< draft-ietf-mpls-bfd-directed-14.txt   draft-ietf-mpls-bfd-directed-15.txt >
MPLS Working Group G. Mirsky MPLS Working Group G. Mirsky
Internet-Draft ZTE Internet-Draft ZTE
Intended status: Standards Track J. Tantsura Intended status: Standards Track J. Tantsura
Expires: December 24, 2020 Nuage Networks Expires: February 5, 2021 Nuage Networks
I. Varlashkin I. Varlashkin
Google Google
M. Chen M. Chen
Huawei Huawei
June 22, 2020 August 4, 2020
Bidirectional Forwarding Detection (BFD) Directed Return Path Bidirectional Forwarding Detection (BFD) Directed Return Path for MPLS
draft-ietf-mpls-bfd-directed-14 Label Switched Paths (LSPs)
draft-ietf-mpls-bfd-directed-15
Abstract Abstract
Bidirectional Forwarding Detection (BFD) is expected to be able to Bidirectional Forwarding Detection (BFD) is expected to be able to
monitor a wide variety of encapsulations of paths between systems. monitor a wide variety of encapsulations of paths between systems.
When a BFD session monitors an explicitly routed unidirectional path When a BFD session monitors an explicitly routed unidirectional path
there may be a need to direct egress BFD peer to use a specific path there may be a need to direct egress BFD peer to use a specific path
for the reverse direction of the BFD session. for the reverse direction of the BFD session.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 24, 2020. This Internet-Draft will expire on February 5, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Requirements Language . . . . . . . . . . . . . . . . 3 1.1.1. Requirements Language . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
3. Control of the Reverse BFD Path . . . . . . . . . . . . . . . 3 3. Control of the Reverse BFD Path . . . . . . . . . . . . . . . 3
3.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . . . 3 3.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . . . 3
3.2. Return Codes . . . . . . . . . . . . . . . . . . . . . . 5 3.2. Return Codes . . . . . . . . . . . . . . . . . . . . . . 5
4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 5 4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 5
5. Operational Considerations . . . . . . . . . . . . . . . . . 5 5. Operational Considerations . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . . . 6 6.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . . . 6
6.2. Return Code . . . . . . . . . . . . . . . . . . . . . . . 6 6.2. Return Code . . . . . . . . . . . . . . . . . . . . . . . 7
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 7 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Normative References . . . . . . . . . . . . . . . . . . . . 8 9. Normative References . . . . . . . . . . . . . . . . . . . . 8
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 9 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
[RFC5880], [RFC5881], and [RFC5883] established the BFD protocol for [RFC5880], [RFC5881], and [RFC5883] established the BFD protocol for
IP networks. [RFC5884] and [RFC7726] set rules for using BFD IP networks. [RFC5884] and [RFC7726] set rules for using BFD
asynchronous mode over IP/MPLS LSPs. These standards do not define asynchronous mode over IP/MPLS LSPs, while not defining means to
means to control the path selection at the egress BFD peer to send control the path an egress BFD system uses to send BFD control
BFD control packets towards the ingress BFD system. packets towards the ingress BFD system.
For the case when BFD is used to detect defects of the traffic For the case when BFD is used to detect defects of the traffic
engineered LSP the path the BFD control packets transmitted by the engineered LSP the path the BFD control packets transmitted by the
egress BFD system toward the ingress may be disjoint from the LSP in egress BFD system toward the ingress may be disjoint from the LSP in
the forward direction. The fact that BFD control packets are not the forward direction. The fact that BFD control packets are not
guaranteed to follow the same links and nodes in both forward and guaranteed to follow the same links and nodes in both forward and
reverse directions may be one of the factors contributing to reverse directions may be one of the factors contributing to
producing false positive defect notifications, i.e., false alarms, at producing false positive defect notifications, i.e., false alarms, at
the ingress BFD peer. Ensuring that both directions of the BFD the ingress BFD peer. Ensuring that both directions of the BFD
session use co-routed paths may, in some environments, improve the session use co-routed paths may, in some environments, improve the
determinism of the failure detection and localization. determinism of the failure detection and localization.
This document defines the BFD Reverse Path TLV as an extension to LSP This document defines the BFD Reverse Path TLV as an extension to LSP
Ping [RFC8029] and proposes that it is to be used to instruct the Ping [RFC8029] and proposes that it is to be used to instruct the
egress BFD peer to use an explicit path for its BFD control packets egress BFD system to use an explicit path for its BFD control packets
associated with a particular BFD session. The TLV will be allocated associated with a particular BFD session. The TLV will be allocated
from the TLV and sub-TLV registry defined in [RFC8029]. As a special from the TLV and sub-TLV registry defined in [RFC8029]. As a special
case, forward and reverse directions of the BFD session can form a case, forward and reverse directions of the BFD session can form a
bi-directional co-routed associated channel. bi-directional co-routed associated channel.
1.1. Conventions used in this document 1.1. Conventions used in this document
1.1.1. Requirements Language 1.1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Problem Statement 2. Problem Statement
When BFD is used to monitor explicitly routed unidirectional path, When BFD is used to monitor explicitly routed unidirectional path,
e.g., MPLS-TE LSP, BFD control packets in forward direction would be e.g., MPLS-TE LSP, BFD control packets in forward direction would be
in-band using the mechanism defined in [RFC5884]. But the reverse in-band using the mechanism defined in [RFC5884]. But the reverse
direction of the BFD session would follow the shortest path route and direction of the BFD session would follow the shortest path route and
that might lead to the problem in detecting failures on an explicit that might lead to the problem in detecting failures on an explicit
unidirectional path as described below: unidirectional path, as described below:
o detection by an ingress node of a failure on the reverse path may o detection by an ingress node of a failure on the reverse path may
not be unambiguously interpreted as the failure of the path in the not be unambiguously interpreted as the failure of the path in the
forward direction. forward direction.
To address this scenario, the egress BFD peer would be instructed to To address this scenario, the egress BFD peer would be instructed to
use a specific path for BFD control packets. use a specific path for BFD control packets.
3. Control of the Reverse BFD Path 3. Control of the Reverse BFD Path
To bootstrap a BFD session over an MPLS LSP, LSP ping, defined in To bootstrap a BFD session over an MPLS LSP, LSP ping, defined in
[RFC8029], MUST be used with BFD Discriminator TLV [RFC5884]. This [RFC8029], MUST be used with BFD Discriminator TLV [RFC5884]. This
document defines a new TLV, BFD Reverse Path TLV, that MUST contain a document defines a new TLV, BFD Reverse Path TLV, that MAY contain
single sub-TLV that can be used to carry information about the none, one or more sub-TLVs that can be used to carry information
reverse path for the BFD session that is specified by the value in about the reverse path for the BFD session that is specified by the
BFD Discriminator TLV. value in BFD Discriminator TLV.
3.1. BFD Reverse Path TLV 3.1. BFD Reverse Path TLV
The BFD Reverse Path TLV is an optional TLV within the LSP ping The BFD Reverse Path TLV is an optional TLV within the LSP ping
[RFC8029]. However, if used, the BFD Discriminator TLV MUST be [RFC8029]. However, if used, the BFD Discriminator TLV MUST be
included in an Echo Request message as well. If the BFD included in an Echo Request message as well. If the BFD
Discriminator TLV is not present when the BFD Reverse Path TLV is Discriminator TLV is not present when the BFD Reverse Path TLV is
included; then it MUST be treated as malformed Echo Request, as included; then it MUST be treated as malformed Echo Request, as
described in [RFC8029]. described in [RFC8029].
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BFD Reverse Path TLV Figure 1: BFD Reverse Path TLV
BFD Reverse Path TLV Type is two octets in length and has a value of BFD Reverse Path TLV Type is two octets in length and has a value of
TBD1 (to be assigned by IANA as requested in Section 6). TBD1 (to be assigned by IANA as requested in Section 6).
Length field is two octets long and defines the length in octets of Length field is two octets long and defines the length in octets of
the Reverse Path field. the Reverse Path field.
Reverse Path field contains a sub-TLV. Any non-multicast Target FEC Reverse Path field contains none, one or more sub-TLVs. Any non-
Stack sub-TLV (already defined, or to be defined in the future) for multicast Target FEC Stack sub-TLV (already defined, or to be defined
TLV Types 1, 16, and 21 of MPLS LSP Ping Parameters registry MAY be in the future) for TLV Types 1, 16, and 21 of MPLS LSP Ping
used in this field. Multicast Target FEC Stack sub-TLVs, i.e., p2mp Parameters registry MAY be used in this field. Multicast Target FEC
and mp2mp, SHOULD NOT be included in Reverse Path field. If the Stack sub-TLVs, i.e., p2mp and mp2mp, SHOULD NOT be included in
egress LSR finds multicast Target Stack sub-TLV, it MUST send echo Reverse Path field. If the egress LSR finds multicast Target Stack
reply with the received Reverse Path TLV, BFD Discriminator TLV and sub-TLV, it MUST send echo reply with the received Reverse Path TLV,
set the Return Code to "Inappropriate Target FEC Stack sub-TLV BFD Discriminator TLV and set the Return Code to "Inappropriate
present" Section 3.2. None, one or more sub-TLVs MAY be included in Target FEC Stack sub-TLV present" Section 3.2. None, one or more
the BFD Reverse Path TLV. If no sub-TLVs are found in the BFD sub-TLVs MAY be included in the BFD Reverse Path TLV. If no sub-TLVs
Reverse Path TLV, the egress BFD peer MUST revert to using the local are found in the BFD Reverse Path TLV, the egress BFD peer MUST
policy based decision as described in Section 7 [RFC5884], i.e., revert to using the local policy-based decision as described in
routed over IP network. Section 7 [RFC5884], i.e., routed over IP network.
If the egress LSR cannot find the path specified in the Reverse Path If the egress LSR cannot find the path specified in the Reverse Path
TLV it MUST send Echo Reply with the received BFD Discriminator TLV, TLV it MUST send Echo Reply with the received BFD Discriminator TLV,
Reverse Path TLV and set the Return Code to "Failed to establish the Reverse Path TLV and set the Return Code to "Failed to establish the
BFD session. The specified reverse path was not found" Section 3.2. BFD session. The specified reverse path was not found" Section 3.2.
An implementation MAY provide configuration options to define action An implementation MAY provide configuration options to define action
at the egress BFD peer. For example, if the egress LSR cannot find at the egress BFD peer. For example, if the egress LSR cannot find
the path specified in the Reverse Path TLV it MAY establish the BFD the path specified in the Reverse Path TLV, it MAY establish the BFD
session over IP network as defined in [RFC5884]. session over an IP network, as defined in [RFC5884].
3.2. Return Codes 3.2. Return Codes
This document defines the following Return Codes for MPLS LSP Echo This document defines the following Return Codes for MPLS LSP Echo
Reply: Reply:
o "Inappropriate Target FEC Stack sub-TLV present", (TBD3). When o "Inappropriate Target FEC Stack sub-TLV present", (TBD3). When
multicast Target FEC Stack sub-TLV found in the received Echo multicast Target FEC Stack sub-TLV found in the received Echo
Request by the egress BFD peer, an Echo Reply with the return code Request by the egress BFD peer, an Echo Reply with the return code
set to "Inappropriate Target FEC Stack sub-TLV present" MUST be set to "Inappropriate Target FEC Stack sub-TLV present" MUST be
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per [RFC7110], with that sub-TLV. By using the LSP Ping with Return per [RFC7110], with that sub-TLV. By using the LSP Ping with Return
Path TLV, an operator monitors whether at the egress BFD node the Path TLV, an operator monitors whether at the egress BFD node the
reverse LSP is mapped to the same FEC as the BFD session. Selection reverse LSP is mapped to the same FEC as the BFD session. Selection
and control of the rate of LSP Ping with Return Path TLV follows the and control of the rate of LSP Ping with Return Path TLV follows the
recommendation of [RFC5884]: "The rate of generation of these LSP recommendation of [RFC5884]: "The rate of generation of these LSP
Ping Echo request messages SHOULD be significantly less than the rate Ping Echo request messages SHOULD be significantly less than the rate
of generation of the BFD Control packets. An implementation MAY of generation of the BFD Control packets. An implementation MAY
provide configuration options to control the rate of generation of provide configuration options to control the rate of generation of
the periodic LSP Ping Echo request messages." the periodic LSP Ping Echo request messages."
If an operator planned network maintenance activity that possibly Suppose an operator planned network maintenance activity that
affects FEC used in the BFD Reverse Path TLV, the operator MUST avoid possibly affects FEC used in the BFD Reverse Path TLV. In that case,
the unnecessary disruption using the LSP Ping with a new FEC in the the operator MUST avoid the unnecessary disruption using the LSP Ping
BFD Reverse Path TLV. But in some scenarios, proactive measures with a new FEC in the BFD Reverse Path TLV. But in some scenarios,
cannot be taken. Because the frequency of LSP Ping messages will be proactive measures cannot be taken. Because the frequency of LSP
lower than the defect detection time provided by the BFD session. As Ping messages will be lower than the defect detection time provided
a result, a change in the reverse-path FEC will first be detected as by the BFD session. As a result, a change in the reverse-path FEC
the failure of the BFD session. In such a case, the ingress BFD node will first be detected as the BFD session's failure. In such a case,
SHOULD immediately transmit the LSP Ping Echo request with Return the ingress BFD node SHOULD immediately transmit the LSP Ping Echo
Path TLV to verify whether the FEC is still valid. If the failure request with Return Path TLV to verify whether the FEC is still
was caused by the change in the FEC used for the reverse direction of valid. If the failure was caused by the change in the FEC used for
the BFD session, the ingress BFD node SHOULD bootstrap a new BFD the reverse direction of the BFD session, the ingress BFD node SHOULD
session using another FEC in BFD Reverse Path TLV. bootstrap a new BFD session using another FEC in BFD Reverse Path
TLV.
6. IANA Considerations 6. IANA Considerations
6.1. BFD Reverse Path TLV 6.1. BFD Reverse Path TLV
The IANA is requested to assign a new value for BFD Reverse Path TLV The IANA is requested to assign a new value for BFD Reverse Path TLV
from the "Multiprotocol Label Switching Architecture (MPLS) Label from the "Multiprotocol Label Switching Architecture (MPLS) Label
Switched Paths (LSPs) Ping Parameters - TLVs" registry, "TLVs and Switched Paths (LSPs) Ping Parameters - TLVs" registry, "TLVs and
sub-TLVs" sub-registry. sub-TLVs" sub-registry.
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6.2. Return Code 6.2. Return Code
The IANA is requested to assign a new Return Code value from the The IANA is requested to assign a new Return Code value from the
"Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs) "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs)
Ping Parameters" registry, "Return Codes" sub-registry, as follows Ping Parameters" registry, "Return Codes" sub-registry, as follows
using a Standards Action value. using a Standards Action value.
+--------+----------------------------------------------+-----------+ +--------+----------------------------------------------+-----------+
| Value | Description | Reference | | Value | Description | Reference |
+--------+----------------------------------------------+-----------+ +--------+----------------------------------------------+-----------+
| (TBD3) | Inappropriate Target FEC Stack sub-TLV | This | | (TBD3) | Inappropriate Target FEC Stack sub-TLV | This docu |
| | present. | document | | | present. | ment |
| (TBD4) | Failed to establish the BFD session. The | This | | (TBD4) | Failed to establish the BFD session. The | This docu |
| | specified reverse path was not found. | document | | | specified reverse path was not found. | ment |
+--------+----------------------------------------------+-----------+ +--------+----------------------------------------------+-----------+
Table 2: New Return Code Table 2: New Return Code
7. Implementation Status 7. Implementation Status
- The organization responsible for the implementation: ZTE - The organization responsible for the implementation: ZTE
Corporation. Corporation.
- The implementation's name ROSng empowers traditional routers, e.g., - The implementation's name ROSng empowers traditional routers, e.g.,
ZXCTN 6000. ZXCTN 6000.
- A brief general description: A Return Path can be specified for a - A brief general description: A Return Path can be specified for a
BFD session over RSVP tunnel or LSP. Same can be specified for a BFD session over RSVP tunnel or LSP. The same can be specified for a
backup RSVP tunnel/LSP. backup RSVP tunnel/LSP.
The implementation's level of maturity: production. The implementation's level of maturity: production.
- Coverage: RSVP LSP (no support for Static LSP) - Coverage: RSVP LSP (no support for Static LSP)
- Version compatibility: draft-ietf-mpls-bfd-directed-10. - Version compatibility: draft-ietf-mpls-bfd-directed-10.
- Licensing: proprietary. - Licensing: proprietary.
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- The date when information about this particular implementation was - The date when information about this particular implementation was
last updated: 12/16/2019 last updated: 12/16/2019
Note to RFC Editor: This section MUST be removed before publication Note to RFC Editor: This section MUST be removed before publication
of the document. of the document.
8. Security Considerations 8. Security Considerations
Security considerations discussed in [RFC5880], [RFC5884], [RFC7726], Security considerations discussed in [RFC5880], [RFC5884], [RFC7726],
and [RFC8029], apply to this document. [RFC8029], and [RFC7110] apply to this document.
9. Normative References 9. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
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Switched (MPLS) Data-Plane Failures", RFC 8029, Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017, DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>. <https://www.rfc-editor.org/info/rfc8029>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Appendix A. Acknowledgments Appendix A. Acknowledgments
Authors greatly appreciate thorough review and the most helpful The authors greatly appreciate a thorough review and the most helpful
comments from Eric Gray and Carlos Pignataro. Authors greatly comments from Eric Gray and Carlos Pignataro. The authors much
appreciate the help of Qian Xin, who provided the information about appreciate the help of Qian Xin, who provided information about the
the implementation of this specification. implementation of this specification.
Authors' Addresses Authors' Addresses
Greg Mirsky Greg Mirsky
ZTE ZTE
Email: gregimirsky@gmail.com Email: gregimirsky@gmail.com
Jeff Tantsura Jeff Tantsura
Nuage Networks Nuage Networks
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