[mpls] Alexey Melnikov's Discuss on draft-ietf-mpls-rfc3107bis-02: (with DISCUSS and COMMENT)

Alexey Melnikov <aamelnikov@fastmail.fm> Tue, 01 August 2017 15:22 UTC

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Subject: [mpls] Alexey Melnikov's Discuss on draft-ietf-mpls-rfc3107bis-02: (with DISCUSS and COMMENT)
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Alexey Melnikov has entered the following ballot position for
draft-ietf-mpls-rfc3107bis-02: Discuss

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I would like to discuss one issue before recommending approval of this document:

In Section 2.1:

   The value field of the Multiple Labels Capability (shown in Figure 1)
   consists of one or more triples, where each triple consists of four
   octets.  The first two octets of a triple specify an AFI value, the
   third octet specifies a SAFI value, and the fourth specifies a Count.
   If one of the triples is <AFI,SAFI,Count>, the Count is the maximum
   number of labels that the BGP speaker sending the Capability can
   process in a received UPDATE of the specified AFI/SAFI.

I think lack of recommendations on the minimal supported Count value will
result in lack of interoperability. What are the common Count values used by


In Section 2.3:

      0                   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
     |    Length     |
     |                 Label                 |Rsrv |S~
     ~                 Label                 |Rsrv |S|
     |                          Prefix                               ~
     ~                                                               |

                    Figure 3: NLRI With Multiple Labels

   - Length:

      The Length field consists of a single octet.  It specifies the
      length in bits of the remainder of the NLRI field.

I would like to double check that my math is correct. With SAFI=128 and AFI=2,
assuming the prefix length of 192 bits, this will leave space for:

 (255-192)/24 = 2.625. So this configuration only allows for 2 labels to be included, right?