Internet DRAFT - draft-zzhang-bier-bar-ipa
draft-zzhang-bier-bar-ipa
BIER Z. Zhang
Internet-Draft A. Przygienda
Intended status: Standards Track Juniper Networks
Expires: September 6, 2018 A. Dolganow
H. Bidgoli
Nokia
I. Wijnands
Cisco Systems
A. Gulko
Thomson Reuters
March 5, 2018
BIER Underlay Path Calculation Algorithm and Contraints
draft-zzhang-bier-bar-ipa-00
Abstract
This document specifies general rules for interaction between the BAR
and IPA fields defined in [I-D.ietf-bier-isis-extensions] and
[I-D.ietf-bier-ospf-bier-extensions].
Requirements Language
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.
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
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 September 6, 2018.
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Copyright Notice
Copyright (c) 2018 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
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Table of Contents
1. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. General Rules for the BAR and IPA fields . . . . . . . . . . 3
3.1. When BAR Is Not Used . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Terminologies
Familiarity with BIER protocols and procedures is assumed. Some
terminologies are listed below for convenience.
[To be added].
2. Introduction
In the BIER architecture, packets with a BIER encapsulation header
are forwarded to the neighbors on the underlay paths towards the
BFERs. For each sub-domain, the paths are calculated in the underlay
topology for the sub-domain, following a calculation algorithm
specific to the sub-domain. The <topology, algorithm> could be
congruent or incongruent with unicast. The topology could be a
default topology, a multi-topology [RFC5120] topology. The algorithm
could be a generic IGP algorithm (e.g. SPF) or could be a BIER
specific one defined in the future.
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In [I-D.ietf-bier-isis-extensions] and
[I-D.ietf-bier-ospf-bier-extensions], an 8-bit BAR field and 8-bit
IPA field are defined to signal the BIER specific algorithm and
generic IGP Algorithm respectively and only value 0 is allowed for
both fields currently. This document specifies the general rules for
the two fields and their interaction when either or both fields are
not 0.
3. General Rules for the BAR and IPA fields
For a particular sub-domain, all routers SHOULD be provisioned with
and signal the same BAR and IPA values. When a BFR discovers another
BFR advertising different BAR or IPA value from its own provisioned,
it MUST treat the advertising BFR as incapable of supporting BIER for
the sub-domain. How incapable routers are handled is outside the
scope of this document.
It is expected that both the BAR and IPA values could have both
algorithm and constraints semantics. To generalize, we introduce the
following terms:
o BC: BIER-specific Constraints
o BA: BIER-specific Algorithm
o RC: Generic Routing Constraints
o RA: Generic Routing Algorithm
o BCBA: BC + BA
o RCRA: RC + RA
A BAR value corresponds to a BCBA, and a IPA value corresponds to a
RCRA. Any of the RC/BC/BA could be "NULL", which means there are no
corresponding constraints or algorithm.
For a particular topology X (which could be a default topology or
multit-topolgy topology) that a sub-domain is associated with, a
router calculates the underlay paths according to its provisioned
BCBA and RCRA the following way:
1. Apply the BIER constraints, resulting in BC(X).
2. Apply the routing constraints, resulting in RC(BC(X)).
3. Select the algorithm AG as following:
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A. If BA is NULL, AG is set to RA.
B. If BA is not NULL, AG is set to BA.
4. Run AG on RC(BC(X)).
3.1. When BAR Is Not Used
The BIER Algorithm registry established by
[I-D.ietf-bier-isis-extensions] and also used in
[I-D.ietf-bier-ospf-bier-extensions] has value 0 for "No BIER
specific algorithm is used". That translates to NULL BA and NULL BC.
Following the rules defined above, the IPA value alone identifies the
calculation algorithm and constraints to be used for a particular
sub-domain when BAR is 0.
4. IANA Considerations
No IANA Consideration is requested in this document.
5. Acknowledgements
The authors thanks Alia Atlas, Eric Rosen, Senthil Dhanaraj and many
others for their suggestions and comments. In particular, the BCBA/
RCRA representation for the interaction rules is based on Alia's
write-up.
6. References
6.1. Normative References
[I-D.ietf-bier-isis-extensions]
Ginsberg, L., Przygienda, T., Aldrin, S., and Z. Zhang,
"BIER support via ISIS", draft-ietf-bier-isis-
extensions-09 (work in progress), February 2018.
[I-D.ietf-bier-ospf-bier-extensions]
Psenak, P., Kumar, N., Wijnands, I., Dolganow, A.,
Przygienda, T., Zhang, Z., and S. Aldrin, "OSPF Extensions
for BIER", draft-ietf-bier-ospf-bier-extensions-15 (work
in progress), February 2018.
[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>.
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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>.
6.2. Informative References
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
Authors' Addresses
Zhaohui Zhang
Juniper Networks
EMail: zzhang@juniper.net
Antoni Przygienda
Juniper Networks
EMail: prz@juniper.net
Andrew Dolganow
Nokia
EMail: andrew.dolganow@nokia.com
Hooman Bidgoli
Nokia
EMail: hooman.bidgoli@nokia.com
IJsbrand Wijnands
Cisco Systems
EMail: ice@cisco.com
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Arkadiy Gulko
Thomson Reuters
EMail: arkadiy.gulko@thomsonreuters.com
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