One document matched: draft-ietf-bier-isis-extensions-02.xml
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<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
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<?rfc tocdepth="3"?>
<?rfc tocindent="yes"?>
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<?rfc compact="yes"?>
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<rfc category="std" docName="draft-ietf-bier-isis-extensions-02"
ipr="trust200902" obsoletes="" submissionType="IETF" updates=""
xml:lang="en">
<front>
<title abbrev="draft-ietf-bier-isis-extensions-02">BIER support via
ISIS</title>
<author fullname="Les Ginsberg" initials="L." role="editor"
surname="Ginsberg">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>510 McCarthy Blvd.</street>
<city>Milpitas</city>
<region>CA</region>
<code>95035</code>
<country>USA</country>
</postal>
<phone/>
<facsimile/>
<email>ginsberg@cisco.com</email>
<uri/>
</address>
</author>
<author fullname="Tony Przygienda" initials="A." surname="Przygienda">
<organization>Ericsson</organization>
<address>
<postal>
<street>300 Holger Way</street>
<city>San Jose</city>
<region>CA</region>
<code>95134</code>
<country>USA</country>
</postal>
<phone/>
<facsimile/>
<email>antoni.przygienda@ericsson.com</email>
<uri/>
</address>
</author>
<author fullname="Sam Aldrin" initials="S." surname="Aldrin">
<organization>Google</organization>
<address>
<postal>
<street>1600 Amphitheatre Parkway</street>
<city>Mountain View</city>
<region>CA</region>
<country>USA</country>
</postal>
<phone/>
<facsimile/>
<email>aldrin.ietf@gmail.com</email>
<uri/>
</address>
</author>
<author fullname="Jeffrey (Zhaohui) Zhang" initials="J." surname="Zhang">
<organization>Juniper Networks, Inc.</organization>
<address>
<postal>
<street>10 Technology Park Drive</street>
<city>Westford</city>
<region>MA</region>
<code>01886</code>
<country>USA</country>
</postal>
<phone/>
<facsimile/>
<email>zzhang@juniper.net</email>
<uri/>
</address>
</author>
<date day="19" month="March" year="2016"/>
<workgroup>Internet Engineering Task Force</workgroup>
<abstract>
<t>Specification of an ISIS extension to support BIER domains and
sub-domains.</t>
</abstract>
<note title="Requirements Language">
<t>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 <xref format="default"
pageno="false" target="RFC2119">RFC 2119</xref> .</t>
</note>
</front>
<middle>
<section title="Introduction" toc="default">
<t>Bit Index Explicit Replication (BIER) <xref format="default"
pageno="false" target="I-D.draft-ietf-bier-architecture-03"/> defines an
architecture where all intended multicast receivers are encoded as
bitmask in the Multicast packet header within different encapsulations
such as <xref format="default" pageno="false"
target="I-D.draft-ietf-bier-mpls-encapsulation-03"/>. 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.</t>
<t>This document presents necessary extensions to the currently deployed
ISIS for IP <xref format="default" pageno="false" target="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.</t>
</section>
<section title="Terminology" toc="default">
<t>Some of the terminology specified in <xref format="default"
pageno="false" target="I-D.draft-ietf-bier-architecture-03"/> is
replicated here and extended by necessary definitions:</t>
<t><list style="hanging">
<t hangText="BIER:">Bit Index Explicit Replication (The overall
architecture of forwarding multicast using a Bit Position).</t>
<t hangText="BIER-OL:">BIER Overlay Signaling. (The method for the
BFIR to learn about BFER's).</t>
<t hangText="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.</t>
<t hangText="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.</t>
<t hangText="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.</t>
<t hangText="BFT:">Bit Forwarding Tree used to reach all BFERs in a
domain.</t>
<t hangText="BIFT:">Bit Index Forwarding Table.</t>
<t hangText="BMS:">Bit Mask Set. Set containing bit positions of all
BFER participating in a set.</t>
<t hangText="BMP:">Bit Mask Position, a given bit in a BMS.</t>
<t hangText="Invalid BMP:">Unassigned Bit Mask Position, consisting
of all 0s.</t>
<t hangText="IGP signalled BIER domain:">A BIER underlay where the
BIER synchronization information is carried in IGP. Observe that a
multi-topology is NOT a separate BIER domain in IGP.</t>
<t hangText="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.</t>
<t hangText="BFR-id:">An optional, unique identifier for a BFR
within a BIER sub-domain.</t>
<t hangText="Invalid BFR-id:">Unassigned BFR-id, consisting of all
0s.</t>
<!--
-->
</list></t>
</section>
<section anchor="IANA" title="IANA Considerations" toc="default">
<t>This document adds the following new sub-TLV to the registry of sub-
TLVs for TLVs 235, 237 <xref format="default" pageno="false"
target="RFC5120"/> and TLVs 135,236 <xref format="default"
pageno="false" target="RFC5305"/>,<xref format="default" pageno="false"
target="RFC5308"/>.</t>
<t>Value: 32 (suggested - to be assigned by IANA)</t>
<t>Name: BIER Info</t>
<t>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 [RFC5226]. 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:</t>
<t><figure>
<artwork><![CDATA[
Type Name
---- ----
1 BIER MPLS Encapsulation
2 BIER sub-domain Tree Type
3 BIER sub-domain BSL conversion
]]></artwork>
</figure></t>
</section>
<section title="Concepts">
<section title="BIER Domains and Sub-Domains">
<t>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.</t>
<t>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 <xref format="default"
pageno="false" target="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.</t>
<t>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.</t>
</section>
<section title="Advertising BIER Information">
<t>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:</t>
<t><list style="symbols">
<t>Prefix length MUST be 32 for an IPv4 prefix or 128 for an IPv6
prefix</t>
<t>When the Prefix Attributes Flags sub-TLV <xref format="default"
pageno="false" target="RFC7794">is present N flag MUST be set and
X and R flags MUST NOT be set.</xref></t>
</list></t>
<t><list style="symbols">
<t>BIER sub-TLVs MUST NOT be included when a prefix reachability
advertisement is leaked between levels.</t>
</list></t>
</section>
</section>
<section title="Procedures">
<!--
-->
<section title="Enabling a BIER Sub-Domain">
<t><!--
--> A given sub-domain with identifier SD with supported bitstring lengths MLs
in a multi-topology MT <xref format="default" pageno="false"
target="RFC5120"/> is denoted further as <MT,SD,MLs> and does
not have to be advertised by default by BFRs to preserve the scaling
of the protocol (i.e. ISIS carries no TLVs containing any of the
elements related to <MT,SD>). The advertisement may be triggered
e.g. by a first BIER sub-TLV (<xref target="S2L"> </xref>) containing
<MT,SD> advertised into the area. The specific trigger itself is
outside the scope of this RFC but can be for example a VPN desiring to
initiate a BIER sub-domain as MI-PMSI <xref format="default"
pageno="false" target="RFC6513"/> tree or a pre-configured BFER (since
BFERs will always advertise the BIER sub-TLV to make sure they can be
reached). It is outside the scope of this document to describe what
trigger for a router capable of participating in <MT,SD> is used
to start the origination of the necessary information to join into
it.</t>
</section>
<section anchor="MTOPSUB" title="Multi Topology and Sub-Domain">
<t>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.</t>
</section>
<section title="Encapsulation">
<t>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.</t>
</section>
<section title="Tree Type">
<t>All routers in the flooding scope of the BIER TLVs MAY advertise a
supported tree type for a given <MT<!--,S-->,SD>. Tree type
indicates the algorithm used when calculating the optimal path.
Currently only the default algorithm "SPF" is defined - which has a
tree type of 0. If no tree type is advertised tree type 0 is assumed.
The supported tree type MUST be consistent for all routers supporting
a given <MT,SD>.</t>
</section>
<!--
-->
<section title="Label advertisements for MPLS Encapsulation">
<t>A router that desires to participate in <MT<!--,S-->,SD> MUST
advertise for each bitstring length it supports in <MT<!--,S-->,SD>
a label range size that guarantees to cover the maximum BFR-id
injected into <MT<!--,S-->,SD> (which implies a certain maximum
set id per bitstring length as described in <xref format="default"
pageno="false" target="I-D.draft-ietf-bier-architecture-03"/>). Any
router that violates this condition MUST be excluded from BIER BFTs
for <MT<!--,S-->,SD>.</t>
</section>
<section title="BFR-id Advertisements">
<t>Each BFER/BFIR MAY advertise with its TLV<MT<!--,S-->,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>.</t>
</section>
<section title="Reporting Misconfiguration">
<t>Whenever an advertisement is received which violates any of the
constraints defined in this document the receiving router MUST report
the misconfiguration.</t>
</section>
<section title="Flooding Reduction">
<t>BIER domain <!-- and service --> information SHOULD change
infrequently. Frequent changes will increase the number of Link State
PDU (LSP) updates and negatively impact performance in the
network.</t>
</section>
<!--
-->
</section>
<!--
-->
<section title="Packet Formats" toc="default">
<t>All ISIS BIER information is carried within the TLVs 235, 237 <xref
format="default" pageno="false" target="RFC5120"/> or TLVs 135 <xref
format="default" pageno="false" target="RFC5305"/>, <xref
format="default" pageno="false" target="RFC5308">or TLV 236</xref>.</t>
<section anchor="S2L" title="BIER Info sub-TLV">
<t>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.</t>
<t>The sub-TLV advertises a single <MT,SD> combination followed
by optional sub-sub-TLVs as described in the following sections.</t>
<figure align="left" alt="" height="" suppress-title="false" title=""
width="">
<artwork align="left" alt="" height="" name="" type="" width=""
xml:space="preserve"><![CDATA[
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | subdomain-id | BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t><list style="hanging">
<t hangText="Type:">as indicated in IANA section.</t>
<t hangText="Length:">1 octet.</t>
<!---->
<!---->
<t hangText="Reserved:">MUST be 0 on transmission, ignored on
reception. May be used in future versions. 8 bits</t>
<t hangText="subdomain-id:">Unique value identifying the BIER
sub-domain. 1 octet</t>
<t hangText="BFR-id:">A 2 octet field encoding the BFR-id, as
documented in <xref format="default" pageno="false"
target="I-D.draft-ietf-bier-architecture-03"/>. If no BFR-id has
been assigned this field is set to the invalid BFR-id.</t>
</list></t>
</section>
<section anchor="MS2L" title="BIER MPLS Encapsulation sub-sub-TLV">
<t>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<!--,S-->,SD>. It is advertised within
the BIER Info sub-TLV (<xref target="S2L"> </xref>) . This sub-sub-TLV
MAY appear multiple times within a single BIER info sub-TLV.</t>
<t>On violation of any of the following conditions, the receiving
router MUST ignore the encapsulating BIER Info sub-TLV.<list
style="symbols">
<t>Label ranges in multiple sub-sub-TLV MUST NOT overlap.</t>
<t>Bitstring lengths in multiple sub-sub-TLVs MUST NOT be
identical.</t>
<t>The sub-sub-TLV MUST include the required bitstring lengths
encoded in precisely the same way as in <xref format="default"
pageno="false"
target="I-D.draft-ietf-bier-mpls-encapsulation-03"/>.</t>
<t>The label range size MUST be greater than 0.</t>
<t>All labels in the range MUST represent valid label values</t>
</list></t>
<figure align="left" alt="" height="" suppress-title="false" title=""
width="">
<artwork align="left" alt="" height="" name="" type="" width=""
xml:space="preserve"><![CDATA[
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t><list style="hanging">
<t hangText="Type:">value of 1 indicating MPLS encapsulation.</t>
<t hangText="Length:">1 octet.</t>
<t hangText="Local BitString Length (BS Len):">Encoded bitstring
length as per <xref format="default" pageno="false"
target="I-D.draft-ietf-bier-mpls-encapsulation-03"/>. 4 bits.</t>
<t hangText="Label Range Size:">Number of labels in the range used
on encapsulation for this BIER sub-domain for this bitstring
length, 1 octet.</t>
<t hangText="Label:">First label of the range, 20 bits. The labels
are as defined in <xref format="default" pageno="false"
target="I-D.draft-ietf-bier-mpls-encapsulation-03"/>.</t>
</list></t>
</section>
<section anchor="MS2T"
title="Optional BIER sub-domain Tree Type sub-sub-TLV">
<t>This sub-sub-TLV carries the information associated with the
supported BIER tree type for a <MT<!--,S-->,SD> combination. It
is carried within the BIER Info sub-TLV (<xref target="S2L"> </xref>)
that the router participates in as BFR. This sub-sub-TLV is optional
and its absence has the same semantics as its presence with Tree Type
value 0 (SPF). When Tree Type 0 is used it is recommended that this
sub-sub-TLV be omitted in order to reduce the space consumed in the
parent TLV.</t>
<t>This sub-sub-TLV MUST NOT occur more than once in a BIER Info
sub-TLV. If multiple occurences of this sub-sub-TLV are present in a
single BIER Info sub-TLV the encapsulating BIER Info sub-TLV MUST be
ignored.</t>
<t>If the tree type (implied or explicitly advertised) does not match
the locally configured tree type associated with the matching <MT,
SD> pair the encapsulating sub-TLV MUST be ignored.</t>
<figure align="left" alt="" height="" suppress-title="false" title=""
width="">
<artwork align="left" alt="" height="" name="" type="" width=""
xml:space="preserve"><![CDATA[
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree Type |
+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t><list style="hanging">
<t hangText="Type:">value of 1 indicating BIER Tree Type.</t>
<t hangText="Length:">1 octet.</t>
<t hangText="Tree Type:">1 octet</t>
</list></t>
</section>
<section anchor="MS2C"
title="Optional BIER sub-domain BSL conversion sub-sub-TLV">
<t>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<!--,S-->,SD> or prevent stable blackholes in
scenarios where not all routers support the same set of BSLs in a
given <MT<!--,S-->,SD>. It is carried within the BIER Info
sub-TLV (<xref target="S2L"> </xref>). 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.</t>
<figure align="left" alt="" height="" suppress-title="false" title=""
width="">
<artwork align="left" alt="" height="" name="" type="" width=""
xml:space="preserve"><![CDATA[
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t/>
</section>
</section>
<section anchor="Security" title="Security Considerations" toc="default">
<t>Implementations must assure that malformed TLV and Sub-TLV
permutations do not result in errors which cause hard protocol
failures.</t>
</section>
<section anchor="Acknowledgements" title="Acknowledgements" toc="default">
<t>The RFC is aligned with the <xref format="default" pageno="false"
target="I-D.draft-ietf-bier-ospf-bier-extensions-01"/> draft as far as
the protocol mechanisms overlap.</t>
<t>Many thanks for comments from (in no particular order) Hannes
Gredler, Ijsbrand Wijnands, Peter Psenak and Chris Bowers.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.1195"?>
<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.5120"?>
<?rfc include="reference.RFC.5226"?>
<?rfc include="reference.RFC.6513"?>
<?rfc include="reference.RFC.5305"?>
<?rfc include="reference.RFC.5308"?>
<?rfc include="reference.RFC.7794"?>
<reference anchor="I-D.draft-ietf-bier-architecture-03">
<front>
<title>Stateless Multicast using Bit Index Explicit Replication
Architecture</title>
<author initials="IJ" surname="Wijnands et al.">
<organization/>
</author>
<date month="Jan" year="2016"/>
</front>
<seriesInfo name="internet-draft"
value="draft-ietf-bier-architecture-03.txt"/>
<format target="http://tools.ietf.org/id/draft-ietf-bier-architecture-02.txt"
type="TXT"/>
</reference>
<reference anchor="I-D.draft-ietf-bier-mpls-encapsulation-03">
<front>
<title>Bit Index Explicit Replication using MPLS
encapsulation</title>
<author initials="IJ" surname="Wijnands et al.">
<organization/>
</author>
<date month="Feb" year="2016"/>
</front>
<seriesInfo name="internet-draft"
value="draft-ietf-bier-mpls-encapsulation-03.txt"/>
<format target="http://tools.ietf.org/id/draft-ietf-bier-mpls-encapsulation-03.txt"
type="TXT"/>
</reference>
<reference anchor="I-D.draft-ietf-bier-ospf-bier-extensions-01">
<front>
<title>OSPF Extension for Bit Index Explicit Replication</title>
<author initials="P" surname="Psenak et al.">
<organization/>
</author>
<date month="October" year="2015"/>
</front>
<seriesInfo name="internet-draft"
value="draft-ietf-bier-ospf-bier-extensions-01.txt"/>
<format target="http://tools.ietf.org/id/draft-ietf-bier-ospf-bier-extensions-01.txt"
type="TXT"/>
</reference>
</references>
</back>
</rfc>
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