Internet DRAFT - draft-mtm-rtgwg-bfd-mc-lag
draft-mtm-rtgwg-bfd-mc-lag
RTG Working Group G. Mirsky
Internet-Draft Ericsson
Intended status: Standards Track J. Tantsura
Expires: 29 March 2023 Microsoft
G. Mishra
Verizon Inc.
25 September 2022
Bidirectional Forwarding Detection (BFD) on Multi-chassis Link
Aggregation Group (MC-LAG) Interfaces
draft-mtm-rtgwg-bfd-mc-lag-05
Abstract
This document describes the use of Bidirectional Forwarding Detection
for Multi-chassis Link Aggregation Group to provide faster than Link
Aggregation Control Protocol convergence. This specification
enhances RFC 7130 "Bidirectional Forwarding Detection (BFD) on Link
Aggregation Group (LAG) Interfaces".
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 29 March 2023.
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document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 2
1.1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . 2
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
3. BFD on MC-LAG with IP-only Data Plane . . . . . . . . . . . . 3
4. BFD on MC-LAG with IP/MPLS Data Plane . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . 4
8.2. Informative . . . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The [RFC7130] defines the use of Bidirectional Forwarding Detection
(BFD) on Link Aggregation Group (LAG) interfaces. A multi-chassis
LAG (MC-LAG) is a type of LAG [IEEE.802.1AX.2008] with member links
terminated on separate chassis. [IEEE.802.1AX.2008] does not specify
MC-LAG but doesn't preclude it either. Link Aggregation Control
Protocol (LACP), also defined in [IEEE.802.1AX.2008], can work with
MC-LAG but, as in the LAG case, the fastest link failure detection
interval is only in a range of single-digit seconds. This document
defines how the mechanism defined to work on LAG interfaces [RFC7130]
can be adapted to the MC-LAG case to enable sub-second detection of
member link failure.
1.1. Conventions used in this document
1.1.1. Acronyms
BFD: Bidirectional Forwarding Detection
LAG: Link Aggregation Group
LACP: Link Aggregation Control Protocol
MC-LAG: Multi-chassis Link Aggregation Group
MPLS: Multi-Protocol Label Switching
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1.1.2. 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.
2. Problem Statement
[RFC7130] does not specify the selection of the destination IP
address for the BFD control packet. The only requirement related to
the selection is in Section 2.1, stating that the use of the address
family across all member links of the given LAG MUST be consistent
across all the links. Thus it is implied that the same unicast IP
address will be used on all member links of the LAG as the use of
different destination addresses would defeat the purpose of [RFC7130]
transforming the case into a set of single-hop BFD sessions
[RFC5881]. But a single unicast IP address may not work in the MC-
LAG case as the member links are terminated on the separate chassis.
This document proposes overcoming this problem if using IP or Multi-
Protocol Label Switching (MPLS) data plane encapsulation.
3. BFD on MC-LAG with IP-only Data Plane
As described in [RFC7130], a micro-BFD session on the LAG interfaces
may use IPv4 or IPv6 address family. In some cases, two sessions,
one with IPv4 and one with IPv6 addresses, may run concurrently.
This document doesn't change any of these but specifies the selection
of the destination IP address in the MC-LAG use case:
* if IPv4 address family is used for the micro-BFD session, then an
address from the link-local multicast address 224.0.0.0/24 range
SHOULD be used as the destination IP address. The subnet
broadcast address MAY be used as the destination IP address as
well;
* if the address family used is IPv6, then the IPv6 All Routers
address with the link scope, as defined in [RFC4291], FF02::2/128
MUST be used as the destination IP address.
4. BFD on MC-LAG with IP/MPLS Data Plane
IP/UDP is the most natural encapsulation format for the case of
micro-BFD on MC-LAG over IP/MPLS data plane as displayed in Figure 1.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ MPLS Label Stack ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------
~ ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IP
| Destination IP address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Header
| Source IP address | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+------
| UDP header |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ BFD Control Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BFD on MC-LAG member link on IPv4/MPLS data plane
An IP and UDP headers immediately follow an MPLS label stack. The
destination IP address MUST be set to the loopback address
127.0.0.1/32 for IPv4 [RFC1812], or the loopback address ::1/128 for
IPv6 [RFC4291]. TTL or Hop Limit field value MUST be set to 255,
according to [RFC5881].
5. IANA Considerations
This document makes no requests for IANA allocations. This section
may be deleted by RFC Editor.
6. Security Considerations
This document does not introduce new security concerns but inherits
all security considerations discussed in [RFC5881] and [RFC7130].
7. Acknowledgements
TBD
8. References
8.1. Normative References
[IEEE.802.1AX.2008]
"IEEE Standard for Local and metropolitan area networks -
Link Aggregation", IEEE 802.1-AX, November 2008.
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[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>.
[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
DOI 10.17487/RFC5881, June 2010,
<https://www.rfc-editor.org/info/rfc5881>.
[RFC7130] Bhatia, M., Ed., Chen, M., Ed., Boutros, S., Ed.,
Binderberger, M., Ed., and J. Haas, Ed., "Bidirectional
Forwarding Detection (BFD) on Link Aggregation Group (LAG)
Interfaces", RFC 7130, DOI 10.17487/RFC7130, February
2014, <https://www.rfc-editor.org/info/rfc7130>.
[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>.
8.2. Informative
[RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers",
RFC 1812, DOI 10.17487/RFC1812, June 1995,
<https://www.rfc-editor.org/info/rfc1812>.
[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>.
Authors' Addresses
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com
Jeff Tantsura
Microsoft
Email: jefftant.ietf@gmail.com
Gyan Mishra
Verizon Inc.
Email: gyan.s.mishra@verizon.com
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