Internet DRAFT - draft-nainar-bier-flex-algo
draft-nainar-bier-flex-algo
Internet Engineering Task Force N. Kumar
Internet-Draft IJ. Wijnands
Intended status: Informational M. Mishra
Expires: May 7, 2020 Cisco
November 4, 2019
Flex Algorithm for BIER
draft-nainar-bier-flex-algo-00
Abstract
Bit Index Explicit Replication (BIER) is an architecture that
provides optimal multicast forwarding through a "BIER domain" without
requiring intermediate routers to run explicit tree-building protocol
or to maintain multicast-related, per-flow state. IGP protocols are
extended to carry BFR-Id and other encapsulation informations that
are used by traditional path computing algorithm using link metric
for a loop-free best path selection.
This document defines a constrained based path selection using IGP
flexible Algorithm for BIER.
Requirements Language
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 RFC
2119 [RFC2119] RFC 8174 [RFC8174] when and only when, they appear in
all capitals, as shown here.
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 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
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 May 7, 2020.
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Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Acronyms and Terminology . . . . . . . . . . . . . . . . 3
1.1.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Terminology . . . . . . . . . . . . . . . . . . . . . 3
2. Flexible Algorithm . . . . . . . . . . . . . . . . . . . . . 3
3. Constraint Forwarding Identifier . . . . . . . . . . . . . . 4
3.1. BFR ID Mapping for Flexible Algorithm . . . . . . . . . . 4
3.2. BIER-MPLS Label Mapping for Flexiblem Algorithm . . . . . 5
4. IGP Extensions Flexible Algorithm . . . . . . . . . . . . . . 6
4.1. ISIS . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
[RFC8279] defines Bit Index Explicit Replication (BIER), an
architecture that provides optimal multicast forwarding through a
"BIER domain" without requiring intermediate routers to run explicit
tree-building protocol or to maintain multicast-related, per-flow
state. [RFC8401] and [RFC8444] defines the IGP protocols extensions
to carry BFR-Id and other encapsulation informations that are used by
traditional path computing algorithm using link metric for a loop-
free best path selection.
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The ability to compute constrained path using attributes beyond the
basic link metric and steering the multicast traffic over such
constrained path brings a lot of benefits such as efficient load
distribution, path dis-jointness and resiliency. Bandwidth-aware,
delay-sensitive or multi-planar are some of the examples for such
constrained path selection. The path computation and traffic
steering over flexible algorithm based constrained path requires
advertising a set of Path constraints associated to each link and a
unique dataplane based identifier to differentiate the data packets
that needs to be steered over such computed constrained paths.
This document specifies the IGP protocol extensions and the mechanism
to implement IGP Flexible Algorithm for BIER network.
1.1. Acronyms and Terminology
1.1.1. Acronyms
TBD
1.1.2. Terminology
This document uses the terminologies defined in [RFC8279], [RFC8296],
and so the readers are expected to be familiar with the same.
2. Flexible Algorithm
Different types of contraints may be used to compute a path over the
BIER network. Link performance and multi-plane are some of the
common examples for such constraints. An example multiplane BIER
network is shown in below figure 1.
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+---(gBFR1)--------------(gBFR2)
/ + +
/ | \ | \
/ | \ | \
(BFIR) | (gBFR3)------------~(gBFR4)------+
\ | + | + \
\ | | | | \
\ + | | | \
+----(rBFR1)--------------(rBFR2) | (BFER)
+ | + | /
\ | \ | /
\ | \ | /
+ + /
(rBFR3)---------------(rBFR4)---+
Figure 1. MultiPlane BIER Network
The above BIER network is enabled with "green" and "red" planes by
assigning a contiguous set of BFRs to each plane. For example,
gBFR1, gBFR2, gBFR3 and gBFR4 belongs to "green" plane while rBFR1,
rBFR2, rBFR3 and rBFR$ belong sto "red" plane. BFIR and BFER are
enabled with both the planes.
Any BFR must have a mechanism to identify the set of constraints
associated to each algorithm so that a loop free path can be
computed. Any BFR must have a mechanism to map the data packet to
the associated constrained path for loop free constrained forwarding.
3. Constraint Forwarding Identifier
This section explains different mechanism for identifying the
constraints forwarding in the BIER encapsulated data packet.
3.1. BFR ID Mapping for Flexible Algorithm
For each Flexible Algorithm, a domain wide unique BFR-ID will be
assigned with BFR-Prefix for each participating BFER within the BIER
domain.
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+---(gBFR1)--------------(gBFR2)
/ + +
/ | \ | \
/ | \ | \
(BFIR) | (gBFR3)------------~(gBFR4)------+
\ | + | + \
\ | | | | \
\ + | | | \
+----(rBFR1)--------------(rBFR2) | (BFER) (0001 = red)
+ | + | / (0010 = green)
\ | \ | /
\ | \ | /
+ + /
(rBFR3)---------------(rBFR4)---+
Figure 2. BFR-ID Mapping
Each BFER is assigned with domain wide unique BFR-ID for each
Flexible Algorithm. In Figure 2, BFER assigns 0001 for "red" plane
while using 0010 for "green" plane. Any BFR participating in one
plane may not have the BFR-ID associated with other planes.
BFIR pushes the relevant BFR-ID to enforce the forwarding over any
specific contraint path which can be influenced by a local policy.
3.2. BIER-MPLS Label Mapping for Flexiblem Algorithm
For each Flexible Algorithm, a locally unique BIER-MPLS label is
assigned by each participating BFR within the BIER domain. In this
option, each BFER is assigned with just one BFR-ID as mentioned in
[RFC8279].
+---(gBFR1)--------------(gBFR2)
/ + +
/ | \ | \
/ | \ | \
(BFIR) | (gBFR3)------------~(gBFR4)------+
\ | + | + \
\ | | | | \
\ + | | | \ (BFR-ID = 0001)
+----(rBFR1)--------------(rBFR2) | (BFER) (L1 = red)
+ | + | / (L2 = green)
\ | \ | /
\ | \ | /
+ + /
(rBFR3)---------------(rBFR4)---+
Figure 3. BIER-MPLS Label Mapping
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Each BFR is assigned with locally unique BIER-MPLS for each Flexible
Algorithm. The BIER-MPLS label along with the relevant constraints
are advertised to other BFR using extensions defined in section x.
In Figure 3, BFER is assigned with BFR-ID of 1 and advertise BIER-
MPLS label L1 for "red" plane and L2 for "green" plane.
BFIR pushes the relevant BIER-MPLS advertised by the nexthop. Any
BFR participating in both the plane will have the forwarding
instruction for both the planes populated in different BIFT. The
incoming BIER-MPLS label is used to identify the plane and the BIFT
to perform the lookup and forwarding.
Additional details about non-MPLS BIER encapsulation will be included
in later revisions.
4. IGP Extensions Flexible Algorithm
This section defines the IGP protocol extensions for BIER Flexible
Algorithm.
4.1. ISIS
4.2. OSPF
5. Security Considerations
To be Updated.
6. IANA Considerations
TBD.
7. Acknowledgements
To be Updated.
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>.
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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>.
[RFC8459] Dolson, D., Homma, S., Lopez, D., and M. Boucadair,
"Hierarchical Service Function Chaining (hSFC)", RFC 8459,
DOI 10.17487/RFC8459, September 2018,
<https://www.rfc-editor.org/info/rfc8459>.
8.2. Informative References
[I-D.ietf-lsr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
algo-04 (work in progress), September 2019.
Authors' Addresses
Nagendra Kumar
Cisco Systems, Inc.
Email: naikumar@cisco.com
Ijsbrand Wijnands
Cisco Systems, Inc.
Email: iwijnand@cisco.com
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Mankamana Mishra
Cisco Systems, Inc.
Email: mankamis@cisco.com
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