MPLS Working Group M. Bocci
Internet-Draft Alcatel-Lucent
Intended status: Standards Track G. Swallow
Expires: January 14, 2010 Cisco
July 13, 2009
MPLS-TP Identifiers
draft-swallow-mpls-tp-identifiers-01
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Abstract
This document specifies identifiers for MPLS-TP objects. Included
are identifiers conformant to existing ITU conventions and
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identifiers which are compatible with existing IP, MPLS, GMPLS, and
Pseudowire definitions.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Named Entities . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Uniquely Identifying an Operator . . . . . . . . . . . . . . . 5
3.1. The Global ID . . . . . . . . . . . . . . . . . . . . . . 5
3.2. ITU Carrier Code . . . . . . . . . . . . . . . . . . . . . 5
4. Node and Interface Identifiers . . . . . . . . . . . . . . . . 6
5. Path Identifiers . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. MPLS-TP LSP Identifiers . . . . . . . . . . . . . . . . . 7
5.2. Pseudowire Identifiers . . . . . . . . . . . . . . . . . . 8
6. Maintenance Identifiers . . . . . . . . . . . . . . . . . . . 8
6.1. Maintenance Entity Identifiers . . . . . . . . . . . . . . 8
6.1.1. IP Compatible ME-IDs . . . . . . . . . . . . . . . . . 9
6.1.2. ICC based ME-IDs . . . . . . . . . . . . . . . . . . . 9
6.2. Maintenance Points . . . . . . . . . . . . . . . . . . . . 9
6.3. MEP_IDs for MPLS-TP LSPs and Tunnels . . . . . . . . . . . 9
6.4. MEP_IDs for Pseudowires . . . . . . . . . . . . . . . . . 10
6.5. Maintenance Intermediate Point Identifiers . . . . . . . . 10
7. Open issues . . . . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
This document specifies identifiers to be used in within the
Transport Profile of Multiprotocol Label Switching (MPLS-TP). where
compatibility with existing MPLS control plane conventions are
necessary. The MPLS-TP requirements [13] 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. In particular,
identifiers conformat to existing ITU conventions are defined. It is
also anticipated that operational environments where MPLS-TP objects,
e.g. Label Switched Paths (LSPs) and Pseudowires (PWs) will be
signaled via existing protocols such as the Label Distribution
Protocol (RFC 4447) [1] and the Resource Reservation Protocol as it
is applied to Generalized Multi-protocol Label Switching (RFCs 3471 &
3473) [2][3] (GMPLS). This document defines a set of identifiers for
MPLS-TP which are both compatible with those protocols and applicable
to MPLS-TP management and OAM functions.
1.1. Terminology
AII: Attachment Interface Identifier
ASN: Autonomous System Number
FEC: Forwarding Equivalence Class
GMPLS: Generalised Multi-Protocol Label Switching
ICC: ITU Carrier Code
LSP: Label Switched Path
LSR: Label Switching Router
ME: Maintenance Entity
MEP: Maintenance End Point
MIP: Maintenance Intermediate Point
MPLS: Multi-Protocol Label Switching
OAM: Operations, Administration and Maintenance
P2MP: Point to Multi-Point
P2P: Point to Point
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PSC: Protection State Coordination
PW: Pseudowire
RSVP: Resource Reservation Protocol
RSVP-TE: RSVP Traffic Engineering
S-PE: Switching Provider Edge
T-PE: Terminating Provider Edge
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 [4].
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 follow entities are defined in
this document:
o Operator
* ICC
* Global-ID
o LSR
o LSP
o PW
o Interface
o MEG
o MEP
o MIP
o Tunnel
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Note that we have borrowed the term tunnel from RSVP-TE (RFC 3209)
[5] where it is used to describe an entity that provides an LSP
connection between a source and destination LSR which 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
Two forms of identification are defined, one that is compatible with
IP operational practice called a Global_ID and one compatible with
ITU practice, the ICC. An Operator MAY be identified either by its
Global_ID or by its ICC.
3.1. The Global ID
RFC 5003 [6] defines a globally unique Attachment Interface
Identifier (AII). That AII is composed of three parts, a Global ID
which uniquely identifies a operator, a prefix, and finally and
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 operator's Autonomous
System Number (ASN). It is expected that the global ID will be
derived from the globally unique ASN of the 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."
When the Global_ID is derived from a 2-octet AS number, the two high-
order octets of this 4-octet identifier MUST be set to zero.
Note that this Global_ID is used solely to provide a globally unique
context for other MPLS-TP identifiers. It has nothing to do with the
use of the ASN in protocols such as BGP.
3.2. ITU Carrier Code
M.1400 defines the ITU Carrier Code (ICC) assigned to a network
operator/service provider and maintained by the ITU-T
Telecommunication Standardization Bureau (TSB): www.itu.int/ITU-T/
inr/icc/index.html.
ICCs can be assigned both to ITU-T and non-ITU-T members and the
referenced local ICC website may containu ICCs of operators of both
kinds.
The ICC is a string of one to six characters, each character being
either alphabetic (i.e. A-Z) or numeric (i.e. 0-9) characters.
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Alphabetic characters in the ICC SHOULD be represented with upper
case letters.
4. Node and Interface Identifiers
An LSR requires identification of the node itself and of its
interfaces. We call the identifier associated with a node a Node
Identifier (Node_ID). Within the context of a particular node, we
call the identifier associated with an interface an Logical Interface
Handle or LIH. The combination of Node_ID::LIH we call an Network
Interface ID or Network_IF_ID.
In existing MPLS deployments Node_IDs are IPv4 addresses. Therefore
we have chosen the Node_ID to be a 32-bit value assigned by the
operator. Where IPv4 addresses are in use the Node_ID can be
automatically mapped to the LSR's /32 IPv4 loopback address. Note
that, when IP reachability is not needed, the 32-bit Node_ID is not
required to have any association with the IPv4 address space used in
the operator's IGP or BGP, other that that they be uniquely chosen
within the scope of that operator.
GMPLS signaling [2] requires interface identification. We have
chosen to adopt the conventions of that RFC. GMPLS allows three
formats for the Interface_ID. For IP numbered links, it is simply
the IPv4 or IPv6 address associated with the interface. The third
format consists of an IPv4 Address plus a 32-bit unsigned integer for
the specific interface.
For MPLS-TP, we have adopted a format consitent with the third format
above. In MPLS-TP, each interface is assigned a 32-bit identifier
which we call an LIH. The LIH MUST be unique within the context of
the Node_ID. We map the Node_ID to the field the field which carries
the IP address. That is, a Nework_IF_ID is a 64-bit identifier
consisting of the Node_ID followed by the LIH. The LIH in turn is a
32-bit unsigned integer unique to the node.
In situations where a Node_ID or an Network_IF_ID needs to be
globally unique, this is accomplished by prefixing the identifier
with the operator's Global_ID. The combination of Global_ID::Node_ID
we call an Global Node ID or Global_Node_ID. Likewise, the
combination of Global_ID::Node_ID::LIH we call an Global Interface ID
or Global_IF_ID.
5. Path Identifiers
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5.1. MPLS-TP LSP Identifiers
[Note: See proposed changes to in the issues section]
GMPLS signalling [3] uses a 5-tuple to uniquely identify an LSP
within a operator's network. This tuple is composed of a Tunnel
Endpoint Address, Tunnel_ID, Extended Tunnel ID, and Tunnel Sender
Address and LSP_ID. For MPLS-TP we have chosen a 4-tuple to uniquely
identify a MPLS-TP LSP. This is composed of a Source Node_ID,
Destination Node_ID, Tunnel_Nbr, and LSP_Nbr. The terms Source and
Destination in this context are used relative to the direction of the
signalling. Note that the Tunnel_ID MUST be unique within the
context of the source.
In situations where a mapping to the GMPLS 5-tuple is required, the
following mapping is used.
o Tunnel Endpoint Address = Destination Node_ID
o Tunnel_ID = Tunnel_Nbr
o Extended Tunnel_ID = Source Node_ID
o Tunnel Sender Address = Source Node_ID
o LSP_ID = LSP_Nbr
A important construct within MPLS_TP is a connection which is
provided across a working and a protect LSP. Note that RFC 4872 [7],
"RSVP-TE Extensions for E2E GMPLS Recovery", requires that the
working and protect LSP have the same identification except for the
LSP_ID, which must be unique. Within this document we will use the
term Tunnel for the connection provided by the working and protect
LSPs.
Thus, a Protected MPLS-TP LSP within a single operator is uniquely
identified by the 3-tuple, Source Node_ID, Destination Node_ID and
Tunnel_Nbr. Similarly, an MPLS-TP LSP is uniquely identified by the
4-tuple, Source Node_ID, Destination Node_ID, Tunnel_Nbr and LSP_Nbr.
In situations where a tunnel or an LSP needs to be globally unique,
this is accomplished by prefixing each of the source and destination
Node_IDs with a operator's Global_ID.
When an MPLS-TP LSP is configured, it MUST be assigned a unique
Network_IF_ID at both the source and destination endpoints. Further
when a MPLS-TP Tunnel is configured, it too must be assigned a unique
Network_IF_ID. Thus a point-to-point tunnel with working and protect
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LSPs will have a total of three Network_IF_IDs assigned at each of
the source and destination.
5.2. Pseudowire Identifiers
Pseudowire signalling (RFC 4447 [1]) defines two FECs used to signal
pseudowires. Of these, FEC Type 129 along with AII Type 2 as defined
in RFC 5003 [6] fits the identification requirements of MPLS-TP.
In an MPLS-TP environment, a PW is identified by a set of identifiers
which can be mapped directly to the elements required by FEC 129 and
AII Type 2. The AII 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 FEC 129, all that is required is a Attachment Group
Identifier (AGI). That field is exactly as specified in RFC 4447.
FEC 129 has a notion of Source AII (SAII) and Target AII (TAII).
These terms are used relative to the direction of the signalling. In
a purely configured environment when referring to the entire PW, this
distinction is not critical. That is a FEC 129 of AGIa::AIIb::AIIc
is equivalent to AGIa::AIIc::AIIb. We note that in a signalled
environment, the required convention in RFC 4447 is that at a
particular endpoint, the AII associated with that endpoint comes
first.
6. Maintenance Identifiers
In MPLS-TP a Maintenance Entity (ME) represents an Entity that
requires management and defines a relationship between a set of
maintenance points. A maintenance point is either Maintenance End-
point (MEP) or a Maintenance Intermediate Point (MIP). This section
defines a means of uniquely identifying Maintenance Entities and
uniquely defining MEPs and MIPs within the context of a Maintenance
Entity.
6.1. Maintenance Entity Identifiers
Maintenance Entity Identifiers (ME-IDs) are required for MPLS-TP
Paths and Pseudowires. Two classes of ME-IDs are defined, one that
follows the IP compatible identifier defined above as well as the
ICC-format.
A Maintenance Entity and an MPLS-TP Path are closely related by
separate concepts. A MPLS-TP Path is a transport entity. It exists
with or without an associated maintenance entity, e.g. when the LSP
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is not monitored.
6.1.1. IP Compatible ME-IDs
In order to automatically generate MEP_IDs for MPLS-TP LSPs and
Pseudowires we simply use the corresponding Path identifier.
However, when encoded in a protocol such as in a TLV, a different
type needs to be defined as the two identifiers are semantically
different.
6.1.2. ICC based ME-IDs
ME ID for MPLS-TP LSPs and Pseudowires MAY use the globally unique
ICC-based format.
In this case, the ME ID is a string of up to thirteen characters,
each character being either alphabetic (i.e. A-Z) or numeric (i.e.
0-9) characters. It consists of two subfields: the ICC (as defined
in section 3) followed by a unique ME ID code (UMC).
The UMC MUST be unique within the organization identified by the ICC.
Note that when encoded in a protocol such as in a TLV, a different
type needs to be defined for LSP and PWs as the OAM capabilities may
be different.
6.2. Maintenance Points
Maintenance points are uniquely associated with a maintenance entity.
Within the context of a ME, MEPs and MIPs must be uniquely
identified. This section describes how MIPs and MEPs are identified.
Note that depending on the requirements of a particular OAM
interaction, the MPLS-TP maintenance entity context may be provided
either explicitly using the ME-IDs described above or implicitly by
the label of the received OAM message.
6.3. MEP_IDs for MPLS-TP LSPs and Tunnels
[Note: See proposed changes to in the issues section]
In order to automatically generate MEP_IDs for MPLS-TP Tunnels and
LSPs, we simply use the Network_IF_ID assigned when they are
configured. This ensures that MEP_IDs are unique for all Tunnels and
LSPs within a operator. When Tunnels or LSPs cross operator
boundaries, these are made unique by pre-pending them with the
operator's Global_ID. [Question: do we want two ACH TLV formats or
do we just spend the extra 4 octets on all OAM]
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6.4. MEP_IDs for Pseudowires
In order to automatically generate MEP_IDs for PWs, we simply use the
AII associated with that end of the PW.
6.5. Maintenance Intermediate Point Identifiers
At a cross connect point, in order to automatically generate MIP_IDs
for MPLS-TP LSPs, we simply use the MEP_IDs of the two interfaces
which are cross connected via the label bindings of the MPLS-TP LSP.
Note that although by this mapping, the MEP and the MIP will
syntactically identical, the semantics will be made clear by both the
TLV encoding and the scoping of the identifier to its MPLS-TP Path.
If only one MIP is configured, then the lower value MEP_ID is chosen.
This ensures that MIP_IDs are unique within the scope of an ME-ID
within a single operator. When Tunnels, LSPs or PWs cross operator
boundaries, MIP_IDs are made unique by pre-pending them with the
operator's Global_ID. [Question: do we want two formats or do we
just spend the extra 4+ octets on all OAM].
[Note: Note - it has been proposed that when there is just one MIP to
use the Node-ID only - need to discuss encoding for this]
7. Open issues
1. The lack of symmetry between the configuration of the "head" and
"Tail" ends of an MPLS-TP LSP makes for difficulties in
configuration and operational intuitiveness. Further it leads to
interoperability issues with other possible implementations of
protection. Finally there are issues with odd configurations
with P2MP / MP2MP (2 endpoints on the same node) I've decided
that the tunnel ID I previously proposed really should be
changed. I propose to make it more like the PW-ID
So instead of
[Src-Global-ID]::Src-Node-ID::[Dst-Global-ID]:: Dst-Node-
ID::Tunnel-nbr
It would be
[Src-Global-ID]::Src-Node-ID::Src-Tunnel-nbr:: [Dst-Global-
ID]::Dst-Node-ID::Dst-Tunnel-nbr
Likewise the Path-ID would go from
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[Src-Global-ID]::Src-Node-ID::[Dst-Global-ID]:: Dst-Node-
ID::Tunnel-nbr::LSP-nbr
to
[Src-Global-ID]::Src-Node-ID::Src-Tunnel-nbr::Src-LSP-nbr::
[Dst-Global-ID]::Dst-Node-ID::Dst-Tunnel-nbr::Dst-LSP-nbr
I would also change the IF-IDs and MEPs to
Tunnel
[Src-Global-ID]::Src-Node-ID::Src-Tunnel-nbr
Path
[Src-Global-ID]::Src-Node-ID::Src-Tunnel-nbr::Src-LSP-nbr
2. Can we do away with tunnel IDs all together and just use the IDs
of the Working Path instead (irrespective of whether it is active
or not)
3. We have two means of identifying operators. Should either be
allowed in all cases or can we constain this. I.e. when there
are both IP compatible and ITU compatible IDs for an Object can
we constrain the operator ID to the corresponding format?
Clearly when only one identifier is defined the both must be
allowed.
4. Details on MEP and MIP identifiers need discussion.
5. Additional ICC identifiers for other entities may be required
6. Do we need IPv6 identifiers as well?
7. Identifiers for P2MP entities
8. Tandem connection Identification - the identification should be
exactly the same as any other MPLS-TP LSP. However, in the ACH
TLV draft we could have a different TLV with the same format as
an MPLS-TP LSP, if there are places where the distinction becomes
important.
9. Are there additional identifiers required for NMS functions?
8. References
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8.1. Normative References
[1] 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.
[2] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS)
Signaling Functional Description", RFC 3471, January 2003.
[3] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS)
Signaling Resource ReserVation Protocol-Traffic Engineering
(RSVP-TE) Extensions", RFC 3473, January 2003.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[5] 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.
[6] Metz, C., Martini, L., Balus, F., and J. Sugimoto, "Attachment
Individual Identifier (AII) Types for Aggregation", RFC 5003,
September 2007.
[7] Lang, J., Rekhter, Y., and D. Papadimitriou, "RSVP-TE
Extensions in Support of End-to-End Generalized Multi-Protocol
Label Switching (GMPLS) Recovery", RFC 4872, May 2007.
[8] Kompella, K., Rekhter, Y., and A. Kullberg, "Signalling
Unnumbered Links in CR-LDP (Constraint-Routing Label
Distribution Protocol)", RFC 3480, February 2003.
[9] Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling in
MPLS Traffic Engineering (TE)", RFC 4201, October 2005.
[10] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label
Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.
[11] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "BFD
For MPLS LSPs", draft-ietf-bfd-mpls-07 (work in progress),
June 2008.
[12] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding
Detection (BFD) for the Pseudowire Virtual Circuit
Connectivity Verification (VCCV)", draft-ietf-pwe3-vccv-bfd-06
(work in progress), July 2009.
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8.2. Informative References
[13] Vigoureux, M., Ward, D., and M. Betts, "Requirements for OAM in
MPLS Transport Networks",
draft-ietf-mpls-tp-oam-requirements-02 (work in progress),
June 2009.
[14] Ohta, H., "Assignment of the 'OAM Alert Label' for
Multiprotocol Label Switching Architecture (MPLS) Operation and
Maintenance (OAM) Functions", RFC 3429, November 2002.
[15] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and
S. Ueno, "MPLS-TP Requirements",
draft-ietf-mpls-tp-requirements-09 (work in progress),
June 2009.
[16] Bocci, M., Bryant, S., and L. Levrau, "A Framework for MPLS in
Transport Networks", draft-ietf-mpls-tp-framework-02 (work in
progress), July 2009.
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
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