SID Space (5f00::/16) Inter-domain Addressing Recommendations
draft-eknb-srv6ops-interdomain-sidspace-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Erik Kline , Nick Buraglio | ||
| Last updated | 2024-11-05 | ||
| Replaces | draft-ek-srv6ops-sidspace-experiment | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
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| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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draft-eknb-srv6ops-interdomain-sidspace-00
SRv6 Operations E. Kline
Internet-Draft Aalyria Technologies, Inc.
Intended status: Informational N. Buraglio
Expires: 9 May 2025 Energy Sciences Network
5 November 2024
SID Space (5f00::/16) Inter-domain Addressing Recommendations
draft-eknb-srv6ops-interdomain-sidspace-00
Abstract
This specification recommends a specific structured use of the SRv6
SIDs prefix in support of Inter-Domain SRv6 networks. The core of
the proposal is to structure the address space by Autonomous System
Number (ASN).
Use of this proposed structure is entirely voluntary. Voluntary use
of this structure aids SRv6 operations while preserving the ability
to use this prefix across cooperating SRv6 domains, but not across
the general Internet.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://ipvsix.github.io/draft-sidspace-experiment/draft-ek-srv6ops-
sidspace-experiment.html. Status information for this document may
be found at https://datatracker.ietf.org/doc/draft-eknb-srv6ops-
interdomain-sidspace/.
Discussion of this document takes place on the SRv6 Operations
Working Group mailing list (mailto:srv6ops@ietf.org), which is
archived at https://mailarchive.ietf.org/arch/browse/srv6ops/.
Subscribe at https://www.ietf.org/mailman/listinfo/srv6ops/.
Source for this draft and an issue tracker can be found at
https://github.com/ipvsix/draft-sidspace-experiment.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Inter-domain SRv6 SIDs . . . . . . . . . . . . . . . . . . . 3
3. Proposed Structure . . . . . . . . . . . . . . . . . . . . . 3
3.1. Generation of ASN derived SRv6 prefix SID . . . . . . . . 4
3.1.1. SRv6 SID Documentation Prefixes . . . . . . . . . . . 4
3.1.2. SRv6 SID Private Use Prefixes . . . . . . . . . . . . 4
4. Routing and Filtering . . . . . . . . . . . . . . . . . . . . 5
5. Example test case . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
[RFC9602] requested of IANA a dedicated prefix for Segment Routing
over IPv6 [RFC8402] Segment Identifiers (SRv6 SIDs), with the aim of
"improv[ing] security by making it simpler to filter traffic at the
edge of the SR domains." The prefix 5f00::/16 was allocated for this
purpose [IANA-IPv6Special]. No requirements were placed on the use
of this prefix nor any recommendations made for structured use of
this prefix.
This specification recommends a specific structured use of the SRv6
SIDs prefix in support of Inter-Domain SRv6 networks. The core of
the proposal is to structure the address space by Autonomous System
Number (ASN).
Use of this proposed structure is entirely voluntary. Voluntary use
of this structure aids SRv6 operations while preserving the ability
to use this prefix across cooperating SRv6 domains, but not across
the general Internet.
The SID space prefix was allocated to improve ease of filtering.
Where SRv6 traffic using these prefixes may be shared with
cooperating partner networks, this proposal makes it easier to craft
filters that permit only SRv6 traffic from identified ASNs.
As a point of historical interest, this proposal contains echos of
the structure of the original 6bone test allocation [RFC1897].
2. Inter-domain SRv6 SIDs
An inter-domain SRv6 SID, as used in this document, means an SRv6 SID
from the address space used by one SRv6 domain that is advertised to
another SRv6 domain force inclusion an SRv6 Policy used by the second
domain when forwarding policy-specific traffic to the advertising
SRv6 domain.
3. Proposed Structure
The recommendation of this specification is for SRv6 domains to
allocate SIDs from prefixes that are concatenations of the SRv6 SID
prefix (5f00::/16) and an applicable ASN. Assuming 32-bit ASNs, this
yields a /48 per ASN in use within an SRv6 domain, i.e. 5f00:as-
hi16:as-lo16::/48.
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3.1. Generation of ASN derived SRv6 prefix SID
Each unique ASN generates a prefix from the IANA allocation by
converting mutually agreed upon ASNs to hexidecimal, and inserting
this hex into a /48 prefix.
3.1.1. SRv6 SID Documentation Prefixes
Using 16-bit and 32-bit ASNs reserved for documentation purposes
[IANA-ASNs] yields several SRv6 SID prefixes that might be used for
SRv6 documentation purposes. These prefixes presently include ASNs
in the range of 64496-64511 as defined in [RFC5398]:
5f00:0:fbf0::/48
...
5f00:0:fbff::/48
or any /48 prefix between these.
It should be noted that 32-but ASNs do not have a specific range
dedicated for documentation but do have a private use block as
defined in [RFC6996].
3.1.2. SRv6 SID Private Use Prefixes
Using 16-bit and 32-bit ASNs reserved for private use purposes
[IANA-ASNs] and defined by yields several SRv6 SID prefixes for
private use. These prefixes are defined by RFC 6996 and presently
include:
+==========+=======================+
| ASN size | Private Use Range |
+==========+=======================+
| 16-bit | 64512-65534 |
+----------+-----------------------+
| 32-bit | 4200000000-4294967294 |
+----------+-----------------------+
Table 1
yielding:
5f00:0:fc00::/48
...
5f00:0:fffe::/48
and
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5f00:fa56:ea00::/48
...
5f00:ffff:fffe::/48
or any /48 prefix between these, as private use ASN-derived SID
prefixes.
4. Routing and Filtering
As noted in [draft-bdmgct-spring-srv6-security], it is assumed that
each ASN using this SRv6 SID space structure has deployed their
respective SRv6 implementations within a limited domain [RFC8799]
with appropriate filtering at the domain boundaries. Because this is
intended for inter-domain use, the requisite filtering exceptions
must be made between each SRv6 domain to allow for the desired Inter-
Domain communication to occur. Care should be taken to allow only
the desired and necessary communication between each SRv6 domain.
The mechanisms used should be conformant with the given domain's
security policy and may include, but are not limited to:
* routing filters such as BGP prefix-lists, route-maps, route-
policies, or other analogous mechanisms, or
* access control filters at the domain edge
5. Example test case
One possible test case is the exchange of the IPv6 prefix SID between
two autonomous systems with independent management domains. In this
example, AS4294967294 exchanges their SRv6 SID prefix
(5f00:ffff:fffe::/48) with AS4200000000 who announces their ASN
derived SRv6 SID prefix (5f00:fa56:ea00::/48).
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┌─────────────────────────────────┐ ┌──────────────────────────────────┐
│ │ │ │
│ │ │ │
│ eBGP speaker │ │ eBGP speaker │
│ 5f00:ffff:fffe::/48 │ │ 5f00:fa56:ea00::/48 │
│ ┌─────┐ ┌────┐ │ │ ┌────┐ ┌─────┐ │
│ │ ├──────┐ │ ├──┼───────────┼──┤ │ ┌───────┤ │ │
│ │ │ │ │ │ │ │ │ │ │ │ │ │
│ └─────┘ ┌──┴──┐ └─┬──┘ │ │ └──┬─┘ ┌──┴──┐ └─────┘ │
│ │ │ │ │ │ │ │ │ │
│ │ ├───────┘ │ │ └───────┤ │ │
│ └─────┘ │ │ └─────┘ │
│ │ │ │
│ │ │ │
│ │ │ │
│ AS4294967294 │ │ AS4200000000│
└─────────────────────────────────┘ └──────────────────────────────────┘
Within this structure, appropriate and agreed upon policy may be
shared between the partner ASNs. Defining the policy or use cases is
outside of the scope of this document.
6. Security Considerations
This document does not alter the inherent security posture of SRv6
[RFC8402], [RFC8754]. The SID space prefix was allocated to improve
ease of filtering. Where SRv6 traffic using these prefixes may be
shared with cooperating partner networks, this proposal makes it
easier to craft filters that permit only SRv6 traffic from identified
ASNs.
7. IANA Considerations
This document has no IANA actions.
8. References
8.1. Normative References
[IANA-ASNs]
"Autonomous System (AS) Numbers", n.d.,
<https://www.iana.org/assignments/as-numbers/as-
numbers.xhtml>.
[IANA-IPv6Special]
"IANA IPv6 Special-Purpose Address Registry", n.d.,
<https://www.iana.org/assignments/iana-ipv6-special-
registry/iana-ipv6-special-registry.xhtml>.
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[RFC9602] Krishnan, S., "Segment Routing over IPv6 (SRv6) Segment
Identifiers in the IPv6 Addressing Architecture",
RFC 9602, DOI 10.17487/RFC9602, October 2024,
<https://www.rfc-editor.org/rfc/rfc9602>.
8.2. Informative References
[draft-bdmgct-spring-srv6-security]
"SRv6 Security Considerations", n.d.,
<https://datatracker.ietf.org/doc/draft-bdmgct-spring-
srv6-security/>.
[RFC1897] Hinden, R. and J. Postel, "IPv6 Testing Address
Allocation", RFC 1897, DOI 10.17487/RFC1897, January 1996,
<https://www.rfc-editor.org/rfc/rfc1897>.
[RFC5398] Huston, G., "Autonomous System (AS) Number Reservation for
Documentation Use", RFC 5398, DOI 10.17487/RFC5398,
December 2008, <https://www.rfc-editor.org/rfc/rfc5398>.
[RFC6996] Mitchell, J., "Autonomous System (AS) Reservation for
Private Use", BCP 6, RFC 6996, DOI 10.17487/RFC6996, July
2013, <https://www.rfc-editor.org/rfc/rfc6996>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/rfc/rfc8402>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/rfc/rfc8754>.
[RFC8799] Carpenter, B. and B. Liu, "Limited Domains and Internet
Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020,
<https://www.rfc-editor.org/rfc/rfc8799>.
Acknowledgments
TODO acknowledge.
Authors' Addresses
Erik Kline
Aalyria Technologies, Inc.
Email: ek.ietf@gmail.com
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Nick Buraglio
Energy Sciences Network
Email: buraglio@forwardingplane.net
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