I have a few comments on the document.
- Section 1, Bridging Limitations: The first two paragraphs are
structured around the logic: because ethernet header doesn't have a TTL
or a hop count, the only choice was to use spanning tree. IEEE 802.1 has
defined several headers such as 802.1Q header that carries the VLAN. If
they wanted to add a TTL, they could have. They picked spanning tree and
said that therefore they didn't need a TTL. To the extent this
represents history, I think it is inaccurate. To the extent it attempts
to explain the rationale for RBridges, it seems unnecessary. A
sufficient replacement maybe along the lines of: "Spanning Tree Protocol
and its variants are the control protocol deployed in current 802.1D
Ethernet bridges. This protocol constructs a single tree out of a mesh
of network connections. This tree eliminates usage of equal cost
multipaths and results in non-optimal pair-wise forwarding."
- Section 1, Bridging Limitations: More specific comments:
- "Because of the potential for severe impact from looping traffic,
many (if not most) current bridge
implementations stop forwarding of traffic frames following a
topology change event and restart only after STP/RSTP is
complete" is incorrect. All 802.1D bridges allow (R/M)STP to
complete before moving a port to forwarding state. I'd
remove the phrase in parentheses.
- "Inefficient inter-bridge connection usage". What do you mean by
this phrase ?
- Section 1.2, Backward Compatibility and section 4.1: "...they
terminate a bridged spanning tree, (i.e. - they do not forward BPDUs)".
I thought that we have not concluded the discussion on preventing loops
for interconnected Bridges and RBridges based on the email thread that
started a while back. Putting a decision in this section on the solution
seems a little unnecessary. What is proposed in the current solution is
to run a spanning tree protocol instance per port which maybe not
scalable. I think something like "It's strongly desirable to minimize
the interaction between the bridges and Rbridges and constrain a
spanning tree" is more appropriate.
- Ethernet and 802 is used interchangeably. Isn't Ethernet 802.3 only ?
Look at: http://en.wikipedia.org/wiki/IEEE_802.3 or
I don't see anything on what I consider to be another important goal: to
have a single protocol to compute unicast, multicast and broadcast
routes. This reduces operational overhead by having to understand and
debug a single protocol.
The IESG wrote:
The IESG has received a request from the Transparent Interconnection of
Lots of Links WG (trill) to consider the following document:
- 'TRILL Routing Requirements in Support of RBridges '
<draft-ietf-trill-routing-reqs-02.txt> as an Informational RFC
The IESG plans to make a decision in the next few weeks, and solicits
final comments on this action. Please send substantive comments to the
ietf(_at_)ietf(_dot_)org mailing lists by 2007-03-30. Exceptionally,
comments may be sent to iesg(_at_)ietf(_dot_)org instead. In either case, please
retain the beginning of the Subject line to allow automated sorting.
The file can be obtained via
IESG discussion can be tracked via
rbridge mailing list
We make our world significant by the courage of our questions and by
the depth of our answers. - Carl Sagan
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