MPLS Working Group G. Mirsky
Internet-Draft ZTE Corp.
Intended status: Standards Track November 19, 2018
Expires: May 23, 2019
BFD for Multipoint Networks over Point-to-Multi-Point MPLS LSP
draft-mirsky-mpls-p2mp-bfd-05
Abstract
This document describes procedures for using Bidirectional Forwarding
Detection (BFD) for multipoint networks to detect data plane failures
in Multiprotocol Label Switching (MPLS) point-to-multipoint (p2mp)
Label Switched Paths (LSPs). It also describes the applicability of
out-band solutions to bootstrap a BFD session in this environment.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on May 23, 2019.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Multipoint BFD Encapsulation . . . . . . . . . . . . . . . . 3
3.1. IP Encapsulation of Multipoint BFD . . . . . . . . . . . 3
3.2. Non-IP Encapsulation of Multipoint BFD . . . . . . . . . 4
4. Bootstrapping Multipoint BFD . . . . . . . . . . . . . . . . 4
4.1. LSP Ping . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. Control Plane . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6.1. Source MEP ID IP Address Type . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
[I-D.ietf-bfd-multipoint] defines a method of using Bidirectional
Detection (BFD) [RFC5880] to monitor and detect unicast failures
between the sender (head) and one or more receivers (tails) in
multipoint or multicast networks. This document describes procedures
for using such mode of BFD protocol to detect data plane failures in
Multiprotocol Label Switching (MPLS) point-to-multipoint (p2mp) Label
Switched Paths (LSPs). The document also describes the applicability
of out-band solutions to bootstrap a BFD session in this environment.
2. Conventions used in this document
2.1. Terminology
MPLS: Multiprotocol Label Switching
LSP: Label Switched Path
BFD: Bidirectional Forwarding Detection
p2mp: Point-to-Multipoint
FEC: Forwarding Equivalence Class
G-ACh: Generic Associated Channel
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ACH: Associated Channel Header
GAL: G-ACh Label
2.2. 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. Multipoint BFD Encapsulation
[I-D.ietf-bfd-multipoint] defines how the tail of multipoint BFD
session demultiplexes received BFD control packet when Your
Discriminator is not set, i.e., equals zero. Because
[I-D.ietf-bfd-multipoint] uses BFD in Demand mode from the very start
of the p2mp BFD session, the head of BFD multipoint session transmits
all BFD control packets with Your Discriminator set to zero. As a
result, a tail cannot demultiplex BFD sessions using Your
Discriminator, as defined in [RFC5880]. [I-D.ietf-bfd-multipoint]
requires that to demultiplex BFD sessions the tail uses the source IP
address, My Discriminator and the identity of the multipoint tree
from which the Multipoint BFD Control packet was received. The
identification of the multipoint tree MAY be provided by the p2mp
MPLS LSP label in case of inclusive p-tree or upstream assigned label
in case of aggregate p-tree. If the BFD control packet is
encapsulated in IP/UDP, then the source IP address MUST be used to
demultiplex the received BFD control packet as described in
Section 3.1. The non-IP encapsulation case is described in
Section 3.2.
3.1. IP Encapsulation of Multipoint BFD
[I-D.ietf-bfd-multipoint] defines IP/UDP encapsulation for multipoint
BFD over p2mp MPLS LSP:
UDP destination port MUST be set to 3784;
destination IP address MUST be from the 127/8 range for IPv4 and
from the 0:0:0:0:0:FFFF:7F00/104 range for IPv6;
This specification further clarifies that:
if multiple alternative paths for the given p2mp LSP Forwarding
Equivalence Class (FEC) exist, the MultipointHead SHOULD use
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Entropy Label [RFC6790] used for LSP Ping [RFC8029] to exercise
that particular alternative path;
or the MultipointHead MAY use the IP address discovered by LSP
Ping traceroute [RFC8029] as the destination IP address to
possibly exercise that particular alternate path.
3.2. Non-IP Encapsulation of Multipoint BFD
In some environments, the overhead of extra IP/UDP encapsulations may
be considered as overburden and make using more compact G-ACh
encapsulation attractive. Non-IP encapsulation for multipoint BFD
over p2mp MPLS LSP MUST use Generic Associated Channel (G-ACh) Label
(GAL) [RFC5586] at the bottom of the label stack followed by
Associated Channel Header (ACH). Channel Type field in ACH MUST be
set to MPLS-TP CV value (0x0023) [RFC6428]. To provide the identity
of the MultipointHead for the particular multipoint BFD session this
document defines new Source MEP ID IP Address type (TBA1) in
Section 6.1. If the Length value is 4, then the Value field contains
an IPv4 address. If the Length value is 16, then the Value field
contains an IPv6 address. Any other value of the Length field MUST
be considered as an error, and the BFD control packet MUST be
discarded.
4. Bootstrapping Multipoint BFD
4.1. LSP Ping
LSP Ping is the part of on-demand OAM toolset to detect and localize
defects in the data plane, and verify the control plane against the
data plane by ensuring that the LSP is mapped to the same FEC, at the
egress, as the ingress.
LSP Ping, as defined in [RFC6425], MAY be used to bootstrap
MultipointTail. If the LSP Ping used, it MUST include the Target FEC
TLV and the BFD Discriminator TLV defined in [RFC5884]. The Target
FEC TLV MUST use sub-TLVs defined in Section 3.1 [RFC6425]. It is
RECOMMENDED setting the value of Reply Mode field to "Do not reply"
[RFC8029] for the LSP Ping to bootstrap MultipointTail of the p2mp
BFD session. A MaultipointTail that receives the LSP Ping that
includes the BFD Discriminator TLV:
o MUST validate the LSP Ping;
o MUST associate the received BFD Discriminator value with the p2mp
LSP;
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o MUST create p2mp BFD session and set bfd.SessionType =
MultipointTail as described in [I-D.ietf-bfd-multipoint];
o MUST use the source IP address of LSP Ping, the value of BFD
Discriminator from the BFD Discriminator TLV, and the identity of
the p2mp LSP to properly demultiplex BFD sessions.
Besides bootstrapping a BFD session over a p2mp LSP, LSP Ping SHOULD
be used to verify the control plane against the data plane
periodically by checking that the p2mp LSP is mapped to the same FEC
at the MultipointHead and all active MultipointTails. The rate of
generation of these LSP Ping Echo request messages SHOULD be
significantly less than the rate of generation of the BFD Control
packets because LSP Ping requires more processing to validate the
consistency between the data plane and the control plane. An
implementation MAY provide configuration options to control the rate
of generation of the periodic LSP Ping Echo request messages.
4.2. Control Plane
BGP-BFD Attribute [I-D.ietf-bess-mvpn-fast-failover] MAY be used to
bootstrap multipoint BFD session on a tail.
5. Security Considerations
This document does not introduce new security aspects but inherits
all security considerations from [RFC5880], [RFC5884], [RFC7726],
[I-D.ietf-bfd-multipoint], [RFC8029], and [RFC6425].
Also, BFD for p2mp MPLS LSP MUST follow the requirements listed in
section 4.1 [RFC4687] to avoid congestion in the control plane or the
data plane caused by the rate of generating BFD control packets. An
operator SHOULD consider the amount of extra traffic generated by
p2mp BFD when selecting the interval at which the MultipointHead will
transmit BFD control packets. Also, the operator MAY consider the
size of the packet the MultipointHead transmits periodically as using
IP/UDP encapsulation adds up to 28 octets, which is more than 50% of
BFD control packet length, comparing to G-ACh encapsulation.
6. IANA Considerations
6.1. Source MEP ID IP Address Type
IANA is required to allocate value (TBD) for the Source MEP ID IP
Address type from the "CC/CV MEP-ID TLV" registry which is under the
"Pseudowire Associated Channel Types" registry.
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+-------+-------------+---------------+
| Value | Description | Reference |
+-------+-------------+---------------+
| TBA1 | IP Address | This document |
+-------+-------------+---------------+
Table 1: Source MEP ID IP Address TLV Type
7. Acknowledgements
The author sincerely appreciates the comments received from Andrew
Malis.
8. References
8.1. Normative References
[I-D.ietf-bess-mvpn-fast-failover]
Morin, T., Kebler, R., and G. Mirsky, "Multicast VPN fast
upstream failover", draft-ietf-bess-mvpn-fast-failover-04
(work in progress), November 2018.
[I-D.ietf-bfd-multipoint]
Katz, D., Ward, D., Networks, J., and G. Mirsky, "BFD for
Multipoint Networks", draft-ietf-bfd-multipoint-18 (work
in progress), June 2018.
[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>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<https://www.rfc-editor.org/info/rfc5586>.
[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>.
[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>.
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[RFC6425] Saxena, S., Ed., Swallow, G., Ali, Z., Farrel, A.,
Yasukawa, S., and T. Nadeau, "Detecting Data-Plane
Failures in Point-to-Multipoint MPLS - Extensions to LSP
Ping", RFC 6425, DOI 10.17487/RFC6425, November 2011,
<https://www.rfc-editor.org/info/rfc6425>.
[RFC6428] Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed.,
"Proactive Connectivity Verification, Continuity Check,
and Remote Defect Indication for the MPLS Transport
Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011,
<https://www.rfc-editor.org/info/rfc6428>.
[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>.
[RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S.
Aldrin, "Clarifying Procedures for Establishing BFD
Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726,
DOI 10.17487/RFC7726, January 2016,
<https://www.rfc-editor.org/info/rfc7726>.
[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>.
8.2. Informative References
[RFC4687] Yasukawa, S., Farrel, A., King, D., and T. Nadeau,
"Operations and Management (OAM) Requirements for Point-
to-Multipoint MPLS Networks", RFC 4687,
DOI 10.17487/RFC4687, September 2006,
<https://www.rfc-editor.org/info/rfc4687>.
Author's Address
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
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