Internet Engineering Task Force (IETF) T. Graf
Request for Comments: 9160 Swisscom
Category: Informational December 2021
ISSN: 2070-1721
Export of MPLS Segment Routing Label Type Information in IP Flow
Information Export (IPFIX)
Abstract
This document introduces new IP Flow Information Export (IPFIX) code
points to identify which traffic is being forwarded based on which
MPLS control plane protocol is used within a Segment Routing domain.
In particular, this document defines five code points for the IPFIX
mplsTopLabelType Information Element for Path Computation Element
(PCE), IS-IS, OSPFv2, OSPFv3, and BGP MPLS Segment Routing
extensions.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9160.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction
2. MPLS Segment Routing Top Label Type
3. IANA Considerations
4. Operational Considerations
5. Security Considerations
6. References
6.1. Normative References
6.2. Informative References
Acknowledgements
Author's Address
1. Introduction
Four routing protocol extensions -- OSPFv2 Extensions [RFC8665],
OSPFv3 Extensions [RFC8666], IS-IS Extensions [RFC8667], and BGP
Prefix Segment Identifiers (Prefix-SIDs) [RFC8669] -- and one Path
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. Per Section 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 in Section 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 in Appendix 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].
+=======+================================+====================+
| Value | Description | Reference |
+=======+================================+====================+
| 6 | Path Computation Element | RFC 9160, RFC 8664 |
+-------+--------------------------------+--------------------+
| 7 | OSPFv2 Segment Routing | RFC 9160, RFC 8665 |
+-------+--------------------------------+--------------------+
| 8 | OSPFv3 Segment Routing | RFC 9160, RFC 8666 |
+-------+--------------------------------+--------------------+
| 9 | IS-IS Segment Routing | RFC 9160, RFC 8667 |
+-------+--------------------------------+--------------------+
| 10 | BGP Segment Routing Prefix-SID | RFC 9160, RFC 8669 |
+-------+--------------------------------+--------------------+
Table 1: Updates to "IPFIX MPLS label type (Value 46)"
Subregistry
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 in Section 2 of
[RFC8277], while BGP Segment Routing Prefix-SID code point 10
corresponds to the label index value in the Label-Index TLV described
in Section 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].
6. References
6.1. Normative References
[RFC7012] Claise, B., Ed. and B. Trammell, Ed., "Information Model
for IP Flow Information Export (IPFIX)", RFC 7012,
DOI 10.17487/RFC7012, September 2013,
<https://www.rfc-editor.org/info/rfc7012>.
6.2. Informative References
[IANA-IPFIX]
IANA, "IPFIX MPLS label type (Value 46)",
<https://www.iana.org/assignments/ipfix/>.
[RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address
Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017,
<https://www.rfc-editor.org/info/rfc8277>.
[RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing with the MPLS Data Plane", RFC 8660,
DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.
[RFC8661] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., and S. Litkowski, "Segment Routing MPLS
Interworking with LDP", RFC 8661, DOI 10.17487/RFC8661,
December 2019, <https://www.rfc-editor.org/info/rfc8661>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
[RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", RFC 8665,
DOI 10.17487/RFC8665, December 2019,
<https://www.rfc-editor.org/info/rfc8665>.
[RFC8666] Psenak, P., Ed. and S. Previdi, Ed., "OSPFv3 Extensions
for Segment Routing", RFC 8666, DOI 10.17487/RFC8666,
December 2019, <https://www.rfc-editor.org/info/rfc8666>.
[RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
Extensions for Segment Routing", RFC 8667,
DOI 10.17487/RFC8667, December 2019,
<https://www.rfc-editor.org/info/rfc8667>.
[RFC8669] Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah,
A., and H. Gredler, "Segment Routing Prefix Segment
Identifier Extensions for BGP", RFC 8669,
DOI 10.17487/RFC8669, December 2019,
<https://www.rfc-editor.org/info/rfc8669>.
[RFC8670] Filsfils, C., Ed., Previdi, S., Dawra, G., Aries, E., and
P. Lapukhov, "BGP Prefix Segment in Large-Scale Data
Centers", RFC 8670, DOI 10.17487/RFC8670, December 2019,
<https://www.rfc-editor.org/info/rfc8670>.
[SR-Traffic-Accounting]
Ali, Z., Filsfils, C., Talaulikar, K., Sivabalan, S.,
Horneffer, M., Raszuk, R., Litkowski, S., Voyer, D.,
Morton, R., and G. Dawra, "Traffic Accounting in Segment
Routing Networks", Work in Progress, Internet-Draft,
draft-ali-spring-sr-traffic-accounting-06, 13 November
2021, <https://datatracker.ietf.org/doc/html/draft-ali-
spring-sr-traffic-accounting-06>.
Acknowledgements
I would like to thank the IE doctors, Paul Aitken and Andrew Feren,
as well as Benoît 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, and Matthias Arnold for their review
and valuable comments. Many thanks also to Robert Wilton for the AD
review. Thanks to Alvaro Retana, Éric Vyncke, and Benjamin Kaduk for
the IESG review.
Author's Address
Thomas Graf
Swisscom
Binzring 17
CH-8045 Zürich
Switzerland
Email: thomas.graf@swisscom.com
