Special Purpose Label terminology
The information below is for an old version of the document.
This is an older version of an Internet-Draft that was ultimately published as RFC 9017.
|Authors||Loa Andersson , Kireeti Kompella , Adrian Farrel|
|Last updated||2020-09-15 (Latest revision 2020-08-12)|
|RFC stream||Internet Engineering Task Force (IETF)|
|Additional resources||Mailing list discussion|
|Stream||WG state||WG Document|
|Document shepherd||Nicolai Leymann|
|Shepherd write-up||Show Last changed 2020-07-08|
|IESG||IESG state||AD is watching::Revised I-D Needed|
|Responsible AD||Deborah Brungard|
|Send notices to||Nicolai Leymann <email@example.com>|
|IANA||IANA review state||IANA OK - Actions Needed|
MPLS Working Group L. Andersson Internet-Draft Bronze Dragon Consulting Updates: 3032, 7274 (if approved) K. Kompella Intended status: Informational Juniper Networks Expires: February 13, 2021 A. Farrel Old Dog Consulting August 12, 2020 Special Purpose Label terminology draft-ietf-mpls-spl-terminology-03 Abstract This document discusses and recommends a terminology that may be used when MPLS Special Purpose Labels (SPL) are specified and documented. This document updates RFC 7274 and RFC 3032. 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 working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on February 13, 2021. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Andersson, et al. Expires February 13, 2021 [Page 1] Internet-Draft SPL Terminology August 2020 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1. GMPLS Special Purpose Labels . . . . . . . . . . . . . . 3 3. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 5 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 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 that 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 writing the first version of this document, the IETF was in the process of allocating the very first SPLs from the Extended SPL (eSPL) range [RFC8595]. This document discusses and recommends terminology and abbreviations to be used when talking about and documenting Special Purpose Labels. This document updates RFC 3032 [RFC3032] and RFC 7274 [RFC7274] in that it changes the terminology for both Base SPLs and Extended SPLs. 2. Background Two sets of SPLs are defined for use in MPLS: The range of 0-15, Base Special Purpose Labels (bSPLs), is specified in RFC 3032 [RFC3032]. The range 0-1048575 of eSPLs is specified in RFC 7274 [RFC7274]. Andersson, et al. Expires February 13, 2021 [Page 2] Internet-Draft SPL Terminology August 2020 * the values 0-15 have been reserved never to be allocated * the values 16-239 are available for allocation * the values 240-255 are for experimental use * the values 256-1048575 are currently not available for allocation. A standard track RFC will be needed to allocate any labels from this range. 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 GMPLS registry or to 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). 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 a bSPL, but that is also called xSPL) and an eSPL is called a Composite Special Purpose Label (cSPL). Andersson, et al. Expires February 13, 2021 [Page 3] Internet-Draft SPL Terminology August 2020 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 4. Security Considerations The document describes the terminology to be used when describing and 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 established by an MPLS control plane or by a centralized controller. This document does not aim to describe existing implementations of SPLs or potential vulnerabilities of SPLs. Andersson, et al. Expires February 13, 2021 [Page 4] Internet-Draft SPL Terminology August 2020 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. We would also like to thank the Routing Directorate reviwer Eric Gray for a detailed, careful and insightful review. 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>. [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 [RFC8595] Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based Forwarding Plane for Service Function Chaining", RFC 8595, DOI 10.17487/RFC8595, June 2019, <https://www.rfc-editor.org/info/rfc8595>. Andersson, et al. Expires February 13, 2021 [Page 5] Internet-Draft SPL Terminology August 2020 Authors' Addresses Loa Andersson Bronze Dragon Consulting Email: firstname.lastname@example.org Kireeti Kompella Juniper Networks Email: email@example.com Adrian Farrel Old Dog Consulting Email: firstname.lastname@example.org Andersson, et al. Expires February 13, 2021 [Page 6]