Re: [trill] I-D Action: draft-ietf-trill-directory-assist-mechanisms-08.txt

Donald Eastlake <> Wed, 02 November 2016 14:26 UTC

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From: Donald Eastlake <>
Date: Wed, 2 Nov 2016 10:26:07 -0400
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Subject: Re: [trill] I-D Action: draft-ietf-trill-directory-assist-mechanisms-08.txt
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This -08 version of draft-ietf-trill-directory-assist-mechanisms has
significant technical changes, although the amount of text
changed/added from version -07 is not that large.

There were two major problems in version -07:

(1) The mechanism it had for hosting a Pull Directory on an end
station almost worked but it lacked any concept of monitoring
adjacency between such an end station and the edge RBridge that was
proxying for it to provide its Pull Directory service to the rest of
the campus. In particular, there was no way if, for example, the end
station crashed, that the edge RBridge would promptly learn of this.
If the end station has crashed or is no longer accessible from the
edge RBridge then directory information pulled from the end station
can no longer be updated and might be stale.

(2) Both draft-ietf-trill-directory-assisted-encap and
draft-ietf-trill-smart-endnodes assume that a specialize end station
can access a Pull Directory (perhaps one on a directly connected edge
RBridge or perhaps even one elsewhere in the campus). But, in fact,
there is no way provided in
draft-ietf-trill-directory-assist-mechanisms to do this.

To fix these problems, version -08 has a significant revised Section
3.5 and a new Section 5. (The old Section 5 is now Section 6 and
similarly for previous sections after 5.)

The new Section 5 specifies a "TRILL ES-IS" mechanism to establish and
monitor adjacency between edge RBridges and cooperating end stations
on the same link through a modified version of TRILL IS-IS.

The modified Section 3.5 specifies how to host a Pull Directory on and
end station and how an end station can access an edge RBridge hosted
Pull Directory on the same link. TRILL ES-IS is used to advertise the
availability of such Pull Directories reducing the need for
configuration in line with TRILL's philosophy of zero/minimum
configuration. (Version -07 had no mechanism for an end station hosted
Pull Directory to announce itself.)

This version -08 is believe to also resolve all or most of the
comments from Joel Halpern's Routing Directorate review of this draft
some months ago. I will send a subsequent message to him copied to the

 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 155 Beaver Street, Milford, MA 01757 USA

On Mon, Oct 31, 2016 at 5:11 PM,  <> wrote:
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the Transparent Interconnection of Lots of Links of the IETF.
>         Title           : TRILL: Edge Directory Assist Mechanisms
>         Authors         : Donald Eastlake
>                           Linda Dunbar
>                           Radia Perlman
>                           Yizhou Li
>         Filename        : draft-ietf-trill-directory-assist-mechanisms-08.txt
>         Pages           : 53
>         Date            : 2016-10-31
> Abstract:
>    This document describes mechanisms for providing directory service to
>    TRILL (Transparent Interconnection of Lots of Links) edge switches.
>    The directory information provided can be used in reducing multi-
>    destination traffic, particularly ARP/ND and unknown unicast
>    flooding. It can also be used to detect traffic with forged source
>    addresses.
> The IETF datatracker status page for this draft is:
> There's also a htmlized version available at:
> A diff from the previous version is available at:
> Please note that it may take a couple of minutes from the time of submission
> until the htmlized version and diff are available at
> Internet-Drafts are also available by anonymous FTP at:
> _______________________________________________
> trill mailing list