Network Working Group H. Chen
Internet-Draft M. McBride
Intended status: Standards Track Futurewei
Expires: August 25, 2021 Y. Liu
China Mobile
A. Wang
China Telecom
G. Mishra
Verizon Inc.
Y. Fan
Casa Systems
L. Liu
Fujitsu
X. Liu
Volta Networks
February 21, 2021
BIER-TE Fast ReRoute
draft-chen-bier-te-frr-00
Abstract
This document describes a mechanism for fast re-route (FRR)
protection against the failure of a transit node or link on an
explicit point to multipoint (P2MP) multicast path/tree in a "Bit
Index Explicit Replication" (BIER) Traffic Engineering (TE) domain.
It does not have any per-path state in the core. For a multicast
packet to traverse a transit node along an explicit P2MP path, when
the node fails, its upstream hop node as a PLR reroutes the packet
around the failed node along the P2MP path once it detects the
failure.
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] [RFC8174]
when, and only when, they appear in all capitals, as shown here.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 25, 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of BIER-TE FRR . . . . . . . . . . . . . . . . . . . 4
3. BIER-TE Extensions for BIER-TE FRR . . . . . . . . . . . . . 5
3.1. Extensions to BIER-TE BIFT . . . . . . . . . . . . . . . 5
3.2. Updated Forwarding Procedure . . . . . . . . . . . . . . 6
4. Example Application of BIER-TE FRR . . . . . . . . . . . . . 7
4.1. Example BIER-TE Topology . . . . . . . . . . . . . . . . 7
4.2. BIER-TE BIFT on a BFR . . . . . . . . . . . . . . . . . . 8
4.3. Extended BIER-TE BIFT on a BFR . . . . . . . . . . . . . 10
4.4. Forwarding using Extended BIER-TE BIFT . . . . . . . . . 13
4.4.1. Forwarding in Normal Operations . . . . . . . . . . . 13
4.4.2. Forwarding in Failure . . . . . . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
[I-D.ietf-bier-te-arch] introduces Bit Index Explicit Replication
(BIER) Traffic/Tree Engineering (BIER-TE). It is an architecture for
per-packet stateless explicit point to multipoint (P2MP) multicast
path/tree and based on Bit Index Explicit Replication (BIER)
architecture defined in [RFC8279]. It does not require intermediate
nodes to maintain any per-path/tree state.
[I-D.eckert-bier-te-frr] describes three BIER-TE FRR methods for
providing fast protections against the failure of an intermediate
node or link on an explicit P2MP BIET-TE path. The first method is
Point-to-Point Tunneling (PPT), where a BIER-TE packet is rerouted by
the PLR around the failure to its NHs and NNHs through unicast
tunnels. This method depends on the tunnels, whose configurations
may increase the Opex. The second is BIER-in-BIER Encapsulation
(BBE), where a BIER-TE packet is rerouted by the PLR to its NHs and
NNHs through encapsulating the packet in another BIER-TE header.
This additional header reroutes the packet around the failure towards
its NHs and NNHs and may increase the overhead. The third is Header
Modification (HM), where the backup path is added into the existing
BIER-TE header through using an AddBitmask and a ResetBitmask. The
issue of this method is that it may cause duplicated packets for some
destinations.
This document describes a BIER-TE FRR mechanism without the above
issues. For a multicast packet with a BIER-TE header to traverse a
transit node along an explicit P2MP path, when the node fails, its
upstream hop node as a point of local repair (PLR) reroutes the
packet around the failed node to the next hop nodes of the failed
node on the P2MP path once it detects the failure.
This BIER-TE FRR does not require intermediate nodes to maintain any
per-path state for FRR protection against the failure of a transit
node or link on any explicit P2MP multicast path.
1.1. Terminology
BIER: Bit Index Explicit Replication.
BIER-TE: BIER Traffic/Tree Engineering.
BFR: Bit-Forwarding Router.
BFIR: Bit-Forwarding Ingress Router.
BFER: Bit-Forwarding Egress Router.
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BFR-id: BFR Identifier. It is a number in the range [1,65535].
BFR-NBR: BFR Neighbor.
F-BM: Forwarding Bit Mask.
BFR-prefix: An IP address (either IPv4 or IPv6) of a BFR.
BIRT: Bit Index Routing Table. It is a table that maps from the BFR-
id (in a particular sub-domain) of a BFER to the BFR-prefix of
that BFER, and to the BFR-NBR on the path to that BFER.
BIFT: Bit Index Forwarding Table.
FRR: Fast Re-Route.
PLR: Point of Local Repair.
IGP: Interior Gateway Protocol.
LSDB: Link State DataBase.
SPF: Shortest Path First.
SPT: Shortest Path Tree.
2. Overview of BIER-TE FRR
A Bit-Forwarding Router (BFR) in a BIER-TE domain has a BIER-TE Bit
Index Forwarding Tables (BIFT) [I-D.ietf-bier-te-arch]. A BIER-TE
BIFT on a BFR comprises a forwarding entry for a BitPosition (BP)
assigned to each of the adjacencies of the BFR. If the BP represents
a forward connected adjacency, the forwarding entry for the BP
forwards the multicast packet with the BP to the directly connected
BFR neighbor of the adjacency. If the BP represents a BFER (i.e.,
egress node) or say a local decap adjacency, the forwarding entry for
the BP decapsulates the multicast packet with the BP and passes a
copy of the payload of the packet to the packet's NextProto within
the BFR.
To support BIER-TE FRR (i.e., fast re-route (FRR) protection against
the failure of a transit node or link on an explicit P2MP multicast
path in a BIER-TE domain), the BIER-TE BIFT on a BFR is extended.
For each forwarding entry of the BIER-TE BIFT on the BFR, if it is
for the BP representing a forward connected adjacency, the forwarding
entry is extended to include a new forwarding entry, which is called
FRR forwarding entry or FRR entry for short.
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Suppose that the BFR-NBR in the forwarding entry for the BP is N.
The FRR entry forwards the multicast packet with the BP to the N's
next hops that are on the P2MP path encoded in the multicast packet.
Once the BFR as a PLR detects the failure of its BFR-NBR N that is a
transit node, for a multicast packet with the BP attached to N, the
PLR uses the FRR forwarding entry in the extended BIER-TE BIFT to
send the packet to the N's next hop nodes that are on the P2MP path
encoded in the multicast packet. These next hop nodes forward the
packet along the P2MP path towards the egress nodes of the path.
Before sending the packet to the N's next hops, for any local decap
BP for a destination/BFER in the header, the PLR removes/clears it if
it is on the backup path and it is not reachable through the forward
connected adjacency BPs in the header (i.e., it is not on any branch
from the PLR).
3. BIER-TE Extensions for BIER-TE FRR
This section describes extensions to a BIER-TE BIFT of a BFR for
supporting BIER-TE FRR and enhancements on a forwarding procedure to
use the extended BIER-TE BIFT for BIER-TE FRR.
3.1. Extensions to BIER-TE BIFT
Every BFR has an extended BIER-TE BIFT to support BIER-TE FRR
protection against the failure of its neighbor transit node. The
forwarding entry with transit node (say N) as its BFR-NBR in the BIFT
comprises a FRR forwarding entry (or FRR entry for short). The FRR
entry contains a flag FPA (which is short for FRR Protection is
Active) and a backup path from the BFR to each of N's next hop nodes.
In normal operations, the flag FPA in the FRR entry for neighbor
transit node N is set to 0 (zero). The flag FPA is set to 1 (one)
when transit node N fails. FPA == 1 means that the FRR protection
for transit node N is active and the FRR entry will be used to
forward the packet with the BP for the adjacency from the BFR to node
N towards N's next hop nodes on the P2MP path encoded in the packet's
BitString along the backup paths.
The backup path from the BFR to a N's next hop node X is a path that
satisfies a set of constraints and does not traverse transit node N
or any link connected to N. In one implementation, the backup path
is represented by the BitPositions for the adjacencies along the
backup path.
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3.2. Updated Forwarding Procedure
The forwarding procedure defined in [I-D.ietf-bier-te-arch] is
updated/enhanced for using an extended BIER-TE BIFT to support BIER-
TE FRR.
For a multicast packet with the BP in the BitString indicating a BFR-
NBR as a transit node of the P2MP path encoded in the packet, the
updated forwarding procedure on a BFR sends the packet towards the
transit node's next hop nodes on the P2MP path if the transit node
fails.
It checks whether FPA equals to 1 (one) in the forwarding entry with
the BFR-NBR that is a transit node of the P2MP path. If FPA is 1
(i.e., the transit node fails and the FRR protection for the transit
node is active), the procedure clears the BP for the adjacency to the
transit node in the packet's BitString first. Secondly, for any
local decap BP for a destination/BFER in the BitString, it removes/
clears the BP if the BP is on the backup path and is not reachable by
the forward connected adjacency BPs in the BitString (i.e., is not on
any branch from the BFR as PLR). And then, for each next hop node of
the failed transit node that is on the P2MP path encoded in the
packet's BitString, it copies and sends the packet to the next hop
node along the backup path from the BFR to the next hop node.
For each next hop node of transit node BFR-NBR (which is named as N
for simplicity), when N's next hop node is on the P2MP path, the
forwarding procedure clears the BP for the adjacency from N to the
N's next hop node in the packet's BitString and adds the BPs for the
backup path from the BFR to the N's next hop node. This lets the
packet be copied and sent to the N's next hop nodes along the backup
paths when transit node N fails and then towards the destinations
along the P2MP path.
The updated procedure is described in Figure 1. It can also be used
by the BFR to forward multicast packets in normal operations.
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Packet = the packet received by BFR;
FOR each BP k (from the rightmost in Packet's BitString) {
IF (BP k is local decap adjacency) {
copies Packet, sends the copy to the multicast
flow overlay and clears bit k in Packet's BitString
} ELSE IF (BP k is forward connect adjacency of the BFR) {
finds the forwarding entry in the BIER-TE BIFT for the domain
using BP k;
Clears BP k in Packet's BitString;
IF (FPA == 1) {//FRR for BFR-NBR/transit N is Active
FOR each BP j for a BFER in Packet's BitString {
IF (BP j is on a backup path and
is not reachable by BPs in BitString) {
Clears BP j in Packet's BitString
}
}
FOR each N's next hop on P2MP path in Packet's BitString {
Clears the BP for the adjacency from N to the next hop;
Adds the BPs for the backup path to N's next hop
into Packet's BitString
}
} //Adjacency to N removed, backup path to N's next hop added
ELSE {
Copies Packet, updates the copy's BitString by
clearing all the BPs for the adjacencies of the BFR,
and sends the updated copy to BFR-NBR
}
}
}
Figure 1: Updated Forwarding Procedure
4. Example Application of BIER-TE FRR
This section illustrates an example application of BIER-TE FRR on a
BFR in a BIER-TE topology in Figure 2.
4.1. Example BIER-TE Topology
An example BIER-TE topology for a BIER-TE domain is shown in
Figure 2. It has 9 nodes/BFRs A, B, C, D, E, F, G, H and I. Nodes/
BFRs D, F, E, H and A are BFERs and have local decap adjacency
BitPositions 1, 2, 3, 4, and 5 respectively. For simplicity, these
BPs are represented by (SI:BitString), where SI = 0 and BitString is
of 8 bits. BPs 1, 2, 3, 4, and 5 are represented by 1 (0:00000001),
2 (0:00000010), 3 (0:00000100), 4 (0:00001000) and 5 (0:00010000)
respectively.
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26' 19' 20' 4
/--------------------( G )---------------( H )
/ / 18'\ 16'/|28'
/ 6'/ \17' / |
/ ________/ ( I )____________/ |
25'/ / 14'/ 15' |
/ 5'/ / |
/ 8' 7' / 3' 4' /13' 12' |27'
( A )--------( B )------------( C )-----------------( D ) 1
5 \1' \9' 11' /24'
\ \ /
\2' 21' 22' \10' /
( E )------------( F )____________/
3 2 23'
Figure 2: Example BIER-TE Topology
The BitPositions for the forward connected adjacencies are
represented by i', where i is from 1 to 28. In one option, they are
encoded as (n+i), where n is a power of 2 such as 32768. For
simplicity, these BitPositions are represented by (SI:BitString),
where SI = (6 + (i-1)/8) and BitString is of 8 bits. BitPositions i'
(i from 1 to 28) are represented by 1'(6:00000001), 2'(6:00000010),
3'(6:00000100), 4'(6:00001000), 5'(6:00010000), 6'(6:00100000),
7'(6:01000000), 8'(6:10000000), 9'(7:00000001), 10'(7:00000010), . .
. , 24'(8:10000000) 25'(9:00000001), 26'(9:00000010), ...,
28'(9:00001000).
For a link between two nodes X and Y, there are two BitPositions for
two forward connected adjacencies. These two forward connected
adjacency BitPositions are assigned on nodes X and Y respectively.
The BitPosition assigned on X is the forward connected adjacency of
Y. The BitPosition assigned on Y is the forward connected adjacency
of X.
For example, for the link between nodes B and C in the figure, two
forward connected adjacency BitPositions 3' and 4' are assigned to
two ends of the link. BitPosition 3' is assigned on node B to B's
end of the link. It is the forward connected adjacency of node C.
BitPosition 4' is assigned on node C to C's end of the link. It is
the forward connected adjacency of node B.
4.2. BIER-TE BIFT on a BFR
Every BFR in a BIER-TE domain/topology has a BIER-TE BIFT. For the
BIER-TE topology in Figure 2, each of 9 nodes/BFRs A, B, C, D, E, F,
G, H and I has its BIER-TE BIFT for the topology.
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The BIER-TE BIFT on BFR B (i.e. node B) is shown in Figure 3.
The 1st forwarding entry in the BIFT is for BitPosition 2', which is
the forward connected adjacency from B to E. For a multicast packet
with BitPosition 2', which indicates that the P2MP path in the packet
traverses the adjacency from B to E, the forwarding entry forwards
the packet to E along the link from B to E.
The 2nd forwarding entry in the BIFT is for BitPosition 4', which is
the forward connected adjacency from B to C. For a multicast packet
with BitPosition 4', which indicates that the P2MP path in the packet
traverses the adjacency from B to C, the forwarding entry forwards
the packet to C along the link from B to C.
The 3rd forwarding entry in the BIFT is for BitPosition 6', which is
the forward connected adjacency from B to G. For a multicast packet
with BitPosition 6', which indicates that the P2MP path in the packet
traverses the adjacency from B to G, the forwarding entry forwards
the packet to G along the link from B to G.
The 4-th forwarding entry in the BIFT is for BitPosition 8', which is
the forward connected adjacency from B to A. For a multicast packet
with BitPosition 8', which indicates that the P2MP path in the packet
traverses the adjacency from B to A, the forwarding entry forwards
the packet to A along the link from B to A.
+----------------+--------------+------------+
| Adjacency BP | Action | BFR-NBR |
| (SI:BitString) | | (Next Hop) |
+================+==============+============+
| 2'(6:00000010) | fw-connected | E |
+----------------+--------------+------------+
| 4'(6:00001000) | fw-connected | C |
+----------------+--------------+------------+
| 6'(6:00100000) | fw-connected | G |
+----------------+--------------+------------+
| 8'(6:10000000) | fw-connected | A |
+----------------+--------------+------------+
Figure 3: BIER-TE BIFT on BFR B
The BIER-TE BIFT on BFR E (i.e. node E) is shown in Figure 4.
The 1st forwarding entry in the BIFT forwards a multicast packet with
BitPosition 1' to B. It is for BitPosition 1', which is the forward
connected adjacency from E to B. For a multicast packet with
BitPosition 1', which indicates that the P2MP path in the packet
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traverses the adjacency from E to B, the forwarding entry forwards
the packet to B along the link from E to B.
The 2nd forwarding entry in the BIFT forwards a multicast packet with
BitPosition 22' to F. It is for BitPosition 22', which is the
forward connected adjacency from E to F. For a multicast packet with
BitPosition 22', which indicates that the P2MP path in the packet
traverses the adjacency from E to F, the forwarding entry forwards
the packet to F along the link from E to F.
The 3rd forwarding entry in the BIFT locally decapsulates a multicast
packet with BitPosition 3 and passes a copy of the payload of the
packet to the packet's NextProto. It is for BitPosition 3, which is
the local decap adjacency for BFER (i.e., egress) E. For a multicast
packet with BitPosition 3, which indicates that the P2MP path in the
packet has node E as one of its destinations (i.e., egress nodes),
the forwarding entry decapsulates the packet and passes a copy of the
payload of the packet to the packet's NextProto within node E.
+----------------+--------------+------------+
| Adjacency BP | Action | BFR-NBR |
| (SI:BitString) | | (Next Hop) |
+================+==============+============+
| 1'(6:00000001)| fw-connected | B |
+----------------+--------------+------------+
| 22'(8:00001000)| fw-connected | F |
+----------------+--------------+------------+
| 3 (0:00000100)| local-decap | |
+----------------+--------------+------------+
Figure 4: BIER-TE BIFT on BFR D
4.3. Extended BIER-TE BIFT on a BFR
Every BFR has an extended BIER-TE BIFT to support BIER-TE FRR
protection against the failure of its neighbor transit node.
For example, the extended BIER-TE BIFT on BFR B is illustrated in
Figure 5. Each forwarding entry with transit node (such as E, C and
G) as its BFR-NBR in the BIFT comprises a FRR entry. Each of these
FRR entries contains a flag FPA and a number of backup paths. For a
forwarding entry with transit node X, its FRR entry has a backup path
to each of node X's next hop nodes except for BFR B itself. FPA is
set to zero in normal operations. FPA in the FRR entry for neighbor
transit node X is set to one when node X fails.
On BFR B, the 1st forwarding entry in the BIFT has BFR-NBR E as
transit node. Nodes F and B are the next hop nodes of node E in
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Figure 2. The backup path from B to F without E or links attached to
E goes through the link from B to C and then the link from C to F.
This backup path from B to F is represented by B-->F: {4', 10'} in
the FRR entry of the forwarding entry.
FPA in the FRR entry is set to 0 (zero) in normal operations. When
transit node E fails, the FPA is set to 1 (one) and the FRR entry is
used to forward a multicast packet with BitPosition 2' for adjacency
from B to E towards E's next hop node F along the backup path from B
to F if the P2MP path in the packet traverses node F.
+----------------+--------------+----------+-----------------+
| Adjacency BP | Action | BFR-NBR | FRR Entry |
| (SI:BitString) | |(Next Hop)|(FPA,BackupPaths)|
+================+==============+==========+=================+
| 2'(6:00000010) | fw-connected | E | FPA=0, |
+----------------+--------------+----------+ |
| B-->F: {4',10'} |
+----------------+--------------+----------+-----------------+
| 4'(6:00000010) | fw-connected | C | FPA=0, |
+----------------+--------------+----------+ |
| B-->F: {2',22'}, B-->D: {6',20',27'}, B-->I: {6',17'} |
+----------------+--------------+----------+-----------------+
| 6'(6:00100000) | fw-connected | G | FPA=0, |
+----------------+--------------+----------+ |
| B-->I: {4',14'}, B-->H: {4',14',16'}, B-->A: {8'} |
+----------------+--------------+----------+-----------------+
| 8'(6:10000000) | fw-connected | A | FPA=0, |
+----------------+--------------+----------+ |
| B-->G: {6'} |
+----------------+--------------+----------+-----------------+
Figure 5: Extended BIER-TE BIFT on BFR B
On BFR B, the 2nd forwarding entry in the BIFT has BFR-NBR C as
transit node. Nodes F, D, I and B are the next hop nodes of node C
in Figure 2. The backup path from B to F without C or links attached
to C goes through the link from B to E and then the link from E to F.
This backup path from B to F is represented by B-->F: {2', 22'} in
the FRR entry of the forwarding entry.
The backup path from B to D without C or links attached to C goes
through the link from B to G, the link from G to H and then the link
from H to D. This backup path from B to D is represented by B-->D:
{6', 20', 27'} in the FRR entry of the forwarding entry.
The backup path from B to I without C or links attached to C goes
through the link from B to G and then the link from G to I. This
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backup path from B to I is represented by B-->I: {6', 17'} in the FRR
entry of the forwarding entry.
FPA in the FRR entry is set to 0 (zero) in normal operations. When
transit node C fails, the FPA is set to 1 (one) and the FRR entry is
used to forward a multicast packet with BitPosition 4' for adjacency
from B to C towards C's next hop nodes F, D or I along the backup
paths from B to F, D or I respectively if the P2MP path in the packet
traverses nodes F, D or I.
On BFR B, the 3rd forwarding entry in the BIFT has BFR-NBR G as
transit node. Nodes I, H, A and B are the next hop nodes of node G
in Figure 2. The backup path from B to I without G or links attached
to G goes through the link from B to C and then the link from C to I.
This backup path from B to I is represented by B-->I: {4', 14'} in
the FRR entry of the forwarding entry.
The backup path from B to H without G or links attached to G goes
through the link from B to C, the link from C to I and then the link
from I to H. This backup path from B to H is represented by B-->H:
{4', 14', 16'} in the FRR entry of the forwarding entry.
The backup path from B to A without G or links attached to G goes
through the link from B to A. This backup path from B to A is
represented by B-->A: {8'} in the FRR entry of the forwarding entry.
FPA in the FRR entry is set to 0 (zero) in normal operations. When
transit node G fails, the FPA is set to 1 (one) and the FRR entry is
used to forward a multicast packet with BitPosition 6' for adjacency
from B to G towards G's next hop nodes I, H or A along the backup
paths from B to I, H or A respectively if the P2MP path in the packet
traverses nodes I, H or A.
On BFR B, the 4-th forwarding entry in the BIFT has BFR-NBR A as
transit node. Nodes G and B are the next hop nodes of node A. The
backup path from B to G without A or links attached to A goes through
the link from B to G. This backup path from B to G is represented by
B-->G: {6'} in the FRR entry of the forwarding entry.
FPA in the FRR entry is set to 0 (zero) in normal operations. When
node A fails, the FPA is set to 1 (one) and the FRR entry is used to
forward a multicast packet with BitPosition 8' for adjacency from B
to A towards A's next hop node G along the backup path from B to G if
the P2MP path in the packet traverses node A as a transit node.
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4.4. Forwarding using Extended BIER-TE BIFT
Suppose that there is an explicit multicast P2MP path from ingress A
to egresses H and D, traversing from A to G to H and from A to B to C
to D. This path is represented by BPs as {26', 20', 7', 4', 12', 4,
1}. The forwarding behaviors in normal operations and in case of BFR
C failure are described below.
4.4.1. Forwarding in Normal Operations
For a multicast packet with the path on BFR A, A sends the packet to
G and B according to the forwarding entries for 26' and 7' in A's
extended BIER-TE BIFT respectively. The packet received by G and B
contains path {20', 4', 12', 4, 1}.
After receving the packet from A, G forwards the packet to H
according to forwarding entry for 20' in its extended BIER-TE BIFT.
The packet received by H contains path {4', 12', 4, 1}. After
receving the packet from A, B forwards the packet to C according to
forwarding entry for 4' in its extended BIER-TE BIFT. The packet
received by C contains path {20', 12', 4, 1}.
After receving the packet from G, H decapsulates the packet and
passes a copy of the payload of the packet to the packet's NextProto
according to forwarding entry for 4 in its extended BIER-TE BIFT.
After receving the packet from B, C forwards the packet to D
according to forwarding entry for 12' in its extended BIER-TE BIFT.
The packet received by D contains path {20', 4, 1}.
After receving the packet from C, D decapsulates the packet and
passes a copy of the payload of the packet to the packet's NextProto
according to forwarding entry for 1 in its extended BIER-TE BIFT.
4.4.2. Forwarding in Failure
Once BFR B detects the failure of node C, it sets FPA of the FRR
entry in the 2nd forwarding entry with BFR-NBR C to one. After
receiving the packet from BFR A, which contains path {20', 4', 12',
4, 1}, BFR B clears BP 4'; BFR B clears the BP 4 for BFER H since H
is on the backup path from B to G to H to D, but not on any branch of
the path from B.
For C's next hop node D on the P2MP path, BFR B clears adjacency BP
12' from C to D and adds the BPs for backup path {6', 20', 27'} from
B to G to H to D. The packet has path {6', 20', 27', 1}. BFR B
sends the packet to G according to forwarding entry for 6' in its
extended BIER-TE BIFT. The packet received by G contains path {20',
27', 1}.
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After receving the packet from B, G forwards the packet to H
according to forwarding entry for 20' in its extended BIER-TE BIFT.
The packet received by H contains path {27', 1}.
After receving the packet from G, H forwards the packet to D
according to forwarding entry for 27' in its extended BIER-TE BIFT.
The packet received by D contains path {1}.
After receving the packet from H, D decapsulates the packet and
passes a copy of the payload of the packet to the packet's NextProto
according to forwarding entry for 1 in its extended BIER-TE BIFT.
5. Security Considerations
TBD.
6. IANA Considerations
No requirements for IANA.
7. Acknowledgements
The authors would like to thank Daniel Merling for his comments to
this work.
8. References
8.1. Normative References
[I-D.ietf-bier-te-arch]
Eckert, T., Cauchie, G., and M. Menth, "Tree Engineering
for Bit Index Explicit Replication (BIER-TE)", draft-ietf-
bier-te-arch-09 (work in progress), October 2020.
[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>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<https://www.rfc-editor.org/info/rfc5226>.
[RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250,
July 2008, <https://www.rfc-editor.org/info/rfc5250>.
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[RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for
IP Fast Reroute: Loop-Free Alternates", RFC 5286,
DOI 10.17487/RFC5286, September 2008,
<https://www.rfc-editor.org/info/rfc5286>.
[RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework",
RFC 5714, DOI 10.17487/RFC5714, January 2010,
<https://www.rfc-editor.org/info/rfc5714>.
[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>.
[RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding
Scope Link State PDUs (LSPs)", RFC 7356,
DOI 10.17487/RFC7356, September 2014,
<https://www.rfc-editor.org/info/rfc7356>.
[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>.
[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <https://www.rfc-editor.org/info/rfc7684>.
[RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <https://www.rfc-editor.org/info/rfc7770>.
[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>.
[RFC8556] Rosen, E., Ed., Sivakumar, M., Przygienda, T., Aldrin, S.,
and A. Dolganow, "Multicast VPN Using Bit Index Explicit
Replication (BIER)", RFC 8556, DOI 10.17487/RFC8556, April
2019, <https://www.rfc-editor.org/info/rfc8556>.
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8.2. Informative 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.
[I-D.ietf-rtgwg-segment-routing-ti-lfa]
Litkowski, S., Bashandy, A., Filsfils, C., Decraene, B.,
and D. Voyer, "Topology Independent Fast Reroute using
Segment Routing", draft-ietf-rtgwg-segment-routing-ti-
lfa-05 (work in progress), November 2020.
[I-D.ietf-spring-segment-protection-sr-te-paths]
Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu,
"Segment Protection for SR-TE Paths", draft-ietf-spring-
segment-protection-sr-te-paths-00 (work in progress),
September 2020.
[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
for Bit Index Explicit Replication (BIER) in MPLS and Non-
MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
2018, <https://www.rfc-editor.org/info/rfc8296>.
[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>.
Authors' Addresses
Huaimo Chen
Futurewei
Boston, MA
USA
Email: Huaimo.chen@futurewei.com
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Mike McBride
Futurewei
Email: michael.mcbride@futurewei.com
Yisong Liu
China Mobile
Email: liuyisong@chinamobile.com
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing, 102209
China
Email: wangaj3@chinatelecom.cn
Gyan S. Mishra
Verizon Inc.
13101 Columbia Pike
Silver Spring MD 20904
USA
Phone: 301 502-1347
Email: gyan.s.mishra@verizon.com
Yanhe Fan
Casa Systems
USA
Email: yfan@casa-systems.com
Lei Liu
Fujitsu
USA
Email: liulei.kddi@gmail.com
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Xufeng Liu
Volta Networks
McLean, VA
USA
Email: xufeng.liu.ietf@gmail.com
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