, P. and A. Bergstrom "Survey of IPv4 Addresses in Currently Deployed IETF Transport Area Standards", RFC 3794, June 2004.
10.2. Informative References 🦋
[8] Chen, E. and J. Yuan, "AS-wide Unique BGP Identifier for BGP-4", Work in Progress, December 2003.
[9] Hopps, C., "Routing IPv6 with IS-IS", Work in Progress, January 2003.
[10] Hinden, R., "Virtual Router Redundancy Protocol for IPv6", Work in Progress, February 2004.
11. Authors' Addresses 🎀
please contact the authors with any questions, comments or suggestions at:
Cesar Olvera Morales
Researcher
Consulintel
San Jose Artesano, 1
28108 - Alcobendas
Madrid, Spain
Phone: +34 91 151 81 99
Fax: +34 91 151 81 98
EMail: cesar.olvera@consulintel.es
Philip J. Nesser II
Principal
Nesser & Nesser Consulting
13501 100th Ave NE, #5202
Kirkland, WA 98034
Phone: +1 425 481 4303
EMail: phil@nesser.com12. Full Copyright Statement 💜
Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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.
Intellectual Property
Okay bestie, so the IETF is lowkey staying neutral here 🫶 It takes no position on whether any IPR or other rights might be claimed for the tech in this doc, or how much (if any) license might be available under those rights. It also doesn't claim to have done its own independent search for those rights. If you want the procedures for rights in RFC docs, check out BCP 78 and BCP 79 📚
Copies of IPR disclosures sent to the IETF Secretariat, any assurances of licenses that might be available, or the results of an attempt to get a general license or permission for implementers or users to use proprietary rights can all be found in the IETF's online IPR repository at http://www.ietf.org/ipr 💜
The IETF also invites anyone interested to flag any copyrights, patents or patent applications, or other proprietary rights that might cover tech needed to implement this standard. Send that info to the IETF at ietf-ipr@ietf.org 🎀
Acknowledgement
Funding for the RFC Editor function is currently provided by the Internet Society 🌈✨
📦 where this page comes from
- ietf: rfc3791 2004-06
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms