Internet Engineering Task Force L. Ginsberg, Ed.
Internet-Draft Cisco Systems
Intended status: Standards Track A. Przygienda
Expires: April 25, 2018 Juniper Networks
S. Aldrin
Google
J. Zhang
Juniper Networks, Inc.
October 22, 2017
BIER support via ISIS
draft-ietf-bier-isis-extensions-06
Abstract
Specification of an ISIS extension to support BIER domains and sub-
domains.
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 RFC 2119 [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
working documents as Internet-Drafts. The list of current Internet-
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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 April 25, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
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(https://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. BIER Domains and Sub-Domains . . . . . . . . . . . . . . 4
4.2. Advertising BIER Information . . . . . . . . . . . . . . 5
5. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Multi Topology and Sub-Domain . . . . . . . . . . . . . . 5
5.2. Encapsulation . . . . . . . . . . . . . . . . . . . . . . 5
5.3. BIER Algorithm . . . . . . . . . . . . . . . . . . . . . 5
5.4. Label advertisements for MPLS Encapsulation . . . . . . . 6
5.5. BFR-id Advertisements . . . . . . . . . . . . . . . . . . 6
5.6. Reporting Misconfiguration . . . . . . . . . . . . . . . 6
5.7. Flooding Reduction . . . . . . . . . . . . . . . . . . . 6
6. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. BIER Info sub-TLV . . . . . . . . . . . . . . . . . . . . 6
6.2. BIER MPLS Encapsulation sub-sub-TLV . . . . . . . . . . . 7
6.3. Optional BIER sub-domain BSL conversion sub-sub-TLV . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Bit Index Explicit Replication (BIER)
[I-D.draft-ietf-bier-architecture-08] defines an architecture where
all intended multicast receivers are encoded as bitmask in the
Multicast packet header within different encapsulations such as
[I-D.draft-ietf-bier-mpls-encapsulation-10]. A router that receives
such a packet will forward the packet based on the Bit Position in
the packet header towards the receiver(s), following a precomputed
tree for each of the bits in the packet. Each receiver is
represented by a unique bit in the bitmask.
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This document presents necessary extensions to the currently deployed
ISIS for IP [RFC1195] protocol to support distribution of information
necessary for operation of BIER domains and sub-domains. This
document defines a new TLV to be advertised by every router
participating in BIER signaling.
2. Terminology
Some of the terminology specified in
[I-D.draft-ietf-bier-architecture-08] is replicated here and extended
by necessary definitions:
BIER: Bit Index Explicit Replication (The overall architecture of
forwarding multicast using a Bit Position).
BIER-OL: BIER Overlay Signaling. (The method for the BFIR to learn
about BFER's).
BFR: Bit Forwarding Router (A router that participates in Bit Index
Multipoint Forwarding). A BFR is identified by a unique BFR-
prefix in a BIER domain.
BFIR: Bit Forwarding Ingress Router (The ingress border router that
inserts the BM into the packet). Each BFIR must have a valid BFR-
id assigned.
BFER: Bit Forwarding Egress Router. A router that participates in
Bit Index Forwarding as leaf. Each BFER must be a BFR. Each BFER
must have a valid BFR-id assigned.
BFT: Bit Forwarding Tree used to reach all BFERs in a domain.
BIER sub-domain: A further distinction within a BIER domain
identified by its unique sub-domain identifier. A BIER sub-domain
can support multiple BitString Lengths.
BFR-id: An optional, unique identifier for a BFR within a BIER sub-
domain.
Invalid BFR-id: Unassigned BFR-id. The special value 0 is reserved
for this purpose.
BAR BIER Algorithm. Algorithm used to calculate unicast nexthops
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3. IANA Considerations
This document adds the following new sub-TLV to the registry of sub-
TLVs for TLVs 235, 237 [RFC5120] and TLVs 135,236
[RFC5305],[RFC5308].
Value: 32 (suggested - to be assigned by IANA)
Name: BIER Info
This document also introduces a new registry for sub-sub-TLVs for the
BIER Info sub-TLV added above. The registration policy is Expert
Review as defined in [RFC8126]. This registry is part of the "IS-IS
TLV Codepoints" registry. The name of the registry is "sub-sub-TLVs
for BIER Info sub-TLV". The defined values are:
Type Name
---- ----
1 BIER MPLS Encapsulation
3 BIER sub-domain BSL conversion
4. Concepts
4.1. BIER Domains and Sub-Domains
An ISIS signalled BIER domain is aligned with the scope of
distribution of BFR-prefixes that identify the BFRs within ISIS.
ISIS acts in such a case as the supporting BIER underlay.
Within such a domain, the extensions defined in this document
advertise BIER information for one or more BIER sub-domains. Each
sub-domain is uniquely identified by a subdomain-id. Each subdomain
is associated with a single ISIS topology [RFC5120], which may be any
of the topologies supported by ISIS. Local configuration controls
which <MT,SD> pairs are supported by a router. The mapping of sub-
domains to topologies MUST be consistent within a BIER flooding
domain.
Each BIER sub-domain has as its unique attributes the encapsulation
used and the type of tree it is using to forward BIER frames
(currently always SPF). Additionally, per supported bitstring length
in the sub-domain, each router will advertise the necessary label
ranges to support it.
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4.2. Advertising BIER Information
BIER information advertisements are associated with a new sub-TLV in
the extended reachability TLVs. BIER information is always
associated with a host prefix which MUST be a node address for the
advertising node. The following restrictions apply:
o Prefix length MUST be 32 for an IPv4 prefix or 128 for an IPv6
prefix
o When the Prefix Attributes Flags sub-TLV is present N flag MUST be
set. [RFC7794]
o BIER sub-TLVs MUST be included when a prefix reachability
advertisement is leaked between levels.
5. Procedures
5.1. Multi Topology and Sub-Domain
A given sub-domain is supported within one and only one topology.
All routers in the flooding scope of the BIER sub-TLVs MUST advertise
the same sub-domain within the same multi-topology. A router
receiving an <MT,SD> advertisement which does not match the locally
configured pair MUST report a misconfiguration of the received <MT,
SD> pair. All received BIER advertisements associated with the
conflicting <MT, SD> pair MUST be ignored.
5.2. Encapsulation
All routers in the flooding scope of the BIER TLVs MUST advertise the
same encapsulation for a given <MT,SD>. A router discovering
encapsulation advertised that is different from its own MUST report a
misconfiguration of a specific <MT,SD>. All received BIER
advertisements associated with the conflicting <MT, SD> pair MUST be
ignored.
5.3. BIER Algorithm
All routers in the flooding scope of the BIER TLVs MUST advertise a
supported algorithm for a given <MT,SD>. The specified algorithm is
used when calculating the optimal path. Currently only the default
algorithm "SPF" is defined - which has a reserved value of 0. The
supported algorithm MUST be consistent for all routers supporting a
given <MT,SD>. A router receiving an <MT,SD> advertisement with a
BAR which does not match the locally configured value MUST report a
misconfiguration of the received <MT, SD> pair. All received BIER
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advertisements associated with the conflicting <MT, SD> pair MUST be
ignored.
5.4. Label advertisements for MPLS Encapsulation
A router that desires to participate in <MT,SD> MUST advertise for
each bitstring length it supports in <MT,SD> a label range size that
guarantees to cover the maximum BFR-id injected into <MT,SD> (which
implies a certain maximum set id per bitstring length as described in
[I-D.draft-ietf-bier-architecture-08]). Any router that violates
this condition MUST be excluded from BIER BFTs for <MT,SD>.
5.5. BFR-id Advertisements
Each BFER/BFIR MAY advertise with its TLV<MT,SD> the BFR-id that it
has administratively chosen. A valid BFR-id MUST be unique within
the flooding scope of the BIER advertisments. All BFERs/BFIRs MUST
detect advertisement of duplicate valid BFR-IDs for a given <MT, SD>.
When such duplication is detected all of the routers advertising
duplicates MUST be treated as if they did not advertise a valid BFR-
id. This implies they cannot act as BFER or BFIR in that <MT,SD>.
5.6. Reporting Misconfiguration
Whenever an advertisement is received which violates any of the
constraints defined in this document the receiving router MUST report
the misconfiguration. Such reports SHOULD be dampened to avoid
excessive logging output.
5.7. Flooding Reduction
BIER domain information SHOULD change infrequently. Frequent changes
will increase the number of Link State PDU (LSP) updates and
negatively impact performance in the network.
6. Packet Formats
All ISIS BIER information is carried within the TLVs 235, 237
[RFC5120] or TLVs 135 [RFC5305], or TLV 236 [RFC5308].
6.1. BIER Info sub-TLV
This sub-TLV carries the information for the BIER sub-domains that
the router participates in as BFR. This sub-TLV MAY appear multiple
times in a given prefix-reachability TLV - once for each sub-domain
supported in the associated topology.
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The sub-TLV advertises a single <MT,SD> combination followed by
optional sub-sub-TLVs as described in the following sections.
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 | subdomain-id | BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-sub-TLVs (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: as indicated in IANA section.
Length: variable
BAR BIER Algorithm. 0 is the only supported value defined in this
document. Other values may be defined in the future. 8 bits
subdomain-id: Unique value identifying the BIER sub-domain. 1 octet
BFR-id: A 2 octet field encoding the BFR-id, as documented in
[I-D.draft-ietf-bier-architecture-08]. If no BFR-id has been
assigned this field is set to the invalid BFR-id.
6.2. BIER MPLS Encapsulation sub-sub-TLV
This sub-sub-TLV carries the information for the BIER MPLS
encapsulation including the label range for a specific bitstring
length for a certain <MT,SD>. It is advertised within the BIER Info
sub-TLV (Section 6.1) . This sub-sub-TLV MAY appear multiple times
within a single BIER info sub-TLV.
On violation of any of the following conditions, the receiving router
MUST ignore the encapsulating BIER Info sub-TLV.
o Label ranges in multiple sub-sub-TLV MUST NOT overlap.
o Bitstring lengths in multiple sub-sub-TLVs MUST NOT be identical.
o The sub-sub-TLV MUST include the required bitstring lengths
encoded in precisely the same way as in
[I-D.draft-ietf-bier-mpls-encapsulation-10].
o The label range size MUST be greater than 0.
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o All labels in the range MUST represent valid label values
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lbl Range Size|BS Len | Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: value of 1 indicating MPLS encapsulation.
Length: 4
Local BitString Length (BS Len): Encoded bitstring length as per [I-
D.draft-ietf-bier-mpls-encapsulation-10]. 4 bits.
Label Range Size: Number of labels in the range used on
encapsulation for this BIER sub-domain for this bitstring length,
1 octet. The size of the label range is determined by the number
of Set Identifiers (SI) (section 1 of [I-D.ietf-bier-
architecture]) that are used in the network. 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.
Label: First label of the range, 20 bits. The labels are as defined
in [I-D.draft-ietf-bier-mpls-encapsulation-10].
6.3. Optional BIER sub-domain BSL conversion sub-sub-TLV
This sub-sub-TLV indicates whether the BFR is capable of imposing a
different Bit String Length (BSL) than the one it received in a BIER
encapsulated packet. Such a capability may allow future, advanced
tree types which ensure simple migration procedures from one BSL to
another in a given <MT,SD> or prevent stable blackholes in scenarios
where not all routers support the same set of BSLs in a given
<MT,SD>. Conversions are supported only between the set of BSLs
advertised as supported by the router. It is carried within the BIER
Info sub-TLV (Section 6.1). This sub-sub-TLV is optional and its
absence indicates that the router is NOT capable of imposing
different BSLs but will always forward the packet with the BSL
unchanged. This sub-sub-TLV MAY occur at most once in a given BIER
info sub-TLV. If multiple occurences of this sub-sub-TLV are
received in a given BIER info sub-TLV the encapsulating sub-TLV MUST
be ignored.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: value of 3 indicating BIER sub-domain BSL Conversion
Length: 0
7. Security Considerations
Implementations must assure that malformed TLV and Sub-TLV
permutations do not result in errors which cause hard protocol
failures.
8. Acknowledgements
The RFC is aligned with the
[I-D.draft-ietf-bier-ospf-bier-extensions-08] draft as far as the
protocol mechanisms overlap.
Many thanks for comments from (in no particular order) Hannes
Gredler, Ijsbrand Wijnands, Peter Psenak and Chris Bowers.
9. References
9.1. Normative References
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
dual environments", RFC 1195, DOI 10.17487/RFC1195,
December 1990, <https://www.rfc-editor.org/info/rfc1195>.
[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>.
[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>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <https://www.rfc-editor.org/info/rfc5305>.
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[RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
DOI 10.17487/RFC5308, October 2008,
<https://www.rfc-editor.org/info/rfc5308>.
[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
March 2016, <https://www.rfc-editor.org/info/rfc7794>.
9.2. Informative References
[I-D.draft-ietf-bier-architecture-08]
Wijnands et al., IJ., "Stateless Multicast using Bit Index
Explicit Replication Architecture", internet-draft draft-
ietf-bier-architecture-08.txt, Sep 2017.
[I-D.draft-ietf-bier-mpls-encapsulation-10]
Wijnands et al., IJ., "Bit Index Explicit Replication
using MPLS encapsulation", internet-draft draft-ietf-bier-
mpls-encapsulation-10.txt, Sep 2017.
[I-D.draft-ietf-bier-ospf-bier-extensions-08]
Psenak et al., P., "OSPF Extension for Bit Index Explicit
Replication", internet-draft draft-ietf-bier-ospf-bier-
extensions-08.txt, Oct 2017.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Authors' Addresses
Les Ginsberg (editor)
Cisco Systems
510 McCarthy Blvd.
Milpitas, CA 95035
USA
Email: ginsberg@cisco.com
Tony Przygienda
Juniper Networks
Email: prz@juniper.net
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Sam Aldrin
Google
1600 Amphitheatre Parkway
Mountain View, CA
USA
Email: aldrin.ietf@gmail.com
Jeffrey (Zhaohui) Zhang
Juniper Networks, Inc.
10 Technology Park Drive
Westford, MA 01886
USA
Email: zzhang@juniper.net
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