MPLS Working Group M. Bocci Internet-Draft Alcatel-Lucent Intended status: Standards Track G. Swallow Expires:September 4,December 16, 2011 Cisco E. Gray EricssonMarch 3,June 14, 2011 MPLS-TP Identifiersdraft-ietf-mpls-tp-identifiers-04draft-ietf-mpls-tp-identifiers-05 Abstract This document specifies identifiers for MPLS-TP objects. Included are identifiers conformant to existing ITU conventions and identifiers which are 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. 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 http://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 onSeptember 4,December 16, 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 . . . . . . . . . . . . . . . . . . . . . . . . .34 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . .34 1.2. Requirements Language . . . . . . . . . . . . . . . . . .45 1.3. Notational Conventionsin Backus-Naur Form. . . . . . . .4. . . . . . . . . . 5 2. Named Entities . . . . . . . . . . . . . . . . . . . . . . . .46 3. Uniquely Identifying an Operator . . . . . . . . . . . . . . .56 3.1. The Global ID . . . . . . . . . . . . . . . . . . . . . .57 3.2. ITU Carrier Code . . . . . . . . . . . . . . . . . . . . .67 4. Node and Interface Identifiers . . . . . . . . . . . . . . . .68 5. MPLS-TP Tunnel and LSP Identifiers . . . . . . . . . . . . . .79 5.1. MPLS-TP Point to Point Tunnel Identifiers . . . . . . . .89 5.2. MPLS-TP LSP Identifiers . . . . . . . . . . . . . . . . .810 5.2.1. MPLS-TP Co-Routed Bidirectional LSP Identifiers . . .810 5.2.2. MPLS-TP Associated Bidirectional LSP Identifiers . . .911 5.3. Mapping toGMPLS and RSVP-TE SignallingRSVP Signaling . . . . . . . . .9. . . . . . . 12 6. Pseudowire Path Identifiers . . . . . . . . . . . . . . . . .1013 7. Maintenance Identifiers . . . . . . . . . . . . . . . . . . .1114 7.1. Maintenance Entity Group Identifiers . . . . . . . . . . .1114 7.1.1. ICC-based MEG Identifiers . . . . . . . . . . . . . .1214 7.1.2. IP Compatible MEG_IDs . . . . . . . . . . . . . . . .1214 7.1.2.1. MPLS-TP Section MEG_IDs . . . . . . . . . . . . . 14 7.1.2.2. MPLS-TP LSP MEG_IDs . . . . . . . . . . . . . . .12 7.1.2.2.15 7.1.2.3. Pseudowire MEG_IDs . . . . . . . . . . . . . . . .1215 7.2. MEP_IDs . . . . . . . . . . . . . . . . . . . . . . . . .1215 7.2.1. ICC-based MEP Identifiers . . . . . . . . . . . . . .1215 7.2.2. IP based MEP_IDs . . . . . . . . . . . . . . . . . . .1315 7.2.2.1. MPLS-TP LSP_MEP_ID . . . . . . . . . . . . . . . .1315 7.2.2.2. MEP_IDs for Pseudowires . . . . . . . . . . . . .1316 7.2.2.3. Pseudowire Segments Endpoint IDs . . . . . . . . .1316 7.3. MIP Identifiers . . . . . . . . . . . . . . . . . . . . .1417 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . .1517 9. Security Considerations . . . . . . . . . . . . . . . . . . .1518 10. References . . . . . . . . . . . . . . . . . . . . . . . . . .1518 10.1. Normative References . . . . . . . . . . . . . . . . . . .1518 10.2. Informative References . . . . . . . . . . . . . . . . . .1618 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .1618 1. Introduction This document specifies identifiers to be used inwithinthe 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 suitable to ITU conventions and to IP/MPLS conventions. Applicability of the different identifier schemas to different applications is outside the scope of this document. 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 AII: Attachment Interface Identifier ASN: Autonomous System Number EGP: Exterior Gateway Protocol FEC: Forwarding Equivalence Class GMPLS: Generalized Multi-Protocol Label Switching ICC: ITU Carrier Code IGP: Interior Gateway Protocol LSP: Label Switched Path LSR: Label Switching Router ME: Maintenance Entity MEG: Maintenance Entity Group MEP: Maintenance Entity Group End Point MIP: Maintenance Entity Group Intermediate Point MPLS: Multi-Protocol Label Switching NNI: Network-to-Network Interface OAM: Operations, Administration and Maintenance P2MP: Point to Multi-Point P2P: Point to Point PW: Pseudowire RSVP: Resource Reservation Protocol RSVP-TE: RSVP Traffic Engineering S-PE: Switching Provider Edge T-PE: Terminating Provider Edge 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 Conventionsin Backus-Naur FormAll multiple-word atomic identifiers use underscores (_) between the words to join the words. Many of the identifiers are composed of aconcatenationset of other identifiers. These are expressedusing Backus-Naur Form (using double-colon - "::" - notation).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 exampleEast-Node_IDA1-Node_ID is the Node_ID of a node referred to asEast. 2. Named Entities In order to configure, operate and manage a transport network based on the MPLS Transport Profile,A1. The notation does define anumberpreferred ordering ofentities require identification. Identifiers forthefollow entities are defined in this document: o Operator * Global_ID * ICC o LSR o LSP o PW o Interface o MEG o MEP o MIP o Tunnel Note that we have borrowedfields. Specifically theterm tunnel from RSVP-TE (RFC 3209) [2] where itdesignation A1 is used todescribe anindicate the lower sort order of a field or set of fields and Z9 is used to indicated 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. 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: * Operator + Global_ID + ICC * LSR * LSP * PW * Interface * MEG * MEP * MIP * Tunnel 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 An operator is uniquely identified by anOperator Identifier (Opr_ID). Two formats are defined,identifier which may take onethatof two formats. One format is compatible with IP operationalpracticepractice, and is called aGlobal_ID and or oneGlobal_ID. The other format is compatible with ITUpractice, thepractice and is called ICC. AnThe Opr_IDoperator MAY use either the Global_ID or ICC format. 3.1. The Global ID RFC 5003 [3] defines a globally unique Attachment Interface Identifier (AII). That AII is composed of three parts, a Global_ID which uniquely identifiesaan operator, a prefix, andfinally andfinally, 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 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 theA Global_IDismust 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 twohigh- orderhigh-order octetsof this 4-octet identifier MUST be setto zero.FurtherASN 0 isreserved.reserved and cannot be assigned. A Global_ID of zero means that no Global_ID ispresent.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.A non-zero Global_ID MUST be derived from an ASN owned by the operator. Note that thisThe Global_ID is used solely to provide a globally unique context for other MPLS-TP identifiers.It has nothingWhile the AS Number used in the Global_ID MUST be one which the operator is entitles to use, the use of the Global_ID is not related todo withthe 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 contain 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. 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. An interface is the attachment point to a serverlayer(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 ofthe Global_ID.a Global_ID or ICC. 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 orBGP.EGP. Where IPv6 addresses are used exclusively, a 32-bit value unique within the scope ofthea Global_ID or ICC is assigned.AAn 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 amidpointintermediate 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'sOpr_ID. The particular combination of Global_ID::Node_ID we call a Global Node IDGlobal_ID orGlobal_Node_ID.ICC. Within the context of a particular node, we call the identifier associated with an interface an Interface Numberor IF_Num.(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 (seesection ,Section 7.3, MIP Identifiers)(Section 7.3)and MUST NOT be used to identify an MPLS-TP interface. An Interface Identifieror IF_ID(IF_ID) identifies an interface uniquely within the context ofan Opr_ID.a Global_ID or ICC. It is formed by concatenating the Node_ID with the IF_Num. That is an IF_ID is a64-bit64- bit identifier formed as Node_ID::IF_Num. This convention was chosen to allow compatibility with GMPLS. GMPLS signaling [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'sOpr_ID.Global_ID or ICC. The attachment point to an MPLS-TP Tunnel (seesectionSection5.15.1) also needs an interface identifier. Note that MPLS-TP supports hierarchical tunnels. The attachment point to a MPLS-TP Tunnel at anysub layer(sub-)layer requires aunique IF_ID.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_ID identifies the transport service and provides a stable binding to the client in the face of changes in the the data plane LSPs used to provide the service due to protectionandor restoration events. This section defines an MPLS-TP Tunnel_ID to uniquely identify a tunnel and MPLS-TP LSP_IDs within the context of that tunnel. For the case where multiple LSPs (for example) are used to support a single service with a common set of end-points, using this identifier allows for a trivial mapping between the server and clientlayers tolayers, providing a common service identifier which 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 orun-protected)unprotected) that may appear to the client as a single service attachment point. Keeping thetunnel numberTunnel_ID consistent across working and protection LSPs is a useful construct currently employed within GMPLS.However there is no requirement thatThe Tunnel_ID for a protection LSPuse the same tunnel number as theMAY differ from that used by its corresponding working LSP. 5.1. MPLS-TP Point to Point Tunnel Identifiers At each endpoint a tunnel is uniquely identified by the endpoint's Node_ID and a locally assigned tunnel number. Specifically a Tunnel_Num is a 16-bit unsigned integer unique within the context of the Node_ID. The motivation for each endpoint having its own tunnel number is to allow a compact form for the MEP-ID. SeesectionSection7.1.2.1.7.2.2.1. Having two tunnel numbers also serves to simplify other signaling (e.g., setup of associatedbi-directionalbidirectional tunnels as described insectionSection5.3.)5.3). The concatenation of the two endpoint identifiers serves as the full identifier.In a configured environment the endpoints are often called East and West.Usingthis conventiontheformat ofA1 / Z9 convention the format of a Tunnel_ID is:East-Node_ID::East-Tunnel_Num::West-Node_ID::West-Tunnel_NumA1-{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:East-Global_Node_ID::East-Tunnel_Num::West-Global_Node_ID:: West-Tunnel_NumA1-{Global_ID::Node_ID::Tunnel_Num}::Z9-{Global_Id::Node_ID:: Tunnel_Num} The corresponding ICC-based version of this identifier would be: A1-{ICC::Node_ID::Tunnel_Num}::Z9-{ICC::Node_ID::Tunnel_Num} When an MPLS-TP Tunnel is configured, it MUST be assigned a unique IF_ID atboth the source and destination endpoints.each endpoint. As usual, the IF_ID is composed of the localNODE_IDNode_ID concatenated with a 32-bit IF_Num. 5.2. MPLS-TP LSP Identifiers 5.2.1. MPLS-TP Co-Routed Bidirectional LSPIdentifiers ForIdentifiers 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_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 dataplane level, a co-routed bidirectional LSP is composed of two unidirectional LSPs traversing the same links in opposite directions. Since a co-routed bidirectional LSPcan be uniquely identified byis provisioned or signaled as a single entity, a singleLSP number within the scope of an MPLS-TP Tunnel_ID. Specifically anLSP_Num isa 16-bit unsigned integer unique within the Tunnel_ID. Thusused for both unidirectional LSPs. The unidirectional LSPs can be referenced by theformat of a LSP_ID is: East-Node_ID::East-Tunnel_Num::West-Node_ID::West- Tunnel_Num::LSP_Numidentifiers: Z9-Node_ID::Z9-Tunnel_Num::LSP_Num::A1-Node_ID and A1-Node_ID::A1-Tunnel_Num::LSP_Num::Z9-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:East-Global_Node_ID::East-Tunnel_Num::West-Global_Node_ID:: West-Tunnel_Num::LSP_NumA1-{Global_ID::Node_ID::Tunnel_Num}::Z9-{Global_Id:: Node_ID::Tunnel_Num}::LSP_Num The corresponding ICC-based version of this identifier would be:East-ICC::East-Node_ID::East-Tunnel_Num::West-ICC::West-Node_ID:: West-Tunnel_Num::LSP_NumA1-{ICC::Node_ID::Tunnel_Num}::Z9-{ICC::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 fromEastA1 toWestZ9 andWestZ9 toEastA1 require LSP_Nums. Each LSPIDs. The each LSP can beis uniquely identified by a single LSP number within the scope of thesendersingress's Tunnel_Num. Specifically an LSP_Num is a 16-bit unsigned integer unique within the Tunnel_Num. Thus the format ofaan MPLS-TP associated bidirectional LSP_ID is:East-Node_ID::East-Tunnel_Num::East-LSP_Num:: West-Node_ID::West-Tunnel_Num::West-LSP_NumA1-{Node_ID::Tunnel_Num::LSP_Num}:: Z9-{Node_ID::Tunnel_Num::LSP_Num} At the dataplane 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:East-Global_Node_ID::East-Tunnel_Num::East-LSP_Num:: West-Global_Node_ID::West-Tunnel_Num::West-LSP_NumA1-{Global_ID::Node_ID::Tunnel_Num::LSP_Num}:: Z9-{Global_Id::Node_ID::Tunnel_Num::LSP_Num} The corresponding ICC-based version of this identifier would be:East-ICC::East-Node_ID::East-Tunnel_Num::East-LSP_Num:: West-ICC::West-Node_ID::West-Tunnel_Num::West-LSP_NumA1-{ICC::Node_ID::Tunnel_Num::LSP_Num}:: Z9-{ICC::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. Both GMPLS and RSVP-TESignallinguse RSVP signaling. This section defines the mapping from an MPLS-TP LSP_ID toGMPLS.RSVP. At this time,GMPLSRSVP has yet to be extended to accommodate Global_IDs. Thus a mapping is only made for the network unique form of the LSP_ID.GMPLSRSVP signaling [5] 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(GMPLS)(RSVP) LSP_ID.In situations whereFor a co-routed bidirectional LSP signaled from A1 to Z9, the mapping to the GMPLS 5-tuple isrequired, the following mapping is used. oas follows: * Tunnel Endpoint Address =West-Node_ID oZ9-Node_ID * Tunnel_ID =East-Tunnel_Num oA1-Tunnel_Num * Extended Tunnel_ID =East-Node_ID oA1-Node_ID * Tunnel Sender Address =East-Node_ID oA1-Node_ID * (RSVP) LSP_ID =East-LSP_NumLSP_Num An associatedbi-directionalbidirectional LSP between two nodesEastA1 andWestZ9 consists of twouni-directionalunidirectional LSPs, one fromEastA1 toWestZ9 and one fromWestZ9 toEast. RSVP-TE is capable of signaling such LSPs.A1. In situations where a mapping to the RSVP 5-tuples is required, the following mappings are used. For theEastA1 toWestZ9 LSP the mapping would be:o* Tunnel Endpoint Address =West-Node_ID oZ9-Node_ID * Tunnel_ID =East-Tunnel_Num oA1-Tunnel_Num * Extended Tunnel_ID =East-Node_ID oA1-Node_ID * Tunnel Sender Address =East-Node_ID oA1-Node_ID * (RSVP) LSP_ID =East-LSP_NumA1-LSP_Num Likewise, theEastZ9 toWest LSPA1 LSP, the mapping would be:o* Tunnel Endpoint Address =East-Node_ID oA1-Node_ID * Tunnel_ID =West-Tunnel_Num oZ9-Tunnel_Num * Extended Tunnel_ID =West-Node_ID oZ9-Node_ID * Tunnel Sender Address =West-Node_ID oZ9-Node_ID * (RSVP) LSP_ID =West-LSP_NumZ9-LSP_Num 6. Pseudowire Path Identifiers Pseudowire signaling (RFC 4447 [6]) defines two FECs used to signal pseudowires. Of these, FEC Type 129 along with AII Type 2 as defined in RFC 5003 [3] 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. To distinguish this identifier from other Pseudowire Identifiers, we call this a Pseudowire Path Identifieror PW_Path_Id.(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 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 signaling. 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 signaled environment, the required convention in RFC 4447 is that at a particular endpoint, the AII associated with that endpoint comes first. The complete PW_Path_Id is:AGI::East-Global_Node_ID::East-AC_ID::West-Global_Node_ID:: West-AC_ID.AGI::A1-{Global_ID::Node_ID::AC_ID}:: Z9-{Global_Id::Node_ID::AC_ID}. The corresponding ICC-based version for this identifier would be:AGI::East-ICC::East-Node_ID::East-AC_ID::West-ICC::West-Node_ID:: West-AC_IDAGI::A1-{ICC::Node_ID::AC_ID}::Z9-{ICC::Node_ID::AC_ID} 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) or a Maintenance Entity Group Intermediate Point (MIP). Maintenance points are uniquely associated with a MEG. Within the context of a MEG, MEPs and MIPs must be uniquely identified. This section defines a means of uniquely identifying Maintenance Entity Groups, Maintenance Entities and uniquely defining 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. Two classes of MEG_IDs are defined, one that follows the IP compatible identifier defined above as well as the ICC-format. 7.1.1. ICC-based MEG Identifiers MEG_ID for MPLS-TP LSPs and Pseudowires MAY use the globally unique ICC-based format. In this case, the MEG_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 MEG code (UMC). The UMC MUST be unique within the organization identified by the ICC. The ICC MEG_ID may be applied equally to a single MPLS-TP LSP or Pseudowires. 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. 7.1.2. IP Compatible MEG_IDs 7.1.2.1. MPLS-TP Section MEG_IDs IP compatible MEG_IDs for MPLS-TP sections are formed by concatenating the two IF_IDs of the corresponding section. For example: A1-IF_ID::Z9-IF_ID 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 Section MEG_ID becomes: A1-{Global_ID::IF_ID}::Z9-{Global_Id::IF_ID} 7.1.2.2. MPLS-TP LSP MEG_IDs Since a MEG pertains to a single MPLS-TP LSP, IP compatible MEG_IDs for MPLS-TP LSPs are simply the corresponding LSP_IDs. 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 MPLS-TP LSP_ID and MPLS-TP LSP MEG_IDs are to be encoded inTLVsTLVs, different types need to be assigned for these two identifiers.7.1.2.2.7.1.2.3. 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. 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_IDisare to be encoded inTLVsTLVs, different types need to be assigned for these two identifiers. 7.2. MEP_IDs 7.2.1. ICC-based MEP Identifiers ICC-based MEP_IDs for MPLS-TP LSPs and Pseudowires are formed by appending a unique number to the MEG_ID defined insectionSection 7.1.1 above. 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-based MEP_ID is: MEG_ID::MEP_Index An ICC-based MEP ID is globally unique by construction given the ICC- based MEG_ID global uniqueness. 7.2.2. IP based MEP_IDs 7.2.2.1. 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 endpoint. This ensures that MEP_IDs are unique for all 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. The MPLS-TP LSP_MEP_ID isNode_ID::Tunnel_Num::LSP_Num,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 ofAssociated Bi-directionalco-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 7.2.2.2. MEP_IDs for Pseudowires Like MPLS-TP LSPs, Pseudowire endpoints (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 used in end-to-end for an 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. 7.2.2.3. Pseudowire Segments Endpoint IDs In some OAM communications, messages are originated by the node at one end of a PW segment and relayed to the other end of that same segment by setting the TTL of the PW label to one (1). For a multi- segment pseudowire, TTL could be set to any value that would cause OAM messages to reach the target segment end-point (up to and including 255). In such communications an identifier for the pseudowire segmentendpoint.endpoint is needed. We call this a Pseudowire Segments Endpoint ID or PW_SE_ID. The PW_SE_ID is formed by a combination of a PW MEP_ID and the identification of the local node. At an S-PE, there are two PW segments. We distinguish the segments by using the MEP_ID which is upstream of the PW segment in question. To complete the identification we suffix this with the identification of the local node. +-------+ +-------+ +-------+ +-------+ | | | | | | | | | A|---------|B C|---------|D E|---------|F | | | | | | | | | +-------+ +-------+ +-------+ +-------+ (T)PE1 (S)PE2 (S)PE3 (T)PE4 Pseudowire Maintenance Points For example, suppose that in the above figure all of the nodes have Global_ID GID1; the node are represented as named in the figure; and The identification for the Pseudowire is: AGI = AGI1East-Global_IDA1-Global_ID = GID1East-Node_IDA1-Node_ID = PE1East-AC_IDA1-AC_ID = AII1West-Global_IDZ9-Global_ID = GID1West-Node_IDZ9-Node_ID = PE4West-AC_IDZ9-AC_ID = AII4 The MEP_ID at point A would be - AGI1::GID1::PE1::AII1 The PW_SE_ID at point B would be - AGI1::GID1::PE4::AII4::GID1::PE2 The PW_SE_ID at point C would be - AGI1::GID1::PE1::AII1::GID1::PE2 7.3. MIP Identifiers At a cross-connect point, in order to automatically generate MIP_IDs for MPLS-TP, we simply use the IF_IDs of the two interfaces which are cross-connected via the label bindings of the MPLS-TPLSP.LSP or PW. This allows, two 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. IANA Considerations There are no IANA actions resulting from this document. 9. Security Considerations This document describes an information model and, as such, does not introduce security concerns. Protocol specifications that describe use of this informationmodel - however -model, however, may introduce security risks 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. 10. References 10.1. 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. 10.2. 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. 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