RFC 5350
IANA Considerations for the IPv4 and IPv6 Router Alert Options
RFC 5350: IANA Considerations for the IPv4 and IPv6 Router Alert Options 🎀
Okay bestie, here's the tea on the header 💖 This one's from September 2008 and it's a Standards Track doc, so it's a real protocol spec 💅. The authors are J. Manner from TKK and A. McDonald from Siemens/Roke 🧚. It's an update to RFC 2113 and RFC 3175 ✨, and the header doesn't list anything it obsoletes. It's part of the Network Working Group 🌸
Status of This Memo 📜
Vibe check: this is an Internet standards track protocol for the whole Internet community 🌐 The authors want your discussion and suggestions for making it better 💬 For the current standardization state and status of this protocol, check the current edition of "Internet Official Protocol Standards" (STD 1) 📚 And distribution is unlimited, so share away 🦋
Copyright Notice ©️
Copyright (C) The IETF Trust (2008). 🫶
Abstract 🌸
This doc updates the IANA allocation rules and the registry of IPv4 and IPv6 Router Alert Option Values 💜
Table of Contents 🗂️
1. Introduction ....................................................2
2. Use of the Router Alert Option Value Field ......................2
3. IANA Considerations .............................................4
3.1. IANA Considerations for IPv4 Router Alert Option Values ....4
3.2. IANA Considerations for IPv6 Router Alert Option Values ....5
4. Security Considerations .........................................5
5. Acknowledgements ................................................6
6. References ......................................................6
6.1. Normative References .......................................6
6.2. Informative References .....................................61. Introduction ✨
Okay so the IP Router Alert Option is defined for IPv4 in [RFC2113]. A similar IPv6 option is defined in [RFC2711]. When one of these options is in an IP datagram, it's basically saying the contents of that datagram might be interesting to routers 👀 The Router Alert Option (RAO) gets used by protocols like the Resource Reservation Protocol (RSVP) [RFC2205] and IGMP [RFC3376] 💅
Both the IPv4 and IPv6 options have a two-octet Value field to carry extra info 🎀 Routers can use that info, for example, to figure out whether the packet deserves a closer look 🔍
There can be up to 65536 values for the RAO 🤯 Yet, right now, there's only a registry for IPv6 values. No registry or allocation policies are defined for IPv4 💀
This doc updates the IANA registry for managing IPv4 and IPv6 Router Alert Option Values, and removes one existing IPv6 Router Alert Option Value 🧹
2. Use of the Router Alert Option Value Field 🌈
Main character energy: the IPv4 and IPv6 RAO specs handle their Value fields differently 💅 In [RFC2113], the IPv4 Router Alert Option Value field has the value 0 assigned to "Router shall examine packet". Every other value (1-65535) is reserved. No management mechanism (like an IANA registry) and no allocation policy are provided for the IPv4 RAO values 🙈
The IPv6 Router Alert Option has an IANA-managed registry [IANA-IPv6RAO] with allocations for the Value field 📋
In [RFC3175], the IPv4 Router Alert Option Value is described as a parameter that gives "additional information" to the router when it makes its interception decision. It's not described as a registry managed by IANA 🧐 So this aggregation mechanism uses the Value field to carry the reservation aggregation level. For the IPv6 option, IANA has assigned a set of 32 values to indicate reservation levels. But since other registrations were already made in that registry, these values are from 3-35 (which is actually a set of 33 values) 😭
It would've been nice to use the same values in both the IPv4 and IPv6 registries 🥺 But the initial allocations in [RFC2711] and the aggregation-level allocations in [RFC3175] made that impossible. The table below shows the allocations in the IPv6 registry and the values used in the IPv4 registry. The IPv4 values were deduced from [RFC2113] and [RFC3175], assuming the number of aggregation levels can be limited to 32, like in the IPv6 case. Entries for values 6 to 31 are elided for brevity ✂️
+----------+-------------------------+------------------------------+
| Value | IPv4 RAO Meaning | IPv6 RAO Meaning |
+----------+-------------------------+------------------------------+
| 0 | Router shall examine | Datagram contains a |
| | packet [RFC2113] | Multicast Listener Discovery |
| | [RFC2205] [RFC3376] | message [RFC2711] [RFC2710] |
| | [RFC4286] | [RFC4286] |
| 1 | Aggregated Reservation | Datagram contains RSVP |
| | Nesting Level 1 | message [RFC2711] [RFC2205] |
| | [RFC3175] | |
| 2 | Aggregated Reservation | Datagram contains an Active |
| | Nesting Level 2 | Networks message [RFC2711] |
| | [RFC3175] | [Schwartz2000] |
| 3 | Aggregated Reservation | Aggregated Reservation |
| | Nesting Level 3 | Nesting Level 0 [RFC3175](*) |
| | [RFC3175] | |
| 4 | Aggregated Reservation | Aggregated Reservation |
| | Nesting Level 4 | Nesting Level 1 [RFC3175] |
| | [RFC3175] | |
| 5 | Aggregated Reservation | Aggregated Reservation |
| | Nesting Level 5 | Nesting Level 2 [RFC3175] |
| | [RFC3175] | |
| ... | ... | ... |
| 32 | Aggregated Reservation | Aggregated Reservation |
| | Nesting Level 32 | Nesting Level 29 [RFC3175] |
| | [RFC3175] | |
| 33 | Reserved | Aggregated Reservation |
| | | Nesting Level 30 [RFC3175] |
| 34 | Reserved | Aggregated Reservation |
| | | Nesting Level 31 [RFC3175] |
| 35 | Reserved | Aggregated Reservation |
| | | Nesting Level 32(*) |
| | | [RFC3175] |
| 36-65534 | Reserved | Reserved to IANA for future |
| | | assignment |
| 65535 | Reserved | Reserved [IANA-IPv6RAO] |
+----------+-------------------------+------------------------------+Note (*): The entry for the IPv6 RAO Value of 35 (Aggregated Reservation Nesting Level 32) is marked because of an inconsistency in the text of [RFC3175]. It's consequently reflected in the IANA registry 🧩 In that doc, the values 3-35 (i.e., 33 values) are defined for nesting levels 0-31 (i.e., 32 levels). Value 3 is also a duplicate, because aggregation level 0 means end-to-end signaling, and that already has an IPv6 RAO value "1" assigned 🤦♀️
Also note that nesting levels begin at 1 for IPv4 (described in Section 1.4.9 of [RFC3175]) and at 0 for IPv6 (allocated in Section 6 of [RFC3175]) 🧠
Section 3.2 of this document redefines these so that, for IPv6, value 3 is no longer used and values 4-35 represent levels 1-32. This clears up the inconsistencies above 🎉✨
4. Security Considerations 🔐
okay so bestie, this doc is only about IANA managing the IPv4 and IPv6 Router Alert Option Values registry 📋, so it doesn't bring any new security issues. The ones that matter were already covered in [RFC2113] and [RFC2711] ✨. Lowkey a relief, honestly 🫶
BUT (and this is a big but 😭) like RFC 4727 [RFC4727] explains, production networks don't always support experimental code points in IP option headers 🙈. So before you deploy any experimental RAO value across extended network domains like the public Internet, you need to evaluate the network's support for experimental values really carefully 🧐. Using unsupported experimental code points can seriously disrupt the stable operation of the network hosting your experiment. Literally a huge deal when you're planning an experiment with them 💀
Heads up: experimental RAO values can break things for everyone on the network, not just you. Check support first, always 🚨
If you're using experimental RAO values inside an administratively self-contained network domain, the network admins should make sure each value is used consistently 🎀. That's how you avoid experiments interfering with each other 🦋
If your experimental values are going across multiple administrative domains, the experimenters should assume there's a risk that other experiments are using the same values at the same time 👀. So interference is a real possibility. Pay special attention to any security threats that this interference might create 🔥. Not me saying "be careful" like it's a vibe, it's a whole thing 😭✨
5. Acknowledgements 🫶
Huge thanks to Robert Hancock, Martin Stiemerling, Alan Ford, and Francois Le Faucheur for their helpful comments on this document 💖 The best squad 👑
6. References 📚
6.1. Normative References
[RFC2113] Katz, D., "IP Router Alert Option", RFC 2113,
February 1997.
[RFC2711] Partridge, C. and A. Jackson, "IPv6 Router Alert
Option", RFC 2711, October 1999.
[RFC3175] Baker, F., Iturralde, C., Le Faucheur, F., and B.
Davie, "Aggregation of RSVP for IPv4 and IPv6
Reservations", RFC 3175, September 2001.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP
26, RFC 5226, May 2008.6.2. Informative References
[IANA-IPv6RAO] "IANA Registry for Internet Protocol version 6 (IPv6)
Router Alert Option Values", <http://www.iana.org>.
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S.,
and S. Jamin, "Resource ReSerVation Protocol (RSVP)
-- Version 1 Functional Specification", RFC 2205,
September 1997.
[RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast
Listener Discovery (MLD) for IPv6", RFC 2710,
October 1999.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and
A. Thyagarajan, "Internet Group Management Protocol,
Version 3", RFC 3376, October 2002.
[RFC4286] Haberman, B. and J. Martin, "Multicast Router
Discovery", RFC 4286, December 2005.
[RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6,
ICMPv4, ICMPv6, UDP, and TCP Headers", RFC 4727,
November 2006.
[Schwartz2000] Schwartz, B., Jackson, A., Strayer, W., Zhou, W.,
Rockwell, D., and C. Partridge, "Smart Packets:
Applying Active Networks to Network Management", ACM
Transactions on Computer Systems (TOCS), Volume 18,
Issue 1, February 2000.Authors' Addresses 🎀
Jukka Manner
Department of Communications and Networking (Comnet)
Helsinki University of Technology (TKK)
P.O. Box 3000
Espoo FIN-02015 TKK
Finland
Phone: +358 9 451 2481
EMail: jukka.manner@tkk.fi
Andrew McDonald
Roke Manor Research Ltd (a Siemens company)
Old Salisbury Lane
Romsey, Hampshire SO51 0ZN
United Kingdom
EMail: andrew.mcdonald@roke.co.ukFull Copyright Statement ©
Copyright (C) The IETF Trust (2008). 💜
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- ietf: rfc5350 2008-09
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