draft-ietf-bier-mvpn-06.txt   draft-ietf-bier-mvpn-07.txt 
Internet Engineering Task Force E. Rosen, Ed. Internet Engineering Task Force E. Rosen, Ed.
Internet-Draft Juniper Networks, Inc. Internet-Draft Juniper Networks, Inc.
Intended status: Experimental M. Sivakumar Intended status: Experimental M. Sivakumar
Expires: December 29, 2017 Cisco Systems, Inc. Expires: January 27, 2018 Cisco Systems, Inc.
S. Aldrin S. Aldrin
Google, Inc. Google, Inc.
A. Dolganow A. Dolganow
Nokia Nokia
T. Przygienda T. Przygienda
Juniper Networks, Inc. Juniper Networks, Inc.
June 27, 2017 July 26, 2017
Multicast VPN Using BIER Multicast VPN Using BIER
draft-ietf-bier-mvpn-06 draft-ietf-bier-mvpn-07
Abstract Abstract
The Multicast Virtual Private Network (MVPN) specifications require The Multicast Virtual Private Network (MVPN) specifications require
the use of multicast tunnels ("P-tunnels") that traverse a Service the use of multicast tunnels ("P-tunnels") that traverse a Service
Provider's backbone network. The P-tunnels are used for carrying Provider's backbone network. The P-tunnels are used for carrying
multicast traffic across the backbone. A variety of P-tunnel types multicast traffic across the backbone. A variety of P-tunnel types
are supported. Bit Index Explicit Replication (BIER) is a new are supported. Bit Index Explicit Replication (BIER) is a new
architecture that provides optimal multicast forwarding through a architecture that provides optimal multicast forwarding through a
"multicast domain", without requiring intermediate routers to "multicast domain", without requiring intermediate routers to
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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-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
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 December 29, 2017. This Internet-Draft will expire on January 27, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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
(http://trustee.ietf.org/license-info) in effect on the date of (http://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 . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Use of the PMSI Tunnel Attribute in x-PMSI A-D Routes . . . . 5 2. Use of the PMSI Tunnel Attribute in x-PMSI A-D Routes . . . . 5
2.1. MPLS Label . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. MPLS Label . . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Explicit Tracking . . . . . . . . . . . . . . . . . . . . 7 2.2. Explicit Tracking . . . . . . . . . . . . . . . . . . . . 8
2.2.1. Using the LIR Flag . . . . . . . . . . . . . . . . . 8 2.2.1. Using the LIR Flag . . . . . . . . . . . . . . . . . 9
2.2.2. Using the LIR-pF Flag . . . . . . . . . . . . . . . . 8 2.2.2. Using the LIR-pF Flag . . . . . . . . . . . . . . . . 9
3. Use of the PMSI Tunnel Attribute in Leaf A-D routes . . . . . 9 3. Use of the PMSI Tunnel Attribute in Leaf A-D routes . . . . . 10
4. Data Plane . . . . . . . . . . . . . . . . . . . . . . . . . 10 4. Data Plane . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Encapsulation and Transmission . . . . . . . . . . . . . 10 4.1. Encapsulation and Transmission . . . . . . . . . . . . . 11
4.2. Disposition . . . . . . . . . . . . . . . . . . . . . . . 11 4.2. Disposition . . . . . . . . . . . . . . . . . . . . . . . 12
4.2.1. At a BFER that is an Egress PE . . . . . . . . . . . 12 4.2.1. At a BFER that is an Egress PE . . . . . . . . . . . 13
4.2.2. At a BFER that is a P-tunnel Segmentation Boundary . 12 4.2.2. At a BFER that is a P-tunnel Segmentation Boundary . 13
5. Contributor Addresses . . . . . . . . . . . . . . . . . . . . 12 5. Contributor Addresses . . . . . . . . . . . . . . . . . . . . 13
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . 13 9.1. Normative References . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . 14 9.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Introduction
[RFC6513] and [RFC6514] specify the protocols and procedures that a [RFC6513] and [RFC6514] specify the protocols and procedures that a
Service Provider (SP) can use to provide Multicast Virtual Private Service Provider (SP) can use to provide Multicast Virtual Private
Network (MVPN) service to its customers. Multicast tunnels are Network (MVPN) service to its customers. Multicast tunnels are
created through an SP's backbone network; these are known as created through an SP's backbone network; these are known as
"P-tunnels". The P-tunnels are used for carrying multicast traffic "P-tunnels". The P-tunnels are used for carrying multicast traffic
across the backbone. The MVPN specifications allow the use of across the backbone. The MVPN specifications allow the use of
several different kinds of P-tunnel technology. several different kinds of P-tunnel technology.
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root. In this case, it contains information that is needed in root. In this case, it contains information that is needed in
order for the originator of the route to join the specified order for the originator of the route to join the specified
P-tunnel. P-tunnel.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. Use of the PMSI Tunnel Attribute in x-PMSI A-D Routes 2. Use of the PMSI Tunnel Attribute in x-PMSI A-D Routes
As defined in [RFC6514], the PMSI Tunnel attribute (PTA) is used to As defined in [RFC6514], the PMSI Tunnel attribute (PTA) carried by
identify the P-tunnel that is used to instantiate a particular PMSI. an x-PMSI A-D route identifies the P-tunnel that is used to
If a PMSI is to be instantiated by BIER, the PTA is constructed as instantiate a particular PMSI. If a PMSI is to be instantiated by
follows. BIER, the PTA is constructed by a BFIR.
If segmented P-tunnels are not being used, the PTA attached to a
given x-PMSI A-D route is constructed by the router that originated
the route (typically by the ingress PE), and the PTA is not changed
as the route is propagated.
If segmented P-tunnels are being used, the PTA attached to a given
x-PMSI A-D route by the route's originator may replaced, at a
segmentation point (a BFER), by a PTA identifying the next segment of
the P-tunnel. If the next segment of the P-tunnel is instantiated by
BIER, the segmentation point serves as the BFIR for that next
segment.
In either case, a PTA is constructed by a BFIR as follows:
The PTA contains the following fields: The PTA contains the following fields:
o "Tunnel Type". IANA is requested to assign a new tunnel type o "Tunnel Type". IANA is requested to assign a new tunnel type
codepoint for "BIER" from the "P-Multicast Service Interface codepoint for "BIER" from the "P-Multicast Service Interface
Tunnel (PMSI Tunnel) Tunnel Types" registry. This codepoint will Tunnel (PMSI Tunnel) Tunnel Types" registry. This codepoint will
be used to indicate that the PMSI is instantiated by BIER. be used to indicate that the PMSI is instantiated by BIER.
(Although BIER does not actually create tunnels, the MVPN
procedures treat BIER as if it were a type of tunnel.) Although BIER does not actually create tunnels, the MVPN
procedures treat BIER as if it were a type of tunnel.
o "Tunnel Identifier". When the "tunnel type" is "BIER", this field o "Tunnel Identifier". When the "tunnel type" is "BIER", this field
contains two subfields: contains two subfields:
1. The first subfield is a single octet, containing a BIER sub- 1. The first subfield is a single octet, containing a BIER
domain-id. (See [BIER_ARCH].) This indicates that packets sub-domain-id. (See [BIER_ARCH].) This indicates that
sent on the PMSI will be sent on the specified BIER sub- packets sent on the PMSI will be sent on the specified BIER
domain. How that sub-domain is chosen is outside the scope of sub-domain. How that sub-domain is chosen is outside the
this document. scope of this document.
2. The second subfield is the BFR-Prefix (see [BIER_ARCH]) of the 2. The second subfield is the BFR-Prefix (see [BIER_ARCH]) of the
originator of the route that is carrying this PTA. This must router (a BFIR) that is constructing the PTA. This must be
be the originator's BFR-prefix in the specified sub-domain. the BFIR's BFR-prefix in the specified sub-domain. The
The BFR-Prefix will either be a /32 IPv4 address or a /128 BFR-Prefix will either be a /32 IPv4 address or a /128 IPv6
IPv6 address. Whether the address is IPv4 or IPv6 can be address. Whether the address is IPv4 or IPv6 can be inferred
inferred from the total length of the PMSI Tunnel attribute. from the total length of the PTA.
The BFR-Prefix need not be the same IP address that is carried The BFR-Prefix need not be the same IP address that is carried
in any other field of the x-PMSI A-D route. in any other field of the x-PMSI A-D route, even if the BFIR
is the originating router of the x-PMSI A-D route.
Failure to properly set the Tunnel Identifier field cannot be Failure to properly set the Tunnel Identifier field cannot be
detected by the protocol, and will result in improper delivery of detected by the protocol, and will result in improper delivery of
the data packets sent on the PMSI. the data packets sent on the PMSI.
o "MPLS label". This field MUST contain an upstream-assigned MPLS o "MPLS label". This field MUST contain an upstream-assigned non-
label. It is assigned by the router that originates the BGP route zero MPLS label. It is assigned by the router (a BFIR) that
to which the PTA is attached. Constraints on the way in which the constructs the PTA. Constraints on the way in which a BFIR
originating router selects this label are discussed in selects this label are discussed in Section 2.1.
Section 2.1.
Failure to follow the constraints on label assignment cannot be Failure to follow the constraints on label assignment cannot be
detected by the protocol, and may result in improper handling of detected by the protocol, and may result in improper handling of
data packets by the egress PE routers. data packets by the egress PE routers.
o "Flags". When the tunnel type is BIER, two of the flags in the o "Flags". When the tunnel type is BIER, two of the flags in the
PTA Flags field are meaningful. Details about the use of these PTA Flags field are meaningful. Details about the use of these
flags can be found in Section 2.2. flags can be found in Section 2.2.
* "Leaf Info Required per Flow (LIR-pF)". This flag is * "Leaf Info Required per Flow (LIR-pF)". This flag is
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the same BIER domain as the originator of the route. If the the same BIER domain as the originator of the route. If the
originator is in more than one BIER domain, the route must be originator is in more than one BIER domain, the route must be
distributed only within the BIER domain in which the BFR-Prefix in distributed only within the BIER domain in which the BFR-Prefix in
the PTA uniquely identifies the originator. As with all MVPN routes, the PTA uniquely identifies the originator. As with all MVPN routes,
distribution of these routes is controlled by the provisioning of distribution of these routes is controlled by the provisioning of
Route Targets. Thus the requirement expressed in this paragraph is Route Targets. Thus the requirement expressed in this paragraph is
really a requirement on the way the Route Targets are provisioned. really a requirement on the way the Route Targets are provisioned.
2.1. MPLS Label 2.1. MPLS Label
Suppose an ingress PE originates two x-PMSI A-D routes. Suppose each Suppose a BFIR attaches a PTA to each of two x-PMSI A-D routes, and
route carries a PTA, and the PTA of each route specifies a tunnel both PTAs specify a tunnel type of "BIER".
type of "BIER".
o If the two routes do not carry the same set of Route Targets o If the two routes do not carry the same set of Route Targets
(RTs), then their respective PTAs MUST contain different MPLS (RTs), then their respective PTAs MUST contain different MPLS
label values. label values.
o If the two routes do not have the same Address Family Identifier o If the two routes do not have the same Address Family Identifier
(AFI) value, then their respective PTAs MUST contain different (AFI) value, then their respective PTAs MUST contain different
MPLS label values. This ensures that when an egress PE receives a MPLS label values. This ensures that when an egress PE receives a
data packet with the given label, the egress PE can infer from the data packet with the given label, the egress PE can infer from the
label whether the payload is an IPv4 packet or an IPv6 packet. label whether the payload is an IPv4 packet or an IPv6 packet.
o If the ingress PE is supporting MVPN extranet ([RFC7900]) o If the BFIR is an ingress PE supporting MVPN extranet ([RFC7900])
functionality, and if the two routes originate from different functionality, and if the two routes originate from different VRFs
VRFs, then the respective PTAs of the two routes MUST contain on this ingress PE, then the respective PTAs of the two routes
different MPLS label values. MUST contain different MPLS label values.
o If the ingress PE is supporting the "Extranet Separation" feature o If the BFIR is an ingress PE supporting the "Extranet Separation"
of MVPN extranet (see Section 7.3 of [RFC7900], section ), and if feature of MVPN extranet (see Section 7.3 of [RFC7900]), and if
one of the routes carries the "Extranet Separation" extended one of the routes carries the "Extranet Separation" extended
community and the other does not, then the respective PTAs of the community but the other does not, then the respective PTAs of the
two routes MUST contain different MPLS label values. two routes MUST contain different MPLS label values.
o If segmented P-tunnels are being used, then the respective PTAs of o If segmented P-tunnels are being used, then the respective PTAs of
the two routes MUST contain different MPLS label values, as long the two routes MUST contain different MPLS label values whenever
as the NLRIs are not identical. In this case, the MPLS label can the respective NLRIs of the two routes are not identical. The
be used by the BFER to identify the particular C-flow to which a MPLS label can then be used at the next segmentation point to
data packet belongs, and this greatly simplifies the process of switch packets from one P-tunnel segment directly to the next,
forwarding a received packet to its next P-tunnel segment. This without requiring the segmentation points to contain any other
is explained further below. See also Section 4. multicast forwarding state. This is explained further below. See
also Section 4.
When segmented P-tunnels are being used, an ABR or ASBR may receive, When segmented P-tunnels are being used, a segmentation point, call
from a BIER domain, an x-PMSI A-D route whose PTA specifies "BIER". it "B1", may receive, from within a given BIER domain, an x-PMSI A-D
This means that BIER is being used for one segment of a segmented route whose PTA specifies "BIER". This means that BIER is being used
P-tunnel. The ABR/ASBR may in turn need to originate an x-PMSI A-D for the previous segment of a segmented P-tunnel. If the next
route whose PTA identifies the next segment of the P-tunnel. The segment is also of type "BIER", B1 will be the BFIR for the next
next segment may also be "BIER". Suppose an ASBR receives x-PMSI A-D segment. That is, B1 is a BFER of one BIER domain (corresponding to
routes R1 and R2, and as a result originates x-PMSI A-D routes R3 and the previous segment), and a BFIR of another BIER domain
R4 respectively, where the PTAs of each of the four routes specify (corresponding to the next segment). B1 needs to replace the PTA of
BIER. Then the PTAs of R3 and R4 MUST NOT specify the same MPLS the x-PMSI A-D route with a new PTA, specifying its own BFR-Prefix,
label, UNLESS both of the following conditions hold: and specifying an upstream-assigned label assigned by B1 itself.
o R1 and R2 have the same "originating router" in their respective Suppose B1 has received two x-PMSI A-D routes, R1 and R2, where:
NLRIs.
o R1 and R2 specify the same MPLS label in their respective PTAs. o R1 and R2 each have a PTA specifying BIER,
The ABR/ASBR MUST then program its dataplane such that a packet o R1's PTA specifies BFR-Prefix B2 and Label L2.
arriving with the upstream-assigned label specified in route R1 is
transmitted with the upstream-assigned label specified in route R3, o R2's PTA specifies BFR-Prefix B3 and Label L3.
and a packet arriving with the upstream-assigned label specified in
route R2 is transmitted with the label specified in route R4. Of Suppose B1 decides to propagate both R1 and R2, replacing each PTA
course, the data plane must also be programmed to encapsulate the with a new PTA specifying BIER. Suppose these new PTAs specify
transmitted packets with an appropriate BIER header, whose BitString labels L4 and L5 respectively. Then L4 and L5 MUST be different
is determined by the multicast flow overlay. (upstream-assigned) label values, UNLESS both of the following
conditions hold:
o R1 and R2 have the same value in the "originating router" field of
their respective NLRIs, and
o B2 is equal to B3, and
o L2 is equal to L3.
The segmentation point (B1 in this example) MUST also program its
dataplane appropriately. For example, when:
o B1 receives a BIER packet for which it is a BFER, and
o the BIER header specifies the BFIR-id that corresponds to B2,and
o the BIER payload is an MPLS packet with upstream-assigned label,
and
o the top label value is L2,
then the dataplane must be programmed to replace L2 with L4, and to
reencapsulate the packet in a BIER header, with B1's BFIR-id in the
BFIR-id field. The BitString of the new BIER header is determined by
the MVPN explicit tracking procedures (see Section 2.2 in the BIER
domain of the next segment.
2.2. Explicit Tracking 2.2. Explicit Tracking
When using BIER to transport an MVPN data packet through a BIER When using BIER to transport an MVPN data packet through a BIER
domain, an ingress PE functions as a BFIR (see [BIER_ARCH]). The domain, an ingress PE functions as a BFIR (see [BIER_ARCH]). The
BFIR must determine the set of BFERs to which the packet needs to be BFIR must determine the set of BFERs to which the packet needs to be
delivered. This can be done in either of two ways: delivered. This can be done in either of two ways:
1. Using the explicit tracking mechanism based on the "Leaf Info 1. Using the explicit tracking mechanism based on the "Leaf Info
Required" flag specified in [RFC6513] and [RFC6514]. This method Required" flag specified in [RFC6513] and [RFC6514]. This method
is further described in Section 2.2.1. is further described in Section 2.2.1.
2. Using the OPTIONAL explicit tracking mechanism based on the LIR- 2. Using the OPTIONAL explicit tracking mechanism based on the
pF flag specified in [EXPLICIT_TRACKING]. This method, further LIR-pF flag specified in [EXPLICIT_TRACKING]. This method,
described in Section 2.2.2, may be used if (and only if) further described in Section 2.2.2, may be used if (and only if)
segmented P-tunnels are not being used. segmented P-tunnels are not being used.
2.2.1. Using the LIR Flag 2.2.1. Using the LIR Flag
To determine the set of BFERs to which the packets of a given C-flow To determine the set of BFERs to which the packets of a given C-flow
must be sent, a BFIR MUST originate a (C-S,C-G) S-PMSI A-D route for must be sent, a BFIR MUST originate a (C-S,C-G) S-PMSI A-D route for
the given C-flow. It MUST attach a PTA to that route, and MUST set the given C-flow. It MUST attach a PTA to that route, and MUST set
the LIR flag in the PTA. Per [RFC6514], the BFERs that need to the LIR flag in the PTA. Per [RFC6514], the BFERs that need to
receive that C-flow will respond with (C-S,C-G) Leaf A-D routes. By receive that C-flow will respond with (C-S,C-G) Leaf A-D routes. By
matching the received Leaf A-D routes to the originated S-PMSI A-D matching the received Leaf A-D routes to the originated S-PMSI A-D
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this document. this document.
This method greatly reduces the number of S-PMSI A-D routes that a This method greatly reduces the number of S-PMSI A-D routes that a
BFIR needs to originate; it can now originate as few as one such BFIR needs to originate; it can now originate as few as one such
route (a (C-*,C-*) S-PMSI A-D route), rather than one for each route (a (C-*,C-*) S-PMSI A-D route), rather than one for each
C-flow. However, the method does not provide a way for the BFIR to C-flow. However, the method does not provide a way for the BFIR to
assign a distinct label to each C-flow. Therefore it cannot be used assign a distinct label to each C-flow. Therefore it cannot be used
when segmented P-tunnels are in use (see Section 4 for an when segmented P-tunnels are in use (see Section 4 for an
explanation). explanation).
Note: if a BFIR originates a (C-*,C-*) S-PMSI A-D route with the LIR- Note: if a BFIR originates a (C-*,C-*) S-PMSI A-D route with the
pF flag set, but also originates a more specific wildcard route that LIR-pF flag set, but also originates a more specific wildcard route
matches a particular (C-S,C-G), the BFERs will not originate Leaf A-D that matches a particular (C-S,C-G), the BFERs will not originate
routes for that (C-S,C-G) unless the LIR-pF flag is also set in the Leaf A-D routes for that (C-S,C-G) unless the LIR-pF flag is also set
more specific wildcard route. If the BFIR also originates a in the more specific wildcard route. If the BFIR also originates a
(C-S,C-G) S-PMSI A-D route without the LIR flag set, the BFERs will (C-S,C-G) S-PMSI A-D route without the LIR flag set, the BFERs will
not originate Leaf A-D routes for that (C-S,C-G) unless the LIR flag not originate Leaf A-D routes for that (C-S,C-G) unless the LIR flag
is also set in that route. is also set in that route.
3. Use of the PMSI Tunnel Attribute in Leaf A-D routes 3. Use of the PMSI Tunnel Attribute in Leaf A-D routes
Before an egress PE can receive a (C-S,C-G) flow from a given ingress Before an egress PE can receive a (C-S,C-G) flow from a given ingress
PE via BIER, the egress PE must have received one of the following PE via BIER, the egress PE must have received one of the following
x-PMSI A-D routes from the ingress PE: x-PMSI A-D routes from the ingress PE:
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The rules for determining which x-PMSI A-D route is the match for The rules for determining which x-PMSI A-D route is the match for
reception are given in [RFC6625]. However, these rules are reception are given in [RFC6625]. However, these rules are
modified here to exclude any x-PMSI A-D route that does not have a modified here to exclude any x-PMSI A-D route that does not have a
PTA, or whose PTA specifies "no tunnel type". PTA, or whose PTA specifies "no tunnel type".
If such a route is found, we refer to it as the "matching x-PMSI If such a route is found, we refer to it as the "matching x-PMSI
A-D route." A-D route."
If no matching x-PMSI A-D route for (C-S,C-G) is found, the egress PE If no matching x-PMSI A-D route for (C-S,C-G) is found, the egress PE
cannot receive the (C-S,C-G) flow from the ingress PE via BIER. cannot receive the (C-S,C-G) flow from the ingress PE via BIER until
such time as a matching route is received.
When an egress PE determines that it needs to receive a (C-S,C-G) When an egress PE determines that it needs to receive a (C-S,C-) flow
flow from a particular ingress PE via BIER, it originates a Leaf A-D from a particular ingress PE via BIER, it originates a Leaf A-D
route. Construction of the Leaf A-D route generally follows the route. Construction of the Leaf A-D route generally follows the
procedures specified in [RFC6514], or optionally, the procedures procedures specified in [RFC6514], or optionally, the procedures
specified in [EXPLICIT_TRACKING]. However, when BIER is being used, specified in [EXPLICIT_TRACKING]. However, when BIER is being used,
the Leaf A-D route MUST carry a PTA that is constructed as follows: the Leaf A-D route MUST carry a PTA that is constructed as follows:
1. The tunnel type MUST be set to "BIER". 1. The tunnel type MUST be set to "BIER".
2. The MPLS label field SHOULD be set to zero. 2. The MPLS label field SHOULD be set to zero.
3. The sub-domain-id field of the Tunnel Identifier field (as 3. The sub-domain-id field of the Tunnel Identifier field (as
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the PTA of the matching x-PMSI A-D route. the PTA of the matching x-PMSI A-D route.
4. The BFR-Prefix field of the Tunnel Identifier field (as defined 4. The BFR-Prefix field of the Tunnel Identifier field (as defined
in Section 2) MUST be set to the egress PE's BFR-Prefix in the in Section 2) MUST be set to the egress PE's BFR-Prefix in the
sub-domain identifiers in the PTA of the matching x-PMSI A-D sub-domain identifiers in the PTA of the matching x-PMSI A-D
route. route.
The BFR-Prefix need not be the same IP address that is carried in The BFR-Prefix need not be the same IP address that is carried in
any other field of the Leaf A-D route. any other field of the Leaf A-D route.
When an ingress PE receives such a Leaf A-D route, it learns the BFR- When an ingress PE receives such a Leaf A-D route, it learns the
Prefix of the egress PE from the PTA. The ingress PE does not make BFR-Prefix of the egress PE from the PTA. The ingress PE does not
any use the value of the PTA's MPLS label field. make any use the value of the PTA's MPLS label field.
Failure to properly construct the PTA cannot always be detected by Failure to properly construct the PTA cannot always be detected by
the protocol, and will cause improper delivery of the data packets. the protocol, and will cause improper delivery of the data packets.
4. Data Plane 4. Data Plane
The MVPN application plays the role of the "multicast flow overlay" The MVPN application plays the role of the "multicast flow overlay"
as described in [BIER_ARCH]. as described in [BIER_ARCH].
4.1. Encapsulation and Transmission 4.1. Encapsulation and Transmission
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