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2 MPLS Working Group L. Andersson
3 Internet-Draft Bronze Dragon Consulting
4 Updates: 3032, 7274 (if approved) K. Kompella
5 Intended status: Informational Juniper Networks
6 Expires: January 8, 2020 A. Farrel
7 Old Dog Consulting
8 July 7, 2019
10 Special Purpose Label terminology
11 draft-ietf-mpls-spl-terminology-00
13 Abstract
15 This document discusses and recommends a terminology that may be used
16 when MPLS Special Purpose Labels (SPL) are specified and documented.
18 Note: The rest of the text in this section is not really part of the
19 abstract even though the text is placed here. It is working notes.
21 Note: At least at the moment it is not the intention to take this
22 document to an RFC, but it might be polled to become a wg document to
23 see if the MPLS working group agree on the proposed terminology.
25 Note: The changes we propose are minor, but we might have to progress
26 the document to RFC since there is a proposed change to the "Special-
27 Purpose Multiprotocol Label Switching (MPLS) Label Values" registry.
29 Status of This Memo
31 This Internet-Draft is submitted in full conformance with the
32 provisions of BCP 78 and BCP 79.
34 Internet-Drafts are working documents of the Internet Engineering
35 Task Force (IETF). Note that other groups may also distribute
36 working documents as Internet-Drafts. The list of current Internet-
37 Drafts is at https://datatracker.ietf.org/drafts/current/.
39 Internet-Drafts are draft documents valid for a maximum of six months
40 and may be updated, replaced, or obsoleted by other documents at any
41 time. It is inappropriate to use Internet-Drafts as reference
42 material or to cite them other than as "work in progress."
44 This Internet-Draft will expire on January 8, 2020.
46 Copyright Notice
48 Copyright (c) 2019 IETF Trust and the persons identified as the
49 document authors. All rights reserved.
51 This document is subject to BCP 78 and the IETF Trust's Legal
52 Provisions Relating to IETF Documents
53 (https://trustee.ietf.org/license-info) in effect on the date of
54 publication of this document. Please review these documents
55 carefully, as they describe your rights and restrictions with respect
56 to this document. Code Components extracted from this document must
57 include Simplified BSD License text as described in Section 4.e of
58 the Trust Legal Provisions and are provided without warranty as
59 described in the Simplified BSD License.
61 Table of Contents
63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
64 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3
65 2.1. GMPLS Special Purpose Labels . . . . . . . . . . . . . . 3
66 3. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3
67 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
68 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
69 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
70 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
71 7.1. Normative References . . . . . . . . . . . . . . . . . . 5
72 7.2. Informative References . . . . . . . . . . . . . . . . . 6
73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
75 1. Introduction
77 RFC 7274 [RFC7274] made some changes to the terminology used for MPLS
78 Special Purpose Labels, but did not define consistent terminology.
80 One thing that RFC 7274 did was to deprecate use use of the term
81 "reserved labels" when describing a range of labels allocated from a
82 registry maintained by IANA. The term "Reserved" in such a registry
83 means "set aside, not to be used", but that range of labels was
84 available for allocation according to the policies set out in the
85 registry. The name "Special Purpose Labels" was introduced in RFC
86 7274 in place of the previous term, and the abbreviation SPL was
87 recommended.
89 At the time of posting this Internet-Draft, the IETF is in the
90 process of allocating the very first SPLs from the Extended SPL range
91 [I-D.ietf-mpls-sfc]. This document discusses and recommends
92 terminology and abbreviations to be used when talking about and
93 documentating Special Purpose Labels.
95 2. Background
97 Two sets of SPLs are defined for use in MPLS:
99 The range of SPLs 0-15 is specified in RFC 3032 [RFC3032].
101 The range of SPLs 0-1048575 is specified in RFC 7274 [RFC7274].
103 * the values 0-15 has been reserved never to be allocated
105 * the values 15-239 are available for allocation
107 * the values 240-255 are for experimental use
109 * the values 256-1048575 are currently not available for
110 allocation, and a standard tracks RFC will be needed to make
111 the entire range or part of it available for allocation
113 2.1. GMPLS Special Purpose Labels
115 Note that IANA maintains a registry called "Special Purpose
116 Generalized Label Values". Labels in that registry have special
117 meaning when present in certain signalling objects, are 32 bits long,
118 and are not to be confused with MPLS forwarding plane labels. This
119 document does not make any changes to the registry or how labels from
120 that registry are described.
122 3. Terminology and Abbreviations
124 IANA maintains a name space for 'Special-Purpose Multiprotocol Label
125 Switching (MPLS) Label Values' code points [SPL-NAME-SPACE]. Within
126 this name space there are two registries. One is called the
127 'Special-Purpose MPLS Label Values' registry [bSPL]. The other is
128 called 'Extended Special-Purpose MPLS Label Values' registry [eSPL].
130 The difference in the name of the name space and the first registry
131 is only that the MPLS abbreviation is expanded. This document
132 changes the name of the first registry to 'Base Special-Purpose MPLS
133 Label Values', but leaves the name of the latter registry unchanged
134 as 'Extended Special-Purpose MPLS Label Values'.
136 The following conventions will be used in specifications and when
137 talking about SPLs
139 o Collectively, the two ranges are known as Special Purpose Labels
140 (SPL).
142 o The special purpose labels from the lower range will be called
143 Base Special Purpose Labels (bSPL).
145 o The special purpose labels from the higher range will be called
146 Extended Special Purpose Labels (eSPL).
148 o The combination of the Extension Label (XL) (value 15 which is an
149 bSPL, but that is also called xSPL) and an eSPL is called a
150 Composite Special Purpose Label (cSPL).
152 This results in a label stacks such as the illustrative examples
153 shown in Figure 1 and Figure 2.
155 0 31
156 | MPLS Label Stack entry |
157 +--------+--------+--------+--------+
158 | MPLS Label Stack entry |
159 +--------+--------+--------+--------+
160 bSPL | Base SPL |
161 +--------+--------+--------+--------+
162 | MPLS Label Stack entry (cont.) |
164 Figure 1: Example of Label Stack
166 0 31
167 | MPLS Label Stack entry |
168 +--------+--------+--------+--------+
169 | MPLS Label Stack entry |
170 +--------+--------+--------+--------+
171 xSPL | Extension Label (XL) | <--+
172 +--------+--------+--------+--------+ |--- cSPL
173 eSPL | Extended SPL | <--+
174 +--------+--------+--------+--------+
175 | MPLS Label Stack entry (cont.) |
177 Figure 2: Example of Label Stack
179 4. Security Considerations
181 This document is entirely about terminology for SPLs and does not
182 effect the forwarding in the MPLS data plane, nor does it have any
183 effect on how LSPs are establsihed by an MPLS control plane or by a
184 centralized controller. The doucment describes a terminology to be
185 used when describing and specifying the use of SPLs.
187 This document does not aim to describe existing implementations of
188 SPLs or the potential vulnerabilities of SPLs.
190 5. IANA Considerations
192 We request that the name of the IANA registry that today is called
193 "Special-Purpose MPLS Label Values" is changed to "Base Special-
194 Purpose MPLS Label Values".
196 6. Acknowledgements
198 The authors of this document would like to thank Stewart Bryant for
199 careful review and constructive suggestions.
201 7. References
203 7.1. Normative References
205 [bSPL] "Special-Purpose MPLS Label Values",
206 .
209 [eSPL] "Extended Special-Purpose MPLS Label Values",
210 .
213 [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
214 Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
215 Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
216 .
218 [RFC7274] Kompella, K., Andersson, L., and A. Farrel, "Allocating
219 and Retiring Special-Purpose MPLS Labels", RFC 7274,
220 DOI 10.17487/RFC7274, June 2014,
221 .
223 [SPL-NAME-SPACE]
224 "Special-Purpose Multiprotocol Label Switching (MPLS)
225 Label Values", .
228 7.2. Informative References
230 [I-D.ietf-mpls-sfc]
231 Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based
232 Forwarding Plane for Service Function Chaining", draft-
233 ietf-mpls-sfc-07 (work in progress), March 2019.
235 Authors' Addresses
237 Loa Andersson
238 Bronze Dragon Consulting
240 Email: loa@pi.nu
242 Kireeti Kompella
243 Juniper Networks
245 Email: kireeti@juniper.net
247 Adrian Farrel
248 Old Dog Consulting
250 Email: adrian@olddog.co.uk