One document matched: draft-psenak-ospf-segment-routing-extensions-01.xml
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<?rfc tocdepth="3"?>
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<rfc category="std" docName="draft-psenak-ospf-segment-routing-extensions-01"
ipr="trust200902">
<front>
<title abbrev="OSPF Extensions for Segment Routing">OSPF Extensions for
Segment Routing</title>
<author fullname="Peter Psenak" initials="P." role="editor"
surname="Psenak">
<organization>Cisco Systems, Inc.</organization>
<address>
<postal>
<street>Apollo Business Center</street>
<street>Mlynske nivy 43</street>
<city>Bratislava</city>
<code>821 09</code>
<country>Slovakia</country>
</postal>
<email>ppsenak@cisco.com</email>
</address>
</author>
<author fullname="Stefano Previdi" initials="S." role="editor"
surname="Previdi">
<organization>Cisco Systems, Inc.</organization>
<address>
<postal>
<street>Via Del Serafico, 200</street>
<city>Rome</city>
<code>00142</code>
<country>Italy</country>
</postal>
<email>sprevidi@cisco.com</email>
</address>
</author>
<author fullname="Clarence Filsfils" initials="C." surname="Filsfils">
<organization>Cisco Systems, Inc.</organization>
<address>
<postal>
<street/>
<city>Brussels</city>
<region/>
<code/>
<country>Belgium</country>
</postal>
<email>cfilsfil@cisco.com</email>
</address>
</author>
<author fullname="Hannes Gredler" initials="H." surname="Gredler">
<organization>Juniper Networks, Inc.</organization>
<address>
<postal>
<street>1194 N. Mathilda Ave.</street>
<city>Sunnyvale</city>
<code>94089</code>
<region>CA</region>
<country>US</country>
</postal>
<email>hannes@juniper.net</email>
</address>
</author>
<author fullname="Rob Shakir" initials="R." surname="Shakir">
<organization>British Telecom</organization>
<address>
<postal>
<street/>
<city>London</city>
<code/>
<country>UK</country>
</postal>
<email>rob.shakir@bt.com</email>
</address>
</author>
<date day="1" month="July" year="2013"/>
<area>Routing</area>
<workgroup>Open Shortest Path First IGP</workgroup>
<keyword>MPLS</keyword>
<keyword>SID</keyword>
<keyword>IGP</keyword>
<keyword>OSPF</keyword>
<keyword>Label advertisement</keyword>
<keyword>Segment Routing</keyword>
<abstract>
<t>Segment Routing (SR) allows for a flexible definition of end-to-end
paths within IGP topologies by encoding paths as sequences of
topological sub-paths, called "segments". These segments are advertised
by the link-state routing protocols (IS-IS and OSPF).</t>
<t>This draft describes the necessary OSPF extensions that need to be
introduced for Segment Routing.</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
target="RFC2119">RFC 2119</xref>.</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>Segment Routing (SR) allows for a flexible definition of end-to-end
paths within IGP topologies by encoding paths as sequences of
topological sub-paths, called "segments". These segments are advertised
by the link-state routing protocols (IS-IS and OSPF). Prefix segments
represent an ecmp-aware shortest-path to a prefix (or a node), as per
the state of the IGP topology. Adjacency segments represent a hop over a
specific adjacency between two nodes in the IGP. A prefix segment is
typically a multi-hop path while an adjacency segment, in most of the
cases, is a one-hop path. SR's control-plane can be applied to both IPv6
and MPLS data-planes, and do not require any additional signaling (other
than the regular IGP). For example, when used in MPLS networks, SR paths
do not require any LDP or RSVP-TE signaling. Still, SR can interoperate
in the presence of LSPs established with RSVP or LDP .</t>
<t>This draft describes the necessary OSPF extensions that need to be
introduced for Segment Routing.</t>
<t>Segment Routing architecture is described in <xref
target="I-D.filsfils-rtgwg-segment-routing"/>.</t>
<t>Segment Routing use cases are described in <xref
target="I-D.filsfils-rtgwg-segment-routing-use-cases"/>.</t>
</section>
<section title="Segment Routing Identifiers">
<t>Segment Routing defines various types of Segment Identifiers (SIDs):
Prefix-SID, Adjacency-SID, LAN Adjacency SID and Binding SID.</t>
<t>For the purpose of the advertisements of various SID values new
Opaque LSAs (defined in <xref target="RFC5250"/>) are defined. These new
LSAs are defined as generic containers that can be used in order to
advertise any additional attributes associated with the prefix or link.
These new Opaque LSAs are complementary to the existing LSAs and are not
aimed to replace any of the existing LSAs.</t>
<section anchor="SIDLABEL" title="SID/Label TLV">
<t>SID/Label TLV appears as Sub-TLV in multiple TLVs or Sub-TLVs
defined later in this document. It is used to advertise SID or label
associated with the prefix or adjacency. SID/Lable TLV has following
format:<figure>
<artwork> 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID/Label (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
</artwork>
</figure><list style="hanging">
<t>Type: TBA</t>
<t>Length: variable, 3 or 4 bytes</t>
<t>SID/Label: if length is set to 3, then the 20 rightmost bits
represent a label. If length is set to 4 then the value represents
a 32 bit SID.</t>
<t/>
<t/>
</list></t>
</section>
</section>
<section anchor="SRCAP" title="Segment Routing Capabilities">
<t>Segment Routing requires some additional capabilities of the router
to be advertised to other routers in the area.</t>
<t>These SR capabilities are advertised in Router Information Opaque LSA
(defined in <xref target="RFC4970"/>).</t>
<section anchor="SRALGO" title="SR-Algorithm TLV">
<t>SR-Algorithm TLV is a TLV of Router Information Opaque LSA (defined
in <xref target="RFC4970"/>).</t>
<t>Router may use various algorithms when calculating reachability to
other nodes in area or to prefixes attached to these nodes. Examples
of these algorithms are metric based Shortest Path First (SPF),
various sorts of Constrained SPF, etc. SR-Algorithm TLV allows a
router to advertise algorithms that router is currently using to other
routers in an area. SR-Algorithm TLV has following structure: <figure>
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm 1 | Algorithm... | Algorithm n | |
+- -+
| |
+ +
where:</artwork>
</figure><list style="hanging">
<t>Type: TBA</t>
<t>Length: variable</t>
<t>Algorithm: one octet identifying the algorithm. The following
value has been defined:<list style="hanging">
<t>0: IGP metric based SPT.</t>
</list></t>
</list></t>
<t>RI LSA can be advertised at any of the defined flooding scopes
(link, area, or autonomous system (AS)). For the purpose of the
SR-Algorithm TLV propagation area scope flooding is required.</t>
</section>
<section anchor="SIDRANGE" title="SID/Label Range TLV">
<t>The SID/Label Range TLV is a TLV of Router Information Opaque LSA
(defined in <xref target="RFC4970"/>).</t>
<t>SID/Label Sub-TLV MAY appear multiple times and has following
format:<figure>
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Range Size | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
+ +
where:</artwork>
</figure><list style="hanging">
<t>Type: TBA</t>
<t>Length: variable</t>
<t>Range Size: size of the SID/label range</t>
</list></t>
<t>Currently the only supported Sub-TLV is the SID/Label TLV as
defined in <xref target="SIDLABEL"/>. SID/Label advertised in
SID/Label TLV represents the first SID/Label from the advertised
range.</t>
<t>RI LSA can be advertised at any of the defined flooding scopes
(link, area, or autonomous system (AS)). For the purpose of the
SR-Capability TLV propagation area scope flooding is required.</t>
</section>
</section>
<section anchor="EXTPXLSA" title="OSPFv2 Extended Prefix Opaque LSA type ">
<t>A new Opaque LSA (defined in <xref target="RFC5250"/>) is defined in
OSPFv2 in order to advertise additional prefix attributes: OSPFv2
Extended Prefix Opaque LSA.</t>
<t>Multiple OSPFv2 Extended Prefix Opaque LSAs can be advertised by a
single router. Flooding scope of the OSPFv2 Extended Prefix Opaque LSA
depends on the content inside the LSA and is in control of the
originating router.</t>
<t>The format of the OSPFv2 Extended Prefix Opaque LSA is as follows:
<figure>
<artwork>
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 9, 10, or 11 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque type | Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- TLVs -+
| ... |</artwork>
</figure></t>
<t>Opaque type used by OSPFv2 Extended Prefix Opaque LSA is TBA.</t>
<t>The format of the TLVs within the body of the LSA is the same as the
format used by the Traffic Engineering Extensions to OSPF defined in
<xref target="RFC3630"/>. The LSA payload consists of one or more nested
Type/Length/Value (TLV) triplets. The format of each TLV is:</t>
<figure>
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</artwork>
</figure>
<t>The Length field defines the length of the value portion in octets.
The TLV is padded to 4-octet alignment; padding is not included in the
length field. Nested TLVs are also 32-bit aligned. Unrecognized types
are ignored.</t>
<section title="OSPF Extended Prefix TLV">
<t>The OSPF Extended Prefix TLV is used in order to advertise
additional attributes associated with the prefix. Multiple OSPF
Extended Prefix TLVs MAY be carried in each OSPFv2 Extended Prefix
Opaque LSA, however all prefixes included in the single OSPFv2
Extended Prefix Opaque LSA MUST have the same flooding scope. The
structure of the OSPF Extended Prefix TLV is as follows: <figure>
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Route Type | Prefix Length | AF | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Prefix (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
where: </artwork>
</figure><list style="hanging">
<t>Type is TBA.</t>
<t>Length is variable</t>
<t>Route type: type of the OSPF route. Supported types are:<figure>
<artwork>
0 - unspecified
1 - intra-area
3 - inter-area
5 - external
7 - NSSA external</artwork>
</figure>If the route type is 0 (unspecified) the information
inside the OSPF External Prefix TLV applies to the prefix
regardless of what route-type it is. This is useful when some
prefix specific attributes are advertised by some external entity,
which is not aware of the route-type associated with the
prefix.</t>
<t>Prefix length: length of the prefix</t>
<t>AF: 0 - IPv4 unicast</t>
<t>Address Prefix: the prefix itself encoded as an even multiple
of 32-bit words, padded with zeroed bits as necessary. This
encoding consumes ((PrefixLength + 31) / 32) 32-bit words. The
default route is represented by a prefix of length 0.</t>
</list></t>
</section>
<section anchor="PREFIXSID" title="Prefix SID Sub-TLV">
<t>The Prefix SID Sub-TLV is a Sub-TLV of the OSPF Extended Prefix
TLV. It MAY appear more than once and has following format: <figure>
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | MT-ID | Algorithm | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:</artwork>
</figure><list style="hanging">
<t>Type: TBA.</t>
<t>Length: A 16-bit field that indicates the length of the value
portion in octets. Set to 8.</t>
<t>Flags: 1 octet field. The following flags are defined: <figure
align="center">
<artwork>
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|N|P|M| |
+-+-+-+-+-+-+-+-+
where:</artwork>
</figure><list style="hanging">
<t>N-Flag: Node-SID flag. If set, then the Prefix-SID refers
to the router identified by the prefix. Typically, the N-Flag
is set on Prefix-SIDs attached to a router loopback address.
The N-Flag is set when the Prefix-SID is a Node- SID as
described in <xref
target="I-D.filsfils-rtgwg-segment-routing"/>.</t>
<t>P-Flag: no-PHP flag. If set, then the penultimate hop MUST
NOT pop the Prefix-SID before delivering the packet to the
node that advertised the Prefix-SID.</t>
<t>M-Flag: Mapping Server Flag. If set, the SID is advertised
from the Segment Routing Mapping Server functionality as
described in <xref
target="I-D.filsfils-rtgwg-segment-routing-use-cases"/>.</t>
<t>Other bits: MUST be zero when sent and ignored when
received.</t>
</list></t>
<t>MT-ID: Multi-Topology ID (as defined in <xref
target="RFC4915"/>).</t>
<t>Algorithm: one octet identifying the algorithm the Prefix-SID
is associated with as defined in <xref target="SRALGO"/>.</t>
<t>Index: 32 bits representing the offset to the advertised
SID/Label range.</t>
</list></t>
<t>If multiple Prefix-SIDs are advertised for the same prefix, the
receiving router MUST use the first encoded SID and MAY use the
subsequent ones.</t>
<t>PHP flag MUST NOT be set on the Prefix-SIDs allocated to inter-
area prefixes that are originated by the router based on intra-area or
inter-area reachability between areas.</t>
</section>
<section anchor="SIDBINDING" title="SID/Label Binding TLV">
<t>SID/Label Binding TLV is used to advertise SID/Label mapping for a
prefix or a path to the prefix. SID/Label value advertised in this TLV
has local significance (to the router).</t>
<t>SID/Label Binding TLV is a Sub-TLV of the OSPF Extended Prefix TLV.
Multiple SID/Label Binding TLVs can be present in OSPF Extended Prefix
TLV. SID/Label Binding TLV has following format: <figure>
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | MT-ID | Weight | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
where: </artwork>
</figure><list style="hanging">
<t>Type: TBA</t>
<t>Length: variable</t>
<t>Flags: 1 octet field of following flags:<figure align="center">
<artwork>
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|M| |
+-+-+-+-+-+-+-+-+
</artwork>
</figure>
where:
<list style="hanging">
<t>M-bit - When the bit is set the binding represents the
mirroring context as defined in
<xref target="I-D.minto-rsvp-lsp-egress-fast-protection"/>.</t>
</list></t>
<t>MT-ID: Multi-Topology ID (as defined in <xref
target="RFC4915"/>).</t>
<t>Weight: weight used for load-balancing purposes. The use of the
weight is defined in <xref
target="I-D.filsfils-rtgwg-segment-routing"/>.</t>
</list></t>
<t>SID/Label Binding TLV currently supports following Sub-TLVs:<list
style="hanging">
<t>SID/Lable TLV as described in <xref target="SIDLABEL"/>. This
TLV MUST appear in the SID/Label Binding Sub-TLV and it MUST only
appear once.</t>
<t>ERO TLVs as defined in <xref target="EROTLV"/>.</t>
</list></t>
<section anchor="EROTLV" title="ERO TLVs">
<t>All 'ERO' information represents an ordered set which describes
the segments of a path. The last ERO TLV describes the segment
closest to the egress point, contrary the first ERO TLV describes
the first segment of a path. If a router extends or stitches a path
it MUST prepend the new segments path information to the ERO
list.</t>
<t>The above similarly applies to backup EROs.</t>
<t>All ERO Sub-TLVs must immediately follow the (SID)/Label
Sub-TLV.</t>
<t>All Backup ERO TLVs must immediately follow last ERO Sub-TLV.</t>
<section anchor="IPV4ERO" title="IPv4 ERO TLV">
<t>IPv4 ERO TLV is a Sub-TLV of the SID/Lable Binding TLV.</t>
<t>The IPv4 ERO TLV describes a path segment using IPv4 Address
style of encoding. Its semantics have been borrowed from <xref
target="RFC3209"/>. <figure title="IPv4 ERO TLV format">
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork>
</figure> where: <list style="hanging">
<t>Type: TBA</t>
<t>Length: 8 bytes</t>
<t>Flags: 1 octet field of following flags: <figure
align="center">
<artwork>
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|L| |
+-+-+-+-+-+-+-+-+
</artwork>
</figure> where: <list style="hanging">
<t>L-bit - If the L bit is set, then the value of the
attribute is 'loose.' Otherwise, the value of the
attribute is 'strict.'</t>
</list></t>
<t>IPv4 Address - the address of the explicit route hop.</t>
</list></t>
</section>
<section anchor="UNNERO" title="Unnumbered Interface ID ERO TLV">
<t>Unnumbered Interface ID ERO TLV is a Sub-TLV of the SID/Lable
Binding TLV.</t>
<t>The appearance and semantics of the 'Unnumbered Interface ID'
have been borrowed from <xref target="RFC3477"/>.</t>
<t>The Unnumbered Interface-ID ERO TLV describes a path segment
that spans over an unnumbered interface. Unnumbered interfaces are
referenced using the interface index. Interface indices are
assigned local to the router and therefore not unique within a
domain. All elements in an ERO path need to be unique within a
domain and hence need to be disambiguated using a domain unique
Router-ID. <figure title="Unnumbered Interface ID ERO TLV format">
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:</artwork>
</figure><list style="hanging">
<t>Type: TBA</t>
<t>Length: 12 bytes</t>
<t>Flags: 1 octet field of following flags:<figure
align="center">
<artwork>
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|L| |
+-+-+-+-+-+-+-+-+
where: </artwork>
</figure><list style="hanging">
<t>L-bit - If the L bit is set, then the value of the
attribute is 'loose.' Otherwise, the value of the
attribute is 'strict.'</t>
</list></t>
<t>Router-ID: Router-ID of the next-hop.</t>
<t>Interface ID: is the identifier assigned to the link by the
router specified by the Router-ID.</t>
</list></t>
</section>
<section anchor="IPV4BERO" title="IPv4 Backup ERO TLV">
<t>IPv4 Prefix Backup ERO TLV is a Sub-TLV of the SID/Lable
Binding TLV.</t>
<t>The IPv4 Backup ERO TLV describes a path segment using IPv4
Address style of encoding. Its semantics have been borrowed from
<xref target="RFC3209"/>. <figure
title="IPv4 Backup ERO TLV format">
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Address (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork>
</figure> where: <list style="hanging">
<t>Type: TBA</t>
<t>Length: 8 bytes</t>
<t>Flags: 1 octet field of following flags: <figure
align="center">
<artwork>
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|L| |
+-+-+-+-+-+-+-+-+
</artwork>
</figure> where: <list style="hanging">
<t>L-bit - If the L bit is set, then the value of the
attribute is 'loose.' Otherwise, the value of the
attribute is 'strict.'</t>
</list></t>
<t>IPv4 Address - the address of the explicit route hop.</t>
</list></t>
</section>
<section anchor="UNNBERO"
title="Unnumbered Interface ID Backup ERO TLV">
<t>Unnumbered Interface ID Backup TLV is a Sub-TLV of the
SID/Lable Binding TLV.</t>
<t>The appearance and semantics of the 'Unnumbered Interface ID'
have been borrowed from <xref target="RFC3477"/>.</t>
<t>The Unnumbered Interface-ID ERO TLV describes a path segment
that spans over an unnumbered interface. Unnumbered interfaces are
referenced using the interface index. Interface indices are
assigned local to the router and therefore not unique within a
domain. All elements in an ERO path need to be unique within a
domain and hence need to be disambiguated using a domain unique
Router-ID. <figure
title="Unnumbered Interface ID Backup ERO TLV format">
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork>
</figure> where: <list style="hanging">
<t>Type: TBA</t>
<t>Length: 12 bytes</t>
<t>Flags: 1 octet field of following flags: <figure
align="center">
<artwork>
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|L| |
+-+-+-+-+-+-+-+-+
</artwork>
</figure> where: <list style="hanging">
<t>L-bit - If the L bit is set, then the value of the
attribute is 'loose.' Otherwise, the value of the
attribute is 'strict.'</t>
</list></t>
<t>Router-ID: Router-ID of the next-hop.</t>
<t>Interface ID: is the identifier assigned to the link by the
router specified by the Router-ID.</t>
</list></t>
</section>
</section>
</section>
</section>
<section anchor="ADJSID" title="Adjacency Segment Identifier (Adj-SID)">
<t>An Adjacency Segment Identifier (Adj-SID) represents a router
adjacency in Segment Routing. At the current stage of Segment Routing
architecture it is assumed that the Adj-SID value has local significance
(to the router).</t>
<section title="OSPFv2 Extended Link Opaque LSA ">
<t>A new Opaque LSA (defined in <xref target="RFC5250"/> is defined in
OSPFv2 in order to advertise additional link attributes: the OSPFv2
Extended Link Opaque LSA.</t>
<t>The OSPFv2 Extended Link Opaque LSA has an area flooding scope.
Multiple OSPFv2 Extended Link Opaque LSAs can be advertised by a
single router in an area.</t>
<t>The format of the OSPFv2 Extended Link Opaque LSA is as follows:
<figure>
<artwork>
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS age | Options | 10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque type | Instance |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS checksum | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- TLVs -+
| ... |</artwork>
</figure></t>
<t>Opaque type used by OSPFv2 Extended Link Opaque LSA is TBA</t>
<t>The format of the TLVs within the body of LSA is the same as the
format used by the Traffic Engineering Extensions to OSPF defined in
<xref target="RFC3630"/>. The LSA payload consists of one or more
nested Type/Length/Value (TLV) triplets. The format of each TLV
is:</t>
<figure>
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+</artwork>
</figure>
<t>The Length field defines the length of the value portion in octets.
The TLV is padded to 4-octet alignment; padding is not included in the
length field. Nested TLVs are also 32-bit aligned. Unrecognized types
are ignored.</t>
</section>
<section title="OSPFv2 Extended Link TLV">
<t>OSPFv2 Extended Link TLV is used in order to advertise various
attributes of the link. It describes a single link and is constructed
of a set of Sub-TLVs. There are no ordering requirements for the
Sub-TLVs. Only one Extended Link TLV SHALL be carried in each Extended
Link Opaque LSA, allowing for fine granularity changes in the
topology.</t>
<t>The Extended Link TLV has following format:<figure>
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link-Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
where:</artwork>
</figure><list>
<t>Type is TBA.</t>
<t>Length is variable.</t>
<t>Link-Type: as defined in section A.4.2 of <xref
target="RFC2328"/>.</t>
<t>Link-ID: as defined in section A.4.2 of <xref
target="RFC2328"/>.</t>
<t>Link Data: as defined in section A.4.2 of <xref
target="RFC2328"/>.</t>
</list></t>
</section>
<section anchor="ADJSIDSUBTLV" title="Adj-SID sub-TLV">
<t>Adj-SID is an optional Sub-TLV of the Extended Link TLV. It MAY
appear multiple times in Extended Link TLV. Examples where more than
one Adj-SID may be used per neighbor are described in <xref
target="I-D.filsfils-rtgwg-segment-routing-use-cases"/>. The
structure of the Adj-SID Sub-TLV is as follows: <figure>
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | MT-ID | Weight | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
where:</artwork>
</figure><list style="hanging">
<t>Type: TBA.</t>
<t>Length: variable.</t>
<t>Flags. 1 octet field of following flags:<figure align="center">
<artwork>
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|B| |
+-+-+-+-+-+-+-+-+
where:</artwork>
</figure><list style="hanging">
<t>B-Flag: Backup-flag: set if the Adj-SID refer to an
adjacency being protected (e.g.: using IPFRR or MPLS-FRR) as
described in <xref
target="I-D.filsfils-rtgwg-segment-routing-use-cases"/>.</t>
<t>Other bits: MUST be zero when originated and ignored when
received.</t>
</list></t>
<t>MT-ID: Multi-Topology ID (as defined in <xref
target="RFC4915"/>.</t>
<t>Weight: weight used for load-balancing purposes. The use of the
weight is defined in <xref
target="I-D.filsfils-rtgwg-segment-routing"/>.</t>
<t>Adj-SID Sub-TLV supports following Sub-TLVs:<list
style="hanging">
<t>SID/Label TLV as described in <xref target="SIDLABEL"/>.
This TLV MUST appear in the Adj-SID Sub-TLV and it MUST only
appear once.</t>
</list></t>
</list></t>
<t>A SR capable router MAY allocate an Adj-SID for each of its
adjacencies and set the B-Flag when the adjacency is protected by a
FRR mechanism (IP or MPLS) as described in <xref
target="I-D.filsfils-rtgwg-segment-routing-use-cases"/>.</t>
</section>
<section anchor="LANADJSIDSUBTLV" title="LAN Adj-SID/Label Sub-TLV">
<t>LAN Adj-SID is an optional Sub-TLV of the Extended Link TLV. It MAY
appear multiple times in Extended Link TLV. It is used to advertise
SID/Label for adjacency to non-DR node on broadcast or NBMA network.
<figure>
<artwork>
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | MT-ID | Weight | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
where:</artwork>
</figure><list style="hanging">
<t>Type: TBA.</t>
<t>Length: variable.</t>
<t>Flags. 1 octet field of following flags:<figure align="center">
<artwork>
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|B| |
+-+-+-+-+-+-+-+-+
where:</artwork>
</figure><list style="hanging">
<t>B-Flag: Backup-flag: set if the LAN-Adj-SID refer to an
adjacency being protected (e.g.: using IPFRR or MPLS-FRR) as
described in <xref
target="I-D.filsfils-rtgwg-segment-routing-use-cases"/>.</t>
<t>Other bits: MUST be zero when originated and ignored when
received.</t>
</list></t>
<t>MT-ID: Multi-Topology ID (as defined in <xref
target="RFC4915"/>.</t>
<t>Weight: weight used for load-balancing purposes. The use of the
weight is defined in <xref
target="I-D.filsfils-rtgwg-segment-routing"/>.</t>
<t>LAN Adj-SID Sub-TLV supports following Sub-TLVs:<list
style="hanging">
<t>SID/Label TLV as described in <xref target="SIDLABEL"/>.
This TLV MUST appear in the Adj-SID Sub-TLV and it MUST only
appear once.</t>
</list></t>
</list></t>
</section>
</section>
<section title="Elements of Procedure">
<section title="Intra-area Segment routing in OSPFv2 ">
<t>The OSPFv2 node that supports segment routing MAY advertise Prefix-
SIDs for any prefix that it is advertising reachability for (e.g.
loopback IP address) as described in <xref target="PREFIXSID"/>.</t>
<t>If multiple routers advertise Prefix-SID for the same prefix, then
the Prefix-SID MUST be the same. This is required in order to allow
traffic load-balancing if multiple equal cost paths to the destination
exist in the network.</t>
<t>Prefix-SID can also be advertised by the SR Mapping Servers (as
described in <xref
target="I-D.filsfils-rtgwg-segment-routing-use-cases"/>). The
Mapping Server advertise Prefix-SID for remote prefixes that exist in
the network. Multiple Mapping Servers can advertise Prefix-SID for the
same prefix, in which case the same Prefix-SID MUST be advertised by
all of them. Flooding scope of the OSPF Extended Prefix Opaque LSA
that is generated by the SR Mapping Server could be either area scope
or autonomous system scope and is decided based on the configuration
of the SR Mapping Server.</t>
</section>
<section title="Inter-area Segment routing in OSPFv2">
<t>In order to support SR in a multi-area environment, OSPFv2 must
propagate Prefix-SID information between areas. The following
procedure is used in order to propagate Prefix SIDs between areas.</t>
<t>When an OSPF ABR advertises a Type-3 Summary LSA from an intra-area
prefix to all its connected areas, it will also originate an Extended
Prefix Opaque LSA, as described in <xref target="EXTPXLSA"/>. The
flooding scope of the Extended Prefix Opaque LSA type will be set to
area-scope. The route-type in OSPF Extended Prefix TLV is set to
inter-area. The Prefix-SID Sub-TLV will be included in this LSA and
the Prefix-SID value will be set as follows: <list style="hanging">
<t>The ABR will look at its best path to the prefix in the source
area and find out the advertising router associated with its best
path to that prefix.</t>
<t>If no Prefix-SID was advertised for the prefix in the source
area by the router that contributes to the best path to the
prefix, then the ABR will use the Prefix-SID advertised by any
other router (e.g.: a Prefix-SID coming from an SR Mapping Server
as defined in <xref
target="I-D.filsfils-rtgwg-segment-routing-use-cases"/>) when
propagating Prefix-SID for the prefix to other areas.</t>
</list></t>
<t>When an OSPF ABR advertises Type-3 Summary LSAs from an inter-area
route to all its connected areas it will also originate an Extended
Prefix Opaque LSA, as described in <xref target="EXTPXLSA"/>. The
flooding scope of the Extended Prefix Opaque LSA type will be set to
area-scope. The route-type in OSPF Extended Prefix TLV is set to
inter-area. The Prefix-SID Sub-TLV will be included in this LSA and
the Prefix-SID will be set as follows: <list style="hanging">
<t>The ABR will look at its best path to the prefix in the source
area and find out the advertising router associated with its best
path to that prefix.</t>
<t>The ABR will then look if such router advertised a Prefix-SID
for the prefix and use it when advertising the Prefix-SID to other
connected areas.</t>
<t>If no Prefix-SID was advertised for the prefix in the source
area by the ABR that contributes to the best path to the prefix,
the originating ABR will use the Prefix-SID advertised by any
other router (e.g.: a Prefix-SID coming from an SR Mapping Server
as defined in <xref
target="I-D.filsfils-rtgwg-segment-routing-use-cases"/>) when
propagating Prefix-SID for the prefix to other areas.</t>
</list></t>
</section>
<section title="SID for External Prefixes">
<t>Type-5 LSAs are flooded domain wide. When an ASBR, which supports
SR, generates Type-5 LSAs, it should also originate Extended Prefix
Opaque LSAs, as described in <xref target="EXTPXLSA"/>. The flooding
scope of the Extended Prefix Opaque LSA type is set to AS-scope. The
route-type in OSPF Extended Prefix TLV is set to external. Prefix-SID
Sub-TLV is included in this LSA and the Prefix-SID value will be set
to the SID that has been reserved for that prefix.</t>
<t>When a NSSA ASBR translates Type-7 LSAs into Type-5 LSAs, it should
also advertise the Prefix-SID for the prefix. The NSSA ABR determines
its best path to the prefix advertised in the translated Type-7 LSA
and finds the advertising router associated with such path. If such
advertising router has advertised a Prefix-SID for the prefix, then
the NSSA ASBR uses it when advertising the Prefix-SID for the Type-5
prefix. Otherwise the Prefix-SID advertised by any other router will
be used (e.g.: a Prefix-SID coming from an SR Mapping Server as
defined in <xref
target="I-D.filsfils-rtgwg-segment-routing-use-cases"/>).</t>
</section>
<section title="Advertisement of Adj-SID">
<t>The Adjacency Segment Routing Identifier (Adj-SID) is advertised
using the Adj-SID Sub-TLV as described in <xref target="ADJSID"/>.</t>
<section title="Advertisement of Adj-SID on Point-to-Point Links">
<t>Adj-SID MAY be advertised for any adjacency on p2p link that is
in a state 2-Way or higher. If the adjacency on a p2p link
transitions from the FULL state, then the Adj-SID for that adjacency
MAY be removed from the area. If the adjacency transitions to a
state lower then 2-Way, then the Adj-SID MUST be removed from the
area.</t>
</section>
<section title="Adjacency SID on Broadcast or NBMA Interfaces">
<t>Broadcast or NBMA networks in OSPF are represented by a star
topology where the Designated Router (DR) is the central point all
other routers on the broadcast or NBMA network connect to. As a
result, routers on the broadcast or NBMA network advertise only
their adjacency to DR and BDR. Routers that are neither DR nor BDR
do not form and do not advertise adjacencies between them. They,
however, maintain a 2-Way adjacency state between them.</t>
<t>When Segment Routing is used, each router on the broadcast or
NBMA network MAY advertise the Adj-SID for its adjacency to DR using
Adj-SID Sub-TLV as described in <xref target="ADJSIDSUBTLV"/>.</t>
<t>SR capable router MAY also advertise Adj-SID for other neighbors
(e.g. BDR, DR-OTHER) on broadcast or NBMA network using the LAN
ADJ-SID Sub-TLV as described in section 5.1.1.2. <xref
target="LANADJSIDSUBTLV"/>.</t>
</section>
</section>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>TBD</t>
</section>
<section anchor="Manageability" title="Manageability Considerations">
<t>TBD</t>
</section>
<section anchor="Security" title="Security Considerations">
<t>TBD</t>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>We would like to thank Anton Smirnov and Wim Hendricks.</t>
<t>Many thanks to Yakov Rekhter, John Drake and Shraddha Hedge for their contribution on earlier
incarnations of the "Binding / MPLS Label TLV" in
<xref target="I-D.gredler-ospf-label-advertisement"/>. </t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.3209.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.3477.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.3630.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.5250.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.2328.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.4970.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml/reference.RFC.4915.xml"?>
<?rfc ?>
</references>
<references title="Informative References">
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-filsfils-rtgwg-segment-routing-00.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-filsfils-rtgwg-segment-routing-use-cases-00.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-minto-rsvp-lsp-egress-fast-protection-02.xml"?>
<?rfc include="http://xml.resource.org/public/rfc/bibxml3/reference.I-D.draft-gredler-ospf-label-advertisement-03.xml"?>
</references>
</back>
</rfc>
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