Internet Engineering Task Force (IETF) R. Winter

Internet Engineering Task Force (IETF) R. Winter
Request for Comments: 6923 NEC
Category: Standards Track E. Gray
ISSN: 2070-1721 Ericsson
H. van Helvoort
Huawei Technologies Co., Ltd.
M. Betts
ZTE
May 2013

MPLS Transport Profile (MPLS-TP) Identifiers
Following ITU-T Conventions

Abstract

This document specifies an extension to the identifiers to be used in
the Transport Profile of Multiprotocol Label Switching (MPLS-TP).
Identifiers that follow IP/MPLS conventions have already been
defined. This memo augments that set of identifiers for MPLS-TP
management and Operations, Administration, and Maintenance (OAM)
functions to include identifier information in a format typically
used by the International Telecommunication Union Telecommunication
Standardization Sector (ITU-T).

Status of This Memo

This is an Internet Standards Track document.

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). Further information on
Internet Standards is available in Section 2 of RFC 5741.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6923.

Winter, et al. Standards Track [Page 1]

RFC 6923 MPLS-TP ITU-T IDs May 2013

Copyright Notice

Copyright (c) 2013 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
(http://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
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction ....................................................2
1.1. Terminology ................................................3
1.2. Requirements Notation ......................................4
1.3. Notational Conventions .....................................4
2. Named Entities ..................................................4
3. Uniquely Identifying an Operator -- the ICC_Operator_ID .........5
3.1. Use of the ICC_Operator_ID .................................6
4. Node and Interface Identifiers ..................................7
5. MPLS-TP Tunnel and LSP Identifiers ..............................7
5.1. MPLS-TP Point-to-Point Tunnel Identifiers ..................7
5.2. MPLS-TP LSP Identifiers ....................................8
5.2.1. MPLS-TP Co-Routed Bidirectional LSP Identifiers .....8
5.2.2. MPLS-TP Associated Bidirectional LSP Identifiers ....9
6. Pseudowire Path Identifiers .....................................9
7. Maintenance Identifiers .........................................9
7.1. MEG Identifiers ...........................................10
7.2. MEP Identifiers ...........................................10
7.3. MIP Identifiers ...........................................10
8. Security Considerations ........................................11
9. References .....................................................11
9.1. Normative References ......................................11
9.2. Informative References ....................................12

1. Introduction

This document augments the initial set of identifiers to be used in
the Transport Profile of Multiprotocol Label Switching (MPLS-TP)
defined in [RFC6370] by adding new identifiers based on ITU-T
conventions. It is not intended that both types of identifiers will
be used at the same time in the same domain.

Winter, et al. Standards Track [Page 2]

RFC 6923 MPLS-TP ITU-T IDs May 2013

[RFC6370] defines a set of MPLS-TP transport and management entity
identifiers to support bidirectional (co-routed and associated)
point-to-point MPLS-TP Label Switched Paths (LSPs), including
Pseudowires (PWs) and Sections that follow the IP/MPLS conventions.

This document specifies an alternative way to generate unambiguous
identifiers for operators/service providers based on ITU-T
conventions and specifies how these operator/service provider
identifiers can be used to generate unambiguous identifiers for the
existing set of identifiable MPLS-TP entities described in [RFC6370].

This document solely defines those identifiers. Their use and
possible protocol extensions to carry them are out of the scope of
this document.

In this document, we follow the notational convention laid out in
[RFC6370], which is included in this document for convenience in
Section 1.3.

1.1. Terminology

CC: Country Code

ICC: ITU Carrier Code

ISO: International Organization for Standardization

ITU: International Telecommunication Union

ITU-T: ITU Telecommunication Standardization Sector

LSP: Label Switched Path

MEG: Maintenance Entity Group

MEP: Maintenance Entity Group End Point

MIP: Maintenance Entity Group Intermediate Point

MPLS: Multiprotocol Label Switching

PW: Pseudowire

TSB: (ITU-T) Telecommunication Standardization Bureau

UMC: Unique MEG ID Code

Winter, et al. Standards Track [Page 3]

RFC 6923 MPLS-TP ITU-T IDs May 2013

1.2. Requirements Notation

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

1.3. Notational Conventions

This document uses the notational conventions laid out in [RFC6370]:

All multiple-word atomic identifiers use underscores (_) between
the words to join the words. Many of the identifiers are composed
of a set of other identifiers. These are expressed by listing the
latter identifiers joined with double-colon "::" notation.

Where the same identifier type is used multiple times in a
concatenation, they are qualified by a prefix joined to the
identifier by a dash (-). For example, A1-Node_ID is the Node_ID
of a node referred to as A1.

The notation defines a preferred ordering of the fields.
Specifically, the designation A1 is used to indicate the lower
sort order of a field or set of fields and Z9 is used to indicate
the higher sort order of the same. The sort is either
alphanumeric or numeric depending on the field's definition.
Where the sort applies to a group of fields, those fields are
grouped with {...}.

Note, however, that the uniqueness of an identifier does not
depend on the ordering, but rather, upon the uniqueness and
scoping of the fields that compose the identifier. Further, the
preferred ordering is not intended to constrain protocol designs
by dictating a particular field sequence ... or even what fields
appear in which objects.

2. Named Entities

This document provides additional identifiers supplementing those
defined in [RFC6370]. The identifiers in [RFC6370] are composed of a
set of atomic identifiers, and this document defines some new atomic
identifiers that can be substituted for some of those that have
already been defined, to create new identifiers. The set of
identifiers defined in [RFC6370] is:

o Global_ID

o Node

Winter, et al. Standards Track [Page 4]

RFC 6923 MPLS-TP ITU-T IDs May 2013

o Interface

o Tunnel

o LSP

o PW

o MEG

o MEP

o MIP

The following sections go through this list of identifiers one by
one. The structure of this document is loosely aligned with the
structure of [RFC6370].

3. Uniquely Identifying an Operator -- the ICC_Operator_ID

In [RFC6370], an operator is uniquely identified by the Global_ID,
which is based on the Autonomous System (AS) number of the operator.
The ITU-T, however, traditionally identifies operators and service
providers based on the ITU Carrier Code (ICC) as specified in
[M1400].

The ITU-T Telecommunication Standardization Bureau (TSB) maintains a
list of assigned ICCs [ICC-list]. Note that ICCs, all of which are
referenced at [ICC-list], can be assigned to ITU-T members as well as
non-members. The national regulatory authorities act as an
intermediary between the ITU/TSB and operators/service providers.
One of the things that the national authorities are responsible for
in the process of assigning an ICC is to ensure that the Carrier
Codes are unique within their country. This uniqueness assumption is
the basis for creating a globally unique ICC-based operator ID.

The ICC itself is a string of one to six characters, each character
being either alphabetic (i.e., A-Z) or numeric (i.e., 0-9).
Alphabetic characters in the ICC SHOULD be represented with uppercase
letters.

Global uniqueness is assured by concatenating the ICC with a Country
Code (CC). The Country Code (alpha-2) is a string of two alphabetic
characters represented with uppercase letters (i.e., A-Z).

Winter, et al. Standards Track [Page 5]

RFC 6923 MPLS-TP ITU-T IDs May 2013

The International Organization for Standardization (ISO) establishes
internationally recognized codes for the representation of names of
countries, territories or areas of geographical interest, and their
subdivisions, published as a list of CCs [CC-list] in ISO Standard
3166-1 [ISO3166-1].

The ICC and CC characters are coded according to ITU-T Recommendation
T.50 [T.50].

Together, the CC and the ICC form the ICC_Operator_ID as:

CC::ICC

3.1. Use of the ICC_Operator_ID

The ICC_Operator_ID is used as a replacement for the Global_ID as
specified in [RFC6370], i.e., its purpose is to provide a globally
unique context for other MPLS-TP identifiers.

As an example, an Interface Identifier (IF_ID) in [RFC6370] is
specified as the concatenation of the Node_ID (a unique 32-bit value
assigned by the operator) and the Interface Number (IF_Num, a 32-bit
unsigned integer assigned by the operator that is unique within the
scope of a Node_ID). To make this IF_ID globally unique, the
Global_ID is prefixed. This memo specifies the ICC_Operator_ID as an
alternative format that, just like the Global_ID, is prefixed to the
IF_ID. Using the notation from RFC 6370 [RFC6370]:

Global_ID::Node_ID::IF_Num

is functionally equivalent to:

ICC_Operator_ID::Node_ID::IF_Num

The same substitution procedure applies to all identifiers specified
in [RFC6370] with the exception of the MEG ID, MEP ID, and MIP ID.
MEG, MEP, and MIP Identifiers are redefined in this document (see
Sections 7.1, 7.2, and 7.3, respectively).

Winter, et al. Standards Track [Page 6]

RFC 6923 MPLS-TP ITU-T IDs May 2013

4. Node and Interface Identifiers

The format of the Node and Interface Identifiers are not changed by
this memo except for the case when global uniqueness is required.

[RFC6370] defines the Node Identifier (Node_ID) as a unique 32-bit
value assigned by the operator within the scope of a Global_ID. The
structure of the Node_ID itself is not defined as it is left to the
operator to choose an appropriate value. The value zero, however, is
reserved and MUST NOT be used.

This document does not change the above definition. However, in case
global uniqueness is required, the Node_ID is prefixed with the
ICC_Operator_ID as defined in Section 3.

[RFC6370] further defines interface numbers (IF_Num) as 32-bit
unsigned integers that can be freely assigned by the operator and
must be unique in the scope of the respective Node_ID. The IF_Num
value 0 has a special meaning, and therefore, it MUST NOT be used to
identify an MPLS-TP interface.

An Interface Identifier (IF_ID) identifies an interface uniquely
within the context of an ICC_Operator_ID. It is formed by
concatenating the Node_ID with the IF_Num to result in a 64-bit
identifier formed as Node_ID::IF_Num.

Global uniqueness of the IF_ID, if needed, can be assured by
prefixing the identifier with the ICC_Operator_ID.

5. MPLS-TP Tunnel and LSP Identifiers

This document does not change the definition for local Tunnel and LSP
IDs. When global uniqueness is needed, the format of these
identifiers is as described in Sections 5.1 and 5.2.

5.1. MPLS-TP Point-to-Point Tunnel Identifiers

Tunnel IDs (Tunnel_ID) are based on the end points' Node_IDs and
locally assigned tunnel numbers (Tunnel_Num), which identify the
tunnel at each end point. The tunnel number is a 16-bit unsigned
integer unique within the context of the Node_ID. A full Tunnel ID
is represented by the concatenation of these two end-point-specific
identifiers. Using the A1/Z9 convention, the format of a Tunnel_ID
is:

A1-{Node_ID::Tunnel_Num}::Z9-{Node_ID::Tunnel_Num}

Winter, et al. Standards Track [Page 7]

RFC 6923 MPLS-TP ITU-T IDs May 2013

Where global uniqueness is required, using ITU-T conventions, the
ICC_Operator_ID is prefixed to the Tunnel_ID. Thus, a globally
unique Tunnel_ID becomes:

A1-{ICC_Operator_ID::Node_ID::Tunnel_Num}::
Z9-{ICC_Operator_ID::Node_ID::Tunnel_Num}

As per [RFC6370], when an MPLS-TP tunnel is configured, it MUST be
assigned a unique IF_ID at each end point as defined in Section 4.

5.2. MPLS-TP LSP Identifiers

The following subsections define identifiers for MPLS-TP co-routed
bidirectional and associated bidirectional LSPs. Since MPLS-TP
Sub-Path Maintenance Entities (SPMEs) are also LSPs, they use the
same form of IDs.

5.2.1. MPLS-TP Co-Routed Bidirectional LSP Identifiers

The LSP Identifier (LSP_ID) for a co-routed bidirectional LSP is
formed by adding a 16-bit unsigned integer LSP number (LSP_Num) to
the Tunnel ID. Consequently, the format of an MPLS-TP co-routed
bidirectional LSP_ID is:

A1-{Node_ID::Tunnel_Num}::Z9-{Node_ID::Tunnel_Num}::LSP_Num

[RFC6370] notes that the "uniqueness of identifiers does not depend
on the A1/Z9 sort ordering".

A co-routed bidirectional LSP is provisioned or signaled as a single
entity, and therefore, a single LSP_Num is used for both
unidirectional LSPs. These can be referenced by the following
identifiers:

A1-Node_ID::A1-Tunnel_Num::LSP_Num::Z9-Node_ID and

Z9-Node_ID::Z9-Tunnel_Num::LSP_Num::A1-Node_ID, respectively.

Global uniqueness is accomplished by using globally unique Node_IDs.
A globally unique LSP_ID consequently becomes:

A1-{ICC_Operator_ID::Node_ID::Tunnel_Num}::
Z9-{ICC_Operator_ID::Node_ID::Tunnel_Num}::LSP_Num

Winter, et al. Standards Track [Page 8]

RFC 6923 MPLS-TP ITU-T IDs May 2013

5.2.2. MPLS-TP Associated Bidirectional LSP Identifiers

An associated bidirectional LSP needs a separate LSP_Num for both of
its unidirectional LSPs. The LSP number is again a 16-bit unsigned
integer that needs to be unique within the scope of the ingress's
Tunnel_Num. Consequently, the format of an MPLS-TP associated
bidirectional LSP_ID is:

A1-{Node_ID::Tunnel_Num::LSP_Num}::
Z9-{Node_ID::Tunnel_Num::LSP_Num}

Each of the unidirectional LSPs of which the associated bidirectional
LSP is composed may be referenced by one of the following
identifiers:

A1-Node_ID::A1-Tunnel_Num::A1-LSP_Num::Z9-Node_ID and

Z9-Node_ID::Z9-Tunnel_Num::Z9-LSP_Num::A1-Node_ID, respectively.

A globally unique LSP_ID is constructed using the globally unique
Node_IDs as defined before. Consequently, a globally unique LSP_ID
is formulated as:

A1-{ICC_Operator_ID::Node_ID::Tunnel_Num::LSP_Num}::
Z9-{ICC_Operator_ID::Node_ID::Tunnel_Num::LSP_Num}

6. Pseudowire Path Identifiers

The PW Path Identifier (PW_Path_ID) is structured in a similar manner
as the PW_Path_ID described in Section 6 of [RFC6370]. Instead of
the Global_ID used in [RFC6370], this document uses the
ICC_Operator_ID to make the PW_Path_ID globally unique. In this
document, the Attachment Individual Identifier (AII) is composed of
three fields. These are the ICC_Operator_ID, the Node_ID, and the
AC_ID. The AC_ID is as defined in [RFC5003]. The complete globally
unique PW_Path_ID is formulated as:

A1-{ICC_Operator_ID::Node_ID::AC_ID}::
Z9-{ICC_Operator_ID::Node_ID::AC_ID}

7. Maintenance Identifiers

The following subsections define the identifiers for the various
maintenance-related groups and entities as defined in [RFC6371]. In
contrast to the IDs defined in [RFC6370], this document does not
define separate maintenance identifiers for Sections, PWs, and LSPs.

Winter, et al. Standards Track [Page 9]

RFC 6923 MPLS-TP ITU-T IDs May 2013

7.1. MEG Identifiers

MEG_IDs for MPLS-TP Sections, LSPs, and PWs following ITU-T
conventions are based on the globally unique ICC_Operator_ID. In
this case, the MEG_ID is a string of up to 15 characters and consists
of three subfields: the Country Code (as described in Section 3) and
the ICC (as described in Section 3) -- which together form the
ICC_Operator_ID -- followed by a Unique MEG ID Code (UMC) as defined
in [Y.1731_cor1].

The resulting MEG_ID is:

CC::ICC::UMC

To avoid the potential for the concatenation of a short (i.e., less
than 6 characters) ICC with a UMC not being unique, the UMC MUST
start with the "/" character, which is not allowed in the ICC itself.
This way, the MEG_ID can also be easily decomposed into its
individual components by a receiver.

The UMC MUST be unique within the organization identified by the
combination of CC and ICC.

The ICC_Operator_ID-based MEG_ID may be applied equally to a single
MPLS-TP Section, LSP, or Pseudowire.

7.2. MEP Identifiers

ICC_Operator_ID-based MEP_IDs for MPLS-TP Sections, LSPs, and
Pseudowires are formed by appending a 16-bit index to the MEG_ID
defined in Section 7.1. Within the context of a particular MEG, we
call the identifier associated with a MEP the MEP Index (MEP_Index).
The MEP_Index is administratively assigned. It is encoded as a
16-bit unsigned integer and MUST be unique within the MEG. An
ICC_Operator_ID-based MEP_ID is structured as:

MEG_ID::MEP_Index

An ICC_Operator_ID-based MEP ID is globally unique by construction
given the ICC_Operator_ID-based MEG_ID's global uniqueness.

7.3. MIP Identifiers

ICC_Operator_ID-based MIP_IDs for MPLS-TP Sections, LSPs, and
Pseudowires are formed by a global IF_ID that is obtained by
prefixing the identifier of the interface on which the MIP resides

Winter, et al. Standards Track [Page 10]

RFC 6923 MPLS-TP ITU-T IDs May 2013

with the ICC_Operator_ID as described in Section 3.1. This allows
MIPs to be independently identified in nodes where a per-interface
MIP model is used.

If only a per-node MIP model is used, one MIP is configured. In this
case, the MIP_ID is formed by using the Node_ID and an IF_Num of 0.

8. Security Considerations

This document extends an existing naming scheme and does not
introduce new security concerns. However, as mentioned in the
Security Considerations section of [RFC6370], protocol specifications
that describe the use of this naming scheme may introduce security
risks and concerns about authentication of participants. For this
reason, these protocol specifications need to describe security and
authentication concerns that may be raised by the particular
mechanisms defined and how those concerns may be addressed.

9. References

9.1. Normative References

[ISO3166-1] "Codes for the representation of names of countries and
their subdivisions -- Part 1: Country codes", ISO
3166-1, 2006.

[M1400] "Designations for interconnections among operators'
networks", ITU-T Recommendation M.1400, July 2006.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC5003] Metz, C., Martini, L., Balus, F., and J. Sugimoto,
"Attachment Individual Identifier (AII) Types for
Aggregation", RFC 5003, September 2007.

[RFC6370] Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
Profile (MPLS-TP) Identifiers", RFC 6370, September
2011.

[T.50] "International Reference Alphabet (IRA) (Formerly
International Alphabet No. 5 or IA5) - Information
technology - 7-bit coded character set for information
exchange", ITU-T Recommendation T.50, September 1992.

[Y.1731_cor1] "OAM functions and mechanisms for Ethernet based
networks - Corrigendum 1", ITU-T Recommendation
G.8013/Y.1731 Corrigendum 1, October 2011.

Winter, et al. Standards Track [Page 11]

RFC 6923 MPLS-TP ITU-T IDs May 2013

9.2. Informative References

[CC-list] "List of Country Codes - ISO 3166 (CCs)",
<http://www.iso.org/iso/country_codes.htm>.

[ICC-list] "List of ITU Carrier Codes (ICCs)",
<http://www.itu.int/oth/T0201>.

[RFC6371] Busi, I., Ed., and D. Allan, Ed., "Operations,
Administration, and Maintenance Framework for MPLS-
Based Transport Networks", RFC 6371, September 2011.

Authors' Addresses

Rolf Winter
NEC

EMail: [email protected]

Eric Gray
Ericsson

EMail: [email protected]

Huub van Helvoort
Huawei Technologies Co., Ltd.

EMail: [email protected]

Malcolm Betts
ZTE

EMail: [email protected]

Winter, et al. Standards Track [Page 12]