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)
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.
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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
Raza, et al. Standards Track [Page 2]
RFC 7506 MPLS OAM IPv6 Router Alert April 2015
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].
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].
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:
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].