Status of This Memo

This document is not an Internet Standards Track specification; it is published for informational purposes.¶

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Table of Contents

1.Introduction

Four routing protocol extensions --OSPFv2 Extensions [RFC8665],OSPFv3 Extensions [RFC8666],IS-IS Extensions [RFC8667], andBGP Prefix Segment Identifiers (Prefix-SIDs) [RFC8669] -- and onePath Computation Element Communication Protocol (PCEP) Extension [RFC8664] have been defined to be able to propagate Segment Routing (SR) labels for the MPLS data plane[RFC8660].¶

Also,[SR-Traffic-Accounting] describes how IP Flow Information Export (IPFIX)[RFC7012] can be leveraged in dimensional data modeling to account for traffic to MPLS SR label dimensions within a Segment Routing domain.¶

In[RFC7012], the Information Element (IE) mplsTopLabelType(46) identifies which MPLS control plane protocol allocated the top-of-stack label in the MPLS label stack. PerSection 7.2 of [RFC7012], the"IPFIX MPLS label type (Value 46)" subregistry [IANA-IPFIX] was created, where new MPLS label type entries should be added. This document defines new code points to address typical use cases that are discussed inSection 2.¶

2.MPLS Segment Routing Top Label Type

By introducing five new code points to the IPFIX IE mplsTopLabelType(46) for Path Computation Element (PCE), IS-IS, OSPFv2, OSPFv3, and BGP Prefix-SIDs, it is possible to identify which traffic is being forwarded based upon which MPLS SR control plane protocol is in use.¶

A typical use case is to monitor MPLS control plane migrations from LDP to IS-IS or OSPF Segment Routing. Such a migration can be done node by node as described inAppendix A of [RFC8661].¶

Another use case is to monitor MPLS control plane migrations from dynamic BGP labels[RFC8277] to BGP Prefix-SIDs[RFC8669]. For example, the motivation for, and benefits of, such a migration in large-scale data centers are described in[RFC8670].¶

Both use cases can be verified by using mplsTopLabelType(46), mplsTopLabelIPv4Address(47), mplsTopLabelIPv6Address(140), mplsTopLabelStackSection(70), and forwardingStatus(89) IEs to infer¶

• how many packets are forwarded or dropped¶
• if packets are dropped, for which reasons, and¶
• the MPLS provider edge loopback address and label protocol¶

By looking at the MPLS label value itself, it is not always clear to which label protocol it belongs. This is because they may share the same label allocation range. This is, for example, the case for IGP-Adjacency SIDs, LDP, and dynamic BGP labels.¶

3.IANA Considerations

IANA has allocated the following code points in the "IPFIX MPLS label type (Value 46)" subregistry within the "IPFIX Information Elements" registry[RFC7012]. See[IANA-IPFIX].¶

References to RFCs 4364, 4271, and 5036 have been added to the "Reference" column in the "IPFIX MPLS label type (Value 46)" subregistry [IANA-IPFIX] for code points 3, 4, and 5, respectively. Previously, these references appeared in the "Additional Information" column for mplsTopLabelType(46) in the "IPFIX Information Elements" registry[IANA-IPFIX].¶

4.Operational Considerations

In the IE mplsTopLabelType(46), BGP code point 4 refers to the label value in the MP_REACH_NLRI path attribute described inSection 2 of [RFC8277], while BGP Segment Routing Prefix-SID code point 10 corresponds to the label index value in the Label-Index TLV described inSection 3.1 of [RFC8669]. These values are thus used for those distinct purposes.¶

5.Security Considerations

There exist no significant extra security considerations regarding the allocation of these new IPFIX IEs as compared to[RFC7012].¶

Acknowledgements

I would like to thank the IE doctors,Paul Aitken andAndrew Feren, as well asBenoît Claise,Loa Andersson,Tianran Zhou,Pierre François,Bruno Decraene,Paolo Lucente,Hannes Gredler,Ketan Talaulikar,Sabrina Tanamal,Erik Auerswald,Sergey Fomin,Mohamed Boucadair,Tom Petch,Qin Wu, andMatthias Arnold for their review and valuable comments. Many thanks also toRobert Wilton for the AD review. Thanks toAlvaro Retana,Éric Vyncke, andBenjamin Kaduk for the IESG review.¶

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