Internet DRAFT - draft-rosen-l3vpn-mvpn-bier
draft-rosen-l3vpn-mvpn-bier
Internet Engineering Task Force E. Rosen, Ed.
Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track M. Sivakumar
Expires: June 7, 2015 IJ. Wijnands
Cisco Systems, Inc.
S. Aldrin
Huawei Technologies
A. Dolganow
Alcatel-Lucent
T. Przygienda
Ericsson
December 4, 2014
Multicast VPN Using BIER
draft-rosen-l3vpn-mvpn-bier-02
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 June 7, 2015.
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Copyright Notice
Copyright (c) 2014 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Use of the PMSI Tunnel Attribute . . . . . . . . . . . . . . 4
3. Explicit Tracking . . . . . . . . . . . . . . . . . . . . . . 6
4. Data Plane . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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
"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.
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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 [SEAMLESS_MCAST]. 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
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.
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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
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.)
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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 "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.
* 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.
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.
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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
[Editor's note: The procedures of this section are still under
discussion, and significant changes may be expected in the next
revision.]
When using BIER to transport an MVPN data packet through a BIER
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
delivered. This is done by using the explicit tracking mechanism
specified in [RFC6513] and [RFC6514].
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".
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4. Data Plane
The MVPN application plays the role of the "multicast flow layer" as
described in [BIER_ARCH].
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 forwarded according
to the procedures of [BIER_ARCH] and [BIER_ENCAPS]. (See especially
Section 4, "Imposing and Processing the BIER Encapsulation", of
[BIER_ENCAPS].)
When a BFER receives an MVPN multicast data packet that has been
BIER-encapsulated, 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.
5. Acknowledgments
The authors wish to thank Jeffrey Zhang for his ideas and
contributions to this work.
6. 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.
7. Security Considerations
The security considerations of [BIER_ARCH], [BIER_ENCAPS], [RFC6513]
and [RFC6514] are applicable.
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8. References
8.1. Normative References
[BIER_ARCH]
Wijnands, IJ., "Multicast using Bit Index Explicit
Replication Architecture", internet-draft draft-wijnands-
bier-architecture-02, December 2014.
[BIER_ENCAPS]
Wijnands, IJ., "Multicast using Bit Index Explicit
Replication Architecture", internet-draft draft-wijnands-
mpls-bier-encapsulation-02, December 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
Label Assignment and Context-Specific Label Space", RFC
5331, August 2008.
[RFC6513] Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
VPNs", RFC 6513, February 2012.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, February 2012.
[RFC6625] Rosen, E., Rekhter, Y., Hendrickx, W., and R. Qiu,
"Wildcards in Multicast VPN Auto-Discovery Routes", RFC
6625, May 2012.
8.2. Informative References
[EXTRANET]
Rekhter, Y. and E. Rosen, "Extranet Multicast in BGP/IP
MPLS VPNs", internet-draft draft-ietf-l3vpn-mvpn-extranet-
05, July 2014.
[SEAMLESS_MCAST]
Rekhter, Y., Aggarwal, R., Morin, T., Grosclaude, I.,
Leymann, N., and S. Saad, "Inter-Area P2MP Segmented
LSPs", internet-draft draft-ietf-mpls-seamless-mcast-14,
June 2014.
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Authors' Addresses
Eric C. Rosen (editor)
Juniper Networks, Inc.
10 Technology Park Drive
Westford, Massachusetts 01886
US
Email: erosen@juniper.net
Mahesh Sivakumar
Cisco Systems, Inc.
510 McCarthy Blvd
Milpitas, California 95035
US
Email: masivaku@cisco.com
IJsbrand Wijnands
Cisco Systems, Inc.
De Kleetlaan 6a
Diegem 1831
BE
Email: ice@cisco.com
Sam K Aldrin
Huawei Technologies
2330 Central Express Way
Santa Clara, California
US
Email: aldrin.ietf@gmail.com
Andrew Dolganow
Alcatel-Lucent
600 March Rd.
Ottawa, Ontario K2K 2E6
CA
Email: andrew.dolganow@alcatel-lucent.com
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Tony Przygienda
Ericsson
300 Holger Way
San Jose, California 95134
US
Email: antoni.przygienda@ericsson.com
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