One document matched: draft-xu-ospf-mpls-elc-01.xml
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<rfc category="std" docName="draft-xu-ospf-mpls-elc-01" ipr="trust200902">
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<!-- ***** FRONT MATTER ***** -->
<front>
<!-- The abbreviated title is used in the page header - it is only necessary if the
full title is longer than 39 characters -->
<title abbrev="Signallng ELC Using OSPF">Signaling Entropy Label
Capability Using OSPF</title>
<!-- add 'role="editor"' below for the editors if appropriate -->
<!-- Another author who claims to be an editor -->
<author fullname="Xiaohu Xu" initials="X.X." surname="Xu">
<organization>Huawei</organization>
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<email>xuxiaohu@huawei.com</email>
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</author>
<author fullname="Sriganesh Kini" initials="S.K." surname="Kini">
<organization>Ericsson</organization>
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<email>sriganesh.kini@ericsson.com</email>
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<author fullname="Siva Sivabalan" initials="S.S." surname="Sivabalan">
<organization>Cisco</organization>
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<email>msiva@cisco.com</email>
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</author>
<author fullname="Clarence Filsfils" initials="C.F." surname="Filsfils">
<organization>Cisco</organization>
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<author fullname="Stephane Litkowski" initials="S.L." surname="Litkowski">
<organization>Orange</organization>
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<abstract>
<t>Multi Protocol Label Switching (MPLS) has defined a mechanism to load
balance traffic flows using Entropy Labels (EL). An ingress LSR cannot
insert ELs for packets going into a given tunnel unless an egress LSR
has indicated via signaling that it can process ELs on that tunnel. This
draft defines a mechanism to signal that capability using OSPF. This
mechanism is useful when the label advertisement is also done via
OSPF.</t>
<t/>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>Multi Protocol Label Switching (MPLS) has defined a method in <xref
target="RFC6790"/> to load balance traffic flows using Entropy Labels
(EL). An ingress LSR cannot insert ELs for packets going into a given
tunnel unless an egress LSR has indicated that it can process ELs on
that tunnel. <xref target="RFC6790"/> defines the signaling of this
capability (a.k.a Entropy Label Capability - ELC) via signaling
protocols. Recently, mechanisms are being defined to signal labels via
link state Interior Gateway Protocols (IGP) such as OSPF <xref
target="I-D.ietf-ospf-segment-routing-extensions"/> . In such scenario
the signaling mechanisms defined in <xref target="RFC6790"/> are
inadequate. This draft defines a mechanism to signal the ELC using OSPF.
This mechanism is useful when the label advertisement is also done via
OSPF. In addition, in the cases where stacked LSPs are used for whatever
reasons (e.g., SPRING-MPLS <xref target="I-D.gredler-spring-mpls"/>
<xref target="I-D.filsfils-spring-segment-routing-mpls"/>), it would be
useful for ingress LSRs to know each LSR's capability of reading the
maximum label stack deepth. This capability, referred to as Readable
Label Stack Deepth Capability (RLSDC) can be used by ingress LSRs to
determine whether it's necessary to insert an EL for a given LSP tunnel
in the case where there has already been at least one EL in the label
stack <xref target="I-D.kini-mpls-spring-entropy-label"/> . Of course,
even it has been determined that it's neccessary to insert an EL for a
given LSP tunnel, if the egress LSR of that LSP tunnel has not yet
indicated that it can process ELs for that tunnel, the ingress LSR MUST
NOT include an entropy label for that tunnel as well. </t>
<section 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>
</section>
</section>
<section anchor="Abbreviations_Terminology" title="Terminology">
<t>This memo makes use of the terms defined in <xref target="RFC6790"/>
and <xref target="RFC4970"/>.</t>
</section>
<section anchor="ELC_OSPF" title="Advertising ELC Using OSPF">
<t>The OSPF Router Information (RI) Opaque LSA defined in <xref
target="RFC4970"/> is used by OSPF routers to announce their
capabilities. A new TLV within the body of this LSA, called ELC TLV is
defined to advertise the capability of the router to process the ELs. It
is formatted as described in Section 2.1 of <xref target="RFC4970"/>.
This TLV is applicable to both OSPFv2 and OSPFv3. The Type for the ELC
TLV needs to be assigned by IANA and it has a Length of zero. The scope
of the advertisement depends on the application but it is recommended
that it SHOULD be AS-scoped.</t>
</section>
<!--
-->
<section title="Advertising RLSDC Using OSPF">
<t>A new TLV within the body of the OSPF RI LSA, called RLSDC TLV is
defined to advertise the capability of the router to read the maximum
label stack depth. It is formatted as described in Section 2.1 of <xref
target="RFC4970"/> with a Type code to be assigned by IANA and a Length
of one. The Value field is set to the maximum readable label stack
deepth in the range between 1 to 255. The scope of the advertisement
depends on the application but it is RECOMMENDED that it SHOULD be
domain-wide. If a router has multiple linecards with different
capabilities of reading the maximum label stack deepth, the router MUST
advertise the smallest one in the RLSDC TLV. This TLV is applicable to
both OSPFv2 and OSPFv3.</t>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The authors would like to thank Yimin Shen and George Swallow for
their comments.</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>This memo includes a request to IANA to allocate two TLV types from
the OSPF RI TLVs registry.</t>
<!--
-->
</section>
<section anchor="Security" title="Security Considerations">
<t>This document does not introduce any new security risk.</t>
</section>
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