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RFC 8920, "OSPF Application-Specific Link Attributes", October 2020

Source of RFC: lsr (rtg)

Errata ID: 6631
Status: Reported
Type: Technical
Publication Format(s) : TEXT

Reported By: Les Ginsberg
Date Reported: 2021-07-05

Section 5 says:

OLD

If link attributes are advertised with zero-length Application
Identifier Bit Masks for both standard applications and user-defined
applications, then any standard application and/or any user-defined
application is permitted to use that set of link attributes. If
support for a new application is introduced on any node in a network
in the presence of such advertisements, these advertisements are
permitted to be used by the new application. If this is not what is
intended, then existing advertisements MUST be readvertised with an
explicit set of applications specified before a new application is
introduced.

An application-specific advertisement (Application Identifier Bit Mask
with a matching Application Identifier Bit set) for an attribute MUST
always be preferred over the advertisement of the same attribute with
the zero-length Application Identifier Bit Masks for both standard
applications and user-defined applications on the same link.

It should say:

NEW

Link attributes MAY be advertised associated with zero-length
Application Identifier Bit Masks for both standard applications
and user-defined applications. Such link attribute advertisements
MUST be used by standard applications and/or user defined applications
when no link attribute advertisements with a non-zero-length
Application Identifier Bit Mask and a matching Application Identifier
Bit set are present for a given link. Otherwise, such link attribute
advertisements MUST NOT be used.

Notes:

RFC 8920 defines advertising link attributes with zero
length Standard Application Bit Mask (SABM) and zero length User
Defined ApplicationBit Mask (UDABM) as a means of advertising link
attributes that can be used by any application. However, the text uses
the word "permitted", suggesting that the use of such advertisements
is "optional". Such an interpretation could lead to interoperability
issues and is not what was intended.

The replacement text below makes explicit the specific conditions when
such advertisements MUST be used and the specific conditions under
which they MUST NOT be used.

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