IGP extension for PCEP security capability support in PCE discovery
draft-ietf-lsr-pce-discovery-security-support-13

PCE working group                                               D. Lopez
Internet-Draft                                            Telefonica I+D
Updates: 5088, 5089, 8231, 8306 (if approved)                      Q. Wu
Intended status: Standards Track                                D. Dhody
Expires: 14 April 2023                                             Q. Ma
                                                                  Huawei
                                                                 D. King
                                                      Old Dog Consulting
                                                         11 October 2022

  IGP extension for PCEP security capability support in PCE discovery
            draft-ietf-lsr-pce-discovery-security-support-13

Abstract

   When a Path Computation Element (PCE) is a Label Switching Router
   (LSR) participating in the Interior Gateway Protocol (IGP), or even a
   server participating in the IGP, its presence and path computation
   capabilities can be advertised using IGP flooding.  The IGP
   extensions for PCE discovery (RFC 5088 and RFC 5089) define a method
   to advertise path computation capabilities using IGP flooding for
   OSPF and IS-IS respectively.  However these specifications lack a
   method to advertise PCE Communication Protocol (PCEP) security (e.g.,
   Transport Layer Security (TLS), TCP Authentication Option (TCP-AO))
   support capability.

   This document defines capability flag bits for the PCE-CAP-FLAGS sub-
   TLV that can be announced as an attribute in the IGP advertisement to
   distribute PCEP security support information.  In addition, this
   document updates RFC 5088 and RFC 5089 to allow advertisement of a
   Key ID or Key Chain Name Sub-TLV to support TCP-AO security
   capability.  Further, this document updates RFC 8231 and RFC 8306.

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 https://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."

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   This Internet-Draft will expire on 14 April 2023.

Copyright Notice

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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions used in this document . . . . . . . . . . . . . .   4
   3.  IGP extension for PCEP security capability support  . . . . .   4
     3.1.  Use of PCEP security capability support for PCE
           discovery . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  KEY-ID Sub-TLV  . . . . . . . . . . . . . . . . . . . . .   5
       3.2.1.  IS-IS . . . . . . . . . . . . . . . . . . . . . . . .   5
       3.2.2.  OSPF  . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  KEY-CHAIN-NAME Sub-TLV  . . . . . . . . . . . . . . . . .   6
       3.3.1.  IS-IS . . . . . . . . . . . . . . . . . . . . . . . .   6
       3.3.2.  OSPF  . . . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Update to RFCs  . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Backward Compatibility Considerations . . . . . . . . . . . .   8
   6.  Management Considerations . . . . . . . . . . . . . . . . . .   8
     6.1.  Control of Policy and Functions . . . . . . . . . . . . .   8
     6.2.  Information and Data Model  . . . . . . . . . . . . . . .   8
     6.3.  Liveness Detection and Monitoring . . . . . . . . . . . .   9
     6.4.  Verify Correct Operations . . . . . . . . . . . . . . . .   9
     6.5.  Requirements on Other Protocols and Functional
           Components  . . . . . . . . . . . . . . . . . . . . . . .   9
     6.6.  Impact on Network Operations  . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  PCE Capability Flags  . . . . . . . . . . . . . . . . . .  10
     8.2.  PCED sub-TLV Type Indicators  . . . . . . . . . . . . . .  10
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     10.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

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1.  Introduction

   As described in [RFC5440], Path Computation Element Communication
   Protocol (PCEP) communication privacy and integrity are important
   issues, as an attacker that intercepts a PCEP message could obtain
   sensitive information related to computed paths and resources.
   Authentication and integrity checks allow the receiver of a PCEP
   message to know that the message genuinely comes from the node that
   purports to have sent it and to know whether the message has been
   modified.

   Among the possible solutions mentioned in that document, Transport
   Layer Security (TLS) [RFC8446] provides support for peer
   authentication, and message encryption and integrity while TCP
   Authentication Option (TCP-AO) [RFC5925] and Cryptographic Algorithms
   for TCP-AO [RFC5926] offer significantly improved security for
   applications using TCP.  As specified in section 4 of [RFC8253], in
   order for a Path Computation Client (PCC) to establish a connection
   with a PCE server using TLS or TCP-AO, the PCC needs to know whether
   PCE server supports TLS or TCP-AO as a secure transport.

   [RFC5088] and [RFC5089] define a method to advertise path computation
   capabilities using IGP flooding for OSPF and IS-IS respectively.
   However, these specifications lack a method to advertise PCEP
   security (e.g., TLS) support capability.

   This document defines capability flag bits for the PCE-CAP-FLAGS sub-
   TLV that can be announced as attributes in the IGP advertisement to
   distribute PCEP security support information.  In addition, this
   document updates [RFC5088] and [RFC5089] to allow advertisement of a
   Key ID or Key Chain Name Sub-TLV to support TCP-AO security
   capability.

   As per [RFC5088], the IANA created a top-level OSPF registry, the
   "Path Computation Element (PCE) Capability Flags" registry.  This
   document updates [RFC5088] and moves the registry to "Interior
   Gateway Protocol (IGP) Parameters".  [RFC5089] states that the IS-IS
   uses the same registry as OSPF.  This document updates [RFC5089] to
   refer to the new IGP registry.  Further, this document updates
   [RFC8231] where it references the registry location as "Open Shortest
   Path First (OSPF) Parameters" registry to "Interior Gateway Protocol
   (IGP) Parameters" registry.  This document updates [RFC8306] where it
   uses the term "OSPF PCE Capability Flag" and request assignment from
   OSPF Parameters registry with "PCE Capability Flag" and the IGP
   Parameters registry.

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   Note that [RFC5557] uses the term "OSPF registry" instead of the "IGP
   registry" whereas [RFC8623] and [RFC9168] uses the term "OSPF
   Parameters" instead of "IGP Parameters".

   Note that the PCEP Open message exchange is another way to discover
   PCE capabilities information, but in this instance, the TCP security
   related key parameters need to be known before the PCEP session is
   established and the PCEP Open messages are exchanged.  Thus, the use
   of the PCE discovery and capabilities advertisement of the IGP needs
   to be leveraged.

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  IGP extension for PCEP security capability support

   [RFC5088] defines a PCE Discovery (PCED) TLV carried in an OSPF
   Router Information Link State Advertisement (LSA) as defined in
   [RFC7770] to facilitate PCE discovery using OSPF.  This document
   defines two capability flag bits in the OSPF PCE Capability Flags to
   indicate TCP Authentication Option (TCP-AO) support
   [RFC5925][RFC5926] and PCEP over TLS support [RFC8253] respectively.

   Similarly, [RFC5089] defines the PCED sub-TLV for use in PCE
   discovery using IS-IS.  This document will use the same flag for the
   OSPF PCE Capability Flags sub-TLV to allow IS-IS to indicate TCP
   Authentication Option (TCP-AO) support, PCEP over TLS support
   respectively.

   The IANA assignments for shared OSPF and IS-IS Security Capability
   Flags are documented in Section 8.1 ("PCE Capability Flags") of this
   document.

3.1.  Use of PCEP security capability support for PCE discovery

   TCP-AO, PCEP over TLS support flag bits are advertised using IGP
   flooding.

   *  PCE supports TCP-AO: IGP advertisement SHOULD include TCP-AO
      support flag bit.

   *  PCE supports TLS: IGP advertisement SHOULD include PCEP over TLS
      support flag bit.

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   If the PCE supports multiple security mechanisms, it SHOULD include
   all corresponding flag bits in its IGP advertisement.

   A client's configuration MAY indicate that support for a given
   security capability is required.  If a client is configured to
   require that its PCE server supports TCP-AO, the client MUST verify
   that the TCP-AO flag bit in the PCE-CAP-FLAGS sub-TLV for a given
   server is set before it opens a connection to that server.
   Similarly, if the client is configured to require that its PCE server
   supports TLS, the client MUST verify that the PCEP over TLS support
   flag bit in the PCE-CAP-FLAGS sub-TLV for a given server is set
   before it opens a connection to that server.

3.2.  KEY-ID Sub-TLV

   The KEY-ID sub-TLV specifies an identifier that can be used by the
   PCC to identify the TCP-AO key [RFC5925] (referred to as KeyID).

3.2.1.  IS-IS

   The KEY-ID sub-TLV MAY be present in the PCED sub-TLV carried within
   the IS-IS Router CAPABILITY TLV when the capability flag bit of PCE-
   CAP-FLAGS sub-TLV in IS-IS is set to indicate TCP Authentication
   Option (TCP-AO) support.

   The KEY-ID sub-TLV has the following format:

      Type: 6

      Length: 1

      KeyID: The one octet Key ID as per [RFC5925] to uniquely identify
      the Master Key Tuple (MKT).

3.2.2.  OSPF

   Similarly, this sub-TLV MAY be present in the PCED TLV carried within
   OSPF Router Information LSA when the capability flag bit of PCE-CAP-
   FLAGS sub-TLV in OSPF is set to indicate TCP-AO support.

   The format of KEY-ID sub-TLV is as follows:

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                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type = 6         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    KeyID      |                 Reserved                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type: 6

      Length: 4

      KeyID: The one octet Key ID as per [RFC5925] to uniquely identify
      the Master Key Tuple (MKT).

      Reserved: MUST be set to zero while sending and ignored on
      receipt.

3.3.  KEY-CHAIN-NAME Sub-TLV

   The KEY-CHAIN-NAME sub-TLV specifies a keychain name that can be used
   by the PCC to identify the keychain.  The keychain name could be
   manually configured via CLI or installed in the YANG datastore (see
   [RFC8177]) at the PCC.

3.3.1.  IS-IS

   The KEY-CHAIN-NAME sub-TLV MAY be present in the PCED sub-TLV carried
   within the IS-IS Router CAPABILITY TLV when the capability flag bit
   of the PCE-CAP-FLAGS sub-TLV in IS-IS is set to indicate TCP
   Authentication Option (TCP-AO) support.

   The KEY-CHAIN-NAME sub-TLV has the following format:

      Type: 7

      Length: Variable, encodes the length of the value field.

      Key Name: The Key Chain Name contains a string of 1 to 255 octets
      to be used to identify the key chain.  It MUST be encoded using
      UTF-8.  A receiving entity MUST NOT interpret invalid UTF-8
      sequences and ignore them.  This field is not NULL terminated.
      UTF-8 "Shortest Form" encoding is REQUIRED to guard against the
      technical issues outlined in [UTR36].

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3.3.2.  OSPF

   Similarly, this sub-TLV MAY be present in the PCED TLV carried within
   the OSPF Router Information LSA when the capability flag bit of PCE-
   CAP-FLAGS sub-TLV in OSPF is set to indicate TCP-AO support.  The
   sub-TLV MUST be zero-padded so that the sub-TLV is 4-octet aligned.

   The format of KEY-CHAIN-NAME sub-TLV is as follows:

                        1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type = 7         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                     Key Chain Name                          //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type: 7

      Length: Variable, padding is not included in the Length field

      Key Name: The Key Chain Name contains a string of 1 to 255 octets
      to be used to identify the key chain.  It MUST be encoded using
      UTF-8.  A receiving entity MUST NOT interpret invalid UTF-8
      sequences and ignore them.  This field is not NULL terminated.
      UTF-8 "Shortest Form" encoding is REQUIRED to guard against the
      technical issues outlined in [UTR36].  The sub-TLV MUST be zero-
      padded so that the sub-TLV is 4-octet aligned.

4.  Update to RFCs

   Section 4 of [RFC5088] states that no new sub-TLVs will be added to
   the PCED TLV, and no new PCE information will be carried in the
   Router Information LSA.  This document updates [RFC5088] by allowing
   the two sub-TLVs defined in this document to be carried in the PCED
   TLV advertised in the Router Information LSA.

   Section 4 of [RFC5089] states that no new sub-TLVs will be added to
   the PCED TLV, and no new PCE information will be carried in the
   Router CAPABLITY TLV.  This document updates [RFC5089] by allowing
   the two sub-TLVs defined in this document to be carried in the PCED
   TLV advertised in the Router CAPABILITY TLV.

   This introduction of additional sub-TLVs should be viewed as an
   exception to the [RFC5088][RFC5089] policy, justified by the
   requirement to discover the PCEP security support prior to

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   establishing a PCEP session.  The restrictions defined in
   [RFC5088][RFC5089] should still be considered to be in place.  If in
   the future new advertisements are required, alternative mechanisms
   such as using [RFC6823] or [I-D.ietf-lsr-ospf-transport-instance]
   should be considered.

   The registry for the PCE Capability Flags assigned in section 8.3 of
   [RFC5557], section 8.1 of [RFC8231], section 6.9 of [RFC8306],
   section 11.1 of [RFC8623], and section 10.5 of [RFC9168] has changed
   to the IGP Parameters "Path Computation Element (PCE) Capability
   Flags" registry created in this document.

5.  Backward Compatibility Considerations

   An LSR that does not support the IGP PCE capability bits specified in
   this document silently ignores those bits.

   An LSR that does not support the KEY-ID and KEY-CHAIN-NAME sub-TLVs
   specified in this document silently ignores these sub-TLVs.

   IGP extensions defined in this document do not introduce any new
   interoperability issues.

6.  Management Considerations

   Manageability considerations for PCE Discovery are addressed in
   Section 4.10 of [RFC4674] and Section 9 of [RFC5088] [RFC5089].

6.1.  Control of Policy and Functions

   A PCE implementation SHOULD allow the following parameters to be
   configured on the PCE:

   *  support for TCP-AO

   *  the KeyID used by TCP-AO

   *  Key Chain Name

   *  support for TLS

6.2.  Information and Data Model

   The YANG model for PCEP [I-D.ietf-pce-pcep-yang] supports PCEP
   security parameters (key, key chain, and TLS).

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6.3.  Liveness Detection and Monitoring

   Normal operations of the IGP meet the requirements for liveness
   detection and monitoring.

6.4.  Verify Correct Operations

   The correlation of PCEP security information advertised against
   information received can be achieved by comparing the information in
   the PCED sub-TLV received by the PCC with that stored at the PCE
   using the PCEP YANG.

6.5.  Requirements on Other Protocols and Functional Components

   There are no new requirements on other protocols.

6.6.  Impact on Network Operations

   Frequent changes in PCEP security information advertised in the PCED
   sub-TLV may have a significant impact on IGP and might destabilize
   the operation of the network by causing the PCCs to reconnect
   sessions with PCE(s).  Section 4.10.4 of [RFC4674] and Section 9.6 of
   [RFC5088] [RFC5089] list techniques that are applicable to this
   document as well.

7.  Security Considerations

   Security considerations as specified by [RFC5088] and [RFC5089] are
   applicable to this document.

   As described in Section 10.2 of [RFC5440], an PCEP speaker MUST
   support TCP MD5 [RFC2385], so no capability advertisement is needed
   to indicate support.  However, as noted in [RFC6952], TCP MD5 has
   been obsoleted by TCP-AO [RFC5925] because of security concerns.
   However, TCP-AO is not widely implemented and so it is, therefore,
   RECOMMENDED (per [RFC8253] which updates [RFC5440]) that PCEP is
   secured using TLS.  An implementation SHOULD offer at least one of
   the two security capabilities defined in this document.

   The information related to PCEP security is sensitive and due care
   needs to be taken by the operator.  This document defines new
   capability bits that are susceptible to a downgrade attack by setting
   them to zero.  The content of Key ID or Key Chain Name Sub-TLV can be
   altered to enable an on-path attack.  Thus, before advertising the
   PCEP security parameters, using the mechanism described in this
   document, the IGP MUST be known to provide authentication and
   integrity for the PCED TLV using the mechanisms defined in [RFC5304],
   [RFC5310] or [RFC5709].

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   Moreover, as stated in the Security Considerations of [RFC5088] and
   [RFC5089], there are no mechanisms defined in OSPF or IS-IS to
   protect the confidentiality of the PCED TLV.  For this reason, the
   operator must ensure that no private data is carried in the TLV, e.g.
   that key-ids or key-chain names do not reveal sensitive information
   about the network.

8.  IANA Considerations

8.1.  PCE Capability Flags

   IANA is requested to move the "Path Computation Element (PCE)
   Capability Flags" registry from the "Open Shortest Path First v2
   (OSPFv2) Parameters" grouping to the "Interior Gateway Protocol (IGP)
   Parameters" grouping.

   IANA is requested to make the following additional assignments from
   the "Path Computation Element (PCE) Capability Flags" registry.

        Bit           Capability Description  Reference
        xx            TCP-AO Support          [This.I.D]
        xx            PCEP over TLS support   [This.I.D]

   The grouping is located at: https://www.iana.org/assignments/igp-
   parameters/igp-parameters.xhtml.

8.2.  PCED sub-TLV Type Indicators

   The PCED sub-TLVs were defined in [RFC5088] and [RFC5089], but they
   did not create a registry for it.  This document requests IANA to
   create a new registry called "PCED sub-TLV type indicators" under the
   "Interior Gateway Protocol (IGP) Parameters" grouping.  The
   registration policy for this registry is "Standards Action"
   [RFC8126].  Values in this registry come from the range 0-65535.

   This registry should be populated with:

        Value         Description             Reference
        0             Reserved                [This.I.D][RFC5088]
        1             PCE-ADDRESS             [This.I.D][RFC5088]
        2             PATH-SCOPE              [This.I.D][RFC5088]
        3             PCE-DOMAIN              [This.I.D][RFC5088]
        4             NEIG-PCE-DOMAIN         [This.I.D][RFC5088]
        5             PCE-CAP-FLAGS           [This.I.D][RFC5088]
        6             KEY-ID                  [This.I.D]
        7             KEY-CHAIN-NAME          [This.I.D]

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   This registry is used by both the OSPF PCED TLV and the IS-IS PCED
   sub-TLV.

   This grouping is located at: https://www.iana.org/assignments/igp-
   parameters/igp-parameters.xhtml.

9.  Acknowledgments

   The authors of this document would also like to thank Acee Lindem,
   Julien Meuric, Les Ginsberg, Ketan Talaulikar, Tom Petch, Aijun Wang,
   Adrian Farrel for the review and comments.

   The authors would also like to special thank Michale Wang for his
   major contributions to the initial version.

   Thanks to John Scudder for providing an excellent AD review.  Thanks
   to Carlos Pignataro, Yaron Sheffer, Ron Bonica, and Will (Shucheng)
   LIU for directorate reviews.

   Thanks to Lars Eggert, Robert Wilton, Roman Danyliw, Eric Vyncke,
   Paul Wouters, Murray Kucherawy, and Warren Kumari for IESG reviews.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5088]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
              Zhang, "OSPF Protocol Extensions for Path Computation
              Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088,
              January 2008, <https://www.rfc-editor.org/info/rfc5088>.

   [RFC5089]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
              Zhang, "IS-IS Protocol Extensions for Path Computation
              Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089,
              January 2008, <https://www.rfc-editor.org/info/rfc5089>.

   [RFC5557]  Lee, Y., Le Roux, JL., King, D., and E. Oki, "Path
              Computation Element Communication Protocol (PCEP)
              Requirements and Protocol Extensions in Support of Global
              Concurrent Optimization", RFC 5557, DOI 10.17487/RFC5557,
              July 2009, <https://www.rfc-editor.org/info/rfc5557>.

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   [RFC5925]  Touch, J., Mankin, A., and R. Bonica, "The TCP
              Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
              June 2010, <https://www.rfc-editor.org/info/rfc5925>.

   [RFC8253]  Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
              "PCEPS: Usage of TLS to Provide a Secure Transport for the
              Path Computation Element Communication Protocol (PCEP)",
              RFC 8253, DOI 10.17487/RFC8253, October 2017,
              <https://www.rfc-editor.org/info/rfc8253>.

   [RFC8177]  Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J.
              Zhang, "YANG Data Model for Key Chains", RFC 8177,
              DOI 10.17487/RFC8177, June 2017,
              <https://www.rfc-editor.org/info/rfc8177>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC7770]  Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
              S. Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
              February 2016, <https://www.rfc-editor.org/info/rfc7770>.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <https://www.rfc-editor.org/info/rfc5304>.

   [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
              and M. Fanto, "IS-IS Generic Cryptographic
              Authentication", RFC 5310, DOI 10.17487/RFC5310, February
              2009, <https://www.rfc-editor.org/info/rfc5310>.

   [RFC5709]  Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
              Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
              Authentication", RFC 5709, DOI 10.17487/RFC5709, October
              2009, <https://www.rfc-editor.org/info/rfc5709>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

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   [RFC8306]  Zhao, Q., Dhody, D., Ed., Palleti, R., and D. King,
              "Extensions to the Path Computation Element Communication
              Protocol (PCEP) for Point-to-Multipoint Traffic
              Engineering Label Switched Paths", RFC 8306,
              DOI 10.17487/RFC8306, November 2017,
              <https://www.rfc-editor.org/info/rfc8306>.

   [RFC8623]  Palle, U., Dhody, D., Tanaka, Y., and V. Beeram, "Stateful
              Path Computation Element (PCE) Protocol Extensions for
              Usage with Point-to-Multipoint TE Label Switched Paths
              (LSPs)", RFC 8623, DOI 10.17487/RFC8623, June 2019,
              <https://www.rfc-editor.org/info/rfc8623>.

   [RFC9168]  Dhody, D., Farrel, A., and Z. Li, "Path Computation
              Element Communication Protocol (PCEP) Extension for Flow
              Specification", RFC 9168, DOI 10.17487/RFC9168, January
              2022, <https://www.rfc-editor.org/info/rfc9168>.

10.2.  Informative References

   [RFC2385]  Heffernan, A., "Protection of BGP Sessions via the TCP MD5
              Signature Option", RFC 2385, DOI 10.17487/RFC2385, August
              1998, <https://www.rfc-editor.org/info/rfc2385>.

   [RFC4674]  Le Roux, J.L., Ed., "Requirements for Path Computation
              Element (PCE) Discovery", RFC 4674, DOI 10.17487/RFC4674,
              October 2006, <https://www.rfc-editor.org/info/rfc4674>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC5926]  Lebovitz, G. and E. Rescorla, "Cryptographic Algorithms
              for the TCP Authentication Option (TCP-AO)", RFC 5926,
              DOI 10.17487/RFC5926, June 2010,
              <https://www.rfc-editor.org/info/rfc5926>.

   [RFC6823]  Ginsberg, L., Previdi, S., and M. Shand, "Advertising
              Generic Information in IS-IS", RFC 6823,
              DOI 10.17487/RFC6823, December 2012,
              <https://www.rfc-editor.org/info/rfc6823>.

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
              <https://www.rfc-editor.org/info/rfc6952>.

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   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [I-D.ietf-pce-pcep-yang]
              Dhody, D., Beeram, V. P., Hardwick, J., and J. Tantsura,
              "A YANG Data Model for Path Computation Element
              Communications Protocol (PCEP)", Work in Progress,
              Internet-Draft, draft-ietf-pce-pcep-yang-19, 11 July 2022,
              <https://www.ietf.org/archive/id/draft-ietf-pce-pcep-yang-
              19.txt>.

   [I-D.ietf-lsr-ospf-transport-instance]
              Lindem, A., Qu, Y., Roy, A., and S. Mirtorabi, "OSPF-GT
              (Generalized Transport)", Work in Progress, Internet-
              Draft, draft-ietf-lsr-ospf-transport-instance-03, 9 July
              2022, <https://www.ietf.org/archive/id/draft-ietf-lsr-
              ospf-transport-instance-03.txt>.

   [UTR36]    Davis, M., "Unicode Technical Report #36, Character
              Encoding Model",
              UTR17 https://www.unicode.org/unicode/reports/tr36/,
              February 2005.

Authors' Addresses

   Diego R. Lopez
   Telefonica I+D
   Spain
   Email: diego.r.lopez@telefonica.com

   Qin Wu
   Huawei Technologies
   101 Software Avenue, Yuhua District
   Nanjing
   Jiangsu, 210012
   China
   Email: bill.wu@huawei.com

   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore 560037
   Karnataka
   India
   Email: dhruv.ietf@gmail.com

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   Qiufang Ma
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing
   Jiangsu, 210012
   China
   Email: maqiufang1@huawei.com

   Daniel King
   Old Dog Consulting
   United Kingdom
   Email: daniel@olddog.co.uk

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