< draft-chen-bier-frr-04.txt   draft-chen-bier-frr-05.txt >
Network Working Group H. Chen, Ed. Network Working Group H. Chen, Ed.
Internet-Draft M. McBride Internet-Draft M. McBride
Intended status: Informational Futurewei Intended status: Informational Futurewei
Expires: July 6, 2022 S. Lindner Expires: October 5, 2022 S. Lindner
M. Menth M. Menth
University of Tuebingen University of Tuebingen
A. Wang A. Wang
China Telecom China Telecom
G. Mishra G. Mishra
Verizon Inc. Verizon Inc.
Y. Liu Y. Liu
China Mobile China Mobile
Y. Fan Y. Fan
Casa Systems Casa Systems
L. Liu L. Liu
Fujitsu Fujitsu
X. Liu X. Liu
Volta Networks Volta Networks
January 2, 2022 April 3, 2022
BIER Fast ReRoute BIER Fast ReRoute
draft-chen-bier-frr-04 draft-chen-bier-frr-05
Abstract Abstract
BIER is a scalable multicast overlay [RFC8279] that utilizes a BIER is a scalable multicast overlay [RFC8279] that utilizes a
routing underlay, e.g., IP, to build up its Bit Index Forwarding routing underlay, e.g., IP, to build up its Bit Index Forwarding
Tables (BIFTs). This document proposes Fast Reroute Extensions for Tables (BIFTs). This document proposes Fast Reroute for BIER (BIER-
BIER (BIER-FRR). It protects BIER traffic after detecting the FRR). It protects BIER traffic after detecting the failure of a link
failure of a link or node in the core of a BIER domain until affected or node in the core of a BIER domain until affected BIFT entries are
BIFT entries are recomputed after reconvergence of the routing recomputed after reconvergence of the routing underlay. BIER-FRR is
underlay. The BIER-FRR extensions are applied locally at the point applied locally at the point of local repair (PLR) and does not
of local repair (PLR) and do not introduce any per-flow state. The introduce any per-flow state. The document specifies nomenclature
document specifies nomenclature for BIER-FRR and gives examples for for BIER-FRR and gives examples for its integration in BIER
its integration in BIER forwarding. Furthermore, it presents forwarding. Furthermore, it presents operation modes for BIER-FRR.
operation modes for BIER-FRR. Link and node protection may be chosen Link and node protection may be chosen as protection level.
as protection level. Moreover, the backup strategies tunnel-based Moreover, the backup strategies tunnel-based BIER-FRR and LFA-based
BIER-FRR and LFA-based BIER-FRR are defined and compared. BIER-FRR are defined and compared.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119] [RFC8174] document are to be interpreted as described in [RFC2119] [RFC8174]
when, and only when, they appear in all capitals, as shown here. when, and only when, they appear in all capitals, as shown here.
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
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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 July 6, 2022. This Internet-Draft will expire on October 5, 2022.
Copyright Notice Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the Copyright (c) 2022 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
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Extensions for BIER-FRR . . . . . . . . . . . . . . . . . . . 5 2. Definition of BIER-FRR . . . . . . . . . . . . . . . . . . . 5
2.1. Definition of Forwarding Actions . . . . . . . . . . . . 5 2.1. Definition of Forwarding Actions . . . . . . . . . . . . 5
2.2. Definition of Backup Forwarding Entries . . . . . . . . . 5 2.2. Definition of Backup Forwarding Entries . . . . . . . . . 5
2.3. Activating and Deactivating Backup Forwarding Entries . . 6 2.3. Activating and Deactivating Backup Forwarding Entries . . 6
2.4. Computation of the Backup F-BM . . . . . . . . . . . . . 7 2.4. Computation of the Backup F-BM . . . . . . . . . . . . . 7
3. Representations for BIER-FRR Forwarding Data . . . . . . . . 7 3. Representations for BIER-FRR Forwarding Data . . . . . . . . 7
3.1. Potential Emergence of Redundant Packets . . . . . . . . 7 3.1. Potential Emergence of Redundant Packets . . . . . . . . 7
3.2. Primary BIFT and Single Backup BIFT . . . . . . . . . . . 9 3.2. Primary BIFT and Single Backup BIFT . . . . . . . . . . . 9
3.3. Primary BIFT and Failure-Specific Backup BIFTs . . . . . 10 3.3. Primary BIFT and Failure-Specific Backup BIFTs . . . . . 10
4. Protection Levels . . . . . . . . . . . . . . . . . . . . . . 11 4. Protection Levels . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Link Protection . . . . . . . . . . . . . . . . . . . . . 11 4.1. Link Protection . . . . . . . . . . . . . . . . . . . . . 11
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would be dropped. BIER traffic can be delivered again only after would be dropped. BIER traffic can be delivered again only after
reconvergence of the routing underlay and recalculation of the BIFT. reconvergence of the routing underlay and recalculation of the BIFT.
Thus, tunneling BIER packets can help to reach the BFR-NBR in case of Thus, tunneling BIER packets can help to reach the BFR-NBR in case of
a link failure by leveraging FRR capabilities of the routing underlay a link failure by leveraging FRR capabilities of the routing underlay
if such mechanisms are available. However, this does not help in if such mechanisms are available. However, this does not help in
case of a node failure. Then, all destinations having the failed case of a node failure. Then, all destinations having the failed
node as BFR-NBR cannot be reached anymore. As BIER carries multicast node as BFR-NBR cannot be reached anymore. As BIER carries multicast
traffic which has often realtime requirements, there is a particular traffic which has often realtime requirements, there is a particular
need to protect BIER traffic against too long outages after failures. need to protect BIER traffic against too long outages after failures.
In this document we propose nomenclature for Fast Reroute Extensions In this document we propose nomenclature for Fast Reroute in BIER
for BIER (BIER-FRR). As soon as a BFR detects a BFR-NBR is (BIER-FRR). As soon as a BFR detects a BFR-NBR is unreachable, BIER-
unreachable, BIER-FRR enables a BFR to quickly reroute affected BIER FRR enables a BFR to quickly reroute affected BIER packets with the
packets with the help of backup forwarding entries. To avoid help of backup forwarding entries. To avoid redundant packets,
redundant packets, backup forwarding entries should be processed backup forwarding entries should be processed prior to normal
prior to normal forwarding entries. To achieve that goal, two forwarding entries. To achieve that goal, two possible
possible representations for backup forwarding entries are proposed. representations for backup forwarding entries are proposed.
The protection level can be either link protection or node The protection level can be either link protection or node
protection. Link protection protects only the failure of a link. It protection. Link protection protects only the failure of a link. It
is simple but may not work if a BFR fails. Node protection is more is simple but may not work if a BFR fails. Node protection is more
complex but also protects against the failure of BFRs. The backup complex but also protects against the failure of BFRs. The backup
strategy determines the selection of the backup forwarding entries. strategy determines the selection of the backup forwarding entries.
Examples for backup strategies are tunnel-based BIER-FRR and LFA- Examples for backup strategies are tunnel-based BIER-FRR and LFA-
based BIER-FRR based BIER-FRR
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topology-independent BIER-LFAs leverage explicit paths to reach topology-independent BIER-LFAs leverage explicit paths to reach
the backup BFR-NBR. In contrast to tunnel-based FRR, LFA-based the backup BFR-NBR. In contrast to tunnel-based FRR, LFA-based
BIER-FRR does not require fast reroute mechanisms in the routing BIER-FRR does not require fast reroute mechanisms in the routing
underlay. underlay.
BIER-FRR as presented in this document follows a primary/backup path BIER-FRR as presented in this document follows a primary/backup path
principle, also known as 1:1 protection. It is opposite to 1+1 principle, also known as 1:1 protection. It is opposite to 1+1
protection which denotes a live-live protection principle. This has protection which denotes a live-live protection principle. This has
been considered for BIER in [BrAl17]. been considered for BIER in [BrAl17].
2. Extensions for BIER-FRR 2. Definition of BIER-FRR
In this section, forwarding actions and backup forwarding entries are In this section, forwarding actions and backup forwarding entries are
defined. Then, the computation of the backup F-BM and the BIER defined. Then, the BIER forwarding process with BIER-FRR and the
forwarding process with BIER-FRR are explained. computation of the backup F-BM are explained.
2.1. Definition of Forwarding Actions 2.1. Definition of Forwarding Actions
A BFR-NBR is directly connected if it is a next hop on the network A BFR-NBR is directly connected if it is a next hop on the network
layer, i.e., if it can be reached via the link layer technology. layer, i.e., if it can be reached via the link layer technology.
Otherwise, the BFR-NBR is indirectly connected. Otherwise, the BFR-NBR is indirectly connected.
We define the following forwarding actions. We define the following forwarding actions.
o Plain: Sends the mere BIER packet to a BFR-NBR via a direct link o Plain: Sends the mere BIER packet to a BFR-NBR via a direct link
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[I-D.chen-bier-egress-protect] [I-D.chen-bier-egress-protect]
Chen, H., McBride, M., Wang, A., Mishra, G. S., Liu, Y., Chen, H., McBride, M., Wang, A., Mishra, G. S., Liu, Y.,
Menth, M., Khasanov, B., Geng, X., Fan, Y., Liu, L., and Menth, M., Khasanov, B., Geng, X., Fan, Y., Liu, L., and
X. Liu, "BIER Egress Protection", draft-chen-bier-egress- X. Liu, "BIER Egress Protection", draft-chen-bier-egress-
protect-03 (work in progress), October 2021. protect-03 (work in progress), October 2021.
[I-D.ietf-rtgwg-segment-routing-ti-lfa] [I-D.ietf-rtgwg-segment-routing-ti-lfa]
Litkowski, S., Bashandy, A., Filsfils, C., Francois, P., Litkowski, S., Bashandy, A., Filsfils, C., Francois, P.,
Decraene, B., and D. Voyer, "Topology Independent Fast Decraene, B., and D. Voyer, "Topology Independent Fast
Reroute using Segment Routing", draft-ietf-rtgwg-segment- Reroute using Segment Routing", draft-ietf-rtgwg-segment-
routing-ti-lfa-07 (work in progress), June 2021. routing-ti-lfa-08 (work in progress), January 2022.
[MeLi20b] Merling, D., Lindner, S., and M. Menth, "P4-Based [MeLi20b] Merling, D., Lindner, S., and M. Menth, "P4-Based
Implementation of BIER and BIER-FRR for Scalable and Implementation of BIER and BIER-FRR for Scalable and
Resilient Multicast", November 2020. Resilient Multicast", November 2020.
[MeLi21] Merling, D., Lindner, S., and M. Menth, "Hardware-based [MeLi21] Merling, D., Lindner, S., and M. Menth, "Hardware-based
Evaluation of Scalable and Resilient Multicast with BIER Evaluation of Scalable and Resilient Multicast with BIER
in P4", March 2020. in P4", March 2020.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast [RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
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