Internet DRAFT - draft-ietf-bier-bfd
draft-ietf-bier-bfd
BIER WG Q. Xiong
Internet-Draft ZTE Corporation
Intended status: Standards Track G. Mirsky
Expires: 16 August 2024 Ericsson
F. Hu
Individual
C. Liu
China Unicom
13 February 2024
BIER BFD
draft-ietf-bier-bfd-05
Abstract
Point to multipoint (P2MP) BFD is designed to verify multipoint
connectivity. This document specifies the application of P2MP BFD in
BIER network.
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 16 August 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. BIER BFD Encapsulation . . . . . . . . . . . . . . . . . . . 3
4. BIER BFD Session Bootstrapping . . . . . . . . . . . . . . . 4
4.1. BIER OAM Bootstrapping . . . . . . . . . . . . . . . . . 4
4.2. IGP Bootstrapping . . . . . . . . . . . . . . . . . . . . 5
4.2.1. IS-IS Extension for BIER BFD . . . . . . . . . . . . 5
4.2.2. OSPF Extension for BIER BFD . . . . . . . . . . . . . 6
4.3. BGP Bootstrapping . . . . . . . . . . . . . . . . . . . . 7
5. Discriminators and Packet Demultiplexing . . . . . . . . . . 7
6. Active Tail in BIER BFD . . . . . . . . . . . . . . . . . . . 7
6.1. Unsolicited Head Notification Mode . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9.1. BIER OAM Message Type . . . . . . . . . . . . . . . . . . 9
9.2. BFD Discriminator TLV . . . . . . . . . . . . . . . . . . 9
9.3. BIER BFD Sub-sub-TLV . . . . . . . . . . . . . . . . . . 9
9.4. BIER BFD Sub-TLV . . . . . . . . . . . . . . . . . . . . 10
9.5. BGP's BFD Discriminator Attribute Mode of P2MP Session with
Active Tails . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Bit Index Explicit Replication (BIER) [RFC8279] provides the
forwarding of multicast data packets through a multicast domain. It
does so without requiring any explicit tree-building protocol and
without requiring intermediate nodes to maintain any per-flow state.
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[RFC8562] defines a method of using Bidirectional Forwarding
Detection (BFD) to monitor and detect unicast failures between the
sender (head) and one or more receivers (tails) in multipoint or
multicast networks. [RFC8563] describes active tail extensions to
the BFD protocol for multipoint networks.
This document describes the procedures for using such mode of BFD
protocol to monitor connectivity between a multipoint sender, Bit-
Forwarding Ingress Router (BFIR), and a set of one or more multipoint
receivers, Bit-Forwarding Egress Routers (BFERs). The BIER BFD only
supports the unidirectional multicast. This document defines the use
of P2MP BFD as per [RFC8562], and active tail as per [RFC8563] for
BIER-specific domain.
2. Conventions used in this document
2.1. Terminology
This document uses the acronyms defined in [RFC8279] along with the
following:
BFD: Bidirectional Forwarding Detection.
OAM: Operations, Administration, and Maintenance.
P2MP: Point to Multi-Point.
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. BIER BFD Encapsulation
BIER BFD encapsulation uses the BIER OAM packet format defined in
[I-D.ietf-bier-ping]. The value of the Message Type field MUST be
set to BIER BFD (TBD1 will be assigned by IANA Section 9.1). BFD
Control packet, defined in Section 4 [RFC5880], immediately follows
the BIER OAM header. The operation of Multipoint BFD with the BFD
Control Packet is described in [RFC8562].
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4. BIER BFD Session Bootstrapping
As defined in [RFC8562], a BIER BFD session MAY be established to
monitor the state of the multipoint path. The BIER BFD session could
be created for each multipoint path and the set of BFERs over which
the BFIR is requested to run BIER BFD. The BFIR MUST advertise the
multipoint path and the value of My Discriminator associated with the
path to the set of BFERs. The BFIR MUST bootstrap the BFD session
and advertise the BFD information to the set of BFERs. Bootstrapping
a BIER BFD session MAY use BIER OAM message (Section 4.1) or the
control plane (Section 4.2, Section 4.3).
The BIER BFD bootstrapping MUST be repeated when the value of this
discriminator being changed.
4.1. BIER OAM Bootstrapping
The BIER OAM could be used for bootstrapping the BIER BFD session.
The BFIR sends the BIER OAM Echo request message carrying a BFD
discriminator TLV which immediately follows the Target SI-Bitstring
TLV (section 3.3.2 [I-D.ietf-bier-ping]).
The Target SI-Bitstring TLV MUST be used to carry the set of BFER
information (including Sub-domain-id, Set ID, BS Len, Bitstring) for
the purpose of the session establishment.
Figure 1 displays the format of BFD Discriminator TLV.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD2 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BFD Discriminator TLV
where:
* Type indicates BFD Discriminator TLV. The value (TBD2) is to be
allocated by IANA (Section 9.2).
* Length MUST be set to 4.
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* My Discriminator - four-octet long field. The value is the local
discriminator generated by BFIR for this session. This
discriminator MUST be used as the My Discriminator field n the
BIER BFD Control packets sent by the BFIR.
4.2. IGP Bootstrapping
An alternative option to bootstrap the BIER BFD using a BIER OAM
message is to advertise the BFD information by an IGP protocol over
the control plane. This document defines a new BIER BFD Sub-sub-TLV
to carry BFD information in IGP protocols IS-IS and OSPF.
The BFIR generates the My Discriminator value for each multicast flow
and advertises it to the expecting BFERs, which is indicated by the
Bitstring and the BIFT-id, which is carried in BIER BFD sub-sub-TLV.
The corresponding BFERs SHOULD store the My Discriminator value for
packet Demultiplexing.
4.2.1. IS-IS Extension for BIER BFD
The new BIER BFD Sub-sub-TLV is carried within the BIER Info sub-TLV
defined in [RFC8401]. The format is displayed in Figure 2.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD3 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | BIFT-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (first 32 bits) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ BitString (last 32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: BIER BFD Sub-sub-TLV for IS-IS Extension
where:
* Type indicates BIER BFD sub-sub-TLV. The value (TBD3) is to be
allocated by IANA (Section 9.3).
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* Length is a two-octet field. The value is the length of the BIER
BFD Sub-sub-TLV for IS-IS extension, in octets
* My Discriminator is a four-octet long field. The value is a
unique, nonzero discriminator value generated by BFIR for each
multipoint path. This discriminator MUST be used as the My
Discriminator field n the BIER BFD Control packets sent by the
BFIR.
* BIFT-id is a two-octet field. The value represents a particular
Bit Index Forwarding Table (BIFT) as per [RFC8279].
* BitString field carries the set of BFR-IDs of BFER(s) that the
BFIR expects to establish the BIER BFD session.
4.2.2. OSPF Extension for BIER BFD
The new BIER BFD Sub-TLV is a sub-TLV of the BIER Sub-TLV defined in
[RFC8444]. The format is displayed in Figure 3.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD4 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | BIFT-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (first 32 bits) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ BitString (last 32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: BIER BFD Sub-sub-TLV for OSPF Extension
where:
* Type indicates BIER BFD sub-TLV. The value (TBD4) is to be
allocated by IANA (Section 9.4).
* Length is a two-octet field. The value is the length of the BIER
BFD sub-TLV for OSPF extension, in octets
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* My Discriminator is a four-octet long field. The value is a
unique, nonzero discriminator value generated by BFIR for each
multipoint path. This discriminator MUST be used as the My
Discriminator field n the BIER BFD Control packets sent by the
BFIR.
* BIFT-id is a two-octet field. The value represents a particular
Bit Index Forwarding Table (BIFT) as per [RFC8279].
* BitString field carries the set of BFR-IDs of BFER(s) that the
BFIR expects to establish the BIER BFD session.
4.3. BGP Bootstrapping
[RFC9026] describes the applicability of [RFC8562] in the detection
of a Multicast Virtual Private Network. The new BGP Attribute, BFD
Discriminator, can be used to bootstrap a p2mp BFD session according
to [RFC8562]. To bootstrap a p2mp BFD session with active tails
according to [RFC8563] IANA is requested to allocate a new value
(TBD5) for the BFD Mode (Section 9.5).
5. Discriminators and Packet Demultiplexing
As defined in [RFC8562], the BFIR sends BFD Control packets to the
set of BFERs over the multipoint path via the BIER BFD session with
My Discriminator is set to the value assigned by the BFIR, and the
value of the Your Discriminator is set to zero. The set of BFERs
MUST demultiplex BFD packets based on a combination of the source
address, My Discriminator value. The source address is BFIR-id and
BIER MPLS Label (MPLS network) or BFIR-id and BIFT-id (Non-MPLS
network) for BIER BFD. My Discriminator value is advertised in BIER
BFD bootstrapping using one of the options described in Section 4.
6. Active Tail in BIER BFD
[RFC8563] defined an extension for Multipoint BFD, which allows the
head to discover the state of a multicast distribution tree for any
sub-set of tails. For BIER BFD in the active tail mode, the BFIR may
learn the state and connectivity of the BFERs by allowing the BFERs
to notify the BFIR. As per [RFC8563] provides detailed information
on how the BFIR can use multipoint Poll sequence message or a
combination of multicast and unicast Poll sequence messages to
determine the state of the multicast tree. Also, [RFC8563] describes
that a BFER can transmit an unsolicited unicast Poll sequence message
to the BFIR (note that a unicast message must be sent over a path
which is disjoint from the multicast distribution tree).
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6.1. Unsolicited Head Notification Mode
[I-D.ietf-mpls-p2mp-bfd] provides detailed information on using the
unsolicited notification method for P2MP MPLS LSP, which is also
applicable to BIER.
In Section 5.2.1 [RFC8563] is noted that "the tail sends unsolicited
BFD packets in response to the detection of a multipoint path
failure" but without the specifics on the information in the packet
and frequency of transmissions. This document defines the procedure
of the active tail with unsolicited notifications for BIER as
specified below.
Upon detecting the failure, a BFER sends a BFD control packet with
the following settings:
* the Poll (P) bit is set;
* the Status (Sta) field is set to Down value;
* the Diagnostic (Diag) field is set to Control Detection Time
Expired value;
* the value of the Your Discriminator field is set to the value the
BFER has been used to demultiplex that BFD multipoint session;
* BFD Control packet is encapsulated in IP/UDP with the destination
IP address of the BFIR and the UDP destination port number set to
4784 per [RFC5883]
* the BFD Control packets are transmitted at the rate of one per
second until either the BFER receives valid for this BFD session
control packet with the Final (F) bit is set from the BFIR or the
defect condition clears.
To improve the likelihood of notifying the BFIR of the failure, the
BFER SHOULD transmit three BFD Control packets defined above in short
succession.
A BFIR that has received the BFD Control packet, as described above,
sends the unicast IP/UDP encapsulated BFD control packet with the
Final (F) bit set to the BFER.
7. Security Considerations
For BIER OAM packet processing security considerations, see
[I-D.ietf-bier-ping].
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For general multipoint BFD security considerations, see [RFC8562].
No additional security issues are raised in this document beyond
those that exist in the referenced BFD documents.
8. Acknowledgements
The authors would like to thank the comments and suggestions from
Sandy Zhang, Jeffrey (Zhaohui) Zhang, Donald Eastlake 3rd.
9. IANA Considerations
9.1. BIER OAM Message Type
IANA is requested to assign a new type from the BIER OAM Message Type
registry as follows:
+=======+=============+=================+
| Value | Description | Reference |
+=======+=============+=================+
| TBD1 | BIER BFD | [this document] |
+-------+-------------+-----------------+
Table 1
9.2. BFD Discriminator TLV
IANA is requested to assign a new type from the BIER OAM TLV registry
as follows:
+=======+=======================+=================+
| Value | Description | Reference |
+=======+=======================+=================+
| TBD2 | BFD discriminator TLV | [this document] |
+-------+-----------------------+-----------------+
Table 2
9.3. BIER BFD Sub-sub-TLV
IANA is requested to assign a new BIER BFD Sub-sub-TLV within the
BIER Info sub-TLV registry is defined in [RFC8401] as follows:
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+=======+======================+=================+
| Value | Description | Reference |
+=======+======================+=================+
| TBD3 | BIER BFD Sub-sub-TLV | [this document] |
+-------+----------------------+-----------------+
Table 3
9.4. BIER BFD Sub-TLV
IANA is requested to assign a new BIER BFD Sub-TLV from the BIER Sub-
TLV registry is defined in [RFC8444] as follows:
+=======+==================+=================+
| Value | Description | Reference |
+=======+==================+=================+
| TBD4 | BIER BFD Sub-TLV | [this document] |
+-------+------------------+-----------------+
Table 4
9.5. BGP's BFD Discriminator Attribute Mode of P2MP Session with Active
Tails
IANA is requested to assign a new value from "BFD Mode" subregistry
(defined in [RFC9026]) in the "Border Gateway Protocol (BGP)
Parameters" registry according to Table 5:
+=======+====================================+=================+
| Value | Description | Reference |
+=======+====================================+=================+
| TBD5 | P2MP BFD Session with Active Tails | [this document] |
+-------+------------------------------------+-----------------+
Table 5
10. References
10.1. Normative References
[I-D.ietf-bier-ping]
Nainar, N. K., Pignataro, C., Chen, M., and G. Mirsky,
"BIER Ping and Trace", Work in Progress, Internet-Draft,
draft-ietf-bier-ping-13, 27 January 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-bier-
ping-13>.
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[I-D.ietf-mpls-p2mp-bfd]
Mirsky, G., Mishra, G. S., and D. E. Eastlake, "BFD for
Multipoint Networks over Point-to-Multi-Point MPLS LSP",
Work in Progress, Internet-Draft, draft-ietf-mpls-p2mp-
bfd-06, 15 December 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
p2mp-bfd-06>.
[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>.
[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>.
[RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
June 2010, <https://www.rfc-editor.org/info/rfc5883>.
[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>.
[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.
[RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z.
Zhang, "Bit Index Explicit Replication (BIER) Support via
IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018,
<https://www.rfc-editor.org/info/rfc8401>.
[RFC8444] Psenak, P., Ed., Kumar, N., Wijnands, IJ., Dolganow, A.,
Przygienda, T., Zhang, J., and S. Aldrin, "OSPFv2
Extensions for Bit Index Explicit Replication (BIER)",
RFC 8444, DOI 10.17487/RFC8444, November 2018,
<https://www.rfc-editor.org/info/rfc8444>.
[RFC8562] Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,
Ed., "Bidirectional Forwarding Detection (BFD) for
Multipoint Networks", RFC 8562, DOI 10.17487/RFC8562,
April 2019, <https://www.rfc-editor.org/info/rfc8562>.
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[RFC8563] Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,
Ed., "Bidirectional Forwarding Detection (BFD) Multipoint
Active Tails", RFC 8563, DOI 10.17487/RFC8563, April 2019,
<https://www.rfc-editor.org/info/rfc8563>.
[RFC9026] Morin, T., Ed., Kebler, R., Ed., and G. Mirsky, Ed.,
"Multicast VPN Fast Upstream Failover", RFC 9026,
DOI 10.17487/RFC9026, April 2021,
<https://www.rfc-editor.org/info/rfc9026>.
Authors' Addresses
Quan Xiong
ZTE Corporation
China
Email: xiong.quan@zte.com.cn
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com
Fangwei Hu
Individual
Email: hufwei@gmail.com
Chang Liu
China Unicom
No.9 Shouti Nanlu
Beijing
100048
China
Phone: +86-010-68799999-7294
Email: liuc131@chinaunicom.cn
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