Subject: Alissa Cooper's Discuss on draft-ietf-rtgwg-enterprise-pa-multihoming-08: (with DISCUSS and COMMENT)

From: Alissa Cooper via Datatracker <[email-masked]>
Date: Wed, 26 Jun 2019 12:43:36 -0700

Alissa Cooper has entered the following ballot position for
draft-ietf-rtgwg-enterprise-pa-multihoming-08: Discuss

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DISCUSS:
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I'd like to discuss the following comments from the Gen-ART reviewer:

"Throughout, but particularly in section 5, this document refers to "hosts"
doing address selection. To be fair, so does RFC 6724, but 6724 is referring to
*default* address selection. In reality, *applications* do address selection on
a host; the host stack will only do address selection if the application
requests a default address. That works well for the scenarios in 6724, but in
this document, for example section 5.2.3, I'm not so sure. The idea that a host
would receive an ICMP destination unreachable and re-arrange its address
selection seems at least an incomplete picture: An application with a (normal,
non-multi-path) TCP connection to a remote application is not able to "try
another source address to reach the destination"; the source address is already
set for that TCP connection, so the only choice is to close the connection
entirely. If the application chooses to re-establish the connection with a
default address, yes, the host stack could then give a new default address back
to the application, but this is hardly the dynamic and quickly adjusting
process that the document seems to be envisioning.

I don't think the above invalidates the core of the document or requires some
grand rewrite. But I do think some clarification is in order, saying that the
mechanisms described help with the *default* address selection, and some short
discussion of the limitations for what applications can (and more importantly
cannot) do with these mechanisms would be useful."

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COMMENT:
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Please respond to the remainder of the Gen-ART review.