Internet DRAFT - draft-hui-stub-router-ra-flag
draft-hui-stub-router-ra-flag
Internet Engineering Task Force J. Hui
Internet-Draft Google LLC
Intended status: Standards Track 27 February 2023
Expires: 31 August 2023
Stub Router Flag in ICMPv6 Router Advertisement Messages
draft-hui-stub-router-ra-flag-01
Abstract
This document defines a new Stub Router flag in the Router
Advertisement message to distinguish configuration information sent
by stub routers from infrastructure routers. For example, the Stub
Router flag allows stub routers to easily identify when an
infrastructure router is advertising a usable IPv6 prefix, triggering
the stub router to not advertise its own routable prefix.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 31 August 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Stub Router Flag . . . . . . . . . . . . . . . . . . . . . . 3
4. Router Advertisement Transmission . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
6. Security Considerations . . . . . . . . . . . . . . . . . . . 3
7. Normative References . . . . . . . . . . . . . . . . . . . . 3
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
A stub router provides IP connectivity between a stub network and an
infrastructure network. A common stub router example is a device
that attaches a 6LoWPAN-based network to a home network.
To support IPv6 reachability between infrastructure network devices
and stub network devices, routable IPv6 addresses must be configured
on both the infrastructure and stub networks. Routers on the
infrastructure network may configure routable IPv6 prefixes using
Router Advertisements (RAs) containing Prefix Information Options
(PIOs) [RFC4861].
In cases where the infrastructure network does not provide routable
IPv6 address configuration, the stub router is responsible for
configuring routable IPv6 addresses on the infrastructure network.
If a stub router determines that routable IPv6 addresses are not
available on the infrastructure link, it will locally generate a
Unique Local Address (ULA) Prefix [RFC4193] and begin advertising
that via a PIO contained in RA messages.
Both infrastructure routers and stub routers may advertise routable
IPv6 prefixes in the same way (via RAs containing PIOs). To
distinguish between an infrastructure router and a stub router, this
document defines a new Stub Router flag in the RA message. The Stub
Router flag allows stub routers to easily identify when an
infrastructure router is advertising a routable IPv6 prefix,
triggering the stub router to stop advertising its ULA prefix.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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3. Stub Router Flag
This document defines a new "Stub Router" flag as flag bit 8 in the
Router Advertisement flags field. Setting the Stub Router flag
requires use of the RA Flags Extension Option [RFC5175] to encode the
flag.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |S| Bit fields available ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... for assignment |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Router Advertisement Expanded Flags Option
4. Router Advertisement Transmission
A stub router that is not explicitly configured as part of the
infrastructure network MUST set the Stub Router flag in outgoing RA
messages.
How and when a stub router includes PIOs in outgoing RAs is specified
in [I-D.ietf-snac-simple].
5. IANA Considerations
IANA is requested to allocate a flag from the "IPv6 ND Router
Advertisement flags" registry of [RFC5175], as specified below:
+---------------+----------------------+---------------+
| RA Option Bit | Description | Reference |
+---------------+----------------------+---------------+
| 8 (suggested) | S - Stub Router Flag | This Document |
+---------------+----------------------+---------------+
Table 1
Note that RA Option Bit 8 requires use of the RA Flags Extension
Option [RFC5175] to encode the flag.
6. Security Considerations
This protocol shares the security issues of NDP that are documented
in the "Security Considerations" section of [RFC4861].
7. Normative References
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[I-D.ietf-snac-simple]
Lemon, T., "Automatically Connecting Stub Networks to
Unmanaged Infrastructure", Work in Progress, Internet-
Draft, draft-ietf-snac-simple-00, 13 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-snac-
simple-00>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
<https://www.rfc-editor.org/info/rfc4193>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>.
[RFC5175] Haberman, B., Ed. and R. Hinden, "IPv6 Router
Advertisement Flags Option", RFC 5175,
DOI 10.17487/RFC5175, March 2008,
<https://www.rfc-editor.org/info/rfc5175>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Author's Address
Jonathan Hui
Google LLC
1600 Amphitheatre Parkway
Mountain View, California 940432
United States of America
Email: jonhui@google.com
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