Networking Working Group Ran. Chen
Internet-Draft Zheng. Zhang
Intended status: Standards Track ZTE Corporation
Expires: November 11, 2019 Vengada. Govindan
IJsbrand. Wijnands
Cisco
MAY 10, 2019
BGP Link-State extensions for BIER
draft-ietf-bier-bgp-ls-bier-ext-05
Abstract
Bit Index Explicit Replication (BIER) is an architecture that
provides optimal multicast forwarding through a "BIER domain" without
requiring intermediate routers to maintain any multicast related per-
flow state. BIER also does not require any explicit tree-building
protocol for its operation. A multicast data packet enters a BIER
domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the
BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs).
The BFIR router adds a BIER header to the packet. The BIER header
contains a bitstring in which each bit represents exactly one BFER to
forward the packet to. The set of BFERs to which the multicast
packet needs to be forwarded is expressed by setting the bits that
correspond to those routers in the BIER header.
This document specifies extensions to the BGP Link-state address-
family in order to advertising BIER information.
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
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Drafts is at https://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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 11, 2019.
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Copyright Notice
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. BGP-LS Extensions for BIER . . . . . . . . . . . . . . . . . 3
3.1. The BIER TLV . . . . . . . . . . . . . . . . . . . . . . 3
3.2. The BIER MPLS Encapsulation Sub-TLV . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. Normative references . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Bit Index Explicit Replication (BIER) is an architecture that
provides optimal multicast forwarding through a "BIER domain" without
requiring intermediate routers to maintain any multicast related per-
flow state. BIER also does not require any explicit tree-building
protocol for its operation. A multicast data packet enters a BIER
domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the
BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs).
The BFIR router adds a BIER header to the packet. The BIER header
contains a bitstring in which each bit represents exactly one BFER to
forward the packet to. The set of BFERs to which the multicast
packet needs to be forwarded is expressed by setting the bits that
correspond to those routers in the BIER header.
This document specifies extensions to the BGP Link-state address-
family in order to advertising BIER-specific. An external component
(e.g., a controller) then can collect BIER information in the
"northbound" direction within the BIER domain.
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2. Conventions used in this document
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 RFC2119.
3. BGP-LS Extensions for BIER
Each BFR MUST be assigned a "BFR-Prefix". A BFR's BFR-Prefix MUST be
an IP address (either IPv4 or IPv6) of the BFR, and MUST be unique
and routable within the BIER domain as described in section 2 of
[RFC8279], and then external component (e.g., a controller) need to
collect BIER information of BIER routers are associated with the BFR-
Prefix in the "northbound" direction within the BIER domain.
Given that the BIER information is associated with the prefix, the
BGP-LS Prefix Attribute TLV [RFC7752] can be used to carry the BIER
information. A new Prefix Attribute TLV and Sub-TLV are defined for
the encoding of BIER information.
3.1. The BIER TLV
A new Prefix Attribute TLV (defined in [RFC7752] is defined for
distributing BIER information. The new TLV is called the BIER TLV.
The BIER TLVs may appear multiple times.
The following BIER TLV is defined:
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 | MT-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BFR-id | BS Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
Figure 1
Type:as indicated in IANA Considerations section.
Length: 2 octet.
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Reserved: MUST be 0 on transmission, ignored on reception. May be
used in future versions.
BAR: A 1 octet field encoding the BIER Algorithm, used to calculate
underlay paths to reach BFERs. Values are allocated from the "BIER
Algorithms" registry which is defined in [RFC8401].
IPA: A 1 octet field encoding the IGP Algorithm, used 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.
Subdomain-id: Unique value identifying the BIER sub-domain, 1 octet.
MT-ID: Multi-Topology ID that identifies the topology that is
associated with the BIER sub-domain.1 octet.
BFR-id: A 2 octet field encoding the BFR-id, as documented in
[RFC8279]. If the BFR-id is zero, it means, the advertising router
is not advertising any BIER-id.In some environment, BFR-id can be
configured by NMS, The BFR-id should be sent to a controller.
BS Length: A 1 octet field encoding the Bitstring length as per
[RFC8296].
If the MT-ID value is outside of the values specified in [RFC4915],
the BIER Sub-TLV MUST be ignored.
3.2. The BIER MPLS Encapsulation Sub-TLV
The BIER MPLS Encapsulation Sub-TLV is a sub-TLV of the BIER TLV.
BIER MPLS Encapsulation Sub-TLV is used in order to advertise MPLS
specific information used for BIER. It MUST appear multiple times in
the BIER TLV as described in [RFC8444]
In some environment, each router allocates its labels, and advertises
it to the controller.That solution is simpler as the controller does
not need to deal with label allocation. If the controller has to
deal with Label allocation , there needs to be a (global) range
carved out such there are no conflicts. We can avoid all that by
having the router allocate the BIER Label range and advertise it to
the controller.
The following the BIER MPLS Encapsulation Sub-TLV is defined:
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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 | Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BS Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2
Type: as indicated in IANA Considerations section.
Length: 2 octet.
Max SI: A 1 octet field encoding the maximum Set Identifier(as
defined in [RFC8279]), used in the encapsulation for this BIER
subdomain for this BitString length.
Label: A 3 octet field, where the 20 rightmost bits represent the
first label in the label range.
BS Length: A 1 octet field encoding the Bitstring length as per
[RFC8296]
BS length in multiple BIER MPLS Encapsulation Sub-TLV inside the same
BIER Sub-TLV MUST NOT repeat, otherwise only the first BIER MPLS
Encapsulation Sub-TLV with such BS length MUST be used and any
subsequent BIER MPLS Encapsulation Sub-TLVs with the same BS length
MUST be ignored.
4. IANA Considerations
This document requests assigning code-points from the registry for
the new Prefix Attribute TLV and Sub-TLV.
+-------------------+---------------+-----------------+
| TLV Code Point | Description | Value defined |
+-------------------+---------------+-----------------+
| 1174( recommend ) | BIER | this document |
+-------------------+---------------+-----------------+
Table 1: The new Prefix Attribute TLV
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+-----------------+-------------------------------+-----------------+
| Sub-TLV | Description | Value |
| Code Point | | |
+-----------------+-------------------------------+-----------------+
| 1 ( recommend) | BIER MPLS Encapsulation | this document |
+------------+-------------------------------+----------------------+
Table 2: The new Prefix Attribute Sub-TLV
5. Security Considerations
Procedures and protocol extensions defined in this document do not
affect the BGP security model. See [RFC6952] for details.
6. Acknowledgements
We would like to thank Peter Psenak (Cisco) for his comments and
support of this work.
7. Normative references
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<https://www.rfc-editor.org/info/rfc3630>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<https://www.rfc-editor.org/info/rfc4915>.
[RFC6952] Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
BGP, LDP, PCEP, and MSDP Issues According to the Keying
and Authentication for Routing Protocols (KARP) Design
Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
<https://www.rfc-editor.org/info/rfc6952>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
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[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>.
Authors' Addresses
Ran Chen
ZTE Corporation
No.50 Software Avenue,Yuhuatai District
Nanjing, Jiangsu Province 210012
China
Phone: +86 025 88014636
Email: chen.ran@zte.com.cn
Zheng Zhang
ZTE Corporation
No.50 Software Avenue,Yuhuatai District
Nanjing, Jiangsu Province 210012
China
Email: zhang.zheng@zte.com.cn
Vengada Prasad Govindan
Cisco
Email: venggovi@cisco.com
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IJsbrand Wijnands
Cisco
De Kleetlaan 6a
Diegem 1831
Belgium
Email: ice@cisco.com
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