Internet DRAFT - draft-xiong-bier-resilience
draft-xiong-bier-resilience
BIER WG Quan Xiong
Internet-Draft Greg Mirsky
Intended status: Informational ZTE Corporation
Expires: September 7, 2019 Fangwei Hu
Individual
March 6, 2019
The Resilience for BIER
draft-xiong-bier-resilience-02.txt
Abstract
Bit Index Explicit Replication (BIER) is an architecture for the
forwarding of multicast data packets. In some scenarios, the
resilience should be provided to guarantee the multicast data is
protected by a given backup resource and forwarded successfully to
the receivers in BIER-specific network.
This document discusses the resilience use cases, requirements and
proposes solutions for BIER, including the protection and restoration
mechanisms and detection methods.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. BIER Resilience Use Cases . . . . . . . . . . . . . . . . . . 3
2.1. BIER End-to-End 1+1 Protection . . . . . . . . . . . . . 3
2.2. BIER End-to-End Restoration . . . . . . . . . . . . . . . 4
2.3. BIER Link Protection . . . . . . . . . . . . . . . . . . 5
3. Management and Control Considerations . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informational References . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
[RFC8279] defined Bit Index Explicit Replication (BIER) architecture
as a solution for the forwarding of multicast data packets. The
routers which support BIER are known as Bit-Forwarding Router (BFR)
and the multicast data packet enters a BIER domain at a Bit-
Forwarding Ingress Router (BFIR) and leaves at one or more Bit-
Forwarding Egress Routers (BFERs).
[I-D.eckert-bier-te-frr] provides some protection mechanisms for
traffic engineering in a BIER domain. However, there is no mechanism
to protect multicast traffic against BIER-specific network failures.
In some scenarios, the resilience should be provided to guarantee the
multicast data is protected by a given backup resource and forwarded
successfully to the receivers in BIER-specific network.
This document describes the resilience use cases and requirements for
BIER-specific network and discusses the protection and restoration
mechanisms and detection methods.
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1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
1.2. Terminology
The terminology is defined as [RFC8279].
2. BIER Resilience Use Cases
The resilience use cases for a BIER-specific network should be
considered including end-to-end and link protection scenarios. The
protection, restoration, and related detection mechanisms MUST be
provided for BIER resilience against a failure of a link or a node.
2.1. BIER End-to-End 1+1 Protection
The end-to-end protection mechanisms for a BIER-specific network
should be considered in some scenarios like shown in Figure 1. It
includes end-to-end 1+1 protection and restoration use cases. Two
disjoint end-to-end multicast paths that are available for 1+1
protection or restoration from BFIR to BFERs should be provided. One
path could be BFIR->BFR1->BFR2->BFR3->BFER1 and
BFIR->BFR1->BFR2->BFR3->BFER2; and the alternative path is
BFIR->BFR6->BFR5->BFR4->BFER1 and BFIR->BFR6->BFR5->BFR4->BFER2.
+----+ +----+ +----+ +-----+
|BFR1|----|BFR2|-----|BFR3|--------|BFER1|
+----+ +----+ +----+ +-----+
/ \ /
/ \ /
+----+ \ /
|BFIR| \/
+----+ /\
\ / \
\ / \
+----+ +----+ +----+ +-----+
|BFR6|----|BFR5|------|BFR4|------|BFER2|
+----+ +----+ +----+ +-----+
Figure 1: BIER End-to-End Protection and Restoration
For a 1+1 protection scenario, it is referred to as live-live, the
BFIR sends two flows of multicast traffic to all BFERs through the
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disjiont multipoint paths. BFERs need to merge the two flows when no
failure happens. The BFERs MUST monitor and detect multicast
failures and switch from one flow to another when a failure of a flow
is detected.
For example, in a Deterministic Networking (DetNet) service, Packet
Replication Function (PRF) is used in combination with Packet
Elimination Function (PEF) and usually referred to as PREF. PREF is
used in DetNet to lower the packet loss metric and it can be viewed
as an example of live-live terminated within BIER domain. PRF
replicates packets into multiple DetNet member flows and sends them
along multiple different paths to the destinations and PEF eliminates
the duplication based on the failure detection.
The failure detection mechanism for the end-to-end 1+1 protection
scenario MUST be able to monitor and detect multicast failures in
each working path. P2MP BFD [I-D.ietf-bfd-multipoint] MAY be used to
verify multipoint connectivity between a BFIR and a set of BFERs.
[I-D.hu-bier-bfd] describes the use of p2mp BFD in a BIER domain.
End-to-end 1+1 protection provides fast switch but low resource
utilization. All BFERs MAY receive two copies from two paths in the
no-failure scenario and the receivers MUST be able to choose one of
them and eliminate the duplication.
2.2. BIER End-to-End Restoration
This section discusses the end-to-end restoration for BIER. If
duplicate transmission is not desirable for some networks, the
restoration mechanism may be taken into consideration where only one
copy is sent to each receiver. The BFIR will send multicast flows
onto the original path. If the BFIR detects a failure in the
multicast path, the BFIR MAY create and new multicast tree and switch
the multicast flow accordingly.
The failure detection mechanism for end-to-end restoration use case
MUST be enable receivers (tails) to monitor and detect multicast
failures in the multicast tree and notify the head node. BIER-
specific extensions MAY be proposed based on
[I-D.ietf-bfd-multipoint-active-tail]. The P2MP active tail
detection method extends the mechanism defined in
[I-D.ietf-bfd-multipoint]. It allows tails to notify the head of the
failure of the multicast path and can be used in multipoint and
multicast networks, e.g., in BIER domain as described in
[I-D.hu-bier-bfd].
If P2MP BFD uses the active tail mode, then when one of the BFERs
detects the failure, it will send a message to the BFIR. The BFIR
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will create a new multicast path to restore the service and notify
BFERs of switchover and start forwarding the multicast flows over the
restoration path.
2.3. BIER Link Protection
Local protection, i.e., link or node protection, MAY be considered
for BIER domain as an alternative to end-to-end protection. The
nodes which are the BFRs in BIER network and they exchange the
information needed for them to forward packets to each other using
BIER. The node protection MAY be provided by using mechanisms
already existing in the underlay network, for example, described in
[I-D.eckert-bier-te-frr].
A BFR MAY send BIER packets to directly connected BIER neighbors
through a BIER link without requiring a routing underlay. Link
protection SHOULD be considered in BIER domain. The detection of
link failure MAY use the Point-to-Point BFD detection defined in
[RFC5880]. A set of extension for BIER-specific P2P BFD SHOULD be
proposed in further discussion.
As shown in Figure 2, the BIER path from BFIR to BFERs is
BFIR->BFR4->BFR3 ->BFR2->BFER1 and BFIR->BFR4->BFR3->BFER2. If the
BIER link from BFR4 to BFR3 fails, the failure can be protected by
the backup paths over BFR4->BFR1->BFR2 ->BFR3.
+-----+ +-----+ +--+--+
|BFR1 +--------+BFR2 +-------+BFER1|
+--+--+ +--+--+ +--+--+
| |
| |
+--+--+ +--+--+ +--+--+ +--+--+
|BFIR +--------+BFR4 +--------+BFR3 +-------+BFER2|
+--+--+ +-----+ +-----+ +-----+
Figure 2: BIER Link Protection
As discussed in [I-D.eckert-bier-te-frr], the BIER link protection
MAY use the existing RSVP-TE/P2MP or SR tunnel bypass. When a node
detects a failure on a link, it MAY be assumed that the link has
failed and the traffic is switched onto the pre-established backup
path to get packets to the downstream node.
Also, as discussed in [RFC7490], the Topology Independent Loop-free
Alternate Fast Re-route (TI-LFA) Fast Reroute (FRR) approach that
achieves guaranteed coverage against link or node failure in the
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Interior Gateway Protocol (IGP) network MAY be applied in BIER
network.
3. Management and Control Considerations
BIER protection or restoration configuration, including BIER end-to-
end protection, restoration, link/node protection and related
information, MAY be defined and controlled from a centralized
controller or a network management system. A failure detection and
notification mechanism MUST be supported. The fast protection
switching MUST be supported to minimize the loss of BIER packets due
to BIER network failure.
4. Security Considerations
Security aspects of protection in BIER domain may be considered in
relation to the data plane, and handling the dedicated OAM packets
used to detect, signal a failure, coordinate the state in the BIER
protection domain.
5. IANA Considerations
TBD
6. Acknowledgements
Authors would like to thank the comments and suggestions from Jeffrey
(Zhaohui) Zhang.
7. References
7.1. Normative References
[I-D.hu-bier-bfd]
Xiong, Q., Mirsky, G., hu, f., and C. Liu, "BIER BFD",
draft-hu-bier-bfd-03 (work in progress), February 2019.
[I-D.ietf-bfd-multipoint]
Katz, D., Ward, D., Networks, J., and G. Mirsky, "BFD for
Multipoint Networks", draft-ietf-bfd-multipoint-19 (work
in progress), December 2018.
[I-D.ietf-bfd-multipoint-active-tail]
Katz, D., Ward, D., Networks, J., and G. Mirsky, "BFD
Multipoint Active Tails.", draft-ietf-bfd-multipoint-
active-tail-10 (work in progress), November 2018.
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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>.
[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>.
[RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
RFC 7490, DOI 10.17487/RFC7490, April 2015,
<https://www.rfc-editor.org/info/rfc7490>.
[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>.
7.2. Informational References
[I-D.eckert-bier-te-frr]
Eckert, T., Cauchie, G., Braun, W., and M. Menth,
"Protection Methods for BIER-TE", draft-eckert-bier-te-
frr-03 (work in progress), March 2018.
Authors' Addresses
Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Wuhan, Hubei 430223
China
Phone: +86 27 83531060
Email: xiong.quan@zte.com.cn
Greg Mirsky
ZTE Corporation
USA
Email: gregimirsky@gmail.com
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Fangwei Hu
Individual
China
Email: hufwei@gmail.com
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