Internet DRAFT - draft-zhang-bier-babel-extensions
draft-zhang-bier-babel-extensions
BIER WG Z. Zhang
Internet-Draft ZTE Corporation
Intended status: Standards Track A. Przygienda
Expires: 26 July 2024 Juniper Networks
23 January 2024
BIER in BABEL
draft-zhang-bier-babel-extensions-10
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
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 July 2024.
Copyright Notice
Copyright (c) 2024 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 (https://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
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and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Conventions Used in This Document . . . . . . . . . . . . . . 3
4. Advertisement of BIER information . . . . . . . . . . . . . . 3
4.1. BIER BFR-prefix and BIER sub-TLV . . . . . . . . . . . . 3
4.1.1. BIER sub-TLV . . . . . . . . . . . . . . . . . . . . 3
4.2. BIER MPLS Encapsulation sub-sub-TLV . . . . . . . . . . . 4
4.3. BIER non-MPLS Encapsulation sub-sub-TLV . . . . . . . . . 5
4.3.1. BIER IPv6 transportation sub-sub-TLV . . . . . . . . 6
5. Tree types and tunneling . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
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.
[RFC8966] 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] and [RFC8966].
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3. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
4. 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.
4.1. BIER BFR-prefix and BIER sub-TLV
BFR-prefix and according information is carried in a Babel Update TLV
per [RFC8966]. 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.
4.1.1. BIER sub-TLV
The BIER sub-TLV format aligns exactly with the definition and
restrictions in [RFC8401] , [RFC8444] and
[I-D.ietf-bier-ospfv3-extensions]. 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.
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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
* Type: as indicated in IANA section.
* Length: 1 octet. Include the length of BIER sub-TLV and potential
length of the sub-sub-TLVs.
* 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.
* 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.
* subdomain-id: Unique value identifying the BIER sub-domain. 1
octet.
* 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.
4.2. 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],
[RFC8444] and [I-D.ietf-bier-ospfv3-extensions]. 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.
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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
* Type: value of 1 indicating MPLS encapsulation.
* Length: 1 octet
* 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.
* Local BitString Length (BS Len): Encoded BitString length as per
[RFC8296]. 4 bits.
* Label: First label, 20 bits. The labels are as defined in
[RFC8296].
4.3. BIER non-MPLS Encapsulation sub-sub-TLV
The BIER non-MPLS Encapsulation sub-sub-TLV can be carried by BIER
sub-TLV. The format and restrictions are aligned with
[I-D.ietf-bier-lsr-non-mpls-extensions]. 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.
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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 | BIFT-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|BS Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: non-MPLS Encapsulation sub-sub-TLV
* Type: value of 2 indicating non-MPLS encapsulation.
* Length: 1 octet
* Max SI: Maximum Set Identifier (Section 1 of [RFC8279]) used in
the encapsulation for this BIER subdomain for this BitString
length, 1 octet. The first BIFT-id is for SI=0, the second BIFT-
id is for SI=1, etc. If the BIFT-id associated with the Maximum
Set Identifier exceeds the 20-bit range, the sub-sub-TLV MUST be
ignored.
* BIFT-id: A 3-octet field, where the 20 rightmost bits represent
the first BIFT-id in the BIFT-id range. The 4 leftmost bits MUST
be ignored. The "BIFT-id range" is the set of 20-bit values
beginning with the BIFT-id and ending with (BIFT-id + (Max SI)).
These BIFT-id's are used for BIER forwarding as described in
[RFC8279] and [RFC8296].
* Local BitString Length (BS Len): Encoded BitString length as per
[RFC8296]. 4 bits.
4.3.1. BIER IPv6 transportation sub-sub-TLV
The BIER IPv6 transportation sub-sub-TLV can be carried by BIER non-
MPLS Encapsulation sub-sub-TLV. The format and restrictions are
aligned with [I-D.ietf-bier-bierin6]. A node that requires IPv6
encapsualtion MUST advertise the BIER IPv6 transportation sub-sub-TLV
according to local configuration or policy in the BIER domain to
request other BFRs to always use IPv6 encapsulation.
The format is the same with the definition in section 4.1,
[I-D.ietf-bier-bierin6].
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5. 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.
6. Security Considerations
Security considerations discussed in [RFC8296], [RFC8966] apply to
this document.
7. IANA Considerations
A new type of Babel update sub-TLV needs to be defined for BIER
information advertisement.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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>.
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[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>.
[RFC8966] Chroboczek, J. and D. Schinazi, "The Babel Routing
Protocol", RFC 8966, DOI 10.17487/RFC8966, January 2021,
<https://www.rfc-editor.org/info/rfc8966>.
8.2. Informative References
[I-D.ietf-bier-bierin6]
Zhang, Z., Zhang, Z. J., Wijnands, I., Mishra, M. P.,
Bidgoli, H., and G. S. Mishra, "Supporting BIER in IPv6
Networks (BIERin6)", Work in Progress, Internet-Draft,
draft-ietf-bier-bierin6-08, 18 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-bier-
bierin6-08>.
[I-D.ietf-bier-lsr-non-mpls-extensions]
Dhanaraj, S., Yan, G., Wijnands, I., Psenak, P., Zhang, Z.
J., and J. Xie, "LSR Extensions for BIER non-MPLS
Encapsulation", Work in Progress, Internet-Draft, draft-
ietf-bier-lsr-non-mpls-extensions-01, 19 September 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-bier-
lsr-non-mpls-extensions-01>.
[I-D.ietf-bier-ospfv3-extensions]
Psenak, P., Nainar, N. K., and I. Wijnands, "OSPFv3
Extensions for BIER", Work in Progress, Internet-Draft,
draft-ietf-bier-ospfv3-extensions-07, 1 December 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-bier-
ospfv3-extensions-07>.
Authors' Addresses
Zheng(Sandy) Zhang
ZTE Corporation
Email: zhang.zheng@zte.com.cn
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Tony Przygienda
Juniper Networks
Email: prz@juniper.net
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