draft-ietf-mpls-spl-terminology-03.txt   draft-ietf-mpls-spl-terminology-04.txt 
MPLS Working Group L. Andersson MPLS Working Group L. Andersson
Internet-Draft Bronze Dragon Consulting Internet-Draft Bronze Dragon Consulting
Updates: 3032, 7274 (if approved) K. Kompella Updates: 3032, 7274 (if approved) K. Kompella
Intended status: Informational Juniper Networks Intended status: Standards Track Juniper Networks
Expires: February 13, 2021 A. Farrel Expires: March 28, 2021 A. Farrel
Old Dog Consulting Old Dog Consulting
August 12, 2020 September 24, 2020
Special Purpose Label terminology Special Purpose Label terminology
draft-ietf-mpls-spl-terminology-03 draft-ietf-mpls-spl-terminology-04
Abstract Abstract
This document discusses and recommends a terminology that may be used This document discusses and recommends a terminology that may be used
when MPLS Special Purpose Labels (SPL) are specified and documented. when MPLS Special Purpose Labels (SPL) are specified and documented.
This document applies that terminology change to the relevant IANA
registry and also clarifies the use of the Entropy Label Indicator
(7) when immediately preceded by the Extension Label (15).
This document updates RFC 7274 and RFC 3032. This document updates RFC 7274 and RFC 3032.
Status of This Memo Status of This Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Copyright Notice Copyright Notice
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. GMPLS Special Purpose Labels . . . . . . . . . . . . . . 3 2.1. GMPLS Special Purpose Labels . . . . . . . . . . . . . . 3
3. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3 3. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4. Clarification on Use of Entropy Label Indicator . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 5 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 5 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
RFC 7274 [RFC7274] made some changes to the terminology used for MPLS RFC 7274 [RFC7274] made some changes to the terminology used for MPLS
Special Purpose Labels, but did not define consistent terminology. Special Purpose Labels, but did not define consistent terminology.
One thing that RFC 7274 did was to deprecate use of the term One thing that RFC 7274 did was to deprecate use of the term
"reserved labels" when describing a range of labels allocated from a "reserved labels" when describing a range of labels allocated from a
registry maintained by IANA. The term "Reserved" in such a registry registry maintained by IANA. The term "Reserved" in such a registry
means "set aside, not to be used", but that range of labels was means "set aside, not to be used", but that range of labels was
skipping to change at page 2, line 44 skipping to change at page 3, line 5
At the time of writing the first version of this document, the IETF At the time of writing the first version of this document, the IETF
was in the process of allocating the very first SPLs from the was in the process of allocating the very first SPLs from the
Extended SPL (eSPL) range [RFC8595]. This document discusses and Extended SPL (eSPL) range [RFC8595]. This document discusses and
recommends terminology and abbreviations to be used when talking recommends terminology and abbreviations to be used when talking
about and documenting Special Purpose Labels. about and documenting Special Purpose Labels.
This document updates RFC 3032 [RFC3032] and RFC 7274 [RFC7274] in This document updates RFC 3032 [RFC3032] and RFC 7274 [RFC7274] in
that it changes the terminology for both Base SPLs and Extended SPLs. that it changes the terminology for both Base SPLs and Extended SPLs.
This document applies that terminology change to the relevant IANA
registry and also clarifies the use of the Entropy Label Indicator
(7) when immediately preceded by the Extension Label (15).
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Background 2. Background
Two sets of SPLs are defined for use in MPLS: Two sets of SPLs are defined for use in MPLS:
The range of 0-15, Base Special Purpose Labels (bSPLs), is The range of 0-15, Base Special Purpose Labels (bSPLs), is
specified in RFC 3032 [RFC3032]. specified in RFC 3032 [RFC3032].
The range 0-1048575 of eSPLs is specified in RFC 7274 [RFC7274]. The range 0-1048575 of eSPLs is specified in RFC 7274 [RFC7274].
* the values 0-15 have been reserved never to be allocated * the values 0-15 have been reserved never to be allocated
skipping to change at page 3, line 39 skipping to change at page 4, line 12
'Special-Purpose MPLS Label Values' registry [bSPL]. The other is 'Special-Purpose MPLS Label Values' registry [bSPL]. The other is
called 'Extended Special-Purpose MPLS Label Values' registry [eSPL]. called 'Extended Special-Purpose MPLS Label Values' registry [eSPL].
The difference in the name of the name space and the first registry The difference in the name of the name space and the first registry
is only that the MPLS abbreviation is expanded. This document is only that the MPLS abbreviation is expanded. This document
changes the name of the first registry to 'Base Special-Purpose MPLS changes the name of the first registry to 'Base Special-Purpose MPLS
Label Values', but leaves the name of the latter registry unchanged Label Values', but leaves the name of the latter registry unchanged
as 'Extended Special-Purpose MPLS Label Values'. as 'Extended Special-Purpose MPLS Label Values'.
The following conventions will be used in specifications and when The following conventions will be used in specifications and when
talking about SPLs talking about SPLs.
o Collectively, the two ranges are known as Special Purpose Labels
(SPL).
o The special purpose labels from the lower range will be called o Collectively, the two (unrelated) ranges (0-15 and 16-1048575) are
Base Special Purpose Labels (bSPL). known as Special Purpose Labels (SPL).
o The special purpose labels from the higher range will be called o Special purpose labels from the range 0-15 are called Base Special
Extended Special Purpose Labels (eSPL). Purpose Labels (bSPL).
o The combination of the Extension Label (XL) (value 15 which is a o Special purpose labels from the range 16-1048575 are called
bSPL, but that is also called xSPL) and an eSPL is called a Extended Special Purpose Labels (eSPL). (Note that the reserved
Composite Special Purpose Label (cSPL). values 0-15 from the 'Extended Special-Purpose MPLS Label Values'
registry do not need a name as they are not available for
allocation and MUST NOT be used.)
This results in a label stacks such as the illustrative examples This results in a label stacks such as the illustrative examples
shown in Figure 1 and Figure 2. shown in Figure 1 and Figure 2.
0 31 0 31
| MPLS Label Stack entry | | MPLS Label Stack entry |
+--------+--------+--------+--------+ +--------+--------+--------+--------+
| MPLS Label Stack entry | | MPLS Label Stack entry |
+--------+--------+--------+--------+ +--------+--------+--------+--------+
bSPL | Base SPL | bSPL | Base SPL |
skipping to change at page 4, line 32 skipping to change at page 5, line 18
| MPLS Label Stack entry | | MPLS Label Stack entry |
+--------+--------+--------+--------+ +--------+--------+--------+--------+
xSPL | Extension Label (XL) | <--+ xSPL | Extension Label (XL) | <--+
+--------+--------+--------+--------+ |--- cSPL +--------+--------+--------+--------+ |--- cSPL
eSPL | Extended SPL | <--+ eSPL | Extended SPL | <--+
+--------+--------+--------+--------+ +--------+--------+--------+--------+
| MPLS Label Stack entry (cont.) | | MPLS Label Stack entry (cont.) |
Figure 2: Example of Label Stack Figure 2: Example of Label Stack
4. Security Considerations 4. Clarification on Use of Entropy Label Indicator
Section 3.1 of [RFC7274] contains two paragraphs that describe the
use of the Entropy Label Indicator (label 7). These paragraphs have
introduced some confusion about whether the Entropy Label Indicator
can be present when immediately preceded by the Extension Label.
This document updates [RFC7274] by replacing those paragraphs as
follows.
OLD
Values 0-15 of the "Extended Special-Purpose MPLS Label Values"
registry are set aside as reserved. Furthermore, values 0-6 and
8-15 MUST NOT appear in the data plane following an XL; an LSR
processing a packet with an XL at the top of the label stack
followed by a label with value 0-6 or 8-15 MUST drop the packet.
Label 7 (when received) retains its meaning as Entropy Label
Indicator (ELI) whether a regular special-purpose label or an
ESPL; this is because of backwards compatibility with existing
implemented and deployed code and hardware that looks for the ELI
without verifying if the previous label is XL or not. However,
when an LSR inserts an entropy label, it MUST insert the ELI as a
regular special-purpose label, not as an ESPL.
NEW
Values 0-15 of the "Extended Special-Purpose MPLS Label Values"
registry are set aside as reserved. Furthermore, an
implementation MUST NOT place a label with value 0-15 in the label
stack immediately following an XL; an LSR processing a packet with
an XL at the top of the label stack immediately followed by a
label with value 0-15 MUST drop the packet.
When inspecting a label stack to find an Entropy Label Indicator
(ELI - label 7) a pre-existing implementation may fail to inspect
the previous label, and so not notice that it is an XL. Such
systems can continue to process the entropy information and
forward the packet when the previous label is an XP without
causing harm. However, the packet will be dropped when the XL
reaches the top of the stack at another LSR.
END
5. Security Considerations
The document describes the terminology to be used when describing and The document describes the terminology to be used when describing and
specifying the use of SPLs. It does not effect the forwarding in the specifying the use of SPLs. It does not effect the forwarding in the
MPLS data plane, nor does it have any effect on how LSPs are MPLS data plane, nor does it have any effect on how LSPs are
established by an MPLS control plane or by a centralized controller. established by an MPLS control plane or by a centralized controller.
This document does not aim to describe existing implementations of This document does not aim to describe existing implementations of
SPLs or potential vulnerabilities of SPLs. SPLs or potential vulnerabilities of SPLs.
5. IANA Considerations 6. IANA Considerations
We request that the name of the IANA registry that today is called IANA is requested to change the name of the registry that today is
"Special-Purpose MPLS Label Values" is changed to "Base Special- called "Special-Purpose MPLS Label Values" is changed to "Base
Purpose MPLS Label Values". Special- Purpose MPLS Label Values".
6. Acknowledgements 7. Acknowledgements
The authors of this document would like to thank Stewart Bryant for We like to thank the Routing Directorate reviwer Eric Gray for a
careful review and constructive suggestions. detailed, careful and insightful review, and Tom Petch for pointing
out several issues of clarity.
We would also like to thank the Routing Directorate reviwer Eric Gray 8. Contributors
for a detailed, careful and insightful review.
7. References The following people contributed text to this document:
7.1. Normative References Stewart Bryant
Futurewei Technologies Inc.
Email: stewart.bryant@gmail.com
Figure 3
9. References
9.1. Normative References
[bSPL] "Special-Purpose MPLS Label Values", [bSPL] "Special-Purpose MPLS Label Values",
<https://www.iana.org/assignments/mpls-label-values/mpls- <https://www.iana.org/assignments/mpls-label-values/mpls-
label-values.xhtml#special-purpose/>. label-values.xhtml#special-purpose/>.
[eSPL] "Extended Special-Purpose MPLS Label Values", [eSPL] "Extended Special-Purpose MPLS Label Values",
<https://www.iana.org/assignments/mpls-label-values/mpls- <https://www.iana.org/assignments/mpls-label-values/mpls-
label-values.xhtml#extended/>. label-values.xhtml#extended/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>. <https://www.rfc-editor.org/info/rfc3032>.
[RFC7274] Kompella, K., Andersson, L., and A. Farrel, "Allocating [RFC7274] Kompella, K., Andersson, L., and A. Farrel, "Allocating
and Retiring Special-Purpose MPLS Labels", RFC 7274, and Retiring Special-Purpose MPLS Labels", RFC 7274,
DOI 10.17487/RFC7274, June 2014, DOI 10.17487/RFC7274, June 2014,
<https://www.rfc-editor.org/info/rfc7274>. <https://www.rfc-editor.org/info/rfc7274>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[SPL-NAME-SPACE] [SPL-NAME-SPACE]
"Special-Purpose Multiprotocol Label Switching (MPLS) "Special-Purpose Multiprotocol Label Switching (MPLS)
Label Values", <https://www.iana.org/assignments/mpls- Label Values", <https://www.iana.org/assignments/mpls-
label-values/mpls-label-values.xhtml/>. label-values/mpls-label-values.xhtml/>.
7.2. Informative References 9.2. Informative References
[RFC8595] Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based [RFC8595] Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based
Forwarding Plane for Service Function Chaining", RFC 8595, Forwarding Plane for Service Function Chaining", RFC 8595,
DOI 10.17487/RFC8595, June 2019, DOI 10.17487/RFC8595, June 2019,
<https://www.rfc-editor.org/info/rfc8595>. <https://www.rfc-editor.org/info/rfc8595>.
Authors' Addresses Authors' Addresses
Loa Andersson Loa Andersson
Bronze Dragon Consulting Bronze Dragon Consulting
Email: loa@pi.nu Email: loa@pi.nu
Kireeti Kompella Kireeti Kompella
Juniper Networks Juniper Networks
Email: kireeti@juniper.net Email: kireeti@juniper.net
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