RFC 6746
IPv4 Options for the Identifier-Locator Network Protocol (ILNP)
RFC 6746: IPv4 Options for the Identifier-Locator Network Protocol (ILNP) 💖
Okay bestie, this one's an Experimental RFC from the IRTF, published November 2012 🦋. It's written by RJ Atkinson (Consultant) and SN Bhatti (U. St Andrews), and it's a product of the IRTF Routing Research Group. The title block doesn't list anything it obsoletes or updates. It's all about two new IPv4 Options that only ILNPv4 uses. 🎀
Abstract 🌸
So the abstract says this doc defines two new IPv4 Options that are used only with the Identifier-Locator Network Protocol for IPv4 (ILNPv4). ILNP is an experimental, evolutionary upgrade to IP, and this doc is a product of the IRTF Routing Research Group. ✨
Status of This Memo 📝
This document is not an Internet Standards Track specification. It's published for examination, experimental implementation, and evaluation. 🧐
It defines an Experimental Protocol for the Internet community, and it's a product of the Internet Research Task Force (IRTF). The IRTF publishes the results of Internet-related research and development, and those results might not be suitable for deployment. This RFC is just the individual opinion(s) of one or more members of the Routing Research Group of the IRTF. Documents approved for publication by the IRSG are not a candidate for any level of Internet Standard, see Section 2 of RFC 5741. 💅
For the current status, any errata, and how to give feedback, check http://www.rfc-editor.org/info/rfc6746. 🔥
Copyright Notice 💜
Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. 🌈
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, since they describe your rights and restrictions with respect to this document.
This document may not be modified, and derivative works of it may not be created, except to format it for publication as an RFC or to translate it into languages other than English. 🙈
Table of Contents 🗺️
1. Introduction ....................................................2
1.1. Document Roadmap ...........................................3
1.2. Terminology ................................................4
2. IPv4 Options for ILNPv4 .........................................4
2.1. ILNPv4 Packet Format .......................................5
2.2. ILNP Identifier Option for IPv4 ............................7
2.3. ILNP Nonce Option for IPv4 .................................8
3. Security Considerations .........................................8
4. IANA Considerations .............................................9
5. References ......................................................9
5.1. Normative References .......................................9
5.2. Informative References ....................................10
6. Acknowledgements ...............................................111. Introduction 🧚
This doc is part of the ILNP document set, and it got extensive review inside the IRTF Routing RG. ILNP is one of the recommendations the RG Chairs made. Separately, various refereed research papers on ILNP were also published during this decade, so the ideas here got way broader review than just the Routing RG. 👑
Okay, the spicy part: the views in this document were considered controversial by the Routing RG, but the RG still reached a consensus that the document should be published. Honestly, the Routing RG has had remarkably little consensus on anything, so basically all of their outputs are considered controversial. 💀
The Internet research and development community is currently exploring ways to evolve the Internet Architecture to solve a bunch of issues, including (but not limited to) scalability of inter-domain routing [RFC4984]. Other issues are also active concerns right now, like site multihoming, node multihoming, site/subnet mobility, and node mobility. 🌍
There are several classes of evolution being considered. One class is often called "Map and Encapsulate", where traffic would be mapped and then tunnelled through the inter-domain core of the Internet. Another class is sometimes known as "Identifier/Locator Split", and this document is about a proposal in that second class of evolutionary approaches. 🦋
ILNP is a proposal for evolving the Internet Architecture. Its main difference from the current Internet Architecture is that it deprecates the concept of an IP Address, and instead defines two new objects, each with crisp syntax and semantics. The first new object is the Locator, a topology-dependent name for a subnetwork. The other is the Identifier, a topology-independent name for a node. ✨
1.1. Document Roadmap 🗺️
This document describes a new IPv4 Nonce Option, which ILNPv4 nodes use to carry a security nonce. That nonce is there to prevent off-path attacks against ILNP ICMP messages. The doc also defines a new IPv4 Identifier Option that ILNPv4 nodes use. 🔐
The ILNP architecture can have more than one engineering instantiation. For example, you could imagine a "clean-slate" engineering design based on the ILNP architecture. In separate documents, they describe two specific engineering instances of ILNP. The term "ILNPv6" refers precisely to an instance of ILNP that is based upon, and backwards compatible with, IPv6. The term "ILNPv4" refers precisely to an instance of ILNP that is based upon, and backwards compatible with, IPv4. 💜
Lots of engineering aspects are common to both ILNPv4 and ILNPv6, and those are described in [RFC6741]. A full engineering specification for either ILNPv6 or ILNPv4 is beyond the scope of this document. 🎀
If you want details that aren't covered here, go check the other related ILNP documents:
- a) [RFC6740] is the main architectural description of ILNP, including the concept of operations.
- b) [RFC6741] describes engineering and implementation considerations that are common to both ILNPv4 and ILNPv6.
- c) [RFC6742] defines additional DNS resource records that support ILNP.
- d) [RFC6743] defines a new ICMPv6 Locator Update message used by an ILNP node to inform its correspondent nodes of any changes to its set of valid Locators.
- e) [RFC6744] defines a new IPv6 Nonce Destination Option used by ILNPv6 nodes (1) to indicate to ILNP correspondent nodes (by inclusion within the initial packets of an ILNP session) that the node is operating in the ILNP mode, and (2) to prevent off-path attacks against ILNP ICMP messages. This Nonce is used, for example, with all ILNP ICMPv6 Locator Update messages that are exchanged among ILNP correspondent nodes.
- f) [RFC6745] defines a new ICMPv4 Locator Update message used by an ILNP node to inform its correspondent nodes of any changes to its set of valid Locators.
- g) [RFC6747] describes extensions to Address Resolution Protocol (ARP) for use with ILNPv4.
- h) [RFC6748] describes optional engineering and deployment functions for ILNP. These are not required for the operation or use of ILNP and are provided as additional options.
1.2. Terminology 📖
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 [RFC2119]. 🫶
2. IPv4 Options for ILNPv4 🎀
ILNP for IPv4 (ILNPv4) is just a different instantiation of the ILNP architecture, so it keeps the crisp distinction between the Locator and the Identifier. Same as ILNP for IPv6 (ILNPv6): when ILNPv4 is used for a network-layer session, the upper-layer protocols (e.g., TCP/UDP pseudo-header checksum, IPsec Security Association) bind only to the Identifiers, never to the Locators. Also like ILNPv6, only the Locator values are used for routing and forwarding ILNPv4 packets. 🦋
That said, the packet format for IPv4 is different from IPv6, so the engineering details for ILNPv4 are different too. Just as ILNPv6 is carefully engineered to be backwards-compatible with IPv6, ILNPv4 is carefully engineered to be backwards-compatible with IPv4. 💅
Each of these options MUST be copied upon fragmentation. Each of these options is used for control, so it uses Option Class 0. 🔥
Originally, these two options were specified to use separate IP option numbers. However, only one IP Option (decimal 158) has been defined for experimental use with the properties of MUST COPY and CONTROL [RFC4727]. So these two options were reworked to share that same IP Option number (158). To tell the two actual options apart, you examine the unsigned 8-bit field ILNPv4_OPT inside this option. 🧩
It is important for implementers to understand that IP Option 158 is not uniquely allocated to ILNPv4. Other IPv4-related experiments might be using that IP Option value for different IP options having different IP Option formats. ⚠️
2.1. ILNPv4 Packet Format 🎀
Okay so, the Source IP Address in the IPv4 header becomes the Source ILNPv4 Locator value, and the Destination IP Address becomes the Destination ILNPv4 Locator value 💖. Backwards compatibility means ILNPv4 Locators use the same number space as IPv4 routing prefixes, so they're literally the same numbers 🫶.
ILNPv4 uses the same 64-bit Identifier, with the same modified EUI-64 syntax, as ILNPv6 ✨. The IPv4 address fields are much smaller than the IPv6 ones, so ILNPv4 can't squeeze the Identifier values into the fixed part of the IPv4 header 😭. The two obvious options are an IPv4 Option, or an IPv6-style Extension Header placed after the IPv4 header and before the upper-layer protocol (e.g., OSPF, TCP, UDP, SCTP) 🦋.
Here's the tea 🍵. Lots of deployed IPv4 routers from multiple router vendors use forwarding silicon that can parse past IPv4 Options and look at the upper-layer protocol header at wire-speed on reasonably fast (e.g., 1 Gbps or better) interfaces. No existing IPv4-capable forwarding silicon can parse past a new Extension Header for IPv4, though 💀. So, for engineering reasons, ILNPv4 uses a new IPv4 Option to carry the Identifier values. Another new IPv4 Option carries a nonce value, doing the same job for ILNPv4 that the IPv6 Nonce Destination Option [RFC6744] does for ILNPv6 🌸.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time to Live | Protocol | Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Locator (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Locator (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OT=158 | OL=5 | 0x00 |ILNPv4_OPT=0x01|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Source Identifier +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Destination Identifier +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OT=158 | OL=2 | 0x00 |ILNPv4_OPT=0x02|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| top 32 bits of nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| lower 32 bits of nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Figure 1: ILNPv4 Header with ILNP ID Option and ILNP Nonce Option 📸
Notation for Figure 1:
- IHL: Internet Header Length
- OT: Option Type
- OL: Option Length
2.2. ILNP Identifier Option for IPv4 💅
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OT=158 | OL=20 | 0x00 |ILNPv4_OPT=0x01|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Identifier |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Identifier |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Figure 2: ILNP Identifier Option for IPv4 🎀
Notation for Figure 2:
- OT: Option Type
- OL: Option Length
RFC 791, Page 15 says the Option Length is measured in words and counts the Option Type octet, the Option Length octet, and the option data octets 🤓.
The Source Identifier and Destination Identifier are unsigned 64-bit integers. [RFC6741] specifies the syntax, semantics, and generation of ILNP Identifier values. Using the same syntax and semantics for every instantiation of ILNP Identifiers keeps specification and implementation simple, and it also makes translation or transition between ILNPv4 and ILNPv6 easier should that ever be wanted in future ✨.
Main character rule 👑: this IP Option MUST NOT be present in an IPv4 packet unless the packet is part of an ILNPv4 session. ILNPv4 sessions MUST include this option in the first few packets of each ILNPv4 session, and they MAY include it in all packets of the session. It is RECOMMENDED to include this option in all packets of the ILNPv4 session if packet loss is higher than normal 🙈.
2.3. ILNP Nonce Option for IPv4 🌈
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OT=158 | OL=2 | 0x00 |ILNPv4_OPT=0x02|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| top 32 bits of nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| lower 32 bits of nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Figure 3: ILNP Nonce Option for IPv4 🦋
Notation for Figure 3:
- OT: Option Type
- OL: Option Length
This option holds a 64-bit ILNP Nonce. As noted in [RFC6740] and [RFC6741], all ILNP Nonce values are unidirectional 🙌. For example, when TCP is in use, the underlying ILNPv4 session has two different NONCE values: one from Initiator to Responder, and another from Responder to Initiator. The ILNP Nonce gives non-cryptographic protection against off-path attacks (e.g., forged ICMP messages from the remote end of a TCP session) 🛡️.
Each NONCE value MUST be unpredictable (i.e., cryptographically random) 🔐. [RFC4086] has guidance for implementers on generating cryptographically random values.
This IP Option MUST NOT be present in an IPv4 packet unless the packet is part of an ILNPv4 session. ILNPv4 nodes MUST include this option in the first few packets of each ILNP session, MUST include it in all ICMP messages generated by endpoints taking part in an ILNP session, and MAY include it in all packets of an ILNPv4 session 💜.
3. Security Considerations 🔥
Security considerations for the overall ILNP Architecture are described in [RFC6740]. Additional common security considerations are described in [RFC6741]. This section covers the security considerations specific to the ILNPv4 topics discussed in this document 👀.
⚠️ If the ILNP Nonce value is predictable, an off-path attacker might be able to forge data or control packets. This risk is also mitigated by the existing common practice of IP Source Address filtering [RFC2827] [RFC3704].
IP Security for ILNP [RFC6741] [RFC4301] provides cryptographic protection for ILNP data and control packets. The ILNP Nonce Option is required in the circumstances described in Section 3, even if IPsec is also in use. Deployments of ILNPv4 in high-threat environments SHOULD use IPsec for additional risk reduction 🔒.
This option is meant to be used primarily end-to-end between a source node and a destination node. However, unlike IPv6, IPv4 has no method for telling apart options with hop-by-hop behaviour from options with end-to-end behaviour 😤.
[FILTERING] gives a general discussion of potential operational issues with IPv4 options, plus specific advice for handling several particular IPv4 options. Also, lots of deployed modern IP routers (both IPv4 and IPv6) have been explicitly configured to ignore all IP options when forwarding packets not addressed to the router itself, even the "Router Alert" option. Reports say this was done to stop IP options being used as a (Distributed) Denial-of-Service (D)DoS attack vector on backbone routers 🚨.
4. IANA Considerations 🧚
This document makes no request of IANA ✨.
If the IETF ever decides to standardise ILNPv4, then allocating two unique Header Option values to ILNPv4, one for the Identifier option and one for the Nonce option, would make sense 💖.
5. References 📚
5.1. Normative References 💜
- [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
- [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005.
- [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, ICMPv6, UDP, and TCP Headers", RFC 4727, November 2006.
- [RFC6740] Atkinson, R. and S. Bhatti, "Identifier-Locator Network Protocol (ILNP) Architectural Description", RFC 6740, November 2012.
- [RFC6741] Atkinson, R. and S. Bhatti, "Identifier-Locator Network Protocol (ILNP) Engineering and Implementation Considerations", RFC 6741, November 2012.
- [RFC6742] Atkinson, R., Bhatti, S. and S. Rose, "DNS Resource Records for the Identifier-Locator Network Protocol (ILNP)", RFC 6742, November 2012.
- [RFC6745] Atkinson, R. and S. Bhatti, "ICMP Locator Update Message for the Identifier-Locator Network Protocol Version 4 (ILNPv4)", RFC 6745, November 2012.
- [RFC6747] Atkinson, R. and S. Bhatti, "Address Resolution Protocol (ARP) Extension for the Identifier-Locator Network Protocol Version 4 (ILNPv4)", RFC 6747, November 2012.
5.2. Informative References 📚
Okay bestie, these are the extra-credit reads 🦋 Not required, but they're iconic and make the whole thing make more sense 💅
[FILTERING] Gont, F., Atkinson, R., and C. Pignataro,
"Recommendations on filtering of IPv4 packets containing
IPv4 options", Work in Progress, March 2012.
[RFC2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines
For Values In the Internet Protocol and Related Headers",
BCP 37, RFC 2780, March 2000.
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP
Source Address Spoofing", BCP 38, RFC 2827, May 2000.
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for
Multihomed Networks", BCP 84, RFC 3704, March 2004.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC
4086, June 2005.
[RFC4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report
from the IAB Workshop on Routing and Addressing", RFC
4984, September 2007.
[RFC6743] Atkinson, R. and S. Bhatti, "ICMP Locator Update Message
for the Identifier-Locator Network Protocol Version 6
(ICMPv6)", RFC 6743, November 2012.
[RFC6744] Atkinson, R. and S. Bhatti, "IPv6 Nonce Destination
Option for the Identifier-Locator Network Protocol
Version 6 (ILNPv6)", RFC 6744, November 2012.
[RFC6748] Atkinson, R. and S Bhatti, "Optional Advanced Deployment
Scenarios for the Identifier-Locator Network Protocol
(ILNP)", RFC 6748, November 2012.6. Acknowledgements 💖
Okay, the shoutout list 🫶 Steve Blake, Stephane Bortzmeyer, Mohamed Boucadair, Noel Chiappa, Wes George, Steve Hailes, Joel Halpern, Mark Handley, Volker Hilt, Paul Jakma, Dae-Young Kim, Tony Li, Yakov Rehkter, Bruce Simpson, Robin Whittle and John Wroclawski (in alphabetical order) gave review and feedback on earlier versions of this document. Steve Blake gave an especially thorough review of an early version of the entire ILNP document set, which was extremely helpful 🙈 The authors also want to thank the anonymous reviewers of the various ILNP papers for their feedback 🌸
Roy Arends gave expert guidance on technical and procedural aspects of DNS issues 👑
Authors' Addresses 🎀
RJ Atkinson
Consultant
San Jose, CA 95125
USA
EMail: rja.lists@gmail.com
SN Bhatti
School of Computer Science
University of St Andrews
North Haugh, St Andrews
Fife, Scotland
KY16 9SX, UK
EMail: saleem@cs.st-andrews.ac.uk📦 where this page comes from
- ietf: rfc6746 2012-11
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