Internet Engineering Task Force E. Rosen, Ed.
Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track M. Sivakumar
Expires: December 22, 2016 Cisco Systems, Inc.
S. Aldrin
Google, Inc.
A. Dolganow
Alcatel-Lucent
T. Przygienda
Ericsson
June 20, 2016
Multicast VPN Using BIER
draft-ietf-bier-mvpn-03
Abstract
The Multicast Virtual Private Network (MVPN) specifications require
the use of multicast tunnels ("P-tunnels") that traverse a Service
Provider's backbone network. The P-tunnels are used for carrying
multicast traffic across the backbone. A variety of P-tunnel types
are supported. Bit Index Explicit Replication (BIER) is a new
architecture that provides optimal multicast forwarding through a
"multicast domain", without requiring intermediate routers to
maintain any per-flow state or to engage in an explicit tree-building
protocol. This document specifies the protocol and procedures that
allow MVPN to use BIER as the method of carrying multicast traffic
over an SP backbone network.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://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 December 22, 2016.
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Copyright Notice
Copyright (c) 2016 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
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Use of the PMSI Tunnel Attribute . . . . . . . . . . . . . . 4
3. Explicit Tracking . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Using the LIR Flag . . . . . . . . . . . . . . . . . . . 7
3.2. Using the LIR-pF Flag . . . . . . . . . . . . . . . . . . 7
4. Data Plane . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Encapsulation and Transmission . . . . . . . . . . . . . 8
4.2. Disposition . . . . . . . . . . . . . . . . . . . . . . . 9
4.2.1. At a BFER that is an Egress PE . . . . . . . . . . . 9
4.2.2. At a BFER that is a P-tunnel Segmentation Boundary . 9
5. Contributor Addresses . . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
[RFC6513] and [RFC6514] specify the protocols and procedures that a
Service Provider (SP) can use to provide Multicast Virtual Private
Network (MVPN) service to its customers. Multicast tunnels are
created through an SP's backbone network; these are known as
"P-tunnels". The P-tunnels are used for carrying multicast traffic
across the backbone. The MVPN specifications allow the use of
several different kinds of P-tunnel technology.
Bit Index Explicit Replication (BIER) ([BIER_ARCH]) is an
architecture that provides optimal multicast forwarding through a
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"multicast domain", without requiring intermediate routers to
maintain any per-flow state or to engage in an explicit tree-building
protocol. The purpose of the current document is to specify the
protocols and procedures needed in order to provide MVPN service
using BIER to transport the multicast traffic over the backbone.
Although BIER does not explicitly build and maintain multicast
tunnels, one can think of BIER as using a number of implicitly
created tunnels through a "BIER domain". In particular, one can
think of there as being one Point-to-Multipoint (P2MP) tunnel from
each "Bit Forwarding Ingress Router" (BFIR) to all the "Bit
Forwarding Egress Routers" (BFERs) in the BIER domain, where a BIER
domain is generally co-extensive with an IGP network. These
"tunnels" are not specific to any particular VPN. However, the MVPN
architecture provides protocols and procedures that allow the traffic
of multiple MVPNs to be aggregated on a single P-tunnel. In this
document, we specify how to use these multi-VPN aggregation
procedures to enable BIER to transport traffic from multiple MVPNs.
MVPN traffic must sometimes traverse more than one IGP domain,
whereas BIER only carries multicast traffic within a single IGP
domain. However, the MVPN specifications allow P-tunnels to be
"segmented", where the segmentation points may either be Autonomous
System Border Routers (ASBRs), as described in [RFC6514], or Area
Border Routers (ABRs), as described in [RFC7524]. As long as the
segmentation points are capable of acting as BFIRs and BFERs, BIER
can be used to provide some or all of the segments of a P-tunnel.
This revision of the document does not specify the procedures
necessary to support MVPN customers that are using BIDIR-PIM. Those
procedures will be added in a future revision.
This document uses the following terminology from [BIER_ARCH]:
o BFR: Bit-Forwarding Router.
o BFIR: Bit-Forwarding Ingress Router.
o BFER: Bit-Forwarding Egress Router.
This document uses the following terminology from [RFC6513]:
o MVPN: Multicast Virtual Private Network -- a VPN [RFC4364] in
which multicast service is offered.
o P-tunnel. A multicast tunnel through the network of one or more
SPs. P-tunnels are used to transport MVPN multicast data
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o C-S: A multicast source address, identifying a multicast source
located at a VPN customer site.
o C-G: A multicast group address used by a VPN customer.
o C-flow: A customer multicast flow. Each C-flow is identified by
the ordered pair (source address, group address), where each
address is in the customer's address space. The identifier of a
particular C-flow is usually written as (C-S,C-G).
Sets of C-flows can be identified by the use of the "C-*" wildcard
(see [RFC6625]), e.g., (C-*,C-G).
o I-PMSI A-D Route: Inclusive Provider Multicast Service Interface
Auto-Discovery route. Carried in BGP Update messages, these
routes are used to advertise the "default" P-tunnel for a
particular MVPN.
o S-PMSI A-D route: Selective Provider Multicast Service Interface
Auto-Discovery route. Carried in BGP Update messages, these
routes are used to advertise the fact that particular C-flows are
bound to (i.e., are traveling through) particular P-tunnels.
o PMSI Tunnel attribute (PTA). This BGP attribute carried is used
to identify a particular P-tunnel. When C-flows of multiple VPNs
is carried in a single P-tunnel, this attribute also carries the
information needed to multiplex and demultiplex the C-flows.
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 RFC 2119 [RFC2119].
2. Use of the PMSI Tunnel Attribute
As defined in [RFC6514], the PMSI Tunnel attribute is used to
identify the particular P-tunnel to which one or more multicast flows
are being assigned.
The PMSI Tunnel attribute (PTA)contains the following fields:
o "Tunnel Type". IANA is requested to assign a new tunnel type
codepoint for "BIER". This codepoint will be used to indicate
that the PMSI is instantiated by BIER.
o "Tunnel Identifier". When the "tunnel type" field is "BIER", this
field contains two subfields:
1. The first subfield is a single octet, containing the sub-
domain-id of the sub-domain to which the BFIR will assign the
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packets that it transmits on the PMSI identified by the NLRI
of the BGP I-PMSI or S-PMSI A-D route that contains this PTA.
(How that sub-domain is chosen is outside the scope of this
document.)
2. The second subfield is the BFR-Prefix (see [BIER_ARCH]) of the
originator of the route that is carrying this PTA. This will
either be a /32 IPv4 address or a /128 IPv6 address. Whether
the address is IPv4 or IPv6 can be inferred from the total
length of the PMSI Tunnel attribute.
o "MPLS label". This field contains an upstream-assigned MPLS
label. It is assigned by the router that originates the BGP route
to which the PTA is attached. Constraints on the way in which the
originating router selects this label are discussed below.
o "Flags". When the tunnel type is BIER, two of the bits in the PTA
Flags field are meaningful. Details about the use of these bits
can be found in Section 3.
* "Leaf Info Required per Flow (LIR-pF)". This bit is introduced
in [EXPLICIT_TRACKING]. A BFIR SHOULD NOT set this bit UNLESS
it knows that all the BFERs in the BIER domain (or at least all
the BFERs to which it needs to transmit) support this bit.
(How this is known is outside the scope of this document.)
This bit MAY be set in a (C-*,C-*) S-PMSI A-D route, but MUST
NOT be set in I-PMSI A-D routes or in other S-PMSI A-D routes.
* "Leaf Info Required Bit". The setting of this bit depends upon
the type of route and the NLRI of the route that carries the
PTA.
+ In an I-PMSI A-D route or a (C-*,C-*) S-PMSI A-D route, the
bit SHOULD be clear, unless the LIR-pF bit has also been set
(see above). This bit SHOULD also be clear in a (C-S,C-*)
or (C-*,C-G) S-PMSI A-D route.
+ In other S-PMSI A-D routes, the bit SHOULD be set.
Note that if a PTA specifying "BIER" is attached to an I-PMSI or
S-PMSI A-D route, the route MUST NOT be distributed beyond the
boundaries of a BIER domain. That is, any routers that receive the
route must be in the same BIER domain as the originator of the route.
If the originator is in more than one BIER domain, the route must be
distributed only within the BIER domain in which the BFR-Prefix in
the PTA uniquely identifies the originator. As with all MVPN routes,
distribution of these routes is controlled by the provisioning of
Route Targets.
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Suppose an ingress PE originates two x-PMSI A-D routes, where we use
the term "x-PMSI" to mean "I-PMSI or S-PMSI". Suppose both routes
carry a PTA, and the PTA of each route specifies"BIER".
o If the two routes do not carry the same set of Route Targets
(RTs), then their respective PTAs MUST contain different MPLS
label values.
o If the ingress PE is supporting MVPN extranet ([EXTRANET])
functionality, and if the two routes originate from different
VRFs, then the respective PTAs of the two routes MUST contain
different MPLS label values.
o If the ingress PE is supporting the "Extranet Separation" feature
of MVPN extranet (see Section 7.3 of [EXTRANET], section ), and if
one of the routes carries the "Extranet Separation" extended
community and the other does not, then the respective PTAs of the
two routes MUST contain different MPLS label values.
o If segmented P-tunnels are being used, then the respective PTAs of
the two routes MUST contain different MPLS label values, as long
as the NLRIs are not identical. In this case, the MPLS label can
be used by the BFER to identify the particular C-flow to which a
data packet belongs, and this greatly simplifies the process of
forwarding a received packet to its next P-tunnel segment. This
is explained further in Section 4.
When segmented P-tunnels are being used, an ABR or ASBR may receive,
from a BIER domain, an x-PMSI A-D route whose PTA specifies "BIER".
This means that BIER is being used for one segment of a segmented
P-tunnel. The ABR/ASBR may in turn need to originate an x-PMSI A-D
route whose PTA identifies the next segment of the P-tunnel. The
next segment may also be "BIER". Suppose an ASBR receives x-PMSI A-D
routes R1 and R2, and as a result originates x-PMSI A-D routes R3 and
R4 respectively, where the PTAs of each of the four routes specify a
BIER. Then the PTAs of R3 and R4 MUST NOT specify the same MPLS
label, UNLESS both of the following conditions hold:
o R1 and R2 have the same "originating router" in their respective
NLRIs.
o R1 and R2 specify the same MPLS label in their respective PTAs.
3. Explicit Tracking
When using BIER to transport an MVPN data packet through a BIER
domain, an ingress PE functions as a BFIR (see [BIER_ARCH]). The
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BFIR must determine the set of BFERs to which the packet needs to be
delivered. This can be done in either of two ways:
1. By using the explicit tracking mechanism based on the "Leaf Info
Required" flag, as specified in [RFC6513] and [RFC6514], or
2. By using the explicit tracking mechanism based on the LIR-pF flag
as specified in [EXPLICIT_TRACKING]. This mechanism MAY be used
if (and only if) segmented P-tunnels are not being used.
3.1. Using the LIR Flag
To determine the set of BFERs to which a given MVPN data packet needs
to be delivered, the BFIR originating an S-PMSI A-D route sets the
LIR bit in the route's PTA. Per [RFC6514], the BFERs will respond
with Leaf A-D routes. By matching the received Leaf A-D routes to
the originated S-PMSI A-D routes, the originator of the S-PMSI A-D
route determines the set of BFERs that need to receive the multicast
data flow (or flows) that is (are) identified in the NLRI of the of
the S-PMSI A-D route.
This requires that each BFIR originate an S-PMSI A-D route for each
C-flow for which it serves as BFIR. The BFIR MAY include, in each
such route, a PTA as described in Section 2. However, if the BFIR
has originated an I-PMSI A-D route or a wildcard S-PMSI A-D route
that "matches" (according to the rules of [RFC6625]) a particular
C-flow, then it may do explicit tracking for that C-flow by
originating an S-PMSI A-D route for that C-flow, but including a PTA
that specifies "no tunnel type".
3.2. Using the LIR-pF Flag
If segmented P-tunnels are not being used, the BFIR can determine the
set of BFERs to which a given MVPN data packet needs to be delivered
by originating a (C-*,C-*) S-PMSI A-D route, and by setting the LIR-
pF flag in the PTA of that route. Per [EXPLICIT_TRACKING], each BFER
will respond with one or more Leaf A-D routes, identifying the flows
that it is expecting to receive from the BFIR that originated the
(C-*,C-*) S-PMSI A-D route.
A BFIR MUST NOT use this method of finding the set of BFERs needing
to receive a given C-flow unless it knows that all those BFERs
support the LIR-pF flag. How this is known is outside the scope of
this document.
This option greatly reduces the number of S-PMSI A-D routes that a
BFIR needs to originate; it now needs to originate only one such
route, rather than one for each C-flow. However, it does not provide
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a way for the BFIR to 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 explanation).
4. Data Plane
The MVPN application plays the role of the "multicast flow layer" as
described in [BIER_ARCH].
4.1. Encapsulation and Transmission
To transmit an MVPN data packet, an ingress PE follows the rules of
[RFC6625] to find the S-PMSI A-D route or I-PMSI A-D route that is a
"match for transmission" for that packet. (In applying the rules of
[RFC6625], any S-PMSI A-D route with a PTA specifying "no tunnel
information" is ignored.) If the matching route has a PTA specifying
a "BIER", the (upstream-assigned) MPLS label from that PTA is pushed
on the packet's label stack. Then the packet is encapsulated in a
BIER header and forwarded, according to the procedures of [BIER_ARCH]
and [BIER_ENCAPS]. (See especially Section 4, "Imposing and
Processing the BIER Encapsulation", of [BIER_ENCAPS].)
In order to create the proper BIER header for a given packet, the
BFIR must know all the BFERs that need to receive that packet. It
determines this by finding all the Leaf A-D routes that correspond to
the S-PMSI A-D route that is the packet's match for transmission.
There are two different cases to consider:
1. The S-PMSI A-D route that is the match for transmission carries a
PTA that has the LIR flag set but does not have the LIR-pF flag
set.
In this case, the corresponding Leaf A-D routes are those whose
"route key" field is identical to the NLRI of the S-PMSI A-D
route.
2. The S-PMSI A-D route that is the match for transmission carries a
PTA that has the LIR-pF flag.
In this case, the corresponding Leaf A-D routes are those whose
"route key" field is derived from the NLRI of the S-PMSI A-D
route according to the procedures described in Section 5.2 of
[EXPLICIT_TRACKING].
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4.2. Disposition
The procedures for handling a received BIER packet at BFER depend on
whether the BFER is an egress PE for the packet. A BFER can tell
whether it is an egress PE for a given BIER packet by examining the
MPLS label that the packet is carrying immediately after the BIER
header. This will be an upstream-assigned label (from the BFIR) that
has been advertised in the PTA of an S-PMSI A-D route.
Note that if segmented P-tunnels are in use, a BFER might be a
P-tunnel segmentation border router rather than an egress PE, or a
BFER might be both an egress PE and a P-tunnel segmentation border
router.
Depending upon the role of the BFER for given packet, it may need to
follow the procedures of Section 4.2.1, the procedures of
Section 4.2.2, or both.
4.2.1. At a BFER that is an Egress PE
When a BFER receives an MVPN multicast data packet that has been
BIER-encapsulated, it determines from the MPLS label at the top of
the packet's label stack whether it is an egress PE for the packet or
not. If it is an egress PE, the BIER layer passes the following
information to the multicast flow layer:
o The BFR-prefix corresponding to the sub-domain-id and BFIR-id in
the BIER header.
o The "payload", which is an MPLS packet whose top label is an
upstream-assigned label. The BFR-prefix provides the "context" in
which the upstream-assigned label is interpreted.
Note that per [RFC5331], the context for an upstream-assigned
label is the IP address of the label assigner, which in this case
is the BFR-prefix of the BFIR.
4.2.2. At a BFER that is a P-tunnel Segmentation Boundary
When segmented P-tunnels are being used, a BFER that receives a BIER-
encapsulated MVPN multicast data packet may need to be forwarded on
its next P-tunnel segment. The choice of the next P-tunnel segment
for the packet depends upon the C-flow to which the packet belongs.
Since the BFIR assigns a distinct upstream-assigned MPLS label for
each C-flow, the BFER can select the proper "next P-tunnel segment"
for a given packet simply by looking up the upstream-assigned label
that immediately follows the BIER header. (If the BFIR had not
assigned a distinct label to each C-flow, the BFER would need to
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maintain all the state from the Multicast Flow Overlay in order to
select the next P-tunnel segment.)
5. Contributor Addresses
Below is a list of other contributing authors in alphabetical order:
IJsbrand Wijnands
Cisco Systems, Inc.
De Kleetlaan 6a
Diegem 1831
Belgium
Email: ice@cisco.com
6. Acknowledgments
The authors wish to thank Jeffrey Zhang for his ideas and
contributions to this work.
7. IANA Considerations
IANA is requested to assign a value for "BIER" from the "P-Multicast
Service Interface Tunnel (PMSI Tunnel) Tunnel Types" registry. The
reference should be this document.
8. Security Considerations
The security considerations of [BIER_ARCH], [BIER_ENCAPS], [RFC6513]
and [RFC6514] are applicable.
9. References
9.1. Normative References
[BIER_ARCH]
Wijnands, IJ., Rosen, E., Dolganow, A., Przygienda, T.,
and S. Aldrin, "Multicast using Bit Index Explicit
Replication", internet-draft draft-ietf-bier-architecture-
03, January 2016.
[BIER_ENCAPS]
Wijnands, IJ., Rosen, E., Dolganow, A., Tantsura, J., and
S. Aldrin, "Encapsulation for Bit Index Explicit
Replication in MPLS Networks", internet-draft draft-ietf-
bier-mpls-encapsulation-04.txt, April 2016.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <http://www.rfc-editor.org/info/rfc4364>.
[RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
Label Assignment and Context-Specific Label Space",
RFC 5331, DOI 10.17487/RFC5331, August 2008,
<http://www.rfc-editor.org/info/rfc5331>.
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <http://www.rfc-editor.org/info/rfc6513>.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
<http://www.rfc-editor.org/info/rfc6514>.
[RFC6625] Rosen, E., Ed., Rekhter, Y., Ed., Hendrickx, W., and R.
Qiu, "Wildcards in Multicast VPN Auto-Discovery Routes",
RFC 6625, DOI 10.17487/RFC6625, May 2012,
<http://www.rfc-editor.org/info/rfc6625>.
9.2. Informative References
[EXPLICIT_TRACKING]
Dolganow, A., Kotalwar, J., Rosen, E., and Z. Zhang,
"Explicit Tracking with Wild Card Routes in Multicast
VPN", internet-draft draft-ietf-bess-mvpn-expl-track-00,
June 2016.
[]
Rekhter, Y., Rosen, E., Aggarwal, R., Cai, Y., and T.
Morin, "Extranet Multicast in BGP/IP MPLS VPNs", internet-
draft draft-ietf-bess-mvpn-extranet-07, April 2016.
[RFC7524] Rekhter, Y., Rosen, E., Aggarwal, R., Morin, T.,
Grosclaude, I., Leymann, N., and S. Saad, "Inter-Area
Point-to-Multipoint (P2MP) Segmented Label Switched Paths
(LSPs)", RFC 7524, DOI 10.17487/RFC7524, May 2015,
<http://www.rfc-editor.org/info/rfc7524>.
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Authors' Addresses
Eric C. Rosen (editor)
Juniper Networks, Inc.
10 Technology Park Drive
Westford, Massachusetts 01886
United States
Email: erosen@juniper.net
Mahesh Sivakumar
Cisco Systems, Inc.
510 McCarthy Blvd
Milpitas, California 95035
United States
Email: masivaku@cisco.com
Sam K Aldrin
Google, Inc.
1600 Amphitheatre Parkway
Mountain View, California
United States
Email: aldrin.ietf@gmail.com
Andrew Dolganow
Alcatel-Lucent
600 March Rd.
Ottawa, Ontario K2K 2E6
Canada
Email: andrew.dolganow@alcatel-lucent.com
Tony Przygienda
Ericsson
300 Holger Way
San Jose, California 95134
United States
Email: antoni.przygienda@ericsson.com
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