Internet DRAFT - draft-mirsky-mpls-bfd-bootstrap-clarify
draft-mirsky-mpls-bfd-bootstrap-clarify
MPLS Working Group G. Mirsky
Internet-Draft Ericsson
Updates: 5884 (if approved) Y. Zhao
Intended status: Standards Track ZTE Corporation
Expires: 12 July 2024 G. Mishra
Verizon Inc.
R. Bonica
Juniper Networks
9 January 2024
Clarifying Use of LSP Ping to Bootstrap BFD over MPLS LSP
draft-mirsky-mpls-bfd-bootstrap-clarify-05
Abstract
This document, if approved, updates RFC 5884 by clarifying procedures
for using MPLS LSP ping to bootstrap Bidirectional Forwarding
Detection (BFD) over MPLS Label Switch Path.
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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This Internet-Draft will expire on 12 July 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Provisions Relating to IETF Documents (https://trustee.ietf.org/
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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. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. Use of Return Mode Field . . . . . . . . . . . . . . . . . . 2
4. Use of BFD Discriminator TLV in LSP Echo Reply . . . . . . . 3
5. Destination IPv6 Address . . . . . . . . . . . . . . . . . . 3
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. Security Considerations . . . . . . . . . . . . . . . . . . . 4
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
9. Normative References . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
[RFC5884] defines how LSP Ping [RFC8029] uses BFD Discriminator TLV
to bootstrap Bidirectional Forwarding Detection (BFD) session over
MPLS Label Switch Path (LSP). Implementation and operational
experiences suggest that two aspects of using LSP ping to bootstrap
BFD session can benefit from clarification. This document updates
[RFC5884] in use of Return Mode field in MPLS LSP echo request
message and use of BFD Discriminator TLV in MPLS LSP echo reply.
2. Requirements Language
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.
3. Use of Return Mode Field
[RFC5884] does not define the value for the Return Mode field
[RFC8029] when LSP ping is used to bootstrap a BFD session of MPLS
LSP. When an LSP echo request is used to detect defects in the MPLS
data plane and verify consistency between the control plane and the
data plane, an echo reply is needed to confirm the correct state and
provide positive acknowledgment. But when an LSP echo request is
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used to bootstrap a BFD session, the positive acknowledgment,
according to[RFC5884], is provided by the egress transmitting BFD
control message. Thus LSP echo reply is not used to bootstrap the
BFD session, and hence the Return Mode field in the echo request
message SHOULD be set to 1 (Do not reply) [RFC8029] when LSP echo
request is used to bootstrap a BFD session. If bootstrapping a BFD
session is combined with the periodic verification of a FEC as
described in [RFC8029], the Return Mode field MAY be set to 2 (Reply
via an IPv4/IPv6 UDP packet). Furthermore, as proposed in
[I-D.kompella-mpls-lspping-norao], the value of the Return Mode field
in the echo request used to bootstrap a BFD session MUST NOT be set
to 3 (Reply via an IPv4/IPv6 UDP packet with Router Alert).
4. Use of BFD Discriminator TLV in LSP Echo Reply
[RFC5884] in section 6 defines that echo reply by the egress LSR to
BFD bootstrapping echo request MAY include BFD Discriminator TLV with
locally assigned discriminator value for the BFD session. But the
[RFC5884] does not define how the ingress LSR may use the returned
value. From a practical point, as discussed in Section 3, the
returned value is not useful since the egress is required to send the
BFD control message right after successfully validating the FEC and
before sending an echo reply message. Secondly, identifying the
corresponding BFD session at ingress without returning its
discriminator presents an unnecessary challenge for the
implementation. Thus the egress LSR SHOULD NOT include BFD
Discriminator TLV if sending an echo reply to BFD bootstrapping echo
request.
5. Destination IPv6 Address
[RFC5884] 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 7 of [RFC5884]
regarding the selection of an IPv6 destination address for a BFD
Control 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.
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* To exercise all paths in an ECMP environment, the entropy other
than the IP destination address SHOULD use the Entropy Label
[RFC6790] to discover multiple alternate paths in an MPLS network.
6. IANA Considerations
This document does not require any action by IANA. This section may
be removed.
7. Security Considerations
This document does not introduce new security aspects but inherits
all security considerations from [RFC5880], [RFC5884], [RFC8029].
8. Acknowledgements
TBA
9. Normative References
[I-D.kompella-mpls-lspping-norao]
Kompella, K., Bonica, R., and G. Mirsky, "Deprecating the
Use of Router Alert in LSP Ping", Work in Progress,
Internet-Draft, draft-kompella-mpls-lspping-norao-02, 10
December 2022, <https://datatracker.ietf.org/doc/html/
draft-kompella-mpls-lspping-norao-02>.
[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>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
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[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"Bidirectional Forwarding Detection (BFD) for MPLS Label
Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
June 2010, <https://www.rfc-editor.org/info/rfc5884>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<https://www.rfc-editor.org/info/rfc6790>.
[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>.
[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
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com
Yanhua Zhao
ZTE Corporation
Email: zhao.yanhua3@zte.com.cn
Gyan Mishra
Verizon Inc.
Email: gyan.s.mishra@verizon.com
Ron Bonica
Juniper Networks
1133 Innovation Way
Sunnyvale, CA 94089
United States
Email: rbonica@juniper.net
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