[mpls] [Errata Held for Document Update] RFC8029 (8788)

rfc-editor@rfc-editor.org Thu, 16 July 2026 08:33 UTC

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Subject: [mpls] [Errata Held for Document Update] RFC8029 (8788)
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The following errata report has been held for document update for RFC8029,
"Detecting Multiprotocol Label Switched (MPLS) Data-Plane Failures"

--------------------------------------
You may review the report below and at:
https://errata.rfc-editor.org/eid8788/

--------------------------------------

Status: Held for Document Update
Type: Technical
Reported by: Adrian Farrel <adrian@olddog.co.uk>
Date Reported: Feb. 27, 2026, 8 p.m.
Held by: Ketan Talaulikar (IESG)

Throughout the document, when it says:

Original Text
-------------
Section 3.4
   Address Type

      The Address Type indicates if the interface is numbered or
      unnumbered.  It also determines the length of the Downstream IP
      Address and Downstream Interface fields.  The Address Type is set
      to one of the following values:

       Type #        Address Type
       ------        ------------
            1        IPv4 Numbered
            2        IPv4 Unnumbered
            3        IPv6 Numbered
            4        IPv6 Unnumbered

Section 3.4
   Downstream Address and Downstream Interface Address

      IPv4 addresses and interface indices are encoded in 4 octets; IPv6
      addresses are encoded in 16 octets.

      If the interface to the downstream LSR is numbered, then the
      Address Type MUST be set to IPv4 or IPv6, the Downstream Address
      MUST be set to either the downstream LSR's Router ID or the
      interface address of the downstream LSR, and the Downstream
      Interface Address MUST be set to the downstream LSR's interface
      address.

      If the interface to the downstream LSR is unnumbered, the Address
      Type MUST be IPv4 Unnumbered or IPv6 Unnumbered, the Downstream
      Address MUST be the downstream LSR's Router ID, and the Downstream
      Interface Address MUST be set to the index assigned by the
      upstream LSR to the interface.

      If an LSR does not know the IP address of its neighbor, then it
      MUST set the Address Type to either IPv4 Unnumbered or IPv6
      Unnumbered.  For IPv4, it must set the Downstream Address to
      127.0.0.1; for IPv6, the address is set to 0::1.  In both cases,
      the interface index MUST be set to 0.  If an LSR receives an Echo
      Request packet with either of these addresses in the Downstream
      Address field, this indicates that it MUST bypass interface
      verification but continue with label validation.

      If the originator of an echo request packet wishes to obtain
      Downstream Detailed Mapping information but does not know the
      expected label stack, then it SHOULD set the Address Type to
      either IPv4 Unnumbered or IPv6 Unnumbered.  For IPv4, it MUST set
      the Downstream Address to 224.0.0.2; for IPv6, the address MUST be
      set to FF02::2.  In both cases, the interface index MUST be set to
      0.  If an LSR receives an echo request packet with the all-routers
      multicast address, then this indicates that it MUST bypass both
      interface and label stack validation but return Downstream Mapping
      TLVs using the information provided.

Section 3.7
   Address Type

      The Address Type indicates if the interface is numbered or
      unnumbered.  It also determines the length of the IP Address and
      Interface fields.  The resulting total for the initial part of the
      TLV is listed in the table below as "K Octets".  The Address Type
      is set to one of the following values:

         Type #        Address Type           K Octets
         ------        ------------           --------
              0        Reserved                      4
              1        IPv4 Numbered                12
              2        IPv4 Unnumbered              12
              3        IPv6 Numbered                36
              4        IPv6 Unnumbered              24
          5-250        Unassigned
        251-254        Reserved for Experimental Use
            255        Reserved


Section 3.7
   IP Address and Interface

      IPv4 addresses and interface indices are encoded in 4 octets; IPv6
      addresses are encoded in 16 octets.

      If the interface upon which the echo request message was received
      is numbered, then the Address Type MUST be set to IPv4 or IPv6,
      the IP Address MUST be set to either the LSR's Router ID or the
      interface address, and the Interface MUST be set to the interface
      address.

      If the interface is unnumbered, the Address Type MUST be either
      IPv4 Unnumbered or IPv6 Unnumbered, the IP Address MUST be the
      LSR's Router ID, and the Interface MUST be set to the index
      assigned to the interface.

Section 6.2.4
      Type #     Address Type      K Octets    Reference
      ------     ------------      --------    ---------
           1     IPv4 Numbered           16    [RFC8029]
           2     IPv4 Unnumbered         16    [RFC8029]
           3     IPv6 Numbered           40    [RFC8029]
           4     IPv6 Unnumbered         28    [RFC8029]
           5     Non IP                  12    [RFC6426]

             Downstream Detailed Mapping Address Type Registry

Section 6.2.8
    Value      Meaning                                  Reference
    ---------- ---------------------------------------- ---------
          0    Reserved                                 [RFC8029]
          1    IPv4 Numbered                            [RFC8029]
          2    IPv4 Unnumbered                          [RFC8029]
          3    IPv6 Numbered                            [RFC8029]
          4    IPv6 Unnumbered                          [RFC8029]
      5-250    Unassigned
    251-254    Experimental Use                         [RFC8029]
        255    Reserved                                 [RFC8029]

Section A.2
   Address Type

      The Address Type indicates if the interface is numbered or
      unnumbered.  It also determines the length of the Downstream IP
      Address and Downstream Interface fields.  The resulting total for
      the initial part of the TLV is listed in the table below as "K
      Octets".  The Address Type is set to one of the following values:

       Type #        Address Type           K Octets
       ------        ------------           --------
            1        IPv4 Numbered                16
            2        IPv4 Unnumbered              16
            3        IPv6 Numbered                40
            4        IPv6 Unnumbered              28
            5        Non IP                       12

Section A.2
   Downstream IP Address and Downstream Interface Address

      IPv4 addresses and interface indices are encoded in 4 octets; IPv6
      addresses are encoded in 16 octets.

      If the interface to the downstream LSR is numbered, then the
      Address Type MUST be set to IPv4 or IPv6, the Downstream IP
      Address MUST be set to either the downstream LSR's Router ID or
      the interface address of the downstream LSR, and the Downstream
      Interface Address MUST be set to the downstream LSR's interface
      address.

      If the interface to the downstream LSR is unnumbered, the Address
      Type MUST be IPv4 Unnumbered or IPv6 Unnumbered, the Downstream IP
      Address MUST be the downstream LSR's Router ID, and the Downstream
      Interface Address MUST be set to the index assigned by the
      upstream LSR to the interface.

      If an LSR does not know the IP address of its neighbor, then it
      MUST set the Address Type to either IPv4 Unnumbered or IPv6
      Unnumbered.  For IPv4, it must set the Downstream IP Address to
      127.0.0.1; for IPv6, the address is set to 0::1.  In both cases,
      the interface index MUST be set to 0.  If an LSR receives an Echo
      Request packet with either of these addresses in the Downstream IP
      Address field, this indicates that it MUST bypass interface
      verification but continue with label validation.

      If the originator of an echo request packet wishes to obtain
      Downstream Mapping information but does not know the expected
      label stack, then it SHOULD set the Address Type to either IPv4
      Unnumbered or IPv6 Unnumbered.  For IPv4, it MUST set the
      Downstream IP Address to 224.0.0.2; for IPv6, the address MUST be
      set to FF02::2.  In both cases, the interface index MUST be set to
      0.  If an LSR receives an echo request packet with the all-routers
      multicast address, then this indicates that it MUST bypass both
      interface and label stack validation, but return Downstream
      Mapping TLVs using the information provided.

Corrected Text
--------------
Section 3.4
   Address Type

      The Address Type indicates if the interface is numbered or
      unnumbered.  It also determines the length of the Downstream IP
      Address and Downstream Interface fields.  The Address Type is set
      to one of the following values:

       Type #        Address Type
       ------        ------------
            1        IPv4 Numbered
            2        IPv4 Unnumbered
            3        IPv6 Numbered (with GUA or ULA)
            4        IPv6 Link-Local-only

Section 3.4
   Downstream Address and Downstream Interface Address

      IPv4 addresses and interface indices are encoded in 4 octets; IPv6
      addresses are encoded in 16 octets.

      If the interface to the downstream LSR is numbered, then the
      Address Type MUST be set to IPv4 or IPv6, the Downstream Address
      MUST be set to either the downstream LSR's Router ID or the
      interface address of the downstream LSR, and the Downstream
      Interface Address MUST be set to the downstream LSR's interface
      address.

      If the interface to the downstream LSR is IPv4 unnumbered or 
      only with IPv6 Link-Local address, the Downstream Address 
      MUST be the downstream LSR's Router ID, and the Downstream
      Interface Address MUST be set to the index assigned by the
      upstream LSR to the interface.

      If an LSR does not know the IP address of its neighbor, then it
      MUST set the Address Type to either IPv4 Unnumbered or IPv6
      Link-Local-Only.  For IPv4, it must set the Downstream Address to
      127.0.0.1; for IPv6, the address is set to 0::1.  In both cases,
      the interface index MUST be set to 0.  If an LSR receives an Echo
      Request packet with either of these addresses in the Downstream
      Address field, this indicates that it MUST bypass interface
      verification but continue with label validation.

      If the originator of an echo request packet wishes to obtain
      Downstream Detailed Mapping information but does not know the
      expected label stack, then it SHOULD set the Address Type to
      either IPv4 Unnumbered or IPv6 Link-Local-Only.  For IPv4, it MUST set
      the Downstream Address to 224.0.0.2; for IPv6, the address MUST be
      set to FF02::2.  In both cases, the interface index MUST be set to
      0.  If an LSR receives an echo request packet with the all-routers
      multicast address, then this indicates that it MUST bypass both
      interface and label stack validation but return Downstream Mapping
      TLVs using the information provided.

Section 3.7
   Address Type

      The Address Type indicates if the interface is numbered or
      unnumbered.  It also determines the length of the IP Address and
      Interface fields.  The resulting total for the initial part of the
      TLV is listed in the table below as "K Octets".  The Address Type
      is set to one of the following values:

         Type #        Address Type           K Octets
         ------        ------------           --------
              0        Reserved                      4
              1        IPv4 Numbered                12
              2        IPv4 Unnumbered              12
              3        IPv6 Numbered (with GUA or ULA)  36
              4        IPv6 Link-Local-only              24
          5-250        Unassigned
        251-254        Reserved for Experimental Use
            255        Reserved


Section 3.7
   IP Address and Interface

      IPv4 addresses and interface indices are encoded in 4 octets; IPv6
      addresses are encoded in 16 octets.

      If the interface upon which the echo request message was received
      is numbered, then the Address Type MUST be set to IPv4 or IPv6,
      the IP Address MUST be set to either the LSR's Router ID or the
      interface address, and the Interface MUST be set to the interface
      address.

      If the interface is IPv4 unnumbered or only with IPv6 Link-Local
      address, the IP Address MUST be the LSR's Router ID, and the 
      Interface MUST be set to the index  assigned to the interface.

Section 6.2.4
      Type #     Address Type      K Octets    Reference
      ------     ------------      --------    ---------
           1     IPv4 Numbered           16    [RFC8029]
           2     IPv4 Unnumbered         16    [RFC8029]
           3     IPv6 Numbered (with GUA or ULA)    40    [RFC8029]
           4     IPv6 Link-Local-only        28    [RFC8029]
           5     Non IP                  12    [RFC6426]

             Downstream Detailed Mapping Address Type Registry

Section 6.2.8
    Value      Meaning                                  Reference
    ---------- ---------------------------------------- ---------
          0    Reserved                                 [RFC8029]
          1    IPv4 Numbered                            [RFC8029]
          2    IPv4 Unnumbered                          [RFC8029]
          3    IPv6 Numbered (with GUA or ULA)  [RFC8029]
          4    IPv6 Link-Local-only                          [RFC8029]
      5-250    Unassigned
    251-254    Experimental Use                         [RFC8029]
        255    Reserved                                 [RFC8029]

Section A.2
   Address Type

      The Address Type indicates if the interface is numbered or
      unnumbered.  It also determines the length of the Downstream IP
      Address and Downstream Interface fields.  The resulting total for
      the initial part of the TLV is listed in the table below as "K
      Octets".  The Address Type is set to one of the following values:

       Type #        Address Type           K Octets
       ------        ------------           --------
            1        IPv4 Numbered                16
            2        IPv4 Unnumbered              16
            3        IPv6 Numbered (with GUA or ULA)   40
            4        IPv6 Link-Local-only            28
            5        Non IP                       12

Section A.2
   Downstream IP Address and Downstream Interface Address

      IPv4 addresses and interface indices are encoded in 4 octets; IPv6
      addresses are encoded in 16 octets.

      If the interface to the downstream LSR is numbered, then the
      Address Type MUST be set to IPv4 or IPv6, the Downstream IP
      Address MUST be set to either the downstream LSR's Router ID or
      the interface address of the downstream LSR, and the Downstream
      Interface Address MUST be set to the downstream LSR's interface
      address.

      If the interface to the downstream LSR is IPv4 unnumbered or only with
      IPv6 Link-Local address, the Downstream Address MUST be the downstream
      LSR's Router ID, and the Downstream Interface Address MUST be set to the 
      index assigned by the  upstream LSR to the interface.

      If an LSR does not know the IP address of its neighbor, then it
      MUST set the Address Type to either IPv4 Unnumbered or IPv6
      Link-Local-Only.  For IPv4, it must set the Downstream Address to
      127.0.0.1; for IPv6, the address is set to 0::1.  In both cases,
      the interface index MUST be set to 0.  If an LSR receives an Echo
      Request packet with either of these addresses in the Downstream
      Address field, this indicates that it MUST bypass interface
      verification but continue with label validation.

      If the originator of an echo request packet wishes to obtain
      Downstream Detailed Mapping information but does not know the
      expected label stack, then it SHOULD set the Address Type to
      either IPv4 Unnumbered or IPv6 Link-Local-Only.  For IPv4, it MUST set
      the Downstream Address to 224.0.0.2; for IPv6, the address MUST be
      set to FF02::2.  In both cases, the interface index MUST be set to
      0.  If an LSR receives an echo request packet with the all-routers
      multicast address, then this indicates that it MUST bypass both
      interface and label stack validation but return Downstream Mapping
      TLVs using the information provided.

Notes
-----
There is no such thing as an "IPv6 unnumbered interface".
Various updates were discussed with participants on the MPLS and 6MAN WG mailing lists. The proposed text is where the discussion concluded.

Pointers to some of the discussion threads:
https://mailarchive.ietf.org/arch/msg/mpls/Cvop4My8RBsrrl7cWshb5YF_coo/
https://mailarchive.ietf.org/arch/msg/mpls/KFIQdqaty4sde5KBzkGR4eRFIS0/
https://mailarchive.ietf.org/arch/msg/ipv6/xd_E_LlYNm9D8CW0iXX8T1ubQUY/

Obviously (?) this report can only be "Held for Document Update" and it is for the WG to decide on any changes/improvements when this RFC gets updated.

--------------------------------------
RFC8029 (draft-ietf-mpls-rfc4379bis)
--------------------------------------
Title               : Detecting Multiprotocol Label Switched (MPLS) Data-Plane Failures
Publication Date    : March 2017
Author(s)           : K. Kompella, G. Swallow, C. Pignataro, Ed., N. Kumar, S. Aldrin, M. Chen
Category            : Proposed Standard
Source              : mpls (rtg)
Stream              : IETF