draft-ietf-bier-architecture-04.txt   draft-ietf-bier-architecture-05.txt 
Internet Engineering Task Force IJ. Wijnands, Ed. Internet Engineering Task Force IJ. Wijnands, Ed.
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track E. Rosen, Ed. Intended status: Standards Track E. Rosen, Ed.
Expires: January 19, 2017 Juniper Networks, Inc. Expires: May 1, 2017 Juniper Networks, Inc.
A. Dolganow A. Dolganow
Nokia Nokia
T. Przygienda T. Przygienda
Juniper Networks, Inc. Juniper Networks, Inc.
S. Aldrin S. Aldrin
Google, Inc. Google, Inc.
July 18, 2016 October 28, 2016
Multicast using Bit Index Explicit Replication Multicast using Bit Index Explicit Replication
draft-ietf-bier-architecture-04 draft-ietf-bier-architecture-05
Abstract Abstract
This document specifies a new architecture for the forwarding of This document specifies a new architecture for the forwarding of
multicast data packets. It provides optimal forwarding of multicast multicast data packets. It provides optimal forwarding of multicast
packets through a "multicast domain". However, it does not require a packets through a "multicast domain". However, it does not require a
protocol for explicitly building multicast distribution trees, nor protocol for explicitly building multicast distribution trees, nor
does it require intermediate nodes to maintain any per-flow state. does it require intermediate nodes to maintain any per-flow state.
This architecture is known as "Bit Index Explicit Replication" This architecture is known as "Bit Index Explicit Replication"
(BIER). When a multicast data packet enters the domain, the ingress (BIER). When a multicast data packet enters the domain, the ingress
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 19, 2017. This Internet-Draft will expire on May 1, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The BFR Identifier and BFR-Prefix . . . . . . . . . . . . . . 6 2. The BFR Identifier and BFR-Prefix . . . . . . . . . . . . . . 6
3. Encoding BFR Identifiers in BitStrings . . . . . . . . . . . 6 3. Encoding BFR Identifiers in BitStrings . . . . . . . . . . . 7
4. Layering . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4. Layering . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. The Routing Underlay . . . . . . . . . . . . . . . . . . 9 4.1. The Routing Underlay . . . . . . . . . . . . . . . . . . 9
4.2. The BIER Layer . . . . . . . . . . . . . . . . . . . . . 10 4.2. The BIER Layer . . . . . . . . . . . . . . . . . . . . . 10
4.3. The Multicast Flow Overlay . . . . . . . . . . . . . . . 11 4.3. The Multicast Flow Overlay . . . . . . . . . . . . . . . 11
5. Advertising BFR-ids and BFR-Prefixes . . . . . . . . . . . . 11 5. Advertising BFR-ids and BFR-Prefixes . . . . . . . . . . . . 12
6. BIER Intra-Domain Forwarding Procedures . . . . . . . . . . . 13 6. BIER Intra-Domain Forwarding Procedures . . . . . . . . . . . 13
6.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 13 6.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 13
6.2. BFR Neighbors . . . . . . . . . . . . . . . . . . . . . . 14 6.2. BFR Neighbors . . . . . . . . . . . . . . . . . . . . . . 15
6.3. The Bit Index Routing Table . . . . . . . . . . . . . . . 15 6.3. The Bit Index Routing Table . . . . . . . . . . . . . . . 15
6.4. The Bit Index Forwarding Table . . . . . . . . . . . . . 16 6.4. The Bit Index Forwarding Table . . . . . . . . . . . . . 16
6.5. The BIER Forwarding Procedure . . . . . . . . . . . . . . 17 6.5. The BIER Forwarding Procedure . . . . . . . . . . . . . . 17
6.6. Examples of BIER Forwarding . . . . . . . . . . . . . . . 19 6.6. Examples of BIER Forwarding . . . . . . . . . . . . . . . 19
6.6.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . 20 6.6.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . 20
6.6.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . 21 6.6.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . 21
6.7. Equal Cost Multi-path Forwarding . . . . . . . . . . . . 23 6.7. Equal Cost Multi-path Forwarding . . . . . . . . . . . . 23
6.7.1. Non-deterministic ECMP . . . . . . . . . . . . . . . 23 6.7.1. Non-deterministic ECMP . . . . . . . . . . . . . . . 23
6.7.2. Deterministic ECMP . . . . . . . . . . . . . . . . . 24 6.7.2. Deterministic ECMP . . . . . . . . . . . . . . . . . 24
6.8. Prevention of Loops and Duplicates . . . . . . . . . . . 26 6.8. Prevention of Loops and Duplicates . . . . . . . . . . . 26
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that the BFR-ids for each sub-domain be assigned "densely" from the that the BFR-ids for each sub-domain be assigned "densely" from the
numbering space, as this will result in a more efficient encoding numbering space, as this will result in a more efficient encoding
(see Section 3). That is, if there are 256 or fewer BFERs, it is (see Section 3). That is, if there are 256 or fewer BFERs, it is
RECOMMENDED to assign all the BFR-ids from the range [1,256]. If RECOMMENDED to assign all the BFR-ids from the range [1,256]. If
there are more than 256 BFERs, but less than 512, it is RECOMMENDED there are more than 256 BFERs, but less than 512, it is RECOMMENDED
to assign all the BFR-ids from the range [1,512], with as few "holes" to assign all the BFR-ids from the range [1,512], with as few "holes"
as possible in the earlier range. However, in some deployments, it as possible in the earlier range. However, in some deployments, it
may be advantageous to depart from this recommendation; this is may be advantageous to depart from this recommendation; this is
discussed further in Section 3. discussed further in Section 3.
In some deployments, it may not be possible to support (in a given
sub-domain) the full range of 65535 BFR-ids. For example, if the
BFRs in a given sub-domain only support 16 SIs and if they only
support BitStringLengths of 256 or less, then only 16*256=4096 BFR-
ids can be supported in that sub-domain.
3. Encoding BFR Identifiers in BitStrings 3. Encoding BFR Identifiers in BitStrings
To encode a BFR-id in a BIER data packet, one must convert the BFR-id To encode a BFR-id in a BIER data packet, one must convert the BFR-id
to an SI and a BitString. This conversion depends upon the parameter to an SI and a BitString. This conversion depends upon the parameter
we are calling "BitStringLength". The conversion is done as follows. we are calling "BitStringLength". The conversion is done as follows.
If the BFR-id is N, then If the BFR-id is N, then
o SI is the integer part of the quotient (N-1)/BitStringLength o SI is the integer part of the quotient (N-1)/BitStringLength
o The BitString has one bit position set. If the low-order bit is o The BitString has one bit position set. If the low-order bit is
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provisioned with all legal smaller values of BitStringLength as both provisioned with all legal smaller values of BitStringLength as both
Imposition and Disposition BitStringLength. Imposition and Disposition BitStringLength.
In order to support transition from one BitStringLength to another, In order to support transition from one BitStringLength to another,
every BFR MUST be capable of being provisioned to simultaneously use every BFR MUST be capable of being provisioned to simultaneously use
two different Disposition BitStringLengths. two different Disposition BitStringLengths.
A BFR MUST support SI values in the range [0,15], and MAY support SI A BFR MUST support SI values in the range [0,15], and MAY support SI
values in the range [0,255]. ("Supporting the values in a given values in the range [0,255]. ("Supporting the values in a given
range" means, in this context, that any value in the given range is range" means, in this context, that any value in the given range is
legal, and will be properly interpreted.) legal, and will be properly interpreted.) Note that for a given
BitStringLength, the total number of BFR-ids that can be represented
is the product of the BitStringLength and the number of supported
SIs. For example, if a deployment uses (in a given sub-domain) a
BitStringLength of 64 and supports 256 SIs, that deployment can only
support 16384 BFR-ids in that sub-domain. Even a deployment that
supports 256 SIs will not be able to support 65535 BFR-ids unless it
uses a BitStringLength of at least 256.
When a BFIR determines that a multicast data packet, assigned to a When a BFIR determines that a multicast data packet, assigned to a
given sub-domain, needs to be forwarded to a particular set of given sub-domain, needs to be forwarded to a particular set of
destination BFERs, the BFIR partitions that set of BFERs into destination BFERs, the BFIR partitions that set of BFERs into
subsets, where each subset contains the target BFERs whose BFR-ids in subsets, where each subset contains the target BFERs whose BFR-ids in
the given sub-domain all resolve to the same SI. Call these the the given sub-domain all resolve to the same SI. Call these the
"SI-subsets" for the packet. Each SI-subset can be represented by a "SI-subsets" for the packet. Each SI-subset can be represented by a
single BitString. The BFIR creates a copy of the packet for each single BitString. The BFIR creates a copy of the packet for each
SI-subset. The BIER encapsulation is then applied to each packet. SI-subset. The BIER encapsulation is then applied to each packet.
The encapsulation specifies a single SI for each packet, and contains The encapsulation specifies a single SI for each packet, and contains
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11.2. Informative References 11.2. Informative References
[Boivie_Feldman] [Boivie_Feldman]
Boivie, R. and N. Feldman, "Small Group Multicast", Boivie, R. and N. Feldman, "Small Group Multicast",
(expired) draft-boivie-sgm-02.txt, February 2001. (expired) draft-boivie-sgm-02.txt, February 2001.
[ISIS_BIER_EXTENSIONS] [ISIS_BIER_EXTENSIONS]
Ginsberg, L., Przygienda, T., Aldrin, S., and J. Zhang, Ginsberg, L., Przygienda, T., Aldrin, S., and J. Zhang,
"BIER Support via ISIS", internet-draft draft-ietf-bier- "BIER Support via ISIS", internet-draft draft-ietf-bier-
isis-extensions-02.txt, March 2016. isis-extensions-03.txt, September 2016.
[MPLS_BIER_ENCAPS] [MPLS_BIER_ENCAPS]
Wijnands, IJ., Rosen, E., Dolganow, A., Tantsura, J., Wijnands, IJ., Rosen, E., Dolganow, A., Tantsura, J.,
Aldrin, S., and I. Meilik, "Encapsulation for Bit Index Aldrin, S., and I. Meilik, "Encapsulation for Bit Index
Explicit Replication in MPLS Networks", internet-draft Explicit Replication in MPLS Networks", internet-draft
draft-ietf-bier-mpls-encapsulation-05.txt, July 2016. draft-ietf-bier-mpls-encapsulation-05.txt, July 2016.
[OSPF_BIER_EXTENSIONS] [OSPF_BIER_EXTENSIONS]
Psenak, P., Kumar, N., Wijnands, IJ., Dolganow, A., Psenak, P., Kumar, N., Wijnands, IJ., Dolganow, A.,
Przygienda, T., Zhang, J., and S. Aldrin, "OSPF Extensions Przygienda, T., Zhang, J., and S. Aldrin, "OSPF Extensions
for Bit Index Explicit Replication", internet-draft draft- for Bit Index Explicit Replication", internet-draft draft-
ietf-ospf-bier-extensions-02.txt, March 2016. ietf-ospf-bier-extensions-04.txt, September 2016.
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/ [RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <http://www.rfc-editor.org/info/rfc6513>. 2012, <http://www.rfc-editor.org/info/rfc6513>.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
<http://www.rfc-editor.org/info/rfc6514>. <http://www.rfc-editor.org/info/rfc6514>.
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