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IETF RFC 6370
Last modified on Wednesday, September 21st, 2011
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Internet Engineering Task Force (IETF) M. Bocci
Request for Comments: 6370 Alcatel-Lucent
Category: Standards Track G. Swallow
ISSN: 2070-1721 Cisco
E. Gray
Ericsson
September 2011
MPLS Transport Profile (MPLS-TP) Identifiers
 Abstract
This document specifies an initial set of identifiers to be used in
the Transport Profile of Multiprotocol Label Switching (MPLS-TP).
The MPLS-TP requirements (RFC 5654) require that the elements and
objects in an MPLS-TP environment are able to be configured and
managed without a control plane. In such an environment, many
conventions for defining identifiers are possible. This document
defines identifiers for MPLS-TP management and Operations,
Administration, and Maintenance (OAM) functions compatible with IP/
MPLS conventions.
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and Pseudowire Emulation Edge-to-Edge
(PWE3) architectures to support the capabilities and functionalities
of a packet transport network as defined by the 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/RFC 6370.
Bocci, et al. Standards Track PAGE 1 
RFC 6370 MPLS-TP Identifiers September 2011
Copyright Notice
Copyright (c) 2011 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 ....................................................3
1.1. Terminology ................................................3
1.2. Requirements Language ......................................4
1.3. Notational Conventions .....................................4
2. Named Entities ..................................................5
3. Uniquely Identifying an Operator - the Global_ID ................5
4. Node and Interface Identifiers ..................................6
5. MPLS-TP Tunnel and LSP Identifiers ..............................7
5.1. MPLS-TP Point-to-Point Tunnel Identifiers ..................8
5.2. MPLS-TP LSP Identifiers ....................................9
5.2.1. MPLS-TP Co-Routed Bidirectional LSP Identifiers .....9
5.2.2. MPLS-TP Associated Bidirectional LSP Identifiers ....9
5.3. Mapping to RSVP Signaling .................................10
6. Pseudowire Path Identifiers ....................................11
7. Maintenance Identifiers ........................................13
7.1. Maintenance Entity Group Identifiers ......................13
7.1.1. MPLS-TP Section MEG_IDs ............................13
7.1.2. MPLS-TP LSP MEG_IDs ................................13
7.1.3. Pseudowire MEG_IDs .................................14
7.2. Maintenance Entity Group End Point Identifiers ............14
7.2.1. MPLS-TP Section MEP_IDs ............................14
7.2.2. MPLS-TP LSP_MEP_ID .................................15
7.2.3. MEP_IDs for Pseudowires ............................15
7.3. Maintenance Entity Group Intermediate Point Identifiers ...15
8. Security Considerations ........................................15
9. References .....................................................16
9.1. Normative References ......................................16
9.2. Informative References ....................................17
Bocci, et al. Standards Track PAGE 2
RFC 6370 MPLS-TP Identifiers September 2011
1. Introduction
This document specifies an initial set of identifiers to be used in
the Transport Profile of Multiprotocol Label Switching (MPLS-TP).
The MPLS-TP requirements (RFC 5654 [7]) require that the elements and
objects in an MPLS-TP environment are able to be configured and
managed without a control plane. In such an environment, many
conventions for defining identifiers are possible. This document
defines identifiers for MPLS-TP management and OAM functions
compatible with IP/MPLS conventions. That is, the identifiers have
been chosen to be compatible with existing IP, MPLS, GMPLS, and
Pseudowire definitions.
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and Pseudowire Emulation Edge-to-Edge
(PWE3) architectures to support the capabilities and functionalities
of a packet transport network as defined by the ITU-T.
1.1. Terminology
AGI: Attachment Group Identifier
AII: Attachment Interface Identifier
AS: Autonomous System
ASN: Autonomous System Number
EGP: Exterior Gateway Protocol
FEC: Forwarding Equivalence Class
GMPLS: Generalized Multiprotocol Label Switching
IGP: Interior Gateway Protocol
LSP: Label Switched Path
LSR: Label Switching Router
MEG: Maintenance Entity Group
MEP: Maintenance Entity Group End Point
MIP: Maintenance Entity Group Intermediate Point
Bocci, et al. Standards Track PAGE 3
RFC 6370 MPLS-TP Identifiers September 2011
MPLS: Multiprotocol Label Switching
NNI: Network-to-Network Interface
OAM: Operations, Administration, and Maintenance
PW: Pseudowire
RSVP: Resource Reservation Protocol
RSVP-TE: RSVP Traffic Engineering
SAII: Source AII
SPME: Sub-Path Maintenance Entity
T-PE: Terminating Provider Edge
TAII: Target AII
1.2. Requirements Language
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 RFC 2119 [1].
1.3. Notational Conventions
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
Bocci, et al. Standards Track PAGE 4
RFC 6370 MPLS-TP Identifiers September 2011
is not intended to constrain protocol designs by dictating a
particular field sequence (for example, see Section 5.2.1) or even
what fields appear in which objects (for example, see Section 5.3).
2. Named Entities
In order to configure, operate, and manage a transport network based
on the MPLS Transport Profile, a number of entities require
identification. Identifiers for the following entities are defined
in this document:
* Global_ID
* Node
* Interface
* Tunnel
* LSP
* PW
* MEG
* MEP
* MIP
Note that we have borrowed the term "tunnel" from RSVP-TE (RFC 3209
[2]) where it is used to describe an entity that provides a logical
association between a source and destination LSR. The tunnel, in
turn, is instantiated by one or more LSPs, where the additional LSPs
are used for protection or re-grooming of the tunnel.
3. Uniquely Identifying an Operator - the Global_ID
The Global_ID is defined to uniquely identify an operator. RFC 5003
[3] defines a globally unique Attachment Interface Identifier (AII).
That AII is composed of three parts: a Global_ID that uniquely
identifies an operator, a prefix, and, finally, an attachment circuit
identifier. We have chosen to use that Global ID for MPLS-TP.
Quoting from RFC 5003, Section 3.2:
The global ID can contain the 2-octet or 4-octet value of the
provider's Autonomous System Number (ASN). It is expected that
the global ID will be derived from the globally unique ASN of the
Bocci, et al. Standards Track PAGE 5
RFC 6370 MPLS-TP Identifiers September 2011
autonomous system hosting the PEs containing the actual AIIs. The
presence of a global ID based on the operator's ASN ensures that
the AII will be globally unique.
A Global_ID is an unsigned 32-bit value and MUST be derived from a
4-octet AS number assigned to the operator. Note that 2-octet AS
numbers have been incorporated in the 4-octet by placing the 2-octet
AS number in the low-order octets and setting the two high-order
octets to zero.
ASN 0 is reserved and cannot be assigned to an operator. An
identifier containing a Global_ID of zero means that no Global_ID is
specified. Note that a Global_ID of zero is limited to entities
contained within a single operator and MUST NOT be used across an
NNI.
The Global_ID is used solely to provide a globally unique context for
other MPLS-TP identifiers. While the AS number used in the Global_ID
MUST be one that the operator is entitled to use, the use of the
Global_ID is not related to the use of the ASN in protocols such as
BGP.
4. Node and Interface Identifiers
An LSR requires identification of the node itself and of its
interfaces. An interface is the attachment point to a server
(sub-)layer, e.g., MPLS-TP section or MPLS-TP tunnel.
We call the identifier associated with a node a "Node Identifier"
(Node_ID). The Node_ID is a unique 32-bit value assigned by the
operator within the scope of a Global_ID. The structure of the
Node_ID is operator-specific and is outside the scope of this
document. However, the value zero is reserved and MUST NOT be used.
Where IPv4 addresses are used, it may be convenient to use the Node's
IPv4 loopback address as the Node_ID; however, the Node_ID does not
need to have any association with the IPv4 address space used in the
operator's IGP or EGP. Where IPv6 addresses are used exclusively, a
32-bit value unique within the scope of a Global_ID is assigned.
An LSR can support multiple layers (e.g., hierarchical LSPs) and the
Node_ID belongs to the multiple-layer context, i.e., it is applicable
to all LSPs or PWs that originate on, have an intermediate point on,
or terminate on the node.
In situations where a Node_ID needs to be globally unique, this is
accomplished by prefixing the identifier with the operator's
Global_ID.
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RFC 6370 MPLS-TP Identifiers September 2011
The term "interface" is used for the attachment point to an MPLS-TP
section. Within the context of a particular node, we call the
identifier associated with an interface an "Interface Number"
(IF_Num). The IF_Num is a 32-bit unsigned integer assigned by the
operator and MUST be unique within the scope of a Node_ID. The
IF_Num value 0 has special meaning (see Section 7.3, MIP Identifiers)
and MUST NOT be used to identify an MPLS-TP interface.
Note that IF_Num has no relation with the ifNum object defined in RFC
2863 [8]. Further, no mapping is mandated between IF_Num and ifIndex
in RFC 2863.
An "Interface Identifier" (IF_ID) identifies an interface uniquely
within the context of a Global_ID. It is formed by concatenating the
Node_ID with the IF_Num. That is, an IF_ID is a 64-bit identifier
formed as Node_ID::IF_Num.
This convention was chosen to allow compatibility with GMPLS. The
GMPLS signaling functional description [4] requires interface
identification. GMPLS allows three formats for the Interface_ID.
The third format consists of an IPv4 address plus a 32-bit unsigned
integer for the specific interface. The format defined for MPLS-TP
is consistent with this format, but uses the Node_ID instead of an
IPv4 address.
If an IF_ID needs to be globally unique, this is accomplished by
prefixing the identifier with the operator's Global_ID.
Note that MPLS-TP supports hierarchical sections. The attachment
point to an MPLS-TP section at any (sub-)layer requires a node-unique
IF_Num.
5. MPLS-TP Tunnel and LSP Identifiers
In MPLS, the actual transport of packets is provided by Label
Switched Paths (LSPs). A transport service may be composed of
multiple LSPs. Further, the LSPs providing a service may change over
time due to protection and restoration events. In order to clearly
identify the service, we use the term "MPLS-TP Tunnel" or simply
"tunnel" for a service provided by (for example) a working LSP and
protected by a protection LSP. The "Tunnel Identifier" (Tunnel_ID)
identifies the transport service and provides a stable binding to the
client in the face of changes in the data-plane LSPs used to provide
the service due to protection or restoration events. This section
defines an MPLS-TP Tunnel_ID to uniquely identify a tunnel, and an
MPLS-TP LSP Identifier (LSP_ID) to uniquely identify an LSP
associated with a tunnel.
Bocci, et al. Standards Track PAGE 7
RFC 6370 MPLS-TP Identifiers September 2011
For the case where multiple LSPs (for example) are used to support a
single service with a common set of end points, using the Tunnel_ID
allows for a trivial mapping between the server and client layers,
providing a common service identifier that may be either defined by
or used by the client.
Note that this usage is not intended to constrain protection schemes,
and may be used to identify any service (protected or unprotected)
that may appear to the client as a single service attachment point.
Keeping the Tunnel_ID consistent across working and protection LSPs
is a useful construct currently employed within GMPLS. However, the
Tunnel_ID for a protection LSP MAY differ from that used by its
corresponding working LSP.
5.1. MPLS-TP Point-to-Point Tunnel Identifiers
At each end point, a tunnel is uniquely identified by the end point's
Node_ID and a locally assigned tunnel number. Specifically, a
"Tunnel Number" (Tunnel_Num) is a 16-bit unsigned integer unique
within the context of the Node_ID. The motivation for each end point
having its own tunnel number is to allow a compact form for the
MEP_ID. See Section 7.2.2.
Having two tunnel numbers also serves to simplify other signaling
(e.g., setup of associated bidirectional tunnels as described in
Section 5.3).
The concatenation of the two end point identifiers serves as the full
identifier. Using the A1/Z9 convention, the format of a Tunnel_ID
is:
A1-{Node_ID::Tunnel_Num}::Z9-{Node_ID::Tunnel_Num}
Where the Tunnel_ID needs to be globally unique, this is accomplished
by using globally unique Node_IDs as defined above. Thus, a globally
unique Tunnel_ID becomes:
A1-{Global_ID::Node_ID::Tunnel_Num}::Z9-{Global_ID::Node_ID::
Tunnel_Num}
When an MPLS-TP Tunnel is configured, it MUST be assigned a unique
IF_ID at each end point. As usual, the IF_ID is composed of the
local Node_ID concatenated with a 32-bit IF_Num.
Bocci, et al. Standards Track PAGE 8
RFC 6370 MPLS-TP Identifiers September 2011
5.2. MPLS-TP LSP Identifiers
This section defines identifiers for MPLS-TP co-routed bidirectional
and associated bidirectional LSPs. Note that MPLS-TP Sub-Path
Maintenance Entities (SPMEs), as defined in RFC 5921 [9], are also
LSPs and use these same forms of identifiers.
5.2.1. MPLS-TP Co-Routed Bidirectional LSP Identifiers
A co-routed bidirectional LSP can be uniquely identified by a single
LSP number within the scope of an MPLS-TP Tunnel_ID. Specifically,
an LSP Number (LSP_Num) is a 16-bit unsigned integer unique within
the Tunnel_ID. Thus, the format of an MPLS-TP co-routed
bidirectional LSP_ID is:
A1-{Node_ID::Tunnel_Num}::Z9-{Node_ID::Tunnel_Num}::LSP_Num
Note that the uniqueness of identifiers does not depend on the A1/Z9
sort ordering. Thus, the identifier:
Z9-{Node_ID::Tunnel_Num}::A1-{Node_ID::Tunnel_Num}::LSP_Num
is synonymous with the one above.
At the data-plane level, a co-routed bidirectional LSP is composed of
two unidirectional LSPs traversing the same links in opposite
directions. Since a co-routed bidirectional LSP is provisioned or
signaled as a single entity, a single LSP_Num is used for both
unidirectional LSPs. The unidirectional LSPs can be referenced by
the 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.
Where the LSP_ID needs to be globally unique, this is accomplished by
using globally unique Node_IDs as defined above. Thus, a globally
unique LSP_ID becomes:
A1-{Global_ID::Node_ID::Tunnel_Num}::Z9-{Global_ID::
Node_ID::Tunnel_Num}::LSP_Num
5.2.2. MPLS-TP Associated Bidirectional LSP Identifiers
For an associated bidirectional LSP, each of the unidirectional LSPs
from A1 to Z9 and Z9 to A1 require LSP_Nums. Each unidirectional LSP
is uniquely identified by a single LSP number within the scope of the
ingress's Tunnel_Num. Specifically, an "LSP Number" (LSP_Num) is a
Bocci, et al. Standards Track PAGE 9
RFC 6370 MPLS-TP Identifiers September 2011
16-bit unsigned integer unique within the scope of the ingress's
Tunnel_Num. Thus, 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}
At the data-plane level, an associated bidirectional LSP is composed
of two unidirectional LSPs between two nodes in opposite directions.
The unidirectional LSPs may be referenced by the 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.
Where the LSP_ID needs to be globally unique, this is accomplished by
using globally unique Node_IDs as defined above. Thus, a globally
unique LSP_ID becomes:
A1-{Global_ID::Node_ID::Tunnel_Num::LSP_Num}::
Z9-{Global_ID::Node_ID::Tunnel_Num::LSP_Num}
5.3. Mapping to RSVP Signaling
This section is informative and exists to help understand the
structure of the LSP IDs.
GMPLS [5] is based on RSVP-TE [2]. This section defines the mapping
from an MPLS-TP LSP_ID to RSVP-TE. At this time, RSVP-TE has yet to
be extended to accommodate Global_IDs. Thus, a mapping is only made
for the network unique form of the LSP_ID and assumes that the
operator has chosen to derive its Node_IDs from valid IPv4 addresses.
GMPLS and RSVP-TE signaling use a 5-tuple to uniquely identify an LSP
within an operator's network. This tuple is composed of a Tunnel
End-point Address, Tunnel_ID, Extended Tunnel ID, Tunnel Sender
Address, and (RSVP) LSP_ID. RFC 3209 allows some flexibility in how
the Extended Tunnel ID is chosen, and a direct mapping is not
mandated. One convention that is often used, however, is to populate
this field with the same value as the Tunnel Sender Address. The
examples below follow that convention. Note that these are only
examples.
Bocci, et al. Standards Track PAGE 10
RFC 6370 MPLS-TP Identifiers September 2011
For a co-routed bidirectional LSP signaled from A1 to Z9, the mapping
to the GMPLS 5-tuple is as follows:
* Tunnel End-point Address = Z9-Node_ID
* Tunnel_ID = A1-Tunnel_Num
* Extended Tunnel_ID = A1-Node_ID
* Tunnel Sender Address = A1-Node_ID
* (RSVP) LSP_ID = LSP_Num
An associated bidirectional LSP between two nodes A1 and Z9 consists
of two unidirectional LSPs, one from A1 to Z9 and one from Z9 to A1.
In situations where a mapping to the RSVP-TE 5-tuples is required,
the following mappings are used. For the A1 to Z9 LSP, the mapping
would be:
* Tunnel End-point Address = Z9-Node_ID
* Tunnel_ID = A1-Tunnel_Num
* Extended Tunnel_ID = A1-Node_ID
* Tunnel Sender Address = A1-Node_ID
* (RSVP) LSP_ID = A1-LSP_Num
Likewise, the Z9 to A1 LSP, the mapping would be:
* Tunnel End-point Address = A1-Node_ID
* Tunnel_ID = Z9-Tunnel_Num
* Extended Tunnel_ID = Z9-Node_ID
* Tunnel Sender Address = Z9-Node_ID
* (RSVP) LSP_ID = Z9-LSP_Num
6. Pseudowire Path Identifiers
Pseudowire signaling (RFC 4447 [6]) defines two FECs used to signal
pseudowires. Of these, the Generalized PWid FEC (type 129) along
with AII Type 2 as defined in RFC 5003 [3] fits the identification
requirements of MPLS-TP.
Bocci, et al. Standards Track PAGE 11
RFC 6370 MPLS-TP Identifiers September 2011
In an MPLS-TP environment, a PW is identified by a set of identifiers
that can be mapped directly to the elements required by the
Generalized PWid FEC (type 129) and AII Type 2. To distinguish this
identifier from other Pseudowire Identifiers, we call this a
Pseudowire Path Identifier (PW_Path_ID).
The AII Type 2 is composed of three fields. These are the Global_ID,
the Prefix, and the AC_ID. The Global_ID used in this document is
identical to the Global_ID defined in RFC 5003. The Node_ID is used
as the Prefix. The AC_ID is as defined in RFC 5003.
To complete the Generalized PWid FEC (type 129), all that is required
is an Attachment Group Identifier (AGI). That field is exactly as
specified in RFC 4447. A (bidirectional) pseudowire consists of a
pair of unidirectional LSPs, one in each direction. Thus, for
signaling, the Generalized PWid FEC (type 129) has a notion of Source
AII (SAII) and Target AII (TAII). These terms are used relative to
the direction of the LSP, i.e., the SAII is assigned to the end that
allocates the PW label for a given direction, and the TAII to the
other end.
In a purely configured environment, when referring to the entire PW,
this distinction is not critical. That is, a Generalized PWid FEC
(type 129) of AGIa::AIIb::AIIc is equivalent to AGIa::AIIc::AIIb.
We note that in a signaled environment, the required convention in
RFC 4447 is that at a particular end point, the AII associated with
that end point comes first. The complete PW_Path_ID is:
AGI::A1-{Global_ID::Node_ID::AC_ID}::
Z9-{Global_ID::Node_ID::AC_ID}.
In a signaled environment the LSP from A1 to Z9 would be initiated
with a label request from A1 to Z9 with the fields of the Generalized
PWid FEC (type 129) completed as follows:
AGI = AGI
SAII = A1-{Global_ID::Node_ID::AC_ID}
TAII = Z9-{Global_ID::Node_ID::AC_ID}
The LSP from Z9 to A1 would signaled with:
AGI = AGI
SAII = Z9-{Global_ID::Node_ID::AC_ID}
TAII = A1-{Global_ID::Node_ID::AC_ID}
Bocci, et al. Standards Track PAGE 12
RFC 6370 MPLS-TP Identifiers September 2011
7. Maintenance Identifiers
In MPLS-TP, a Maintenance Entity Group (MEG) represents an entity
that requires management and defines a relationship between a set of
maintenance points. A maintenance point is either a Maintenance
Entity Group End Point (MEP), a Maintenance Entity Group Intermediate
Point (MIP), or a Pseudowire Segment End Point. Within the context
of a MEG, MEPs and MIPs must be uniquely identified. This section
defines a means of uniquely identifying Maintenance Entity Groups and
Maintenance Entities. It also uniquely defines MEPs and MIPs within
the context of a Maintenance Entity Group.
7.1. Maintenance Entity Group Identifiers
Maintenance Entity Group Identifiers (MEG_IDs) are required for
MPLS-TP sections, LSPs, and Pseudowires. The formats were chosen to
follow the IP-compatible identifiers defined above.
7.1.1. MPLS-TP Section MEG_IDs
MPLS-TP allows a hierarchy of sections. See "MPLS-TP Data Plane
Architecture" (RFC 5960 [10]). Sections above layer 0 are MPLS-TP
LSPs. These use their MPLS-TP LSP MEG IDs defined in Section 7.1.2.
IP-compatible MEG_IDs for MPLS-TP sections at layer 0 are formed by
concatenating the two IF_IDs of the corresponding section using the
A1/Z9 ordering. For example:
A1-IF_ID::Z9-IF_ID
Where the Section_MEG_ID needs to be globally unique, this is
accomplished by using globally unique Node_IDs as defined above.
Thus, a globally unique Section_MEG_ID becomes:
A1-{Global_ID::IF_ID}::Z9-{Global_ID::IF_ID}
7.1.2. MPLS-TP LSP MEG_IDs
A MEG pertains to a unique MPLS-TP LSP. IP compatible MEG_IDs for
MPLS-TP LSPs are simply the corresponding LSP_IDs; however, the A1/Z9
ordering MUST be used. For bidirectional co-routed LSPs, the format
of the LSP_ID is found in Section 5.2.1. For associated
bidirectional LSPs, the format is in Section 5.2.2.
Bocci, et al. Standards Track PAGE 13
RFC 6370 MPLS-TP Identifiers September 2011
We note that while the two identifiers are syntactically identical,
they have different semantics. This semantic difference needs to be
made clear. For instance, if both an MPLS-TP LSP_ID and MPLS-TP LSP
MEG_IDs are to be encoded in TLVs, different types need to be
assigned for these two identifiers.
7.1.3. Pseudowire MEG_IDs
For Pseudowires, a MEG pertains to a single PW. The IP-compatible
MEG_ID for a PW is simply the corresponding PW_Path_ID; however, the
A1/Z9 ordering MUST be used. The PW_Path_ID is described in
Section 6. We note that while the two identifiers are syntactically
identical, they have different semantics. This semantic difference
needs to be made clear. For instance, if both a PW_Path_ID and a
PW_MEG_ID are to be encoded in TLVs, different types need to be
assigned for these two identifiers.
7.2. Maintenance Entity Group End Point Identifiers
7.2.1. MPLS-TP Section MEP_IDs
IP-compatible MEP_IDs for MPLS-TP sections above layer 0 are their
MPLS-TP LSP_MEP_IDs. See Section 7.2.2.
IP-compatible MEP_IDs for MPLS-TP sections at layer 0 are simply the
IF_IDs of each end of the section. For example, for a section whose
MEG_ID is:
A1-IF_ID::Z9-IF_ID
the Section MEP_ID at A1 would be:
A1-IF_ID
and the Section MEP_ID at Z9 would be:
Z9-IF_ID.
Where the Section MEP_ID needs to be globally unique, this is
accomplished by using globally unique Node_IDs as defined above.
Thus, a globally unique Section MEP_ID becomes:
Global_ID::IF_ID.
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RFC 6370 MPLS-TP Identifiers September 2011
7.2.2. MPLS-TP LSP_MEP_ID
In order to automatically generate MEP_IDs for MPLS-TP LSPs, we use
the elements of identification that are unique to an end point. This
ensures that MEP_IDs are unique for all LSPs within an operator.
When Tunnels or LSPs cross operator boundaries, these are made unique
by pre-pending them with the operator's Global_ID.
The MPLS-TP LSP_MEP_ID is:
Node_ID::Tunnel_Num::LSP_Num
where the Node_ID is the node in which the MEP is located and
Tunnel_Num is the tunnel number unique to that node. In the case of
co-routed bidirectional LSPs, the single LSP_Num is used at both
ends. In the case of associated bidirectional LSPs, the LSP_Num is
the one unique to where the MEP resides.
In situations where global uniqueness is required, this becomes:
Global_ID::Node_ID::Tunnel_Num::LSP_Num
7.2.3. MEP_IDs for Pseudowires
Like MPLS-TP LSPs, Pseudowire end points (T-PEs) require MEP_IDs. In
order to automatically generate MEP_IDs for PWs, we simply use the
AGI plus the AII associated with that end of the PW. Thus, a MEP_ID
for a Pseudowire T-PE takes the form:
AGI::Global_ID::Node_ID::AC_ID
where the Node_ID is the node in which the MEP is located and the
AC_ID is the AC_ID of the Pseudowire at that node.
7.3. Maintenance Entity Group Intermediate Point Identifiers
For a MIP that is associated with a particular interface, we simply
use the IF_ID (see Section 4) of the interfaces that are cross-
connected. This allows MIPs to be independently identified in one
node where a per-interface MIP model is used. If only a per-node MIP
model is used, then one MIP is configured. In this case, the MIP_ID
is formed using the Node_ID and an IF_Num of 0.
8. Security Considerations
This document describes an information model and, as such, does not
introduce security concerns. Protocol specifications that describe
use of this information model, however, may introduce security risks
Bocci, et al. Standards Track PAGE 15
RFC 6370 MPLS-TP Identifiers September 2011
and concerns about authentication of participants. For this reason,
the writers of protocol specifications for the purpose of describing
implementation of this information model need to describe security
and authentication concerns that may be raised by the particular
mechanisms defined and how those concerns may be addressed.
Uniqueness of the identifiers from this document is guaranteed by the
assigner (e.g., a Global_ID is unique based on the assignment of ASNs
from IANA and both a Node_ID and an IF_Num are unique based on the
assignment by an operator). Failure by an assigner to use unique
values within the specified scoping for any of the identifiers
defined herein could result in operational problems. For example, a
non-unique MEP value could result in failure to detect a mis-merged
LSP.
Protocol specifications that utilize the identifiers defined herein
need to consider the implications of guessable identifiers and, where
there is a security implication, SHOULD give advice on how to make
identifiers less guessable.
9. References
9.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and
G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels",
RFC 3209, December 2001.
[3] Metz, C., Martini, L., Balus, F., and J. Sugimoto, "Attachment
Individual Identifier (AII) Types for Aggregation", RFC 5003,
September 2007.
[4] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS)
Signaling Functional Description", RFC 3471, January 2003.
[5] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS)
Signaling Resource ReserVation Protocol-Traffic Engineering
(RSVP-TE) Extensions", RFC 3473, January 2003.
[6] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. Heron,
"Pseudowire Setup and Maintenance Using the Label Distribution
Protocol (LDP)", RFC 4447, April 2006.
Bocci, et al. Standards Track PAGE 16
RFC 6370 MPLS-TP Identifiers September 2011
9.2. Informative References
[7] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and
S. Ueno, "Requirements of an MPLS Transport Profile", RFC 5654,
September 2009.
[8] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB",
RFC 2863, June 2000.
[9] Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, "A
Framework for MPLS in Transport Networks", RFC 5921, July 2010.
[10] Frost, D., Bryant, S., and M. Bocci, "MPLS Transport Profile
Data Plane Architecture", RFC 5960, August 2010.
Authors' Addresses
Matthew Bocci
Alcatel-Lucent
Voyager Place, Shoppenhangers Road
Maidenhead, Berks SL6 2PJ
UK
EMail: matthew.bocci@alcatel-lucent.com
George Swallow
Cisco
EMail: swallow@cisco.com
Eric Gray
Ericsson
900 Chelmsford Street
Lowell, Massachussetts 01851-8100
EMail: eric.gray@ericsson.com
Bocci, et al. Standards Track PAGE 17
RFC TOTAL SIZE: 35294 bytes
PUBLICATION DATE: Wednesday, September 21st, 2011
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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