Subject: [Idr] [Technical Errata Reported] RFC5291 (3468)

From: RFC Errata System <[email-masked]>
Date: Tue, 22 Jan 2013 20:31:09 -0800 (PST)

The following errata report has been submitted for RFC5291,
"Outbound Route Filtering Capability for BGP-4".

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You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=5291&eid=3468

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Type: Technical
Reported by: David Lamparter <[email-masked]>

Section: 5

Original Text
-------------
5. Outbound Route Filtering Capability

   A BGP speaker that is willing to receive ORF entries from its peer,
   or a BGP speaker that would like to send ORF entries to its peer,
   advertises this to the peer by using the Outbound Route Filtering
   Capability, as described below.

   The Outbound Route Filtering Capability is a new BGP Capability
   [BGP-CAP] defined as follows:

      Capability code: 3

      Capability length: variable

      Capability value: one or more of the entries as shown in Figure 3.

         +--------------------------------------------------+
         | Address Family Identifier (2 octets)             |
         +--------------------------------------------------+
         | Reserved (1 octet)                               |
         +--------------------------------------------------+
         | Subsequent Address Family Identifier (1 octet)   |
         +--------------------------------------------------+
         | Number of ORFs (1 octet)                         |
         +--------------------------------------------------+
         | ORF Type (1 octet)                               |
         +--------------------------------------------------+
         | Send/Receive (1 octet)                           |
         +--------------------------------------------------+
         | ...                                              |
         +--------------------------------------------------+
         | ORF Type (1 octet)                               |
         +--------------------------------------------------+
         | Send/Receive (1 octet)                           |
         +--------------------------------------------------+

         Figure 3: Outbound Route Filtering Capability Encoding

Corrected Text
--------------

Notes
-----
RFC5291 does not specify how the ORF capability is supposed to be used
in conjunction with multiple enabled AFI/SAFI combinations.  The text
can be interpreted as either "one capability instance will be sent,
carrying multiple blocks as described in Figure 3" or as "the
capability will be supplied in more than instance".

Note also that RFC3392 [BGP-CAP] Section 4 reads:

   BGP speakers MAY include more than one instance of a capability (as
   identified by the Capability Code) with non-zero Capability Length
   field, but with different Capability Value, and either the same or
   different Capability Length.  Processing of these capability
   instances is specific to the Capability Code and MUST be described in
   the document introducing the new capability.

Latter description of how multiple instances of the capability are to be
processed - albeit relatively obvious - is nowhere to be found in RFC5291.

Respectfully requesting a clarification,

David Lamparter

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RFC5291 (draft-ietf-idr-route-filter-17)
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Title               : Outbound Route Filtering Capability for BGP-4
Publication Date    : August 2008
Author(s)           : E. Chen, Y. Rekhter
Category            : PROPOSED STANDARD
Source              : Inter-Domain Routing
Area                : Routing
Stream              : IETF
Verifying Party     : IESG