BIER WG Z. Zhang
Internet-Draft ZTE Corporation
Intended status: Standards Track A. Przygienda
Expires: May 6, 2020 Juniper Networks
November 3, 2019
BIER in BABEL
draft-zhang-bier-babel-extensions-02
Abstract
BIER introduces a novel multicast architecture. It does not require
a signaling protocol to explicitly build multicast distribution
trees, nor does it require intermediate nodes to maintain any per-
flow state.
Babel defines a distance-vector routing protocol that operates in a
robust and efficient fashion both in wired as well as in wireless
mesh networks. This document defines a way to carry necessary BIER
signaling information in Babel.
Status of This Memo
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This Internet-Draft will expire on May 6, 2020.
Copyright Notice
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Advertisement of BIER information . . . . . . . . . . . . . . 2
3.1. BIER BFR-prefix and BIER sub-TLV . . . . . . . . . . . . 3
3.1.1. BIER sub-TLV . . . . . . . . . . . . . . . . . . . . 3
3.2. BIER MPLS Encapsulation sub-sub-TLV . . . . . . . . . . . 4
4. Tree types and tunneling . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
[RFC8279] introduces a novel multicast architecture. It does not
require a signaling protocol to explicitly build multicast
distribution trees, nor does it require intermediate nodes to
maintain any per-flow state. All procedures necessary to support
BIER are abbreviated by the "BIER architecture" moniker in this
document.
[I-D.ietf-babel-rfc6126bis] define a distance-vector routing protocol
under the name of "Babel". Babel operates in a robust and efficient
fashion both in ordinary wired as well as in wireless mesh networks.
2. Terminology
The terminology of this documents follows [RFC8279], [RFC6126],
[RFC7557] and [I-D.ietf-babel-rfc6126bis].
3. Advertisement of BIER information
In case a router is configured with BIER information, and Babel is
the routing protocol used, such a router MAY use Babel protocol to
announce the BIER information using the BIER sub-TLV specified below.
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3.1. BIER BFR-prefix and BIER sub-TLV
BFR-prefix and according information is carried in a Babel Update TLV
per [I-D.ietf-babel-rfc6126bis]. A new sub-TLV is defined to convey
further BIER information such as BFR-id, sub-domain-id and BSL. Two
sub-sub-TLVs are carried as payload of BIER sub-TLV.
The mandatory bit of BIER sub-TLV should be set to 0. If a router
cannot recognize a sub-TLV, the router MUST ignore this unknown sub-
TLV.
3.1.1. BIER sub-TLV
The BIER sub-TLV format aligns exactly with the definition and
restrictions in [RFC8401] and [RFC8444]. It is a sub-TLV of Babel
update TLV. The prefix MUST NOT be summarized and the according sub-
TLV MUST be treated as optional and transitive.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BAR | IPA | subdomain-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-sub-TLVs (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BIER sub-TLV
o Type: as indicated in IANA section.
o Length: 1 octet. Include the length of BIER sub-TLV and potential
length of the sub-sub-TLVs.
o BAR: BIER Algorithm. Specifies a BIER-specific algorithm used to
calculate underlay paths to reach BFERs. Values are allocated
from the "BIER Algorithms" registry. 1 octet.
o IPA: IGP Algorithm. Specifies an IGP Algorithm to either modify,
enhance, or replace the calculation of underlay paths to reach
BFERs as defined by the BAR value. Values are from the IGP
Algorithm registry. 1 octet.
o subdomain-id: Unique value identifying the BIER sub-domain. 1
octet.
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o BFR-id: A 2 octet field encoding the BFR-id, as documented in
[RFC8279]. If no BFR-id has been assigned this field is set to
the invalid BFR-id.
3.2. BIER MPLS Encapsulation sub-sub-TLV
The BIER MPLS Encapsulation sub-sub-TLV can be carried by BIER sub-
TLV. The format and restrictions are aligned with [RFC8401] and
[RFC8444]. This sub-sub-TLV carries the information for the BIER
MPLS encapsulation including the label range for a specific BSL for a
certain <MT,SD> pair.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max SI |BS Len | Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: MPLS Encapsulation sub-sub-TLV
o Type: value of 1 indicating MPLS encapsulation.
o Length: 1 octet
o Max SI: Maximum Set Identifier (Section 1 of [RFC8279]) used in
the encapsulation for this BIER subdomain for this BitString
length, 1 octet. Each SI maps to a single label in the label
range. The first label is for SI=0, the second label is for SI=1,
etc. If the label associated with the Maximum Set Identifier
exceeds the 20-bit range, the sub-sub-TLV MUST be ignored.
o Local BitString Length (BS Len): Encoded BitString length as per
[RFC8296]. 4 bits.
o Label: First label, 20 bits. The labels are as defined in
[RFC8296].
4. Tree types and tunneling
Since Babel is performing a diffusion computation, support for
different tree types is not as natural as with link-state protocols.
Hence this specification is assuming that normal Babel reachability
computation is performed without further modifications.
BIER architecture does not rely on all routers in a domain performing
BFR procedures. How to support tunnels that will allow to tunnel
BIER across such routers in Babel is for further study.
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5. Security Considerations
TBD
6. IANA Considerations
A new type of Babel update sub-TLV needs to be defined for BIER
information advertisement.
7. Normative References
[I-D.ietf-babel-rfc6126bis]
Chroboczek, J. and D. Schinazi, "The Babel Routing
Protocol", draft-ietf-babel-rfc6126bis-15 (work in
progress), October 2019.
[RFC6126] Chroboczek, J., "The Babel Routing Protocol", RFC 6126,
DOI 10.17487/RFC6126, April 2011,
<https://www.rfc-editor.org/info/rfc6126>.
[RFC7557] Chroboczek, J., "Extension Mechanism for the Babel Routing
Protocol", RFC 7557, DOI 10.17487/RFC7557, May 2015,
<https://www.rfc-editor.org/info/rfc7557>.
[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>.
[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>.
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Authors' Addresses
Zheng(Sandy) Zhang
ZTE Corporation
No. 50 Software Ave, Yuhuatai Distinct
Nanjing
China
Email: zhang.zheng@zte.com.cn
Tony Przygienda
Juniper Networks
Email: prz@juniper.net
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