[Teas] Benjamin Kaduk's No Objection on draft-ietf-teas-sr-rsvp-coexistence-rec-03: (with COMMENT)

Benjamin Kaduk <kaduk@mit.edu> Wed, 09 May 2018 18:29 UTC

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Date: Wed, 09 May 2018 11:29:35 -0700
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Subject: [Teas] Benjamin Kaduk's No Objection on draft-ietf-teas-sr-rsvp-coexistence-rec-03: (with COMMENT)
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Benjamin Kaduk has entered the following ballot position for
draft-ietf-teas-sr-rsvp-coexistence-rec-03: No Objection

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COMMENT:
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TED/its expansion should be introduced in the Introduction, not the
Abstract, since the Abstract and the rest of the document must be
able to be read in a standalone manner.


In line with Alvaro's comment, I would suggest moving Sections 3.1
through 3.4 into a new parent section "Discarded Options" or
similarly-named.


Section 3.5

   [...] It is RECOMMENDED that the IGP-TE update
   threshold SHOULD be lower in order to flood unreserved bandwidth
   updates often.

Lower than what?


Section 7

It feels odd to say that these "do not require any new security
considerations" and then go and list some new security
considerations.  I would suggest something like "The security
considerations of each protocol are unaffected by the presence of
the other, so only the interactions of the TED consistency solution
with the individual protocols needs to be considered."

I would probably also want to expand the text a bit, noting that:

A hijacked SR traffic stream could potentially cause disruption to
RSVP-TE LSPs in two ways: directly, but consuming sufficient
bandwidth to cause traffic loss, and indirectly, by consuming
sufficient traffic to result in the TED consistency solution
proposed in this document reducing the bandwidth available to
RSVP-TE paths.  The former is possible whenever RSVP-TE and SR
traffic share links, independently of whether this specification is
in use; the latter is new behavior with this specifciation but is
seen as preferrable to the alternative, since the impact to RSVP-TE
traffic can be controlled and paths re-routed.  However, some latent
risk of disruption remains because this specification is a reactive
protcol, relying on taking measurements and only adopting to new
traffic flows after the measurement period.  The finite duration of
the measurement window leaves open a period of potential disruption
before remediation can be applied.


Appendix A

This guidance seems like it could be (very) roughly characterized as
"these are the ranges of values that are not insane to use".  Is it
possible to give more precise/active guidance, such as (taking a
wild guess) "Values between 0.9 and 1.1 allow for taking accunt of
estimated future traffic growth during the current measurement
period while reducing the risk of leaving large amounts of bandwidth
underutilized.  The measurement period should be smaller than a
minute in order for this tight of a growth window to make sense."