Internet DRAFT - draft-kompella-mpls-lspping-norao
draft-kompella-mpls-lspping-norao
MPLS WG K. Kompella
Internet-Draft R. Bonica
Updates: 7506, 8029 (if approved) Juniper Networks
Intended status: Standards Track G. Mirsky
Expires: 12 June 2023 Ericsson
9 December 2022
Deprecating the Use of Router Alert in LSP Ping
draft-kompella-mpls-lspping-norao-02
Abstract
LSP ping messages (RFC 8029) are encapsulated in IP headers that
include a Router Alert Option (RAO). The rationale for including an
RAO is questionable. Furthermore, RFC6398 identifies security
vulnerabilities associated with the RAO.
Therefore, this document removes the RAO from LSP ping message
encapsulations. It updates RFCs 7506 and 8029.
This document also recommends the use of an IPv6 loopback address
(:::1/128) and discourages the use of an IPv4 loopback address mapped
to IPv6.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 12 June 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
Kompella, et al. Expires 12 June 2023 [Page 1]
Internet-Draft RAO-less LSP Ping December 2022
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://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 Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Router Alert for LSP Ping (RFC 8029) . . . . . . . . . . . . 3
2.1. Echo Request . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Echo Reply . . . . . . . . . . . . . . . . . . . . . . . 4
3. Update to RFC 7506 . . . . . . . . . . . . . . . . . . . . . 4
4. Update to RFC 8029 . . . . . . . . . . . . . . . . . . . . . 5
5. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
LSP ping [RFC8029] detects data-plane failures in MPLS Label Switched
Paths (LSPs). It can operate in "ping mode" or "traceroute mode".
When operating in ping mode, it verifies end-to-end LSP continuity.
When operating in traceroute mode, it can localize failures to a
particular node along an LSP.
LSP ping defines a probe message, called the "MPLS echo request". It
also defines a response message, called the "MPLS echo reply". Both
messages are encapsulated in UDP and IP. The echo request message is
further encapsulated in an MPLS label stack.
When operating in ping mode, LSP ping sends a single echo request
message, with the MPLS TTL set to a high value (e.g., 255). This
message is intended to reach the egress Label Switching Router (LSR).
When operating in traceroute mode, MPLS ping sends multiple echo
request messages. It manipulates the MPLS TTL so that the first
message expires on the first LSR along the path and subsequent
messages expire on subsequent LSRs.
The IP header that encapsulates an echo request message must include
a Router Alert Option (RAO), while the IP header that encapsulates an
echo reply message may include an RAO. In both cases, the rationale
Kompella, et al. Expires 12 June 2023 [Page 2]
Internet-Draft RAO-less LSP Ping December 2022
for including an RAO is questionable. Furthermore, [RFC6398]
identifies security vulnerabilities associated with the RAO and
recommends against its use outside of controlled environments.
Therefore, this document removes the RAO from both LSP ping message
encapsulations. It updates RFCs 7506 [RFC7506] and 8029.
1.1. 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.
LSP: Label Switched Path
LSR: Label Switching Router
RAO: Router Alert Option
2. Router Alert for LSP Ping (RFC 8029)
2.1. Echo Request
While the MPLS echo request message must traverse every node in the
LSP under test, it must not traverse any other node. Specifically,
the message must not be forwarded beyond the egress Label Switching
Router (LSR).
To achieve this, RFC 8029 proposes the following:
1. When the echo request message is encapsulated in IPv4, the IPv4
destination address must be chosen from the subnet 127/8. When
the echo request message is encapsulated in IPv6, the IPv6
destination address must be chosen from the subnet
0:0:0:0:0:FFFF:7F00:0/104.
2. When the echo request message is encapsulated in IPv4, the IPv4
TTL must be equal to 1. When the echo request message is
encapsulated in IPv6, the IPv6 Hop Limit must be equal to 1.
3. When the echo request message is encapsulated in IPv4, the IPv4
header must include an RAO. When the echo request message is
encapsulated in IPv6, the IPv6 header chain must include a Hop-
by-hop extension header and the Hop-by-hop extension header must
include an RAO.
Kompella, et al. Expires 12 June 2023 [Page 3]
Internet-Draft RAO-less LSP Ping December 2022
Currently, ALL of these are required. However, any one is sufficient
to prevent forwarding the packet beyond the egress LSR.
Therefore, this document changes RFC 8029 in that Requirement 3 is
removed.
The authors are not aware of any implementation that relies on the
RAO to prevent packets from being forwarded beyond the egress LSR.
2.2. Echo Reply
An LSP ping replies to the MPLS echo message with an MPLS echo reply
message. It has four reply modes:
1. Do not reply
2. Reply via an IPv4/IPv6 UDP packet
3. Reply via an IPv4/IPv6 UDP packet with Router Alert
4. Reply via application-level control channel
The rationale for mode 3 is questionable, if not wholly misguided.
According to RFC 8029, "If the normal IP return path is deemed
unreliable, one may use 3 (Reply via an IPv4/IPv6 UDP packet with
Router Alert)."
However, it is not clear that the use of the RAO increases the
reliability of the return path. In fact, one can argue it decreases
the reliability in many instances, due to the additional burden of
processing the RAO. This document changes RGC 8020 in that mode 3
are removed.
The authors are not aware of any implementations of mode 3.
3. Update to RFC 7506
RFC 7506 defines the IPv6 Router Alert Option for MPLS Operations,
Administration, and Management. This document reclassifies RFC 7506
as Historic.
Kompella, et al. Expires 12 June 2023 [Page 4]
Internet-Draft RAO-less LSP Ping December 2022
4. Update to RFC 8029
[RFC8029] requires that the IPv6 Destination Address used in IP/UDP
encapsulation of an echo request packet is selected from the IPv4
loopback address range mapped to IPv6. Such packets do not have the
same behavior as prescribed in[RFC1122] for an IPv4 loopback
addressed packet.
[RFC4291] defines ::1/128 as the single IPv6 loopback address.
Considering that this specification updates section 2.1 of [RFC8029]
regarding the selection of an IPv6 destination address for an echo
request message:
* For IPv6, the IPv6 loopback address ::1/128 SHOULD be used.
* The sender of an echo request MAY select the IPv6 destination
address from the 0:0:0:0:0:FFFF:7F00/104 range.
* To exercise all paths in an ECMP environment, the entropy other
than the IP destination address SHOULD be used.
LSP Ping implementations SHOULD ignore RAO options when they arrive
on incoming echo request and echo reply messages.
5. Backwards Compatibility
LSP Ping implementations SHOULD ignore RAO options when they arrive
on incoming echo request and echo reply messages.
This document requests that the IPv6 RAO value for MPLS OAM (69) in
[IANA-IPV6-RAO] is marked as "Deprecated". It also requests tha that
Reply Mode 3 ("Reply via an IPv4/IPv6 UDP packet with Router Alert")
in [IANA-LSP-PING] is marked as "Deprecated".
We interpret "DEPRECATED" in this context to mean that the deprecated
values should not be used in new implementations, and that deployed
implementations that use these values continue to work seamlessly.
6. IANA Considerations
If this document is approved, mark the IPv6 RAO value of MPLS OAM
(69) in [IANA-IPV6-RAO] as "Deprecated". [RFC8126] offers a formal
description of the word "Deprecated".
Also, mark Reply Mode 3 ("Reply via an IPv4/IPv6 UDP packet with
Router Alert") in [IANA-LSP-PING] as "Deprecated".
Kompella, et al. Expires 12 June 2023 [Page 5]
Internet-Draft RAO-less LSP Ping December 2022
7. Security Considerations
The recommendations this document makes do not compromise security.
8. Normative References
[IANA-IPV6-RAO]
IANA, "IPv6 Router Alert Option Values", n.d.,
<https://www.iana.org/assignments/ipv6-routeralert-
values>.
[IANA-LSP-PING]
IANA, "Multiprotocol Label Switching (MPLS) Label Switched
Paths (LSPs) Ping Parameters", n.d.,
<https://www.iana.org/assignments/mpls-lsp-ping-
parameters/mpls-lsp-ping-parameters.xml>.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989,
<https://www.rfc-editor.org/info/rfc1122>.
[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>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC6398] Le Faucheur, F., Ed., "IP Router Alert Considerations and
Usage", BCP 168, RFC 6398, DOI 10.17487/RFC6398, October
2011, <https://www.rfc-editor.org/info/rfc6398>.
[RFC7506] 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>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.
Kompella, et al. Expires 12 June 2023 [Page 6]
Internet-Draft RAO-less LSP Ping December 2022
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
Authors' Addresses
Kireeti Kompella
Juniper Networks
1133 Innovation Way
Sunnyvale, CA 94089
United States
Email: kireeti.ietf@gmail.com
Ron Bonica
Juniper Networks
1133 Innovation Way
Sunnyvale, CA 94089
United States
Email: rbonica@juniper.net
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com
Kompella, et al. Expires 12 June 2023 [Page 7]
