Re: Review of draft-bberry-pppoe-credit (Informational)

James Carlson <[email protected]>
Newsgroups gmane.ietf.pppext
Message-ID <[email protected]>
Mark Townsley writes:
> This is an individual submission document for Informational publication. 
> Without getting into whether PPPoE itself should have been strangled at 
> birth or not, I would like a fair review of this document before 
> advancing it. Please send comments to the authors and this list before 
> August 24.

I suppose I'm a bit curious why the existing RFC 1663 (PPP Reliable
Transmission) and RFC 1989 (PPP Link Quality Monitoring) protocols
weren't already sufficient for the job and, if not sufficient,
couldn't have been built on to solve the problem.  I don't see either
mentioned in the draft as related work.

I don't think I see a point to having flow control implemented here,
as the transport layers already know how to deal with loss by slowing
down.  Perhaps the real solution might be to fix the "limited
buffering" design problem in the affected devices that this draft
mentions rather than imposing a new protocol on the rest of the world.

There seems to be no description of how the "Receive only" flag might
be used.  Doesn't RFC 1661 already assume (and require) a
bidirectional link?  How could a valid and usable PPP link ever be
running over a "receive only" link?

This proposal seems to further degrade the already tortured PPPoE link
MTU.  If tag insertion is allowed with PPPoE Session Stage messages
(something that RFC 2516 didn't allow), then what happens to the link
MTU?  Further, I suspect that section 5 of the draft is misworded.
The magic value 0106 (which fortunately is not a legal PPP Protocol
ID) is used to distinguish the presence of this TLV, and the system
shouldn't just check for LCP.

One other note: I'm not sure what the "Resources" field is doing in
the PADQ message.  The amount of remaining battery power (!) doesn't
appear to have much to do with link quality.

-- 
James Carlson, KISS Network                    <[email protected]>
Sun Microsystems / 1 Network Drive         71.232W   Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757   42.496N   Fax +1 781 442 1677

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