Re: [trill] RtgDir review of draft-ietf-trill-directory-assist-mechanisms-07.txt

Alia Atlas <> Thu, 14 April 2016 01:35 UTC

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Date: Wed, 13 Apr 2016 21:35:18 -0400
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From: Alia Atlas <>
To: Susan Hares <>
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Subject: Re: [trill] RtgDir review of draft-ietf-trill-directory-assist-mechanisms-07.txt
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Thank you very much for your review!


On Wed, Apr 13, 2016 at 6:53 PM, Susan Hares <> wrote:

> Joel:
> Thank you for the review of this document.  As co-chair, I will work with
> the authors to try to address this issue.
> Sue
> -----Original Message-----
> From: Joel M. Halpern []
> Sent: Wednesday, April 13, 2016 4:47 PM
> To:
> Cc:;
> Subject: RtgDir review of
> draft-ietf-trill-directory-assist-mechanisms-07.txt
> Hello,
> I have been selected as the Routing Directorate reviewer for this draft.
> The Routing Directorate seeks to review all routing or routing-related
> drafts as they pass through IETF last call and IESG review, and sometimes
> on special request. The purpose of the review is to provide assistance to
> the Routing ADs. For more information about the Routing Directorate, please
> see ​
> Although these comments are primarily for the use of the Routing ADs, it
> would be helpful if you could consider them along with any other IETF Last
> Call comments that you receive, and strive to resolve them through
> discussion or by updating the draft.
> Document: draft-ietf-trill-directory-assist-mechanisms-07.txt
> Reviewer: Joel Halpern
> Review Date: 13-April-2016
> IETF LC End Date: N/A
> Intended Status: Proposed Standard
> Summary: I have significant concerns about this document and recommend
> that the Routing ADs discuss these issues further with the authors.
>      I do believe that the major issues are easily resolvable.  I have
> tried to provide my best guess as to text how to resolve each of them.
>      I would like to see the minor issues discussed and preferably
> addressed.
> Major Issues:
>      In the state machine transitions in section 2.3.3 for push servers,
> it appears that if the event indicating that the server is being shut down
> occurs while the server is already Going Stand-By or Uncompleting, the
> transitions indicate that this "going down" event will be lost.  A strict
> reading of this would seem to mean that the "go Down" event would need to
> recur after the timeout condition.  This would seem to be best addressed by
> a new state "Going-Down" whose timeout behavior is to move to down state.
> In section 2.3.2, The descriptions for event 3 and 5 are identical.  I
> believe from the state transitions that condition 3 is supposed to reflect
> the server NOT having complete data when the Activate condition is met.
> In section 3.2.1 there is provision for using a received frame as a
> Query.  There are type indications as to what the type of the frame is.
>   I believe that the intent is that the query always contains the full
> received Ethernet Frame, no matter what the type is.  But it does not say
> that.  So one could also conclude that for ARP, what I should send is the
> ARP message, and for ND, the ND message, etc.  I believe the text needs to
> be clarified.  If my guess is correct that the full Ethernet Frame is to be
> send in all cases, then explanatory text as to why the various type codes
> exist would seem helpful, since the received frame contains enough
> information to support decoding.
> Minor Issues:
>      In section 2.3.3 describing the state transitions for push servers,
> there is an event (event 1) described as "the server was Down but is now
> Up."  The state transition diagram describes this as being a valid event
> that does not change the servers state if the server is in any state other
> than "Down." In one sense, this is reasonable, saying that such an event is
> harmless.  I would however expect some sort of logging or administrative
> notification, as something in the system is quite confused.
>      Should section 2.4 include a note that indicates that reliance on
> information completeness does mean that there are windows when new entities
> join the space represented by particular TRILL data label during which
> packets for that destination may be dropped, due to clients not yet having
> received the updated information?  I believe this window is small, and it
> is quite reasonable to also note that in such text.
>      Text in section on lifetimes and the information maintenance
> in section 3.3 imply that the clients and servers must maintain a
> connection.  Presumably, this is required already by the RBRidge Channel
> protocol, and I understand that we should not repeat the entire protocol
> here.  It would seem to make readers life MUCH simpler if the text noted
> that the RBRidge Channel protocol requires that there be a maintained
> connection between the client and the server, and that these mechanisms
> leverage the presence of that connection.
>      In section on Pull directory forwarding, I expect to see text
> about and to whom the Pull server will flood the received request.
>   Instead, the text appears to say that it is teh response that will be
> flooded.  More importantly, the descriptive text talks about sending the
> response, which would normally be a description of sending the response to
> the requestor, not sending it to someone else.
>      In a related confusion, it seems very strange that a "flood"
> request will result in sending an underlying paket unicast to the
> destination.  This may be just terminology, but it seems likely to confuse
> implementors.  Maybe the flag should be called the Forward flag, with a
> note in the definition that it nromally causes the response to be sent to
> multiple parties, but in the case of a raw MAC frame, results in the packet
> being forwarded to the destination or flooded, as the server can manage?
>      In the description in section 3.3 of Cache management, in the text on
> method one in which the servers keep minimal state, it would seem that a
> large health warning is needed, as this method will cause all clients to
> discard all positive data whenever any positive data at the server changes
> (even if no client is using the modified data.)  This makes a flapping end
> station an attack on the cache of all clients!
>      It strikes me that the working group could help get robust deployment
> by making method 3 (tracking what you told clients) a SHOULD.
>   (I grant that it is not a MUST, as the other choices do work.)
> Editorial Issues / Nits :