Internet DRAFT - draft-andersson-mpls-spl-terminology
draft-andersson-mpls-spl-terminology
MPLS Working Group L. Andersson
Internet-Draft Bronze Dragon Consulting
Updates: 3032, 7274 (if approved) K. Kompella
Intended status: Informational Juniper Networks
Expires: August 30, 2019 A. Farrel
Old Dog Consulting
February 26, 2019
Special Purpose Label terminology
draft-andersson-mpls-spl-terminology-01
Abstract
This document discusses and recommends a terminology that may be used
when MPLS Special Purpose Labels (SPL) are specified and documented.
Note: The rest of the text in this section is not really part of the
abstract even though the text is placed here. It is working notes.
Note: At least at the moment it is not the intention to take this
document to an RFC, but it might be polled to become a wg document to
see if the MPLS working group agree on the proposed terminology.
Note: The changes we propose are minor, but we might have to progress
the document to RFC since there is a proposed change to the "Special-
Purpose Multiprotocol Label Switching (MPLS) Label Values" registry.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 30, 2019.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. GMPLS Special Purpose Labels . . . . . . . . . . . . . . 3
3. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
RFC 7274 [RFC7274] made some changes to the terminology used for MPLS
Special Purpose Labels, but did not define consistent terminology.
One thing that RFC 7274 did was to deprecate use use of the term
"reserved labels" when describing a range of labels allocated from a
registry maintained by IANA. The term "Reserved" in such a registry
means "set aside, not to be used", but that range of labels was
available for allocation according to the policies set out in the
registry. The name "Special Purpose Labels" was introduced in RFC
7274 in place of the previous term, and the abbreviation SPL was
recommended.
At the time of posting this Internet-Draft, the IETF is in the
process of allocating the very first SPLs from the Extended SPL range
[I-D.ietf-mpls-sfc]. This document discusses and recommends
terminology and abbreviations to be used when talking about and
documentating Special Purpose Labels.
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2. Background
Two sets of SPLs are defined for use in MPLS:
The range of SPLs 0-15 is specified in RFC 3032 [RFC3032].
The range of SPLs 0-1048575 is specified in RFC 7274 [RFC7274].
* the values 0-15 has been reserved never to be allocated
* the values 15-239 are available for allocation
* the values 240-255 are for experimental use
* the values 256-1048575 are currently not available for
allocation, and a standard tracks RFC will be needed to make
the entire range or part of it available for allocation
2.1. GMPLS Special Purpose Labels
Note that IANA maintains a registry called "Special Purpose
Generalized Label Values". Labels in that registry have special
meaning when present in certain signalling objects, are 32 bits long,
and are not to be confused with MPLS forwarding plane labels. This
document does not make any changes to the registry or how labels from
that registry are described.
3. Terminology and Abbreviations
IANA maintains a name space for 'Special-Purpose Multiprotocol Label
Switching (MPLS) Label Values' code points [SPL-NAME-SPACE]. Within
this name space there are two registries. One is called the
'Special-Purpose MPLS Label Values' registry [bSPL]. The other is
called 'Extended Special-Purpose MPLS Label Values' registry [eSPL].
The difference in the name of the name space and the first registry
is only that the MPLS abbreviation is expanded. This document
changes the name of the first registry to 'Base Special-Purpose MPLS
Label Values', but leaves the name of the latter registry unchanged
as 'Extended Special-Purpose MPLS Label Values'.
The following conventions will be used in specifications and when
talking about SPLs
o Collectively, the two ranges are known as Special Purpose Labels
(SPL).
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o The special purpose labels from the lower range will be called
Base Special Purpose Labels (bSPL).
o The special purpose labels from the higher range will be called
Extended Special Purpose Labels (eSPL).
o The combination of the Extension Label (XL) (value 15 which is an
bSPL, but that is also called xSPL) and an eSPL is called a
Composite Special Purpose Label (cSPL).
This results in a label stacks such as the illustrative examples
shown in Figure 1 and Figure 2.
0 31
| MPLS Label Stack entry |
+--------+--------+--------+--------+
| MPLS Label Stack entry |
+--------+--------+--------+--------+
bSPL | Base SPL |
+--------+--------+--------+--------+
| MPLS Label Stack entry (cont.) |
Figure 1: Example of Label Stack
0 31
| MPLS Label Stack entry |
+--------+--------+--------+--------+
| MPLS Label Stack entry |
+--------+--------+--------+--------+
xSPL | Extension Label (XL) | <--+
+--------+--------+--------+--------+ |--- cSPL
eSPL | Extended SPL | <--+
+--------+--------+--------+--------+
| MPLS Label Stack entry (cont.) |
Figure 2: Example of Label Stack
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4. Security Considerations
This document is entirely about terminology for SPLs and does not
effect the forwarding in the MPLS data plane, nor does it have any
effect on how LSPs are establsihed by an MPLS control plane or by a
centralized controller. The doucment describes a terminology to be
used when describing and specifying the use of SPLs.
This document does not aim to describe existing implementations of
SPLs or the potential vulnerabilities of SPLs.
5. IANA Considerations
We request that the name of the IANA registry that today is called
"Special-Purpose MPLS Label Values" is changed to "Base Special-
Purpose MPLS Label Values".
6. Acknowledgements
The authors of this document would like to thank Stewart Bryant for
careful review and constructive suggestions.
-
7. References
7.1. Normative References
[bSPL] "Special-Purpose MPLS Label Values",
<https://www.iana.org/assignments/mpls-label-values/
mpls-label-values.xhtml#special-purpose/>.
[eSPL] "Extended Special-Purpose MPLS Label Values",
<https://www.iana.org/assignments/mpls-label-values/
mpls-label-values.xhtml#extended/>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.
[RFC7274] Kompella, K., Andersson, L., and A. Farrel, "Allocating
and Retiring Special-Purpose MPLS Labels", RFC 7274,
DOI 10.17487/RFC7274, June 2014,
<https://www.rfc-editor.org/info/rfc7274>.
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[SPL-NAME-SPACE]
"Special-Purpose Multiprotocol Label Switching (MPLS)
Label Values", <https://www.iana.org/assignments/
mpls-label-values/mpls-label-values.xhtml/>.
7.2. Informative References
[I-D.ietf-mpls-sfc]
Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based
Forwarding Plane for Service Function Chaining", draft-
ietf-mpls-sfc-05 (work in progress), February 2019.
Authors' Addresses
Loa Andersson
Bronze Dragon Consulting
Email: loa@pi.nu
Kireeti Kompella
Juniper Networks
Email: kireeti@juniper.net
Adrian Farrel
Old Dog Consulting
Email: adrian@olddog.co.uk
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