Martin - From: Martin Duke <martin.h.d...@gmail.com> Sent: Tuesday, June 09, 2020 2:35 PM To: Les Ginsberg (ginsberg) <ginsb...@cisco.com> Cc: The IESG <i...@ietf.org>; lsr-cha...@ietf.org; aretana.i...@gmail.com; Acee Lindem (acee) <a...@cisco.com>; draft-ietf-isis-te-...@ietf.org; lsr@ietf.org Subject: Re: [Lsr] Martin Duke's No Objection on draft-ietf-isis-te-app-14: (with COMMENT)
On Tue, Jun 9, 2020 at 12:25 PM Les Ginsberg (ginsberg) <ginsb...@cisco.com<mailto:ginsb...@cisco.com>> wrote: [Les:] The use of "any application" is only possible if the same link attribute values can be used by all applications which are in use in that deployment. This is a decision that can only be made based on the deployment. The discussion of "enablement" is pointing out a possible side effect even if the first set of conditions are met. To my mind, the use of "any application" is likely NOT the default mode of operation even when the preconditions are met - but this is an implementation choice not subject to standardization. I suspect we are talking past each other, probably due to my ignorance of this area, and possibly beyond what a non-blocking comment is worth. Anyway, I can live with not having normative language here, but I would like to have a little more discussion of the considerations for this decision -- at least what the consequences are if nodes don't know if the links support RSVP-TE or not. [Les:] When the application bit mask is populated (non-zero length), the set of applications to which the associated link attributes apply is explicit. When the application bit mask is NOT populated (zero-length), the set of applications to which the associated link attributes apply is implicit. Specifically, any application that is enabled on a node (by application specific configuration which likely is NOT link specific) is allowed to use the attributes. For an application (such as RSVP-TE) where “use” includes the enablement of the application on that link there is a possibility that this is not what was intended. Simply by configuring/advertising a link attribute can then result in unintended use of that link by such an application. Applications which do NOT depend on link attribute advertisements for enablement do not face this issue. They will use the link (or not) based on other criteria which remain application specific. This is what we try to capture (more succinctly) in the sentence: “In the presence of an application where the advertisement of link attribute advertisements is used to infer the enablement of an application on that link (e.g., RSVP-TE), the absence of the application identifier leaves ambiguous whether that application is enabled on such a link.” I don’t know if this helps, but I am trying… 😊 Les
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