IPv6 Router Alert Option for MPLS Operations, Administration, and Maintenance (OAM)
Allocates IPv6 Router Alert value 69 so MPLS ping and traceroute messages can be flagged for routers on IPv6.
Raza, K., Akiya, N., and C. Pignataro, "IPv6 Router Alert Option for MPLS Operations, Administration, and Maintenance (OAM)", RFC 7506, DOI 10.17487/RFC7506, April 2015, <https://www.rfc-editor.org/info/rfc7506>.
@misc{rfc7506,
series = {Request for Comments},
number = 7506,
howpublished = {RFC 7506},
publisher = {RFC Editor},
doi = {10.17487/RFC7506},
url = {https://www.rfc-editor.org/info/rfc7506},
author = {K. Raza and N. Akiya and C. Pignataro},
title = {{IPv6 Router Alert Option for MPLS Operations, Administration, and Maintenance (OAM)}},
pagetotal = 6,
year = 2015,
month = apr,
} RFC text
Contents
Internet Engineering Task Force (IETF) K. Raza
Request for Comments: 7506 Cisco Systems, Inc.
Updates: 4379 N. Akiya
Category: Standards Track Big Switch Networks
ISSN: 2070-1721 C. Pignataro
Cisco Systems, Inc.
April 2015
IPv6 Router Alert Option
for MPLS Operations, Administration, and Maintenance (OAM)
Abstract
RFC 4379 defines the MPLS Label Switched Path (LSP) Ping/Traceroute
mechanism in which the Router Alert Option (RAO) MUST be set in the
IP header of the MPLS Echo Request messages and may conditionally be
set in the IP header of the MPLS Echo Reply messages depending on the
Reply Mode used. While a generic "Router shall examine packet"
Option Value is used for the IPv4 RAO, there is no generic RAO value
defined for IPv6 that can be used. This document allocates a new,
generic IPv6 RAO value that can be used by MPLS Operations,
Administration, and Maintenance (OAM) tools, including the MPLS Echo
Request and MPLS Echo Reply messages for MPLS in IPv6 environments.
Consequently, it updates RFC 4379.
The initial motivation to request an IPv6 RAO value for MPLS OAM
comes from the MPLS LSP Ping/Traceroute. However, this value is
applicable to all MPLS OAM and not limited to MPLS LSP Ping/
Traceroute.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7506.
Copyright Notice
Copyright (c) 2015 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, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Specification of Requirements . . . . . . . . . . . . . . . . 3
3. IPv6 RAO Value for MPLS OAM . . . . . . . . . . . . . . . . . 3
4. Updates to RFC 4379 . . . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
A commonly deployed MPLS OAM tool is specified in [RFC4379],
"Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures",
which is used to diagnose MPLS network data planes. This
specification, often referred to as "MPLS LSP Ping/Traceroute"
[RFC4379], requires the use of the Router Alert Option (RAO) in the
IP header. For example, Section 4.3 of [RFC4379] states that the IP
RAO MUST be set in the IP header of an MPLS Echo Request message.
Similarly, Section 4.5 of [RFC4379] states that the IP RAO MUST be
set in the IP header of an MPLS Echo Reply message if the Reply Mode
in the Echo Request is set to "Reply via an IPv4/IPv6 UDP packet with
Router Alert".
[RFC2113] defines a generic Option Value 0x0 for IPv4 RAO that is
used in LSP Ping and LSP Traceroute for MPLS in IPv4 environments.
This IPv4 RAO value of 0x0 is assigned to "Router shall examine
packet". However, currently there is no generic IPV6 RAO value
defined that can be used in LSP Ping and LSP Traceroute for MPLS in
IPv6 environments. Specifically, [RFC2711] defined the Router Alert
for a general IPv6 purpose but required the Value field in the RAO to
indicate a specific reason for using the RAO. Because there is no
defined value for MPLS LSP Ping/Traceroute use or for general use, it
is not possible for MPLS OAM tools to use the IPv6 Router Alert
mechanism.
As vendors are starting to implement MPLS on the IPv6 control plane
(e.g., [LDP-IPV6]), there is a need to define and allocate such an
Option Value for IPv6 in order to comply with [RFC4379]. This
document defines a new IPv6 RAO value that can be used by MPLS OAM
tools, including the MPLS Echo Request and MPLS Echo Reply messages
for MPLS in IPv6 environments.
This document closes the gap discussed in the third paragraph of
Section 3.4.2 in [RFC7439].
2. Specification of Requirements
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].
3. IPv6 RAO Value for MPLS OAM
This document defines a new Option Value (69) for the IPv6 RAO to
alert transit routers to examine the packet more closely for MPLS OAM
purposes. This Option Value is used by any MPLS OAM application that
requires their packets to be examined by a transit router.
In the scope of this document, this Option Value will be used by the
MPLS Echo Request and MPLS Echo Reply for its IPv6 messages, as is
required by [RFC4379].
4. Updates to RFC 4379
[RFC4379] specifies the use of the RAO in the IP header. Sections
4.3 and 4.5 of [RFC4379] are updated as follows:
For every time in which the "Router Alert IP Option" is used, the
following text is appended:
In case of an IPv4 header, the generic IPv4 RAO value 0x0
[RFC2113] SHOULD be used. In case of an IPv6 header, the IPv6 RAO
value (69) allocated through this document for MPLS OAM MUST be
used.
5. IANA Considerations
This document defines a new value (69) for the IPv6 RAO to alert
transit routers to examine the packet more closely for MPLS OAM
purposes. IANA has assigned a new code point under its "IPv6 Router
Alert Option Values" registry defined by [RFC2711], updated by
[RFC5350], and maintained in [IANA-IPv6-RAO]. The new code point is
as follows:
Value Description Reference
----- ------------------------------- ---------------
69 MPLS OAM RFC 7506
6. Security Considerations
This document introduces no new security concerns in addition to what
have already been captured in [RFC4379] and [RFC6398], the latter of
which expands the security considerations of [RFC2113] and [RFC2711].
IPv6 packets containing the MPLS OAM RAO are encapsulated with an
MPLS header and are not expected to be inspected by every label
switched hop within an MPLS LSP. Consequently, this value of the RAO
will be processed by the appropriate router and is not subject to the
problem of being ignored, as described in Section 2.2 of [RFC7045].
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2711] Partridge, C. and A. Jackson, "IPv6 Router Alert Option",
RFC 2711, October 1999,
<http://www.rfc-editor.org/info/rfc2711>.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006, <http://www.rfc-editor.org/info/rfc4379>.
[RFC5350] Manner, J. and A. McDonald, "IANA Considerations for the
IPv4 and IPv6 Router Alert Options", RFC 5350, September
2008, <http://www.rfc-editor.org/info/rfc5350>.
[RFC6398] Le Faucheur, F., Ed., "IP Router Alert Considerations and
Usage", BCP 168, RFC 6398, October 2011,
<http://www.rfc-editor.org/info/rfc6398>.
7.2. Informative References
[IANA-IPv6-RAO]
IANA, "IPv6 Router Alert Option Values",
<http://www.iana.org/assignments/ipv6-routeralert-values>.
[LDP-IPV6] Asati, R., Pignataro, C., Raza, K., Manral, V., and R.
Papneja, "Updates to LDP for IPv6", Work in Progress,
draft-ietf-mpls-ldp-ipv6-17, February 2015.
[RFC2113] Katz, D., "IP Router Alert Option", RFC 2113, February
1997, <http://www.rfc-editor.org/info/rfc2113>.
[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing
of IPv6 Extension Headers", RFC 7045, December 2013,
<http://www.rfc-editor.org/info/rfc7045>.
[RFC7439] George, W., Ed. and C. Pignataro, Ed., "Gap Analysis for
Operating IPv6-Only MPLS Networks", RFC 7439, January
2015, <http://www.rfc-editor.org/info/rfc7439>.
Acknowledgements
The authors would like to thank George Swallow, Ole Troan, Bob
Hinden, Faisal Iqbal, Mathew Janelle, and Gregory Mirsky for their
useful input.
Authors' Addresses
Kamran Raza
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, ON K2K-3E8
Canada
EMail: skraza@cisco.com
Nobo Akiya
Big Switch Networks
EMail: nobo.akiya.dev@gmail.com
Carlos Pignataro
Cisco Systems, Inc.
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
United States
EMail: cpignata@cisco.com
AI ELI5
On this page
§1Why MPLS OAM Needs an IPv6 Value
A widely used MPLS Operations, Administration, and Maintenance (OAM) tool is the one in RFC 4379, often called MPLS LSP Ping/Traceroute. It requires the Router Alert Option (RAO) in the IP header. For example, the IP RAO MUST be set on an MPLS Echo Request, and on an Echo Reply when the Reply Mode is "Reply via an IPv4/IPv6 UDP packet with Router Alert".
For IPv4, RFC 2113 defines a generic Option Value of 0x0, assigned to "Router shall examine packet". For IPv6, RFC 2711 required the Value field to indicate a specific reason, and no value existed for MPLS LSP Ping/Traceroute or for general use. That made it impossible for MPLS OAM tools to use the IPv6 Router Alert mechanism.
As vendors began to implement MPLS on the IPv6 control plane, a value was needed in order to comply with RFC 4379.
Test messages are supposed to carry a flag that says "routers, look at me." The flag existed for one kind of address but not the other, so the test messages could not follow the rules on the newer kind.
§3The New IPv6 RAO Value
The document defines a new Option Value, 69, for the IPv6 RAO. It alerts transit routers to examine the packet more closely for MPLS OAM purposes. Any MPLS OAM application that needs its packets examined by a transit router can use it.
Within this document, the value is used by the MPLS Echo Request and MPLS Echo Reply for IPv6 messages, as RFC 4379 requires. The abstract adds that the value is applicable to all MPLS OAM and is not limited to LSP Ping/Traceroute.
Number 69 is the new flag. Any test tool for these networks can attach it when it wants routers along the way to take a closer look.
§4Update to RFC 4379
Sections 4.3 and 4.5 of RFC 4379 are updated. Every time the "Router Alert IP Option" is mentioned there, this text is appended: for an IPv4 header, the generic IPv4 RAO value 0x0 SHOULD be used; for an IPv6 header, the IPv6 RAO value (69) allocated through this document for MPLS OAM MUST be used.
So the IPv4 behavior is a recommendation, while the IPv6 behavior is a firm requirement.
The old rulebook now gets one extra sentence: use the old flag on the old addresses, and use flag 69 on the new addresses.
| IP version | RAO value | Requirement |
|---|---|---|
| IPv4 | 0x0 (RFC 2113) | SHOULD |
| IPv6 THIS RFC | 69 (this document) | MUST |
§5The IANA Registry Entry
IANA has assigned a new code point under its "IPv6 Router Alert Option Values" registry, which RFC 2711 defined and RFC 5350 updated. The entry is value 69, description "MPLS OAM", reference RFC 7506.
The official list of flag numbers got a new line saying that 69 means "MPLS test messages."
§6Security Considerations
The document introduces no new security concerns beyond those already captured in RFC 4379 and RFC 6398, the latter of which expands the security considerations of RFC 2113 and RFC 2711.
IPv6 packets with the MPLS OAM RAO are encapsulated with an MPLS header and are not expected to be inspected by every label switched hop within an LSP. The RFC concludes that this value will be processed by the appropriate router and is not subject to the problem of being ignored, as described in Section 2.2 of RFC 7045.
Adding this flag does not open any new doors for trouble. The messages travel wrapped up inside the MPLS network, so only the right routers are expected to read them.