draft-ietf-bess-mvpn-fast-failover-05.txt   draft-ietf-bess-mvpn-fast-failover-06.txt 
Network Working Group T. Morin, Ed. Network Working Group T. Morin, Ed.
Internet-Draft Orange Internet-Draft Orange
Intended status: Standards Track R. Kebler, Ed. Intended status: Standards Track R. Kebler, Ed.
Expires: August 18, 2019 Juniper Networks Expires: January 3, 2020 Juniper Networks
G. Mirsky, Ed. G. Mirsky, Ed.
ZTE Corp. ZTE Corp.
February 14, 2019 July 2, 2019
Multicast VPN fast upstream failover Multicast VPN fast upstream failover
draft-ietf-bess-mvpn-fast-failover-05 draft-ietf-bess-mvpn-fast-failover-06
Abstract Abstract
This document defines multicast VPN extensions and procedures that This document defines multicast VPN extensions and procedures that
allow fast failover for upstream failures, by allowing downstream PEs allow fast failover for upstream failures, by allowing downstream PEs
to take into account the status of Provider-Tunnels (P-tunnels) when to take into account the status of Provider-Tunnels (P-tunnels) when
selecting the upstream PE for a VPN multicast flow, and extending BGP selecting the upstream PE for a VPN multicast flow, and extending BGP
MVPN routing so that a C-multicast route can be advertised toward a MVPN routing so that a C-multicast route can be advertised toward a
standby upstream PE. standby upstream PE.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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 August 18, 2019. This Internet-Draft will expire on January 3, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. UMH Selection based on tunnel status . . . . . . . . . . . . 3 3. UMH Selection based on tunnel status . . . . . . . . . . . . 3
3.1. Determining the status of a tunnel . . . . . . . . . . . 4 3.1. Determining the status of a tunnel . . . . . . . . . . . 5
3.1.1. mVPN tunnel root tracking . . . . . . . . . . . . . . 5 3.1.1. mVPN tunnel root tracking . . . . . . . . . . . . . . 5
3.1.2. PE-P Upstream link status . . . . . . . . . . . . . . 5 3.1.2. PE-P Upstream link status . . . . . . . . . . . . . . 5
3.1.3. P2MP RSVP-TE tunnels . . . . . . . . . . . . . . . . 5 3.1.3. P2MP RSVP-TE tunnels . . . . . . . . . . . . . . . . 6
3.1.4. Leaf-initiated P-tunnels . . . . . . . . . . . . . . 6 3.1.4. Leaf-initiated P-tunnels . . . . . . . . . . . . . . 6
3.1.5. (C-S, C-G) counter information . . . . . . . . . . . 6 3.1.5. (C-S, C-G) counter information . . . . . . . . . . . 6
3.1.6. BFD Discriminator . . . . . . . . . . . . . . . . . . 6 3.1.6. BFD Discriminator . . . . . . . . . . . . . . . . . . 7
3.1.7. Per PE-CE link BFD Discriminator . . . . . . . . . . 9 3.1.7. Per PE-CE link BFD Discriminator . . . . . . . . . . 9
4. Standby C-multicast route . . . . . . . . . . . . . . . . . . 10 4. Standby C-multicast route . . . . . . . . . . . . . . . . . . 10
4.1. Downstream PE behavior . . . . . . . . . . . . . . . . . 11 4.1. Downstream PE behavior . . . . . . . . . . . . . . . . . 11
4.2. Upstream PE behavior . . . . . . . . . . . . . . . . . . 12 4.2. Upstream PE behavior . . . . . . . . . . . . . . . . . . 12
4.3. Reachability determination . . . . . . . . . . . . . . . 13 4.3. Reachability determination . . . . . . . . . . . . . . . 13
4.4. Inter-AS . . . . . . . . . . . . . . . . . . . . . . . . 13 4.4. Inter-AS . . . . . . . . . . . . . . . . . . . . . . . . 13
4.4.1. Inter-AS procedures for downstream PEs, ASBR fast 4.4.1. Inter-AS procedures for downstream PEs, ASBR fast
failover . . . . . . . . . . . . . . . . . . . . . . 14 failover . . . . . . . . . . . . . . . . . . . . . . 14
4.4.2. Inter-AS procedures for ASBRs . . . . . . . . . . . . 14 4.4.2. Inter-AS procedures for ASBRs . . . . . . . . . . . . 14
5. Hot leaf standby . . . . . . . . . . . . . . . . . . . . . . 15 5. Hot Root Standby . . . . . . . . . . . . . . . . . . . . . . 15
6. Duplicate packets . . . . . . . . . . . . . . . . . . . . . . 15 6. Duplicate packets . . . . . . . . . . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
10. Contributor Addresses . . . . . . . . . . . . . . . . . . . . 16 10. Contributor Addresses . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Normative References . . . . . . . . . . . . . . . . . . 18 11.1. Normative References . . . . . . . . . . . . . . . . . . 18
11.2. Informative References . . . . . . . . . . . . . . . . . 19 11.2. Informative References . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
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The terminology used in this document is the terminology defined in The terminology used in this document is the terminology defined in
[RFC6513] and [RFC6514]. [RFC6513] and [RFC6514].
x-PMSI: I-PMSI or S-PMSI x-PMSI: I-PMSI or S-PMSI
3. UMH Selection based on tunnel status 3. UMH Selection based on tunnel status
Current multicast VPN specifications [RFC6513], section 5.1, describe Current multicast VPN specifications [RFC6513], section 5.1, describe
the procedures used by a multicast VPN downstream PE to determine the procedures used by a multicast VPN downstream PE to determine
what the upstream multicast hop (UMH) is for a given (C-S,C-G). what the upstream multicast hop (UMH) is for a given (C-S, C-G).
The procedure described here is an OPTIONAL procedure that consists The procedure described here is an OPTIONAL procedure that consists
of having a downstream PE take into account the status of P-tunnels of having a downstream PE take into account the status of P-tunnels
rooted at each possible upstream PEs, for including or not including rooted at each possible upstream PEs, for including or not including
each given PE in the list of candidate UMHs for a given (C-S,C-G) each given PE in the list of candidate UMHs for a given (C-S, C-G)
state. The result is that, if a P-tunnel is "down" (see state. The result is that, if a P-tunnel is "down" (see
Section 3.1), the PE that is the root of the P-tunnel will not be Section 3.1), the PE that is the root of the P-tunnel will not be
considered for UMH selection, which will result in the downstream PE considered for UMH selection, which will result in the downstream PE
to failover to the upstream PE which is next in the list of to failover to the upstream PE which is next in the list of
candidates. If rules to determine the state of the P-tunnel are not candidates. Because all PEs could arrive at a different conclusion
consistent across all PEs, then some may arrive at a different regarding the state of the tunnel, procedures described in
conclusion regarding the state of the tunnel, In such a scenario, Section 9.1.1 of [RFC6513] MUST be used when using inclusive tunnels.
procedures described in Section 9.1.1 of [RFC6513] MUST be used.
A downstream PE monitors the status of the tunnels of UMHs that are A downstream PE monitors the status of the tunnels of UMHs that are
ahead of the current one. Whenever the downstream PE determines that ahead of the current one. Whenever the downstream PE determines that
one of these tunnels is no longer "known to down", the PE selects the one of these tunnels is no longer "known to down", the PE selects the
UMH corresponding to that as the new UMH. UMH corresponding to that as the new UMH.
More precisely, UMH determination for a given (C-S,C-G) will consider More precisely, UMH determination for a given (C-S, C-G) will
the UMH candidates in the following order: consider the UMH candidates in the following order:
o first, the UMH candidates that either (a) advertise a PMSI bound o First, the UMH candidates that either
to a tunnel, where the specified tunnel is not known to be down or
(b) do not advertise any x-PMSI applicable to the given (C-S,C-G)
but have associated a VRF Route Import BGP attribute to the
unicast VPN route for S (this is necessary to avoid incorrectly
invalidating an UMH PE that would use a policy where no I-PMSI is
advertised for a given VRF and where only S-PMSI are used, the
S-PMSI advertisement being possibly done only after the upstream
PE receives a C-multicast route for (C-S, C-G)/(C-*, C-G) to be
carried over the advertised S-PMSI)
o second, the UMH candidates that advertise a PMSI bound to a tunnel A. advertise a PMSI bound to a tunnel, where the specified tunnel
is not known to be down or
B. do not advertise any x-PMSI applicable to the given (C-S, C-G)
but have associated a VRF Route Import BGP attribute to the
unicast VPN route for S (this is necessary to avoid
incorrectly invalidating a UMH PE that would use a policy
where no I-PMSI is advertised for a given VRF and where only
S-PMSI are used, the S-PMSI advertisement being possibly done
only after the upstream PE receives a C-multicast route for
(C-S, C-G)/(C-*, C-G) to be carried over the advertised
S-PMSI).
o Second, the PE advertising the next best route is to be
considered.
o Third, the UMH candidates that advertise a PMSI bound to a tunnel
that is "down" -- these will thus be used as a last resort to that is "down" -- these will thus be used as a last resort to
ensure a graceful fallback to the basic MVPN UMH selection ensure a graceful fallback to the basic MVPN UMH selection
procedures in the hypothetical case where a false negative would procedures in the hypothetical case where a false negative would
occur when determining the status of all tunnels occur when determining the status of all tunnels.
For a given downstream PE and a given VRF, the P-tunnel corresponding For a given downstream PE and a given VRF, the P-tunnel corresponding
to a given upstream PE for a given (C-S,C-G) state is the S-PMSI to a given upstream PE for a given (C-S, C-G) state is the S-PMSI
tunnel advertised by that upstream PE for this (C-S,C-G) and imported tunnel advertised by that upstream PE for this (C-S, C-G) and
into that VRF, or if there isn't any such S-PMSI, the I-PMSI tunnel imported into that VRF, or if there isn't any such S-PMSI, the I-PMSI
advertised by that PE and imported into that VRF. tunnel advertised by that PE and imported into that VRF.
Note that this document assumes that if a site of a given MVPN that Note that this document assumes that if a site of a given MVPN that
contains C-S is dual-homed to two PEs, then all the other sites of contains C-S is dual-homed to two PEs, then all the other sites of
that MVPN would have two unicast VPN routes (VPN-IPv4 or VPN-IPv6) that MVPN would have two unicast VPN routes (VPN-IPv4 or VPN-IPv6)
routes to C-S, each with its own RD. routes to C-S, each with its RD.
3.1. Determining the status of a tunnel 3.1. Determining the status of a tunnel
Different factors can be considered to determine the "status" of a Different factors can be considered to determine the "status" of a
P-tunnel and are described in the following sub-sections. The P-tunnel and are described in the following sub-sections. The
optional procedures proposed in this section also allow that all optional procedures proposed in this section also allow that all
downstream PEs don't apply the same rules to define what the status downstream PEs don't apply the same rules to define what the status
of a P-tunnel is (please see Section 6), and some of them will of a P-tunnel is (please see Section 6), and some of them will
produce a result that may be different for different downstream PEs. produce a result that may be different for different downstream PEs.
Thus what is called the "status" of a P-tunnel in this section, is Thus what is called the "status" of a P-tunnel in this section, is
not a characteristic of the tunnel in itself, but is the status of not a characteristic of the tunnel in itself, but is the status of
the tunnel, *as seen from a particular downstream PE*. Additionally, the tunnel, *as seen from a particular downstream PE*. Additionally,
some of the following methods determine the ability of downstream PE some of the following methods determine the ability of downstream PE
to receive traffic on the P-tunnel and not specifically on the status to receive traffic on the P-tunnel and not specifically on the status
of the P-tunnel itself. This could be referred to as "P-tunnel of the P-tunnel itself. That could be referred to as "P-tunnel
reception status", but for simplicity, we will use the terminology of reception status", but for simplicity, we will use the terminology of
P-tunnel "status" for all of these methods. P-tunnel "status" for all of these methods.
Depending on the criteria used to determine the status of a P-tunnel, Depending on the criteria used to determine the status of a P-tunnel,
there may be an interaction with another resiliency mechanism used there may be an interaction with another resiliency mechanism used
for the P-tunnel itself, and the UMH update may happen immediately or for the P-tunnel itself, and the UMH update may happen immediately or
may need to be delayed. Each particular case is covered in each may need to be delayed. Each particular case is covered in each
separate sub-section below. separate sub-section below.
3.1.1. mVPN tunnel root tracking 3.1.1. mVPN tunnel root tracking
A condition to consider that the status of a P-tunnel is up is that A condition to consider that the status of a P-tunnel is up is that
the root of the tunnel, as determined in the PMSI tunnel attribute, the root of the tunnel, as determined in the PMSI tunnel attribute,
is reachable through unicast routing tables. In this case, the is reachable through unicast routing tables. In this case, the
downstream PE can immediately update its UMH when the reachability downstream PE can immediately update its UMH when the reachability
condition changes. condition changes.
This is similar to BGP next-hop tracking for VPN routes, except that That is similar to BGP next-hop tracking for VPN routes, except that
the address considered is not the BGP next-hop address, but the root the address considered is not the BGP next-hop address, but the root
address in the PMSI tunnel attribute. address in the PMSI tunnel attribute.
If BGP next-hop tracking is done for VPN routes and the root address If BGP next-hop tracking is done for VPN routes and the root address
of a given tunnel happens to be the same as the next-hop address in of a given tunnel happens to be the same as the next-hop address in
the BGP auto-discovery route advertising the tunnel, then this the BGP auto-discovery route advertising the tunnel, then this
mechanisms may be omitted for this tunnel, as it will not bring any mechanisms may be omitted for this tunnel, as it will not bring any
specific benefit. specific benefit.
3.1.2. PE-P Upstream link status 3.1.2. PE-P Upstream link status
A condition to consider a tunnel status as Up can be that the last- A condition to consider a tunnel status as Up can be that the last-
hop link of the P-tunnel is up. hop link of the P-tunnel is up.
This method should not be used when there is a fast restoration This method should not be used when there is a fast restoration
mechanism (such as MPLS FRR [RFC4090]) in place for the link. mechanism (such as MPLS FRR [RFC4090]) in place for the link.
3.1.3. P2MP RSVP-TE tunnels 3.1.3. P2MP RSVP-TE tunnels
For P-tunnels of type P2MP MPLS-TE, the status of the P-tunnel is For P-tunnels of type P2MP MPLS-TE, the status of the P-tunnel is
considered up if one or more of the P2MP RSVP-TE LSPs, identified by considered up if the sub-LSP to this downstream PE is in Up state.
the P-tunnel Attribute, are in Up state. The determination of The determination of whether a P2MP RSVP-TE LSP is in Up state
whether a P2MP RSVP-TE LSP is in Up state requires Path and Resv requires Path and Resv state for the LSP and is based on procedures
state for the LSP and is based on procedures in [RFC4875]. In this specified in [RFC4875]. In this case, the downstream PE can
case, the downstream PE can immediately update its UMH when the immediately update its UMH when the reachability condition changes.
reachability condition changes.
When signaling state for a P2MP TE LSP is removed (e.g. if the When signaling state for a P2MP TE LSP is removed (e.g., if the
ingress of the P2MP TE LSP sends a PathTear message) or the P2MP TE ingress of the P2MP TE LSP sends a PathTear message) or the P2MP TE
LSP changes state from Up to Down as determined by procedures in LSP changes state from Up to Down as determined by procedures in
[RFC4875], the status of the corresponding P-tunnel SHOULD be re- [RFC4875], the status of the corresponding P-tunnel SHOULD be re-
evaluated. If the P-tunnel transitions from up to Down state, the evaluated. If the P-tunnel transitions from up to Down state, the
upstream PE, that is the ingress of the P-tunnel, SHOULD NOT be upstream PE that is the ingress of the P-tunnel SHOULD NOT be
considered a valid UMH. considered a valid UMH.
3.1.4. Leaf-initiated P-tunnels 3.1.4. Leaf-initiated P-tunnels
A PE can be removed from the UMH candidate list for a given (C-S, A PE can be removed from the UMH candidate list for a given (C-S,
C-G) if the P-tunnel (I or S , depending) for this (S, G) is leaf C-G) if the P-tunnel (I or S, depending) for this (S, G) is leaf
triggered (PIM, mLDP), but for some reason internal to the protocol triggered (PIM, mLDP), but for some reason internal to the protocol
the upstream one-hop branch of the tunnel from P to PE cannot be the upstream one-hop branch of the tunnel from P to PE cannot be
built. In this case, the downstream PE can immediately update its built. In this case, the downstream PE can immediately update its
UMH when the reachability condition changes. UMH when the reachability condition changes.
3.1.5. (C-S, C-G) counter information 3.1.5. (C-S, C-G) counter information
In cases, where the downstream node can be configured so that the In cases, where the downstream node can be configured so that the
maximum inter-packet time is known for all the multicast flows mapped maximum inter-packet time is known for all the multicast flows mapped
on a P-tunnel, the local per-(C-S,C-G) traffic counter information on a P-tunnel, the local per-(C-S, C-G) traffic counter information
for traffic received on this P-tunnel can be used to determine the for traffic received on this P-tunnel can be used to determine the
status of the P-tunnel. status of the P-tunnel.
When such a procedure is used, in the context where fast restoration When such a procedure is used, in the context where fast restoration
mechanisms are used for the P-tunnels, downstream PEs should be mechanisms are used for the P-tunnels, downstream PEs should be
configured to wait before updating the UMH, to let the P-tunnel configured to wait before updating the UMH, to let the P-tunnel
restoration mechanism happen. A configurable timer MUST be provided restoration mechanism happen. A configurable timer MUST be provided
for this purpose, and it is recommended to provide a reasonable for this purpose, and it is recommended to provide a reasonable
default value for this timer. default value for this timer.
This method can be applicable, for instance, when a (C-S, C-G) flow This method can be applicable, for instance, when a (C-S, C-G) flow
is mapped on an S-PMSI. is mapped on an S-PMSI.
In cases where this mechanism is used in conjunction with In cases where this mechanism is used in conjunction with
Hot leaf standby, then no prior knowledge of the rate of the Hot Root Standby, no prior knowledge of the rate of the multicast
multicast streams is required; downstream PEs can compare reception streams is required; downstream PEs can compare reception on the two
on the two P-tunnels to determine when one of them is down. P-tunnels to determine when one of them is down.
3.1.6. BFD Discriminator 3.1.6. BFD Discriminator
P-tunnel status can be derived from the status of a multipoint BFD P-tunnel status can be derived from the status of a multipoint BFD
session [I-D.ietf-bfd-multipoint] whose discriminator is advertised session [RFC8562] whose discriminator is advertised along with an
along with an x-PMSI A-D route. x-PMSI A-D route.
This document defines the format and ways of using a new BGP This document defines the format and ways of using a new BGP
attribute called the "BGP- BFD attribute". This is an optional attribute called the "BGP- BFD attribute". It is an optional
transitive BGP attribute. The format of this attribute is defined as transitive BGP attribute. The format of this attribute is defined as
follows: follows:
+-------------------------------+ +-------------------------------+
| Flags (1 octet) | | Flags (1 octet) |
+-------------------------------+ +-------------------------------+
| BFD Discriminator (4 octets) | | BFD Discriminator (4 octets) |
+-------------------------------+ +-------------------------------+
The Flags field has the following format: The Flags field has the following format:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| reserved | | reserved |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
3.1.6.1. Upstream PE Procedures 3.1.6.1. Upstream PE Procedures
When it is desired to track the P-tunnel status using p2mp BFD When it is desired to track the P-tunnel status using a p2mp BFD
session, the Upstream PE: session, the Upstream PE:
o MUST initiate BFD session and set bfd.SessionType = MultipointHead o MUST initiate BFD session and set bfd.SessionType = MultipointHead
as described in [I-D.ietf-bfd-multipoint]; as described in [RFC8562];
o MUST use address in 127.0.0.0/8 range for IPv4 or in o MUST use an address in 127.0.0.0/8 range for IPv4 or in
0:0:0:0:0:FFFF:7F00:0/104 range for IPv6 as destination IP address 0:0:0:0:0:FFFF:7F00:0/104 range for IPv6 as destination IP address
when transmitting BFD control packets; when transmitting BFD control packets;
o MUST use the IP address of the Upstream PE as source IP address o MUST use the IP address of the Upstream PE as source IP address
when transmitting BFD control packets; when transmitting BFD control packets;
o MUST include the BGP-BFD Attribute in the x-PMSI A-D Route with o MUST include the BGP-BFD Attribute in the x-PMSI A-D Route with
BFD Discriminator value set to My Discriminator value; BFD Discriminator value set to My Discriminator value;
o MUST periodically transmit BFD control packets over the x-PMSI o MUST periodically transmit BFD control packets over the x-PMSI
tunnel. tunnel.
If tracking of the P-tunnel by using a p2mp BFD session is to be If the tracking of the P-tunnel by using a p2mp BFD session is
enabled after the P-tunnel has been already signaled, then the enabled after the x-PMSI A-D route has been already advertised, the
procedure described above MUST be followed. Note that x-PMSI A-D x-PMSI A-D Route MUST be re-sent with precisely the same attributes
Route MUST be re-sent with exactly the same attributes as before and as before and the BGP-BFD Attribute included.
the BGP-BFD Attribute included.
If P-tunnel is already signaled, and P-tunnel status tracked using If the x-PMSI A-D route is advertised with P-tunnel status tracked
the p2mp BFD session and it is desired to stop tracking P-tunnel using the p2mp BFD session and it is desired to stop tracking
status using BFD, then: P-tunnel status using BFD, then:
o x-PMSI A-D Route MUST be re-sent with exactly the same attributes o x-PMSI A-D Route MUST be re-sent with precisely the same
as before, but the BGP-BFD Attribute MUST be excluded; attributes as before, but the BGP-BFD Attribute MUST be excluded;
o the p2mp BFD session SHOULD be deleted. o the p2mp BFD session SHOULD be deleted.
3.1.6.2. Downstream PE Procedures 3.1.6.2. Downstream PE Procedures
Upon receiving the BGP-BFD Attribute in the x-PMSI A-D Route, the Upon receiving the BGP-BFD Attribute in the x-PMSI A-D Route, the
Downstream PE: Downstream PE:
o MUST associate the received BFD discriminator value with the o MUST associate the received BFD discriminator value with the
P-tunnel originating from the Root PE and the IP address of the P-tunnel originating from the Root PE and the IP address of the
Upstream PE; Upstream PE;
o MUST create p2mp BFD session and set bfd.SessionType = o MUST create p2mp BFD session and set bfd.SessionType =
MultipointTail as described in [I-D.ietf-bfd-multipoint]; MultipointTail as described in [RFC8562];
o MUST use the source IP address of the BFD control packet, the o MUST use the source IP address of the BFD control packet, the
value of the BFD Discriminator field, and the x-PMSI tunnel value of the BFD Discriminator field, and the x-PMSI tunnel
identifier the BFD control packet was received to properly identifier the BFD control packet was received to properly
demultiplex BFD sessions. demultiplex BFD sessions.
After the state of the p2mp BFD session is up, i.e., bfd.SessionState After the state of the p2mp BFD session is up, i.e., bfd.SessionState
== Up, the session state will then be used to track the health of the == Up, the session state will then be used to track the health of the
P-tunnel. P-tunnel.
According to [I-D.ietf-bfd-multipoint], if the Downstream PE receives According to [RFC8562], if the Downstream PE receives Down or
Down or AdminDown in the State field of the BFD control packet or AdminDown in the State field of the BFD control packet or associated
associated with the BFD session Detection Timer expires, the BFD with the BFD session Detection Timer expires, the BFD session state
session state is down, i.e., bfd.SessionState == Down. When the BFD is down, i.e., bfd.SessionState == Down. When the BFD session state
session state is Down, then the P-tunnel associated with the BFD is Down, then the P-tunnel associated with the BFD session as down
session as down MUST be declared down. Then The Downstream PE MAY MUST be declared down. Then The Downstream PE MAY initiate a
initiate a switchover of the traffic from the Primary Upstream PE to switchover of the traffic from the Primary Upstream PE to the Standby
the Standby Upstream PE only if the Standby Upstream PE deemed Upstream PE only if the Standby Upstream PE deemed available. A
available. A different p2mp BFD session MAY monitor the state of the different p2mp BFD session MAY monitor the state of the Standby
Standby Upstream PE. Upstream PE.
If the Downstream PE's P-tunnel is already up when the Downstream PE If the Downstream PE's P-tunnel is already up when the Downstream PE
receives the new x-PMSI A-D Route with BGP-BFD Attribute, the receives the new x-PMSI A-D Route with BGP-BFD Attribute, the
Downstream PE MUST accept the x-PMSI A-D Route and associate the Downstream PE MUST accept the x-PMSI A-D Route and associate the
value of BFD Discriminator field with the P-tunnel. The Upstream PE value of BFD Discriminator field with the P-tunnel. The Upstream PE
MUST follow procedures listed above in this section to bring the p2mp MUST follow procedures listed above in this section to bring the p2mp
BFD session up and use it to monitor the state of the associated BFD session up and use it to monitor the state of the associated
P-tunnel. P-tunnel.
If the Downstream PE's P-tunnel is already up, its state being If the Downstream PE's P-tunnel is already up, its state being
monitored by the p2mp BFD session, and the Downstream PE receives the monitored by the p2mp BFD session, and the Downstream PE receives the
new x-PMSI A-D Route without the BGP-BFD Attribute, the Downstream new x-PMSI A-D Route without the BGP-BFD Attribute, the Downstream
PE: PE:
o MUST accept the x-PMSI A-D Route; o MUST accept the x-PMSI A-D Route;
o MUST stop receiving BFD control packets for this p2mp BFD session; o MUST stop processing BFD control packets for this p2mp BFD
session;
o SHOULD delete the p2mp BFD session associated with the P-tunnel; o SHOULD delete the p2mp BFD session associated with the P-tunnel;
o SHOULD NOT switch the traffic to the Standby Upstream PE. o SHOULD NOT switch the traffic to the Standby Upstream PE.
In such a scenario, in the context where fast restoration mechanisms
are used for the P-tunnels, leaf PEs should be configured to wait
before updating the UMH, to let the P-tunnel restoration mechanism
happen. A configurable timer MUST be provided for this purpose, and
it is RECOMMENDED to provide a reasonable default value for this
timer.
3.1.7. Per PE-CE link BFD Discriminator 3.1.7. Per PE-CE link BFD Discriminator
The following approach is defined for the fast failover in response The following approach is defined for the fast failover in response
to the detection of PE-CE link failures, in which UMH selection for a to the detection of PE-CE link failures, in which UMH selection for a
given C-multicast route takes into account the state of the BFD given C-multicast route takes into account the state of the BFD
session associated with the state of the upstream PE-CE link. session associated with the state of the upstream PE-CE link.
According to section 6.8.17 [RFC5880], failure of a PE-CE link MAY be
communicated to the downstream PE by setting the bfd.LocalDiag of the
p2mp BFD session associated with this link to Concatenated Path Down
and/or Reverse Concatenated Path Down. The mechanism to communicate
the mapping between the PE-CE link and the associated BFD session is
outside the scope of this document.
3.1.7.1. Upstream PE Procedures 3.1.7.1. Upstream PE Procedures
For each protected PE-CE link, the upstream PE initiates a multipoint For each protected PE-CE link, the upstream PE initiates a multipoint
BFD session [I-D.ietf-bfd-multipoint] as MultipointHead toward BFD session [RFC8562] as MultipointHead toward downstream PEs. A
downstream PEs. A downstream PE monitors the state of the p2mp downstream PE monitors the state of the p2mp session as
session as MultipointTail and MAY interpret transition of the BFD MultipointTail and MAY interpret the transition of the BFD session
session into Down state as the indication of the associated PE-CE into Down state as the indication of the associated PE-CE link being
link being down. down.
For SSM groups, the upstream PE advertises an (C-S, C-G) S-PMSI A-D For SSM groups, the upstream PE advertises a (C-S, C-G) S-PMSI A-D
route or wildcard (S,*) S-PMSI A-D route for each received SSM (C-S, route or wildcard (S,*) S-PMSI A-D route for each received SSM (C-S,
C-G) C-multicast route for which protection is desired. For each ASM C-G) C-multicast route for which protection is desired. For each ASM
(C-S, C-G) C-multicast route for which protection is desired, the (C-S, C-G) C-multicast route for which protection is desired, the
upstream PE advertises a (C-S, C-G) S-PMSI A-D route. For each ASM upstream PE advertises a (C-S, C-G) S-PMSI A-D route. For each ASM
(*,G) C-Multicast route for which protection is desired, the upstream (*, G) C-Multicast route for which protection is desired, the
PE advertises a wildcard (*,G) S-PMSI A-D route. Note that all upstream PE advertises a wildcard (*, G) S-PMSI A-D route. Note that
S-PMSI A-D routes can signal the same P-tunnel, so there is no need all S-PMSI A-D routes can signal the same P-tunnel, so there is no
for a new P-tunnel for each S-PMSI A-D route. Multicast flows for need for a new P-tunnel for each S-PMSI A-D route. Multicast flows
which protection is desired is controlled by configuration/policy on for which protection is desired are controlled by configuration/
the upstream PE. The protected link is the RPF PE-CE interface policy on the upstream PE. The protected link is the RPF PE-CE
towards the src/RP. The upstream PE advertises the BFD Discriminator interface towards the src/RP. The upstream PE advertises the BFD
of the protected link in the S-PMSI A-D route. If the route to the Discriminator of the protected link in the S-PMSI A-D route. If the
src/RP changes such that the RPF interface is changed to be a new PE- route to the src/RP changes such that the RPF interface is changed to
CE interface, then the upstream PE will update the S-PMSI A-D route be a new PE-CE interface, then the upstream PE will update the S-PMSI
with included BGP-BFD Attribute so that the previously advertised A-D route with included BGP-BFD Attribute so that the previously
value of the BFD Discriminator is associated with the new RPF link. advertised value of the BFD Discriminator is associated with the new
RPF link.
3.1.7.2. Downstream PE Procedures 3.1.7.2. Downstream PE Procedures
If an S-PMSI A-D route bound to a given C-multicast is signaled with If an S-PMSI A-D route bound to a given C-multicast is signaled with
a multipoint BFD session, then the upstream PE is considered during a multipoint BFD session, then the upstream PE is considered during
UMH selection for the C-multicast if and only if the corresponding UMH selection for the C-multicast if and only if the corresponding
BFD session is not in state Down, i.e., bfd.SessionState != Down. BFD session is not in state Down, i.e., bfd.SessionState != Down.
Whenever the state of the BFD session changes to Down the Provider Whenever the state of the BFD session changes to Down the Provider
Tunnel will be considered down, and the downstream PE MAY switch to Tunnel will be considered down, and the downstream PE MAY switch to
the backup Provider Tunnel only if the backup Provider Tunnel deemed the backup Provider Tunnel only if the backup Provider Tunnel deemed
skipping to change at page 10, line 41 skipping to change at page 10, line 45
The procedures described below are limited to the case where the site The procedures described below are limited to the case where the site
that contains C-S is connected to two or more PEs though, to simplify that contains C-S is connected to two or more PEs though, to simplify
the description, the case of dual-homing is described. The the description, the case of dual-homing is described. The
procedures require all the PEs of that MVPN to follow the UMH procedures require all the PEs of that MVPN to follow the UMH
selection, as specified in [RFC6513], whether the PE selected based selection, as specified in [RFC6513], whether the PE selected based
on its IP address, hashing algorithm described in section 5.1.3 on its IP address, hashing algorithm described in section 5.1.3
[RFC6513], or Installed UMH Route. The procedures assume that if a [RFC6513], or Installed UMH Route. The procedures assume that if a
site of a given MVPN that contains C-S is dual-homed to two PEs, then site of a given MVPN that contains C-S is dual-homed to two PEs, then
all the other sites of that MVPN would have two unicast VPN routes all the other sites of that MVPN would have two unicast VPN routes
(VPN-IPv4 or VPN-IPv6) routes to C-S, each with its own RD. (VPN-IPv4 or VPN-IPv6) routes to C-S, each with its RD.
As long as C-S is reachable via both PEs, a given downstream PE will As long as C-S is reachable via both PEs, a given downstream PE will
select one of the PEs connected to C-S as its Upstream PE with select one of the PEs connected to C-S as its Upstream PE for C-S.
respect to C-S. We will refer to the other PE connected to C-S as We will refer to the other PE connected to C-S as the "Standby
the "Standby Upstream PE". Note that if the connectivity to C-S Upstream PE". Note that if the connectivity to C-S through the
through the Primary Upstream PE becomes unavailable, then the PE will Primary Upstream PE becomes unavailable, then the PE will select the
select the Standby Upstream PE as its Upstream PE with respect to Standby Upstream PE as its Upstream PE for C-S. When the Primary PE
C-S. When the Primary PE later becomes available, then the PE will later becomes available, then the PE will select the Primary Upstream
select the Primary Upstream PE again as its Upstream PE. This is PE again as its Upstream PE. Such behavior is referred to as
referred to as "revertive" behavior and MUST be supported. Non- "revertive" behavior and MUST be supported. Non-revertive behavior
revertive behavior would refer to the behavior of continuing to would refer to the behavior of continuing to select the backup PE as
select the backup PE as the UMH even after the Primary has come up. the UMH even after the Primary has come up. This non-revertive
This non-revertive behavior can also be optionally supported by an behavior can also be optionally supported by an implementation and
implementation and would be enabled through some configuration. would be enabled through some configuration.
For readability, in the following sub-sections, the procedures are For readability, in the following sub-sections, the procedures are
described for BGP C-multicast Source Tree Join routes, but they apply described for BGP C-multicast Source Tree Join routes, but they apply
equally to BGP C-multicast Shared Tree Join routes failover for the equally to BGP C-multicast Shared Tree Join routes failover for the
case where the customer RP is dual-homed (substitute "C-RP" to case where the customer RP is dual-homed (substitute "C-RP" to
"C-S"). "C-S").
4.1. Downstream PE behavior 4.1. Downstream PE behavior
When a (downstream) PE connected to some site of an MVPN needs to When a (downstream) PE connected to some site of an MVPN needs to
send a C-multicast route (C-S, C-G), then following the procedures send a C-multicast route (C-S, C-G), then following the procedures
specified in Section "Originating C-multicast routes by a PE" of specified in Section "Originating C-multicast routes by a PE" of
[RFC6514] the PE sends the C-multicast route with RT that identifies [RFC6514] the PE sends the C-multicast route with RT that identifies
the Upstream PE selected by the PE originating the route. As long as the Upstream PE selected by the PE originating the route. As long as
C-S is reachable via the Primary Upstream PE, the Upstream PE is the C-S is reachable via the Primary Upstream PE, and the Upstream PE is
Primary Upstream PE. If C-S is reachable only via the Standby the Primary Upstream PE. If C-S is reachable only via the Standby
Upstream PE, then the Upstream PE is the Standby Upstream PE. Upstream PE, then the Upstream PE is the Standby Upstream PE.
If C-S is reachable via both the Primary and the Standby Upstream PE, If C-S is reachable via both the Primary and the Standby Upstream PE,
then in addition to sending the C-multicast route with an RT that then in addition to sending the C-multicast route with an RT that
identifies the Primary Upstream PE, the PE also originates and sends identifies the Primary Upstream PE, the PE also originates and sends
a C-multicast route with an RT that identifies the Standby Upstream a C-multicast route with an RT that identifies the Standby Upstream
PE. This route, that has the semantics of being a 'standby' PE. This route that has the semantics of being a 'standby'
C-multicast route, is further called a "Standby BGP C-multicast C-multicast route is further called a "Standby BGP C-multicast
route", and is constructed as follows: route", and is constructed as follows:
o the NLRI is constructed as the original C-multicast route, except o the NLRI is constructed as the original C-multicast route, except
that the RD is the same as if the C-multicast route was built that the RD is the same as if the C-multicast route was built
using the standby PE as the UMH (it will carry the RD associated using the standby PE as the UMH (it will carry the RD associated
to the unicast VPN route advertised by the standby PE for S and a to the unicast VPN route advertised by the standby PE for S and a
Route Target derived from the standby PE's UMH route's VRF RT Route Target derived from the standby PE's UMH route's VRF RT
Import EC); Import EC);
o SHOULD carry the "Standby PE" BGP Community (this is a new BGP o SHOULD carry the "Standby PE" BGP Community (this is a new BGP
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community, then preference is given to the one *not* carrying the community, then preference is given to the one *not* carrying the
"Standby PE" attribute. Such a situation can happen when, for "Standby PE" attribute. Such a situation can happen when, for
instance, due to transient unicast routing inconsistencies, two instance, due to transient unicast routing inconsistencies, two
different downstream PEs consider different upstream PEs to be the different downstream PEs consider different upstream PEs to be the
primary one; in that case, without any precaution taken, both primary one; in that case, without any precaution taken, both
upstream PEs would process a standby C-multicast route and possibly upstream PEs would process a standby C-multicast route and possibly
stop forwarding at the same time. For this purpose, routes that stop forwarding at the same time. For this purpose, routes that
carry the "Standby PE" BGP Community MUST have the LOCAL_PREF carry the "Standby PE" BGP Community MUST have the LOCAL_PREF
attribute set to zero. attribute set to zero.
Note that, when a PE advertises such a Standby C-multicast join for Note that, when a PE advertises such a Standby C-multicast join for a
an (C-S, C-G) it must join the corresponding P-tunnel. (C-S, C-G) it must join the corresponding P-tunnel.
If at some later point the local PE determines that C-S is no longer If at some later point the local PE determines that C-S is no longer
reachable through the Primary Upstream PE, the Standby Upstream PE reachable through the Primary Upstream PE, the Standby Upstream PE
becomes the Upstream PE, and the local PE re-sends the C-multicast becomes the Upstream PE, and the local PE re-sends the C-multicast
route with RT that identifies the Standby Upstream PE, except that route with RT that identifies the Standby Upstream PE, except that
now the route does not carry the Standby PE BGP Community (which now the route does not carry the Standby PE BGP Community (which
results in replacing the old route with a new route, with the only results in replacing the old route with a new route, with the only
difference between these routes being the presence/absence of the difference between these routes being the presence/absence of the
Standby PE BGP Community). Standby PE BGP Community). Also, a LOCAL_PREF attribute MUST be set
to zero.
4.2. Upstream PE behavior 4.2. Upstream PE behavior
When a PE receives a C-multicast route for a particular (C-S, C-G), When a PE receives a C-multicast route for a particular (C-S, C-G),
and the RT carried in the route results in importing the route into a and the RT carried in the route results in importing the route into a
particular VRF on the PE, if the route carries the Standby PE BGP particular VRF on the PE, if the route carries the Standby PE BGP
Community, then the PE performs as follows: Community, then the PE performs as follows:
when the PE determines that C-S is not reachable through some when the PE determines that C-S is not reachable through some
other PE, the PE SHOULD install VRF PIM state corresponding to other PE, the PE SHOULD install VRF PIM state corresponding to
this Standby BGP C-multicast route (the result will be that a PIM this Standby BGP C-multicast route (the result will be that a PIM
Join message will be sent to the CE towards C-S, and that the PE Join message will be sent to the CE towards C-S, and that the PE
will receive (C-S,C-G) traffic), and the PE SHOULD forward (C-S, will receive (C-S, C-G) traffic), and the PE SHOULD forward (C-S,
C-G) traffic received by the PE to other PEs through a P-tunnel C-G) traffic received by the PE to other PEs through a P-tunnel
rooted at the PE. rooted at the PE.
Furthermore, irrespective of whether C-S carried in that route is Furthermore, irrespective of whether C-S carried in that route is
reachable through some other PE: reachable through some other PE:
a) based on local policy, as soon as the PE receives this Standby BGP a) based on local policy, as soon as the PE receives this Standby BGP
C-multicast route, the PE MAY install VRF PIM state corresponding C-multicast route, the PE MAY install VRF PIM state corresponding
to this BGP Source Tree Join route (the result will be that Join to this BGP Source Tree Join route (the result will be that Join
messages will be sent to the CE toward C-S, and that the PE will messages will be sent to the CE toward C-S, and that the PE will
receive (C-S,C-G) traffic) receive (C-S, C-G) traffic)
b) based on local policy, as soon as the PE receives this Standby BGP b) based on local policy, as soon as the PE receives this Standby BGP
C-multicast route, the PE MAY forward (C-S, C-G) traffic to other C-multicast route, the PE MAY forward (C-S, C-G) traffic to other
PEs through a P-tunnel independently of the reachability of C-S PEs through a P-tunnel independently of the reachability of C-S
through some other PE. [note that this implies also doing (a)] through some other PE. [note that this implies also doing (a)]
Doing neither (a) or (b) for a given (C-S,C-G) is called "cold root Doing neither (a) or (b) for a given (C-S, C-G) is called "cold root
standby". standby".
Doing (a) but not (b) for a given (C-S,C-G) is called "warm root Doing (a) but not (b) for a given (C-S, C-G) is called "warm root
standby". standby".
Doing (b) (which implies also doing (a)) for a given (C-S,C-G) is Doing (b) (which implies also doing (a)) for a given (C-S, C-G) is
called "hot root standby". called "hot root standby".
Note that, if an upstream PE uses an S-PMSI only policy, it shall Note that, if an upstream PE uses an S-PMSI only policy, it shall
advertise an S-PMSI for an (C-S, C-G) as soon as it receives a advertise an S-PMSI for a (C-S, C-G) as soon as it receives a
C-multicast route for (C-S, C-G), normal or Standby; i.e., it shall C-multicast route for (C-S, C-G), normal or Standby; i.e., it shall
not wait for receiving a non-Standby C-multicast route before not wait for receiving a non-Standby C-multicast route before
advertising the corresponding S-PMSI. advertising the corresponding S-PMSI.
Section 9.3.2 of [RFC6514], describes the procedures of sending a Section 9.3.2 of [RFC6514], describes the procedures of sending a
Source-Active A-D result as a result of receiving the C-multicast Source-Active A-D result as a result of receiving the C-multicast
route. These procedures should be followed for both the normal and route. These procedures should be followed for both the normal and
Standby C-multicast routes. Standby C-multicast routes.
4.3. Reachability determination 4.3. Reachability determination
The standby PE can use the following information to determine that The standby PE can use the following information to determine that
C-S can or cannot be reached through the primary PE: C-S can or cannot be reached through the primary PE:
o presence/absence of a unicast VPN route toward C-S o presence/absence of a unicast VPN route toward C-S
o supposing that the standby PE is an egress of the tunnel rooted at o supposing that the standby PE is the egress of the tunnel rooted
the Primary PE, the standby PE can determine the reachability of at the Primary PE, the standby PE can determine the reachability
C-S through the Primary PE based on the status of this tunnel, of C-S through the Primary PE based on the status of this tunnel,
determined thanks to the same criteria as the ones described in determined thanks to the same criteria as the ones described in
Section 3.1 (without using the UMH selection procedures of Section 3.1 (without using the UMH selection procedures of
Section 3); Section 3);
o other mechanisms MAY be used. o other mechanisms MAY be used.
4.4. Inter-AS 4.4. Inter-AS
If the non-segmented inter-AS approach is used, the procedures in If the non-segmented inter-AS approach is used, the procedures in
section 4 can be applied. section 4 can be applied.
skipping to change at page 14, line 39 skipping to change at page 14, line 46
4.4.2. Inter-AS procedures for ASBRs 4.4.2. Inter-AS procedures for ASBRs
When an upstream ASBR receives a C-multicast route, and at least one When an upstream ASBR receives a C-multicast route, and at least one
of the RTs of the route matches one of the ASBR Import RT, the ASBR of the RTs of the route matches one of the ASBR Import RT, the ASBR
locates an Inter-AS I-PMSI A-D route whose RD and Source AS matches locates an Inter-AS I-PMSI A-D route whose RD and Source AS matches
the RD and Source AS carried in the C-multicast route. If the match the RD and Source AS carried in the C-multicast route. If the match
is found, and C-multicast route carries the Standby PE BGP Community, is found, and C-multicast route carries the Standby PE BGP Community,
then the ASBR performs as follows: then the ASBR performs as follows:
o if the route was received over iBGP; the route is expected to have o if the route was received over iBGP; the route is expected to have
a LOCAL_PREF attribute set to zero and it should be re-advertised a LOCAL_PREF attribute set to zero, and it should be re-advertised
in eBGP with a MED attribute (MULTI_EXIT_DISC) set to the highest in eBGP with a MED attribute (MULTI_EXIT_DISC) set to the highest
possible value (0xffff) possible value (0xffff)
o if the route was received over eBGP; the route is expected to have o if the route was received over eBGP; the route is expected to have
a MED attribute set of 0xffff and should be re-advertised in iBGP a MED attribute set of 0xffff and should be re-advertised in iBGP
with a LOCAL_PREF attribute set to zero with a LOCAL_PREF attribute set to zero
Other ASBR procedures are applied without modification. Other ASBR procedures are applied without modification.
5. Hot leaf standby 5. Hot Root Standby
The mechanisms defined in sections Section 4 and Section 3 can be The mechanisms defined in sections Section 4 and Section 3 can be
used together as follows. used together as follows.
The principle is that, for a given VRF (or possibly only for a given The principle is that, for a given VRF (or possibly only for a given
C-S,C-G): C-S,C-G):
o downstream PEs advertise a Standby BGP C-multicast route (based on o downstream PEs advertise a Standby BGP C-multicast route (based on
Section 4) Section 4)
o upstream PEs use the "hot standby" optional behavior and thus will o upstream PEs use the "hot standby" optional behavior and thus will
forward traffic for a given multicast state as soon as they have forward traffic for a given multicast state as soon as they have
whether a (primary) BGP C-multicast route or a Standby BGP whether a (primary) BGP C-multicast route or a Standby BGP
C-multicast route for that state (or both) C-multicast route for that state (or both)
o downstream PEs accept traffic from the primary or standby tunnel, o downstream PEs accept traffic from the primary or standby tunnel,
based on the status of the tunnel (based on Section 3) based on the status of the tunnel (based on Section 3)
Other combinations of the mechanisms proposed in Section 4) and Other combinations of the mechanisms proposed in Section 4 and
Section 3 are for further study. Section 3 are for further study.
Note that the same level of protection would be achievable with a Note that the same level of protection would be achievable with a
simple C-multicast Source Tree Join route advertised to both the simple C-multicast Source Tree Join route advertised to both the
primary and secondary upstream PEs (carrying as Route Target extended primary and secondary upstream PEs (carrying as Route Target extended
communities, the values of the VRF Route Import attribute of each VPN communities, the values of the VRF Route Import attribute of each VPN
route from each upstream PEs). The advantage of using the Standby route from each upstream PEs). The advantage of using the Standby
semantic for is that, supposing that downstream PEs always advertise semantic for is that, supposing that downstream PEs always advertise
a Standby C-multicast route to the secondary upstream PE, it allows a Standby C-multicast route to the secondary upstream PE, it allows
to choose the protection level through a change of configuration on to choose the protection level through a change of configuration on
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6. Duplicate packets 6. Duplicate packets
Multicast VPN specifications [RFC6513] impose that a PE only forwards Multicast VPN specifications [RFC6513] impose that a PE only forwards
to CEs the packets coming from the expected upstream PE to CEs the packets coming from the expected upstream PE
(Section 9.1). (Section 9.1).
We highlight the reader's attention to the fact that the respect of We highlight the reader's attention to the fact that the respect of
this part of multicast VPN specifications is especially important this part of multicast VPN specifications is especially important
when two distinct upstream PEs are susceptible to forward the same when two distinct upstream PEs are susceptible to forward the same
traffic on P-tunnels at the same time in the steady state. This will traffic on P-tunnels at the same time in the steady state. That will
be the case when "hot root standby" mode is used (Section 4), and be the case when "hot root standby" mode is used (Section 4), and
which can also be the case if procedures of Section 3 are used and which can also be the case if procedures of Section 3 are used and
(a) the rules determining the status of a tree are not the same on (a) the rules determining the status of a tree are not the same on
two distinct downstream PEs or (b) the rule determining the status of two distinct downstream PEs or (b) the rule determining the status of
a tree depend on conditions local to a PE (e.g. the PE-P upstream a tree depends on conditions local to a PE (e.g., the PE-P upstream
link being up). link being up).
7. IANA Considerations 7. IANA Considerations
Allocation is expected from IANA for the BGP "Standby PE" community. Allocation is expected from IANA for the BGP "Standby PE" community.
(TBC) (TBC)
8. Security Considerations 8. Security Considerations
9. Acknowledgments 9. Acknowledgments
skipping to change at page 18, line 24 skipping to change at page 18, line 24
701 E Middlefield Rd 701 E Middlefield Rd
Mountain View, CA 94043 Mountain View, CA 94043
USA USA
Email: kanwar.singh@alcatel-lucent.com Email: kanwar.singh@alcatel-lucent.com
11. References 11. References
11.1. Normative References 11.1. Normative References
[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.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S. [RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
Yasukawa, Ed., "Extensions to Resource Reservation Yasukawa, Ed., "Extensions to Resource Reservation
Protocol - Traffic Engineering (RSVP-TE) for Point-to- Protocol - Traffic Engineering (RSVP-TE) for Point-to-
Multipoint TE Label Switched Paths (LSPs)", RFC 4875, Multipoint TE Label Switched Paths (LSPs)", RFC 4875,
DOI 10.17487/RFC4875, May 2007, DOI 10.17487/RFC4875, May 2007,
<https://www.rfc-editor.org/info/rfc4875>. <https://www.rfc-editor.org/info/rfc4875>.
[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>.
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <https://www.rfc-editor.org/info/rfc6513>. 2012, <https://www.rfc-editor.org/info/rfc6513>.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
<https://www.rfc-editor.org/info/rfc6514>. <https://www.rfc-editor.org/info/rfc6514>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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>.
11.2. Informative References 11.2. Informative References
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast [RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090, Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
DOI 10.17487/RFC4090, May 2005, DOI 10.17487/RFC4090, May 2005,
<https://www.rfc-editor.org/info/rfc4090>. <https://www.rfc-editor.org/info/rfc4090>.
[RFC7431] Karan, A., Filsfils, C., Wijnands, IJ., Ed., and B. [RFC7431] Karan, A., Filsfils, C., Wijnands, IJ., Ed., and B.
Decraene, "Multicast-Only Fast Reroute", RFC 7431, Decraene, "Multicast-Only Fast Reroute", RFC 7431,
DOI 10.17487/RFC7431, August 2015, DOI 10.17487/RFC7431, August 2015,
 End of changes. 62 change blocks. 
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