[rbridge] WG LC draft-ietf-trill-prob-04.txt

[Dinesh G Dutt]

Here are my initial set of comments, some editorial and some not. I'll 
try and send more tomorrow.

    * Abstract: I disagree with the choice of the word "custom routing
      protocols". Spanning tree is as much a custom protocol as IS-IS or
      OSPF or BGP. I'd be OK with something along the lines of "Current
      Ethernet link layers use variants of the spanning tree protocol
      that have ...."
    * Abstract: I also don't think people use the word "routing
      protocols" when referring to Ethernet control protocols. "Bridging
      protocols" maybe appropriate.
    * Section 2: It was not 802.1Q that originally allowed multiple
      spanning tree protocol (MSTP), but 802.1s, and was merged into
      802.1Q only in 2003.
    * Section 2: What does it mean to say "STP is affected even by small
      changes". So does any routing protocol. The fact that it is a tree
      makes for some interesting failure scenarios. But the statement as
      it is worded is vague and potentially inaccurate.
    * Section 2.2: I disagree with the statement "Multipathing would
      typically result in only a small improvement in capacity for a
      network with roughly equal traffic between all pairs of nodes."
      Compared to STP, the effect is dramatic. This is THE main
      motivator for TRILL in the industry. Please reword the paragraph.
    * Section 2.3, last paragraph: I don't believe it is STP that
      specifies that the bridge ports are forwarding by default. It is a
      property of the p-n-p nature of the bridge. We've shipped products
      that have the ports blocked by default.
    * Section 3.1, first para: I'd make it a mandatory requirement to
      retain the native properties of Ethernet, unicast, multicast and
      broadcast, not merely a "useful to have".
    * Section 3.4, first para: There is an erroneous text "Error !
      Reference not found"

Dinesh
Donald Eastlake wrote:
> Hi,
>
> This message initiates a two week TRILL Working Group Last Call on the 
> draft below.
>
> Thanks,
> Donald and Erik
>
> 2008/6/27 <Internet-Drafts at ietf.org <mailto:Internet-Drafts at ietf.org>>:
>
>     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 Working Group of the IETF.
>
>
>            Title           : Transparent Interconnection of Lots of
>     Links (TRILL): Problem and Applicability Statement
>            Author(s)       : J. Touch, R. Perlman
>            Filename        : draft-ietf-trill-prob-04.txt
>            Pages           : 18
>            Date            : 2008-06-27
>
>     Current Ethernet (802.1) link layers use custom routing protocols
>     that have a number of challenges. These routing protocols need to
>     strictly avoid loops, even temporary loops during route propagation,
>
>
>      because of the lack of header loop detection support. Routing tends
>     not to take full advantage of alternate paths, or even non-
>     overlapping pairwise paths (in the case of spanning trees). The
>     convergence of these routing protocols and stability under link
>     changes and failures is also of concern. This document addresses
>     these concerns and suggests that they are related to the need to be
>     able to apply modern network layer routing protocols at the link
>     layer. This document assumes that solutions would not address issues
>     of scalability beyond that of existing bridged (802.1) links, but
>     that a solution would be backward compatible with 802.1, including
>     hubs, bridges, and their existing plug-and-play capabilities.
>
>     This document is a work in progress; we invite you to participate on
>     the mailing list at http://www.postel.org/rbridge
>
>     A URL for this Internet-Draft is:
>     http://www.ietf.org/internet-drafts/draft-ietf-trill-prob-04.txt
>
>     Internet-Drafts are also available by anonymous FTP at:
>     ftp://ftp.ietf.org/internet-drafts/
>
>     Below is the data which will enable a MIME compliant mail reader
>     implementation to automatically retrieve the ASCII version of the
>     Internet-Draft.
>
>
> =============================
> Donald E. Eastlake 3rd
> 155 Beaver Street
> Milford, MA 01757 USA
> d3e3e3 at gmail.com <mailto:d3e3e3 at gmail.com>
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