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Network Working Group                                  J.P. Vasseur, Ed.Request for Comments: 5073                           Cisco Systems, Inc.Category: Standards Track                              J.L. Le Roux, Ed.                                                          France Telecom                                                           December 2007IGP Routing Protocol Extensions forDiscovery of Traffic Engineering Node CapabilitiesStatus of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Abstract   It is highly desired, in several cases, to take into account Traffic   Engineering (TE) node capabilities during Multi Protocol Label   Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineered   Label Switched Path (TE-LSP) selection, such as, for instance, the   capability to act as a branch Label Switching Router (LSR) of a   Point-To-MultiPoint (P2MP) LSP.  This requires advertising these   capabilities within the Interior Gateway Protocol (IGP).  For that   purpose, this document specifies Open Shortest Path First (OSPF) and   Intermediate System-Intermediate System (IS-IS) traffic engineering   extensions for the advertisement of control plane and data plane   traffic engineering node capabilities.Vasseur & Le Roux           Standards Track                     [Page 1]

RFC 5073 IGP Ext for Discovery of TE Node Cap December 2007Table of Contents1. Introduction.....................................................22. Terminology......................................................33. TE Node Capability Descriptor ...................................33.1. Description ................................................33.2. Required Information .......................................34. TE Node Capability Descriptor TLV Formats .......................44.1. OSPF TE Node Capability Descriptor TLV Format ..............44.2. IS-IS TE Node Capability Descriptor sub-TLV format .........55. Elements of Procedure ...........................................65.1. OSPF .......................................................65.2. IS-IS ......................................................76. Backward Compatibility ..........................................87. Security Considerations .........................................88. IANA Considerations .............................................88.1. OSPF TLV ...................................................88.2. ISIS sub-TLV ...............................................88.3. Capability Registry ........................................99. Acknowledgments .................................................910. References ....................................................1010.1. Normative References .....................................1010.2. Informative References ...................................111. Introduction Multi Protocol Label Switching-Traffic Engineering (MPLS-TE) routing ([RFC3784], [RFC3630], [OSPFv3-TE]) relies on extensions to link state Interior Gateway Protocols (IGP) ([IS-IS], [RFC1195], [RFC2328], [RFC2740]) in order to advertise Traffic Engineering (TE) link information used for constraint-based routing. Further Generalized MPLS (GMPLS) related routing extensions are defined in [RFC4205] and [RFC4203]. It is desired to complement these routing extensions in order to advertise TE node capabilities, in addition to TE link information. These TE node capabilities will be taken into account as constraints during path selection. Indeed, it is useful to advertise data plane TE node capabilities, such as the capability for a Label Switching Router (LSR) to be a branch LSR or a bud-LSR of a Point-To-MultiPoint (P2MP) Label Switched Path (LSP). These capabilities can then be taken into account as constraints when computing the route of TE LSPs. It is also useful to advertise control plane TE node capabilities such as the capability to support GMPLS signaling for a packet LSR, or the capability to support P2MP (Point to Multipoint) TE LSPVasseur & Le Roux Standards Track [Page 2]

RFC 5073 IGP Ext for Discovery of TE Node Cap December 2007 signaling. This allows selecting a path that avoids nodes that do not support a given control plane feature, or triggering a mechanism to support such nodes on a path. Hence, this facilitates backward compatibility. For that purpose, this document specifies IGP (OSPF and IS-IS) extensions in order to advertise data plane and control plane capabilities of a node. A new TLV is defined for OSPF, the TE Node Capability Descriptor TLV, to be carried within the Router Information LSA ([RFC4970]). A new sub-TLV is defined for IS-IS, the TE Node Capability Descriptor sub-TLV, to be carried within the IS-IS Capability TLV ([RFC4971]).2. Terminology This document uses terminologies defined in [RFC3031], [RFC3209], and [RFC4461]. 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 inRFC 2119 [RFC2119].3. TE Node Capability Descriptor3.1. Description LSRs in a network may have distinct control plane and data plane Traffic Engineering capabilities. The TE Node Capability Descriptor information defined in this document describes data and control plane capabilities of an LSR. Such information can be used during path computation so as to avoid nodes that do not support a given TE feature either in the control or data plane, or to trigger procedures to handle these nodes along the path (e.g., trigger LSP hierarchy to support a legacy transit LSR on a P2MP LSP (see [RFC4875])).3.2. Required Information The TE Node Capability Descriptor contains a variable-length set of bit flags, where each bit corresponds to a given TE node capability.Vasseur & Le Roux Standards Track [Page 3]

RFC 5073         IGP Ext for Discovery of TE Node Cap      December 2007   Five TE Node Capabilities are defined in this document:      - B bit: when set, this flag indicates that the LSR can act               as a branch node on a P2MP LSP (see [RFC4461]);      - E bit: when set, this flag indicates that the LSR can act               as a bud LSR on a P2MP LSP, i.e., an LSR that is both               transit and egress (see [RFC4461]);      - M bit: when set, this flag indicates that the LSR supports               MPLS-TE signaling ([RFC3209]);      - G bit: when set this flag indicates that the LSR supports               GMPLS signaling ([RFC3473]);      - P bit: when set, this flag indicates that the LSR supports               P2MP MPLS-TE signaling ([RFC4875]).   Note that new capability bits may be added in the future if required.4.  TE Node Capability Descriptor TLV Formats4.1.  OSPF TE Node Capability Descriptor TLV Format   The OSPF TE Node Capability Descriptor TLV is a variable length TLV   that contains a series of bit flags, where each bit correspond to a   TE node capability.  The bit-field MAY be extended with additional   32-bit words if more bit flags need to be assigned.  Any unknown bit   flags SHALL be treated as Reserved bits.   The OSPF TE Node Capability Descriptor TLV is carried within an OSPF   Router Information LSA, which is defined in [RFC4970].   The format of the OSPF TE Node Capability Descriptor TLV is the same   as the TLV format used by the Traffic Engineering Extensions to OSPF   [RFC3630].  That is, the TLV is composed of 2 octets for the type, 2   octets specifying the length of the value field, and a value field.   The OSPF TE Node Capability Descriptor TLV has the following format:      TYPE:     5 (seeSection 8.1)      LENGTH:   Variable (multiple of 4).      VALUE:    Array of units of 32 flags numbered from the most                significant bit as bit zero, where each bit represents                a TE node capability.Vasseur & Le Roux           Standards Track                     [Page 4]

RFC 5073 IGP Ext for Discovery of TE Node Cap December 2007 The following bits are defined: Bit Capabilities 0 B bit: P2MP Branch Node capability: When set, this indicates that the LSR can act as a branch node on a P2MP LSP [RFC4461]. 1 E bit: P2MP Bud-LSR capability: When set, this indicates that the LSR can act as a bud LSR on a P2MP LSP, i.e., an LSR that is both transit and egress [RFC4461]. 2 M bit: If set, this indicates that the LSR supports MPLS-TE signaling ([RFC3209]). 3 G bit: If set, this indicates that the LSR supports GMPLS signaling ([RFC3473]). 4 P bit: If set, this indicates that the LSR supports P2MP MPLS-TE signaling ([RFC4875]). 5-31 Reserved for future assignments by IANA. Reserved bits MUST be set to zero on transmission, and MUST be ignored on reception. If the length field is greater than 4, implying that there are more than 32 bits in the value field, then any additional bits (i.e., not yet assigned) are reserved.4.2. IS-IS TE Node Capability Descriptor sub-TLV format The IS-IS TE Node Capability Descriptor sub-TLV is a variable length sub-TLV that contains a series of bit flags, where each bit corresponds to a TE node capability. The bit-field MAY be extended with additional bytes if more bit flags need to be assigned. Any unknown bit flags SHALL be treated as Reserved bits. The IS-IS TE Node Capability Descriptor sub-TLV is carried within an IS-IS CAPABILITY TLV, which is defined in [RFC4971]. The format of the IS-IS TE Node Capability sub-TLV is the same as the sub-TLV format used by the Traffic Engineering Extensions to IS-IS [RFC3784]. That is, the sub-TLV is composed of 1 octet for the type, 1 octet specifying the length of the value field. The IS-IS TE Node Capability Descriptor sub-TLV has the following format: TYPE: 1 (seeSection 8.2) LENGTH: Variable VALUE: Array of units of 8 flags numbered from the most significant bit as bit zero, where each bit represents a TE node capability.Vasseur & Le Roux Standards Track [Page 5]

RFC 5073         IGP Ext for Discovery of TE Node Cap      December 2007   The following bits are defined:   Bit       Capabilities    0      B bit: P2MP Branch Node capability: When set, this indicates           that the LSR can act as a branch node on a P2MP LSP           [RFC4461].    1      E bit: P2MP Bud-LSR capability: When set, this indicates           that the LSR can act as a bud LSR on a P2MP LSP, i.e., an           LSR that is both transit and egress [RFC4461].    2      M bit: If set, this indicates that the LSR supports MPLS-TE           signaling ([RFC3209]).    3      G bit: If set, this indicates that the LSR supports GMPLS           signaling ([RFC3473]).    4      P bit: If set, this indicates that the LSR supports P2MP           MPLS-TE signaling ([RFC4875]).    5-7    Reserved for future assignments by IANA.   Reserved bits MUST be set to zero on transmission, and MUST be   ignored on reception.  If the length field is great than 1, implying   that there are more than 8 bits in the value field, then any   additional bits (i.e., not yet assigned) are reserved.5.  Elements of Procedure5.1.  OSPF   The TE Node Capability Descriptor TLV is advertised, within an OSPFv2   Router Information LSA (Opaque type of 4 and Opaque ID of 0) or an   OSPFv3 Router Information LSA (function code of 12), which are   defined in [RFC4970].  As such, elements of procedure are inherited   from those defined in [RFC2328], [RFC2740], and [RFC4970].   The TE Node Capability Descriptor TLV advertises capabilities that   may be taken into account as constraints during path selection.   Hence, its flooding scope is area-local, and it MUST be carried   within an OSPFv2 type 10 Router Information LSA (as defined in   [RFC2370]) or an OSPFv3 Router Information LSA with the S1 bit set   and the S2 bit cleared (as defined in [RFC2740]).   A router MUST originate a new OSPF Router Information LSA whenever   the content of the TE Node Capability Descriptor TLV changes or   whenever required by the regular OSPF procedure (LSA refresh (every   LSRefreshTime)).Vasseur & Le Roux           Standards Track                     [Page 6]

RFC 5073 IGP Ext for Discovery of TE Node Cap December 2007 The TE Node Capability Descriptor TLV is OPTIONAL and MUST NOT appear more than once in an OSPF Router Information LSA. If a TE Node Capability Descriptor TLV appears more than once in an OSPF Router Information LSA, only the first occurrence MUST be processed and others MUST be ignored. When an OSPF Router Information LSA does not contain any TE Node Capability Descriptor TLV, this means that the TE node capabilities of that LSR are unknown. Note that a change in any of these capabilities MAY trigger Constrained Shortest Path First (CSPF) computation, but MUST NOT trigger normal SPF computation. Note also that TE node capabilities are expected to be fairly static. They may change as the result of configuration change or software upgrade. This is expected not to appear more than once a day.5.2. IS-IS The TE Node Capability sub-TLV is carried within an IS-IS CAPABILITY TLV defined in [RFC4971]. As such, elements of procedure are inherited from those defined in [RFC4971]. The TE Node Capability Descriptor sub-TLV advertises capabilities that may be taken into account as constraints during path selection. Hence, its flooding is area-local, and it MUST be carried within an IS-IS CAPABILITY TLV having the S flag cleared. An IS-IS router MUST originate a new IS-IS LSP whenever the content of any of the TE Node Capability sub-TLV changes or whenever required by the regular IS-IS procedure (LSP refresh). The TE Node Capability Descriptor sub-TLV is OPTIONAL and MUST NOT appear more than once in an ISIS Router Capability TLV. When an IS-IS LSP does not contain any TE Node Capability Descriptor sub-TLV, this means that the TE node capabilities of that LSR are unknown. Note that a change in any of these capabilities MAY trigger CSPF computation, but MUST NOT trigger normal SPF computation. Note also that TE node capabilities are expected to be fairly static. They may change as the result of configuration change, or software upgrade. This is expected not to appear more than once a day.Vasseur & Le Roux Standards Track [Page 7]

RFC 5073 IGP Ext for Discovery of TE Node Cap December 20076. Backward Compatibility The TE Node Capability Descriptor TLVs defined in this document do not introduce any interoperability issues. For OSPF, a router not supporting the TE Node Capability Descriptor TLV will just silently ignore the TLV, as specified in [RFC4970]. For IS-IS, a router not supporting the TE Node Capability Descriptor sub-TLV will just silently ignore the sub-TLV, as specified in [RFC4971]. When the TE Node Capability Descriptor TLV is absent, this means that the TE Capabilities of that LSR are unknown. The absence of a word of capability flags in OSPF or an octet of capability flags in IS-IS means that these capabilities are unknown.7. Security Considerations This document specifies the content of the TE Node Capability Descriptor TLV in IS-IS and OSPF to be used for (G)MPLS-TE path computation. As this TLV is not used for SPF computation or normal routing, the extensions specified here have no direct effect on IP routing. Tampering with this TLV may have an effect on Traffic Engineering computation. Mechanisms defined to secure IS-IS Link State PDUs [RFC3567], OSPF LSAs [RFC2154], and their TLVs can be used to secure this TLV as well.8. IANA Considerations8.1. OSPF TLV [RFC4970] defines a new codepoint registry for TLVs carried in the Router Information LSA defined in [RFC4970]. IANA has made a new codepoint assignment from that registry for the TE Node Capability Descriptor TLV defined in this document and carried within the Router Information LSA. The value is 5. SeeSection 4.1 of this document.8.2. ISIS sub-TLV IANA has defined a registry for sub-TLVs of the IS-IS CAPABILITY TLV defined in [RFC4971]. IANA has made a new codepoint assignment from that registry for the TE Node Capability Descriptor sub-TLV defined in this document, and carried within the ISIS CAPABILITY TLV. The value is 1. SeeSection4.2 of this document.Vasseur & Le Roux Standards Track [Page 8]

RFC 5073 IGP Ext for Discovery of TE Node Cap December 20078.3. Capability Registry IANA has created a new registry to manage the space of capability bit flags carried within the OSPF and ISIS TE Node Capability Descriptor. A single registry must be defined for both protocols. A new base registry has been created to cover IGP-TE registries that apply to both OSPF and IS-IS, and the new registry requested by this document is a sub-registry of this new base registry. Bits in the new registry should be numbered in the usual IETF notation, starting with the most significant bit as bit zero. New bit numbers may be allocated only by an IETF Consensus action. Each bit should be tracked with the following qualities: - Bit number - Defining RFC - Name of bit IANA has made assignments for the five TE node capabilities defined in this document (see Sections8.1 and8.2) using the following values: Bit No. Name Reference --------+---------------------------------------+--------------- 0 B bit: P2MP Branch LSR capability [RFC5073] 1 E bit: P2MP Bud LSR capability [RFC5073] 2 M bit: MPLS-TE support [RFC5073] 3 G bit: GMPLS support [RFC5073] 4 P bit: P2MP RSVP-TE support [RFC5073] 5-7 Unassigned [RFC5073]9. Acknowledgments We would like to thank Benoit Fondeviole, Adrian Farrel, Dimitri Papadimitriou, Acee Lindem, and David Ward for their useful comments and suggestions. We would also like to thank authors of [RFC4420] and [RFC4970] by which some text of this document has been inspired. Adrian Farrel prepared the final version of this document for submission to the IESG.Vasseur & Le Roux Standards Track [Page 9]

RFC 5073         IGP Ext for Discovery of TE Node Cap      December 200710.  References10.1.  Normative References   [RFC1195]    Callon, R., "Use of OSI IS-IS for routing in TCP/IP and                dual environments",RFC 1195, December 1990.   [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate                Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC2328]    Moy, J., "OSPF Version 2", STD 54,RFC 2328, April 1998.   [RFC2370]    Coltun, R., "The OSPF Opaque LSA Option",RFC 2370, July                1998.   [RFC2740]    Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6",RFC 2740, December 1999.   [RFC3031]    Rosen, E., Viswanathan, A., and R. Callon,                "Multiprotocol Label Switching Architecture",RFC 3031,                January 2001.   [RFC3209]    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.   [RFC3473]    Berger, L., Ed., "Generalized Multi-Protocol Label                Switching (GMPLS) Signaling Resource ReserVation                Protocol-Traffic Engineering (RSVP-TE) Extensions",RFC3473, January 2003.   [RFC3630]    Katz, D., Kompella, K., and D. Yeung, "Traffic                Engineering (TE) Extensions to OSPF Version 2",RFC3630, September 2003.   [RFC3784]    Smit, H. and T. Li, "Intermediate System to Intermediate                System (IS-IS) Extensions for Traffic Engineering (TE)",RFC 3784, June 2004.   [IS-IS]      "Intermediate System to Intermediate System Intra-Domain                Routeing Exchange Protocol for use in Conjunction with                the Protocol for Providing the Connectionless-mode                Network Service (ISO 8473)", ISO 10589.   [RFC4971]    Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,                "Intermediate System to Intermediate System (IS-IS)                Extensions for Advertising Router Information",RFC4971, July 2007.Vasseur & Le Roux           Standards Track                    [Page 10]

RFC 5073         IGP Ext for Discovery of TE Node Cap      December 2007   [RFC4970]    Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R.,                and S. Shaffer, "Extensions to OSPF for Advertising                Optional Router Capabilities",RFC 4970, July 2007.   [RFC4875]    Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.                Yasukawa, Ed., "Extensions to Resource Reservation                Protocol - Traffic Engineering (RSVP-TE) for Point-to-                Multipoint TE Label Switched Paths (LSPs)",RFC 4875,                May 2007.10.2.  Informative References   [RFC2154]    Murphy, S., Badger, M., and B. Wellington, "OSPF with                Digital Signatures",RFC 2154, June 1997.   [RFC3567]    Li, T. and R. Atkinson, "Intermediate System to                Intermediate System (IS-IS) Cryptographic                Authentication",RFC 3567, July 2003.   [RFC4203]    Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions                in Support of Generalized Multi-Protocol Label Switching                (GMPLS)",RFC 4203, October 2005.   [RFC4205]    Kompella, K., Ed., and Y. Rekhter, Ed., "Intermediate                System to Intermediate System (IS-IS) Extensions in                Support of Generalized Multi-Protocol Label Switching                (GMPLS)",RFC 4205, October 2005.   [RFC4420]    Farrel, A., Ed., Papadimitriou, D., Vasseur, J.-P., and                A. Ayyangar, "Encoding of Attributes for Multiprotocol                Label Switching (MPLS) Label Switched Path (LSP)                Establishment Using Resource ReserVation Protocol-                Traffic Engineering (RSVP-TE)",RFC 4420, February 2006.   [RFC4461]    Yasukawa, S., Ed., "Signaling Requirements for Point-                to-Multipoint Traffic-Engineered MPLS Label Switched                Paths (LSPs)",RFC 4461, April 2006.   [OSPFv3-TE]  Ishiguro K., Manral V., Davey A., and Lindem A.,                "Traffic Engineering Extensions to OSPF version 3", Work                in Progress.Vasseur & Le Roux           Standards Track                    [Page 11]

RFC 5073         IGP Ext for Discovery of TE Node Cap      December 2007Contributors' Addresses   Seisho Yasukawa   NTT   3-9-11 Midori-cho,   Musashino-shi, Tokyo 180-8585, Japan   EMail: s.yasukawa@hco.ntt.co.jp   Stefano Previdi   Cisco Systems, Inc   Via Del Serafico 200   Roma, 00142   Italy   EMail: sprevidi@cisco.com   Peter Psenak   Cisco Systems, Inc   Pegasus Park DE Kleetlaan 6A   Diegmen, 1831   BELGIUM   EMail: ppsenak@cisco.com   Paul Mabbey   Comcast   USAEditors' Addresses   Jean-Philippe Vasseur   Cisco Systems, Inc.   1414 Massachusetts Avenue   Boxborough, MA, 01719   USA   EMail: jpv@cisco.com   Jean-Louis Le Roux   France Telecom   2, avenue Pierre-Marzin   22307 Lannion Cedex   FRANCE   EMail: jeanlouis.leroux@orange-ftgroup.comVasseur & Le Roux           Standards Track                    [Page 12]

RFC 5073         IGP Ext for Discovery of TE Node Cap      December 2007Full Copyright Statement   Copyright (C) The IETF Trust (2007).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Vasseur & Le Roux           Standards Track                    [Page 13]

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